Dam and Reservoir Rehabilitation
City of White Plains, New York

J. Robert Folchetti & Associates (JRFA) was retained by the City of White Plains to perform the analysis, design, and construction supervision of its two water supply reservoirs. The system is served by a 450 acre watershed and the impoundments consist of two high hazard dam structures.

The two dams were built in the early 1900's and, although in relatively good condition, no longer meet the latest design safety requirements. One of the dams is of masonry construction and the other is an earthen berm with a rubble center. JRFA determined the modifications that were needed to bring the structures, spillways, channels etc. into conformance with NYSDEC dam safety criteria and allow the passage of the probable maximum flood storm event.

A hydraulic analysis was first performed, allowing for the development of a computerized model of the watershed. The model considered each dam spillway, gravity drainage piping, hydraulic control points etc. Since historical rainfall data could not predict the worst case storm event, the National Weather Service was contacted to obtain data on the probable maximum precipitation for the White Plains area.

From this analysis, alternatives allowing for rehabilitation of the system were developed. These alternatives ranged from structural improvements to total replacement of the dams. The recommended alternative was aimed at maximizing total storage capacity of the reservoirs while allowing the City to optimize use of its new water treatment plant.