A severe flood risk persists in the Village of Mamaroneck, NY along the Mamaroneck River and Sheldrake River based on the recurrence of flood events and the damages sustained.  The largest floods of record resulted from the storms of October 1955, June 1972, September 1975, and April 2007.  Extensive damages and loss of life have occurred during these major flood events.  Damages within the Mamaroneck and Sheldrake Rivers Basin for the June 1972 and September 1975 floods alone amounted to approximately $18M and $92M, respectively, based on conditions of development at the time and October 2015 price levels.  A combination of low channel capacity, small bridge openings, developmental encroachment along both rivers, urbanization, and a poor flow conveyance at the confluence of both rivers has contributed to significant and frequent flooding.  

A Chief of Engineer’s Report was signed on 14 Dec 2017. This General Reevaluation Report (GRR) was being conducted after interest peaked following storm events in 2007, which struck the Mamaroneck and Sheldrake Basin flooding homes and businesses.  This GRR was an attempt at resolving issues with previous studies that yielded a 1977 Feasibility Report and a 1989 General Design Memorandum (1989 GDM) which did not proceed to construction due to concerns of the non-Federal sponsors relating to the costs and separable element justification. 

A Design Agreement was signed by the District and NYS Department of Conservation (NYSDEC) and Westchester County for the GRR Study and Preconstruction Engineering and Design (PED) on 1 Mar 2010. The Chief of Engineer’s Report proposed a National Economic Development (NED) plan at a total first construction cost of $127,416,000 (FY 2024 price level). Since the Chief’s Report was signed, the total project cost estimate has increased, which necessitated a full examination of the project economics at the Headquarters level. The team completed this review and received approval to proceed with design of the Ward Ave. bridge demolition and replacement to 100% Plans and Specifications. Concurrently, the team is also going to advance the design for the other features of the project (bridges, channel work, non-structural features, etc.) to approximately 30% in order to achieve a certified cost estimate. Completion of the Ward Ave. bridge design and the certified cost estimate will enable USACE to execute a Project Partnership Agreement with the non-Federal Sponsor and proceed into the construction phase. The outstanding design work is anticipated to conclude in 2028 with the PPA being completed the same calendar year.

For more information, please read the following:

Fact Sheet

Project Placemat

Watershed Map 

Main Report