Washington Street West watershed - City of Champaign

Draft ReportWest Washington Street Watershed Master Planis no local stormwater drainage system in place in this area and as a result it oftencontains standing water for several days after a precipitation event occurs. The open areaat this site is a rarity in this neighborhood and a requirement for a stormwater detentionstructure. Typically if open area does not exist, the City would be required to purchasehomes from local residents and convert residential neighborhoods into stormwaterdetention ponds. With only two homes located within this site, the removal of homes iskept to a minimum. The other benefit of this site is the proximity to the WestWashington Street trunk sewer, which will provide both an inflow and outflow to thedetention pond.The Alloy Casting Pond site has several limiting factors that reduce the effectiveness andoverall impact on the storm sewer system. Most of the site is owned by Alloy Casting,but there is a lone remaining resident that is reluctant to sell their property to AlloyCasting. There may be a reason behind Alloy Casting purchasing this land and it mayconflict with any plans to use this site for stormwater detention purposes. Stormwaterrunoff from the Alloy Casting Facility may also be a concern, since the building andparking lot form a large impervious area. Runoff from this impervious area wouldquickly flow to any detention structure at this site and consume storage volume intendedfor the West Washington Street trunk sewer. The local flooding in the western areas ofthis site would now be contained within a designated stormwater detention structure thatwould be design to properly drain after a precipitation event; however, the worst of theflooding is located a few thousand feet upstream of this location with only the WestWashington Street trunk sewer connecting the ponds to the flooded areas. This sewer isnot designed to convey peak flows into a detention pond and as a result a new stormsewer would likely be required to convey high peak flows from the worst flooding areasto the Alloy Casting Pond(s). The structures, roads and park that would form theboundary of this site would limit the use of this site as a regional detention pond byrestricting the maximum size of the pond.September 20096-5Clark Dietz, Inc.