Chateau Eau Plaines Stormwater Improvements

raSmith was retained by the Village of Pleasant Prairie to prepare a storm sewer design that would completely convey Unnamed Tributary No. 1 to Kilbourn Road Ditch along 115th Avenue in Chateau Eau Plaines. The project area is single-family residential with roadside ditches and culverts. Localized flooding and drainage problems have existed in Chateau Eau Plaines for over 15 years. Flooding in 2009 was compounded by power outages, which affected sump pumps and the sanitary lift station. The subdivision was prone to flooding because the topography is flat and the roadside ditches were constructed at very flat grades and have been enclosed in some areas. In addition to the ditches being flat, sump pumps are very active in the area, causing nuisance conditions. Many residents have taken it upon themselves to place drains or other homemade structures in the ditches to try to get water to drain.

raSmith staff prepared a design of a new storm sewer system which fully contains the 1% annual chance (100-year) flood event. This design reduced the flooding during significant rain events and eliminated mapped floodplain along the residential properties. raSmith worked to update the effective hydraulic model and obtained a Conditional Letter of Map Revision (CLOMR) from FEMA prior to construction. Once construction was completed, raSmith verified the model based on survey information and completed a Letter of Map Revision (LOMR) to remove the mapped floodplain along the various residential lots.