HomeMy WebLinkAboutDrainage Study Drainage Study
FOR
SUMMIT CROSSING SUBDIVISION
PHASE 2B
College Station
Brazos County, Texas
September 5, 2014
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Prepared For:
DWS Development, Inc.
PO Box 4508
Bryan,TX 77803
Prepared By:
RME Consulting Engineers
Texas Firm Registration No. F-4695
P.O. Box 9253
College Station,TX 77845
RME No. 298-0542
Drainage Study
SUMMIT CROSSING SUBIDIVISION
PHASE 2B
College Station
Brazos County, Texas
TABLE OF CONTENTS: PAGE
1.0 General Information 11
1.1 Scope of Report 2
1.2 Site and General Location 2
1.3 Description of Existing Conditions and Drainage Patterns 2
1.4 FEMA Information
2.0 Watersheds&Drainage Areas 22
2.1 Sub-Drainage Basins for Storm Sewer Collection System
3.0 Hydrologic Modeling 33
3.1 Rational Formula and Methodology 4
3.2 Stormwater Runoff Quantities
4.0 Storm Drainage System 4
4.1 Street Drainage 4 4
4.2 Storm Drain Inlets 56
4.3 Storm Drain Conduits
5.0 Certification 8
298-0542 Drainage Report.docx Page-i
LIST OF TABLES: PAGE
Section 4.0—Storm Drainage System 5
Table#1: Street Drainage Summary 5
Table#2: Curb Inlet Summary 6
Table#3: Storm Drainage Summary
298-0542 Drainage Report.docx Page-ii
ATTACHMENTS:
Section 1.0—General Information
Preliminary Plan
Final Plat
Vicinity Map
Section 2.0—Watersheds&Drainage Areas
Storm System Drainage Area Map
Section 4.0—Storm Drainage System
Winstorm—Hydraulic Computations—Storm Drainage System"C"
ST-01: Street&Drainage Plan/Profile
298-0542 Drainage Report.docx Page-iii
Drainage Study
SUMMIT CROSSING SUBIDIVISION
PHASE 2B
College Station
Brazos County, Texas
1.0 GENERAL INFORMATION
1.1 Scope of Report:
This report addresses the existing conditions and proposed drainage improvements for the
Summit Crossing Subdivision — Phase 2B. This development will consist of 34
townhome residential lots. This drainage study's scope also comments on the existing
detention facilities, currently constructed and designed/reported (dated March 17, 2008)
and the detention facility for Phase 2A & 2B (dated July 14, 2014). In addition, this
drainage report outlines the street drainage and storm sewer system improvements design
and analysis for the subject development.
The proposed development and drainage improvements are designed and analyzed in
accordance with the criteria outlined in the "Unified Stormwater Design Guidelines"
(USDG)manual of the City of College Station(CoCS).
1.2 Site and General Location:
The proposed development, Summit Crossing, Phase 2B, consists of 4.773 acre tract of
land wholly contained within the 89.64 acre parent tract of the master planned
subdivision. Summit Crossing, Phase 2B has direct access to Buena Vista and Lonetree
Drive and subsidiary access to SH 30 (Harvey Road East) and FM 158 (Boonville Road)
along its north and east property lines. Adjacent existing developments generally consist
of the Crescent Pointe development to the south and the Brazos Super Trac convenience
center to the northeast. All of these developments are in the College Station sewer
service area and are provided utility service by CoCS. Land adjacent to this development
to the southwest is currently owned by the same development group (The Summit
Crossing, LLC) and is anticipated to experience development of commercial, retail,
office, and residential improvements in the near future. The existing, proposed, and
future surrounding developments and phases are depicted on the Preliminary Plan which
is provided in the "Attachment— Section 1.0" portion of this report. Also, the Final Plat
of Summit Crossing—Phase 2B is provided in the same location of this report.
A Vicinity Map, for this project site, is provided and is located in the "Attachment —
Section 1.0" portion of this manual. This map is being provided as an aid in locating the
site. Drawings describing the work and its specific locations are contained in the
Construction Drawings prepared by RME Consulting Engineers, College Station, Brazos
County, TX. These Construction Drawings are included as part of this Drainage Report
by reference.
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Summit Crossing,Phase 2B RME Consulting Engineers
Drainage Study September 5,2014
1.3 Description of Existing Conditions and Drainage Patterns:
The 4.773-acre tract, which contains the proposed development of Summit Crossing,
Phase 2B, is primarily an unimproved area with moderately well sloping (approximately
1.0%)undeveloped site with natural drainage systems that convey runoff to the detention
facility constructed for Phase 2B. Existing land-cover general consists of open grassy
areas with some thick brush, weeds, and trees along the fence lines. Elevations range on
the site from approximately 298' Mean Sea Level (MSL) to approximately 306' MSL.
The Brazos County soil maps, as reported on the NRCS Web Soil Survey web-based
program, indicates that the studied area is primarily comprised of Type C and D soils.
These soils generally consist of clays or silty clay/sand mixtures with low absorption
rates.
Detention for new impervious cover, within this development, was accounted for in this
Phase 2B detention facility. A more descriptive analysis and explanation of these
detention facilities are provided in the original Drainage Study(prepared by RME on July
14, 2014). Therefore,no additional detention will be required for this phase.
1.4 FEMA Information:
The entire master planned Summit Crossing Subdivision does not lie within mapped 100-
year floodplain as graphically depicted by the Federal Emergency Management Agency
(FEMA)—Flood Insurance Rate Map (FIRM) Community/Panel number 48041C 0220E,
with an effective date of May 16,2012.
2.0 WATERSHEDS & DRAINAGE AREAS
2.1 Sub-drainage Basins for Storm Sewer Collection System:
For analysis of the internal storm drainage system,the original drainage area(called P1 in
the July 14, 2014 report) was further broken into smaller sub-drainage areas so that
individual curb inlets, grate inlets, and conveyance elements could properly be designed
and analyzed. The Storm System "C" — Drainage Area Map, illustrates these sub-
drainage areas and is an expansion of the drainage studies for downstream collection
systems, and is located in the"Attachment—Section 2.0"portion of this Drainage Study.
The sub-drainage areas, per system, are briefly described below. Please note that when
sub-drainage areas abutted or received runoff from future phases the hydrologic model
reflected the worse-case scenario for that receiving node. Dependent upon location
dictated whether existing drainage conditions were modeled or future development
conditions were modeled. This is due to the fact that at future development conditions
some receiving system's node areas will be significantly decreased.
• System C—Majority of Phase 2B.
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Summit Crossing,Phase 2B RME Consulting Engineers
Drainage Study September 5,2014
3.0 HYDROLOGIC MODELING
3.1 Rational Formula and Methodology:
The Rational Method (Q=CIA) is one of the more frequently used methods to determine
the peak runoff from a watershed and is typically reliable for small watersheds (< 50
acres). The Rational Method generates hydrologic data based on drainage area
geometries, surface conditions, and rainfall intensities. The Rational Method will be
employed to determine these sizes of watershed's runoff values, for the sub-drainage
areas for the internal storm drain systems, and it is explained further as:
Q=CIA where,
Q=peak runoff rate (cubic feet per second);
C = runoff coefficient — This represents the average runoff characteristics of the
land cover within the drainage area and is a dimensionless coefficient.
Runoff coefficients are interpolated from either Table C-2 or C-3 of the
USDG;
I =average rainfall intensity(in/hr);
A=area of land that contributes stormwater runoff to the area of study(acres);
RUNOFF COEFFICIENT(C):
The runoff coefficient(C) for various sub-drainage basins was estimated from the USDG,
Table C-2 and C-3 by comparison of runoff surface types to percentage of land coverage
and total drainage area. Calculations for these weighted runoff coefficients are included
in the"Attachment—Section 4" section of this Drainage Study.
TIME OF CONCENTRATION"T:':
The Time-of-Concentration (Ta) for each sub-drainage basin is used to determine the
intensity of the rainfall event for the corresponding drainage basin. Time-of-
Concentration is defined as the time required for the surface runoff to flow from the most
remote point in a watershed to the point of analysis. The Te is the summation of the flow
time for shallow overland flow and/or concentrated flow to the lower reach of the
watershed. Overland sheet flow is a method developed by Overton and Meadows and is
typically used for flow distances of 300 feet or less. Concentrated flows are estimated by
velocities determined by use of the Manning's Equation. The minimum Tc used for any
drainage area will 10.0 minutes.
RAINFALL INTENSITY(I):
Rainfall intensities (I) are the average rate of rainfall in inches per hour for a given
rainfall event. The duration of "I" is assumed to occur at the computed Time-of-
Concentration for each respective drainage basin. Rainfall intensities can be determined
by use of intensity-duration-frequency (IDF) curves or from intensity equations which are
provided in the TxDOT Hydraulic Manual.
298-0542 Drainage Report.docx Page-3
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Summit Crossing,Phase 2B RME Consulting Engineers
Drainage Study September 5,2014
3.2 Stormwater Runoff Quantities:
Runoff values generated from the smaller sub-drainage areas, for purposes of modeling
the proposed internal storm sewer system and driveway culverts, are not summarized in
this section but are covered in the subsequent Section 4.0 — Storm Drainage System.
These hydrologic analyses utilized the Rational Method. Runoff values for the internal
storm sewer system were computed within the Winstorm hydraulic program (further
explained in Section 4.0).
4.0 STORM DRAINAGE SYSTEM
The "system criteria" listed below in the follow sub-sections are only the main highlights of
the CoCS — USDG. The proposed development and drainage improvements are designed
and analyzed in full accordance with the criteria outlined in this manual.
4.1 Street Drainage
SYSTEM CRITERIA:
1. The maximum velocity of street flow shall not exceed 10 fps. At "T" street
intersection the flow velocity will be checked on the stem of the "T". The minimum
velocity shall be maintained by keeping a gutter slope of 0.60%or greater;
2. The depth of flow shall be limited to the top of the curb for the design flow (10-year
rainfall event) and shall be contained within the right-of-way during the 100-year
rainfall event:
a. Local Streets — The design storm in local streets shall be limited to the top of
crown or the top of curb,whichever is less;
b. Collector Streets — Design storm flow in collector streets shall be limited so that
one 12-foot wide are at the center of the street will remain clear of water;
3. Curb inlets shall be placed in a manner to ensure that the design storm flows are
intercepted along street legs in advance of the curb returns. For intersection types of
Collector to Local the curb inlets shall be placed along the local legs. For
intersection types of Local to Local it is preferred that the curb inlets be located along
two legs.
METHODOLGY& CONCLUSIONS:
The hydraulic analysis, for street drainage with straight crowns, and corresponding
results were determined by using the following equation for triangular channels.
Corresponding flows for the studied locations were extracted from the WINSTORM
hydraulic program, for stormwater modeling. This TxDOT program's typical use is for
modeling gravity stormwater systems. The Winstorm data is summarized, for each
system, under the Winstorm—Hydraulic Computations (reference "Attachment— Section
4.0"portion of the report).
Flow Depth,Y= {Qn/ [(0.56z*S15)1}3/8 where,
Y=depth of flow(ft);
Q=gutter discharge (cubic feet per second);
298-0542 Drainage Report.docx Page-4
Summit Crossing,Phase 2B RME Consulting Engineers
Drainage Study September 5,2014
z=reciprocal of the crown slope (ft/ft);
S =street or gutter slope (ft/ft);
n=Manning's roughness coefficient(typically 0.018);
Flow Velocity,V= [(1.49=n) * (R2/3 * SIN where,
V=velocity of flow(fps);
R=hydraulic radius(cross-sectional area/wetted perimeter);
S=street or gutter slope (ft/ft);
n=Manning's roughness coefficient(typically 0.018);
Street drainage depths, for the both the design storm and 100-year rainfall event, are
summarized below in Table#1 —"Street Drainage Summary".
TABLE#1
STREET DRAINAGE SUMMARY
10-YR 100-YR
10-YR 100-YR Gutter Flow Flow 10-YR 100-YR
Runoff Q Runoff Q Slope Depth Depth Velocity Velocity
Location (cfs) (cfs) (ft/fl) (ft) (ft) (fps) (fps)
Buena Vista-CA."CI" 6.953 9.373 0.0204 0.27 0.31 3.60 3.88
Buena Vista-C.I."C2 6.228 8.396 0.0204 0.26 0.29 3.51 3.78
Street Drainage Notes:
1. Design calculations are with a n=0.018 and z=33.3(cross-slope of 3.00%);
2. Runoff rates illustrated are from the Winstorm program. These Q's are the total runoff values being
conveyed in the gutter immediately upstream of the identified inlet. For curb inlets at grade, the
total runoff is input in lieu of that inlet's intercept capacity;
3. Maximum allowable flow depth for Buena Vista&Lonetree Drive are D=0.42';
4. Flows from DA"Cl"&"C2"where reduced by 33%to emulate partial flows from either direction;
4.2 Storm Drain Inlets
SYSTEM CRITERIA:
1. All curb inlets within this project are specified as recessed curb inlets with gutter
depressions. Curb inlets that are located on streets with less than a 1% longitudinal
slope shall be analyzed as curb inlets at sumps;
2. At any developments scenario and analyzed rainfall event, up to the 100-year
frequency,the ponding depth at the inlet shall not exceed 24";
METHODOLGY&CONCLUSIONS:
The hydraulic analysis, for curb inlet sizing, and corresponding results were determined
by using the following equation from the USDG, Table C-8 of Appendix C.
Corresponding flows for the studied locations were extracted from the WINSTORM
hydraulic program, for stormwater modeling. This TxDOT program's typical use is for
modeling gravity stormwater systems. The Winstorm data is summarized, for each
system,under the Winstorm—Hydraulic Computations (reference "Attachment—Section
4.0"portion of the report).
Required Curb Length (on grade),L=KC Q°'42S°3(1 -(nSe))°'6 where,
298-0542 Drainage Report.docx Page-5
Summit Crossing,Phase 2B RME Consulting Engineers
Drainage Study September 5,2014
Se=S%+(Eoa+W)
L=calculated curb length requirement(ft);
Se= Substitution for S.which is the cross slope of the road(ft/ft);
Kc=0.6 (coefficient);
S = street or gutter slope (ft/ft);
a= gutter depression depth(ft);
W=width of gutter depression(ft);
Eo=ratio of frontal flow to total gutter flow(estimated at 0.50);
Required Curb Length (at sag),L=Q/(3.0*y''S)where,
L=calculated curb length requirement(ft);
Q=gutter discharge (cubic feet per second);
y=total depth of water or head on the inlet(ft);
Curb inlet sizing, for the both the design storm and 100-year rainfall event, are
summarized below in Table#2—"Curb Inlet Summary".
TABLE#2
CURB INLET SUMMARY
10-YR 100-YR
10-YR 100-YR Gutter Required Required Provided
Curb Inlet Runoff Q Runoff Q Slope Length Length Length
Location-Curb Inlet I.D. Type (cfs) (cfs) (ft/ft) (ft) (ft) (ft)
Buena Vista"CI" Sag 10.377 13.989 0.0204 10.87 14.65 15
Buena Vista"C2" Sag 9.296 12.531 0.0204 9.74 13.13 15
Curb Inlet Notes:
1. Design calculations are with a standard gutter depression depth(a)of 0.33' and standard depression
width(W)of 2';
2. Design calculations are with a n=0.018 and a standard cross-sectional slope of 3.0%(0.03 ft/ft);
3. Curb inlets analyzed at sags will utilize the depth(y)of 6"unless otherwise noted;
4. Curb inlets at grade were allowed to be undersized so long as the downstream gutter section and
ultimate receiving sag inlet could accommodate conveyed flows;
5. Inlets at sags where reduced by 10%(opening)to account for clogging;
4.3 Storm Drain Conduits
SYSTEM CRITERIA:
1. Storm drainage systems are designed to convey the design storm and analyzed during
the 100-year rainfall event. An gravity over-flow route, contained within the right-of-
way or public drainage easement, has been provided so that conduits that are unable
to convey the 100-year storm can "spill" over into these over-flow systems so that
situations that are hazardous to life,property,or public infrastructure is prevented;
2. For the design storm the minimum flow velocity in a conveyance element shall not be
less than 2.5 fps and not greater than 15.0 fps;
3. Roughness coefficients for storm sewer pipes were assigned at 0.012 for smooth-lined
High Density Poly-Ethylene (HDPE)pipe and 0.013 for RCP;
4. Junction boxes were provided at all changes in conduit size and grade or alignment
changes. Where junction box spacing exceeded 300 feet for 54" diameter pipe, or
298-0542 Drainage Report.docx Page-6
Summit Crossing,Phase 2B RME Consulting Engineers
Drainage Study September 5,2014
smaller, and 500' for pipes exceeding 54" in diameter, additional manhole holes were
provided to maintain the desired spacing;
5. Storm sewer conduits with a diameter of 18"through 24" were hydraulically analyzed
with a 25% reduction in cross-sectional area to compensate for potential partial
blockage. Therefore 18" sized pipes were input as 1.30' diameter pipe and 24" sized
pipes were inputted as a 1.73' diameter pipe;
6. Conveyance elements were sized so that the design storm's hydraulic grade line
would equal to or less than 12"below the respective curb inlet curb elevation;
7. Free-open area of all grate inlets were reduced by 25%to compensate for cloggage;
TAILWATER CONSIDERATIONS:
(Tailwater data from Original Report)
Tailwater for the storm drainage system was set at a free-discharge condition equal to the
outlet pipe soffit elevation unless the downstream receiving system's tailwater surcharged
the pipe. In this case the tailwater was set to equal that of the downstream system.
Therefore the design storm, 10-year event, had a TW=296.93', and the analyzed storm,
100-year event,had a TW=298.57'.
METHODOLGY&CONCLUSIONS:
The hydraulic analysis, for storm drain conduits, and corresponding results were
determined by using the WINSTORM hydraulic program, for stormwater modeling. This
TxDOT program's typical use is for modeling gravity stormwater systems. The
Winstorm data is summarized, for each system, under the Winstorm — Hydraulic
Computations (reference "Attachment — Section 4.0" portion of the report). Also, for
graphical illustration purposes the hydraulic grade line (HGL), for the 10-year and 100-
year, are identified on ST-01 Street & Drainage Plan/Profile of the construction drawings
(see"Attachment—Section 4.0"portion of the report).
Storm drain conveyance elements and system, for the design storm (10-year rainfall
event) and analyzed storm (100-year rainfall event), are summarized below in Table #3 —
"Storm Drainage Summary". As illustrated the HGL of this system is contained within
the storm sewer pipe completely during both studied rainfall events.
TABLE#3
STORM DRAINAGE SUMMARY
Pipe Size 10-YR US Top of
US Node DS Node Diameter Velocity Capacity Runoff Q US HGL Curb Diff
ID ID (in) (fps) (cfs) (cfs) (ft) Elev.(ft) (ft)
SYSTEM"C"- 10 YEAR DESIGN STORM
Cl OUT1 30 3.99 34.21 19.59 297.18 300.12 2.94
C2 C3 24 3.95 12.88 9.30 297.32 300.12 2.80
SYSTEM"C"- 100 YEAR DESIGN STORM
Cl OUT1 30 5.38 34.21 26.41 299.03 300.12 1.09
C2 C3 24 5.33 12.88 12.53 299.27 300.12 0.85
Storm Drainage System Notes:
1. All storm sewer system outfalls are specified with velocity dissipaters at the headwall with
additional rock rip-rap erosion control;
298-0542 Drainage Report.docx Page-7
Summit Crossing,Phase 2B RME Consulting Engineers
Drainage Study September 5,2014
5.0 CERTIFICATION
"This report for the drainage design of Summit Crossing, Phase 2B 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." ��
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298-0542 Drainage Report.docx Page-8
Section 1 .0
GENERAL INFORMATION
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Section 2.0
WATERSHEDS & DRAINAGE AREAS
Section 4.0
STORM DRAINAGE SYSTEM
stmOutput.txt
•
WinStorm (STORM DRAIN DESIGN) Version 3.05, Jan. 25, 2002
Run @ 9/5/2014 1: 03:27 PM
PROJECT NAME : 298
JOB NUMBER 0542
PROJECT DESCRIPTION : System C
DESIGN FREQUENCY 10 Years
ANALYSYS FREQUENCY : 100 Years
MEASUREMENT UNITS: ENGLISH
OUTPUT FOR DESIGN FREQUENCY of: 10 Years
Runoff Computation for Design Frequency.
ID C Value Area Tc Tc Used Intensity Supply Q Total Q
(acre) (min) (min) (in/hr) (cfs) (cfs)
C-1 0. 65 1.85 10.00 10.00 8 . 63 0.000 10. 377
C-2 0.7 1.54 10.00 10.00 8 . 63 0.000 9.296
Sag Inlets Configuration Data.
Inlet Inlet Length/ Grate Left-Slope Right-Slope Gutter Depth Critic
ID Type Perim. Area Long Trans Long Trans n DeprW Allowed Elev.
(ft) (sf) (%) (%) (%) (%) (ft) (ft) (ft)
C-1 Curb 10.00 n/a 0.70 3. 50 2.00 3. 50 0.014 1.50 0.50 300. 12
C-2 Curb 10.00 n/a 0.70 3.50 2.00 3.50 0.014 1.50 0.50 300. 12
Sag Inlets Computation Data.
Inlet Inlet Length Grate Total Q Inlet Total Ponded Width
ID Type Perim Area Capacity Head Left Right
(ft) (ft) (sf) (cfs) (cfs) (ft) (ft) (ft)
C-1 Curb 10. 00 n/a n/a 10.377 10.327 0. 502 9.54 7 . 85
C-2 Curb 10. 00 n/a n/a 9.296 10.327 0. 466 9. 19 7 .55
Cumulative Junction Discharge Computations
Node Node Weighted Cumulat. Cumulat. Intens. User Additional Total
I.D. Type C-Value Dr.Area Tc Supply Q Q in Node Disch.
(acres) (min) (in/hr) cfs) (cfs) (cfs)
Page 1
stmOutput.txt
C-i Curb 0. 673 3.39 10. 10 8. 60 0.000 0. 00 19. 590
C-2 Curb 0.700 1.54 10. 00 8.63 0.000 0.00 9.296
OUT3 Outlt 0. 673 3.39 10. 10 8. 60 0.000 0.00 19. 590
Conveyance Configuration Data
Run# Node I.D. Flowline Elev.
US DS US DS Shape # Span Rise Length Slope n_value
(ft) (ft) (ft) (ft) (ft) (%)
1 C-i OUT3 294 . 63 293. 86 Circ 1 0.00 2.50 110.70 0.70 0.013
2 C-2 C-1 295. 66 295.40 Circ 1 0.00 1.73 37.00 0.70 0.013
Conveyance Hydraulic Computations. Tailwater = 296. 930 (ft)
Hydraulic Gradeline Depth Velocity Junc
Run# US Elev DS Elev Fr.Slope Unif. Actual Unif. Actual Q Cap Loss
(ft) (ft) (%) (ft) (ft) (f/s) (f/s) (cfs) (cfs) (ft)
1* 297 . 18 296. 93 0.228 1.36 2.50 7 .20 3. 99 19.59 34 .21 0. 000
2* 297 .32 297 . 18 0.366 1.09 1.73 5. 97 3. 95 9.30 12.88 0.000
OUTPUT FOR ANALYSYS FREQUENCY of: 100 Years
Runoff Computation for Analysis Frequency.
ID C Value Area Tc Tc Used Intensity Supply Q Total Q
(acre) (min) (min) (in/hr) (cfs) (cfs)
C-1 0. 65 1.85 10. 00 10.00 11. 64 0.000 13. 989
C-2 0.7 1.54 10.00 10. 00 11. 64 0. 000 12.531
Sag Inlets Configuration Data.
Inlet Inlet Length/ Grate Left-Slope Right-Slope Gutter Depth Critic
ID Type Perim. Area Long Trans Long Trans n DeprW Allowed Elev.
(ft) (sf) (%) (%) (%) (%) (ft) (ft) (ft)
C-1 Curb 10. 00 n/a 0.70 3. 50 2. 00 3. 50 0.014 1.50 0. 50 300. 12
Page 2
stmOutput.txt
•
C-2 Curb 10.00 n/a 0.70 3.50 2. 00 3.50 0. 014 1.50 0.50 300. 12
Sag Inlets Computation Data.
Inlet Inlet Length Grate Total Q Inlet Total Ponded Width
ID Type Perim Area Capacity Head Left Right
(ft) (ft) (sf) (cfs) (cfs) (ft) (ft) (ft)
C-1 Curb 10.00 n/a n/a 13. 989 15. 586 0.491 10. 69 8.79
C-2 Curb 10.00 n/a n/a 12.531 10.327 0.569 10.29 8 . 44
Cumulative Junction Discharge Computations
Node Node Weighted Cumulat. Cumulat. Intens. User Additional Total
I.D. Type C-Value Dr.Area Tc Supply Q Q in Node Disch.
(acres) (min) (in/hr) cfs) (cfs) (cfs)
C-1 Curb 0. 673 3.39 10.10 11.59 0.000 0.00 26.413
C-2 Curb 0.700 1.54 10.00 11. 64 0.000 0.00 12. 531
OUT3 Outlt 0. 673 3.39 10. 10 11.59 0. 000 0.00 26.413
Conveyance Configuration Data
Run# Node I.D. Flowline Elev.
US DS US DS Shape # Span Rise Length Slope n_value
(ft) (ft) (ft) (ft) (ft) (%)
1 C-1 OUT3 294. 63 293. 86 Circ 1 0. 00 2.50 110.70 0.70 0. 013
2 C-2 C-1 295. 66 295. 40 Circ 1 0. 00 1.73 37 .00 0.70 0.013
Conveyance Hydraulic Computations. Tailwater = 298 .570 (ft)
Hydraulic Gradeline Depth Velocity June
Run# US Elev DS Elev Fr.Slope Unif. Actual Unif. Actual Q Cap Loss
(ft) (ft) (%) (ft) (ft) (f/s) (f/s) (cfs) (cfs) (ft)
1* 299.03 298. 57 0. 415 1. 64 2.50 7.74 5.38 26. 41 34 .21 0. 000
2 299.27 299. 03 0. 665 1.38 1.73 6.24 5. 33 12.53 12.88 0. 000
END
* Super critical flow.
NORMAL TERMINATION OF WINSTORM.
Warning Messages for current project:
Page 3
stmOutput.txt
Runoff Frequency of: 10 Years
Capacity of sag inlet exceeded at inlet Id= C-1
Runoff Frequency of: 100 Years
Capacity of sag inlet exceeded at inlet Id= C-2
Page 4
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
12-/M 1✓ CAnks L- - City: Bryan
.P Qx 9223 )C College Station
COLL1- 71 2 Date of Submittal: °I. 1.511`-{I I y
Lead Engineer's Name and Contact Info.(phone, e-mail,fax): Other:
s 1� NOAr c-PLF, P.
Supporting Engineering/Consulting Firm(s): Other contacts:
Developer/Owner/Applicant Information
Developer/Applicant Name and Address: Phone and e-mail:
S E-1-0 f rel,Sv.T . t ( NC
C
Property Owner(s) if not Developer/ Applicant(&address): Phone and e-mail:
Project Identification
Development Name: y A cT Cek:Bs t f.r Com- Z 6
is subject property a site project, a single-phase subdivision, or part of a multi-phase subdivision?
If multi-phase, subject property is phase 3 of .
Legal description of subject property (phase)or Project Area:
(see Section II, Paragraph B-3a)
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.
ri,/�s-cE:e. t7.E4 f mn.47 o-F t-Yn w\cc C4e,m,skr.r C;
General Location of Project Area, or subject property(phase):
1* 3o - i-A- - r 1 Pt' -r
In City Limits? Extraterritorial Jurisdiction (acreage):
Bryan: acres. Bryan: College Station:
College Station: ''773 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:
Lsr y-r r C 42-Cf=sca.tCk• P14Z
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: T-----"bp Existjnq 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? _ 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
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 Actions (include dates)
Approved ?
US Army Crops of
Engineers
No )( Yes
US Environmental
Protection Agency
No X Yes
Texas Commission on
Environmental Quality / P
No Yes X
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 _ 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 _x 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
Proposed
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 Yes
(Section II, Paragraph B1) or a tributary thereof?
Is any part of subject property in flloodplain
No X Yes Rate Map22-0
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.
X. se, ofR-kc-;",st\_- 311710 S SC - P2S c NSO
Sc t ZN il �
Is the stormwater management plan for the property in substantial conformance with the
earlier study? Yes X No If not, explain how it differs.
No If subject property is not part of multi-phase project, describe stormwater management
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? }C 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?
r If the need for How was determination made?
J) Type 1 Detention
(X 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? 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? 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? 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)?
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).
Nearby
Drainage Do any of these have hydrologic or hydraulic influence on proposed stormwater
Facilities design? 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.
Discharge(s)To Lower Property(ies) (Section II, Paragraph El)
Does project include drainage features(existing or future) proposed to become public via
platting? No Yes Separate Instrument? No _ Yes
Per Guidelines reference above, how will Establishing Easements(Scenario 1)
runoff be discharged to neighboring 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#_ )
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?
No
Yes
How will runoff from Project 1. With facility(ies)involving other development projects.
Area be mitigated to pre- 2 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# )
3. By phase(or site)project: Describe planned mitigation measures for phases(or sites) in
subsequent questions of this Part.
Are aquatic echosystems proposed? No Yes In which phase(s) or
project(s)?
�-
} Are other Best Management Practices for reducing stormwater pollutants proposed?
a No Yes Summarize type of BMP and extent of use:
c
.N
(1) 0
�_ z
If design of any runoff-handling facilities deviate from provisions of B-CS Technical
n Specifications, check type facility(ies) and explain in later questions.
cn Detention elements Conduit elements Channel features
92
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 Yes Identify type and
general size and In which phase(s).
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):
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? )C, 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?
-0
a
coa Steepest side slopes: Usual front slopes: Usual back slopes:
a)
Flow line slopes: least Typical distance from travelway:
-a (Attached Exhibit# _)
0 typical greatest
Z
-
as
� Are longitudinal culvert ends in compliance with B-CS Standard Specifications?
Yes No, then explain:
At intersection or otherwise, do valley gutters cross arterial or collector streets?
3 0.. No _Yes If yes explain:
vv
s. Are valley gutters proposed to cross any street away from an intersection?
2 a)Z No Yes Explain: (number of locations?)
15 -
m
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 p, (Dol. Usual L-(0!• Greatest 2-Q`'i '
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.
cs-
Will inlet size and placement prevent exceedi_ng allowable water spread for 10-year
design storm throughout site(or phase)? X Yes No If no, explain.
°
rn
c Sag curves:Are inlets placed at low points? X Yes No Are inlets and
onduit sized to prevent 100-year stormflow from ponding at greater than 24 inches?
Yes No Explain"no" answers.
U)
m
a)
in
Will 100-yr stormflow be contained in combination of ROW and buried conduit on
whole length of all streets? X Yes No If no, describe where and why.
Do designs for curb, gutter, and inlets comply with B-CS Technical Specifications?
X, Yes No If not, describe difference(s) and attach justification.
Are any 12-inch laterals used? x No Yes Identify length(s) and where
used.
Nv, Pipe runs between system Typical -3 7 Longest 1-70
° } access points(feet):
aEi Are junction boxes used at each bend? )C Yes No If not, explain where
and why.
c
f6 z
E I° Are downstream soffits at or below upstream soffits? Least amount that hydraulic
Yes ,e. 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).
1) Watercourse(or system),velocity, and angle?
ll,.c�W
2) Watercourse(or system),velocity, and angle?
C O
c
O
O C_
E °'
• E m ^3)Watercourse (or system), velocity, and angle?
TN
0
f
-0 a
E For each outfall above,what measures are taken to prevent erosion or scour of
Nreceiving and all facilities at juncture?
1)
is
Co
2)
U)
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):
�•
U)
a)
U)
Di; }
m I Flow line slopes(minimum and maximum):
0
ami o
Z Outfall characteristics for each (velocity, convergent angle, &end treatment).
13
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? No Yes If so, provide the following:
Is 25-year flow contained with 6 inches of freeboard throughout? Yes No
+U Are top of banks separated from road shoulders 2 feet or more? Yes No
Are all ditch sections trapezoidal and at least 1.5 feet deep? Yes No
N For any"no"answers provide location(s) and explain:
CO
CO
0
If conduit is beneath a swale, provide the following information(each instance).
Instance 1 Describe general location, approximate length:
w
>- Is 100-year design flow contained in conduit/swale combination? Yes No
Iiff If "no" explain:
O 0 Space for 100-year storm flow? ROW Easement Width
Z c Swale Surface type, minimum Conduit Type and size, minimum and maximum
(�I c and maximum slopes: slopes, design storm:
cs
m Inlets Describe how conduit is loaded (from streets/storm drains, inlets by type):
c T
C c
L �
• L
C
O
O.0 o Access Describe how maintenance access is provided (to swale, into conduit):
w is
o E
0 0
= c
.o Instance 2 Describe general location, approximate length:
1:43
U)
c v Is 100-year design flow contained in conduit/swale combination? Yes No
o o If "no" explain:
m Q,
c
E • Space for 100-year storm flow? ROW Easement Width
"' Swale Surface type, minimum Conduit Type and size, minimum and maximum
• and maximum slopes: slopes, design storm:
O 0-
4-2 Inlets Describe how conduit is loaded (from streets/storm drains, inlets by type):
• c
°
• 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:
E xa
o w
L
o ui Is 100-year design flow contained in swale? Yes No Is swale wholly
c >_ within drainage ROW? Yes No Explain"no"answers:
L
a)
Access Describe how maintenance access is provide:
o
z
VI
O
og Instance 2 Describe general location, approximate length, surfacing:
a)
�•
c
o E
= a2
3 m Is 100-year design flow contained in swale? Yes No Is swale wholly
a
4) within drainage ROW? Yes No Explain "no" answers:
3 �
N 0
X Access Describe how maintenance access is provided:
z
d
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.
ami .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:
c
(1)
E I
a�
o Instance 2:
n
E o
z
az?(
ol
Instance 3:
-c
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? No Yes
If"yes" provide the information below.
Will small creeks and their floodplains remain undisturbed? 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.
V
a)
c
Watercourses (and tributaries): Aside from fringe changes, are Regulatory
Watercourses proposed to be altered? _ 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
° and data. Is full report submitted? Yes No If"no" explain:
E
m
L All Proposed Channel Work: For all proposed channel work, provide information
U 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)
Stormvvater Management Concept(continued)
Within Or Serving Subject Property(Phase, or Site)(continued)
How many facilities for subject property project? For each provide info. below.
For each dry-type facilitiy: Facility 1 Facility 2
Acres served&design volume+ 10%
100-yr volume:free flow& plugged
Design discharge (10 yr&25 yr)
Spillway crest at 100-yr WSE? yes no yes no
Berms 6 inches above plugged WSE? yes no yes no
Explain any"no"answers:
0
>
a)
For each facility what is 25-yr design Q, and design of outlet structure?
Facility 1:
0
Facility 2:
Do outlets and spillways discharge into a public facility in easement or ROW?
Facility 1: Yes No Facility 2: Yes No
If"no"explain:
a)
0
0
0
a For each, what is velocity of 25-yr design discharge at outlet? &at spillway?
a) Facility 1: _& Facility 2: &_
Are energy dissipation measures used? No Yes Describe type and
location:
c
0
C
a)
a)
For each, is spillway surface treatment other than concrete? Yes or no, and describe:
Facility 1:
Facility 2:
For each, what measures are taken to prevent erosion or scour at receiving facility?
Facility 1:
Facility 2:
If berms are used give heights, slopes and surface treatments of sides.
Facility 1:
Facility 2:
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
I 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;
a>
5 Facility 2:
o .�
For additional facilities provide all same information on a separate sheet.
Are parking areas to be used for detention? No Yes What is
maximum depth due to required design storm?
Roadside Ditches:Will culverts serve access driveways at roadside ditches?
No Yes If"yes", provide information in next two boxes.
Will 25-yr. flow pass without flowing over driveway in all cases? Yes No
Without causing flowing or standing water on public roadway? Yes No
Designs&materials comply with B-CS Technical Specifications? Yes No
Explain any"no" answers:
U)
o)
oAre culverts parallel to public roadway alignment? Yes No Explain:
U N
.
COa Creeks at Private Drives: Do private driveways, drives, or streets cross drainage
ways that serve Above-Project areas or are in public easements/ ROW?
a)Z No Yes If"yes" provide information below.
`
c How many instances? Describe location and provide information below.
Location 1:
C)
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? 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 Maior Collector Streets: Will culverts serve these types of roadways?
No Yes How many instances? For each identify the
a) location and provide the information below.
} n Instance 1:
3 Instance 2:
0 Instance 3:
0
o .2 Yes or No for the 100-year design flow: 1 2 3
o Headwater WSE 1 foot below lowest curb top?
(i) Spread of headwater within ROW or easement?
E
Is velocity limited per conditions (Table C-11)?
.N m Explain any"no"answer(s):
0 c
.0
U
0
o Minor Collector or Local Streets: Will culverts serve these types of streets?
aNo Yes How many instances? for each identify the
-0 location and provide the information below:
aa)
CI- Instance 1:
a `
N c Instance 2:
z
o Instance 3:
CD 2 c For each instance enter value, or"yes"/ no for: 1 2 3
c 0 co
Design yr. headwater WSE 1 ft. below curb top?
Q a) 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,
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
0
N
N
Is scour/erosion protection provided to ensure long term stability of culvert structural
U 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
SECTION IX
APPENDIX D - TECHNICAL DESIGN SUMMARY
Part 4__L.,-- 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?
a)
rn
73
Id
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:
Pollution Prevention 6,Li rF.�icANsia-
To Plan (SW3P)
C established for Co.4S142)C-Zr 'FP-I-TCE.
a, project construction? '115 s Ls,---( Cc,vrc,(2s:)(__
No x Yes
Special Designs—Non-Traditional Methods
Are any non-traditional methods(aquatic echosystems, wetland-type detention, natural stream
re lication, BMPs for water quality, etc.) proposed for any aspect of subject property project?
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 rnaintena ce 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
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:
2 � C-
What is the size and location of largest Design Drainage Area to which the Rational Formula
has been applied? r, t 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)
IDesign Parameters(continued)
Hydrology(continued)
In making determinations for time of concentration,was segment analysis used?
No Yes In approximately what percent of Design Drainage Areas?
As to intensity-duration-frequency and rain depth criteria for determining runoff flows, were any
criteria other than those provided in these Guidelines used? 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 O O 0
Open channels
Swale/buried conduit combination in lieu of channel
Swales
Roadside ditches and culverts serving them
Detention facilities: spillway crest and its outfall
Detention facilities: outlet and conveyance structure(s)
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) 3•(9 O ?j°T.5
Streets and Storm Drain Systems Provide the summary information outlined below:
Roughness coefficients used: For street gutters: 0. 0 (`g
For conduit type(s) 'RC.e Coefficients:O' k
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? XNO Yes Head and friction losses )C No Yes
Explain any"yes" answer:
In conduit is velocity generally increased in the downstream direction? -X Yes No
Are elevation drops provided at inlets, manholes, and junction boxes? X Yes No
Explain any"no" answers:
Are hydraulic grade lines calculated and shown for design storm? )C 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:
Tv� Dom_ ce�c� e'o,sc=. Foote (JC
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 icioritlge report
. a ;
•
ti
Noor •e
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)
IDesign 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
t 45—Cc)2-YA
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 Ill, 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 pirmits
required by any and all state and federal regulatory agencies for the proposed dr-linage
improvements have been issued or fall under applicable general permits."
(Affix Seal) -� ?
11
Licensed Professional Engineer .1.10F ` • .iU� •
"
• .F CA %#
State of Texas PE No. � RABON A`METCA T • 1
88583 ;:•c,��``
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STORMWATER DESIGN GUIDELINES Page 26 of 26 "ltlargENDIX. D:TECH. DESIGN SUMMARY
Effective February 2007 As Revised August 2012