HomeMy WebLinkAboutDrainage Report May 7, 2015
Gessner Engineering Job No. 11-0355
Prepared for:
Moreau Family Investments, Ltd.
Mr. Chuck Moreau
In Accordance with:
Unified Storm water Design Guidelines
City of Bryan/City of College Station
Prepared by:
GESSNER ENGINEERING, LLC
College Station, Texas
DRAINAGE DESIGN REPORT
Brazos Valley Floor and Design
College Station, Texas
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May 7, 2015
Mr. Alan Gibbs, P.E.
City Engineer
City of College Station
1101 Texas Avenue
College Station,TX 77840
Re: Storm Water Drainage Study
Brazos Valley Floor and Design
12900 Old Wellborn Road
College Station,Texas
Gessner Engineering Job No.: 11-0355
Dear Mr. Gibbs,
This report conveys the results of the storm water drainage study conducted by Gessner
Engineering for the proposed redevelopment of Brazos Valley Floor and Design, College Station,
Texas. Gessner Engineering believes that all information contained in this report is valid. Please
contact us if you have any questions or if we can be of further assistance.
This report for the drainage design for Brazos Valley Floor and Design was
prepared by Gessner Engineering in accordance with provisions of the
Bryan/College Station Unified Stormwater Design Guidelines for the owner of the
property.
Sincerely,
GESSNER ENGINEERING LLC, F-7451 .. 1.
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Melissa P. Thomas, P.E. t 0''•t ENi
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TABLE OF CONTENTS
EXECUTIVE SUMMARY 4
INTRODUCTION 4
CALCULATIONS 5
Time of Concentration 5
Unit Hydrograph 6
Reach Routing 6
Peak Runoff Flow 6
Peak Post-Developed Runoff Flow 7
CONCLUSION 7
APPENDIX
Appendix A:General Location Map
Appendix B: FEMA 100 Year Floodplain Map
Appendix C: Drainage Area Map and Calculations
Appendix D: Hydrographs
Appendix E: HEC-HMS Calculations
Appendix F: Driveway Culvert Calculations
Appendix G: Technical Design Summary
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EXECUTIVE SUMMARY
This storm water drainage report is submitted to the City of College Station, Texas for review on
April 2, 2014 by Melissa P. Thomas, P.E. of Gessner Engineering, located at 2501 Ashford Drive,
Suite 102, College Station, Texas 77840.
The proposed project consists of the demolition of the asphalt pavement serving the current
building and construction of a 15,000 square foot (SF) warehouse and associated new concrete
parking. The site will be served by two detention ponds in series. The total area of construction is
approximately 2.38 acres. The subject site currently contains a 2,434 SF retail building to remain, a
1,963 sf metal canopy, a 1,112 sf metal awning, and a 24,631 SF of existing parking lot and
hardscape all to be removed.
The site is located directly northwest of the intersection of Old Wellborn Road and N. Graham
Road. The site is located in the Hopes Creek watershed. The site is not located in the FEMA 100
year flood plain, as shown by FIRM number 48041C0310E. This firmette is included as Appendix B.
Runoff from the overall drainage area generally flows south until reaching N. Graham Road. Water
then flows southwest through a small drainage ditch along N. Graham Road until reaching a
tributary of Hopes Creek. Runoff from the subject site reaches N. Graham Road by sheet flow and
shallow concentrated flow through a small channel in the center of the property. Runoff from the
Carpet Outlet site is stored in a detention pond in the southern corner of the property and
discharged to flow across the property to the southwest of both lots until reaching N. Graham
Road. Under existing conditions, the total flow exiting the lot and reaching the drainage ditch on N.
Graham Road is 16.3 cubic feet per second (cfs) at the peak of the 100 year, Type III, 24 hour storm
event. After development, runoff will be stored in a series of two detention ponds on the subject
property and discharged at the southern corner of the property directly into the ditch along N.
Graham Road. Under proposed conditions the flow into the drainage ditch is 15.7 cfs, at the same
storm event. Additionally, a small portion of the two driveways along the north property line
discharges 0.2 cfs onto the existing Brazos Valley Floor and Design site at the same storm event.
The total peak flow of the subject tract under the proposed conditions is 15.9 cfs.
The post-developed peak flow is below the pre-developed peak at the 100 year storm event and
does not create any issues for downstream properties.
INTRODUCTION
This storm water drainage report is intended to determine the required detention to match pre-
developed storm runoff conditions for the proposed Brazos Valley Floor and Design. The entire
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drainage area contributes to the drainage ditch along N. Graham Road. The point of contribution
to the ditch was used for both pre-developed and post-developed conditions analysis.
Drainage Calculations for this site were prepared according to the National Resource Conservation
Method as detailed in Technical Release 55 (TR-55) published in June of 1986. Proposed
improvements include a 15,000 SF building and 50,130 SF concrete pavement and approximately
8,140 SF of detention area. Curve numbers from TR-55 were used based on developed uses as
described above. Pre-developed flows were calculated based on the existing development for the
• subject site and based on undeveloped conditions for the Carpet Outlet tract. The calculated pre-
• developed and developed flows include the two (2), five (5), ten (10), twenty-five (25), fifty (50) and
one-hundred (100) year storms in accordance with the Bryan/College Station Unified Stormwater
• Design Guidelines.
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CALCULATIONS
Calculations were performed according to the USDA TR-55 and with the aid of HEC-HMS 3.5 by the
10 U.S. Army Corps of Engineers. The output data from HEC-HMS has been provided as Appendix E.
Time of Concentration
The time of concentration (travel time) for each drainage area was estimated by summing the flow
time for each segment of travel. For sheet flow, travel time was estimated by Manning's Kinematic
equation:
0.007 x(nL)o�
t _ �r 0.4 J
�J 2
Where:
tt = travel time (hours)
n = manning's roughness coefficient
L = flow length (feet)
S = slope (ft/ft)
P2 = 2-year, 24 hour rainfall (inches)
For shallow concentrated flow, the travel time was calculated from the flow velocity based on the
slope in the direction of flow. These velocities were taken from Table C-4 of the Bryan College
Station Unified Stormwater Design Guidelines.
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The computed times of concentration for each drainage area are included in Appendix E.
Computed values were increased to a minimum time of six (6) minutes as required, based on
Chapter 3 of TR-55 which limits the minimum Time of Concentration to 0.1 hour or six (6) minutes.
Unit Hydrograph
A generic unit hydrograph was computed by distributing the rainfall depths (Table 1) according to
the distribution factors for the NCRS Type III 24 hour storm. This hydrograph was then applied to
each subarea based on the curve number and time of concentration of that area.
Reach Routing
Hydrographs were routed from subareas to the outflow through the kinematic wave method. This
method allows for hydrographs to be translating with time, but not attenuating. The effects of
backwater flow and pressure flow in channels were neglected.
Peak Runoff Flow
Peak Runoff Flow from the site was determined based on the Type Ill 24 hour storm applied to
each drainage area. The depth-duration-intervals for each frequency are included in Table 1 below,
and were obtained from Table C-6 in the Unified Stormwater Design Guidelines. Curve Number
values (CN) were determined from Table C-7, Appendix C of the Unified Stormwater Design
Guidelines. Peak pre-developed flows for the subject site adjacent to N. Graham Road are included
in Table 1. Drainage areas and calculations are included on sheet C5.0 and C5.1, which are
attached in Appendix C.
Rainfall Depth(in),24-hr Pre-Developed Peak Flow
Frequency duration (cfs)
2 year 4.50 5.6
10 year 7.40 10.4
25 year 8.40 12.5
50 year 9.80 14.1
100 year 11.00 16.3
Table 1:Rainfall Depths and Resulting Flows
Peak Post-Developed Runoff Flow
The post-developed peak flows compared to the pre-developed peak flows are shown in Table 2
below for each storm event. Hydrographs for each storm event are included as Appendix D.
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Pre-Developed Post-Developed Post-Developed Total Post-
Storm Peak Flow at Peak Flow at Peak Flow at Developed Flow
Event Southwest Outlet Southwest Outlet North Outlet (cfs)
(cfs) (cfs) (cfs)
2 year 5.6 5.4 0.1 5.5
10 year 10.4 9.5 0.1 9.6
25 year 12.5 11.3 0.1 11.4
50 year 14.1 12.8 0.2 13.0
100 year 16.3 14.7 0.2 14.9
Table 2:Pre-Developed and Post-Developed Site Outflows
CONCLUSION
Based on visual evidence, engineering drainage calculations and sound engineering judgment,
Gessner Engineering believes that the post-development flows are reduced for the two (2), ten
(10), twenty-five (25), fifty (50), and one hundred (100) year design storms for this development,
and do not create adverse impacts to downstream properties.
Work Certification
"This report for the drainage design of the Brazos Valley Floor & Design was prepared by me in
accordance with the provisions of the Bryan/College Station Unified Drainage Guidelines for the
owners of the property. All licenses and permits required by any and all state and federal
regulatory agencies for the proposed drainage improvements have been issued."
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M6eL18SA , , State of Texas No. 98398
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APPENDIX A:
General Location Map
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• APPENDIX B:
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• Hydrographs
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Subbasin"PRE-AREA 1"Results for Run"PRE-2 YEAR"
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Run:PRE-2 YEAR Element:PRE-AREA 1 Result:Precipitation Run:PRE-2 YEAR Element:PRE-AREA 1 Resul:Precip Cation Loss
Run:PRE-2 YEAR Element:PRE-AREA 1 Result:Outflow ——– Run:PRE-2 YEAR Element:PRE-AREA 1 Result:Baseflow
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Subbasin"PRE-AREA 1"Results for Run"PRE- 10 YEAR"
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Run:PRE-10 YEAR Element:PRE-AREA 1 Result Outflow ——— Run:PRE-10 YEAR Element PRE-AREA 1 Result Easeflow
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Subbasin"PRE-AREA 1"Results for Run'PRE-25 YEAR"
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Subbasin"PRE-AREA 1"Results for Run"PRE- 50 YEAR"
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• Subbasin"PRE-AREA 1"Results for Run"PRE- 100 YEAR"
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minim Run:PRE-100 YEAR Element:PRE-AREA 1 Result:Precipitation mini Run:PRE-100 YEAR Element:PRE-AREA 1 Resutt:Precipitation Loss
Run:PRE-100 YEAR Element:PRE-AREA 1 Result:Outflow ——— Run:PRE-100 YEAR Element:PRE-AREA 1 Result:Baseflow
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Junction "SOUTHWEST OUTLET" Results for Run "POST - 2 YEAR"
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Run:POST- 2 YEAR Element:SOUTHWEST OUTLET Result.Outflovv
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Run:POST- 2 YEAR Element:POST-AREA 3 Result:Outflow
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Junction "SOUTHWEST OUTLET" Results for Run "POST - 10 YEAR"
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— Run:POST- 10 YEAR ElernentSOUTHWEST OUTLET Result:Outflow
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Junction "SOUTHWEST OUTLET" Results for Run "POST - 50 YEAR"
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Run POST- 50 YEAR Element SOUTHWEST OUTLET Result Outflow
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— Run POST- 50 YEAR Element POST-AREA 4 Result Outflow
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• APPENDIX E:
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• HEC-HMS Calculations
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.r, PRE-AREA1
Pre-Developed HEC-HMS Model
Project: 11-0355 Simulation Run: PRE-2 YEAR
Start of Run: 0Dan 2013,00:00 Basin Model: 11-0355 PRE
End of Run: 033an2013,00:00 Meteorologic Model: 2 YR
Compute Time: 18Mar2014, 11:31:25 Control Specifications:Control 1
Show Elements: All Elements = Volume Units: IN AC-FT Sorting: Hydrologic .
Hydrologicr---
Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) (CFS) (IN)
!PRE-AREA 1 0,0037 5.6 01Jan2013, 12:16 ( 3.19
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Project: 11-0355 Simulation Run:PRE- 10 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 PRE
End of Run: 03Jan2013,00:00 Meteorologic Model: 10 YR
Compute Time: 18Mar2014, 11:32:38 Control Specifications: Control 1
Show Elements: All Elements 7M1 Volume Units: ,o IN _ AC-FT Sorting: Hydrologic ,
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) ' (CFS) (IN)
PRE-AREA 1 0.0037 10.4 013an2013, 12:16 6.07
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Project: 11-0355 Simulation Run: PRE-25 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 PRE
End of Run: 03Jan2013,00:00 Meteorologic Model: 25 YR
Compute Time: 18Mar2014, 11:32:58 Control Specifications: Control 1
Show Elements: 'All Elements __. Volume Units: p IN AC-FT Sorting: Hydrologic ,1
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) (CFS) (IN)
."" PRE-AREA 1 0.0037 12.5 01Jan2013, 12:16 7.34
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Project: 11-0355 Simulation Run: PRE-50 YEAR
Start of Run: 013an2013,00:00 Basin Model: 11-0355 PRE
End of Run: 03Jan2013,00:00 Meteorologic Model: 50 YR
Compute lime: 18Mar2014, 11:34:27 Control Specifications: Control 1
Show Elements: All Elements Volume Units: it. IN AC-FT Sorting: Hydrologic
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) (CFS) (IN)
PRE-AREA 1 0.0037 14.1 01Jan 2013, 12:16 8.32
Project: 11-0355 Simulation Run:PRE-100 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 PRE
End of Run: 033an2013,00:00 Meteorologic Model: 100 YR
Compute Time: 18Mar2014, 11:34:45 Control Specifications: Control 1
Show Elements: !AD Elements Volume Units: 4 IN AC-FT Sorting: Hydrologic .
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) (CFS) (IN)
PRE-AREA 1 0.0037 16.3 01Jan2013, 12:16 9.70
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*_01,2E1L0..UTLET
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Protect:11-0355 Simulation Run:POST-2 YEAR
Stott of Run: 011n2013p 00:00 Basin Model; 11-0355 POST
End of Run: 023an2013,00:02 Meteoroloctc Model: 2 YR
Compute Ttme:136tilay2015,09:59:25 Control Sped ications:Control 1
Snow Elements: ,s.1 Elements - Volume Urits: 0 114 AC-FT Sortmg: Hydrologic w
1---- Hydrologic Tranage Area Peak Discharge The d Peak Volume
--- 0e/fleck (M12) (CFS) (IN)
POST-AREA 5 1 0.0012500 2.5 013an2013 12:08 ' 3.34
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POST-AREA 6 .000953 2.1 013an201312:09 191
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POND 1 .000953 1.7 0134n2013,12:15 3.91
P ach-i .000953 1.7 01322013, 1216 191
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Pnlqn'' - 0 0022030 30 011/m2013o 1219 358
Reach-2 1 0.0022030 3.0 013e013, 12:19 3.58
POST ,AREA 3 0,0013750 2.4 01302013,1213 151
POST AREA 4 .000125 0.2 0130n2013, 12:08 2.46
SOUTHWEST OUTLET 0.0037030 5.4 01302013,12:15 3.52
POST AREA 2 00001713 0.0 013an2013, 1207 426
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PO5T-AREA 1 .00001619 0.0 ot3an2013, 12:07 4.28
NORTH OUTLET .0IX103412 1 0.1 1 01)an2013, 12:07 4.26 ,
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Project:11-0355 Simulation Run:POST- 10 YEAR
crier rif pin- ni lArt71111,an.nin eActir,M,1,4•14 1 1.111SR POST
End of Run: 023an2013,00:02 Meteorologic Model: 10 YR
Compute Time:06Moy2015, 10:02:54 Control Speciications:Control 1
511uw time:its: iii aVtlitli kt,:. VIJIWIIM UIW.}. W [IA AC4-1- Xining; nydrulugA. w
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1 llydrologic Drainage Area Peak Discharge Time of Peak Vdume
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Ellerrient
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POST-AREA 5 0.0012500 4.6 01322013, 12:08 6.25
POST-AREA 6 .000953 3.5 013art2013, 1209 6,88
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PON)1 .111VICK1 31 fillAn21111. 17.13
Reach-1 .000953 3.1 Olian2013, 12:14 6.88
POrl)2 0.0022030 5.2 01lan2013, 12:20 6.51
Reach-2 0.0022030 5.2 . 01 Tann t3. 12:20 &St
POST-AREA 3 0.0013750 4,3 013an2013. 1213 6.44
POST-AREA 4 .000125 0.4 01lan2013, 12:08 5.15
SOUTHWEST OUTLET 1 00037030 - 9.5 01Jan1013. 12:15 6.44
POST-AREA 2 00001733 0.1 013an2013, 12:07 7.25
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POST-AREA 1 00001679 0.1 01302013, 12:07 7.25
NOP IN OUTLET .04003412 --' 0.1 111.1an2013, 12:07 7.25
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Project:11-0355 Srrfulation Run:POST-25 YEAR
Start of Run: 01322013,00:00 Bassin Model; 11-0355 POST
End of Run: 02322013,00:02 Meteorologic Model: 25 YR
Compute Tine:06May2015, 10:03:37 Control Specifrcations:Control 1
Show Elements: All Eleni Vo&ne Units: o IN AC-FT Sorting: Hydrologic
x Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Elenwer:t (M12) (CF5) (114) —
POST-AREA 5 0.0012500 5.5 013an2013, 1208 7.52
POST-AREA 6 .000953 4.2 I 013an2013, 12:09 8.18
PON 1 .000953 , 3.8 013an2013, 12:13 8.18
Peach-1 .000953 31 01322013, 12:14 8,17
PCNA 2 0.0022030 6.2 01322013, 12:19 7.80
Reach-2 0.0022030 6.2013an2013, 12:19 7.80
POST -AREA 3 1 0.0013750 5,1 013an2013, 12:13 7.72
POST -AREA 4 .000125 0.5 013an2013, 12:07 6.37
SOUTHWEST OUTLET 0.0037030 11.3
-, 01322013, 12:15 7.72 . '.
POST-AREA 2 .00001733 0.1 013an2013, 12:07 855
POST-AREA 1 .00001679 0,1 01322013, 12:07 1855
NORTH OUTLET .00003412 0,2 013an2013, 12:07 � 8.55
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yr Project:11-0355 Simulation Run:POST-50 YEAR
• Start of Run: 011an2013,00:00 Basin Model: 11-0355 POST
• End of Rt: O23an2013,00:02 Meteorologic Model: 50 YR
Compute Tirrie:06May2015, 10:04:54 Control Specifications:Control I
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r Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (M12) (CFS) (IN)
• [POST AREA 5 0. 012500 6.1 01Jan2013, 12:08 8.S1
• iposT-AREA 6 .0100953 4.6 013an2013, 12:09 9.17
laf NND i 00U953 4.2 013an2013, 12:13 , 9.17
• 1Reach- .000953 4.2 013an2013, 12:14 9.17
LPOND 2 0.0022030 7.0 Ol ari2013,12:19 8.79
• Reach-2 - 0.0022030 7.0 01322013 12:19 8.79
• !POST-AREA 33 0.0013750 5.8 1 01122013, 12:13 8.71
• POST-AREA 4 .000125 0.6 013an2013, 12:07 7.32
.• a.T OUTLET 0.0037030 12.8 101122013, 12:15 8,71
• T AREA 2 001733 ------1—).1-1 Ol3an2013 12'07 955
• T AREA 1 .00001679 0.1 01)&2013,12:07 9.55
• •NORTH OUTLET .00003412 0.2 013612013, 12.07 9.55 i
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Project:11.0355 Simulation Run:POST- 100 YEAR
Start of Run: 01)an2013,00:00 Basin Model: 11-0355 POST
End of Ron: 023an2013,00:02 Meteorologic Model: 100 YR
Compute Tine:05May2015, 10:44:26 Control 5peclfications:Control 1
Show Etcmcnts: Elrr y<r,r; Volume Units: a U AC-FT Sorting: Hydrologic •
Hydrologic Drainage Area Peak Drscharge Time of Peak Volume
Element (M12) (CFS) (IN)
PPOST-AREA 5 0.0012500 7.1 013en2013, 12:08 9.89
POST-AREA 6 --
.000953 5.3 013an2013, 12:09 10.57
013an2013. 12:13 1057.
'POND .000953 4,8 ...
each-1 .000953 4.8 013an2013, 12:11 10.56
POND 2 0,0022030 8.0 013an2013, 12.19 10.17
Reach-2 ._. 0.00220308.0 013an2013. 12:19 10.17
POST-AREA 3 0.0013750 6.6 - 013�an2013, 12:13 10.10
POST-AREA 4 .000125 0.7 013an2013,12:07 8.66
SOUTHWEST OUTLET 0.0037030 14.7 013an2013.12:15 10.09
POST-AREA 2 .00001733 0.1 013an2013, 12:07 10.95
POST -AREA 1 .00001679 0.1 013an2013i 12:07 10.95_
NORTH OUTLET .00003412 0.2 01Jan2013, 12:07 10.95
Protect:11-0355 Simulation Run:post 100 year dogged
Reservoir:POND 2
:mart d P01. 013ori2013,00.00 ()cps tq,Jcl. 11-117.,5 POCir CluthtcJ Oi t'.c
End of Run: 023an2013,00:02 Meteo ro o9c Model: 100 YR
Compute TKne:0614ay2015, 10:59:16 Control Specifications:Control 1
Yoluma Uric; a IN Ac-rT
Computed Results
Peak Inflow: 10.7(CFS) Date/Time of Peak Inflow: 013an2013, 12:11
Peak Discharge: 8.2(CFS) Date/Tithe of Peak Discherge:013en2013, 12:18
Inflow Volume: 10.17(IN) Peak Storage: 0.2(AC-FT)
Discharge Volume:10.11 (IN) Peak Elevation: 2.4(FT)
Post-Developed Clogged Orifice Condition
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® Driveway Culvert Calculations
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HY-8 Culvert Analysis Report
Crossing Discharge Data
Discharge Selection Method: Specify Minimum, Design, and Maximum Flow
Minimum Flow: 0 cfs
Design Flow: 5.1 cfs
Maximum Flow: 10 cfs
Table 1 - Summary of Culvert Flows at Crossing: 11-0355 driveway culvert
Headwater Elevation Total Discharge(cfs) Culvert 2 Discharge Roadway Discharge Iterations
(ft) (cfs) (cfs)
320.06 0.00 0.00 0.00 1
1.#R 1.00 1.00 0.00 1
321.31 2.00 2.00 0.00 1
320.41 3.00 3.00 0.00 1
320.46 4.00 4.00 0.00 1
320.51 5.00 5.00 0.00 1
6111111 IIIIII VIII Si
320.60 7.00 7.00 0.00 1
320.64 8.00 8.00 0.00 1
320.68 9.00 9.00 0.00 1
320.71 10.00 10.00 0.00 1
321.50 37.88 37.88 0.00 Overtopping
Rating Curve Plot for Crossing: 11-0355 driveway culvert
Total Rating Curve
Crossing: 11-0355 driveway culvert
321.6-
321.4--
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a- 320.8-_
4 320.6--
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320.4-
320.2-
320.0,
20.2-320.0-, I I I i IIII II II I I I I I I I I IIII I I I I iii I
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0 5 10 15 20 2f5 30 35
Total Discharge (cfs)
Table 2 - Culvert Summary Table: Culvert 2
Total Culvert Headwater Inlet Control Outlet Flow Normal Critical Outlet Depth Tailwater Outlet Tailwater
Discharge Discharge Elevation(ft) Depth(ft) Control Type Depth(ft) Depth(ft) (ft) Depth(ft) Velocity Velocity
(cfs) (cfs) Depth(ft) (ft/s) (ft/s)
0.00 0.00 320.06 0.000 0.000 0-NF 0.000 0.000 0.000 0.000 0.000 0.000
1.00 1.00 1.#R 0.497 0.0* 3-M1t 0.016 0.014 0.198 0.198 0.381 0.842
2.00 2.00 321.31 0.517 1.252 3-M1t 0.031 0.028 0.284 0.284 2.342 1.027
3.00 3.00 320.41 0.346 0.079 1-S2n 0.047 0.336 0.311 0.349 0.758 1.150
4.00 4.00 320.46 0.402 0.131 1-S2n 0.063 0.389 0.357 0.401 0.893 1.243
5.00 5.00 320.51 0.449 0.177 1-S2n 0.079 0.433 0.396 0.447 1.020 1.320
5.10 5.10 320.51 0.454 0.181 1-S2n 0.080 0.437 0.393 0.451 1.048 1.327
7.00 7.00 320.60 0.539 0.255 1-S2n 0.110 0.514 0.464 0.524 1.249 1.444
8.00 8.00 320.64 0.579 0.288 1-S2n 0.126 0.551 0.487 0.558 1.371 1.495
9.00 9.00 320.68 0.618 0.320 1-S2n 0.142 0.585 0.521 0.590 1.460 1.542
10.00 10.00 320.71 0.655 0.349 1-S2n 0.157 0.617 0.549 0.619 1.557 1.585
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• Straight Culvert
Inlet Elevation(invert):320.06 ft, Outlet Elevation(invert):319.79 ft
• Culvert Length:54.00 ft, Culvert Slope:0.0050
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Water Surface Profile Plot for Culvert: Culvert 2
Crossing - 11-0355 driveway culvert, Design Discharge - 5.1 cfs
Culvert - Culvert 2, Culvert Discharge - 5.1 cfs
338--
336
38-336--
334-
332--
330-
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328--
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326--
324--
322--
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320
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322--
320-_- + - _ s g
=1l1 ! HI liii III ! 1111 IIII
10 0 10 20 30 40 50 60 70
Station (ft)
Site Data - Culvert 2
Site Data Option: Culvert Invert Data
Inlet Station: 0.00 ft
Inlet Elevation: 320.06 ft
Outlet Station: 54.00 ft
Outlet Elevation: 319.79 ft
Number of Barrels: 1
Culvert Data Summary - Culvert 2
Barrel Shape: Circular
Barrel Diameter: 18.00 ft
Barrel Material: Concrete
Embedment: 0.00 in
Barrel Manning's n: 0.0120
Culvert Type: Straight
Inlet Configuration: Mitered to Conform to Slope
Inlet Depression: NONE
Table 3 - Downstream Channel Rating Curve (Crossing: 11-0355 driveway culvert)
Flow(cfs) Water Surface Depth(ft) Velocity(ft/s) Shear(psf) Froude Number
Elev(ft)
0.00 319.79 0.00 0.00 0.00 0.00
1.00 319.99 0.20 0.84 0.06 0.38
2.00 320.07 0.28 1.03 0.09 0.40
3.00 320.14 0.35 1.15 0.11 0.42
4.00 320.19 0.40 1.24 0.13 0.42
5.00 320.24 0.45 1.32 0.14 0.43
5.10 320.24 0.45 1.33 0.14 0.43
7.00 320.31 0.52 1.44 0.16 0.44
8.00 320.35 0.56 1.50 0.17 0.44
9.00 320.38 0.59 1.54 0.18 0.45
10.00 320.41 0.62 1.59 0.19 0.45
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Tailwater Channel Data - 11-0355 driveway culvert
Tailwater Channel Option: Trapezoidal Channel
Bottom Width: 4.00 ft
Side Slope (H:V): 10.00 (_:1)
Channel Slope: 0.0050
Channel Manning's n: 0.0350
Channel Invert Elevation: 319.79 ft
Roadway Data for Crossing: 11-0355 driveway culvert
Roadway Profile Shape: Constant Roadway Elevation
Crest Length: 50.00 ft
Crest Elevation: 321.50 ft
Roadway Surface: Paved
Roadway Top Width: 38.00 ft
29
Appendix G:
Technical Design Summary
Gessner Engineering
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
The Cities of Bryan and College Station both require storm drainage design to follow these
Unified Stormwater Design Guidelines. Paragraph C2 of Section III (Administration) requires
submittal of a drainage report in support of the drainage plan (stormwater management plan)
proposed in connection with land development projects, both site projects and subdivisions.
That report may be submitted as a traditional prose report, complete with applicable maps,
graphs, tables and drawings, or it may take the form of a "Technical Design Summary". The
format and content for such a summary report shall be in substantial conformance with the
description in this Appendix to those Guidelines. In either format the report must answer the
questions (affirmative or negative) and provide, at minimum, the information prescribed in the
"Technical Design Summary" in this Appendix.
The Stormwater Management Technical Design Summary Report shall include several parts
as listed below. The information called for in each part must be provided as applicable. In
addition to the requirements for the Executive Summary, this Appendix includes several
pages detailing the requirements for a Technical Design Summary Report as forms to be
completed. These are provided so that they may be copied and completed or scanned and
digitized. In addition, electronic versions of the report forms may be obtained from the City.
Requirements for the means (medium) of submittal are the same as for a conventional report
as detailed in Section III of these Guidelines.
Note: Part 1 — Executive Summary must accompany any drainage report
required to be provided in connection with any land development project,
regardless of the format chosen for said report.
Note: Parts 2 through 6 are to be provided via the forms provided in this
Appendix. Brief statements should be included in the forms as requested,
but additional information should be attached as necessary.
Part 1 — Executive Summary Report
Part 2 — Project Administration
Part 3 — Project Characteristics
Part 4 — Drainage Concept and Design Parameters
Part 5 — Plans and Specifications
Part 6 — Conclusions and Attestation
STORMWATER MANAGEMENT TECHNICAL DESIGN SUMMARY REPORT
Part 1 — Executive Summary
This is to be a brief prose report that must address each of the seven areas listed below.
Ideally it will include one or more paragraphs about each item.
1. Name, address, and contact information of the engineer submitting the report, and
of the land owner and developer (or applicant if not the owner or developer). The
date of submittal should also be included.
2. Identification of the size and general nature of the proposed project, including any
proposed project phases. This paragraph should also include reference to
STORMWATER DESIGN GUIDELINES Page 1 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
applications that are in process with either City: plat(s), site plans, zoning requests,
or clearing/grading permits, as well as reference to any application numbers or
codes assigned by the City to such request.
3. The location of the project should be described. This should identify the Named
Regulatory Watershed(s) in which it is located, how the entire project area is
situated therein, whether the property straddles a watershed or basin divide, the
approximate acreage in each basin, and whether its position in the Watershed
dictates use of detention design. The approximate proportion of the property in the
city limits and within the ETJ is to be identified, including whether the property
straddles city jurisdictional lines. If any portion of the property is in floodplains as
described in Flood Insurance Rate Maps published by FEMA that should be
disclosed.
4. The hydrologic characteristics of the property are to be described in broad terms:
existing land cover; how and where stormwater drains to and from neighboring
properties; ponds or wetland areas that tend to detain or store stormwater; existing
creeks, channels, and swales crossing or serving the property; all existing drainage
easements (or ROW) on the property, or on neighboring properties if they service
runoff to or from the property.
5. The general plan for managing stormwater in the entire project area must be
outlined to include the approximate size, and extent of use, of any of the following
features: storm drains coupled with streets; detention / retention facilities; buried
conveyance conduit independent of streets; swales or channels; bridges or culverts;
outfalls to principal watercourses or their tributaries; and treatment(s) of existing
watercourses. Also, any plans for reclaiming land within floodplain areas must be
outlined.
6. Coordination and permitting of stormwater matters must be addressed. This is to
include any specialized coordination that has occurred or is planned with other
entities (local, state, or federal). This may include agencies such as Brazos County
government, the Brazos River Authority, the Texas A&M University System, the
Texas Department of Transportation, the Texas Commission for Environmental
Quality, the US Army Corps of Engineers, the US Environmental Protection Agency,
et al. Mention must be made of any permits, agreements, or understandings that
pertain to the project.
7. Reference is to be made to the full drainage report (or the Technical Design
Summary Report) which the executive summary represents. The principal
elements of the main report (and its length), including any maps, drawings or
construction documents, should be itemized. An example statement might be:
"One -page drainage report dated , one set of
construction drawings ( sheets) dated , and a
-page specifications document dated comprise
the drainage report for this project."
STORMWATER DESIGN GUIDELINES Page 2 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 2 — Project Administration Start (Page 2.1)
Engineering and Design Professionals Information
Engineering Firm Name and Address: Jurisdiction
Gessner Engineering City: _ Bryan
2501 Ashford Drive Suite 102 X College Station
College Station, TX 77840 Date of Submittal:
Lead Engineer's Name and Contact Info.(phone, e-mail, fax): Other:
Jeremy N. Peters, 979-680-8840,jpeters@gessnerengineering.com
Supporting Engineering /Consulting Firm(s): Other contacts:
Developer/Owner/Applicant Information
Developer/Applicant Name and Address: Phone and e-mail:
Chuck Moreau - Moreau Family Investments, Ltd. 764-4084
1834 Harris Drive chuck@bvcarpetoutlet.com
College Station, TX 77845
Property Owner(s) if not Developer/ Applicant (&address): Phone and e-mail:
Project Identification
Development Name: Brazos Valley Floor and Design
Is subject property a site project, a single-phase subdivision, or part of a multi-phase subdivision?
Site Project If multi-phase, subject property is phase of
Legal description of subject property (phase) or Project Area:
(see Section II, Paragraph B-3a)
Lot 10, Block 1, Rock Prairie West Business Park
If subject property (phase) is second or later phase of a project, describe general status of all
earlier phases. For most recent earlier phase Include submittal and review dates.
General Location of Project Area, or subject property(phase):
Rock Prairie&Wellborn
In City Limits? Extraterritorial Jurisdiction (acreage):
Bryan: acres. Bryan: College Station:
College Station: 2.38 acres. Acreage Outside ETJ:
STORMWATER DESIGN GUIDELINES Page 3 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D — TECHNICAL DESIGN SUMMARY
Part 2 — Project Administration Continued (page 2.2)
Project Identification (continued)
Roadways abutting or within Project Area or Abutting tracts, platted land, or built
subject property: developments:
N. Graham Rd., Old Wellborn Rd.
Named Regulatory Watercourse(s) &Watershed(s): Tributary Basin(s):
Plat Information For Project or Subject Property (or Phase)
Preliminary Plat File#: Final Plat File#: Date:
Name: Status and Vol/Pg:
If two plats, second name: File #:
Status: Date:
Zoning Information For Project or Subject Property (or Phase)
Zoning Type: PPD RxbisIbta or Proposed? Case Code:
Case Date Status:
Zoning Type: Existing or Proposed? Case Code:
Case Date Status:
Stormwater Management Planning For Project or Subject Property(or Phase)
Planning Conference(s) & Date(s): Participants:
Preliminary Report Required? No Submittal Date Review Date
Review Comments Addressed? Yes No In Writing? When?
Compliance With Preliminary Drainage Report. Briefly describe (or attach documentation
explaining) any deviation(s)from provisions of Preliminary Drainage Report, if any.
STORMWATER DESIGN GUIDELINES Page 4 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 2 — Project Administration Continued (page 2.3)
Coordination For Project or Subject Property (or Phase)
Note: For any Coordination of stormwater matters indicated below, attach documentation
describing and substantiating any agreements, understandings, contracts, or approvals.
Coordination Dept. Contact: Date: Subject:
With Other
Departments of
Jurisdiction
City(Bryan or
College Station)
Coordination With Summarize need(s) & actions taken (include contacts&dates):
Non-jurisdiction
City Needed?
Yes No X
Coordination with Summarize need(s) & actions taken (include contacts&dates):
Brazos County
Needed?
Yes No X
Coordination with Summarize need(s) & actions taken (include contacts&dates):
TxDOT Needed?
Yes No X
Coordination with Summarize need(s) &actions taken (include contacts&dates):
TAMUS Needed?
Yes No X
Permits For Project or Subject Property (or Phase)
As to stormwater management, are permits required for the proposed work from any of the entities
listed below? If so, summarize status of efforts toward that objective in spaces below.
Entity Permitted or Status of Actionsinclude dates
Approved ? Actions (include
US Army Crops of
Engineers
No X Yes
US Environmental
Protection Agency
No X Yes
Texas Commission on
Environmental Quality
No X Yes
Brazos River
Authority
No X Yes
STORMWATER DESIGN GUIDELINES Page 5 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Start (Page 3.1)
Nature and Scope of Proposed Work
Existing: Land proposed for development currently used, including extent of impervious cover?
Site
X Redevelopment of one platted lot, or two or more adjoining platted lots.
Development Building on a single platted lot of undeveloped land.
Project Building on two or more platted adjoining lots of undeveloped land.
(select all Building on a single lot, or adjoining lots, where proposed plat will not form
applicable) a new street (but may include ROW dedication to existing streets).
Other(explain):
Subdivision Construction of streets and utilities to serve one or more platted lots.
Development Construction of streets and utilities to serve one or more proposed lots on
Project lands represented by pending plats.
Site projects: building use(s), approximate floor space, impervious cover ratio.
Describe Subdivisions: number of lots by general type of use, linear feet of streets and
Nature and drainage easements or ROW.
Size of Construction of new parking lot for existing building and construction of new
Proposed 12,000 SF warehouse
Project
Is any work planned on land that is not platted If yes, explain:
or on land for which platting is not pending?
X No Yes
FEMA Floodplains
Is any part of subject property abutting a Named Regulatory Watercourse No X Yes
(Section II, Paragraph B1) or a tributary thereof?
Is any part of subject property in floodplain No X Yes Rate Map
area of a FEMA-regulated watercourse?
Encroachment(s) Encroachment purpose(s): Building site(s) Road crossing(s)
into Floodplain
areas planned? Utility crossing(s) Other (explain):
No X
Yes
If floodplain areas not shown on Rate Maps, has work been done toward amending the FEMA-
approved Flood Study to define allowable encroachments in proposed areas? Explain.
STORMWATER DESIGN GUIDELINES Page 6 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Continued (Page 3.2)
Hydrologic Attributes of Subject Property (or Phase)
Has an earlier hydrologic analysis been done for larger area including subject property?
Yes Reference the study(& date) here, and attach copy if not already in City files.
Is the stormwater management plan for the property in substantial conformance with the
earlier study? Yes No If not, explain how it differs.
No If subject property is not part of multi-phase project, describe stormwater management
X plan for the property in Part 4.
If property is part of multi-phase project, provide overview of stormwater management plan
for Project Area here. In Part 4 describe how plan for subject property will comply
therewith.
Do existing topographic features on subject property store or detain runoff? X No Yes
Describe them (include approximate size, volume, outfall, model, etc).
Any known drainage or flooding problems in areas near subject property? X No Yes
Identify:
Based on location of study property in a watershed, is Type 1 Detention (flood control) needed?
(see Table B-1 in Appendix B)
X Detention is required. Need must be evaluated. Detention not required.
What decision has been reached? By whom?
If the need for How was determination made?
Type 1 Detention
must be evaluated:
STORMWATER DESIGN GUIDELINES Page 7 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Fffactivn FPhruary 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Continued (Page 3.3)
Hydrologic Attributes of Subject Property (or Phase) (continued)
Does subject property straddle a Watershed or Basin divide? X No Yes If yes,
describe splits below. In Part 4 describe design concept for handling this.
Watershed or Basin Larger acreage Lesser acreage
Above-Project Areas(Section II, Paragraph B3-a)
Does Project Area (project or phase) receive runoff from upland areas? X No Yes
Size(s) of area(s) in acres: 1) 2) 3) 4)
Flow Characteristics (each instance) (overland sheet, shallow concentrated, recognizable
concentrated section(s), small creek(non-regulatory), regulatory Watercourse or tributary);
Flow determination: Outline hydrologic methods and assumptions:
Does storm runoff drain from public easements or ROW onto or across subject property?
No Yes If yes, describe facilities in easement or ROW:
Are changes in runoff characteristics subject to change in future? Explain
Conveyance Pathways (Section II, Paragraph C2)
Must runoff from study property drain across lower properties before reaching a Regulatory
Watercourse or tributary? X No Yes
Describe length and characteristics of each conveyance pathway(s). Include ownership of
property(ies).
STORMWATER DESIGN GUIDELINES Page 8 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Continued (Page 3.4)
Hydrologic Attributes of Subject Property (or Phase) (continued)
Conveyance Pathways (continued)
Do drainage If yes,for what part of length? % Created by? plat, or
easements instrument. If instrument(s), describe their provisions.
exist for any
part of
pathway(s)?
x No
Yes
'h► Where runoff must cross lower properties, describe characteristics of abutting lower
property(ies). (Existing watercourses? Easement or Consent aquired?)
• Pathway
• Areas
•
•
• Describe any built or improved drainage facilities existing near the property (culverts,
bridges, lined channels, buried conduit, swales, detention ponds, etc).
• Detention pond on adjacent property.
•
•
•
Nearby
• Drainage Do any of these have hydrologic or hydraulic influence on proposed stormwater
Facilities design? X No Yes If yes, explain:
ler
•
•
•
•
•
•
•
•
•
•
•
• STORMWATER DESIGN GUIDELINES Page 9 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
• Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Start (Page 4.1)
Stormwater Management Concept
Discharge(s) From Upland Area(s)
If runoff is to be received from upland areas, what design drainage features will be used to
accommodate it and insure it is not blocked by future development? Describe for each area,
flow section, or discharge point.
Discharge(s)To Lower Property(ies) (Section II, Paragraph El)
Does project include drainage features (existing or future) proposed to become public via
platting? X No Yes Separate Instrument? X No Yes
Per Guidelines reference above, how will Establishing Easements (Scenario 1)
runoff be discharged to neighboring X Pre-development Release (Scenario 2)
property(ies)? Combination of the two Scenarios
Scenario 1: If easements are proposed, describe where needed, and provide status of actions
on each. (Attached Exhibit#
Scenario 2: Provide general description of how release(s)will be managed to pre-development
conditions (detention, sheet flow, partially concentrated, etc.). (Attached Exhibit#
detention
Combination: If combination is proposed, explain how discharge will differ from pre-
development conditions at the property line for each area (or point)of release.
If Scenario 2, or Combination are to be used, has proposed design been coordinated with
owner(s) of receiving property(ies)? No Yes Explain and provide
documentation.
STORMWATER DESIGN GUIDELINES Page 10 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.2)
Stormwater Management Concept (continued)
Within Project Area Of Multi-Phase Project
Identify gaining Basins or Watersheds and acres shifting:
Will project result
in shifting runoff
between Basins or
between What design and mitigation is used to compensate for increased runoff
Watersheds? from gaining basin or watershed?
X No
Yes
How will runoff from Project 1. With facility(ies) involving other development projects.
Area be mitigated to pre- 2. X Establishing features to serve overall Project Area.
development conditions?
Select any or all of 1, 2, 3. On phase (or site) project basis within Project Area.
and/or 3, and explain below.
1. Shared facility(type&location of facility; design drainage area served; relationship to size of
Project Area): (Attached Exhibit#
2. For Overall Project Area (type&location of facilities): (Attached Exhibit#
Two detention ponds;one located to the southwest of the proposed building
and one to the northwest of the building.
3. By phase (or site) project: Describe planned mitigation measures for phases(or sites) in
subsequent questions of this Part.
Are aquatic echosystems proposed? x No Yes In which phase(s)or
project(s)?
-•
m �
Are other Best Management Practices for reducing stormwater pollutants proposed?
X No Yes Summarize type of BMP and extent of use:
CD
m 0
2
Ta
If design of any runoff-handling facilities deviate from provisions of B-CS Technical
x Specifications, check type facility(ies) and explain in later questions.
Detention elements Conduit elements Channel features
Swales Ditches Inlets Valley gutters Outfalls
Culvert features Bridges Other
STORMWATER DESIGN GUIDELINES Page 11 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.3)
lir Stormwater Management Concept (continued)
• Within Project Area Of Multi-Phase Project (continued)
• Will Project Area include bridge(s)or culvert(s)? No X Yes Identify type and
• general size and In which phase(s).
Culvert under drive at SW of the Proposed Building.
•
•
• If detention/retention serves (will serve)overall Project Area, describe how it relates to subject
1 • phase or site project (physical location, conveyance pathway(s), construction sequence):
• Property is served by two detention ponds;one to the NW and one to the SW of the proposed building.
• Pond 1 discharges into Pond 2 which discharges to SW of site.
•
• Within Or Serving Subject Property(Phase, or Site)
• If property part of larger Project Area, is design in substantial conformance with earlier analysis
and report for larger area? Yes No, then summarize the difference(s):
Identify whether each of the types of drainage features listed below are included, extent of use,
and general characteristics.
Typical shape? Surfaces?
ir -o
• = Steepest side slopes: Usual front slopes: Usual back slopes:
u) >-
•
• a,
Flow line slopes: least Typical distance from travelway:
• ):13 o typical greatest (Attached Exhibit# )
• u, z
• ca
2 x Are longitudinal culvert ends in compliance with B-CS Standard Specifications?
• °'
Q Yes No, then explain:
• At intersections or otherwise, do valley gutters cross arterial or collector streets?
• No Yes If yes explain:
Dom }
• U N
L
• o) `m Are valley gutters proposed to cross any street away from an intersection?
• m 5 o coz No Yes Explain: (number of locations?)
• Tri 2
2 cu
• Q x
•
•
• STORMWATER DESIGN GUIDELINES Page 12 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
• Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D — TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.4)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site)(continued)
Gutter line slopes: Least Usual Greatest
Are inlets recessed on arterial and collector streets? Yes No If"no",
identify where and why.
Will inlets capture 10-year design stormflow to prevent flooding of intersections (arterial
with arterial or collector)? Yes No If no, explain where and why not.
-•
a)
Will inlet size and placement prevent exceeding allowable water spread for 10-year
a) design storm throughout site(or phase)? Yes No If no, explain.
a)
m Sag curves: Are inlets placed at low points? Yes No Are inlets and
conduit sized to prevent 100-year stormflow from ponding at greater than 24 inches?
o Yes No Explain "no" answers.
U)
a)
m
L
Will 100-yr stormflow be contained in combination of ROW and buried conduit on
whole length of all streets? Yes No If no, describe where and why.
Do designs for curb, gutter, and inlets comply with B-CS Technical Specifications?
Yes No If not, describe difference(s) and attach justification.
Are any 12-inch laterals used? No Yes Identify length(s)and where
used.
Pipe runs between system Typical Longest
• } access points (feet):
m Are junction boxes used at each bend? Yes No If not, explain where
>, and why.
cn
•� Z• o
L
Ex Least amount that hydraulic
Are downstream soffits at or below upstream soffits? y
• Yes No If not, explain where and why: grade line is below gutter line
(system-wide):
STORMWATER DESIGN GUIDELINES Page 13 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D — TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.5)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site) (continued)
Describe watercourse(s), or system(s) receiving system discharge(s) below
(include design discharge velocity, and angle between converging flow lines).
0
1) Watercourse (or system),velocity, and angle?
m E 2) Watercourse (or system), velocity, and angle?
o
0
Q c
E a' �.
E 3)Watercourse (or system), velocity, and angle?
c, U-
cn a)
c -a O
o
-0 a
E For each outfall above, what measures are taken to prevent erosion or scour of
receiving and all facilities at juncture?
1)
(I;
a0
a 2)
a)
3)
Are swale(s) situated along property lines between properties? No Yes
Number of instances: For each instance answer the following questions.
Surface treatments (including low-flow flumes if any):
U)
a)
a
• Flow line slopes(minimum and maximum):
c
0
z Outfall characteristics for each (velocity, convergent angle, &end treatment).
a)
To
m
• Will 100-year design storm runoff be contained within easement(s) or platted drainage
ROW in all instances? Yes No If"no" explain:
STORMWATER DESIGN GUIDELINES Page 14 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.6)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site)(continued)
Are roadside ditches used? X No Yes If so, provide the following:
a) Is 25-year flow contained with 6 inches of freeboard throughout ? Yes No
Are top of banks separated from road shoulders 2 feet or more? Yes No
a Are all ditch sections trapezoidal and at least 1.5 feet deep? Yes No
a)
55 For any"no"answers provide location(s) and explain:
0
0
cK
If conduit is beneath a swale, provide the following information (each instance).
Instance 1 Describe general location, approximate length:
u)
>- Is 100-year design flow contained in conduit/swale combination? Yes No
- If "no" explain:
a)
o
o co Space for 100-year storm flow? ROW Easement Width
Z c Swale Surface type, minimum Conduit Type and size, minimum and maximum
.1770 and maximum slopes: slopes, design storm:
0
vi
a� -Fes Inlets Describe how conduit is loaded (from streets/storm drains, inlets by type):
c
c c
ca co
o
o L-
C 0
0• o
0.O E Access Describe how maintenance access is provided (to swale, into conduit):
as
m• 0
c
c .43 Instance 2 Describe general location, approximate length:
-0 E
a) m
u)
c 72 Is 100-year design flow contained in conduit/swale combination? Yes No
o o If "no" explain:
t
E 0 Space for 100-year storm flow? ROW Easement Width
o ' Swale Surface type, minimum Conduit Type and size, minimum and maximum
m and maximum slopes: slopes, design storm:
c a3
o 0 Inlets Describe how conduit is loaded (from streets/storm drains, inlets by type):
di
To c
• °
6
El!
Q Access Describe how maintenance access is provided (to swale, into conduit):
STORMWATER DESIGN GUIDELINES Page 15 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
$ Part 4 — Drainage Concept and Design Parameters Continued (Page 4.7)
• Stormwater Management Concept (continued)
0 Within Or Serving Subject Property (Phase, or Site)(continued)
• If"yes" provide the following information for each instance:
• Instance 1 Describe general location, approximate length, surfacing:
• c
'ca
• E CL
• o w
uiIs 100-year design flow contained in swale? Yes No Is swale wholly
• c > within drainage ROW? Yes No Explain "no" answers:
• a)
• aoei Access Describe how maintenance access is provide:
L o
• 5z
• 0 Instance 2 Describe general location, approximate length, surfacing:
a)
• =
C
• OE
• 3 ,cclIs 100-year design flow contained in swale? Yes No Is swale wholly
a o within drainage ROW? Yes No Explain "no" answers:
• as
• 03 O
_> CC Access Describe how maintenance access is provided:
>
• > .2
s
• 7
Q
Instance 3, 4, etc. If swales are used in more than two instances, attach sheet
providing all above information for each instance.
ago
I., "New" channels: Will any area(s) of concentrated flow be channelized (deepened,
widened, or straightened)or otherwise altered? No Yes If only slightly
• shaped, see"Swales" in this Part. If creating side banks, provide information below.
• c Will design replicate natural channel? Yes No If"no", for each instance
7:13 .c
describe section shape & area, flow line slope (min. & max.), surfaces, and 100-year
• o w design flow, and amount of freeboard:
• co m Instance 1:
• c
a)
E
• a)
o Instance 2:
L
• 0
EO
Z
• a)
c x Instance 3:
• ca
• U
•
•
• STORMWATER DESIGN GUIDELINES Page 16 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
• Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.8)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
Existing channels (small creeks): Are these used? X No Yes
If"yes" provide the information below.
Will small creeks and their floodplains remain undisturbed? X Yes No How
many disturbance instances? Identify each planned location:
For each location, describe length and general type of proposed improvement
(including floodplain changes):
For each location, describe section shape & area, flow line slope (min. & max.),
surfaces, and 100-year design flow.
m
c Watercourses (and tributaries): Aside from fringe changes, are Regulatory
Watercourses proposed to be altered? X No Yes Explain below.
Submit full report describing proposed changes to Regulatory Watercourses. Address
existing and proposed section size and shape, surfaces, alignment, flow line changes,
> length affected, and capacity, and provide full documentation of analysis procedures
a and data. Is full report submitted? Yes No If"no" explain:
E
m
s All Proposed Channel Work: For all proposed channel work, provide information
v requested in next three boxes.
If design is to replicate natural channel, identify location and length here, and describe
design in Special Design section of this Part of Report.
Will 100-year flow be contained with one foot of freeboard? Yes No If
not, identify location and explain:
Are ROW/easements sized to contain channel and required maintenance space?
Yes No If not, identify location(s) and explain:
STORMWATER DESIGN GUIDELINES Page 17 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.9)
•
Stormwater Management Concept (continued)
• Within Or Serving Subject Property(Phase, or Site) (continued)
• How many facilities for subject property project? 2 For each provide info. below.
II For each dry-type facilitiy: Facility 1 POND 1 Facility 2pOND 2
• Acres served &design volume+ 10% 0.61 ac 0.061 ac-ft 0.67 ac 0.165 ac-ft
• 100-yr volume:free flow& plugged 0.032 ac-ft 0.055 ac-ft 0.146 ac-ft 0.174 ac-ft
• Design discharge (10 yr& 25 yr) 3.1 cfs 3.8 cfs 5.2 cfs 6.2 cfs
• Spillway crest at 100-yr WSE? x yes no x yes no
• Berms 6 inches above plugged WSE? x yes no x yes no
• Explain any"no" answers:
•
• a)
m
• For each facility what is 25-yr design Q, and design of outlet structure?
• Facility 1: 3.8 cfs,drainage structure with orifice and weir
ID 0
Z Facility 2: 6.2 cfs,drainage structure with orifice and weir
gir Do outlets and spillways discharge into a public facility in easement or ROW?
• Facility 1: X Yes No Facility 2: X Yes No
mIf"no"explain:
u)
• o
a
2 L
• - For each, what is velocity of 25-yr design discharge at outlet? & at spillway?
Facility 1: 4.75 ft/sec & Facility 2: 13.22 ft/sec & 4.38 ft/sec
0 Are energy dissipation measures used? No x Yes Describe type and
u- location:
o Riprap at discharge points
a)
•
m
m
0
2 For each, is spillway surface treatment other than concrete? Yes or no, and describe:
• Q Facility 1: no,concrete weir
III Facility 2: no,concrete weir
Ill For each, what measures are taken to prevent erosion or scour at receiving facility?
• Facility 1: Riprap
• Facility 2: Riprap
• If berms are used give heights, slopes and surface treatments of sides.
• Facility 1: Pond 1: no berms,grass side slopes 10%-25%
• Pond 2: berm on plan north and west sides, 2.5'max. berm height,
• Facility 2: grass side slopes 16%-25%
•
• STORMWATER DESIGN GUIDELINES Page 18 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
• Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D — TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.10)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
Do structures comply with B-CS Specifications? Yes or no, and explain if"no":
cn
Facility 1; yes
a)
CO CD Facility 2: yes
c �.
o c
o
U
a)
• For additional facilities provide all same information on a separate sheet.
Are parking areas to be used for detention? X No Yes What is
maximum depth due to required design storm?
Roadside Ditches:Will culverts serve access driveways at roadside ditches?
No X Yes If"yes", provide information in next two boxes.
Will 25-yr. flow pass without flowing over driveway in all cases? X Yes No
Without causing flowing or standing water on public roadway? X Yes No
Designs& materials comply with B-CS Technical Specifications? X Yes No
Explain any"no" answers:
cs•
0)
o Are culverts parallel to public roadway alignment? X Yes No Explain:
• a)
N
x Creeks at Private Drives: Do private driveways, drives, or streets cross drainage
ways that serve Above-Project areas or are in public easements/ ROW?
z X No Yes If"yes" provide information below.
How many instances? Describe location and provide information below.
• Location 1:
U
Location 2:
Location 3:
For each location enter value for: 1 2 3
Design year passing without toping travelway?
Water depth on travelway at 25-year flow?
Water depth on travelway at 100-year flow?
For more instances describe location and same information on separate sheet.
STORMWATER DESIGN GUIDELINES Page 19 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D — TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.11)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site)(continued)
Named Regulatory Watercourses (&Tributaries): Are culverts proposed on these
facilities? X No Yes, then provide full report documenting assumptions,
criteria, analysis, computer programs, and study findings that support proposed
design(s). Is report provided? Yes No If"no", explain:
Arterial or Major Collector Streets: Will culverts serve these types of roadways?
cX No Yes How many instances? For each identify the
a) location and provide the information below.
• (0 Instance 1:
Cl
g; Instance 2:
c
O Instance 3:
c
0
o m Yes or No for the 100-year design flow: 1 2 3
z E
x o Headwater WSE 1 foot below lowest curb top?
c
O Spread of headwater within ROW or easement?
E
Is velocity limited per conditions (Table C-11)?
CD
.N C' Explain any"no" answer(s):
• c
✓ o
>, (d
(0 0
0
o 42 Minor Collector or Local Streets: Will culverts serve these types of streets?
.0_ X No Yes How many instances? for each identify the
13 location and provide the information below:
o a�
T Instance 1:
�
c Instance 2:
7
(n o Instance 3:
Cll0 For each instance enter value, or"yes"/"no"for: 1 2 3
• c
g Design yr. headwater WSE 1 ft. below curb top?
< 100-yr. max. depth at street crown 2 feet or less?
E Product of velocity(fps) &depth at crown (ft) _ ?
o Is velocity limited per conditions (Table C-11)?
Limit of down stream analysis(feet)?
Explain any"no" answers:
STORMWATER DESIGN GUIDELINES Page 20 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.12)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site) (continued)
All Proposed Culverts: For all proposed culvert facilities (except driveway/roadside
ditch intersects) provide information requested in next eight boxes.
Do culverts and travelways intersect at 90 degrees? Yes No If not,
vee
identify location(s)and intersect angle(s), and justify the design(s):
Does drainage way alignment change within or near limits of culvert and surfaced
approaches thereto? No Yes If"yes" identify location(s), describe
change(s), and justification:
Are flumes or conduit to discharge into culvert barrel(s)? No Yes If yes,
identify location(s) and provide justification:
Are flumes or conduit to discharge into or near surfaced approaches to culvert ends?
No Yes If"yes" identify location(s), describe outfall design treatment(s):
0
U
> Is scour/erosion protection provided to ensure long term stability of culvert structural
�j components, and surfacing at culvert ends? Yes No If"no" Identify
locations and provide justification(s):
Will 100-yr flow and spread of backwater be fully contained in street ROW, and/or
drainage easements/ ROW? Yes No if not, why not?
Do appreciable hydraulic effects of any culvert extend downstream or upstream to
neighboring land(s) not encompassed in subject property? No Yes If
"yes" describe location(s) and mitigation measures:
Are all culvert designs and materials in compliance with B-CS Tech. Specifications?
Yes No If not, explain in Special Design Section of this Part.
STORMWATER DESIGN GUIDELINES Page 21 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
dowilliniiiiv
•
•
• SECTION IX
• APPENDIX D - TECHNICAL DESIGN SUMMARY
• Part 4 — Drainage Concept and Design Parameters Continued (Page 4.13)
• Stormwater Management Concept (continued)
• Within Or Serving Subject Property(Phase, or Site)(continued)
• Is a bridge included in plans for subject property project? x No Yes
• If"yes" provide the following information.
• Name(s) and functional classification of the roadway(s)?
•
• What drainage way(s) is to be crossed?
•
W m
a)
a
• m`
• A full report supporting all aspects of the proposed bridge(s) (structural, geotechnical,
• hydrologic, and hydraulic factors) must accompany this summary report. Is the report
• provided? Yes No If"no" explain:
•
Is a Stormwater Provide a general description of planned techniques:
*m" Pollution Prevention construction entrance, erosion control silt fence, hay bales at
Plan (SW3P) pond discharge points
0 established for
0 project construction?
No X Yes
C
Special Designs— Non-Traditional Methods
Are any non-traditional methods (aquatic echosystems, wetland-type detention, natural stream
iii replication, BMPs for water quality, etc.) proposed for any aspect of subject property project?
• X No Yes If"yes" list general type and location below.
•
•
I.
A
ifi
Provide full report about the proposed special design(s) including rationale for use and
expected benefits. Report must substantiate that stormwater management objectives will not
• be compromised, and that maintenance cost will not exceed those of traditional design
• solution(s). Is report provided? Yes No If"no"explain:
•
•
•
0
• STORMWATER DESIGN GUIDELINES Page 22 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
• Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.14)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site)(continued)
Special Designs—Deviation From B-CS Technical Specifications
If any design(s) or material(s) of traditional runoff-handling facilities deviate from provisions of
B-CS Technical Specifications, check type facility(ies) and explain by specific detail element.
Detention elements Drain system elements Channel features
Culvert features Swales Ditches Inlets Outfalls
Valley gutters Bridges (explain in bridge report)
In table below briefly identify specific element,justification for deviation(s).
Specific Detail Element Justification for Deviation (attach additional sheets if needed)
1)
2)
3)
4)
5)
Have elements been coordinated with the City Engineer or her/his designee? For each item
above provide`yes" or"no", action date, and staff name:
1)
2)
3)
4)
5)
Design Parameters
Hydrology
Is a map(s) showing all Design Drainage Areas provided? X Yes No
Briefly summarize the range of applications made of the Rational Formula:
N/A. Rational Method can not be used for detention design per BCS Std. Design Guidelines.
What is the size and location of largest Design Drainage Area to which the Rational Formula
has been applied? acres Location (or identifier):
STORMWATER DESIGN GUIDELINES Page 23 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.15)
Design Parameters (continued)
Hydrology(continued)
In making determinations for time of concentration, was segment analysis used?
No X Yes In approximately what percent of Design Drainage Areas? 100
ok
As to intensity-duration-frequency and rain depth criteria for determining runoff flows, were any
criteria other than those provided in these Guidelines used? X No Yes If"yes"
identify type of data, source(s), and where applied:
For each of the stormwater management features listed below identify the storm return
frequencies (year) analyzed (or checked), and that used as the basis for design.
Feature Analysis Year(s) Design Year
Storm drain system for arterial and collector streets
Storm drain system for local streets
Open channels
Swale/buried conduit combination in lieu of channel
Swales
Roadside ditches and culverts serving them
Detention facilities: spillway crest and its outfall 2, 10,25, 50,& 100 100
Detention facilities: outlet and conveyance structure(s) 2, 10,25,50, & 100 2,10,25,50,&100
Detention facilities: volume when outlet plugged
Culverts serving private drives or streets
Culverts serving public roadways
Bridges: provide in bridge report.
Hydraulics
What is the range of design flow velocities as outlined below?
Design flow velocities; Gutters Conduit Culverts Swales Channels
Highest (feet per second)
Lowest (feet per second)
Streets and Storm Drain Systems Provide the summary information outlined below:
Roughness coefficients used: For street gutters:
For conduit type(s) Coefficients:
STORMWATER DESIGN GUIDELINES Page 24 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.16)
Design Parameters (continued)
Hydraulics(continued)
Street and Storm Drain Systems (continued)
For the following, are assumptions other than allowable per Guidelines?
Inlet coefficients? No Yes Head and friction losses No Yes
Explain any"yes"answer:
In conduit is velocity generally increased in the downstream direction? Yes No
Are elevation drops provided at inlets, manholes, and junction boxes? Yes No
Explain any"no" answers:
Are hydraulic grade lines calculated and shown for design storm? Yes No
For 100-year flow conditions? Yes No Explain any"no" answers:
What tailwater conditions were assumed at outfall point(s) of the storm drain system? Identify
each location and explain:
Open Channels If a HEC analysis is utilized, does it follow Sec VI.F.5.a? Yes No
Outside of straight sections, is flow regime within limits of sub-critical flow? Yes No
If"no" list locations and explain:
Culverts If plan sheets do not provide the following for each culvert, describe it here.
For each design discharge, will operation be outlet(barrel) control or inlet control?
Entrance, friction and exit losses:
Bridges Provide all in bridge report
STORMWATER DESIGN GUIDELINES Page 25 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.17)
Design Parameters (continued)
Computer Software
What computer software has been used in the analysis and assessment of stormwater
management needs and/or the development of facility designs proposed for subject property
4.- project? List them below, being sure to identify the software name and version, the date of the
version, any applicable patches and the publisher
•
•
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•
•
•
Part 5 — Plans and Specifications
• Requirements for submittal of construction drawings and specifications do not differ due to use of a
• Technical Design Summary Report. See Section III, Paragraph C3.
•
• Part 6 — Conclusions and Attestation
Conclusions
• Add any concluding information here:
•
•
•
•
Attestation
Provide attestation to the accuracy and completeness of the foregoing 6 Parts of this Technical
Design Summary Drainage Report by signing and sealing below.
"This report (plan) for the drainage design of the development named in Part B was prepared
by me (or under my supervision) in accordance with provisions of the Bryan/College Station
• Unified Drainage Design Guidelines for the owners of the property. All licenses and permits
• required by any and all state and federal regulatory agencies for the proposed drainage
improvements have been issued or fall under applicable general permits."
(01(Yrflost
OF TE
1 a �'�•' '' 'gid,
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• *
Licensed Professional Engineer * •• I a '
• * ...- .:.....i..........
% MELISSA P
7HOMAS_;
• State of Texas PE No. 98398
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• J
STORMWATER DESIGN GUIDELINES Page 26 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
May 29, 2014
Gessner Engineering Job No. 11-0355
Prepared for:
Moreau Family Investments, Ltd.
Mr. Chuck Moreau
In Accordance with:
Unified Storm water Design Guidelines
City of Bryan/City of College Station
Prepared by:
GESSNER ENGINEERING, LLC
College Station, Texas
DRAINAGE DESIGN REPORT
Brazos Valley Floor and Design
College Station, Texas
2
May 29, 2014
Mr. Alan Gibbs, P.E.
City Engineer
City of College Station
1101 Texas Avenue
College Station,TX 77840
Re: Storm Water Drainage Study
Brazos Valley Floor and Design
12900 Old Wellborn Road
College Station,Texas
Gessner Engineering Job No.: 11-0355
Dear Mr. Gibbs,
This report conveys the results of the storm water drainage study conducted by Gessner
Engineering for the proposed redevelopment of Brazos Valley Floor and Design, College Station,
Texas. Gessner Engineering believes that all information contained in this report is valid. Please
contact us if you have any questions or if we can be of further assistance.
This report for the drainage design for Brazos Valley Floor and Design was
prepared by Gessner Engineering in accordance with provisions of the
Bryan/College Station Unified Stormwater Design Guidelines for the owner of the
property.
Sincerely,
GESSNER ENGINEERING LLC, F-7451
t,
,= Zti flf T,F 1
'IA,/ r1/� +r' ` 1* •:40 ,` 5/2-'q*tf -
t 1y I- •MELISSA P. THOMAS�' i
Melissa P. Thomas, P.E. ite
1 98398
.i
( - '...";::- C...,__ I. es,,,:f......._,„,,,,c„..a.
Joshua B. Van Wie, E.I.T., M.S.
0
3
TABLE OF CONTENTS
EXECUTIVE SUMMARY 4
INTRODUCTION 4
CALCULATIONS 5
Time of Concentration 5
Unit Hydrograph 6
Reach Routing 6
Peak Runoff Flow 6
Peak Post-Developed Runoff Flow 7
CONCLUSION 7
APPENDIX
Appendix A: General Location Map
Appendix B: FEMA 100 Year Floodplain Map
Appendix C: Drainage Area Map and Calculations
Appendix D: Hydrographs
Appendix E: HEC-HMS Calculations
Appendix F: Technical Design Summary
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EXECUTIVE SUMMARY
This storm water drainage report is submitted to the City of College Station, Texas for review on
April 2, 2014 by Melissa P. Thomas, P.E. of Gessner Engineering, located at 2501 Ashford Drive,
Suite 102, College Station, Texas 77840.
The proposed project consists of the demolition of the asphalt pavement serving the current
building and construction of a 15,000 square foot (SF) warehouse and associated new concrete
parking. The site will be served by two detention ponds in series. The total area of construction is
approximately 2.38 acres. The subject site currently contains a 2,434 SF retail building to remain, a
1,963 sf metal canopy, a 1,112 sf metal awning, and a 24,631 SF of existing parking lot and
hardscape all to be removed.
The site is located directly northwest of the intersection of Old Wellborn Road and N. Graham
Road. The site is located in the Hopes Creek watershed. The site is not located in the FEMA 100
year flood plain, as shown by FIRM number 48041C0310E. This firmette is included as Appendix B.
Runoff from the overall drainage area generally flows south until reaching N. Graham Road. Water
then flows southwest through a small drainage ditch along N. Graham Road until reaching a
tributary of Hopes Creek. Runoff from the subject site reaches N. Graham Road by sheet flow and
shallow concentrated flow through a small channel in the center of the property. Runoff from the
Carpet Outlet site is stored in a detention pond in the southern corner of the property and
discharged to flow across the property to the southwest of both lots until reaching N. Graham
Road. Under existing conditions, the total flow exiting the lot and reaching the drainage ditch on N.
Graham Road is 16.3 cubic feet per second (cfs) at the peak of the 100 year, Type III, 24 hour storm
event. After development, runoff will be stored in a series of two detention ponds on the subject
property and discharged at the southern corner of the property directly into the ditch along N.
Graham Road. Under proposed conditions the flow into the drainage ditch is 15.7 cfs, at the same
storm event. Additionally, a small portion of the two driveways along the north property line
discharges 0.2 cfs onto the existing Brazos Valley Floor and Design site at the same storm event.
The total peak flow of the subject tract under the proposed conditions is 15.9 cfs.
The post-developed peak flow is below the pre-developed peak at the 100 year storm event and
does not create any issues for downstream properties.
INTRODUCTION
This storm water drainage report is intended to determine the required detention to match pre-
developed storm runoff conditions for the proposed Brazos Valley Floor and Design. The entire
G Gessner Engineering
5
drainage area contributes to the drainage ditch along N. Graham Road. The point of contribution
to the ditch was used for both pre-developed and post-developed conditions analysis.
Drainage Calculations for this site were prepared according to the National Resource Conservation
Method as detailed in Technical Release 55 (TR-55) published in June of 1986. Proposed
improvements include a 15,000 SF building and 50,130 SF concrete pavement and approximately
8,140 SF of detention area. Curve numbers from TR-55 were used based on developed uses as
described above. Pre-developed flows were calculated based on the existing development for the
subject site and based on undeveloped conditions for the Carpet Outlet tract. The calculated pre-
developed and developed flows include the two (2), five (5), ten (10), twenty-five (25), fifty (50) and
one-hundred (100) year storms in accordance with the Bryan/College Station Unified Stormwater
tir
Design Guidelines.
• CALCULATIONS
Calculations were performed according to the USDA TR-55 and with the aid of HEC-HMS 3.5 by the
U.S. Army Corps of Engineers. The output data from HEC-HMS has been provided as Appendix E.
•
Time of Concentration
The time of concentration (travel time) for each drainage area was estimated by summing the flow
time for each segment of travel. For sheet flow, travel time was estimated by Manning's Kinematic
equation:
•I
= 0.007 x(nL)°8
tS°.4P,
•
• Where:
tt = travel time (hours)
n = manning's roughness coefficient
L = flow length (feet)
S = slope (ft/ft)
146 P2 = 2-year, 24 hour rainfall (inches)
For shallow concentrated flow, the travel time was calculated from the flow velocity based on the
slope in the direction of flow. These velocities were taken from Table C-4 of the Bryan College
Station Unified Stormwater Design Guidelines.
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The computed times of concentration for each drainage area are included in Appendix E.
Computed values were increased to a minimum time of six (6) minutes as required, based on
Chapter 3 of TR-55 which limits the minimum Time of Concentration to 0.1 hour or six (6) minutes.
Unit Hydrograph
A generic unit hydrograph was computed by distributing the rainfall depths (Table 1) according to
the distribution factors for the NCRS Type III 24 hour storm. This hydrograph was then applied to
each subarea based on the curve number and time of concentration of that area.
Reach Routing
Hydrographs were routed from subareas to the outflow through the kinematic wave method. This
method allows for hydrographs to be translating with time, but not attenuating. The effects of
backwater flow and pressure flow in channels were neglected.
Peak Runoff Flow
Peak Runoff Flow from the site was determined based on the Type III 24 hour storm applied to
each drainage area. The depth-duration-intervals for each frequency are included in Table 1 below,
and were obtained from Table C-6 in the Unified Stormwater Design Guidelines. Curve Number
values (CN) were determined from Table C-7, Appendix C of the Unified Stormwater Design
Guidelines. Peak pre-developed flows for the subject site adjacent to N. Graham Road are included
in Table 1. Drainage areas and calculations are included on sheet C5.0 and C5.1, which are
attached in Appendix C.
Rainfall Depth (in),24-hr Pre-Developed Peak Flow
Frequency duration (cfs)
2 year 4.50 5.6
10 year 7.40 10.4
25 year 8.40 12.5
50 year _ 9.80 14.1
100 year 11.00 16.3
Table 1:Rainfall Depths and Resulting Flows
Peak Post-Developed Runoff Flow
The post-developed peak flows compared to the pre-developed peak flows are shown in Table 2
below for each storm event. Hydrographs for each storm event are included as Appendix D.
G Gessner Engineering
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Pre-Developed Post-Developed Post-Developed Total Post-
Storm Peak Flow at Peak Flow at Peak Flow at Developed Flow
Event Southwest Outlet Southwest Outlet North Outlet (cfs)
(cfs) (cfs) (cfs)
2 year 5.6 5.5 0.1 5.6
10 year 10.4 10.2 0.1 10.3
25 year 12.5 12.1 0.1 12.2
50 year 14.1 13.7 0.2 13.9
100 year 16.3 15.7 0.2 15.9
Table 2:Pre-Developed and Post-Developed Site Outflows
CONCLUSION
Based on visual evidence, engineering drainage calculations and sound engineering judgment,
Gessner Engineering believes that the post-development flows are reduced for the two (2), ten
(10), twenty-five (25), fifty (50), and one hundred (100) year design storms for this development,
and do not create adverse impacts to downstream properties.
Work Certification
"This report for the drainage design of the Brazos Valley Floor & Design was prepared by me in
accordance with the provisions of the Bryan/College Station Unified Drainage Guidelines for the
owners of the property. All licenses and permits required by any and all state and federal
regulatory agencies for the proposed drainage improvements have been issued."
�ti o rx�4.A
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* ` S1/2.Vt0r"
Licensed Professional Engineer
I MELISSA P. THOMAS 0
State of Texas No. 98398
ftp 98398 ."
t�1`olt`
G Gessner Engineering
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• APPENDIX A:
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• General Location Map
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• APPENDIX B:
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• FEMA 100 Year Floodplain Map
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APPENDIX D:
Hydrographs
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• Subbasin "PRE-AREA 1"Results for Run"PRE-2 YEAR"
• 0.00
• 0.01
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00:00 03:00 06.00 09.00 12:00 15:00 18.00 21:00 00:0(
II 01Jan2013 I
. Legend(Compute Time:07Apr2014,15:22:31)
Run:PRE-2 YEAR Element:PRE-AREA 1 Result-Precipitation Run PRE-2 YEAR Element:PRE-AREA 1 Result:Precipitation Loss
Run:PRE-2 YEAR Element:PRE-AREA 1 Resutt:Outflow ——— Run PRE-2 YEAR Element:PRE-AREA 1 Resutt:Baseflow
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Subbasin"PRE-AREA 1"Results for Run"PRE- 10 YEAR"
0.00
0.02-
0.04
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0.10-
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.080.10 ,
0.12
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00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:0(
I 01Jan2013 I
Legend(Compute Time:07Apr2014,15:22:30)
Run:PRE-10 YEAR Element:PRE-AREA 1 Result Precipitation Run:PRE-10 YEAR Element:PRE-AREA 1 Result:Precipitation Loss
Run:PRE-10 YEAR Element:PRE-AREA 1 Result:Outflow ——- Run:PRE-10 YEAR Element PRE-AREA 1 Result:Baseflaw
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Subbasin"PRE-AREA 1"Results for Run"PRE-25 YEAR"
0.0o-
0.02-
0.06-
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.00-0.06
Q
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0.10 _
0.12 — —__ i ..--
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00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:0[
Ili 01Jan2013
• Legend(Compute Time:07Apr2014,15:22:31)
Run:PRE-25 YEAR Element:PRE-AREA 1 Result:Precipitation Run:PRE-25 YEAR Elemerit:PRE-AREA 1 Resutt:Precipttation Loss
Run:PRE-25 YEAR Element:PRE-AREA 1 Result:Outflow ——— Run:PRE-25 YEAR Element:PRE-AREA 1 Resutt:Baseflow
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Subbasin"PRE-AREA 1"Results for Run"PRE-50 YEAR"
0.00
0.02- ---- —___--?-------------
0.04
= 0.06 ;. ._.
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m
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00:00 03:00 06:00 09:00 12.00 15:00 18:00 21:00 00:0(
I 01Jan2013 I
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• mmem Run:PRE-50 YEAR Element:PRE-AREA 1 Result:PrecipitationRun:PRE-50 YEAR Element:PRE-AREA 1 Result:Precipitation Loss
Run:PRE-50 YEAR Elemer t:PRE-AREA 1 ftesutt:0utflow – Run:PRE-50 YEAR Element:PRE-AREA 1 Resutt:Baseflow
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Subbasin"PRE-AREA 1"Results for Run"PRE- 100 YEAR"
0.00
0.02
0.04-
0.06-
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.040.06c
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0.10-
0.12-
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. 00.00 03:00 06:00 09:00 12:00 15:00 18.00 21:00 00.0(
01Jan2013
• Legend(Compute lime:07Apr2014, 15:22:30)
• Run:PRE-100 YEAR Element:PRE-AREA 1 Resutt:PrecipttationRun:PRE-100 YEAR Element:PRE-AREA 1 Resutt:Precipitation Loss
Run:PRE-100 YEAR Element:PRE-AREA 1 Result:Outflow - Run:PRE-100 YEAR Element:PRE-AREA 1 Resutt:Baseflow
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Junction"SOUTWEST OUTLET"Results for Run "POST- 2 YEAR"
6
5-
4-
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00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:0[
01Jan2013
Legend(Compute Time: 14Apr20 14, 14:36:29)
Run:POST-2 YEAR Element:SOUTWEST OUTLET Result:Outflow ——- Run:POST-2 YEAR Element:REACH-2 Result:Outflow
Run:POST-2 YEAR Element:POST-AREA 3 Result:Outflow ---• Run:POST-2 YEAR Element:REACH-1 Result:Outflow
Run:POST-2 YEAR Element:POST-AREA 4 Result:Outflow
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Junction"SOUTWEST OUTLET"Results for Run"POST- 10 YEAR"
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10-
8-
6-
3
0
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4-
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2-
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00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:01
01Jan2013
Legend(Compute Time: 14Apr 2014,14:36:26)
Run:POST-10 YEAR Element:SOUTWEST OUTLET Result:Outflow ——— Run:POST-10 YEAR Element:REACH-2 Result:Outflow
Run:POST-10 YEAR Element.POST-AREA 3 Result Outflow --- Run.POST-10 YEAR Element:REACH-1 Resul:Outflow
— — Run:POST-10 YEAR Element:POST-AREA 4 Result Outflow
G Gessner Engineering
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Junction"SOUTWEST OUTLET"Results for Run"POST-25 YEAR"
14
12 _..
1
10 __
--- t —_—
s-
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O
u 6-
4- k'
11;
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:1
2- i?j 1,
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-- `�f i.. -/I •`__-`=4 «��.- _— —
00:00 03:00 06:00 09:00 12:00 15:00 15:00 21:00 00:0(
01Jan2013
Legend(Compute Time:14Apr2014, 14:36:28)
Run:POST-25 YEAR Element:SOUTv EST OUTLET Result:Outflow --- Run:POST-25 YEAR Element:REACH-2 Result Outflow
• Run:POST-25 YEAR Element:POST-AREA 3 Result:Outflow --—. Run:POST-25 YEAR Element:REACH-1 Result-Outflow
—--— Run:POST-25 YEAR Element:POST-AREA 4 Result:Outflow
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Junction"SOUTWEST OUTLET"Results for Run"POST-50 YEAR"
14
12-
10-
8-
0D
0
6-
• 4 j.
. 1;
• :I1
• 2-
• l`I \
• 00:00 03:00 06.00 09:00 12:00 15:00 18:00 21:00 00:0(
• 1 01Jan2013 1
Legend(Compute Time: 14Apr2014,14:36:31)
. --
Run:POST-50 YEAR Element:SOUTVVEST OUTLET Resutt:0utflaw — Run:POST-50 YEAR Element:REACH-2 Resutt:0utflaw
— Run:POST-50 YEAR Element:POST-AREA 3 Result:Outflow —-— Run:POST-50 YEAR Element:REACH-1 Result:Outflow
Run:POST-50 YEAR Element:POST-AREA 4 Result:Outflow
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Junction"SOUTWEST OUTLET"Results for Run"POST- 100 YEAR"
16
11111 14-
12-
10-
N 8-
1 Mr 0It tio g
Li
1 • 6
•• j'
a 7y;
• I
lb iti, 1...\
• 00:00 03:00 06:00 09:00 12:0015:0018:00 J 21:00 00:0(
• I 01Jan2013
Legend(Compute Time: 14Apr2014,14:3,5:25)
• Run:POST-100 YEAR Element:SOUT REST OUTLET Result:Outflow ——— Run:POST-100 YEAR Element:REACH-2 Result:Outflow
. Run:POST-100 YEAR Element:POST-AREA 3 Result:Outflow —-—• Run:POST-100 YEAR Element:REACH-1 Result:Outflow
—--— Run:POST-100 YEAR Element:POST-AREA 4 Result:Outflow
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APPENDIX E:
HEC-HMS Calculations
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CPRE-AREA 1
Pre-Developed HEC-HMS Model
Project: 11-0355 Simulation Run: PRE-2 YEAR
Start of Run: 013an2013,00:00 Basin Model: 11-0355 PRE
End of Run: 033an2013,00:00 Meteorologic Model: Z YR
Compute Time: 18Mar2014, 11:31:25 Control Specifications:Control 1
Show Elements 1 All Elements Volume Units: 41)IN AC-FT Sorting: Hydrologic .
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Bement (MI2) (CFS) (IN)
PRE-AREA 1 0.0037 5.6 01Jan2013, 12:16 3.19
Project: 11-0355 Simulation Run:PRE-10 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 PRE
End of Run: 033an2013,00:00 Meteorologic Model: 10 YR
Compute Time: 18Mar2014, 11:32:38 Control Specifications: Control 1
Show Elements: !All Elements ! Volume Units: o IN AC-FT Sorting: :Hydrologic
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element {1Y1I2) (CFS) (IN)
PRE-AREA 1 0.0037 10.4 01Jan2013, 12:16 6.07
ar ---
S
S
411 Project: 11-0355 Simulation Run:PRE-25 YEAR
• Start of Run: 01Jan21J13,00:00 Basin Model: 11-0355 PRE
End of Run: 033an2013,00:00 Meteorologic Model: 25 YR
Compute Time: 18Mar2014,11:32:58 Control Specifications: Control 1
•
Show Elements. 'All Elements ' Volume Units: qi IN AC-FT Sorting: Hydrologic
• Hydrologic Drainage Area Peak Discharge Time of Peak Volume
• Element (MI2) (CFS) (IN)
. PRE-AREA 1 0.0037 12.5 01Jan2013, 12:16 7.34
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Project: 11-0355 Simulation Run: PRE-50 YEAR
Start of Run: 013anZ013,00:00 Basin Model: 11-0355 PRE
End of Run: 033an2013,00:00 Meteorologic Model: 50 YR
Compute Time: 18Mar2014, 11:34:27 Control Specifications: Control 1
• Show Elements: All Elements . Volume Units: o IN AC-FT Sorting: Hydrologic•
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
• Element (MI2) (CFS) (IN)
• PRE-AREA 1 0.0037 14.1 01Jan2013, 12:16 8.32
•
• Project: 11-0355 Simulation Run: PRE- 100 YEAR
•
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 PRE
• End of Run: 033an2013,00:00 Meteorologic Model: 100 YR
• Compute Time: 18Mar2014, 11:34:45 Control Spedfications: Control 1
Show Elements: All Elements Volume Units: IN AC-FT Sorting: Hydrologic
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
• Element (MI2) (CFS) (IN)
PRE-AREA 1 i 0.0037 16.3 IOLlan2013, 12:16 9.70
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L ►.S RTH OUTLET
ve POST-AREA 2
POST-AREA 1
OND 1
.POST-AREA 6
.�e. POST-AREA 5
me POST-AREA 4
Reach 1is POND 2
,r POST-AREA 3
Reach-2
OUTWEST OUTLET
Post-Developed HEC-HMS Model
G Gessner Engineering
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Project: 11-0355 Simulation Run: POST-2 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 POST
End of Run: 02Jan2013,00:02 Meteorologic Model: 2 YR
Compute Time: 14Apr2014, 14:36:29 Control Spedfications: Control 1
Show Elements: All Elements - Volume Units: 34, IN AC-FT Sorting: Hydrologic .
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) (CFS) (IN)
POST-AREA 5 0.0010470 2.2 01Jan2013, 12:08 3.52
POND 2 0.0010470 1.0 01Jan2013, 12:24 3.52
Reach-2 0.0010470 1.0 0lJan2013, 12:24 3.52
POST-AREA 3 0.0013750 2.4 01Jan2013, 12:13 ! 3.51
POST-AREA 6 I .000953 2.1 01Jan2013, 12:09 3.91
POND 1 .000953 1.7 01Jan2013, 12:14 3.91
Reach-1 .000953 1,7 013an2013, 12:15 3.91
POST-AREA 4 .000328 0.6 01Jan2013, 12:08 2.95
SOUT1"LEST OUTLET 0.0037030 5.5 01Jan2013, 12:14 3.57
POST-AREA 2 .00001733 0.0 01Jan2013, 12:07 I 4.26
POST-AREA 1 .00001679 0.0 0llan2013, 12:07 4.26
NORTH OUTLET .00003412 0.1 101Jan2013, 12:07 4.26
Project: 11-0355 Simulation Run:POST-10 YEAR
Start of Run: O 1Jan2013,00:00 Basin Model: 11-0355 POST
End of Run: 02Jan2013,00:02 Meteorologic Model: 10 YR
Compute Time: 14Apr2014, 14:36:26 Control Spedfications:Control 1
Shov.Elements: !All Elements , t Volume Units: f IN :"-) AC-FT Sorting: Hydrologic .1
Ill HydrologicDrainage Area Peak Discharge Time of Peak Volume
• Element (MI2) (CFS) (IN)
POST-AREA 5 0.0010470 3.9 01Jan2013, 12:08 6.46
• POND 2 0.0010470 1.9 01Jan2013, 12:22 6.46
• Reach-2 0.0010470 1.9 01Jan2013, 12:22 6.46
POST-AREA 3 0.0013750 4.3 O 1Jan2013, 12:13 + 6.44
• POST AREA 6 .000953 3.5 O1Jan2013, 12:09 I 6.88
• POND 1 .000953 3.2 01Jan2013, 12:13 6.88
Reach-1 .000953 3.2 01Jan2013, 12:14 1 6.88
• POST-AREA 4 .000328 1.2 01Jan2013, 12:07 5.78
• SOLITWEST OUTLET 0.0037030 10.2 01Jan2013, 12:13 6.50
POST-AREA 2 .00001733 0.1 O 1Jan2O13, 12:07 7.25
POST-AREA 1 .00001679 0.1 01Jan2013, 12:07 7.25
NORTH OUTLET .00003412 0.1 01Jan2013, 12:07 7.25
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Project: 11-0355 Simulation Run: POST-25 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 POST
End of Run: 02Jan2013,00:02 Meteorologic Model: 25 YR
Compute Time: 14Apr2014, 14:36:28 Control Specifications: Control 1
Shove Elements: All Elements Volume Units: d IN AC-FT Sorting: Hydrologic .
Y
Hydrologic Drainage Area Peak Discharge Time of Peak Volum
Element (M12) (CFS) (IN)
POST-AREA 5 0.0010470 4.6 O llan2013, 12:08 7.74
POND 2 0.0010470 2.3 01Jan2013, 12:21 7.74
Reach-2 0.0010470 2.3 0lJan2013, 12:21 7.74
POST AREA 3 0.0013750 5.1 01Jan2013, 12:13 7.72
POST-AREA 6 .000953 4.2 lO llan2013, 12:09 8.18
POND 1 .000953 3.8 01Jan2013, 12:12 8.18
Reach-1 .000953 3.8 01Jan2013, 12:13 8.17
POST-AREA 4 .000328 1.4 01Jan2013, 12:07 7.04
SOUTfn/ESTOUTLET 0.0037030 12.1 OiJan2O13, 12:13 7.78
POST-AREA 2 .00001733 0.1 10 iJan 2O 13, 12:07 8.55
POST-AREA 1 .00001679 0.1 01Jan2013, 12:07 8.55
NORTH OUTLET .00003412 0.2 101Jan2013, 12:07 8.55
Project: 11-0355 Simulation Run: POST-50 YEAR
Start of Run: OiJan2O13,00:00 Basin Model: 11-0355 POST
I End of Run: 02Jan2013,00:02 Meteorologic Model: 50 YR
• Compute Time: 14Apr2014, 14:36:31 Control Specifications: Control 1
• Shore Elements. A F z _ Volume Units: o IN AC-FT Sorting: Hydrologic
• Hydrologic Drainage Area- Peak Discharge Time of Peak Volume
• Element (MI2) (CFS) (IN)
POST-AREA 5 0.0010470 5.2 O lJan2013, 12:08 8.73
• POND 2 0.0010470 2.6 013an2013, 12:21 8.73
• Reach-2 0.0010470 2.6 01Jan2013, 12:21 8.73
POST-AREA 3 0.0013750 5.8 O 1Jan2013, 12:13 8.71
• POST-AREA 6 .000953 4.6 01Jan2013, 12:09 9.17
• POND 1 .000953 4.3 013an2013, 12:12 9.17
Reach-1 .000953 4.3 01Jan2013, 12:13 9.17
• POST-AREA 4 .000328 1.6 01Jan2013, 12:07 8.01
• SOUTWEST OUTLET 0.0037030 13.7 01Jan2013, 12:13 8.77
POST-AREA 2 .00001733 0.1 01Jan2013, 12:07 9.55
• POST-AREA 1 .00001679 0.1 01Jan2013, 12:07 9.55
• NORTH OUTLET .00003412 0.2 101Jan2013, 12:07 9.55
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Project: 11-0355 Simulation Run:POST- 100 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 POST
End of Run: 02Jan2013,00:02 Meteorologic Model: 100 YR
Compute Time: 14Apr2014, 14:36:25 Control Spedfications: Control 1
Shoia Elements: i Al!Elements Volume Units: Q IN AC-FT Sorting: Hydrologic .
Hydrologic Drainage Area Peak Discharge Time of Peak I Volume
Element (MI2) (CFS) (IN)
POST-AREA 5 0.0010470 6.0 01Jan2013, 12:08 10.12
POND 2 0.0010470 3,0 01Jan2013, 12:21 10.12
Reach-2 0.0010470 3.0 01Jan2013, 12:21 10.12
POST-AREA 3 0.0013750 6.6 01Jan2013, 12:13 10.10
POST-AREA 6 .000953 5.3 01Jan2013, 12:09 10.57
POND 1 .000953 4.9 01Jan2013, 12:12 10.57
Reach-1 .000953 4.9 101Jan2013, 12:13 10.56
POST AREA 4 .000328 1.8
101Jan2013, 12:07 9.38
SOUfWEST OUTLET 0,0037030 15,7 01Jan2013, 12:13 10.16
POST-AREA 2 .00001733 0.1 01Jan2013, 12:07 10.95
!POST-AREA 1 .00001679 0.1 01Jan2013, 12:07 10.95
(NORTH OUTLET .00003412 0.2 01Jan2013, 12:07 10.95
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APPENDIX F:
Technical Design Summary
0 Gessner Engineering
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 2 — Project Administration Start (Page 2.1)
Engineering and Design Professionals Information
Engineering Firm Name and Address: Jurisdiction
Gessner Engineering City: Bryan
2501 Ashford Drive Suite 102 X College Station
College Station,TX 77840 Date of Submittal:
Lead Engineer's Name and Contact Info.(phone, e-mail, fax): Other:
Jeremy N. Peters,979-680-8840,jpeters@gessnerengineering.com
Supporting Engineering /Consulting Firm(s): Other contacts:
Developer/Owner/Applicant Information
Developer/Applicant Name and Address: Phone and e-mail:
Chuck Moreau - Moreau Family Investments, Ltd. 764-4084
1834 Harris Drive chuck@bvcarpetoutlet.com
College Station,TX 77845
Property Owner(s) if not Developer/ Applicant (&address): Phone and e-mail:
1: Project Identification
Development Name: Brazos Valley Floor and Design
Is subject property a site project, a single-phase subdivision, or part of a multi-phase subdivision?
Site Project If multi-phase, subject property is phase of
• Legal description of subject property (phase) or Project Area:
S (see Section II, Paragraph B-3a)
Lot 10, Block 1, Rock Prairie West Business Park
4111 If subject property (phase) is second or later phase of a project, describe general status of all
• earlier phases. For most recent earlier phase Include submittal and review dates.
General Location of Project Area, or subject property (phase):
Rock Prairie&Wellborn
I •
In City Limits? Extraterritorial Jurisdiction (acreage):
r.,
Bryan: acres. Bryan: College Station:
College Station: 2.38 acres. Acreage Outside ETJ:
STORMWATER DESIGN GUIDELINES Page 3 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
■ t Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 2 — Proiect Administration Continued (page 2.2)
Project Identification (continued)
Roadways abutting or within Project Area or Abutting tracts, platted land, or built
subject property: developments:
N.Graham Rd.,Old Wellborn Rd.
Named Regulatory Watercourse(s) &Watershed(s): Tributary Basin(s):
Plat Information For Project or Subject Property (or Phase)
Preliminary Plat File#: _ Final Plat File#: Date:
Name: Status and Vol/Pg:
If two plats, second name: File#:
Status: Date:
Zoning Information For Project or Subject Property (or Phase)
Zoning Type: PPD gxi6i1n or Proposed? Case Code:
Case Date Status:
Zoning Type: Existing or Proposed? Case Code:
Case Date Status:
Stormwater Management Planning For Project or Subject Property (or Phase)
Planning Conference(s) & Date(s): Participants:
C.
•
• Preliminary Report Required? No Submittal Date Review Date
Review Comments Addressed? Yes No In Writing? When?
Compliance With Preliminary Drainage Report. Briefly describe (or attach documentation
• explaining) any deviation(s)from provisions of Preliminary Drainage Report, if any.
•
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• STORMWATER DESIGN GUIDELINES Page 4 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
• Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D — TECHNICAL DESIGN SUMMARY
Part 2 - Project Administration Continued (page 2.3)
Coordination For Project or Subject Property (or Phase)
Note: For any Coordination of stormwater matters indicated below, attach documentation
describing and substantiating any agreements, understandings, contracts, or approvals.
Dept. Contact: Date: Subject:
Coordination
With Other
Departments of
Jurisdiction
City (Bryan or
College Station)
Coordination With Summarize need(s) &actions taken (include contacts &dates):
Non jurisdiction
City Needed?
Yes No X
Coordination with Summarize need(s) &actions taken (include contacts &dates):
Brazos County
Needed?
Yes No X
Coordination with Summarize need(s) &actions taken (include contacts &dates):
TxDOT Needed?
Yes No X
Coordination with Summarize need(s) &actions taken (include contacts &dates):
TAMUS Needed?
II
Yes No X
•
Permits For Project or Subject Property (or Phase)
• As to stormwater management, are permits required for the proposed work from any of the entities
• listed below? If so, summarize status of efforts toward that objective in spaces below.
• Entity Permitted or Status of Actions (include dates)
Approved .
• US Army Crops of
• Engineers
• No X Yes
US Environmental
Protection Agency
• No X Yes
' 0 Texas Commission on
• Environmental Quality
• No X Yes
Brazos River
Authority
• No X Yes
•
STORMWATER DESIGN GUIDELINES Page 5 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Start (Page 3.1)
Nature and Scope of Proposed Work
Existing: Land proposed for development currently used, including extent of impervious cover?
Site
X Redevelopment of one platted lot, or two or more adjoining platted lots.
Development Building on a single platted lot of undeveloped land.
Project Building on two or more platted adjoining lots of undeveloped land.
(select all Building on a single lot, or adjoining lots, where proposed plat will not form
applicable) a new street (but may include ROW dedication to existing streets).
Other(explain):
Subdivision Construction of streets and utilities to serve one or more platted lots.
Development Construction of streets and utilities to serve one or more proposed lots on
Project lands represented by pending plats.
Site projects: building use(s), approximate floor space, impervious cover ratio.
Describe Subdivisions: number of lots by general type of use, linear feet of streets and
Nature and drainage easements or ROW.
Size of Construction of new parking lot for existing building and construction of new
Proposed 12,000 SF warehouse
Project
Is any work planned on land that is not platted If yes, explain:
or on land for which platting is not pending?
X No Yes
FEMA Floodplains
Is any part of subject property abutting a Named Regulatory Watercourse No X Yes
(Section II, Paragraph B1)or a tributary thereof?
Is any part of subject property in floodplain No X Yes Rate Map
area of a FEMA-regulated watercourse?
Encroachment(s) Encroachment purpose(s): Building site(s) Road crossing(s)
into Floodplain
areas planned? Utility crossing(s) Other (explain):
No X
Yes
If floodplain areas not shown on Rate Maps, has work been done toward amending the FEMA-
approved Flood Study to define allowable encroachments in proposed areas? Explain.
STORMWATER DESIGN GUIDELINES Page 6 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Continued (Page 3.2)
Hydrologic Attributes of Subject Property (or Phase)
Has an earlier hydrologic analysis been done for larger area including subject property?
Yes Reference the study(& date) here, and attach copy if not already in City files.
Is the stormwater management plan for the property in substantial conformance with the
earlier study? Yes No If not, explain how it differs.
No If subject property is not part of multi-phase project, describe stormwater management
X plan for the property in Part 4.
If property is part of multi-phase project, provide overview of stormwater management plan
for Project Area here. In Part 4 describe how plan for subject property will comply
therewith.
Do existing topographic features on subject property store or detain runoff? X No Yes
Describe them (include approximate size, volume, outfall, model, etc).
Any known drainage or flooding problems in areas near subject property? X No Yes
Identify:
Based on location of study property in a watershed, is Type 1 Detention (flood control) needed?
(see Table B-1 in Appendix B)
X Detention is required. Need must be evaluated. Detention not required.
What decision has been reached? By whom?
If the need for How was determination made?
Type 1 Detention
must be evaluated:
STORMWATER DESIGN GUIDELINES Page 7 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Continued (Page 3.3)
Hydrologic Attributes of Subject Property (or Phase) (continued)
Does subject property straddle a Watershed or Basin divide? X No Yes If yes,
describe splits below. In Part 4 describe design concept for handling this.
Watershed or Basin Larger acreage Lesser acreage
Above-Project Areas(Section II, Paragraph B3-a)
Does Project Area (project or phase) receive runoff from upland areas? X No Yes
Size(s) of area(s) in acres: 1) 2) 3) 4)
Flow Characteristics (each instance) (overland sheet, shallow concentrated, recognizable
concentrated section(s), small creek (non-regulatory), regulatory Watercourse or tributary);
Flow determination: Outline hydrologic methods and assumptions:
Does storm runoff drain from public easements or ROW onto or across subject property?
No Yes If yes, describe facilities in easement or ROW:
Are changes in runoff characteristics subject to change in future? Explain
Conveyance Pathways (Section II, Paragraph C2)
Must runoff from study property drain across lower properties before reaching a Regulatory
Watercourse or tributary? X No Yes
Describe length and characteristics of each conveyance pathway(s). Include ownership of
property(ies).
STORMWATER DESIGN GUIDELINES Page 8 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Continued (Page 3.4)
Hydrologic Attributes of Subject Property (or Phase) (continued)
Conveyance Pathways (continued)
Do drainage If yes, for what part of length? % Created by? plat, or
easements instrument. If instrument(s), describe their provisions.
exist for any
part of
pathway(s)?
X No
Yes
Where runoff must cross lower properties, describe characteristics of abutting lower
property(ies). (Existing watercourses? Easement or Consent aquired?)
Pathway
Areas
Describe any built or improved drainage facilities existing near the property (culverts,
bridges, lined channels, buried conduit, swales, detention ponds, etc).
Detention pond on adjacent property.
Nearby
Drainage Do any of these have hydrologic or hydraulic influence on proposed stormwater
Facilities design? X No Yes If yes, explain:
STORMWATER DESIGN GUIDELINES Page 9 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
•
Part 4— Drainage Concept and Design Parameters Start (Page 4.1)
•
Stormwater Management Concept
Discharge(s) From Upland Area(s)
If runoff is to be received from upland areas, what design drainage features will be used to
accommodate it and insure it is not blocked by future development? Describe for each area,
flow section, or discharge point.
C
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Discharge(s)To Lower Property(ies) (Section II, Paragraph El)
Does project include drainage features (existing or future) proposed to become public via
platting? X No Yes Separate Instrument? X No Yes
Per Guidelines reference above, how will Establishing Easements(Scenario 1)
runoff be discharged to neighboring X Pre-development Release (Scenario 2)
property(ies)? Combination of the two Scenarios
• Scenario 1: If easements are proposed, describe where needed, and provide status of actions
on each. (Attached Exhibit#
•
• Scenario 2: Provide general description of how release(s)will be managed to pre-development
conditions (detention, sheet flow, partially concentrated, etc.). (Attached Exhibit#.
detention
Combination: If combination is proposed, explain how discharge will differ from pre-
development conditions at the property line for each area (or point)of release.
If Scenario 2, or Combination are to be used, has proposed design been coordinated with
owner(s)of receiving property(ies)? No Yes Explain and provide
• documentation.
•
•
•
024
STORMWATER DESIGN GUIDELINES Page 10 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.2)
Stormwater Management Concept (continued)
Within Project Area Of Multi-Phase Project
Identify gaining Basins or Watersheds and acres shifting:
Will project result
in shifting runoff
between Basins or
between What design and mitigation is used to compensate for increased runoff
Watersheds? from gaining basin or watershed?
X No
Yes
How will runoff from Project 1. With facility(ies) involving other development projects.
Area be mitigated to pre- 2. X Establishing features to serve overall Project Area.
development conditions?
Select any or all of 1, 2, 3. On phase (or site) project basis within Project Area.
and/or 3, and explain below.
1. Shared facility(type &location of facility; design drainage area served; relationship to size of
Project Area): (Attached Exhibit#
2. For Overall Project Area (type&location of facilities): (Attached Exhibit#
Two detention ponds;one located to the southwest of the proposed building
and one to the northwest of the building.
3. By phase (or site)project: Describe planned mitigation measures for phases(or sites) in
subsequent questions of this Part.
Are aquatic echosystems proposed? x No Yes In which phase(s)or
project(s)?
�•
m w
c >- Are other Best Management Practices for reducing stormwater pollutants proposed?
a X No Yes Summarize type of BMP and extent of use:
rn
N
O o
o z
• x If design of any runoff-handling facilities deviate from provisions of B-CS Technical
O Specifications, check type facility(ies) and explain in later questions.
Detention elements Conduit elements Channel features
Swales Ditches Inlets Valley gutters Outfalls
Culvert features Bridges Other
STORMWATER DESIGN GUIDELINES Page 11 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D — TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.3)
Stormwater Management Concept (continued)
Within Project Area Of Multi-Phase Project (continued)
Will Project Area include bridge(s) or culvert(s)? No X Yes Identify type and
general size and In which phase(s).
Culvert under drives at NW and SW of the Proposed Building.
If detention/retention serves (will serve)overall Project Area, describe how it relates to subject
phase or site project (physical location, conveyance pathway(s), construction sequence):
Property is served by two detention ponds;one to the NW and one to the SW of the proposed building.
Both ponds discharge to SW of site.
Within Or Serving Subject Property (Phase, or Site)
If property part of larger Project Area, is design in substantial conformance with earlier analysis
and report for larger area? Yes No, then summarize the difference(s):
r
•
• Identify whether each of the types of drainage features listed below are included, extent of use,
and general characteristics.
• Typical shape? Surfaces?
•
411 a)
a Steepest side slopes: Usual front slopes: Usual back slopes:
41
m
• Flow line slopes: least Typical distance from travelway:
• o typical greatest
(Attached Exhibit#
(, z
° x Are longitudinal culvert ends in compliance with B-CS Standard Specifications?
• Q Yes No, then explain:
•
At intersections or otherwise, do valley gutters cross arterial or collector streets?
} No Yes If yes explain:
L
wAre valley gutters proposed to cross any street away from an intersection?
T. 5z No Yes Explain: (number of locations?)
m
ca
Q X
STORMWATER DESIGN GUIDELINES Page 12 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.4)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
Gutter line slopes: Least Usual Greatest
Are inlets recessed on arterial and collector streets? Yes No If"no",
'O'" identify where and why.
C
w Will inlets capture 10-year design stormflow to prevent flooding of intersections (arterial
41, with arterial or collector)? Yes No If no, explain where and why not.
III -.
a)
Will inlet size and placement prevent exceeding allowable water spread for 10-year
m design storm throughout site (or phase)? Yes No If no, explain.
• � 17
41 (11 S Sag curves: Are inlets placed at low points? Yes No Are inlets and
conduit sized to prevent 100-year stormflow from ponding at greater than 24 inches?
o Yes No Explain "no" answers.
i
.3
En
411 a)
Q)
m Will 100-yr stormflow be contained in combination of ROW and buried conduit on
Q whole length of all streets? Yes No If no, describe where and why.
Do designs for curb, gutter, and inlets comply with B-CS Technical Specifications?
• Yes No If not, describe difference(s) and attach justification.
•
•
Are any 12-inch laterals used? No Yes Identify length(s) and where
used.
40 a) Pipe runs between system
co co
) access points (feet): Typical Longest
aE) Are junction boxes used at each bend? Yes No If not, explain where
and why.
• 0
'E-§ O
Z
E X
Are downstream soffits at or below upstream soffits? Least amount that hydraulic
_w Yes No If not, explain where and why: grade line is below gutter line
(system-wide):
STORMWATER DESIGN GUIDELINES Page 13 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D — TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.5)
•
• Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
• Describe watercourse(s), or system(s) receiving system discharge(s) below
(include design discharge velocity, and angle between converging flow lines).
• U
f 1) Watercourse (or system), velocity, and angle?
•
-
m-
E 2) Watercourse (or system), velocity, and angle?
C o
C
o
� c
•
E w
• E — 3)Watercourse (or system), velocity, and angle?
c/
> a)
•
� O
0 ` o
a
E For each outfall above, what measures are taken to prevent erosion or scour of
La receiving and all facilities at juncture?
u)
0 1)
2)
• a)
0 3)
Are swale(s) situated along property lines between properties? No Yes
Number of instances: For each instance answer the following questions.
Surface treatments (including low-flow flumes if any):
a)
in } Flow line slopes (minimum and maximum):
0
ami o
z Outfall characteristics for each (velocity, convergent angle, &end treatment).
a)
x
a)
Will 100-year design storm runoff be contained within easement(s) or platted drainage
ROW in all instances? Yes No If"no" explain:
•
I
STORMWATER DESIGN GUIDELINES Page 14 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.6)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
Are roadside ditches used? X No Yes If so, provide the following:
Is 25-year flow contained with 6 inches of freeboard throughout ? Yes No
4--2 Are top of banks separated from road shoulders 2 feet or more? Yes No
ezo
Are all ditch sections trapezoidal and at least 1.5 feet deep? Yes No
a) p P
For any"no" answers provide location(s) and explain:
a-3
cc
If conduit is beneath a swale, provide the following information (each instance).
Instance 1 Describe general location, approximate length:
a)
>- Is 100-year design flow contained in conduit/swale combination? Yes No
If "no" explain:
a)
U
o as Space for 100-year storm flow? ROW Easement Width
z _c Swale Surface type, minimum Conduit Type and size, minimum and maximum
x m and maximum slopes: slopes, design storm:
•• m Inlets Describe how conduit is loaded (from streets/storm drains, inlets by type):
>,
C c
U
• o o Access Describe how maintenance access is provided (to swale, into conduit):
• 5 m
• m
•
-�
a, Instance 2 Describe general location, approximate length:
• a) ct
E
c 7 Is 100-year design flow contained in conduit/swale combination? Yes No
o o If "no" explain:
c
c
ip E Space for 100-year storm flow? ROW Easement Width
o
m Swale Surface type, minimum Conduit Type and size, minimum and maximum
m and maximum slopes: slopes, design storm:
c a3
0
a)
Inlets Describe how conduit is loaded (from streets/storm drains, inlets by type):
Tu c
3 0
Access Describe how maintenance access is provided (to swale, into conduit):
r
•
S
STORMWATER DESIGN GUIDELINES Page 15 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
• Effective February 2007 As Revised August 2012
F
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.7)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
If"yes" provide the following information for each instance:
Instance 1 Describe general location, approximate length, surfacing:
-a
Ex
I-1-1
ui Is 100-year design flow contained in swale?
o Yes No Is swale wholly
c within drainage ROW? Yes No Explain "no" answers:
2
• a)
.>
• a)
Access Describe how maintenance access is provide:
o
411 Z
-0
• x
Instance 2 Describe general location, approximate length, surfacing:
Cv -o
a)
C,
• _0
• E cl)
o
_c
Is 100-year design flow contained in swale? Yes No Is swale wholly
a)
within drainage ROW? Yes No Explain "no" answers:
w 0
= Access Describe how maintenance access is provided:
• § 0
•
Instance 3, 4, etc. If swales are used in more than two instances, attach sheet
providing all above information for each instance.
"New" channels: Will any area(s) of concentrated flow be channelized (deepened,
widened, or straightened) or otherwise altered? No Yes If only slightly
shaped, see "Swales" in this Part. If creating side banks, provide information below.
.c Will design replicate natural channel? Yes No If"no", for each instance
ow T,L(7' describe section shape & area, flow line slope (min. & max.), surfaces, and 100-year
• design flow, and amount of freeboard:
'a
• u) Instance 1:
•
a)
• a)
> Instance 2:
• 2
0.
• Tu.
x Instance 3:
• c
_c
STORMWATER DESIGN GUIDELINES Page 16 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.8)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site)(continued)
Existing channels (small creeks): Are these used? X No Yes
If"yes" provide the information below.
Will small creeks and their floodplains remain undisturbed? X Yes No How
many disturbance instances? Identify each planned location:
For each location, describe length and general type of proposed improvement
(including floodplain changes):
For each location, describe section shape &area, flow line slope (min. & max.),
surfaces, and 100-year design flow.
a)
Watercourses (and tributaries): Aside from fringe changes, are Regulatory
• Watercourses proposed to be altered? X No Yes Explain below.
• Submit full report describing proposed changes to Regulatory Watercourses. Address
existing and proposed section size and shape, surfaces, alignment, flow line changes,
> length affected, and capacity, and provide full documentation of analysis procedures
a and data. Is full report submitted? Yes No If"no" explain:
E
m
• All Proposed Channel Work: For all proposed channel work, provide information
requested in next three boxes.
If design is to replicate natural channel, identify location and length here, and describe
design in Special Design section of this Part of Report.
Will 100-year flow be contained with one foot of freeboard? Yes No If
not, identify location and explain:
Are ROW/easements sized to contain channel and required maintenance space?
Yes No If not, identify location(s)and explain:
STORMWATER DESIGN GUIDELINES Page 17 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.9)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
How many facilities for subject property project? 2 For each provide info. below.
For each dry-type facilitiy: Facility 1 POND 1 Facility 2POND 2
Acres served & design volume + 10% 0.61 ac 0.061 ac-ft 0.67 ac 0.165 ac-ft
100-yr volume:free flow& plugged 0.028ac-ft 0.055 ac-ft 0.61 0.15 ac-ft
Design discharge (10 yr& 25 yr) 3.2 cfs 3.8 cfs 1.9 cfs 2.3 cfs
Spillway crest at 100-yr WSE? x yes no x yes no
Berms 6 inches above plugged WSE? x yes no x yes no
Explain any"no" answers:
U)
a)
>x
For each facility what is 25-yr design Q, and design of outlet structure?
Facility 1: 3.8 cfs
0
z Facility 2: 2.3 cfs
Do outlets and spillways discharge into a public facility in easement or ROW?
Facility 1: X Yes No Facility 2: X Yes No
0 If"no" explain:
U)
0
0
o_ For each, what is velocity of 25-yr design discharge at outlet? & at spillway?
a) Facility 1: & 4.75 ft/sec Facility 2: 13.22 ft/sec & 4.38 ft/sec
73.
Are energy dissipation measures used? No x Yes Describe type and
location:
Riprap at discharge points
c
a)
m
0
For each, is spillway surface treatment other than concrete? Yes or no, and describe:
Facility 1: no,concrete weir
Facility 2: no, concrete weir
For each, what measures are taken to prevent erosion or scour at receiving facility?
Facility 1: Riprap
Facility 2: Riprap
If berms are used give heights, slopes and surface treatments of sides.
Facility 1: Pond 1: no berms, grass side slopes 10%-25%
Pond 2: berm on plan north and west sides, 1.2'max. berm height,
Facility 2: grass side slopes 16%-23%
STORMWATER DESIGN GUIDELINES Page 18 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.10)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site)(continued)
Do structures comply with B-CS Specifications? Yes or no, and explain if"no":
Facility 1; yes
a)
z Facility 2: yes
c .--
o c
f= O
a) U
o For additional facilities provide all same information on a separate sheet.
Are parking areas to be used for detention? X No Yes What is
maximum depth due to required design storm?
Roadside Ditches: Will culverts serve access driveways at roadside ditches?
No X Yes If"yes", provide information in next two boxes.
Will 25-yr. flow pass without flowing over driveway in all cases? X Yes No
Without causing flowing or standing water on public roadway? X Yes No
Designs & materials comply with B-CS Technical Specifications? X Yes No
Explain any "no" answers:
0
0)
oAre culverts parallel to public roadway alignment? X Yes No Explain:
U U
a)
(II
Q x Creeks at Private Drives: Do private driveways, drives, or streets cross drainage
m ways that serve Above-Project areas or are in public easements/ ROW?
z X No Yes If"yes" provide information below.
z How many instances? Describe location and provide information below.
a) Location 1:
z
U
Location 2:
Location 3:
For each location enter value for: 1 2 3
Design year passing without toping travelway?
Water depth on travelway at 25-year flow?
Water depth on travelway at 100-year flow?
For more instances describe location and same information on separate sheet.
STORMWATER DESIGN GUIDELINES Page 19 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
•
•
• SECTION IX
• APPENDIX D — TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.11)
• Stormwater Management Concept (continued)
• Within Or Serving Subject Property (Phase, or Site) (continued)
Named Regulatory Watercourses (&Tributaries): Are culverts proposed on these
facilities? X No Yes, then provide full report documenting assumptions,
criteria, analysis, computer programs, and study findings that support proposed
design(s). Is report provided? Yes No If"no", explain:
I .
a� Arterial or Major Collector Streets: Will culverts serve these types of roadways?
c X No Yes How many instances? For each identify the
m location and provide the information below.
m Instance 1:
r > a
• Instance 2:
•
O Instance 3:
o
o .ta' Yes or No for the 100-year design flow: 1 2 3
z E
x o Headwater WSE 1 foot below lowest curb top?
a) Spread of headwater within ROW or easement?
•
�; ° Is velocity limited per conditions (Table C-11)?
N m Explain any"no" answer(s):
• c
o
l 3 O
- 4)
o Minor Collector or Local Streets: Will culverts serve these types of streets?
0 9 X No Yes How many instances? for each identify the
location and provide the information below:
a Q)
Instance 1:
c Instance 2:
U) o Instance 3:
u,
cFor each instance enter value, or"yes"/"no"for: 1 2 3
U C6
c Design yr. headwater WSE 1 ft. below curb top?
< .� 100-yr. max. depth at street crown 2 feet or less?
• E Product of velocity (fps) &depth at crown (ft) = ?
o Is velocity limited per conditions (Table C-11)?
• Limit of down stream analysis (feet)?
• Explain any "no" answers:
•
S
•
•
•
STORMWATER DESIGN GUIDELINES Page 20 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
• Effective February 2007 As Revised August 2012
•
•
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.12)
•
Stormwater Management Concept (continued)
0.4 Within Or Serving Subject Property (Phase, or Site) (continued)
All Proposed Culverts: For all proposed culvert facilities (except driveway/roadside
ditch intersects) provide information requested in next eight boxes.
r Do culverts and travelways intersect at 90 degrees? Yes No If not,
identify location(s) and intersect angle(s), and justify the design(s):
Does drainage way alignment change within or near limits of culvert and surfaced
approaches thereto? No Yes If"yes" identify location(s), describe
change(s), and justification:
Are flumes or conduit to discharge into culvert barrel(s)? No Yes If yes,
identify location(s) and provide justification:
Are flumes or conduit to discharge into or near surfaced approaches to culvert ends?
m No Yes If"yes" identify location(s), describe outfall design treatment(s):
c
c
0
0
a) Is scour/erosion protection provided to ensure long term stability of culvert structural
components, and surfacing at culvert ends? Yes No If"no" Identify
locations and provide justification(s):
Will 100-yr flow and spread of backwater be fully contained in street ROW, and/or
drainage easements/ ROW? Yes No if not, why not?
1 •
Do appreciable hydraulic effects of any culvert extend downstream or upstream to
neighboring land(s) not encompassed in subject property? No Yes If
"yes" describe location(s) and mitigation measures:
41
111 Are all culvert designs and materials in compliance with B-CS Tech. Specifications?
Yes No If not, explain in Special Design Section of this Part.
1
STORMWATER DESIGN GUIDELINES Page 21 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.13)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site) (continued)
Is a bridge included in plans for subject property project? X No Yes
If"yes" provide the following information.
• Name(s) and functional classification of the roadway(s)?
4110
What drainage way(s) is to be crossed?
•
C 4)
•
0)
CO
• A full report supporting all aspects of the proposed bridge(s) (structural, geotechnical,
• hydrologic, and hydraulic factors) must accompany this summary report. Is the report
provided? Yes No If"no" explain:
I • Is a Stormwater Provide a general description of planned techniques:
.>. Pollution Prevention construction entrance, erosion control silt fence, hay bales at
Plan (SW3P) pond discharge points
c� established for
project construction?
No X Yes
Special Designs— Non-Traditional Methods
Are any non-traditional methods (aquatic echosystems, wetland-type detention, natural stream
replication, BMPs for water quality, etc.) proposed for any aspect of subject property project?
X No Yes If"yes" list general type and location below.
Provide full report about the proposed special design(s) including rationale for use and
expected benefits. Report must substantiate that stormwater management objectives will not
be compromised, and that maintenance cost will not exceed those of traditional design
solution(s). Is report provided? Yes _ No If"no" explain:
•
STORMWATER DESIGN GUIDELINES Page 22 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
•
•
• SECTION IX
• APPENDIX D - TECHNICAL DESIGN SUMMARY
• Part 4 — Drainage Concept and Design Parameters Continued (Page 4.14)
•
Stormwater Management Concept (continued)
• Within Or Serving Subject Property(Phase, or Site)(continued)
Special Designs— Deviation From B-CS Technical Specifications
• If any design(s) or material(s) of traditional runoff-handling facilities deviate from provisions of
B-CS Technical Specifications, check type facility(ies) and explain by specific detail element.
Detention elements Drain system elements Channel features
Culvert features Swales Ditches Inlets Outfalls
Valley gutters Bridges (explain in bridge report)
• In table below briefly identify specific element,justification for deviation(s).
Specific Detail Element Justification for Deviation (attach additional sheets if needed)
1)
2)
3)
4)
5)
Have elements been coordinated with the City Engineer or her/his designee? For each item
above provide"yes" or"no", action date, and staff name:
1)
2)
3)
4)
5)
Design Parameters
I ; Hydrology
Is a map(s) showing all Design Drainage Areas provided? X Yes No
Briefly summarize the range of applications made of the Rational Formula:
N/A. Rational Method can not be used for detention design per BCS Std. Design Guidelines.
What is the size and location of largest Design Drainage Area to which the Rational Formula
has been applied? acres Location (or identifier):
STORMWATER DESIGN GUIDELINES Page 23 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.15)
Design Parameters (continued)
Hydrology(continued)
In making determinations for time of concentration, was segment analysis used?
No X Yes In approximately what percent of Design Drainage Areas? 100
As to intensity-duration-frequency and rain depth criteria for determining runoff flows, were any
criteria other than those provided in these Guidelines used? X No Yes If"yes"
identify type of data, source(s), and where applied:
For each of the stormwater management features listed below identify the storm return
frequencies (year) analyzed (or checked), and that used as the basis for design.
Feature Analysis Year(s) Design Year
Storm drain system for arterial and collector streets
Storm drain system for local streets
Open channels
Swale/buried conduit combination in lieu of channel
•
Swales
Roadside ditches and culverts serving them
Detention facilities: spillway crest and its outfall 2, 10, 25, 50,& 100 100
Detention facilities: outlet and conveyance structure(s) 2, 10,25,50, & 100 2,10,25,50,&100
Detention facilities: volume when outlet plugged
• Culverts serving private drives or streets
•
Culverts serving public roadways
•
Bridges: provide in bridge report.
• Hydraulics
• What is the range of design flow velocities as outlined below?
• Design flow velocities; Gutters Conduit Culverts Swales Channels
•
•
Highest (feet per second)
Lowest (feet per second)
Streets and Storm Drain Systems Provide the summary information outlined below:
41 Roughness coefficients used: For street gutters:
For conduit type(s) Coefficients:
STORMWATER DESIGN GUIDELINES Page 24 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.16)
Design Parameters (continued)
Hydraulics (continued)
Street and Storm Drain Systems (continued)
For the following, are assumptions other than allowable per Guidelines?
Inlet coefficients? No Yes Head and friction losses No Yes
• Explain any"yes" answer:
S
In conduit is velocity generally increased in the downstream direction? Yes No
Are elevation drops provided at inlets, manholes, and junction boxes? Yes No
• Explain any"no" answers:
•
• Are hydraulic grade lines calculated and shown for design storm? Yes No
For 100-year flow conditions? Yes No Explain any "no" answers:
i1
What tailwater conditions were assumed at outfall point(s) of the storm drain system? Identify
I • each location and explain:
• Open Channels If a HEC analysis is utilized, does it follow Sec VI.F.5.a? Yes No
• Outside of straight sections, is flow regime within limits of sub-critical flow? Yes No
If"no" list locations and explain:
•
I
• Culverts If plan sheets do not provide the following for each culvert, describe it here.
• For each design discharge, will operation be outlet (barrel) control or inlet control?
•
S
Entrance, friction and exit losses:
•
•
S
Bridges Provide all in bridge report
•
•
S
• STORMWATER DESIGN GUIDELINES Page 25 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.17)
Design Parameters (continued)
Computer Software
What computer software has been used in the analysis and assessment of stormwater
management needs and/or the development of facility designs proposed for subject property
project? List them below, being sure to identify the software name and version, the date of the
version, any applicable patches and the publisher
Part 5 — Plans and Specifications
Requirements for submittal of construction drawings and specifications do not differ due to use of a
Technical Design Summary Report. See Section III, Paragraph C3.
Part 6 — Conclusions and Attestation
Conclusions
Add any concluding information here:
Attestation
Provide attestation to the accuracy and completeness of the foregoing 6 Parts of this Technical
Design Summary Drainage Report by signing and sealing below.
"This report (plan) for the drainage design of the development named in Part B was prepared
by me (or under my supervision) in accordance with provisions of the Bryan/College Station
Unified Drainage Design Guidelines for the owners of the property. All licenses and permits
required by any and all state and federal regulatory agencies for the proposed drainage
improvements have been issued or fall under applicable general permit424.4"NNsu
' (Affix Seal) " t..F•TE..tut 1k
Licensed Professional Engineer �•„*,.: •• ••A” •:�HOMpS
......
State of Texas PE No. 98398 tt '•., UC,ENgta�:' i
t1A �SStONA -,��� \
STORMWATER DESIGN GUIDELINES Page 26 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
May 29, 2014
Gessner Engineering Job No. 11-0355
Prepared for:
Moreau Family Investments, Ltd.
• Mr. Chuck Moreau
• In Accordance with:
• Unified Storm water Design Guidelines
• City of Bryan/City of College Station
•
•
•
•
• Prepared by:
• GESSNER ENGINEERING, LLC
• College Station, Texas
•
•
•
•
• DRAINAGE DESIGN REPORT
• Brazos Valley Floor and Design
• College Station, Texas
•
•
•
•
•
•
•
2
May 29, 2014
Mr. Alan Gibbs, P.E.
City Engineer
City of College Station
1101 Texas Avenue
College Station,TX 77840
Re: Storm Water Drainage Study
Brazos Valley Floor and Design
12900 Old Wellborn Road
• College Station,Texas
• Gessner Engineering Job No.: 11-0355
• Dear Mr. Gibbs,
•
• This report conveys the results of the storm water drainage study conducted by Gessner
• Engineering for the proposed redevelopment of Brazos Valley Floor and Design, College Station,
Texas. Gessner Engineering believes that all information contained in this report is valid. Please
contact us if you have any questions or if we can be of further assistance.
•
• This report for the drainage design for Brazos Valley Floor and Design was
prepared by Gessner Engineering in accordance with provisions of the
• Bryan/College Station Unified Stormwater Design Guidelines for the owner of the
property.
411
Sincerely,
GESSNER ENGINEERING LLC, F-7451
„-�PZ ** t'��7�
Iq.‘t
qir , ! *
# ;
lMELISSA P. THOMAS
Melissa P. Thomas, P.E.
;t , 98398
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I . Joshua B. Van Wie, E.I.T., M.S.
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TABLE OF CONTENTS
EXECUTIVE SUMMARY 4
INTRODUCTION 4
CALCULATIONS 5
Time of Concentration 5
Unit Hydrograph 6
Reach Routing 6
Peak Runoff Flow 6
Peak Post-Developed Runoff Flow 7
CONCLUSION 7
APPENDIX
Appendix A: General Location Map
Appendix B: FEMA 100 Year Floodplain Map
Appendix C: Drainage Area Map and Calculations
Appendix D: Hydrographs
Appendix E: HEC-HMS Calculations
Appendix F: Technical Design Summary
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• EXECUTIVE SUMMARY
This storm water drainage report is submitted to the City of College Station, Texas for review on
April 2, 2014 by Melissa P. Thomas, P.E. of Gessner Engineering, located at 2501 Ashford Drive,
Suite 102, College Station, Texas 77840.
The proposed project consists of the demolition of the asphalt pavement serving the current
• building and construction of a 15,000 square foot (SF) warehouse and associated new concrete
• parking. The site will be served by two detention ponds in series. The total area of construction is
• approximately 2.38 acres. The subject site currently contains a 2,434 SF retail building to remain, a
1,963 sf metal canopy, a 1,112 sf metal awning, and a 24,631 SF of existing parking lot and
hardscape all to be removed.
The site is located directly northwest of the intersection of Old Wellborn Road and N. Graham
Road. The site is located in the Hopes Creek watershed. The site is not located in the FEMA 100
year flood plain, as shown by FIRM number 48041C0310E. This firmette is included as Appendix B.
• Runoff from the overall drainage area generally flows south until reaching N. Graham Road. Water
• then flows southwest through a small drainage ditch along N. Graham Road until reaching a
• tributary of Hopes Creek. Runoff from the subject site reaches N. Graham Road by sheet flow and
• shallow concentrated flow through a small channel in the center of the property. Runoff from the
• Carpet Outlet site is stored in a detention pond in the southern corner of the property and
discharged to flow across the property to the southwest of both lots until reaching N. Graham
Road. Under existing conditions, the total flow exiting the lot and reaching the drainage ditch on N.
• Graham Road is 16.3 cubic feet per second (cfs) at the peak of the 100 year, Type III, 24 hour storm
• event. After development, runoff will be stored in a series of two detention ponds on the subject
• property and discharged at the southern corner of the property directly into the ditch along N.
Graham Road. Under proposed conditions the flow into the drainage ditch is 15.7 cfs, at the same
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storm event. Additionally, a small portion of the two driveways along the north property line
discharges 0.2 cfs onto the existing Brazos Valley Floor and Design site at the same storm event.
The total peak flow of the subject tract under the proposed conditions is 15.9 cfs.
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The post-developed peak flow is below the pre-developed peak at the 100 year storm event and
does not create any issues for downstream properties.
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• INTRODUCTION
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• This storm water drainage report is intended to determine the required detention to match pre-
• developed storm runoff conditions for the proposed Brazos Valley Floor and Design. The entire
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i drainage area contributes to the drainage ditch along N. Graham Road. The point of contribution
to the ditch was used for both pre-developed and post-developed conditions analysis.
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• Drainage Calculations for this site were prepared according to the National Resource Conservation
• Method as detailed in Technical Release 55 (TR-55) published in June of 1986. Proposed
improvements include a 15,000 SF building and 50,130 SF concrete pavement and approximately
8,140 SF of detention area. Curve numbers from TR-55 were used based on developed uses as
• described above. Pre-developed flows were calculated based on the existing development for the
• subject site and based on undeveloped conditions for the Carpet Outlet tract. The calculated pre-
developed and developed flows include the two (2), five (5), ten (10), twenty-five (25), fifty (50) and
one-hundred (100) year storms in accordance with the Bryan/College Station Unified Stormwater
• Design Guidelines.
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• CALCULATIONS
• Calculations were performed according to the USDA TR-55 and with the aid of HEC-HMS 3.5 by the
• U.S. Army Corps of Engineers. The output data from HEC-HMS has been provided as Appendix E.
Time of Concentration
4 The time of concentration (travel time) for each drainage area was estimated by summing the flow
4 time for each segment of travel. For sheet flow, travel time was estimated by Manning's Kinematic
4 equation:
0.007 x(nL)°8
/ r/ _ S p4 V"
2
tip
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Where:
tt = travel time (hours)
n = manning's roughness coefficient
L = flow length (feet)
S = slope (ft/ft)
P2 = 2-year, 24 hour rainfall (inches)
For shallow concentrated flow, the travel time was calculated from the flow velocity based on the
slope in the direction of flow. These velocities were taken from Table C-4 of the Bryan College
Station Unified Stormwater Design Guidelines.
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The computed times of concentration for each drainage area are included in Appendix E.
Computed values were increased to a minimum time of six (6) minutes as required, based on
Chapter 3 of TR-55 which limits the minimum Time of Concentration to 0.1 hour or six (6) minutes.
Unit Hydrograph
A generic unit hydrograph was computed by distributing the rainfall depths (Table 1) according to
the distribution factors for the NCRS Type III 24 hour storm. This hydrograph was then applied to
each subarea based on the curve number and time of concentration of that area.
Reach Routing
Hydrographs were routed from subareas to the outflow through the kinematic wave method. This
method allows for hydrographs to be translating with time, but not attenuating. The effects of
backwater flow and pressure flow in channels were neglected.
Peak Runoff Flow
Peak Runoff Flow from the site was determined based on the Type III 24 hour storm applied to
each drainage area. The depth-duration-intervals for each frequency are included in Table 1 below,
and were obtained from Table C-6 in the Unified Stormwater Design Guidelines. Curve Number
values (CN) were determined from Table C-7, Appendix C of the Unified Stormwater Design
Guidelines. Peak pre-developed flows for the subject site adjacent to N. Graham Road are included
in Table 1. Drainage areas and calculations are included on sheet C5.0 and C5.1, which are
attached in Appendix C.
Rainfall Depth (in),24-hr Pre-Developed Peak Flow
Frequency duration (cfs)
2 year 4.50 5.6
10 year 7.40 10.4
25 year 8.40 12.5
50 year 9.80 14.1
100 year 11.00 16.3
Table 1:Rainfall Depths and Resulting Flows
Peak Post-Developed Runoff Flow
The post-developed peak flows compared to the pre-developed peak flows are shown in Table 2
below for each storm event. Hydrographs for each storm event are included as Appendix D.
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• Pre-Developed Post-Developed Post-Developed Total Post-
Storm Peak Flow at Peak Flow at Peak Flow at Developed Flow
• Event Southwest Outlet Southwest Outlet North Outlet (cfs)
(cfs) (cfs) (cfs)
• 2 year 5.6 5.5 0.1 5.6
6 10 year 10.4 10.2 0.1 10.3
• 25 year 12.5 12.1 0.1 12.2
50 year 14.1 13.7 0.2 13.9
• 100 year 16.3 15.7 0.2 15.9
eTable 2:Pre-Developed and Post-Developed Site Outflows
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I CONCLUSION
•
it Based on visual evidence, engineering drainage calculations and sound engineering judgment,
0 Gessner Engineering believes that the post-development flows are reduced for the two (2), ten
(10), twenty-five (25), fifty (50), and one hundred (100) year design storms for this development,
and do not create adverse impacts to downstream properties.
Work Certification
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"This report for the drainage design of the Brazos Valley Floor & Design was prepared by me in
• accordance with the provisions of the Bryan/College Station Unified Drainage Guidelines for the
owners of the property. All licenses and permits required by any and all state and federal
IL regulatory agencies for the proposed drainage improvements have been issued."
•
• r:4,At OF TF i ji r
• j' Y"riii-
, Licensed Professional Engineer
MELISSA P. THOMAS 1
• + State of Texas No. 98398
e�iii. 98398
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• APPENDIX A:
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• General Location Map
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• APPENDIX B:
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• FEMA 100 Year Floodplain Map
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• Drainage Area Maps and Calculations
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APPENDIX D:
Hydrographs
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Subbasin"PRE-AREA 1"Results for Run "PRE- 2 YEAR"
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Legend(Compute lime:07Apr2014,15:22:31)
. 111.1 Run:PRE-2 YEAR Element:PRE-AREA 1 Result:Precipitation Run:PRE-2 YEAR Element:PRE-AREA 1 Result:Precipitation Loss
Run:PRE-2 YEAR Element:PRE-AREA 1 Result:Outflow — Run.PRE-2 YEAR Element:PRE-AREA 1 Result:Baseflow
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Subbasin"PRE-AREA 1"Results for Run"PRE- 10 YEAR"
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Run:PRE-10 YEAR Element:PRE-AREA 1 Result:Precipitation Run:PRE-10 YEAR Element:PRE-AREA 1 Recut Precipitation Loss
• Run:PRE-10 YEAR Element:PRE-AREA 1 Result:Outflow ——- Run:PRE-10 YEAR ElementPRE-AREA 1 Resutt:Baseflaw
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Subbasin"PRE-AREA 1"Results for Run"PRE-25 YEAR"
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Legend(Compute Time:07Apr2014,15:22:31)
imman Run:PRE-25 YEAR Element:PRE-AREA 1 Resutt:Precipdation Run:PRE-25 YEAR Element:PRE-AREA 1 Result:Precipdation Loss
Run:PRE-25 YEAR Element:PRE-AREA 1 Result Outflow ——- Run:PRE-25 YEAR Element:PRE-AREA 1 ResutBaseflow
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Subbasin"PRE-AREA 1"Results for Run"PRE-50 YEAR"
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Run:PRE-50 YEAR Element:PRE-AREA 1 Result:Precipitation Run:PRE-50 YEAR Element:PRE-AREA 1 Result:Precipitation Loss
Run:PRE-50 YEAR Element:PRE-AREA 1 Result:Outflow ——— Run:PRE-50 YEAR Element:PRE-AREA 1 Resutt:Baseflow
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Subbasin"PRE-AREA 1"Results for Run"PRE- 100 YEAR"
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Legend(Compute Time:07Apr2014, 15:22:30)
Run:PRE-100 YEAR Element:PRE-AREA 1 Result:Precipitetion Imilm Run:PRE-100 YEAR Element:PRE-AREA 1 Result:Precipitatian Loss
Run:PRE-100 YEAR Element:PRE-AREA 1 Resutt:Outflow ——— Run:PRE-100 YEAR Element PRE-AREA 1 Resuf:Baseflow
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Junction"SOUTWEST OUTLET"Results for Run"POST- 2 YEAR"
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Run:POST-2 YEAR Element:SOUNVEST OUTLET Resutt:Outflow ——— Run:POST-2 YEAR Element:REACH-2 Result:Outflow
Run:POST-2 YEAR Element:POST-AREA 3 Resutt:Outflow ---• Run:POST-2 YEAR Element REACH-1 Result:Outflow
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Junction"SOUTWEST OUTLET"Results for Run"POST- 10 YEAR"
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Run:POST-10 YEAR Element:SOUPNEST OUTLET Result:Outflow ——- Run:POST-10 YEAR Element:REACH-2 Result:Outflow
Run:POST-10 YEAR Element:POST-AREA 3 Result:Outflow --- Run:POST-10 YEAR Element:REACH-1 Result:Outflow
Run:POST-10 YEAR Element:POST-AREA 4 Result:Outflow
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Junction"SOUTWEST OUTLET"Results for Run"POST- 25 YEAR"
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01Jan2013
Legend(Compute Tme: 14Apr2014, 14:36:28)
Run:POST-25 YEAR Element:SOUPNEST OUTLET Resutt:Outflow ——— Run:POST-25 YEAR Element:REACH-2 Result:Outflow
Run:POST-25 YEAR Element:POST-AREA 3 Result:Outflow --- Run:POST-25 YEAR Element:REACH-1 Resutt:Outflow
—--— Run:POST-25 YEAR Element:POST-AREA 4 Result:Outflow
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Junction"SOUTWEST OUTLET"Results for Run"POST-50 YEAR"
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Legend(Compute Time: 14Apr2014,14:36:31)
Run:POST-50 YEAR Element:SOU1VEST OUTLET Result:Outflow ——— Run:POST-50 YEAR Element:REACH-2 Result:Outflow
Run:POST-50 YEAR Element:POST-AREA 3 Result:Outflow —-—• Run:POST-50 YEAR Element:REACH-1 Result:Outflow
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Junction"SOUTWEST OUTLET"Results for Run"POST- 100 YEAR"
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Legend(Compute Time: 14Apr2014,14:36:25)
• Run:POST-100 YEAR Element:SOUTWEST OUTLET Resutt:Outflow ——— Run:POST-100 YEAR Element:REACH-2 Result:Outflow
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• APPENDIX E:
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• HEC-HMS Calculations
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CPRE-AREA 1
Pre-Developed HEC-HMS Model
Project: 11-0355 Simulation Run: PRE -2 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 PRE
End of Run: 03Jan2013,00:00 Meteorologic Model: 2 YR
Compute Time: 18Mar2014, 11:31:25 Control Specifications:Control 1
Show Elements: IAD Elements °; Volume Units: 4,IN %y AC-FT Sorting: Hydrologic
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) (CFS) (IN)
[PRE_AREA 1 0.0037 5.6 01Jan2013, 12:16 3.19
Project: 11-0355 Simulation Run: PRE-10 YEAR
Start of Run: O lJan2013,00:00 Basin Model: 11-0355 PRE
End of Run: 03Jan2013,00:00 Meteorologic Model: 10 YR
Compute Time: 18Mar2014, 11:32:38 Control Specifications: Control 1
Show Elements: iAll Elements vt.,
3 Volume Units: a IN AC-FT Sorting: Hydrologic
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) (CFS) (IN)
PRE-AREA 1 0.0037 10.4 01Jan2013, 12:16 j 6.07
Project: 11-0355 Simulation Run: PRE-25 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 PRE
End of Run: 033an2013,00:00 Meteorologic Model: 25 YR
Compute Time: 18Mar2014, 11:32:58 Control Specifications: Control 1
Sho,A,Elements, A11 dements Volume Units: ,0 IN AC-FT Sorting: Hydrologic
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) I (CFS) (IN)
PRE-AREA 1 0.0037 12.5 01Jan2013, 12:16 7.34
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Project: 11-0355 Simulation Run: PRE-50 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 PRE
End of Run: 03Jan2013,00:00 Meteorologic Model: 50 YR
Compute lime: 18Mar2014, 11:34:27 Control Specifications:Control 1
Show Elements: « _ Volume Units: .o IN AC-FT Sorting: Hydrologic
Hydrologic Drainage Area Peak Discharge` Time of Peak Volume
Element (MI2) (CFS) (IN)
PRE-AREA 1 0.0037 I 14.1 01Jan2013, 12:16 3.32
Project: 11-0355 Simulation Run: PRE-100 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 PRE
End of Run: 03Jan2013,00:00 Meteorologic Model: 100 YR
Compute Time: 18Mar2014, 11:34:45 Control Specifications:Control 1
Show Elements: G All Elements j Volume Units: +a IN AC-FT Sorting: Hydrologic .]
Hydrologic Drainage Area Peak Discharge I Time of Peak Volume
Element (MI2) (CFS) (IN)
PRE-AREA 1 0.0037 16.3 01Jan2013, 12:16 9.70
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Project: 11-0355 Simulation Run: POST-2 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 POST
End of Run: 02Jan2013,00:02 Meteorologic Model: 2 YR
Compute Time: 14Apr2014, 14:36:29 Control Specifications: Control 1
Show Elements: All Elements , Volume Units: 0 IN AC-FT Sorting: Hydrologic .
Hydrologic[-----
Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) (CFS) (IN)
POST-AREA 5 0,0010470 j 2.2 '01Jan2013, 12:08 3.52
POND 2 0.0010470 1.0 01JanZ013, 12:24 3.52 _
Reach-2 0.0010470 1.0 01Jan2013, 12:24 3.52
POST-AREA 3 0.0013750 2,4 01Jan2013, 12:13 3.51
POST-AREA 6 r .000953 2.1 01Jan2013, 12:09 3.91
POND 1 .000953 1.7 01Jan2013, 12:14 3.91
Reach-1 .000953 1,7 013an2013, 12:15 3.91
POST-AREA 4 .000328 0.6 01Jan2013, 12:08 2.95
SOUTWEST OUTLET 0.0037030 5.5 013an2013, 12:14 3.57
POST-AREA 2 .00001733 I 0.0 01Jan2013, 12:07 4.26
POST-AREA 1 ( .00001679 0.0 01Jan2013, 12:07 4.26
NORTH OUTLET ( .00003412 ( 0.1 01Jan2013, 12:07 4.26
Project: 11-0355 Simulation Run:POST- 10 YEAR
Start of Run: OlJan2013,00:00 Basin Model: 11-0355 POST
End of Run: 02Jan2013,00:02 Meteorologic Model: 10 YR
Compute Time: 14Apr2014, 14:36:26 Control Specifications: Control 1
Show Elements All Elements , ; Volume Units: ,0 IN AC-FT Sorting: Hydrologic .
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) (CFS) (IN)
POST-AREA 5 0,0010470 3.9 01Jan2013, 12:08 6.46
POND 2 0.0010470 1.9 O1Jan2013, 12:22 6.46
Reach-2 0,0010470 1.9 01Jan2013, 12:22 6.46
POST-AREA 3 I 0.0013750 4.3 01Jan2013, 12:13 6.44
POST-AREA 6 I .000953 3.5 0llan2O13, 12:09 6.88
POND 1 .000953 3.2 OiJan2O13, 12:13 6.88
Reach-1 .000953 3.2 O1Jan2013, 12:14 6.88
'POST-AREA 4 .000328 1.2 01Jan2013, 12:07 5.78
SOUTWEST OUTLET 0.0037030 10.2 01Jan2O13, 12:13 6.50
POST-AREA 2 .00001733 0.1 01Jan2O13, 12:07 7.25
I
POST-AREA 1 .00001679 0.1 01Jan2013, 12:07 7.25
NORTH OUTLET .00003412 0.1 01Jan2O13, 12:07 7.25
0 Gessner Engineering
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Project: 11-0355 Simulation Run: POST-25 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 POST
End of Run: 02Jan2013,00:02 Meteorologic Model: 25 YR
Compute Time: 14Apr2014, 14:36:28 Control Specifications: Control 1
Show Elements: -, .:: Volume Units: a IN AC-FT Sorting: Hydrologic .
Hydrologic ...Drainage Area Peak Discharge Time of Peak Volume
I Element (MI2) (CFS) (IN)
POST-AREA 5 0.0010470 4.6 OlJan2O 13, 12:08 7.74
POND 2 0.0010470 2.3 01Jan2013, 12:21 7.74
Reach-2 0.0010470 2.3 OlJan2013, 12:21 7.74
POST-AREA 3 0.0013750 5.1 01Jan2013, 12:13 7.72
POST-AREA 6 .000953 4.2 1O 1Jan2013, 12:09 8.18
POND 1 .000953 3.8 101Jan2013, 12:12 8.18
Reach-1 .000953 3.8 01Jan2013, 12:13 8.17
POST-AREA 4 .000328 1.4 01Jan2013, 12:07 7.04
SOUTWEST OUTLET 0.0037030 12.1 O lJan2013, 12:13 7.78
POST-AREA 2 .00001733 0.1 O lJan2O13, 12:07 8.55
POST-AREA 1 .00001679 0.1 OlJan2013, 12:07 8.55
NORTH OUTLET .00003412 0.2 0llan2013, 12:07 8.55
Project: 11-0355 Simulation Run: POST-50 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 POST
End of Run: 02Jan2013,00:02 Meteorologic Model: 50 YR
Compute Time: 14Apr2014, 14:36:31 Control Specifications: Control 1
Show Elements: All Elements Volume Units: 4 IN AC-FT Sorting: Hydrologic .
Hydrologic Drainage Area Peak Discharge Time of Peak Volume
Element (MI2) (CFS) (IN)
POST-AREA 5 0.0010470 ' 5.2 0llan2013, 12:08 8.73
POND 2 0.0010470 2.6 0lJan2013, 12:21 8.73
Reach-2 0.0010470 2.6 101Jan2013, 12:21 8.73
POST-AREA 3 0.0013750 5.8 01Jan2013, 12:13 8.71
POST-AREA 6 .000953 4.6 OlJan2013, 12:09 9.17
POND 1 .000953 4.3 OtJan2O13, 12:12 9.17
Reach-1 .000953 4.3 OlJan2013, 12:13 9.17
POST-AREA 4 .000328 1.6 01Jan2013, 12:07 8.01
SOUTWEssT OUTLET 0.0037030 13.7 01Jan2013, 12:13 8.77
POST-AREA 2 .00001733 0.1 01Jan2013, 12:07 9.55
POST-AREA 1 .00001679 0.1 01Jan2013, 12:07 9.55
NORTH OUTLET .00003412 0.2 101Jan2013, 12:07 9.55
411
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Project: 11-0355 Simulation Run: POST- 100 YEAR
Start of Run: 01Jan2013,00:00 Basin Model: 11-0355 POST
End of Run: 02Jan2013,00:02 Meteorologic Model: 100 YR
Compute Time: 14Apr2014, 14:36:25 Control Spedfications:Control 1
Show Elements: All Elements Volume Units: izi IN AC-FT Sorting: Hydrologic .
HydrologicDrainage Area Peak Discharge Time of Peak Volume
Element (M12) (CFS) (IN)
POST-AREA 5 0.0010470 6.0 01Jan2013, 12:08 10.12
POND 2 0.0010470 3.0 01Jan2013, 12:21 10.12
Reach-2 0.0010470 3.0 01Jan2013, 12:21 10.12
POST-AREA 3 0.0013750 6.6 01Jan2013, 12:13 10.10
POST-AREA 6 .000953 5.3 01Jan2013, 12:09 10.57
POND 1 .000953 4.9 01Jan2013, 12:12 10.57
Reach-1 .000953 4.9 101Jan2013, 12:13 10.56
POST-AREA 4 .000328 1.8 01Jan2013, 12:07 9.38
SOUTWEST OUTLET 0.0037030 15.7 0llan2013, 12:13 10.16
POST-AREA 2 .00001733 0.1 01Jan2013, 12:07 10.95
POST-AREA 1 .00001679 0.1 01Jan2013, 12:07 10.95
NORTH OUTLET .00003412 0.2 101Jan2013, 12:07 10.95
0 Gessner Engineering
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• APPENDIX F:
• Technical Design Summary
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Gessner Engineering
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SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 2 — Project Administration Start (Page 2.1)
Engineering and Design Professionals Information
Engineering Firm Name and Address: Jurisdiction
Gessner Engineering City: Bryan
2501 Ashford Drive Suite 102 X College Station
College Station, TX 77840 Date of Submittal:
Lead Engineer's Name and Contact Info.(phone, e-mail, fax): Other:
Jeremy N. Peters, 979-680-8840,jpeters@gessnerengineering.com
gessnerengineering.com
Supporting Engineering /Consulting Firm(s): Other contacts:
Developer/Owner/Applicant Information
Developer/Applicant Name and Address: Phone and e-mail:
Chuck Moreau - Moreau Family Investments, Ltd. 764-4084
1834 Harris Drive chuck@bvcarpetoutlet.com
College Station, TX 77845
Property Owner(s) if not Developer/ Applicant (&address): Phone and e-mail:
Project Identification
•
Development Name: Brazos Valley Floor and Design
Is subject property a site project, a single-phase subdivision, or part of a multi-phase subdivision?
Site Project If multi-phase, subject property is phase of
Legal description of subject property (phase) or Project Area:
• (see Section II, Paragraph B-3a)
• Lot 10, Block 1, Rock Prairie West Business Park
•
•
• If subject property (phase) is second or later phase of a project, describe general status of all
. earlier phases. For most recent earlier phase Include submittal and review dates.
•
General Location of Project Area, or subject property (phase):
Rock Prairie&Wellborn
In City Limits? Extraterritorial Jurisdiction (acreage):
Bryan: acres. Bryan: College Station:
College Station: 2.38 acres. Acreage Outside ETJ:
STORMWATER DESIGN GUIDELINES Page 3 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 2 — Project Administration Continued (page 2.2)
Project Identification (continued)
Roadways abutting or within Project Area or Abutting tracts, platted land, or built
subject property: developments:
N. Graham Rd., Old Wellborn Rd.
Named Regulatory Watercourse(s) &Watershed(s): Tributary Basin(s):
Plat Information For Project or Subject Property (or Phase)
Preliminary Plat File#: Final Plat File#: Date:
Name: Status and Vol/Pg:
If two plats, second name: File #:
Status: Date:
Zoning Information For Project or Subject Property (or Phase)
Zoning Type: PPD gAlsin or Proposed? Case Code:
Case Date Status:
Zoning Type: Existing or Proposed? Case Code:
Case Date Status:
Stormwater Management Planning For Project or Subject Property (or Phase)
Planning Conference(s) & Date(s): Participants:
Preliminary Report Required? No Submittal Date Review Date
Review Comments Addressed? Yes No In Writing? When?
Compliance With Preliminary Drainage Report. Briefly describe (or attach documentation
explaining) any deviation(s)from provisions of Preliminary Drainage Report, if any.
STORMWATER DESIGN GUIDELINES Page 4 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 2 — Project Administration Continued (page 2.3)
Coordination For Project or Subject Property (or Phase)
Note: For any Coordination of stormwater matters indicated below, attach documentation
describing and substantiating any agreements, understandings, contracts, or approvals.
Coordination
Dept. Contact: Date: Subject:
With Other
Departments of
Jurisdiction
City (Bryan or
College Station)
Coordination With Summarize need(s) & actions taken (include contacts & dates):
Non-jurisdiction
City Needed?
Yes No X
Coordination with Summarize need(s) & actions taken (include contacts & dates):
Brazos County
Needed?
Yes No X
Coordination with Summarize need(s) &actions taken (include contacts &dates):
TxDOT Needed?
Yes No X
Coordination with Summarize need(s) & actions taken (include contacts &dates):
TAMUS Needed?
Yes No X
Permits For Project or Subject Property (or Phase)
As to stormwater management, are permits required for the proposed work from any of the entities
listed below? If so, summarize status of efforts toward that objective in spaces below.
Entity Permitted or Status of Actionsinclude dates
Approved ? Actions (include
US Army Crops of
Engineers
No X Yes
US Environmental
Protection Agency
No X Yes
Texas Commission on
Environmental Quality
No X Yes
Brazos River
Authority
No X Yes
STORMWATER DESIGN GUIDELINES Page 5 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Start (Page 3.1)
Nature and Scope of Proposed Work
Existing: Land proposed for development currently used, including extent of impervious cover?
Site
X Redevelopment of one platted lot, or two or more adjoining platted lots.
Development Building on a single platted lot of undeveloped land.
Project Building on two or more platted adjoining lots of undeveloped land.
(select all Building on a single lot, or adjoining lots, where proposed plat will not form
applicable) a new street (but may include ROW dedication to existing streets).
Other (explain):
Subdivision Construction of streets and utilities to serve one or more platted lots.
Development Construction of streets and utilities to serve one or more proposed lots on
Project lands represented by pending plats.
Site projects: building use(s), approximate floor space, impervious cover ratio.
Describe Subdivisions: number of lots by general type of use, linear feet of streets and
Nature and drainage easements or ROW.
Size of Construction of new parking lot for existing building and construction of new
Proposed 12,000 SF warehouse
Project
Is any work planned on land that is not platted If yes, explain:
or on land for which platting is not pending?
X No Yes
FEMA Floodplains
Is any part of subject property abutting a Named Regulatory Watercourse No X Yes
(Section II, Paragraph B1) or a tributary thereof?
Is any part of subject property in floodplain No X Yes Rate Map
area of a FEMA-regulated watercourse?
Encroachment(s) Encroachment purpose(s): Building site(s) Road crossing(s)
into Floodplain
areas planned? Utility crossing(s) Other (explain):
No X
Yes
If floodplain areas not shown on Rate Maps, has work been done toward amending the FEMA-
approved Flood Study to define allowable encroachments in proposed areas? Explain.
STORMWATER DESIGN GUIDELINES Page 6 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
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SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Continued (Page 3.2)
•
Hydrologic Attributes of Subject Property (or Phase)
• Has an earlier hydrologic analysis been done for larger area including subject property?
Yes Reference the study (& date) here, and attach copy if not already in City files.
•
Is the stormwater management plan for the property in substantial conformance with the
earlier study? Yes No If not, explain how it differs.
IrNo If subject property is not part of multi-phase project, describe stormwater management
X plan for the property in Part 4.
If property is part of multi-phase project, provide overview of stormwater management plan
for Project Area here. In Part 4 describe how plan for subject property will comply
rtherewith.
Do existing topographic features on subject property store or detain runoff? X No Yes
Describe them (include approximate size, volume, outfall, model, etc).
I
Any known drainage or flooding problems in areas near subject property? X No Yes
Identify:
Based on location of study property in a watershed, is Type 1 Detention (flood control) needed?
(see Table B-1 in Appendix B)
X Detention is required. Need must be evaluated. Detention not required.
What decision has been reached? By whom?
If the need for How was determination made?
Type 1 Detention
must be evaluated:
STORMWATER DESIGN GUIDELINES Page 7 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Continued (Page 3.3)
Hydrologic Attributes of Subject Property (or Phase) (continued)
Does subject property straddle a Watershed or Basin divide? X No Yes If yes,
describe splits below. In Part 4 describe design concept for handling this.
Watershed or Basin Larger acreage Lesser acreage
Above-Project Areas(Section II, Paragraph B3-a)
Does Project Area (project or phase) receive runoff from upland areas? X No Yes
Size(s) of area(s) in acres: 1) 2) 3) 4)
Flow Characteristics (each instance) (overland sheet, shallow concentrated, recognizable
concentrated section(s), small creek (non-regulatory), regulatory Watercourse or tributary);
Flow determination: Outline hydrologic methods and assumptions:
+rr
• Does storm runoff drain from public easements or ROW onto or across subject property?
No Yes If yes, describe facilities in easement or ROW:
•
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• Are changes in runoff characteristics subject to change in future? Explain
•
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• Conveyance Pathways (Section II, Paragraph C2)
Must runoff from study property drain across lower properties before reaching a Regulatory
• Watercourse or tributary? X No Yes
• Describe length and characteristics of each conveyance pathway(s). Include ownership of
• property(ies).
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• STORMWATER DESIGN GUIDELINES Page 8 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 3 — Property Characteristics Continued (Page 3.4)
Hydrologic Attributes of Subject Property (or Phase) (continued)
Conveyance Pathways (continued)
Do drainage If yes, for what part of length? % Created by? plat, or
easements instrument. If instrument(s), describe their provisions.
exist for any
part of
pathway(s)?
X No
Yes
Where runoff must cross lower properties, describe characteristics of abutting lower
property(ies). (Existing watercourses? Easement or Consent aquired?)
Pathway
Areas
•
•
Describe any built or improved drainage facilities existing near the property(culverts,
bridges, lined channels, buried conduit, swales, detention ponds, etc).
• Detention pond on adjacent property.
•
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Nearby
Drainage
Facilities Do any of these have hydrologic or hydraulic influence on proposed stormwater
• design? X No Yes If yes, explain:
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C
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C
STORMWATER DESIGN GUIDELINES Page 9 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Start (Page 4.1)
Stormwater Management Concept
Discharge(s) From Upland Area(s)
If runoff is to be received from upland areas, what design drainage features will be used to
accommodate it and insure it is not blocked by future development? Describe for each area,
flow section, or discharge point.
Discharge(s)To Lower Property(ies) (Section II, Paragraph El)
Does project include drainage features (existing or future) proposed to become public via
platting? X No Yes Separate Instrument? X No Yes
Per Guidelines reference above, how will Establishing Easements (Scenario 1)
runoff be discharged to neighboring X Pre-development Release (Scenario 2)
property(ies)? Combination of the two Scenarios
Scenario 1: If easements are proposed, describe where needed, and provide status of actions
on each. (Attached Exhibit#
Scenario 2: Provide general description of how release(s)will be managed to pre-development
conditions (detention, sheet flow, partially concentrated, etc.). (Attached Exhibit#
detention
Combination: If combination is proposed, explain how discharge will differ from pre-
development conditions at the property line for each area (or point)of release.
If Scenario 2, or Combination are to be used, has proposed design been coordinated with
owner(s)of receiving property(ies)? No Yes Explain and provide
documentation.
STORMWATER DESIGN GUIDELINES Page 10 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.2)
Stormwater Management Concept (continued)
Within Project Area Of Multi-Phase Project
Identify gaining Basins or Watersheds and acres shifting:
Will project result
in shifting runoff
between Basins or
between What design and mitigation is used to compensate for increased runoff
Watersheds? from gaining basin or watershed?
X No
Yes
How will runoff from Project 1. With facility(ies) involving other development projects.
Area be mitigated to pre- 2. X Establishing features to serve overall Project Area.
development conditions?
Select any or all of 1, 2, 3. On phase (or site) project basis within Project Area.
and/or 3, and explain below.
1. Shared facility (type &location of facility; design drainage area served; relationship to size of
Project Area): (Attached Exhibit#
2. For Overall Project Area (type& location of facilities): (Attached Exhibit#
Two detention ponds;one located to the southwest of the proposed building
and one to the northwest of the building.
3. By phase (or site) project: Describe planned mitigation measures for phases (or sites) in
subsequent questions of this Part.
Are aquatic echosystems proposed? x No Yes In which phase(s) or
project(s)?
a> u,
} Are other Best Management Practices for reducing stormwater pollutants proposed?
co
X No Yes Summarize type of BMP and extent of use:
a) o
Z
(-)0 If design of any runoff-handling facilities deviate from provisions of B-CS Technical
X Specifications, check type facility(ies) and explain in later questions.
co Detention elements Conduit elements Channel features
Swales Ditches Inlets Valley gutters Outfalls
Culvert features Bridges Other
STORMWATER DESIGN GUIDELINES Page 11 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.3)
Stormwater Management Concept (continued)
Within Project Area Of Multi-Phase Project(continued)
Will Project Area include bridge(s) or culvert(s)? No X Yes Identify type and
general size and In which phase(s).
Culvert under drives at NW and SW of the Proposed Building.
If detention/retention serves (will serve)overall Project Area, describe how it relates to subject
phase or site project (physical location, conveyance pathway(s), construction sequence):
Property is served by two detention ponds;one to the NW and one to the SW of the proposed building.
Both ponds discharge to SW of site.
Within Or Serving Subject Property(Phase, or Site)
If property part of larger Project Area, is design in substantial conformance with earlier analysis
and report for larger area? Yes No, then summarize the difference(s):
Identify whether each of the types of drainage features listed below are included, extent of use,
and general characteristics.
Typical shape? Surfaces?
r
a
g Steepest side slopes: Usual front slopes: Usual back slopes:
a)
O Flow line slopes: least Typical distance from travelway:
a• 0
typical greatest (Attached Exhibit#
cn z
2 c)
x Are longitudinal culvert ends in compliance with B-CS Standard Specifications?
Yes No, then explain:
At intersections or otherwise, do valley gutters cross arterial or collector streets?
m. No Yes If yes explain:
U• -a
L
w m Are valley gutters proposed to cross any street away from an intersection?
LI?• 3 o No Yes Explain: (number of locations?)
L a�z
E
Q
6
STORMWATER DESIGN GUIDELINES Page 12 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.4)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
Gutter line slopes: Least Usual Greatest
Are inlets recessed on arterial and collector streets? Yes No If"no",
identify where and why.
Will inlets capture 10-year design stormflow to prevent flooding of intersections (arterial
with arterial or collector)? Yes No If no, explain where and why not.
�.
a)
Will inlet size and placement prevent exceeding allowable water spread for 10-year
C13 design storm throughout site (or phase)? Yes No If no, explain.
0)
S Sag curves: Are inlets placed at low points? Yes No Are inlets and
E conduit sized to prevent 100-year stormflow from ponding at greater than 24 inches?
o Yes No Explain "no" answers.
U)
iv
a�
in
Will 100-yr stormflow be contained in combination of ROW and buried conduit on
whole length of all streets? Yes No If no, describe where and why.
Do designs for curb, gutter, and inlets comply with B-CS Technical Specifications?
Yes No If not, describe difference(s) and attach justification.
Are any 12-inch laterals used? No Yes Identify length(s) and where
used.
a Pipe runs between systemcn Typical Longest
• } access points (feet):
aa)) Are junction boxes used at each bend? Yes No If not, explain where
and why.
cnLZ
° x Are downstream soffits at or below upstream soffits? Least amount that hydraulic
• Yes No If not, explain where and why: grade line is below gutter line
(system-wide):
STORMWATER DESIGN GUIDELINES Page 13 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4 — Drainage Concept and Design Parameters Continued (Page 4.5)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site)(continued)
Describe watercourse(s), or system(s) receiving system discharge(s) below
(include design discharge velocity, and angle between converging flow lines).
owU
1) Watercourse (or system), velocity, and angle?
• E 2) Watercourse (or system), velocity, and angle?
c• o
c o
oo c
aa) E m 3)Watercourse (or system), velocity, and angle?
>. �'
c 0
o
-
E m For each outfall above, what measures are taken to prevent erosion or scour of
o s receiving and all facilities at juncture?
0 1)
a
2)
m
0 3)
Are swale(s) situated along property lines between properties? No Yes
Number of instances: For each instance answer the following questions.
Surface treatments (including low-flow flumes if any):
a)
v, u) Flow line slopes (minimum and maximum):
Z Outfall characteristics for each (velocity, convergent angle, &end treatment).
x
a)
Will 100-year design storm runoff be contained within easement(s) or platted drainage
ROW in all instances? Yes No If"no" explain:
STORMWATER DESIGN GUIDELINES Page 14 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.6)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site)(continued)
Are roadside ditches used? X No Yes If so, provide the following:
sIs 25-year flow contained with 6 inches of freeboard throughout ? Yes No
Are top of banks separated from road shoulders 2 feet or more? Yes No
E Are all ditch sections trapezoidal and at least 1.5 feet deep? Yes No
a)
70
Fz For any"no"answers provide location(s)and explain:
0
0
cc
If conduit is beneath a swale, provide the following information (each instance).
Instance 1 Describe general location, approximate length:
Is 100-year design flow contained in conduit/swale combination? Yes No
If "no" explain:
U)
a)
U
o a Space for 100-year storm flow? ROW Easement Width
z c Swale Surface type, minimum Conduit Type and size, minimum and maximum
i H
c and maximum slopes: slopes, design storm:
0
vi a
a� m Inlets Describe how conduit is loaded (from streets/storm drains, inlets by type):
c
c c
c0 m
r
o
c O
0 o Access Describe how maintenance access is provided (to swale, into conduit):
.8 m
E
0
w o
c
.5 m Instance 2 Describe general location, approximate length:
E
m m
N
z
0
c 72 Is 100-year design flow contained in conduit/swale combination? Yes No
° ` If "no" explain:
ri o.
C
E � Space for 100-year storm flow? ROW Easement Width
o c
O Swale Surface type, minimum Conduit Type and size, minimum and maximum
a�
a and maximum slopes: slopes, design storm:
C co
o 0-
Inlets Describe how conduit is loaded (from streets/storm drains, inlets by type):
a)
To c
°
m
Q Access Describe how maintenance access is provided (to swale, into conduit):
STORMWATER DESIGN GUIDELINES Page 15 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.7)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site)(continued)
If"yes" provide the following information for each instance:
Instance 1 Describe general location, approximate length, surfacing:
c
E Q
o w
L
• vi Is 100-year design flow contained in swale? Yes No Is swale wholly
>_ within drainage ROW? Yes No Explain "no" answers:
a)
Access Describe how maintenance access is provide:
o
z
-o x
Instance 2 Describe general location, approximate length, surfacing:
a)
•
.5 (1)
o E
2 Is 100-year design flow contained in swale? Yes No Is swale wholly
m °' within drainage ROW? Yes No Explain "no" answers:
0
3 �
> Access Describe how maintenance access is provided:
U_
0
a
Instance 3, 4, etc. If swales are used in more than two instances, attach sheet
providing all above information for each instance.
"New" channels: Will any area(s) of concentrated flow be channelized (deepened,
widened, or straightened) or otherwise altered? No Yes If only slightly
shaped, see "Swales" in this Part. If creating side banks, provide information below.
m .c Will design replicate natural channel? Yes No If"no", for each instance
o a describe section shape & area, flow line slope (min. & max.), surfaces, and 100-year
w design flow, and amount of freeboard:
• Instance 1:
tn
m
C
m
E
a)
o Instance 2:
L
d
E
Z
p
c x Instance 3:
n3
0
STORMWATER DESIGN GUIDELINES Page 16 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.8)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site)(continued)
Existing channels (small creeks): Are these used? X No Yes
If"yes" provide the information below.
Will small creeks and their floodplains remain undisturbed? X Yes No How
many disturbance instances? Identify each planned location:
For each location, describe length and general type of proposed improvement
(including floodplain changes):
For each location, describe section shape & area, flow line slope (min. & max.),
surfaces, and 100-year design flow.
•
• a
a)
Watercourses (and tributaries): Aside from fringe changes, are Regulatory
• Watercourses proposed to be altered? X No Yes Explain below.
• m Submit full report describing proposed changes to Regulatory Watercourses. Address
existing and proposed section size and shape, surfaces, alignment, flow line changes,
•
> length affected, and capacity, and provide full documentation of analysis procedures
a and data. Is full report submitted? Yes No If"no" explain:
• E
• m
c
•
U
All Proposed Channel Work: For all proposed channel work, provide information
• requested in next three boxes.
• If design is to replicate natural channel, identify location and length here, and describe
. design in Special Design section of this Part of Report.
11100
Will 100-year flow be contained with one foot of freeboard? Yes No If
• not, identify location and explain:
Ity
Are ROW/easements sized to contain channel and required maintenance space?
Yes No If not, identify location(s) and explain:
•
C
0
411 STORMWATER DESIGN GUIDELINES Page 17 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
• Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.9)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site)(continued)
How many facilities for subject property project? 2 For each provide info. below.
For each dry-type facilitiy: Facility 1 POND 1 Facility 2POND 2
Acres served &design volume+ 10% 0.61 ac 0.061 ac-ft 0.67 ac 0.165 ac-ft
100-yr volume:free flow& plugged 0.028ac-ft 0.055 ac-ft 0.61 0.15 ac-ft
Design discharge (10 yr&25 yr) 3.2 cfs 3.8 cfs 1.9 cfs 2.3 cfs
Spillway crest at 100-yr WSE? x yes no x yes no
Berms 6 inches above plugged WSE? x yes no x yes no
Explain any"no"answers:
U,
a)
>-
For each facility what is 25-yr design Q, and design of outlet structure?
Facility 1: 3.8 cfs
0
z Facility 2: 2.3 cfs
• Do outlets and spillways discharge into a public facility in easement or ROW?
• Facility 1: X Yes No Facility 2: X Yes No
a) If"no"explain:
u)
g o
a
0
• o_ For each, what is velocity of 25-yr design discharge at outlet? &at spillway?
• a) Facility 1: & 4.75 ft/sec Facility 2: 13.22 ft/sec & 4.38 ft/sec
Are energy dissipation measures used? No x Yes Describe type and
IIILL location:
• o Riprap at discharge points
• a
m
Cr)
lir D
ED_ For each, is spillway surface treatment other than concrete? Yes or no, and describe:
Q Facility 1: no,concrete weir
C Facility 2: no,concrete weir
Or For each, what measures are taken to prevent erosion or scour at receiving facility?
, Facility 1: Riprap
It Facility 2: Riprap
C If berms are used give heights, slopes and surface treatments of sides.
c Facility 1: Pond 1:no berms,grass side slopes 10%-25%
Pond 2:berm on plan north and west sides, 1.2'max. berm height,
Facility 2:grass side slopes 16%-23%
ar.
0
STORMWATER DESIGN GUIDELINES Page 18 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
C Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.10)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site)(continued)
Do structures comply with B-CS Specifications? Yes or no, and explain if"no":
Facility 1; yes
a)
• iFf
�i S Facility 2: yes
c
o c
o
U
a) --
oFor additional facilities provide all same information on a separate sheet.
Are parking areas to be used for detention? X No Yes What is
• maximum depth due to required design storm?
• Roadside Ditches:Will culverts serve access driveways at roadside ditches?
• No X Yes If"yes", provide information in next two boxes.
• Will 25-yr. flow pass without flowing over driveway in all cases? X Yes No
Without causing flowing or standing water on public roadway? X Yes No
Designs& materials comply with B-CS Technical Specifications? X Yes No
• Explain any"no"answers:
•
•
i
oAre culverts parallel to public roadway alignment? X Yes No Explain:
• U a)
a)
• x Creeks at Private Drives: Do private driveways, drives, or streets cross drainage
is ways that serve Above-Project areas or are in public easements/ ROW?
m z X No Yes If"yes" provide information below.
N How many instances? Describe location and provide information below.
cp
Location 1:
U
. Location 2:
a
Location 3:
,op
For each location enter value for: 1 2 3
Design year passing without toping travelway?
Water depth on travelway at 25-year flow?
•
Water depth on travelway at 100-year flow?
For more instances describe location and same information on separate sheet.
1111,
STORMWATER DESIGN GUIDELINES Page 19 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.11)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
Named Redulatory Watercourses (&Tributaries): Are culverts proposed on these
facilities? X No Yes, then provide full report documenting assumptions,
criteria, analysis, computer programs, and study findings that support proposed
design(s). Is report provided? Yes No If"no", explain:
Arterial or Major Collector Streets: Will culverts serve these types of roadways?
NX No Yes How many instances? For each identify the
location and provide the information below.
} c'(;
Instance 1:
°a,' Instance 2:
c
0 Instance 3:
c
0
O Yes or No for the 100-year design flow: 1 2 3
z E
x o Headwater WSE 1 foot below lowest curb top?
0 Spread of headwater within ROW or easement?
("W ° Is velocity limited per conditions (Table C-11)?
.N co Explain any"no" answer(s):
0 c
O 9
>,
as o
3
o e Minor Collector or Local Streets: Will culverts serve these types of streets?
w X No Yes How many instances? for each identify the
location and provide the information below:
0_ m
L Instance 1:
CI) >.,
Instance 2:
n o Instance 3:
� 0
0 For each instance enter value, or"yes"/"no"for: 1 2 3
c
O 03
• Design yr. headwater WSE 1 ft. below curb top?
Q - 100-yr. max. depth at street crown 2 feet or less?
E Product of velocity(fps) &depth at crown (ft)= ?
Is velocity limited per conditions (Table C-11)?
Limit of down stream analysis(feet)?
Explain any"no" answers:
STORMWATER DESIGN GUIDELINES Page 20 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.12)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site)(continued)
All Proposed Culverts: For all proposed culvert facilities (except driveway/roadside
ditch intersects) provide information requested in next eight boxes.
Do culverts and travelways intersect at 90 degrees? Yes No If not,
identify location(s) and intersect angle(s), and justify the design(s):
Does drainage way alignment change within or near limits of culvert and surfaced
approaches thereto? No Yes If"yes" identify location(s), describe
change(s), and justification:
Are flumes or conduit to discharge into culvert barrel(s)? No Yes If yes,
identify location(s)and provide justification:
Are flumes or conduit to discharge into or near surfaced approaches to culvert ends?
a)
No Yes If"yes" identify location(s), describe outfall design treatment(s):
0
0
> Is scour/erosion protection provided to ensure long term stability of culvert structural
0 components, and surfacing at culvert ends? Yes No If"no" Identify
locations and provide justification(s):
Will 100-yr flow and spread of backwater be fully contained in street ROW, and/or
drainage easements/ ROW? Yes No if not, why not?
Do appreciable hydraulic effects of any culvert extend downstream or upstream to
neighboring land(s) not encompassed in subject property? No Yes If
"yes" describe location(s) and mitigation measures:
Are all culvert designs and materials in compliance with B-CS Tech. Specifications?
Yes No If not, explain in Special Design Section of this Part.
STORMWATER DESIGN GUIDELINES Page 21 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised Auclust 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.13)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site)(continued)
Is a bridge included in plans for subject property project? x No Yes
If"yes" provide the following information.
Name(s)and functional classification of the roadway(s)?
What drainage way(s) is to be crossed?
w
m
cn
m`
A full report supporting all aspects of the proposed bridge(s) (structural, geotechnical,
hydrologic, and hydraulic factors) must accompany this summary report. Is the report
® provided? Yes No If"no" explain:
S
S
Is a Stormwater Provide a general description of planned techniques:
Pollution Prevention construction entrance, erosion control silt fence, hay bales at
Plan (SW3P) pond discharge points
0 established for
project construction?
No X Yes
C
Special Designs—Non-Traditional Methods
Are any non-traditional methods (aquatic echosystems, wetland-type detention, natural stream
410 replication, BMPs for water quality, etc.) proposed for any aspect of subject property project?
• X No Yes If"yes" list general type and location below.
S
S
S
S
S
Provide full report about the proposed special design(s) including rationale for use and
expected benefits. Report must substantiate that stormwater management objectives will not
be compromised, and that maintenance cost will not exceed those of traditional design
solution(s). Is report provided? Yes No If"no" explain:
'.
STORMWATER DESIGN GUIDELINES Page 22 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.14)
Stormwater Management Concept (continued)
Within Or Serving Subject Property(Phase, or Site)(continued)
Special Designs— Deviation From B-CS Technical Specifications
If any design(s) or material(s)of traditional runoff-handling facilities deviate from provisions of
B-CS Technical Specifications, check type facility(ies) and explain by specific detail element.
Detention elements Drain system elements Channel features
• Culvert features Swales Ditches Inlets Outfalls
_Valley gutters Bridges (explain in bridge report)
C In table below briefly identify specific element,justification for deviation(s).
Specific Detail Element Justification for Deviation (attach additional sheets if needed)
1)
C
2)
C 3)
C 4)
5)
•
$ Have elements been coordinated with the City Engineer or her/his designee? For each item
r above provide"yes" or"no", action date, and staff name:
1)
41 2)
3)
4)
sok
5)
Design Parameters
• Hydrology
Is a map(s) showing all Design Drainage Areas provided? X Yes No
Briefly summarize the range of applications made of the Rational Formula:
N/A. Rational Method can not be used for detention design per BCS Std. Design Guidelines.
What is the size and location of largest Design Drainage Area to which the Rational Formula
has been applied? acres Location (or identifier):
STORMWATER DESIGN GUIDELINES Page 23 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.15)
Design Parameters(continued)
Hydrology(continued)
In making determinations for time of concentration, was segment analysis used?
No X Yes In approximately what percent of Design Drainage Areas? 100
ok
As to intensity-duration-frequency and rain depth criteria for determining runoff flows, were any
criteria other than those provided in these Guidelines used? X No Yes If"yes"
identify type of data, source(s), and where applied:
For each of the stormwater management features listed below identify the storm return
frequencies (year) analyzed (or checked), and that used as the basis for design.
Feature Analysis Year(s) Design Year
Storm drain system for arterial and collector streets
Storm drain system for local streets
Open channels
Swale/buried conduit combination in lieu of channel
Swales
Roadside ditches and culverts serving them
i Detention facilities: spillway crest and its outfall
2, 10,25,50, & 100 100
• Detention facilities: outlet and conveyance structure(s) 2, 10,25,50, & 100 2,10,25,50,&100
M Detention facilities: volume when outlet plugged
• Culverts serving private drives or streets
Culverts serving public roadways
Bridges: provide in bridge report.
Hydraulics
IWhat is the range of design flow velocities as outlined below?
t Design flow velocities; Gutters Conduit Culverts Swales Channels
Highest (feet per second)
Lowest (feet per second)
Streets and Storm Drain Systems Provide the summary information outlined below:
C
Roughness coefficients used: For street gutters:
For conduit type(s) Coefficients:
STORMWATER DESIGN GUIDELINES Page 24 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.16)
Design Parameters (continued)
Hydraulics(continued)
Street and Storm Drain Systems (continued)
For the following, are assumptions other than allowable per Guidelines?
Inlet coefficients? No Yes Head and friction losses No Yes
Explain any"yes" answer:
In conduit is velocity generally increased in the downstream direction? Yes No
Are elevation drops provided at inlets, manholes, and junction boxes? Yes No
Explain any"no" answers:
Are hydraulic grade lines calculated and shown for design storm? Yes No
For 100-year flow conditions? Yes No Explain any"no" answers:
What tailwater conditions were assumed at outfall point(s)of the storm drain system? Identify
each location and explain:
•
•
• Open Channels If a HEC analysis is utilized, does it follow Sec VI.F.5.a? Yes No
• Outside of straight sections, is flow regime within limits of sub-critical flow? Yes No
If"no"list locations and explain:
Culverts If plan sheets do not provide the following for each culvert, describe it here.
For each design discharge, will operation be outlet (barrel) control or inlet control?
Entrance, friction and exit losses:
1.110
I ilk
Bridges Provide all in bridge report
I •
STORMWATER DESIGN GUIDELINES Page 25 of 26 APPENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012
t
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4— Drainage Concept and Design Parameters Continued (Page 4.17)
Design Parameters (continued)
Computer Software
What computer software has been used in the analysis and assessment of stomiwater
management needs and/or the development of facility designs proposed for subject property
project? List them below, being sure to identify the software name and version, the date of the
version, any applicable patches and the publisher
Part 5 — Plans and Specifications
Requirements for submittal of construction drawings and specifications do not differ due to use of a
Technical Design Summary Report. See Section III, Paragraph C3.
Part 6 — Conclusions and Attestation
Conclusions
Add any concluding information here:
4110
•
r
•
• Attestation
• Provide attestation to the accuracy and completeness of the foregoing 6 Parts of this Technical
Design Summary Drainage Report by signing and sealing below.
• "This report (plan) for the drainage design of the development named in Part B was prepared
by me (or under my supervision) in accordance with provisions of the Bryan/College Station
Unified Drainage Design Guidelines for the owners of the property. All licenses and permits
• required by any and all state and federal regulatory agencies for the proposed drainage
improvements have been issued or fall under applicable general peraitei%
(Affix Se4rGD**Tx:+s� 1
vg
Licensed Professional Engineer * • •••,,,..•P'�NpM
�' ME�„ISSA, .a. i
t. ....... �i
State of Texas PE No. 98398 t 14% E0./�0••
STORMWATER DESIGN GUIDELINES Page 26 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012