HomeMy WebLinkAbout32 Development Permit 01-14 Add Parking Covenant Family Church 4010 HarveyC$·w
( ('l If • '-.1 :\flU'-
DEVELOPMENT PERMIT
PERMIT NO . 100014
DP-COVENANT FAMILY CH-ADD PKING
FOR AREAS OUTSIDE THE SPECIAL FLOOD HAZARD AREA
RE : CHAPTER 13 OF THE COLLEGE STATION CITY CODE
SITE LEGAL DESCRIPTION:
COVENANT FAMILY CHURCH
DA TE OF ISSUE: JUNE 28, 2001
OWNER:
POST OAK CHRISTIAN CENTER INC
C/O DANIEL GREEN-PASTOR
COLLEGE STATION , TX 77842-0152
SITE ADDRESS:
4010 HARVEY RD
DRAINAGE BASIN:
UNAMEDCHANNELTOCC
v ALID FOR 12 MONms
CONTRACTOR:
TYPE OF DEVELOPMENT: PARKING LOT AND DETENTION
SPECIAL CONDITIONS:
Temporary berm approved.
All construction must be in compliance with the approved construction plans .
All trees must be barricaded, as shown on plans , prior to any construction . Any trees not barricaded will not count towards
landscaping points . Barricades must be l' per caliper inch of the tree diameter.
The Contractor shall take all necessary precautions to prevent silt and debris from leaving the immediate construction site in
accordance with the approved erosion control plan as well as the City of College Station Drainage Policy and Design
Criteria. The Owner and/or Contractor shall assure that all disturbed areas are sodden and establishment of vegetation
occurs prior to removal of any silt fencing or hay bales used for temporary erosion control. The Owner and/or Contractor
shall also insure that any disturbed vegetation be returned to its original condition, placement and state . The Owner and/or
Contractor shall be responsible for any damage to adjacent properties , city streets or infrastructure due to heavy machinery
and/or equipment as well as erosion, siltation or sedimentation resulting from the permitted work.
Any trees required to be protected by ordinance or as part of the landscape plan must be completely fenced before any
operations of this permit can begin.
In accordance with Chapter 13 of the Code of Ordinances of the City of College Station, measures shall be taken to insure
that debris from construction, erosion , and sedimentation shall not be deposited in city streets, or existing drainage fac ilities .
I hereby grant this permit for development of an area outside the special flood hazard area . All development shall be in
accordance with the plans and specifications submitted to and approved by the City Engineer in the development permit
application forthe above named project and all of the codes and ordinances of the City of College Station that apply.
If it is determined the prescribed erosion control measures are ineffective to retain all sediment ons ite, it is the contractors
responsibility to implement measures that will meet City, State and Federal requirements .
Date
~1d°'~I
Dat
~ .1 9:, 2"0 I
c
s
c I
Engineenng & Environmental
Consultants , Inc .
Ma y 2 1, 2001
Mr. S pe ncer Thomp so n
C ity of College Station Deve lo pm ent Serv ices
I I 0 I Texas A venu e
Co ll ege Stat io n, TX 77 840
Re: Drain age Report fo r Covenant Fam il y C hur c h (Harvey Hill s ide S ubdi v is io n)
Co ll ege Station (Brazos Cou nty), Texas
Dear Mr. T ho mp so n:
CSC Eng in ee rin g & Environm e ntal Co ns ult a nt s, In c. (CSC) is pleased to s ubmit the e nc losed drain age
reports (four co pi es) fo r the Cove nant Family C hu rch deve lopme nt. These repo rt s are s ubmitted on beha lf
of th e Cove nan t Fa mil y C hur c h in co mpli a nce with curre nt City of Co ll ege Stat io n draina ge
req uir ements. The s it e is locate d at 40 I 0 Harv ey Road in College Stat io n, Texas . As previou s ly
documented in "Drai na ge Repo rt for Cove na nt Family C hurch , Lots 22 & 23 , Bl ock I Harvey Hill s id e
Subdi vis io n ( 1.03 acres), May 3, 1999" pre pa red by Klin g Eng in ee rin g & Survey in g, the 5.04-acre s it e is
o nl y pa rtiall y s itu ated w ithin the c ity lim its of Co ll ege Stati on. However, the owne r has e lected to pro v id e
detenti o n fo r futur e deve lopment in acco rdance wit h th e d rainage po li cy of the C ity of Co ll ege Stat io n.
In fo rm ation re lative to futur e deve lopment is di sc ussed in detailed in the enc losed reports. These reports
are bei ng s ubmitt ed fo r rev iew by the C ity of Co ll ege Stat ion in accordance w ith the pro vis ions of the
C ity of Co lle ge Station Drain age Po li cy and Design Sta nd ards Manual.
Plea se contact eithe r of the und ers igned indi vidua ls at 778-28 10 if yo u have any questions or need
ad diti ona l info rmation co ncerning this matt er.
Res pectfully ,
W.R . C ull e n, P.E.
Project Ma nager
M. Frederick Con lin , P.E .
Se ni or Eng in eer
WR C:mf
Via Hand Delivery
cc: Fami ly Covenant Chur ch
3407 Tabor Road
Bryan, Texas 77808
Phone (979) 778-2810
Fax(979)778-0820
,
oven a1i t
Family Church
"Success Begins On Sunday "
June 13, 2001
Danny & Janet Green
Pastors
Spencer Thompson ·
City of College Station Development Services
1101 Texas Ave. ·
College Station, TX 77840
RE: Covenant Family Church Detention Pond
I
Dear Spencer,
As we discussed, total planned construction for Covenant Family Church will be completed in
three phases. )
Phase One will be two bqys of concr(!te paving, apptoximately 16, 000 sq. ft., which will drain to
-storm inleis that dump into the proposed detention pond. This paving is less t~an 25% of total
planned construction. Phase Two will be an additional 16, 000 sq. ft. of concrete paving surface
draining to the detention pond. The final phase will be d new sanctuary building oj
approximately 30, 000 sq. ft. with an additional drive and parking of appro,ximately 10, 000 sq. ft.
The time frame for Phase One and Two construction f1as not been determinf!d. Therefore , it is
requested that the detention pond as designed be scaled down to accommodate only the water
runoff created by Phase One pavi~g., Specifically, our consultant (CSC Engineering and
Environmental Consultant, Inc.) indicates that ~he increase runoff attributed to the Phase I
construction will be on the order of 3.0 c.fs. As a result, we propose to construct a temporary
earthen berm in place of the proposed concrete wall. The berm will be appr(Jximately 18-inch
high and have an 18-inch outlet structure to control discharge to the 36-inch c.m.p . beneath
Marcy Lane. During the construction of Phase Two the earthen berm will be removed and ·
. replaced with a permanent concrete wall as indicated in our previous submittal to the City of
College., Station. '
If you need any additional information, contact me at your convenience.
Sincerely,
COVENANT FAMILY CHURCH
' .
Construction Consultant
DJR!nr
40/0 Harve y Road (Hwy 30 ) PO. Box 10152 College Stati on, Texas 77842
Office (979) 774-1269 Fax (979) 776 -5498 E-mai l: Gre enCFC@ao l.com www.covenant-family -church.org
'I
KLING ENGINEERING & SURVEYING
Consulting Engineers • Land Surveyors
4103 Teus Avenue, Suite 212
Bryan, Teus 77802
Poat OfYlce Box 4234
B..J. Kling, P.E., R.P.LS.
S.M. Kling, R.P.LS.
FEBRUARY 23, 2001
TO:
FROM:
Ted Mayo, P.E .
B.J. Kling, P.E.
Stacy King
Telephone 97918464»212
Fax 979/846-8252
Bryan, Teus 77805
RE: Family Covenant -Detention Requirements for Additional Parking
PURPOSE
Family Covenant Church has proposed to build two additional parking bays crossing Lots 22
and 23, to build one future parking bay crossing Lots 23 and 24 and to modify the existing
parking bay adjacent to Marcy Lane . These lots are within the Harvey Hillside Subdivision in
College Station and Brazos County. The construction of the parking bays requires the removal
of the existing buildings located on Lots 23 and 24 . The purpose of this letter is to document
the handling of the increased runoff from the three additional parking bays .
HISTORY
The Church is located along the south side of State Highway 30 near the intersection of Marcy
Lane . The majority of the property is located in Brazos County and the remainder ls located
in College Station. In 1999 the church constructed two parking bays on the portion of the
property located in College Station with the approval of the City. The runoff from the two parking
bays was directed to a storm sewer system which discharged into a creek located on the
portion of the property in Brazos County. No detention was provided since the discharge was
in Brazos County and the downstream cross-sections were determined to have capacity for the
increase in runoff. (Refer to the 1999 report titled "Drainage Report for Covenant Family
Church , Lots 22 & 23, Block 1" and Appendix 6: "Hydraulic Calculationsn in the 1999 report for
the capacity of the downstream cross-sections.) The result of this was a reduction in the
predeveloped runoff flowing into the drainage ditch along State Highway 30 in College Station ,
a net decrease of 4.52 cfs for the hundred year storm event. (Refer to Appendix 5: Hydrologic
Calculations in the 1999 report for the predeveloped and postdeveloped runoff calculations from
the year 1999.)
DRAINAGE
Notes: 1. All runoff quantities are for the 100 year storm event.
2 ; Sample Calculations attached.
Runoff Into Brazos County
The runoff from the two proposed parking bays is directed into the storm sewer system
constructed in 1999 whose outlet is in the creek located in Brazos County. The full flow
capacity of the existing storm sewer system is 21. 92 cfs . The first grate inlet in the storm
sewer system has capacity for 6 .22 cfs at a depth of 0.20 ft and the second grate inlet
has capacity for 16.58 cfs at a depth of 0.80 ft . The existing runoff into the storm sewer
system is 10.35 cfs, 6 .22 cfs flows to the system via the first inlet and the remaining 4 .13
cfs overflows into the second inlet.
The runoff from the Proposed Parking Bay 1 and the surrounding landscaped areas
contributes 1. 91 cfs to the existing storm sewer system . This runoff bypasses the first
grate inlet and overflows into the second inlet. The runoff from the Proposed Parking
Bay 2 and the surrounding landscaped areas contributes 2 . 04 cfs to the existing storm
sewer system . This runoff flows directly to the second inlet.
The total runoff that flows into the second grate inlet including existihg and proposed
runoff is 8. 08 cfs at a depth of 0.34 ft. The total runoff that flows into the existing storm
sewer system including the existing and proposed runoff is 14.30 cfs which is less than
the capacity of the system (21.92 cfs}.
Runoff Into College Station
The runoff from the Future Parking Bay is directed into the ditch along State Highway 30
located in College Station. The increase in runoff from the Future Parking Bay and
additional paving in the existing parking bay is 1.41 cfs. The decrease in the
predeveloped runoff as mentioned previously allows for an increase in runoff of 4.52 cfs
to the ditch per the 1999 report. Therefore, the postdeveloped runoff from the Future
Parking Bay is less than the predeveloped runoff by 3.11 cfs.
-II
0
cP
0
II
0
~ I
0
8
II
••
.J) -
('
•I
9
_J
(fJ
II
I\ -0
~
i-'
0
0 I\ --
II
0
U1
oP
I \
0
11
£' ,,
0
_J
0
0
June 1, 2001
CITY OF COLLEGE STATION
DEVELOPMENT SERVICES
1101 Texas Avenue South, PO Box 9960
College Station, Texas 77842
Phone (979) 764-3570 I Fax (979) 764-3496
MEMORANDUM
TO: Covenant Family Church, Via fax 776-5498
FROM: Bridgette George, Asst. Development Review Manager
PROJECT: Covenant Family Church Parking Lot-Additional Parking
Staff reviewed the above-mentioned site plan as requested. The following page is a list
of staff review comments detailing items that need to be addressed. Please address
the comments and submit the following information by Monday at 10:00 a .m. for further
staff review:
Two (2) copies of the revised construction plans; and,
Modified Puls routing spreadhsheet.
If you have any questions or need additional information, please call me at 764-3570.
Attachments : Staff review comments
cc: CSC Engineering & Environmental Consultants, Inc. l/l lA-fd* 1/3 '"'Odd-a
Case file #01-14
Home of Texas A&M University
ENGINEERING REVIEW
COMMENTS No. 1
DP-COVENANT FAMILY CH-ADD PKING (01 00100014)
1. I need to review a complete routing of stormwater through the proposed pond and
through the 36" CMP. There is an area to the west that drains through here. Please
include a drainage area map.
2. Please show what call-outs in hex boxes refer to, Sheet C-1 . Many of the numbers
did not show up in the printing process . Some of the information may have been
misread.
3. Will the parking lot storage depth of 8" be exceeded when the new lots drain into the
existing grates? Please show calculations.
4. Please explain discharge calculations for 36" CMP. What is the flow line elevation
and slope?
5. Please include Modified Puls routing spreadsheet.
Reviewed by: Spencer Thompson Date: May 29, 2001
Home of Texas A&M University
SITE PLAN APPLICATION
MINIMUM SUBMITTAL REQUIREMENTS
'v Site plan application completed in full .
'I' $100.00 Application Fee.
__ $100.00 Development Permit Application Fee.
or. ()1 -1 lf;
1:UA.. $300.00 Public Infrastructure Inspection Fee if applicable. (Ibis fee is payable if construction of a public
waterline, sewerline, sidewalk, street or drainage facilities is involved.)
"'J Ten ( 10) folded copies of site plan.
~ A copy of the attached site plan checklist with all items checked off or a brief explanation as to why they are not
checked off.
APPLICATION DATA
NAMEOFPROJECT Site Plan for Additional Parkin g
ADDRESS 4010 Harvey Road .
LEGALDESCRIPTION Lot 22,23 & 24, Harvey Hillside Subdivision, Vol 264, Pg 484
APPLICANT (Primary Contact for the Project):
Name Covenant Family Church
StreetAddress 4010 Harvey Road
State TX Zip Code 77842
Phone Number ( 979) 77 4-1269
PROPERlY OWNER'S INFORMATION:
Name Same as applicant
City College Station
E-Mail Address -------------
Fax Number -----------------
Street Address City
---------------~ --------------
State Zip Code _____ E-Mail Address -------------
Phone Number Fax Number -------------' -----------------
ARCIIlTECT OR ENGINEER'S INFORMATION:
Name Kling Engineering and Surveying
StreetAddress 4103 Texas Ave. Suite 212 City __ B_r_y_an _________ _
State TX Zip Code 77802 E-Mail Address stacy@kl i ngen g . com
Phone Number ( 979) 8 46-8612 FaxNumber (97 9 ) 8 46-8 252
OTIIER CONTACTS (Please specify type of contact, i.e. project manager, potential buyer, local contact, etc.)
Name N/A ----------------------------------
StreetAddress ---------------~ City------------~
State Zip Code _____ E-Mail Address ------------
Phone Number Fax Number ________________ _
SITE PLAN APPLICATION
SITEAPP.DOC OJn.5199
CURRENT ZONING ~-0 -Agri cultura 1 Open
PRESENT USE OF PROPER1Y Chu~ch and ,parkinq
PROPOSED USE OF PROPER1Y Parkin
VARIANCE(S) REQUESTED AND REASON(S) _;..:...no:....;..n;..:;.e _______________ _
#OF PARKING SPACES REQUIRED __ 1_55 __
Not A licable -Proposed Parking Only
0 MULTI-FAMILY RESIDENTIAL
Total Acreage ___ _
Floodplain Acreage __
Housing Units ----
# of 1 Bedroom Units
# of 2 Bedroom Units
# of 3 Bedroom Units
# of 4 Bedroom Units
FOR 2 BEDROOM UNITS ONLY
__ # Bedrooms ~ 132 sq. ft.
__ # Bedrooms < 132 sq. ft.
#OF PARKING SPACES PROVIDED 255
0 COMMERCIAL
Total Acreage
Building Square Feet ___ _
Floodplain Acreage ----
The applicant has prepared this application and certifies that the facts stated herein and exhibits attached
hereto are tru co"ect.
er, Agent or Applicant
SITE PLAN APPLICATION
SITF.APP rYV' n'tn~/QQ
'23 &6 2od I
Date
2 of3
SUPPLEMENTAL DEVELOPMENT PERMIT INFORMATION
.\pplication is hereby made for the following development specific waterway alterations:
ACKNOWLEDGMENTS:
L Jonat han A. Poe design engineer/owner, hereby acknowledge or affirm that:
The information and conclusions contained in the above plans and supporting documents comply with the current requirements of
the City of College Station, Texas City Code, Chapter 13 and its associated Drainage Policy and Design Standards.
As a co · tion of approval of this permit application, I agree to construct the improvements proposed in this application according to
t11Cit'<llOc$llllllC:nts and the requirements o hapter 13 of the College Station City Code.
Contractor
CERTIFICATIONS: (for proposed alterations within designated flood hazard areas.)
A L certify that any nonresidential structure on or proposed to be on this site as part
of this application is designated to prevent damage to the structure or its contents as a result of flooding from the 100 year storm.
Engineer Date
B. L certify that the finished floor elevation of the lowest floor, including any
basement, of any residential structure, proposed as part of this application is at or above the base flood elevation established in the
latest Federal Insurance Administration Flood Ha7.ard Study and maps, as amended.
Engineer Date
C . L certify that the alterations or development covered by this permit shall not
diminish the flood-Qlll)'ing capacity of the waterway adjoining or crossing this permitted site and that such alterations or
development are consistent with requirements of the City of College Station City Code, Chapter 13 ·concerning encroachments of
floodways and of floodway fringes.
Engineer Date
D . L do certify that the proposed alterations do not raise the level of the 100 year
flood above elevation established in the latest Federal Insurance Administration Flood Ha7.ard Study.
Engineer Date
Conditions or comments as part of approval:---------------------------
.
In accordance with Chapter 13 of the Code of Ordinances of the City of College Station, measures shall be taken to insure that debris
from construction, erosion, and sedimentation shall not be deposited in city streets, or existing drainage facilities .
' hereby grant this permit for development All development shall be in accordance with the plans and specifications submitted to
and approved by the City Engineer for the above named project All of the applicable codes and ordinances of the City of College
Station shall apply.
SITE PLAN APPLICATION
SITEAPP.DOC 03/25199
3of3
W. R. Cu ll en, P.E .
Pr oj ect Ma nage r
R ~v, -wEIJ FOR FI LE
t COMPLI
JUN 21 20
ENGINEERING ~ ~
DRAINAGE REPORT FOR
COVENANT FAMILY CHURCH (5.04
ACRES), HARVEY HILLSIDE SUBDIVISION
COLLEGE STATION (BRAZOS COUNTY),
TEXAS
Pr epared for
Cove nant Fami ly Chu rc h
40 I 0 Ha rvey Roa d
Co ll ege Stat ion , Texa s 77845
Prepared by
CSC Eng in ee rin g & Enviro nm e nt a l Co ns ult a nts, In c .
34 0 7 Tabor Road
Co ll ege Station , Texa s 77808
May 2 1, 2001
Se ni or Eng in eer
csc Dra in age Re port for Covena nt Fam il y C hurc h
TABLE OF CONTENTS
Page
GENE RAL DESCRIPT ION 01: S ITE AND P RO POSED DEVELOP M ENT ...................................... .
P R E-DEVELO P ME 1T DRA INAGE PATTE RNS AND MA J OR DRA INAGE BAS INS .................... 2
SCOPE OF RE PORT AND ORAi "AGE DES IG 1 C RI TER IA ............................................................. 2
STO R MWATE R RUNOFF COMPUTAT IONS ..................................................................................... 2
USE OF T H E R/\ T IONAI. FO RMULA........................................................................................ 2
R UNOFF COEFF IC IENTS (C) ..................................................................................................... 3
T IME OF CONCENT RAT IO (TcJ............................................................................................. 4
RAINFALL INTENS II.Y_LJ..}.......................................................................................................... 5
AREA OF S ITE (A)....................................................................................................................... 5
STORM W ATER R UNOFF QUANTIT IES................................................................................... 6
STO RMWATER DETE 1T ION CO MPUTAT IO S .............................................................................. 6
REQU IR ED M IN IMUM DETE TION STO RAGE VOLUME................................................... 6
DETE 1T ION STO RAGE AREA.................................................................................................. 7
STO R MWATE R RO UT ING CO MPUTAT IONS................................................................................... 7
METHODOLOGY......................................................................................................................... 7
ROUT ING COMPUTATIONS AND CONCLUS IONS................................................................ 8
CERTIF ICAT ION .................................................................................................................................... 9
R EFE R E, CES ........................................................................................................ ." ................................ 10
LIST OF TABLES
Ta bl e I. S um marv of R unoff Coefficient ("C") Values for Pre-a nd Post-Deve lopment
Co ndition s............................................................................................................................. 4
Table 2. Co m puted Rai n fa ll lnten s itv Val ues for Refe re nced Sto rm Return Per iod.......................... 5
Table 3. Ca lculation of Pre -and Post-Deve lopment Sto rn nvater Run off Rates Using the
F ig ure I .
F ig ure 2.
F ig ur e 3 .
F ig ure 4 .
Figure 5 .
Fi g ure 6.
F ig ure 7.
Rat ional Form u la .................................................................................................................. 6
LIST OF FIGURES
S it e Locati o n ma p Fo r Pro posed Covena nt Famil y C hurc h Deve lo pm e nt
Ca rt e r C reek Dra in age Bas in
S it e M ap Fo r Pro pose d Cove nant Family C hurc h Deve lo pm e nt
Pre-a nd Post-Deve lo pm e nt Hy drog raph s fo r 25-Y ear St o rm Eve nt
C umul ative O utfl ow (Di sc harge) Ve rs us De pth of Stora ge
Infl ow a nd O ut fl ow Hydrogra ph s Illu stra t in g Ro ut ing fo r 25-Year Sto rm Eve nt
Infl ow a nd O utfl ow Hy d rogra ph s Illu st ratin g Ro utin g fo r I 00-Year Sto rm Event
II
csc Drainage Report for Covenant Family C hurch
GENERAL DESCRIPTION OF SITE AND PROPOSED DEVELOPMENT
The s ite , wh ich is the s ubj ect of this drain age report, is located a t 40 I 0 Harvey Ro ad in Co ll ege
Station (Brazos County). Texas. The s ubj ect property, d e picted in Figure I , is s ituated on a 5 .04-acre tract
o f contiguous prope 1ty located o n the no 1th east co rn er of th e State Highway 30 (Harvey Road) and Marcy
La ne intersection . The s it e is pa rtiall y d eve lo pe d a t the present time . Existing s urface vegetati ve cover at
the s it e co ns ists of isolated nat ive trees and grasses . The s urfa ce topograp hy across th e und eve lo pe d
po rti o ns of the si te ge nera ll y s lopes to the east toward Marcy La ne. Adjacent properti es can be described
as full y to partially developed .
As previously me ntion ed . th e s it e ca n be co ns id e red as partiall y developed, and co ns ists of the
fo llowin g covered areas :
• Structures -church/office a rea (8 ,000 ft 2) a nd t wo s upport buildin gs ( 1,990 and 1,344 ft2,
respectively)
• Pavement and s idewalks -cumulative support pa veme nt and s ide wa lk s ( 11 ,334 ft2)
This report has been developed to address detenti o n requi re m e nt s for "full y " developed
conditions at the subject prop erty. Initi a ll y , the owner proposes .to construct a pprox imatel y 25,5 00 ft2 of
a dditi o nal parkin g area a lo ng t he western portion of th e s it e adjacent to S tate Hi g hway 30 . Future
development plan s w ill a lso e nt ai l the co ns tru ct ion of a s in g le-story building near the cente r of th e
prop erty a nd associated parking on the easte rn po 1t ion of the s ubj ec t property. The p ro po sed new church
buildin g foo tprint w ill e nco mp ass a n area of approximately 3 0 ,000 ft 2 and th e s upport paving w ill
e nc o mpass an area of approximately 18 ,000 ft 2.
As previously me nti o ned . the west pa rkin g area w ill be the only improvement mad e during th e
initial ph ase of th e development . Howeve r, the owner has ex pressed int e rest in th e d es ig n of a n a ppli cab le
detention facility fo r '·full y develo pe d " conditions . T h e following additional structures and res pecti ve
covered areas are planned for the proposed deve lo pm e nt (full y developed):
• S tru ct ures -new church buildin g (30 ,000 ft 2)
• Pavem ent and s idewa lks -west parkin g a rea (25,500 ft 2) and east parkin g area ( 18 ,000 ft2)
The total in crease in impervious cover assoc iated with the proposed improvements rs
approximately 72 ,500 ft 2 ( 1.66 ac res). It s hould be no te d that the g ra ss cover and associated s lopes for
g reen s pace a nd land sca pe d areas pro posed to be developed on the s ite are s imilar in c haracter a nd grad e
to the existin g "pre -deve lopm e nt .. co nditi o n s . As a resu lt , these landscaped a reas were not considered as
adding to the quanti ty o r rate of sto rm wate r run off assoc iate d wi th post-de ve lo pment conditi o ns.
csc Drainage Report for Covenant Famil y C hurch
PRE-DEVELOPMENT DRAINAGE PATTERNS AND MAJOR DRAINAGE
BASINS
The 5.04-acre s it e is located in the Ca 11er C reek Drainage basin as illu strated on Figure 2.
Topographically, the s urface elevatio n decreases by approximately 13 ft , from E l 3 14 ms ! near the
northeast corner to E l 30 I m s l o n the southwest corner of the properfy. These topographic condition s
occur over a distance of approximate ly 500 ft , resulting in an average slope of 2.6%. A re lati vely small
depression is present o n th e so uthern corner of the property, immediately upstream of a 36-inch CMP
cu lve 11 that provides s to rn1\\ater drainage beneath Marcy Lane . Ca pacity is s ues relative to this drainage
structure have been addressed in the referenced drainage report dated M ay 3, 1999 , as prepared by Klin g
Eng ineerin g & Survey in g.
There is a man -mad e draina ge cha nn e l that is located along the southwest boundary of the project
s ite . Stormwater runoff fr o m th e s it e is a combination of s heet flow and subsurface flow from a 24-inch
storm sewer that was in stall e d during previou s con struction activities at the s ite. The I 00-year floodplain
is not present within the s ite boundari es .
SCOPE OF REPORT AND DRAINAGE DESIGN CRITERIA
This report addresses the need for d e tenti o n of draina ge from the subject s ite following th e
construction of the "pha se d·· future improvements to the Covena nt Famil y C hurch s ite . Th e report ha s
been developed to e n s ur e drain age conditio ns as previou s ly documented in "Drainage Report for
Covenant Fami ly Church . Lots 22 & 23, Block I Harvey Hill s id e Subdi vision ( 1.03 acres), May 3, 1999"
prepared by Kling Engineer in g & Surveyi ng. The s ite and proposed deve lopment were evaluated in
accordance with the crite ri a o utlin e d in the Drainage Policy and Design Standards Manual (DPDSM) of
the City of College Station. Texas. The DP DSM is part of th e Storm water Management Plan for the City
of Co ll ege Station .
This report also discusses s pecific drainage control structure s related to the detention of
stormwater runoff from th e pro p osed development.
STORM WATER RUNOFF COMPUTATIONS
USE OF THE RA TI ON AL FORMULA
The Rational Fo rmul a was use d to compute the total volume of storm water runoff generated from
the full y developed s ite a nd to assess the quantity of sto rm water w hich was required to be detained to
2
csc Draina ge Re port fo r Covenant Family Church
"offset" the in c reased runoff associated with th e n ew d eve lopment. Use of the Rational Formula is
rea so nable for thi s proj ect since the contributory area of runoff is less than 50 acres, an area sometimes
referenced in the literature as an upper limit for use of the Rational Formu la. Therefore, the Rational
Formula was used to determine the peak discharge for both pre-and post-development conditions.
The general eq uati o n for the Rational Formula is well known:
Q =C I A
where:
Q =di sc harge of sto rmwater in unit s of cubic feet per second (cfs)
C = coefficient that represents the average runoff characteristics of the land cover within the
draina ge area of interest, i.e., the runoff coefficient, which is dimensionless
I = rainfall intensity in unit s of inches per hour (in/hr), and
A = a rea of the s ite that contributes to the stonnwater runoff in units of acres
The values for each of these components used to com pute .the sto rmwater runoff at the subject site are
discussed in the following sections.
RUNOFF COEFFICIENTS (C)
The run off coefficient s or .. C " va lu es were computed for both pre-development (current
co nditi o n s) and po s t-development conditions for the entire 5.04-acre s it e . Pre-development condition s
were assumed to represent the '·current" conditions as s ummarized in th e "General Desc ription of Site and
Proposed Devel opm e nt" of thi s report . The post development conditions were established to repre sent
"full y developed '. conditions subsequent to the addition of the single-story building, paved parkin g and
drive areas, and landscaped areas. The values of the runoff coefficients used for the pre-and po st-
development conditions were the values presented in Table 111-1 of the DPDSM for different types of
s urface covers and land uses.
The pre-and post-development "C" values were determined from the referenced table for the
specific ty pes of site cover and were applied to the spec ific areas of the s ite overlaid by the specifically
named cover mater ia ls . Specific types of cover and the corresponding "C' va lues used in the analysis are
listed in Table I . Also presented in Table I are calcu lated "average" "C" va lues for the pre-and post-
developed s ite .
3
csc Dra in age Re port fo r Cove nant Fa mily Chu rc h
Ta bl e I . Summ ary of Run off Coeffic ie nt ("C'.) Va lu es fo r Pre -a nd Post-Deve lo pm ent Co nditi o ns
T y pe of Ground Cover
Pre-D e velopm ent (C urrent Co ndit ion:;)
Ex istin g Buildin gs and Stru ctures
Pa rkin g and Dri ves
Und eve lo ped Gra ss and La nd scape d
A reas
S ummation
Area of
Coverage,
(square feet)
11 ,334
66 ,791
14 1,4 17
219,542
T y pical "C "
Values
0.90
0.90
0.4 0
Extended Multiplication of
"C" Values x Area
10 .2 00
60 ,112
56.566
126 ,878
Ave ra ge Pre-Deve lo pm e nt "C" va lu e = 126 ,87 8 squ are fee t I 2 19,542 squ a re fee t = 0 .5 7
Pos t-De velopment (Fu lly De ve loped)
Ex istin g Buildin gs and St ru ctures
(I 1,334 ft2) an d ew Church
Buil d in g (30 ,000 ft 2)
Ex istin g Pa rkin g and Dri ve Area s
(66 ,792 ft 2) and ew Wes t (25,5 00
ft 2) a nd East Pa rkin g ( 18 ,00 0 ft 2)
Area s
Re ma in ing Und eve lo pe d Grass a nd
La nd sca ped Ar ea s
S ummation
4 1,334 0.90 37 ,200
11 0,292 0.9 0 99 ,262
67 ,916 0.4 0 2 7,167
219,542 163 ,628
Ave ra ge Pos t-Deve lopme nt "C" va lu e = 16 3,62 8 sq uare fee t I 2 19,542 squ are fee t = 0 . 74
T he res ultin g wei g hted "C'' va lu e of 0 . 74 wa s used to re prese nt pos t-deve lo pm e nt drainage across th e s it e
a nd in s ubse qu ent run off co mpu ta ti o ns pr ese nt ed he re in .
TIME OF CONCE NTRATIO N (tc)
T he tim e of co nce ntrat io n at a s ite is used to dete rmin e the intensity of th e rai nfa ll even t use d fo r
co mpu ti ng storm water fl ow s a nd required dete nti o n vo lum es . The t im e of co nce nt ra ti o n is defin ed as "'th e
tim e requ ired for th e ru noff to be es ta bli shed and fl o w fr o m the mo st remote pa rt o f th e dr a ina ge a rea to
the po int und er des ign:·
T he tim e of conce ntra tio n fo r th e s ubj ec t s ite wa s ca lc ul ated base d up o n th e e leva ti on differe nce
a nd t he flow di sta nce fro m the no rt heast co rn e r of the s it e , to the ex istin g 24-in ch sto rm wa ter inl et loca ted
in the nort h pa rkin g a rea , to a po int of di sc harge in t he ex ist ing d epr essed area at th e so uth east co rn er of
th e s ubject prop erty as illu strated in Fig ure 3 . T he s lo pe or g rad e of the s it e fo r pre -deve lo pm e nt
4
csc Drai nage Re po rt fo r Covena nt Fa mil y C hurc h
condi t io ns was d e termin e d fr o m th e re fe re nced Klin g Eng in ee ri ng & S urvey in g re po rt d a te d May 3 , 19 99.
T he s lo pe fo r po st -d eve lo pm e nt conditi o ns w a s d e te rmin e d fr o m the pro posed s it e g radin g pl a n, which
will be c o n s iste nt wi th th e ex istin g s it e to pog raphy with th e e xc e pti o n of lo cali zed g radin g near th e
proposed s tru c tures . Us in g th e s ur face tra ve l di s ta nce o f a p prox imate ly 8 7 0 ft a nd a we ig hted fl ow
ve loc ity compute d fro m th e var io us m e th o d s of co nveya nce a lo ng th e fl ow pa th (Fi g ure 3), a tim e of
concent rat io n o f ap p rox im a te ly 2 .7 minutes was d e termin ed fo r pre-d eve lo pme nt fl ow. T he post-
d eve lo pm e nt tim e of concentrati o n was compute d in a s imil a r ma nner to usi n g a fl ow di sta nce o f 8 35 ft .
T he tim e of co nce n tra ti o n fo r post-d eve lo pm e nt c ondition s was a lso compute d to be 2.7 minutes us in g a
w e ig hte d fl o w ve loc it y o f 6 .8 ft/sec (Fi g ure 3 ). Ba sed o n DPDSM c rite ri a, a minimum tim e o f
conce nt ra ti o n o f 10 minutes is re quired for th e d es ig n of d ra ina ge system c o mpo ne nt s, in c ludin g
dete nti o n fac iliti es . Accordin g ly , a tim e of c o nce nt ration of I 0 minutes was used in th e s ub sequ e nt
drain age ca lc ul a ti o n fo r th e s it e.
RAINFALL INTENSITY (I)
T he rain fa ll in te ns ity va lu es we re compute d for th e 10-minute tim e o f concentra ti o n prev io us ly
di scussed us in g th e inte ns it y-durati o n-fre que ncy c urv es d eve lo ped by th e T exas Depa rtm e nt o f
Tran s po rt at io n . Th e co mputed int e ns iti es ca lc ulate d fo r sto rm eve nt s w it h "re turn pe riod s" of 5, 10 , 25 ,
5 0 , a nd 100 years a re indicate d in Ta bl e 2.
Ta bl e 2 . Comp uted Ra in fa ll lnt e nsity V a lu es fo r Refere nced Storm Return Pe ri o d
Storm Return Period
(years)
AREA OF SITE (A)
5
10
25
50
10 0
Rainfall Intensity
(inches/hour)
7.7
8.6
9 .9
I I. I
12 .3
As previ o us ly di sc ussed . th e s it e proposed for d eve lo pm e nt e nco mpa sses approx im a tel y 5.04
acres . Accordin g ly , co mputa ti o ns assoc ia te d w ith th e eva lua t io n o f sto rm wate r run o ff we re d e ve lo pe d
us in g a n a rea o f 5.04 ac res .
5
csc Drainage Report for Covenant Fa mil y C hurc h
STORM WAT E R RUNOFF QUANTITIES
Sto nn water runoff rat es we re ca lc ul a te d us ing th e Rati o nal Formula . Run off rates were ca lc ulated
for both pre-and post-development co ndition s for the 5.0 4-acre s it e a nd are present e d in Table 3.
Table 3 . Ca lc ulati o n of Pre-and Post-Deve lopme nt Stormwater Run off Rates Us in g the Ration a l
Formula
Storm Site A r ea 11 ,. Site Area 11051 Intensity pre Inten s it y 11051 Q
1
pre Qpos t Q
1
difT
Event (acres) (acres) Cprc Cpos t (in/hr) (in/hr) (cfs) (cfs) (cfs)
5 5.04 5.04 .57 .74 7 .7 7 .7 22 .1 28 .7 6.6
IO 5 .04 5.04 .57 .74 8 .6 8 .6 24.8 32.2 7.4
25 5 .04 5.04 .57 .74 9.9 9 .9 28.3 36 .8 8 .4
50 5.04 5 .04 .5 7 .74 I I. I I I. I 32.0 41.6 9 .6
100 5 .04 5 .04 .57 .74 12.3 12.3 25.3 45 .9 10 .5
No tes:
I. Permitted rate or o uttl ow from detention basi n.
2. Difference in ll ow s th at wil l require deten tion .
The calculate d pre-development flows prese nt e d in Tab le 3 for the 25-year storm eve nt rep resent
th e maxi mum permiss ibl e di sc ha rge flo w rates from the d etent io n facility. The diffe re nce in the pre-a nd
post-deve lo pm ent fl ows for the 25-year sto rm eve nt li sted in Tabl e 3 (Oct itT = 8 .4 cfs) represents the
in c rease in fl ow rate fr o m th e development that mu st be detaine d .
STORMWATER DETENTION COMPUTATIONS
REQUIRED MINIMUM DETENTION STORAGE VOLUME
The required s torage vo lum e of the d etenti o n ba si n was ca lcul ated s u c h th at the peak discharge of
th e ul timate de ve lo pm e nt hy dro gra ph s fo r th e 25-year d es ig n sto rm was limited to a discharge le ss than a
defined target disc h arge . The target di sc h a rge was de fin e d by t he DP DSM to be the peak di sc harge of the
pre-deve lop m e nt hy drograph for the 25-year storm event. A s previous ly me nti o ned, d etenti o n
requirements have bee n computed for ·'full y deve lo ped '' cond itio ns even th o u g h the site d evelopm e nt will
occur in a phased approac h .
T he req uired detention storage volume was determined as th e difference in a rea betwee n the pre-
and po st-developm e nt hy drographs, w hi c h are d ep icted on Figure 4 . The Triangular Approximation
M et hod was u sed to d ete rmin e th e hy drog raph s . The hydrograp hs were constructed by assuming that the
peak discharge, as calculated from the Rati onal Formul a , occ urs at a time e qual to the time of
conce ntrati o n and that o ne -third of the flow vo lum e occ urs before th e peak discharge is reached and two-
6
csc Dr a ina ge Rep o rt fo r Cove na nt Family C hurc h
third s occ ur following th e peak discharge. T he Tr ia ng ular Approximation Met hod of developing
hydro g raph s is generally co ns id ered to be acceptable fo r analysis of se co nd ary drain age syste ms wi th an
a rea of less th an 50 ac res. whi ch is a ppli ca bl e to th e drainage bas in addre ssed in thi s report.
By co mp a rin g th e two hydrogra ph s in Figure 4 , it is apparent that the difference 111 areas
att ributabl e to in creased fl ow s from the pro posed development is relatively sma ll . As previously
discussed , bot h the pre-a nd post-development flows we re deve loped for the e ntire 5 .0 4 acres of
co ntributo ry drain age area . T he difference in area betwee n the two hydro grap hs, o r th e required minimum
vo lum e of the detent io n storage area for th e 25-year sto rm eve nt , wa s calc ulated to be a pp rox imat e ly
7,600 ft 3
. A 10 % increase in the required volume as s pec ifi ed in th e DPDSM res ult ed in a des ig n
dete nti on vo lum e of 8,360 ft'.
DETENTION STORAGE AREA
Give n th e relatively low storage vo lum e require d fo r detention and ex ist in g site co ndition s, the
ow ne r has e lect ed to take advantage of the nat ural topographic features a nd co nst ru ct a detent io n area
w ithin the ex istin g drainage area at the s it e. The locat io n of the propo se d stor mwat er dete nti o n basin is
illu strat ed in Figure 2 . The average plan a rea o f the nat ur a l detenti o n ba s in is a ppro x im ate ly 2,095 ft2• The
ave rage depth of the drainage basin is a ppro x im ate ly 4 ft (E l 295.0 to El 299.0 ms l). T hu s, the volume
ava il ab le fo r detention is approx im ate ly 8,380 ft 3 . An o utl et struct ure will be constructed o n the north e nd
of th e drainage basin to co ntr ol di charge from the dete nti o n facility.
STORM WATER ROUTING COMPUTATIONS
METHODOLOGY
The detention basin wa s ana lyzed for fl ow rout in g through the areas under different storm eve nt s .
T he purp ose of the routi ng a nalysi s was to s imul ate the perfo rm anc e of the detention bas in in the form of
inflow and ou tfl ow hydrographs .
T he storage-ro utin g analy s is was pe rform ed base d up o n the Pul s Method . The Pul s Method is a
pro ced ure fo r grap hi ca ll y so lv in g the co ntinuity equ ation for sto rage re servoi rs us in g the c har.ac teri sti c
hei ght-storage a nd he ig ht -d isc harge c ur ves. As prev ious ly di sc usse d , th e equ iva le nt of the he ight-storage
c urv e was developed gra phi ca ll y fro m the gra din g plan and the invert elevation of the outlet st ructure . A
heig ht -disc ha rge or disc harge versus depth of storage c ur ve was a lso developed for the o utl et structure.
T he curve for the area of int erest is illustrated in Fig ure 5 -C umulati ve Outflow (D isc harge) ve rsus
De pth of Storage.
7
csc Drai nage Re port fo r Covena nt Fami ly C hu rc h
ROUTI NG COMP UTATIO NS A N D CONCLUSIONS
Rout in g a na lysis was pe r for m ed fo r t wo sto rm eve nts: th e 25-year event, w hi c h re presents t he
d es ig n sto rm ; and th e I 00-yea r eve nt as s pec ifi e d in th e DPD S M . Infl ow a nd o ut fl ow hy drogra ph s
illu st ra ti ng ro utin g for 25-yea r a nd I 00-year sto rm event s a re p rese nt ed gra phi ca ll y o n F ig ures 6 and 7,
res pecti ve ly. As can be see n fro m F ig ure 7, th e max imum o utfl ow fro m th e detenti o n bas in is
a pp roximate ly 24% of th e max imum pre -d eve lo pm e nt ra te of28.3 cfs. T herefo re, th e detent io n bas in has
th e ca pacity to s to re the excess vo lum e of sto rm wate r assoc iated w it h th e p la nn e d d eve lo pm e nt o f th e s ite
a nd . di s c ha rge th e stored wate r a t a ra te th a t is "equal to or less th a n t he pea k di sc ha rges of th e pre -
d eve lop men t hy d rographs fo r t he design [25-year] storm '· as spec ifi e d in t he DPDSM . In addit io n, t he
res ult s of t he ro ut ing a na lys is for t he I 00-year eve nt as illu st ra ted in F igure 7 indi cate t hat t he hi g he r
fl ows associa ted with thi s eve nt w ill flow ove r th e to p of t he co nc re te wa ll o utl e t structure onto a r ip-
ra pp ed area prio r to disc harge t h ro ug h t he roa d way c ul ve rt a nd w ill no t adverse ly im pact th e integr ity of
th e bas in .
8
csc Drainage Report for Cove nant Fam il y C hurch
CERTIFICATION
"I here by ce rtify that this repo1t fo r drainage design of the sto rmwater detention basin at the 5 .04-acre
Cove na nt Family C hurc h locate d a t 40 I 0 Ha rvey Road in Co lle ge S tat io n (Bra zos Co un ty), Texas, was
prepared und e r my s up e rvi sion in accordance with the prov isio ns of the City of Co lle ge Station DP DSM
for the owners thereof . .,
/f'ii £ e.,_v.._
5/J1/c1
!/JJ. ~ . Ut___
W .R . C ull en , P .E.
Registered Professional Eng in eer
State of Texas P.E. Number 652 15
9
csc Drainage Repo11 for Cove nant Family Church
REFERENCES
Chow , Ven T., Maidment, David R. and May s, Larry W. 1988. Applied Hydrology . McGraw-Hill Book
Company. New York , NY .
City of Co ll ege Station, Texas . October 1992 . Drainage Design Guideline Manual.
Davis , Victor D., and Soren e n, Kenneth E. 1969 . Handbook of Applied Hydraulic s. McGraw-Hill Book
Co mpany . New York. NY.
Mason, John M. and Rhombrerg. Edward L. 1980. On-Site Detention . Prepared for Texas Engineering
Extension Service. Texas A&M University . Co ll ege Stat ion, TX. Publication No . PWP : 03355-0 I.
McCuen, Richard H. 1982 . A _Guide to Hydrologic Analysis Using SCS Method s. Prentice-Hall , Inc .
Englewood C li ffs , NJ.
United States Department of Agriculture . January 1975 . Urban Hydrology for Small Watershed s.
Technical Release No. 55 . Engi neering Division , Soi ls Co nservation Service , U.S. Department of
Agriculture.
Wanielista , Martin P. 1978 . Sto rmwater Management Quantity and Quality. Ann Arbor Science. Ann
Arbor, Ml.
Westaway , C.R. and Loomi s, A. W. 1979. Cameron Hydra ulic Data . (I 6111 Edition). In gerso ll-Rand .
Woodcliff Lake , J.
10
FIGURES
SUBJECT
TRACT
Prepared For:
COVENANT
FAMILY
CHURCH
NOT TO SCALE
SITE LOCATION MAP FOR PROPOSED
COVENANT FAMILY CHURCH
COLLEGE STATION, TEXAS
PROJECT : COVE NANT FAMILY CHURCH
LOCATION : COLLEGE STATION TEXAS
APPR: DATE :
DRAWN BY : JBF SCALE : NOT TO SCALE
DATE : 05/21/01 FIGURE : 1
\\Shared\shared c\G ra phicslcovenantldwg\FIG 1.dwg, 05/2 112001 06:31:27 AM
C :\WINDOWS\TEMP\A$C4FCB56B7.DIB
Prepared For:
COVENANT
FAMILY
CHURCH
•
SITE
LOCATION
Carter Creek Drainage Basin
PROJECT: COVENANT FAMILY CHURCH
LOCATION : COLLEGE STATION TEXAS
APPR: DATE:
DRAWN BY: JBF SCALE: NOT TO SCALE
DATE : 05/21/01 FIGURE : 2
1\Sharedlshared c\Graphics\covenanl\dwg\FIG2.dwg, 05/21/2001 00:24:51 /Wi
50
40 -Q post =36.8cfs J!?
(.) -0
~ 30 w
(!) a::
<( :c 20 (.)
Cl) -0
10
0
5
VOLUME OF DETENTION STORAGE
(EQUALS DIFFERENCE IN AREA
BENEATH EACH HYDROGRAPH)
/POST-DEVELOPMENT ~1 HYDROGRAPH en
(lJ ...... ......
::J ::J
c c
E E
0 0
I"") I"")
E E ~EVELOPMENT II II
1il 0 0 0 ~ a. a.
I I
..J' 0
II II ......
I"") I"")
ll 1il .... 0 HYDROGRAPH a. a.
I I
~ ~
10 15 20 25 30 35
TIME, (minutes)
Prepared For:
COVENANT
FAMILY
CHURCH
Pre-and Post-Development
Hydrographs for 25-Year Storm Event
PROJECT: COVENANT FAMILY CHURCH
LOCATION : COLLEGE STATION TEXAS
APPR : DATE :
DRAVVN BY: JBF SCALE : NOT TO SCALE
DATE : 05121/01 FIGURE : 4
l\Sharedlshared c\Graph ic s\covenant\dwg\FIG4 .dwg , 05121/2001 06:28:45 AM
20
18
16
14
~ 12 a w
Cl a: 10 < ::c
0
!!1 c 8
6
4
2
0
0
IMlmffN: Of llElDl1DI PlllO
1 2 3 4 5
OEPTll OF WATER IN DETENTION PONO, (ft)
I•\
Prepared For:
COVENANT
FAMILY
CHURCH
Flow through 18-inch Outlet Pipe
vs. Depth of Water in Detention Pond
PROJECT COVENANT FAM ILY CHURCH
LOCATION: COLLEGE STATION TEXAS
APPR: DATE :
DRAWN BY : JBF SCALE : NOT TO SCALE
DATE : 05/'21/01 FIGURE : 5
l \Shar ed\shared c\Graphics\covenant\dwg\FIGS.dwg, 0512112001 06:35:06 AM
40
35
30
~
~ 25
0 INFLOW w
~ 20
c:(
::c
(.) 15 CJ)
0
10
5
0
0 10 20 30 40
TIME , (minutes)
1
1 C
8
c I Inflow and Outflow hydrographs
_ . Illustrating Routing of 25-Year Storm Event
:=======:P;=re=pa=red::::;:For::=. ====: PROJECT : COVENANT FAM ILY CHURCH
COVENANT LOCATIO N: CO LL EG E STATION TEXAS
FAMILY A PPR: DATE :
CHURC H DR AWN BY: JBF SC A LE: NOT TO SCALE
DATE : 05/21/01 FIGURE : 6
l \Shared\sha red c\Graph icslcovenant\dwg\FIG6.dwg , 05/2 1/2001 09:27 :42 AM
60
50
~ 40 -0
w
(!)
~ 30
:::c
(.)
(/') c
20
10
0 10
DETENTION POND AT CAPACITY
/ EMERGENCY SPILLOVER OCCURS
/ INFLOW=OUTFLOW
20 30 40
TIME, (minutes)
50
1
1 C
8
c I Inflow and Outflow hydrographs
. Illustrating Routing of 100-Year Storm Event
~=====================~ Prepared For. PROJECT: COVENANT FAMILY CHURCH
COVENANT LOCATION : COLLEGE STATION TEXAS
FAMILY APPR : DATE :
CHURCH DRAWN BY : JBF SCALE : NOT TO SCALE
DATE : 05/21/01 FIGURE : 7
\\Sharedlsha red c\Graphics\coven antldwg\FIG7.dwg , 05121/2001 09:24 :44 AM
l .
-
.. '
' )
c
s
c I
Engineering & Environmental
Consultants . Inc .
June 8, 200 I
Mr. Spencer Thompson
City of College Station Development Services
I I 0 I Texas Avenue
Co ll ege Station , TX 77 840
RE!VIEWED FOR
~ COMPLIA~
JUN 2 1 2001 \)
COLLEGE STATION
ENGINEERING
Re: Response to City of Co ll ege Station Engineering Review Comments o . I Regarding The Drainage
Report for Covenant Family C hurc h (Ha rvey Hillside Subdivis ion)
College Station (Brazos County), Texas
Dear Mr. Thomp son:
CSC Engineering & Environmenta l Co nsultants , In c. (CSC), on behalf of the Covenant Family Church
has prepared a re s ponse to the City of College Station 's review com ments dated May 29, 200 I. The City
of Col lege Station's comment s are presented in itali cs, immedi ate ly followed by a response that addresses
the comment.
• I n eed to re view a co mplete routing of stormwater throug h the proposed pond and through the 36 "
CMP. Ther e is an area to the west that drains through here. Please include a drainage area map.
The drainage map for the subbasin does indicate that off-site runoff will be directed to the 36" CMP
located along Marc y Lane. It is our understanding that details regarding drainage from off-site areas have
bee n previ o us ly addressed in an engineering report prepared by Kling Engineering & Surveying (Kling)
entitled ·'Dra ina ge Repo rt for Covenant Family Ch urch , Lots 22 & 23, Block I Harvey Hillside
Subdi vis io n ( 1.0 3 acres), May 3 , 1999." The detention facility for this project has been designed in a
manner th at will not restrict the current surface flow to the 36" CMP. A copy of the area drainage map is
presented in Attachment A of this letter.
• Please show what call-outs in hex boxes refer to , Sheet C -1. Many of the numb ers did not s how up in
th e printing process. Som e of th e information may have been misread.
A complete "plot copy" of th e project plans ha s been enclosed as part of this submittal.
• Will th e parking lot storage depth of 8 " be exceeded when th e new lot s drain into the existing grates?
Please show calculations.
Inform ation pre sented in Kling 's referenced report ind ic ates that the flow from area 48 (which includes
the two existing parking areas) is 5 .62 cfs for the I 0-year storm event and I 0.35 cfs for the I 00-year
storm event. These flows will in crease s li g htly due to the construction of proposed parking bays I and 2
a nd will be conveyed throu g h two inlet grates to the existi ng 24" storm drain. Specifically, the
construction of proposed parking ba y No. I wi ll increase the flow to grate 1 to 7 .04 cfs for the 10 -year
storm event and to 12 .26 c fs for the 100-year sto rm event. It s hould be noted that due to the topography of
the drive a rea between the two grates, once the depth of ponded stormwater at the grate I lo cation
exceed 0.4 ft (or 4 .8 inches), ponded stormwater will begin to flow to grate 2. At 0.4 ft d epth of ponded
water, approx im ately I 0.05 cfs w ill flow into grate 1. Thus, g rate 1 can handle all of the 7 .0 4 cfs flow
from the I 0-year event and all but 2.2 1 cfs ( 12.26 cfs -I 0.05 cfs) from the I 00-year event.
3407 Tabor Road
Bryan, Texas 77808
Phone (979) 778-2810
Fax (979) 778-0820
I c
s
c I
Mr. Spencer Thompso n
Page 2
Jun e 7, 200 I
T he construction of proposed parkin g bay No. 2 has been desi g ned in a manner that w ill a ll ow sto rmwater
run off to be con veyed p rim aril y by grate 2 . F low from p roposed parkin g bay 2 to grate 2 is calcu lated to
be 1.42 cfs for the I 0-year st o rm eve nt and 1.9 cfs for the I 00-year storm event. The re s ul ti ng d epth of
po nd ed storm water at the grate 2 locat ion , in c ludin g t he overflow from the g rate I locat io n for the I 00-
year event, is estimated to be less th a n 0.3 ft for both event s.
T he a ll owabl e storage depth prese nt ed in C ity of Co ll ege Statio n Drain age Policy an d Design Stand a rd s
Manual is 0.83 ft for the I 0-year sto rm eve nt and 1.5 ft for th e I 00-year sto rm event. As indicated by the
refere nc ed calc ul ations , both of th ese design limitation s wi ll not be exceeded for the propo sed parkin g
a rea layout. Stormwater flow in the "future parking Bay 3 " w ill be conveyed via s heet flow to a
sto rm water ditch a lo ng Hi g hway 30 as indicated in the referenced Klin g report a nd therefore w ill not have
to routed to the reference d grated stotmwate r inl ets .
• Please expla in disc harge calculations for th e 36 " CMP. What is the flo w lin e elevation and slope ?
A s previ o u s ly stated , drain age iss ues relative to the 36" CMP have been addressed in the referenced
e ng in eeri ng Klin g report. ln fomiat ion prov id ed by Kling indi cates th at the up stream fl ow lin e is at E l.
294.26 ms l a nd the downstream flo w line is at E l. 292.50 msl. The 36" CM P that conveys stormwater
be neath Marcy Lane is approximate ly 26 ft long. The res ultin g s lope of th e 36" C MP is 6.7%.
• Pl ea e include Modified Puls routing .spreads hee t.
T he stormwater rout in g work s heets fo r the 25 -a nd I 00-year storm event s have been included in
Attachm e nt A . The work s heet fo r th e 25 -year storm eve nt indicates a max imum o utflow of 7.9 cfs or
approximate ly 25 % of the predeve lo pm e nt fl ow . In additio n, the wo rks heet for the I 00-year storm event
indi cates that th e detent io n fac ili ty wa ll w ill be overtopped a s required by t he provi s ion s of t he City of
Co ll ege Statio n Drainage Po li cy and Des ign Standards Manual.
Plea se conta ct either of th e unders ig ned indi v idual s at 778-28 10 if yo u have any questi o n s or need
ad diti o nal inform atio n concerning thi s matter.
~'~
Respectful ly, .. 'l.~·~1 1
R ;z_ I t .. ,,,.'"'~ 6li • ".:I l•i >' ,. '; • r ~~ ,,,; ~ .... ·-·····-.... ~ . -A. CUUEN.A ~ ·r...... .,~....-. .. ····~
W.R . C ullen , P .E. 1\ 65215 ~ /~J
Se ni o r Eng ineer ,,.~··t~e! · ·~~!.~:& ,,~~~·· ··t.~~ w___
1n,~~~~'"--... ~,..,. to/?/~1
M. Frederic k Con lin , P .E.
Seni o r Eng in eer
WRC:mf
Enc losure
Via Hand Delivery
ATTACHMENT A
Area Drainage Map
Storage Depth Calculations
Stormwater Routing Worksheets
• c
s
c
v
I
Engineering & En111ronmental
Consultants, Inc.·
~
N ~ /II J \I rzi ~
--I..._ ,_ r l. <
v ~
' '.=: /h 'Z z: r
..... I-' I I j
-
r II' --r J(. ! .I < (
I
"'
.
u
'
Project: C OV ~ N 'A "'l F Id''\ 1 L 'f ~Date : --=-G+-}--=-fo+-/_l'.l -'--1 _
Created By: _W_lZ_c ____ _ Page_)_ of_/_
--I-I--
--~ I I"" K -1 l'I t~ n
I-
--
r ,_ I I\ I .
I.-: ( ,, 1 ..., I I r; \
I'-
7 ' -~
, A -, __ ,_
1--
\ -( ~ c ·~ -J .,
l -.... 4 -1 ( I / -2 h I\ ·-'---11 t 0 J
.I If ' ~ -
I/ ' , \
.) " :r 1 I , I 2'. ....
'\
•'-)
I<. -A ~ ' D. . ' h
r'\ -'1 , ' ' ' ( -·~ (. )."~ ~ I I\. "-
I -I -.... ) ... 1'
'-" -I I J .I (, I UI ,-I~ -,_
I n~ ""t"IK
' ~ , .. 11 <,<,I \
\ I" I
~ . c 1'-1. < • I~ <. \ 11
I
--ID IJ I .. ~
I\. -
:: I Cl I i,,' l 7J I
·~
-I ~ ,
...-, IA '} ,..... I• r ~ y ,
\.
I c.. ::. L r 7 ll ' .
~
'J (~ () .,..
-
• t ~. ~ ... I}~ l,, ~: Routing Calculations for 25 year storm Time Inflow lavgDt (min) (cfs) (ac-ft) 0 0.00 0.00 2 7.36 0.01 4 14.71 0.02 6 22.07 0.03 8 29.42 0.04 10 36.78 0.05 12 33.10 0.03 14 29.42 0.03 16 25.75 0.04 18 22.07 0.03 20 18.39 0.03 22 14.71 0.02 24 11.03 0.02 26 7.36 0.01 28 3.68 0.01 30 0.00 0.00 y1 S-ODt/2 S+ODt/2 y2 Outflow (ft) (ac-ft) (ac-ft) (ft) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.10 0.80 0.10 0.00 0.03 0.30 2.70 0.30 0.00 0.05 0.50 4.50 0.50 0.00 0.07 0.70 7.10 0.70 0.00 0.09 0.90 7.90 0.90 0.00 0.07 0.70 6.40 0.70 0.00 0.06 0.60 5.50 0.60 0.00 0.08 0.80 7.10 0.80 0.00 0.07 0.70 6.40 0.70 0.00 0.06 0.60 5.50 0.60 0.00 0.05 0.50 4.50 0.50 0.00 0.04 0.40 3.70 0.40 0.00 0.03 0.30 2.70 0.30 0.00 0.02 0.20 1.75 0.20 0.00 0.01 0.10 0.80
Time Inflow lavgot y1 5-0Dt/2 S+ODt/2 y2 Outflow (min) (cfs) (ac-ft) (ft) (ac-ft) (ac-ft) (ft) (cfs) 0 0.00 0.00 0.00 0.00 0.00 2 9.17 0.03 0.00 0.00 0.03 0.35 3.20 4 18.35 0.06 0.35 0.01 0.10 1.20 9.70 6 27.52 0.09 1.20 0.04 0.19 2.30 13.10 8 36.70 0.13 2.30 0.10 0.32 3.62 16.40 10 45.87 0.16 3.62 0.21 0.49 5.00 overtops wall 12 41.29 0.14 0.30 14 36.70 0.13 0.27 16 32.11 0.11 0.24 18 27.52 0.09 0.21 20 22.94 0.08 0.17 22 18.35 0.06 0.14 24 13.76 0.05 0.11 26 9.17 0.03 0.08 28 4.59 0.02 0.05 30 0.00 0.00 0.02