HomeMy WebLinkAboutDrainage Report LetterKLING ENGINEERING & SURVEYING
~onsulting Engineers • Land Surveyors
4101 Texas Avenue, Suite A
Bryan, Texas 77802
B.J. Kling, P.E., R.P.L.S.
S.M. Kling, R.P.L.S.
Date: February 9, 2007
To: Josh Norton
City of College Station
From: Jeremy Peters, E.I.T.
Fred Paine, P .E.
Telephone 979 / 846-6212
Fax 979/846-8252
Post Office Box 4234
Bryan, Texas 77805
Re: Common Area 'F' OZ / z/or
Amendment to the Drainage Report for Lot 3R, Block 2, C escent Pointe Phase 2 and
An Additional 14.9 Acres of Block 2 of Crescent Pointe
As documented in the Drainage Report for Lot 3R, Block 2, Crescent Pointe Phase 2 & An
Additional 14.9 Acres of Block 2 of Crescent Pointe, Block 1 of Crescent Pointe drains through an
existing 4'x3' box culvert, across Crescent Pointe Parkway and contributes to the detention pond in
Common Area 'F'. The area within Block 1 of Crescent Pointe is also documented in the Drainage
Report/or Lots JR-3R & Common Area 'D', Block 1, Crescent Pointe Phase Two, Vol. 7594, Pg.
JO.
The detention pond in Common Area 'F' was designed assuming existing conditions runoff from Block 1.
Now, with the design of the detention pond in Common Area 'D', the contributing runoff to Common
Area 'F' will be reduced. This amendment will show that the reduced contribution of Block 1 does not
adversely affect the attenuation provided by the detention pond in Common Area 'F'.
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pg 1 of2
The following table summarizes results of ultimate development storm water routing, and should be
regarded as amending Table 9 of the original report.
PEAK DISCHARGE RATE STORM EVENT
(CFS)
2YR 5YR 10YR 25YR 50YR 100YR
DA-3-POST 44 48 51 55 61 69
DA-4A-POST 140 170 191 218 246 257
DA-4A-POST Inflow 172 208 232 264 297 309
DA-4A-POST Outfall/ WSEL 491277.6 531278.2 55 / 278.6 58 / 279.1 60 / 279.7 61 / 279.9
DA-4A-POST Discharge 9.98 10.79 11.20 11 .81 12.22 12.42 Velocity
DA-48-POST 2 2 2 3 3 3
DA-48-POST Inflow 49 53 55 58 61 62
Project Outfall / WSEL 491270.6 53 / 270.8 551270.9 58 / 271 .0 60 / 271 .1 62 / 271 .1
Project Outfall Velocity 14.05 14.37 14.52 14.73 14.87 15.01
*reported values vary slightly from calculated values due to differences in the runo:ffhydrograph and routing
procedure calculation time steps Table 9
All calculations can be found in Appendix 1, contained on the attached CD. Additionally, the following
table amends Table 11 of the original report, and it shows there are no adverse affects from reducing the
contributing runoff from Block 1.
PEAK DISCHARGE RATE (CFS) STORM EVENT
THROUGH PROJECT OUTFALL
2YR 5YR 10YR 25YR 50YR 100YR
Pre Developed 69 83 92 103 114 118
Post Developed 49 53 55 58 60 62
The reduced contributing runoff from Block 1 of Crescent Pointe due to the design of the detention pond
in Common Area 'D' does not adversely affect the attenuation provided by the Common Area 'F'
detention pond.
pg 2 of2