HomeMy WebLinkAboutDrainage Design Approach KT ING ENGINEERING &SURVEYING
Consulting Engineers • Land Surveyors
4103 Texas Avenue, Suite 212 Post Office Box 4234
Bryan, Texas 77802 Bryan, Texas 77805
Telephone 979/846-6212
Fax 979/846-8252
S.J. Kling, P.E., R.P.L.S.
S.M. Kling, R.P.L.S.
Putz-Meyer Subdivision - Site Development
Drainage Design Approach
September 20, 2004
Current Flood Plain Record Information:
1. Primary Drainage Basin: Burton Creek
2. Flooding source: Unnamed Tributary to Burton Creek
3. FEMA Map No.: 48041 C0142 C
4. FEMA Flood plain designation: Zone A - No Base Flood Elevations Determined
5. Upstream drainage area: -43 acres (0.07 sq miles) determined my Mitchell &
Morgan, LLP (M+M) January 15, 2003 as documented in letter report to the City
of College Station
6. Q100 for drainage area: 218 cfs determined by (M+M)
7. Outfall device for the drainage area is 2-36" RCP culverts installed by TXDOT
under University Drive.
8. Base Flood Elevations (BFE's) determined by (M+M) based on City of College
Station 2' digital contours (BFE @ University Drive -304.2').
Proposed Design Approach:
1. Due to existing development conditions downstream of University Drive - No
increase in runoff is allowable.
2. Development in the Burton Creek drainage basin requires mandatory detention
per City drainage policy.
3. Detention to be provided within the limits of the FEMA horizontally positioned
floodplain / limits of M+M determined floodplain.
4. Existing conditions cause un-designed detention to occur within the limits of the
existing channel. Volume of storage is estimated based on the BFE's
determined by M+M and is approximately 4.4 ac-ft on-site with an additional 2
ac-ft in the University Drive right of way. This total volume (-6.4 ac-ft) will be
incorporated into the detention facility designed for the project.
5. A preliminary volume required to attenuate excess runoff through the 100 year
event was calculated based on the currently proposed development scenario.
This volume is approximately 1.25 ac-ft for a developed area of approximately
7.3 acres. Additional detention (-0.5 ac-ft) will be provided to attenuate a small
portion of the previously named Henton-Lincoln development that drains to the
site (refer to Henton-Lincoln drainage report). Total required detention -1.75 ac-ft
6. Volume of detention pond to be approximately 8.2 ac-ft accommodating existing
channel storage & required storage due to development. Pond to consist of
underground boxes discharging directly into the TXDOT structure but not
influenced by the structure.