HomeMy WebLinkAboutDrainage ReportDrainage Report
for
Oxford Court Office Building
College Station, Texas
September, 2008
Developer:
Highway 40 C&P Investments, LLC
4 714 Williams Creek Dr.
College Station, Texas 77845
(979) 777-0285
Engineer:
Civil Development, Ltd.
2033 Harvey Mitchell Parkway South
College Station, Texas 77840
(979) 764-7743
ENGINEER
Drainage Report -Executive Summary
Oxford Court Office Building
College Station, Texas
September 24, 2008
Civil Development, Ltd. -Joseph Schultz, P.E . (joe@cdlbcs.com)
P.O. Box 11 929
College Station, Texas 77842
Phone: (979) 764-7743 Fax: (979) 764-7759
OWNER/DEVELOPER
Highway 40 C&P Investments, LLC
4714 Williams Creek Dr.
College Station, TX 77845
GENERAL DESCRIPTION AND LOCATION
This project consists of the development of Lots 4&5 in Phase 1 C of the Castle Rock Subdivision in College
Station. Lots 4 & 5 are a commercial development to include an office building, utilities and infrastructure.
This development is located in Phase 1 C of the Castle Rock Subdivision. The entire site lies within the
corporate limits of the City of College Station. This development is between William D. Fitch Parkway and
the Corps of Engineers protected greenbelt area owned by the City of College Station, which is adjacent to
this tract to the north.
Area: 0.99 acres
Existing Land Use: Vacant
Proposed Land Use: Office Building
Number of Lots: 2 commercial
Drainage Basin: Spring Creek Tributary A
FEMA FIRM: #48041C0205 D, dated 2/9/2000
Floodplain: A small portion of this phase of the development lies within the floodplain.
HYDROLOGIC CHARACTERISTICS
The existing site is open land with a few scattered trees. The elevations range from 289 to 296, sloping in a
northerly direction, where runoff enters Tributary A of Spring Creek on the adjacent tract, which ultimately
flows into Spring Creek. A detention pond was constrncted on the Crowley Tract downstream of this
development.
GENERAL STORMWATERPLAN
The previous drainage plan for this development involved the installation of curb openings and a rock riprap
sh·ucture, which h·ansmit the runoff into existing drainages flowing across the adjacent tract and then into
Tributary A of Spring Creek. This structure was designed for future developed conditions, assuming a "C"
value of 0.85. With Oxford Court Office Building Development the "C" value will be less than 0.85,
therefore, no further analysis of this sh·ucture is needed.
The construction of the dumpster pad encroaches 9feet into the floodplain. The total width of the floodplain
at this location is approximately 400 feet. This encroachment will have negligible impact on the
I 00 year storm wa ter surface elevation.
The detention pond for this proposed development is located on the Crowle y Tract.
COORDlNA TION & STORMW ATEH J>J~RMJTTJNG
I ,' . .'.'., I
The project will require that a Notice of Intent be submitted to the Texas Commission for Environmental
Quality. No other pem1its are anticipated for this project.
The follo-vving items comprise this drainage report for this project:
Executive Summary
Technical Design Summary
Appendix A -Drainage Area Calculations
Appendix E -Drainage Area Map (Exhibit A)
CERTIFICATION
I, Joseph P. Schultz, Licensed Professional Engineer No. 65889, State of Texas, certify that this report for the
drainage design for the Oxford Court Office Building, was prepared by me in accordance with the provisions
of the Unified Stormwater Design Guidelines.
1';1•.:1
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 2 -Project Administration I Start (Page 2.1)
Engineering and Design Professionals Information
Engineering Firm Name and Address: Jurisdiction
C\v) \ Dtv{ \opme VL +, L-td · City: Bryan
v College Station f. 0 · \3 D x_ \ \ CJ '2..0J Date of Submittal: . Colle V\f sbdl D h 1-x 1 ·1q+i-
Lead Eng1neer's Name and Contact lnfo.(phone, e-mail, fax): Other:
j D~f.fV\ ~cVivt l 1.-i. P.(. ·?u.tt -11"f3
\ n P 6) C' cl I ki r ~ . ctJ Yh 7 '1 -4 · Y7 sq ·· fui x
Supporting Engineering I Consulting Firm(s): Other contacts:
NJ !i
Developer I Owner I Applicant Information
Phone and e-mail: Developer I Applicant Name and Address:
H ~ h V'l ot ~ ~o G-t P hw t ~+\IV\ { ~-r~ , L-L-G 711 -07..85
tt lj_ ·w, I!, t1tm 0 tvu Ii-Dr.
f n I ./M t,tz"-h VY\ -r t ... Tl<i.4.C
(olo;!./+€... crc~l~.1. C.0•"-5+rVo<...tc~"''• '-6 M
Property Owner(s) if not Developer I Applicant (& address): Phone and e-mail:
Project Identification
Development Name: 0 . .X .f {) f' d (01;1 Ylt 0 f(; f (J E:>u ;id; vi .?\
Is subject property a site project, a single-phase subdivision, or part of a m'ulti-phase subdivision?
S'i Y1 ~J.e ·-rtn g st'.L If multi-phase, subject property is phase of
Legal description of subject property (phase) or Project Area:
(see Section II, Paragraph B-3a)
L.ort 5 4 ..!( 5 /]/1 Lk {( I
(l 0 )+ ~ (l)t._ ~ V\h J. :v~·;;,.,._ !~iJ)(' 18
I
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):
Hill1 0tm D r;tch f P! \"~Cl\.~ cJ) )tit CA vd t 6 C us;\-\.t i~o c k.S\I\ bcl iv 1~;0~~
In City Limits?
Bryan: -acres.
Co llege Station: 0.11 acres.
STORMWATER DESIGN GUIDELINES
Effective February 2007
Extraterritorial Jurisdiction (acreage):
Bryan: -College Station: -
Acreage Outside ET J: --
Page 3 of 26 APPENDIX. D TECH. DESIGN SUMMARY
As Revi sed ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 2 -Project Administration I Continued (page 2.2)
Project Identification (continued)
Roadways abutting or within Project Area or Abutting tracts, platted land , or built
subject property: developments:
V\J i \l i til M p . f;1lh V\rlV'l~t \CJ ltlt s 1 l-t 12 0 c I<-
~ lt v \t-w l'l~
Named Regulatory Watercourse(s) & Waters hed(s): Tributary Basin(s):
N~~ v-1:f<"' } : J-e S \Yf--\ Y\. V\ Crue~
Plat Information For Project or Subject Property (or Phase)
Preliminary Plat File#: 01-5 D o I !:>Z.. t...i5 i '"' i::0 -1'... rVi.:tse 1r...t 1v
Final Plat File #: ..fil'ltl I Pl &1 + Date: 3 /Lt / DC/ I
Name: (1A ,,;::~ ; JJ :fZ.oclL S1;1 k>d; y iS0
l7>' ~Status and Vol/Pg: y,4 ·7q/1.c-1
If two plats, second name: File#:
Status: N /il Date:
Zoning Information For Project or Subject Property (or Phase)
Zoning Type: Air Existing 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:
N)A
Preliminary Report Required? N/jj_ Submittal Date Review Date
Review Comments Addressed? Yes --No --In Writing? When?
Compliance With Preliminary Drainage Report. Briefly describe (or attach documentation
explai ning) any deviation(s) from provisions of Prel iminary Drainage Report, if any.
r0 //t
STORMWATER DESI GN GU IDELINES
Effec1ive February 2007
Page 4 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
As Revised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 2 -Project Administration I 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? V
Yes __ No __
Coordination with Summarize need(s) & actions taken (include contacts & dates):
Brazos County
Needed? v Yes No -- --
Coordination with Summarize need(s) & actions taken (include contacts & dates):
TxDOT Needed?
Yes No . V"° --
Coordination with Summarize need(s) & actions taken (include contacts & dates):
T AMUS Needed?
Yes No ~ ----
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 i/ Yes ---
Texas Commission on 6 evi e ~,,ii fffM;+-Si vi u_ L. c; lk cf i -s t-\lt tt.kto\ 1 V\ o ND+ i ~ Envir~ental Quality
No __ Yes V IS DODD
Brazos River
Authority
No v Yes ---
STORMWATER DESIGN GUIDELINES
Effective February 2007
rl1Y'.iiUv/ ·, CUY1<SlfZ.\l\ChOY\ .s ;H r.Jv ha.. ro \,.{.
po<S\-ed ~1 Coyit(lV?ctof-'..
Page 5 of 26 APPENDIX. D TECH. DESIGN SUMMARY
As Revised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 3 -Pro12erty Characteristics I Start (Page 3.1)
Nature and Scope of Proposed Work
Existing: Land proposed for development currently used, including extent of impervious cover?
N c \'\.L -v fA.c tt1 Y\.. ..r C:~C~rj)t ~( c:._.,....~1+<, e~5c--'1 Jv-e~ .... ,
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 __ 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 --Dff i U b Vt i \di I VL)
Pro1:1osed --12-oo sF
Project -~.f6o/eiwip fni ioi1<;
Is any work planned on land that is not platted If yes, explain:
or on land for which platting is not pending?
~No --Yes
FEMA Floodplains
Is any part of subject property abutting a Named Regulatory Watercourse I No __ Yes ..,/" (Section II , Paragraph B1 ) or a tributary thereof?
Is any part of subject property in floodplain I No_ Yes v' Rate Map 'nOfl 6D"2.o5\) 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 l.../"
--
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.
"fl voe\ p )Ai n
STORMWATER DESIGN GUIDELINES
Effective February 2007
shown
Page 6 of 26
o V\ ~a le N1 A p s
APPENDIX. D TECH. DESIGN SUMMARY
As Re vised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 3 -ProQerty Characteristics I Continued (Page 3.2)
Hydrologic Attributes of Subject Property (or Phase)
Has an earlier hydrologic analysis been done for larger area including subject property?
y~ Reference the study (&date) here, and attach copy if not already in City files .
--LOM R--l.--J A -1-b {) D
Is the stormwater mana/ent 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
plan for the property in Part 4. --If property!.§. 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? ~ No --Yes
Describe them (include approximate size, volume, outfall, model, etc).
/
Any known drainage or flooding problems in areas near subject property? ~ 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) PtL-u-v 1 d-ecl A I ~~dQ
__ Detention is required. --Need must be evaluated. ~ Detention not requ1 ed.
What decision has been reached? By whom?
If the need for
Type 1 Detention How was determinati on made?
must be evaluated:
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 7 of 26 APPEN DIX. D: TECH. DESIGN SUMMARY
As Revised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 3 -Pro12erty Characteristics I Continued (Page 3.3)
Hydrologic Attributes of Subject Property (or Ptyise) (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 83-a) /
Does Project Area (project or phase) rP,ceive runoff from upland areas? ~No --Yes
Size(s) ofarea(s) in acres: 1) ? ; A-~ 2) 3) 4)
Flow Characteristics (each instance) (overland sheet,' shallow concentrated, recognizable
concentrated section(s), small creek (non-regulatory), regulatory Watercourse or tributary);
O"J -e ¥2.la n.ol f low f~b V\J tvuo \) t0 t?'I Vl + tild )ot U-V\) t~-Js
Flow determination: Outline hydrologic methods and assumptions:
\2-At i 0 Vl 0. l F4,, \AA h lTYl
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 c~anges in r~noff characteristics subject to chanLe in future? Explain
·'{e5 ""I Ph ~1~J. ~f e+J @1t l, .f 7 / 6-"'
'-E'_ W°'C).la . ) I' . C' \I J -h
'I::_ v &""'\ ..... .,,..-\-:""' cy'\ ~ L v ,;> 1 ..... ~ i.v :.( \ M C<-
Conveyance Pathways (Section II, Paragraph C2)
Must runoff from study propertv drain across low/ properties before reaching a Regulatory
Watercourse or tributary? ~ No · Yes
Describe length and characteristics of each conveyance pathway(s). Include ownership of
property(ies).
v 'I { h Y'l t( 'f, Glf { s 11.ld ~ I 0 IA) Ol vvfi ( "' iob • f>ZV1 t )'\ ~ )
CA\ e11_vJ X I~ h VL 1 f vt V ,( mJ.,.vvf · . , . . .
Ov\JvUJe__slA ·1 p of VLolj!i\ u V\ + t~uf-·1 s Ct tvr)' ~J ~v~~ ~
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 8 of 26 APPENDIX. D TECH. DESIGN SUMMARY
As Revised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMM,
Part 3 -Pro!;!erty Characteristics I Continued (Page 2
Hydrologic Attributes of Subject Property (or Phase) (continued)
Conveyance Pathways (continued)
Do drainage If yes, for what part of length? 1fo % Created by?_ V:. plat, or easements __ instrument. If instrument(s), describe their provisions.
exist for any r ~ Jv. i.,.'-,.._,I ~ t\A.. f \o--~ \ ~ W'-, \--s . part of
pathway( s)?
l;-/"G ~..,.._
No
_ ·'7Yes
Where runoff must cross lower properties, describe characteristics of abutting lower
property(ies). (Existing watercourses? Easement or Consent aquired?)
Pathway C \ +j o vO n <:; f f:.Opetz-hj
Areas ·l'Yv ~ au vYi ; V1 D f-d. f-A i 'A Ct 1)'e,-; fvud tlf. ~ .
-h)r 1 c vJJ t ~-vo~clf d fui?\, +-Ut pfit ru--. -nu. -t. x 1"" h vv:J flct-V
(). vLV1 +-ci 1 t-to Sf t?-1 \A~ c m JL --rrz 1 b . A .
Describe any built or improved drainage facilities existing near the property (culverts,
bridges, lined channels, buried conduit, swales, detention ponds, etc).
[1vl,t .exy,\-i ~ ~-t"-f:'c~ Ac vt~s P11-iv iw0c 1 \.\Ol~ C~t kJ ?-l'V\\V\. S W (OY\V .e_~ "-lAVtDff &\V\.0
~o c '?-\2-' r v-tit p v\) 0t s ~ \ oi uol to -P ~ v R. V\_ f -e..r:..o s i (}YI •
Nearby
Drainage Do any of thes~tiave hy~ogic or hydraulic influence on proposed stormwater Facilities design? __ No __ Yes If yes , explain :
(I,e -ei<.-; 5.\-;) {rf r~J..,-,._ A:>~~~~
w~ G-J p.ru..r '1.i -·sli ol.DJ c5r--
c-J (.., ~.(~v .,hl ~··~ P ~C( ( l 13 •
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 9 of 26 APPENDIX. D TECH. DESIGN SUMMARY
As Re vised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUM~
Part 4 -Drainage Conce~t and Design Parameters I Start (Page '
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.
-~ ~j_\~h V\.~ tu_f-YJ D,~\VLor V\J .trU cU&i~VLed 'y?viCK~
oltv .e \ 0 ~d C.lYVl cA I D ifVi ) . lA r l ill Vlt~ ~ 1/1; Vl of { \0 I I ~ tJh
flvw 1 n YLV Vt z1h. ?tt~ k-r n..~ V:i -f tu <-RX i ~+i n J CV\. R ~
D~l/\fnU(p Th-r-(_ ' L 4--~ u'-fJ f --l ere C\ • . -J v.V(
Discharge(s) To Lower Property(ies) (Section II, Paragraph E1)
Does project include drainage features (existing or future) proposed to become public via
platting? V No Yes Separate Instrument? V No Yes
Per Guidelines reference above, how will _t_ Establishing Easements (Scenario 1) runoff be discharged to neighboring
property(ies)? __ Pre-development Release (Scenario 2)
Combination of the two Scenarios --
Scenario 1: If easements are proposed, describe where needed, and provide status of actions
on each. (Attached Exhibit# ) C :-~ fro~+-i. fi-~ s u---A-> 1--...J--~ C"'°k._ j { Ow" I
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 DES IGN GUIDELINES
Effective February 2007
Page 10 of 26 APPENDIX. D: TECH . DESIGN SUMMARY
As Revised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage ConceQt and Design Parameters I 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 N/A in shifting runoff
between Basins or
between What design and mitigation is used to compensate for increased runoff
Watersheds? from gaining basin or watershed?
V No
rJ/A --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# )
0-e-~ D~ C>~..,)_., ) cvJ..-d ~....,_-s+r .. c ./\
~ .........
(\.(M.r ) \-\ Co
2. For Overall Project Area (type & location of facilities): (Attached Exhibit# )
e_rcw-1~1 l/G ~ ~ p~
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)?
<:'-· "O Ql rJ) c Ql c >-Are other Besiyanagement Practices for reducing stormwater pollutants proposed? Cll
o.._ __ No __ Yes Summarize type of BMP and extent of use: en c s·11+ f.&vcu_ + t+~ttrzo Wi Lit I l h Ol 5UdiVi.j en
Ql o~
1 \I If design of any runoff-handling facilities deviate from provisions of B-CS Technical
Specifications, check type facility(ies) and explain in later questions.
Ql --Detention elem ents --Conduit elements --Channel features
~ Swa les Ditches __ Inlets __ Va lley gutters __ Outfalls ----
--Culvert features __ Bridges Other
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 11 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
As Revised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Conce~t and Design Parameters I 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)? v 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? V Yes No, then summarize th e difference(s):
Identify whether each of the types of drainage features listed below are included, extent of use,
and general characteristics.
Typical shape? I Surfaces?
C'-·
"O Q) en Steepest side slopes: Usual front slopes: Usual back slopes: en :::i Q)
en >-
Q)
I ..c Flow line slopes: least Typical distance from travelway: . .g
"O typical (Attached Exhibit # )
Q) greatest
"O 0 "(jj z
!~ Are longitudinal culvert ends in compliance with B-CS Standard Specifications?
Yes No, then explain: <(
en At intel'Sections or otherwise, do valley gutters cross arterial or collector streets?
~ Q) No Yes If yes explain: ~ C'· >---u "O I ./\J /A ..c Q) ~ en ·-:::i 3: .._ I Are V?lley gutters proposed to cross any street away from an intersection? en Ql W~o No Yes Explain : (number of locations?) ~ oiz ----]]jl
N/f\
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 12 of 26 APPENDIX. D TECH. DESIGN SUMMA RY
As Revised ____ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage ConceQt and Design Parameters I 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.
C'-·
"'O Q) en Will inlet size and placement prevent exceeding allowable water spread for 10-year :::J
'-2 design storm throughout site (or phase)? --Yes --No If no , explain.
5
Ol
"'O ~ c "'O ro Q.l Sag curves: Are inlets placed at low points? Yes No Are inlets and .o E ----
'-·-conduit sized to prevent 100-year stormflow from ponding at greater than 24 inches? ::::i-<J c Yes No Explain "no" answers. 0 L: <J ----.-=:: -3
en Q)
!!! u;
Q) Will 100-yr stormflow be contained in combination of ROW and buried conduit on -d: whole length of all streets? Yes No If no , describe where and why. ----
Do designs for curb, gutter, and in lets comply with 8-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.
C'-· "'O Pipe run s between system I Typical Q) Longest en en access points (feet): :::J Q)
E >-~I Are junction boxes used at each bend? --Yes --No If not, explain where
and why. en
c j ~1
Are downstream soffits at or below upstream soffits? Least am ount th at hydraulic en grade line is below gutter line (/) Yes No __ If not, explain where and why: ---(system-wide):
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 13 of 26 APPENDIX. D TECH. DESIGN SUMMARY
As Revised ____ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Concept and Design Parameters I Continued (Page 4.5)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
Vi'
Q) u c ro Ul c
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?
2) Watercourse (or system), velocity, and angle?
3) Watercourse (or system), velocity, and angle?
For each outfall above, what measures are taken to prevent erosion or scour of
receiving and all facilities at juncture?
1)
2)
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):
Flow line slopes (minimum and maximum):
Outfall characteristics for each (velocity, convergent angle, & end treatment).
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
Effective February 2007
Page 14 of 26 APPENDIX. D TECH. DESIGN SUMMARY
As Revised ____ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Conce~t and Design Parameters I Continued (Page 4.6)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
en Are road side ditches used? ~No __ Yes If so, provide the following:
Q) Is 25-year flow contained with 6 inches of freeboard throughout? __ Yes --No ..c _ .g Are top of banks separated from road shoulders 2 feet or more? __ Yes --No
0 Are all ditch sections trapezoidal and at least 1.5 feet deep? Yes No Q) ----
""Cl For any "no" answers provide location(s) and explain: "(jj
""Cl rn 0 n::
If conduit is beneath a swale, provide the following information (each instance).
Insta nce 1 Describe general location, approximate length:
en
Q) >-
lw Is 100-year design flow contained in conduit/swale com bination? --Yes --No
If "no" explain:
c
0 rn z u:; Space for 100-year storm flow? ROW Easement Width ~1 ~ Swale Surface type, minimum Conduit Type and size, minimum and maximum
0 and maximum slopes: slopes, design storm:
C'-· :E
en ""Cl
a; ""Cl rn c >-Inlets Describe how conduit is loaded (from streets/storm drains, inlets by type): c rn c
.c rn
l) '-0 c -Q) c o._ 0 0 ~ Access Describe how maintenance access is provided (to swale, into conduit): -0 E ::::J
.!!! J2 c c Q)
""Cl E Instance 2 Describe general location, approximate length: Q) rn (fJ (fJ ::::J
en Q)
c ""Cl
0 ·5 Is 100-year design fl ow contained in conduit/swale combination? Yes No ~ e ----
c o._ If "no" explain:
:.0 Q:J
E Q)
0 .c Space for 100-year storm flow? ROW Easement Width l) en
·-Q) Swale Surface type, minimum Conduit Type and size, minimum and maximum ::::J ~ ""Cl and maximum slopes: slopes, design storm : c rn 0 o._
l) Q)
:ili en Inlets Describe how conduit is loaded (from streets/storm drains, inlets by type): c rn ~ 3 en
Q)
4: Access Describe how maintenance access is provided (to swale, into conduit):
STORMWATER DESIGN GUIDELI NES
Effective February 2007
Page 15 of 26 APP ENDIX. D TECH. DESIGN SUMMARY
As Revised ____ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Concept and Design Parameters I Continued (Page 4. 7)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued)
c
.!!!
E ~ 0 w ~
If "yes" provide the following information for each instance:
Instance 1 Describe general location, approximate length, surfacing:
15 cn Is 100-year design flow contained in swale? __ Yes __ No Is swale wholly
c a.> within drainage ROW? __ Yes __ No Explain "no" answers:
.; >-I f---------------------------------~ ~ Access Describe how maintenance access is provide:
,_ 0
1~1 1----------------------------------~ ~ Instance 2 Describe general location, approximate length, surfacing:
a.> ·;::::: C"· ::i Cf)
..c c
::; a.> o E
£a.>
"§: ~ a.> Cf) ,_
a.> 0
3 s
Cf) 0
0:: 5: .~
('·
..c ::i c.
-0 c ~ .!!! 0 c. c. x e w c.
Cf) Cf) c a.> a.> >-
I I c. E o l~I
0
Is 100-year design flow contained in swale? __ Yes __ No Is swale wholly
within drainage ROW? __ Yes __ No Explain "no" answers:
Access Describe how maintenance access is provided:
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.
Will design replicate natural channel? __ Yes __ No If "no", for each instance
describe section shape & area, flow line slope (min. & max.), surfaces, and 100-year
design flow, and amount of freeboard :
Instance 1:
Instance 2:
Instance 3:
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 16 of 26 APPENDIX. D TECH. DESIGN SUMMARY
As Revised ____ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Concef;!t and Design Parameters I 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 "ves" 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 .
..-.. -c Q)
:::::l c: I c Watercourses {and tributaries}: Aside from fringe changes, are Regulatory 0 Watercourses proposed to be altered? ~No __ Yes Explain below. ~
(/l c Submit full report describing proposed changes to Regulatory Watercourses. Address
Q) existing and proposed section size and shape, surfaces, alignment, flow line changes, E Q) length affected, and capacity, and provide full documentation of analysis procedures > 0 and data. Is full report submitted? Yes No If "no" explain: L.. Cl. --E
a; l~ IA-c: c: I ro All Pro12osed 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.
N/A
Will 100-year flow be contained with one foot of freeboard? --Yes --No If
not, identify location and explain:
N fA
Are ROW I easements sized to contain channel and required maintenance space?
--Yes --No If not, identify location(s) and explain:
NIA
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 17 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
As Revised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Conce12t and Design Parameters I Continued (Page 4.9)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued) C \2 D 1\J \-<.-v\ , b<,·~ -4'\ti~N-{
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 (1 O 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:
en Q) >-
I For each facility what is 25-yr design Q, and design of outlet structure?
0 Facility 1: z ~ Facility 2:
Do outlets and spillways discharge into a public facility in easement or ROW?
C'-· Facility 1: __ Yes No Facility 2: Yes No "O ------
Q) If "no" explain: en 0 0.. e 0..
en For each , what is velocity of 25-yr design discharge at outlet? & at spillway? Q)
:E Facility 1: & Facility 2: & ·u ro Are energy dissipation measures used? No Yes Describe type and lJ... ----c location: 0 ~ Q)
(i)
0
Q) .< 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
Effective February 2007
Page 18 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
As Revised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Conce1;2t and Design Parameters I 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":
Cf)
Facility 1;
a.> :;::;
=~ ~a.> Facility 2: LL ::i c C:;:;
0 c :;::::; 0 c (.} a.i~ w For additional facilities provide all same information on a separate sheet. 0
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 :
C'-· Cf) en c ·u;
Are culverts parallel to public roadway alignment? Yes No Explain : Cf)
0 -- --.... Cf) (.}
a.> a.> >-rn
I > ·;:: Creeks at Private Drives: Do private driveways, drives, or streets cross drainage a. rn ways that serve Above-Project areas or are in public easements/ ROW?
"O 0 No Yes If "yes" provide information below. !~1 ----
How many instances? Describe location and provide information below.
a.> Location 1: .2: ::i (.}
a.> 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 1 OD-year flow?
For more instances describe locati on and same information on separate sheet.
STORMWATER DESIGN GUIDELINES
Effective Fe bruary 2007
Page 19 of 26 APPENDIX. D TECH. DESIGN SUMMARY
As Revised ____ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Conce~t and Design Parameters I Conti nued (Page 4.11 )
Stormwater Management Concept (continued)
With in Or Serving Subject Property (Phase, or Site) (continued)
Named Regulatort Watercourses {&Tributaries}: Are culverts proposed on these
facilities? --No __ Yes, then provide full report documenting assumptions,
criteria, an alysis, computer programs, and study fin ding s 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? Qi
Q) No Yes How many instances? For each identify the ..c Vl ----
Q) location and provide the information below.
vi -ro Instance 1: Q) .__
>-~ I ~ Instance 2:
Instance 3: c a a~ Yes or No for the 1 OD-year design fl ow: 1 2 3 z E
~1 ~ Headwater WSE 1 foot below lowest curb top?
Spread of headwater within ROW or easement?
E C'· ro Is velocity limited per condition s (Table C-11)? Vl Vl gi ""C Explai n any "no" answer(s): ·-c ~ ro a c .__ a
(.):;:::;
>-ro ro u 3 _Q
""C Q) ro ..c Minor Collector or Local Streets: Will culverts serve these types of streets? a ·-.__ .__
(.) (.) No Yes How many instances? for each identify the ·-Vl -Q) ----"§ ""C location and provide the information below: a. Q)
-a. Instance 1: ro c
""C >. Instance 2: Q) c ~ ro -Instance 3: .!!l a
.__ Vl
Q) Q) z (.) For each instance enter value, or "yes" I "no" for: 1 2 3 :::Jc u ro Design yr. headwater WSE 1 ft. below curb top? Q) (ii
-< c
~ 100-yr. max. depth at street crown 2 feet or less?
a Product of velocity (fps) & depth at crown (ft) = ? E .__ g Is velocity limited per conditions (Table C-11)?
Limit of down stream analy sis (feet)?
Explain any "no" answers:
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 20 of 26 APPE NDIX. D TECH. DESIGN SUMMARY
As Revised ____ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Conce1;2t and Design Parameters I 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:
::0 Are flumes or conduit to discharge into or near surfaced approaches to culvert ends? <V ::::i No Yes If "yes" identify location(s), describe outfall design treatment(s): c ----~ 0 ~
en t <V .2: ::::i 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 8-CS Tech. Specifications?
--Yes --No If not, explain in Specia l Design Section of this Part.
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 21 of 26 APPENDIX. D TECH. DESIGN SUMMARY
As Revised ____ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Conce12t and Design Parameters I 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? --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.> Ol
"O ·;::: ro
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
Yes No provided? ----If "no" explain:
Is a Stormwater Provide a general description of planned technique-:::
.~ Pollution Prevention S.ee (,/-...-h-:-"' ?t0t n l 'S ~t.?-'> ro Plan (SW3P) :J a established for ok c B'Yl s t~tA.c t1 1:>n \:) ~ t\ \N I VLvj S L.. project construction? Q.) rn __ No ·/"Yes s
Special Designs -Non-Traditional Methods
Are any non-traditional methods (aquatic echosystems, wetland-type detention, natural stream
re~ation , 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. Rep ort must substantiate th at stormwater management objectives will not
be compro mised, and that maintenance cost wi ll not exceed those of traditiona l design
solution (s). Is report provided?
N/ f\
STORMWATER DESIGN GUIDELI NES
Effective Februa ry 2007
Yes ----
Page 22 of 26
No If "no" explain:
APPENDIX. D: TE CH. DESIGN SUMMARY
As Revised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage ConceQt and Design Parameters I Continued (Page 4.14)
Stormwater Management Concept (continued)
Within Or Serving Subject Property (Phase, or Site) (continued) tJ / J\
Special Designs -Deviation From 8-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)
I
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
v Yes No Is a map(s) showing all Design Drainage Areas provided? ----
Briefly summarize the range of applications made of the Rational Formula:
~V\. h VYJ(l \ F of-m 1A.lt'I. vl~ 17( to\'Z-,,f_x l ~ti Vlj
t\A.~b 017{M'1Vl'1 t>-es \,,,,JY\ .
What is the size and location of largest Design Drainage Area to which the Rational Formula
has been applied ? l . '-\ 1.---acres Location (o r identifier):
STORMWATER DES IGN GUIDELINES
Effective February 2007
Page 23 of 26 APPENDIX. D TECH. DESIGN SUMMARY
As Revised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Conce~t and Design Parameters J Continued (Page 4.15)
Design Parameters (continued)
Hydrology (continued)
ln~king deteITTiinations 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 appli ed:
-¥ Tu::.. JOmiV\
\A. t,{ cJ1 i Y'\ fi \!\_ C<. .v-
i 13 + \ v [, tA \ l'\.a.~ ~L po tz-+-fo(Z-th; 5
IA.-e.t.t\
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
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)
Streets and Storm Drain Systems Provide the summ ary information outlined below:
Roughness coefficients used:
For conduit type(s)
STORMWATER DESIGN GUIDELINES
Effective February 2007
For street gutters:
Page 24 of 26
Coefficients:
APPENDIX. D TECH . DESIGN SUMMARY
As Revised ____ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage ConceQt and Design Parameters I Continued (Page 4.16)
Design Parameters (continued)
Hydraulics (continued)
Street and Storm Drain Systems (continued)
For the following, are assumptions other than allowable per Guid elines?
Inlet coefficients? No Yes Head and friction losses No Yes --------
Explain any "yes" answer:
N/A
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:
N (A:
Are hydraulic grade lines calculated and shown for design storm? --Yes --No
For 100-year flow conditions? --Yes --No Explain any "no" answers:
N/~
What tailwater conditions were assumed at outfall point(s) of the storm drain system? Identify
each location and explain:
N}A
Open Channels If a HEC analysis is utilized, does it follow Sec Vl.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
Effective February 2007
Page 25 of 26 APPENDIX. D TECH. DESIGN SUMMARY
As Revised ___ _
SECTION IX
APPENDIX D -TECHNICAL DESIGN SUMMARY
Part 4 -Drainage Conce12t and Design Parameters I Continued (Page 4.17)
Design Parameters (continued)
Computer Software
What computer software has been used in the ana lysis 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 pub lisher
\).fS i ~ YI \/\\ [.{ ~ ? f. y fD {L1v\.UA i Y\ ?fZ-eV (DLA S
12--e p o ~.-\ (Cll51 \{ )2 oc \c.. '.?h tt« l 6t )G J
'
Part 5 -Plans and S12ecifications
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 informatio n here:
\)-es\ °J \r\ l O'YY) 'P \ i -£ '.J V\) \ -\ \;\ 'j\l\.io\.{ l\V\l)
Attestation
Provide attestation to the accuracy and completeness of the foregoing 6 Parts of this Technical
Desiqn Summary Drainaqe Report by signing and sealing below.
"This report (plan) for the drainage design of the development named in Part B wa s prepared
by me (or under my supervision) in accordance with provisions of the Bryan/Co llege 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 th.e ,,eroposed drainage
improve ~nls have been i~dec applicable general:f!"!lit"f!J'/""'}'<\\ hJAP .:-.. ~ .... "" 11
(Affix ~GJ>_ •• ···*··· .. ~0.., Oe ... '* .. ·. * ~~ . I?*: ·*~
Licensed'&rofeJsional Engineer i···josEP~tfi'. .. sC"t=iLi1Tt:J
~···························· .. ··(i:. il. l~ ~I I ~~-.. ssaa9 <) l&J State of Texas PE No. () r 3 ,.~ 1~0,;·~fGtsTt:.~~/~ .#' IA'.~;. •• -•• r,; g
"ij . ->.::J'f ~-~. -
STORMWATER DESIGN GUIDELINES
Effective February 2007
Page 26 of 26 APPENDIX. D: TECH. DESIGN SUMMARY
As Revised ----
Castle Rock Subdivision
Phases 1B
Drainage Area Calculations
Area
Area No. (acres)
A1 I Ai
261A 1.42 I
The Rational Method:
Q =CIA
Q = Flow (cfs)
A= Area (acres)
C = Runoff Coeff.
I = Rainfall Intensity (in/hr)
Brazos County:
5 year storm
b = 76
d = 8.5
e = 0.785
I AJ
I
Oxford Court Office Building
I Total
I 1.42
c
tc
C1 C2 C3 Crotal (min)
0.85 0.85 10.0
I = b I (tc+d)e
tc =Time of concentration (min)
C1 = 0.85 = Commercial Area
C1 = 0.35 = Undeveloped Area
5 year storm
Is Os
(in/hr) (cfs)
7.693 9.29
C2 = 0.90 = Impervious Area (pavement)
C3 = 0.55 = Residential Area
10 year storm 25 year storm 50 year storm
b = 80 b = 89 b = 98
d = 8.5 d = 8.5 d = 8.5
e = 0 .76 e = 0.75 e = 0.745
"C" Value Calculation for Area 261A
Area "C" Valu e (Acres)
Paved Area 0.50 0.95 0.48
Building 0.1 0 0.95 0.10
Landscape Area 0.20 0.45 0.09
Undisturbed Area 0.62 0.35 0.22
Total Area 1.42 Weighted "C" Value 0.62
10 year storm 25 year storm
110 010 l2s
(in/hr) (cfs) (in/hr)
8.635 10.42 9.861
tc = L/(V*60)
L = Length (ft)
V =Velocity (ft/sec)
100 year storm
b = 96
d = 8.0
e = 0.730
02s
(cfs)
11.90
50 year storm 1 00 year storm
lso Oso 1100 0 100
(in/hr) (cfs) (in/hr) (cfs)
11.148 13.46 11 .639 14.05