Washington Street West watershed - City of Champaign

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Draft ReportWest Washington Street Watershed Master Plan6.3.1.4 Regional Detention PondsInterstate 72 PondFigure 6-10Interstate 72 PondTable 6-9Interstate 72 PondPondSize(acres)PondDepth(feet)MaximumPond Volume(ac-ft)EffectivePond Volume(ac-ft)InletSewer(inches)OutletSewer(inches)1.9 11 20.0 15.0 30-42 12-18The Interstate 72 Pond is an identified potential pond location that is in open space that isnear the West Washington Street watershed. This pond is south of the West WashingtonStreet trunk sewer, but is actually located in a separate sewershed. The surface slopesand potential pipe slopes are feasible, but overall design would require additional surveyto determine the inlet and outlet sewer possibilities.This regional detention pond location is the only pond location that is relatively close andis downstream of the West Washington Street trunk sewer. The other regional detentionpond locations are either far from the West Washington Street trunk sewer or are locatedupstream of the Copper Slough discharge. No homes would need to be removed and apotentially larger pond footprint is possible. The existing parking lot is rarely used forparking and so there could be an opportunity to use this area for stormwater detention.September 20096-16Clark Dietz, Inc.
Draft ReportWest Washington Street Watershed Master PlanThe natural drainage of the parking lot is to the southwest and therefore would drain intothe detention pond. This surface inflow would consume pond volume and would increasethe drainage area to the West Washington Street trunk sewer. The land acquisition wouldbe expensive and the location of this pond relative to the watershed flooding wouldrequire additional storm sewer.Bradley Avenue PondFigure 6-11Bradley Avenue PondA large unused open space exists immediately south of Bradley Avenue, just east of theCopper Slough channel (see Figure 6-11), that could be potentially used for a regionaldetention pond location. This undeveloped area is currently owned by the ChampaignPark District; however, the Park District has not been amenable to converting park landinto stormwater detention areas.This location could accommodate approximately 48 acre-feet of stormwater detention(keeping it below 50 acre-feet helps to avoid a Dam Safety Permit) that can be used as adirect hydraulic control for runoff from the Washington Street basin. A 6-acre footprintwould provide enough storage volume to offset the impacts of increased stormwaterrunoff from the Washington Street basin sewer improvements. In order to convey peakflows to this pond a large diameter storm sewer would be required and is discussed as theCopper Slough Recommended alternative later in this chapter. The function of this pondis dependent on the channel profile and cross section modifications to the Copper SloughSeptember 20096-17Clark Dietz, Inc.
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Washington Street West watershed - City of Champaign

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