Washington Street West watershed - City of Champaign

Draft ReportWest Washington Street Watershed Master Planpond would be served primarily by the 24-inch trunk storm sewer on North McKinleyAvenue and would discharge further downstream when the sewer is 36 inches indiameter. The purpose of this pond is to intercept as much of the North McKinleyAvenue trunk sewer flow before the flow reaches the downstream sections andoverwhelms the West Washington Street trunk sewer.The size and location of this pond obviously is not a standalone regional detention pondoption, but it does work well in a multiple pond design by providing relief to the NorthMcKinley Avenue trunk sewer. The upstream location allows the pond to beginaccepting flow before the downstream sewers become overwhelmed, providing relief anda slight delay to the surcharged sewer conditions. The pond may be expandable, althoughthat depends on the willingness of the concrete facility, but the benefits of this location isthat no homes would need to be removed to construct this pond. The other benefit is thatvery little new storm sewer would be required to construct a detention pond at thislocation.The limitations of this site hinges on the willingness of the concrete facility to sell thisland to the City. The runoff issue with this site is similar to the Alloy Casting pond siteand the possibility of impervious area runoff flowing directly into the pond andconsuming storage volume intended for the North McKinley Avenue trunk sewer exists.The depth of the receiving sewer also reduces the maximum volume of this alternativewith the hydraulic conditions downstream remaining for large storm events.September 20096-11Clark Dietz, Inc.