HomeMy WebLinkAbout03. RV Station development permit,...
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RV Station
Drainage Report
August 3, 2015
Prepared For:
RV Station
2815 N. Earl Rudder Freeway
Bryan, Texas 77803
Prepared By:
~ HOMEYER
ENGINEERING, INC.
TBPE FIRM REGISTRATION NO. F-8440
P.O. Box 294527
Lewisville, TX 75029
Phone: 972-906 -9985
Fax: 972-906-9987
This report for the drainage design of the RV Station development was prepared by me or under my
supervision in accordance with the provisions of the Bryan/College Station Unified Drainage Design
Guidelines SECTION Ill ADMINISTRATION STORMWATER DESIGN GUIDELINES Page 5 of 14
SECTION Ill: ADMINISTRTION effective February 2007 as revised February 2009 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 will be issued prior to the start of work.
Steven R. Homey?t r, P.E
Licensed Professi ~nal Engineer
State of Texas No. 86942
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Executive Summary
Drainage Report
RV Station
Table of Contents
A. General Location and Description of Project Area
B. Drainage Watershed and Study Area
C. Drainage Design Criteria
D. Drainage System Design
Table 1
E. Conclusions
F. References
G. Appendices
Exhibits:
A -General Location Map
B -Alum Creek Watershed
C -FEMA FIRMette
D.1 -Existing Drainage Area Map
D.2 -Proposed Drainage Area Map
E. 1 -Detention Plan
E.2 -Detention Calculations
E. 3 -Outlet Structure
F.1 -2-Year & 5-Year Hydrograph
F.2 -10-Year & 25-Year Hydrograph
F.3 -50-Year & 100-Year Hydrograph
G -Topographic Survey Conducted by Kling Engineering & Surveying
H-Site Plan
1.1 -Overall Grading Plan
1.2 -Site Grading Plan
J -Erosion Control Plan
Drainage Report -RV Station
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August 3, 2015
Executive Summary
Contact Information:
Engineer:
Homeyer Engineering, Inc.
Steven R. Homeyer, P.E., CFM
P.O. Box 294527
Lewisville, Texas 75029
Developer:
RV Station
Chris Falcone
2815 N. Earl Rudder Freeway
Bryan, Texas 77803
Identification of the proposed project
RV Station (5.22 acres in Phase 1)
Proposed 11.56 acre, C-1: Commercial
Project Location
1
This project is located within the city limits of the City of College Station, on the west side of
State Highway 6, south of William D. Fitch Parkway, and north of S. Oaks Road, primarily in the
Alum Creek watershed area per the City of College Station drainage manual.
This property is in a FEMA Zone X, an area determined to be outside the 500-year flood plain.
No portion of this site is located within a Zone A or AE designated flood area.
Hydrologic Characteristics
The existing site consists of grass covered pasture land with a few trees and includes no
buildings. Storm water on 9.42 acres of the 11.56 acre site flows south off-site. The remaining
2.14 acres flows northeast off-site to the State Highway 6 right of way.
Stormwater Management Plan
A proposed detention pond is located at the southern corner of the property and is designed to
accommodate the proposed flows of the overall tract (11.56 acres). A weir outlet structure will
be installed to release the developed flows at existing pre-developed flow rates. The drainage
area was determined using a topographic survey conducted by Kling Engineering & Surveying.
The Modified Rational method was used to determine the volume of stormwater storage needed
to compensate for increased runoff due to development and 10% was added to the volume per
the City of College Station Unified Stormwater Design Guidelines. The 5, 10, 25, 50 and 100-
year storm events were analyzed for both pre and post developed conditions. With an allowable
release rate of 42.10 cfs, the detention pond volume is required to hold 44,894 cubic feet of
water. The design of the rectangular weir outfall allows the pond to meet each of the design
years' allowable release rates and provides 44,894 cubic feet of storage at the 100-year release
elevation. The added 10% of volume requires the pond to provide a total of 49,383 cubic feet.
Drainage Report -RV Station August 3, 2015
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At 2.56 feet above the bottom of the pond, the detention facility provides 49,383 cubic feet of
volume.
Coordination with Other Entities
A Storm Water Pollution Prevention Plan will be prepared and the appropriate TCEQ permits
will be obtained prior to the issuance of a development permit by the city.
Technical Design Summary Report
One 7-page Drainage Report with Appendices dated August 3, 2015 and one set of construction
drawings dated August 3, 2015 comprise the drainage report for this project.
Drainage Report -RV Station August 3, 2015
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A. General Location and Description of Project Area
The RV Station is a proposed 5.22 acre commercial development on an 11.56 acre tract. The
proposed RV Station project is the first of several potential phases.
This project is located within the city limits of the City of College Station, on the west side of
State Highway 6, south of William D. Fitch Parkway, and north of S. Oaks Road, primarily in the
Alum Creek watershed area per the City of College Station drainage manual. (See Exhibit A)
Properties surrounding the proposed Project Area:
To the northeast: State Highway 6 R.O.W.
To the south: South Oaks, Volume 319, Page 821
To the northwest: Mary Ann Davis, 9.795 Acres, Volume 9538, Page 170
As stated above, this property is in the Alum Creek watershed per the City of College Station
drainage manual. This property is located in a FEMA Zone X, an area determined to be outside
the 500-year flood plain. No portion of this site is located within a Zone A or AE designated
flood area. (Exhibits B & C)
Engineer:
Homeyer Engineering, Inc.
Steven R. Homeyer, P.E., CFM
P.O. Box 294527
Lewisville, Texas 75029
B. Drainage Watershed and Study Area
Developer:
RV Station
Chris Falcone
2815 N. Earl Rudder Freeway
Bryan, Texas 77803
The existing site consists of grass and a few trees with no buildings. Storm water on 9.42 acres
of the 11.56 acre site flows south off-site. The remaining 2.14 acres flows northeast off-site to
the State Highway 6 right of way.
At present, 11.21 cfs of runoff leaves the site to the northeast and to the State Highway 6
R.O.W. Most of the existing on-site drainage, 49.34 cfs, ultimately flows to the southern corner
of the property and off-site to the South Oaks property.
The calculations in this drainage report indicate that the proposed detention pond is designed to
capture all of the developed on-site flows from the proposed RV Station development as well as
future phases. The proposed detention pond will reduce the total amount of storm water being
released onto the downstream properties from the post developed site.
C. Drainage Design Criteria
Pre-Developed:
The subject property consists of 11.56 acres. Of this area, 2.14 acres naturally drain to the
northeast. Using the City of College Station Stormwater Design Guidelines, a C-value of 0.45
was determined based on the existing site conditions. Using a pre-developed C-value of 0.45
and an intensity of 11.64 in./hr., the pre-developed flow from the areas flowing to the northeast
is 0 100=11.21 cfs. The remaining 9.42 acres of the property drains south to the South Oaks
property. This equates to a pre-developed flow 0 100=49.34 cfs to flow south off-site.
Drainage Report -RV Station August 3, 2015
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Post-Developed:
The proposed detention pond was designed to accept 91.42 cfs from the subject property during
a 100-year storm event. Of the remaining on-site flow, 11.19 cfs exits to the State Highway 6
R.O.W. undetained, while 7.24 cfs free flows to the southwest property line based on existing
conditions.
The storm water from the subject site will sheet flow to the proposed on-site detention facility
without ponding in the parking areas (Exhibits D.1 & D.2). The remainder of the runoff will be
allowed to free flow from the site undetained. The proposed detention facility will outfall at the
existing natural low point of the subject property. The stormwater will follow the existing swale
through the downstream property as it currently does to a tributary of Alum Creek. (See Exhibit
D.2 -Proposed DAM)
The proposed detention facility outlet structure is a rectangular weir (Exhibit E.3). As designed,
0 100=42.10 cfs will be released from the detention facility in addition to the 0 100 =11.19 cfs of free
flow to the northeast property line, and the 0 100=7.24 cfs of free flow to the southwest property
line.
The Modified Rational method was used to determine the volume of stormwater storage
required to compensate for the increased runoff due to the proposed development. In addition,
10% was added to the total volume of the pond in accordance with the City of College Station
Unified Stormwater Design Guidelines. The 5, 10, 25, 50 and 100-year storm events were
analyzed for both pre and post developed conditions. With an allowable release rate of 42.1 O
cfs, the detention pond volume is required to hold 44,894 cubic feet of water. The design of the
rectangular weir outfall allows the pond to meet each of the design years' allowable release
rates and provides for 44,894 cubic feet of storage at an elevation of 281. 72. The added 10% of
volume requires the pond to provide a total of 49,383 cubic feet of storage. At 2.56 feet above
the bottom of pond, the detention facility provides for 49,383 cubic feet of volume. The top of
pond elevation is 283.30. The proposed Detention Plan and Calculation sheets are included in
Exhibits E.1 -E.3.
The overall drainage area was determined using a topographic survey by Kling Engineering &
Surveying (Exhibit G). The time of concentration was computed using the formula from the City
of College Station Unified Stormwater Design Guidelines. A time of concentration for pre-
developed flows was calculated as approximately 10 minutes. For post developed flows, a
minimum time of concentration of 10 minutes was used.
Rainfall intensity was computed using the formulas in Table C-1 of the City of College Station
Unified Stormwater Design Guidelines and the times of concentration above. "C" factors were
obtained from Tables C-2 & C-3 of the City of College Station Unified Stormwater Design
Guidelines.
D. Drainage System Design
The proposed pond was designed to accept 0 100 =91.42 cfs from the subject property. The
proposed discharge from the subject property to the south and west is 0 100=49.34 cfs. Based
on the proposed free flow from the subject property, the proposed pond will discharge
0 100=42.10 cfs from the outlet structure proposed as part of this project.
Drainage Report -RV Station August 3, 2015
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The State Highway 6 R.O.W. to the east originally received a 0 10o=11.21 cfs from the subject
property and is designed to receive 0 100=11.19 cfs after the development is complete. Area P1
of the Proposed Drainage Area Map identifies the free flow to the east of 0 100 =11.19 (Exhibit
D.2).
Prior to the development of the proposed RV Station, the site generated 0 100=60.55 cfs as an
undeveloped pasture (Exhibit D.1). After the RV Station project is completed with the proposed
detention pond and outlet structure modifications, the proposed release rate will be 0 100=60.53
cfs based on the controlled release rate of 0 100=42.10 cfs from the detention pond and
0 100 =18.43 cfs of free flow from various areas within the development. (Refer to Table 1 for
Drainage Summary Totals).
The outlet structure has been designed to regulate the various storm events as identified above.
In addition, the outlet structure has also been designed to include the emergency overflow weir.
Should the proposed 3.16' outlet weir become clogged for any reason, the 10.0' weir designed
above the 100-year water surface elevation can convey the 100-year storm event without
overtopping the detention pond berms. Should the emergency overflow weir be utilized, the
velocity of the water exiting the outlet structure during the 100-year storm event will be 3.94 feet
per second.
Drainage Report -RV Station August 3, 2015
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Drainage Summary Totals for RV Station Subdivision -See Exhibits D.1 & D.2
I I I 2 yr. I 5 yr. I 10yr. I 25 yr. I SOyr. I 100 yr. I
"'C -Area Discharged North from RV Station 2.14 2.14 2 .14 2.14 2.14 2.14 QI "' a. QI 0 .... -u
QI < > -
QI "' 0 IV Area Discharged South from RV Station 9.42 9.42 9.42 9.42 9.42 9.42 QI
QI .... tr. <
"'C Vi
QI ~
t; g-~ To Proposed Detention Pond-Area P2 8 .73 8.73 8.73 8.73 8.73 8 .73 0 --c. QI "' > IV
QI QI 0 .... <
D Pre Developed 'C' value 0.45 0.45 0.45 0.45 0.45 0.45
Post Developed 'C' value 0.90 0.90 0 .90 0 .90 0.90 0.90
Rainfall Intensity {In/Hr) 6.33 7.69 8 .63 9 .86 11.15 11.64
.I:
"'C t! Discharge Off-site North from RV Station 6.10 7.41 8 .31 9 .50 10.74 11.21 QI 0
a. z
0 "ii c:;; > u..
QI u
0 -
QI ~ Discharge Off-site South from RV Station 41.80 47.26 49.34 .... 26.83 32.60 36.58 c. 0
"'
.I:
t!
0 z Discharge Off-site North from RV Station 6.08 7.39 8.29 9.48 10.72 11.19
"'C
QI a.
0
Qi -.I: > II) .. Discharge Off-site South from RV Station 3 .94 4.78 5.37 6.13 6.94 7 .24 :I QI u.. 0 o~ "'
t;
0 c.
c: Runoff to Detention Pond 49.71 60.40 67.78 77.44 87.57 91.42
0 ·.-::; c: --------------., .. Discharge from Detention Pond .,
Q 22.89 27.82 31.21 35.67 40.32 42.10
Drainage Re port -RV St ation August 3, 2015
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E. Conclusions
The intent of the RV Station Drainage Report is to safeguard life, property and public
infrastructure from damage due to ill-managed storm flow. This report demonstrates
compliance with the Unified Stormwater Design Guidelines and the City of College Station Code
of Ordinances.
The proposed drainage improvements on the subject property will reduce the overall storm
discharge from the subject property to existing levels. The proposed detention pond outfalls off-
site and is directed to Alum Creek.
F. References
City of College Station Code of Ordinances
Cities of Bryan and College Station Unified Stormwater Design Guidelines -January 2010
Drainage Report -RV Station August 3, 2015
Drainage Report
RV Station
Exhibits:
A -General Location Map
B -Alum Creek Watershed
C-FEMA FIRMette
Appendices
D.1 -Existing Drainage Area Map
D.2 -Proposed Drainage Area Map
E.1 -Detention Plan
E.2 -Detention Calculations
E.3 -Outlet Structure
F.1 -2-Year & 5-Year Hydrograph
F.2 -10-Year & 25-Year Hydrograph
F.3 -50-Year & 100-Year Hydrograph
G -Topographic Survey Conducted by Kling Engineering & Surveying
H-Site Plan
1.1 -Overall Grading Plan
1.2 -Site Grading Plan
J -Erosion Control Plan
40
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~HOMEYER
ENGINEERING, INC.
TBPE REGISTRATION NC. FwB44D
P.O. BOX 2GJ4527 +LEWISVILLE ¥TEXAS ¥75D2lil
9'72·9D8•99B5 PHONE •972•908•9987 FAX
WWW.MEI.US.COM
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SOUTH
SCALE: 1H=2000'
06-03-2013
DRAWN BY: RJM
CHECKED BY: SRH
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NORTH
EXHIBIT A
PROJECT
LOCATION
\
VICINITY MAP
RV--S-iATION
11.562 ACRES
ZONED C-1
CITY OF COLLEGE STAllON
BRAZOS COUNTY, TEXAS
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EXHIBIT B
SECTION IX
APPENDIX B-REGION'S WATERSHEDS
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Figure B-2: Alum Creek Watershed Area
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 5 of 24
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APPENDIX B: REGION'S WATERSHEDS
As Revised August 2012
N
Alum Creek Tributary 5.3
Peach Creek South Alum Creek
Tributary 16. 6 Tributary 5
+
Peach Creek South
Tributary 16
Peach Creek South
Tributary 16.5
+
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"-"~r----Stream Ac-1
Alum Creek
Tributary 6
!4/um Creek
Tributary 6.1 I .
Peach Creek South
Triliuta~v 16.5.l
Peach Creek South
Tributary 14.2
ZONEAE
Alum Creek
Tributary 5.1
HARPERS FERRY RO
1. ROCKCLIFFE LP
2. RAVENSTONE LP
3. CASTLEGATE DR
4 KENDAL GREEN
5. ROCKINGHAM LP
6. NEWARK CIR
7. STONE CASTLE
8. PARNELL DR
9. VICTORIA AVE
10. BROUGHAM PL
11. CARLISLE CT
12. NORHAM DR
13. ALEXANDRIA DR
14. SPRING GARDEN
15. DECATUR OR
16. SALEM CT
17. MARTINSVILLE L
18. DAYTON CT
1000
EXHIBITC
MAP SCALE 1" = 2000'
o 2000
PANEL0325E
FLOOD INSURANCE RATE MAP
ANDINCORPORATEDAREAS
(SEE MAP INDEX FOR F\RM PANEL LAYOUD
"""""' """"' fil!Efll< 4a11gs 0325
4aOOll3 0325
Notice to User. The Map Number shown below
sflould be used when placing map orders; the
Community Number shown above should be
used on Insurance applications for the subject
MAP NUMBER
48041C0325E
MAP REVISED
MAY 16, 2012
This is an official copy of a portion of the above referenced flood map. It
was extracted using F-M!TOn-Wne, This map does not reflect changes
or amendments which may have been made subsequent to the date on the
title block. For the latest product inform,.tlon about National Flood Insurance
Program t\ood maps check the FEMA Flood Map Store at www.m$c.fema.Qo\/