The existing high flood flows are due to a very large tributary area. The Concord-Interlaken pond overflows for extreme storm events. The existing storm sewer system has insufficient capacity. Overland flow routes are through residential side yards with insufficient capacity. Insufficient storage within the watershed and no available open space for significant new storage contribute to the flooding.
Install a new overflow structure and modify the existing restrictors at the Concord-Interlaken pond. Install a new larger diameter relief storm sewer from the Concord-Interlaken pond along Butterfield Road and Winchester Road all the way to the eastern Cambridge-North detention basin. Modify the restrictor of the detention basin at Windhaven Road immediately south of Interlaken Ridge ponds. Install a new storm sewer just east of the ComEd right-of-way to drain the depressional area. Modify the east overflow of the Loyola Ponds. Install a new storm sewer to drain the Wilshire Court detention basin and route drainage to the eastern Cambridge North detention basin. Reconstruct the outfall at the Cambridge-North detention basin.