FtWorth Townhouse Project Adjacent to Bentley Village
Existing Drainage & Proposed Drainage Plan
The information below has been provided by Peter Kavanagh, Zone Systems, Inc. as request by residents at the September 28th meeting.
Existing Drainage Plan
This plan shows how the site currently drains. A portion (Area A) of the site slopes/drains into Randol Mill and the balance slopes/drains onto the Bentley Village Subdivision. Area C1 drains to the northeast corner and the balance (Area C2) slopes/drains onto the two lots east of this tract.
Proposed Drainage Plan
This plan shows how the drainage will be handled after development. Area A will drain into Randol Mill including a new inlet in the alley to intercept part of the flow from Area A. Area B will be intercepted on-site by a underground storm drain system with inlets as shown. The storm drain system will outfall into the detention pond. The detention pond will be designed to restrict the developed storm water runoff (which is significantly higher than the runoff from existing/undeveloped conditions due to increase in impervious surfaces) to the capacity of the existing 18” RCP storm drain pipe at the northeast corner. As the runoff exceeds the capacity of the restricted outlet structure the runoff will “backup” into the pond as long as the rainfall rate exceeds the capacity of the existing pipe. Area C is the area that will slope/drain onto the Bentley Village development. AS you see from the two plans, Area C1 and C2 in the existing plan area greatly reduced to Area C in the proposed plan. Area C is simply the backside of the dam/embankment for detention pond.
In summary, a large portion of this site in the undeveloped state slopes/drains onto Bentley Village. A portion (Area C1) drains to the north and the other portion (Area C2) slopes/drains onto the Bentley Village on the east side. There is a pipe extended for this area, but is buried and not in use now. The total of Area C1 and C2 is 3.45 acres.
Upon development, Area A will slope/drain to Randol Mill. Area B will be intercepted by the new underground storm drain pipe system and inlets. All of Area B will outfall into the detention pond which will restrict the outflow from the pond to the design capacity of the existing 18” pipe at the northeast corner that is buried. Area C that drains onto Bentley Village will be reduced from 3.45 acres to 0.14 acres. Development will greatly improve the drainage for Bentley Village due to the significant reduction in the runoff onto and through their lots.
Of course, upon final design, the onsite system and the inlet location vary slightly, but the overall results will be the same.