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The Lofts at Saw Mill Hasting-On-Hudson, NY

Geotechnical Engineering, Land Planning, Water Resources

An aerial view of three residential buildings backed by trees.

The Lofts on Saw Mill River, developed by Ginsburg Development Companies (GDC), required a multi-step stormwater design. SESI Consulting Engineers engineered the stormwater management system to collect, transport, store, and treat stormwater throughout the site and then discharge directly into the Saw Mill River. The Lofts on Saw Mill River sit on approximately 7.45-acres and are located in the Village of Hastings-on-Hudson, NY. The location takes advantage of the outdoor recreational opportunities afforded by the South County Trailway while offering a quick commute to Manhattan, White Plains, and other major economic centers.

A perfect residence for the everyday explorer, The Lofts consists of three multi-unit luxury residential buildings. Construction for the site included associated paved roadways, parking, and landscaped areas. The adjacent South County Trailway stretches from Van Cortlandt Park in Yonkers 15 miles to Tarrytown’s Lakes Park where it meets the 22-mile long North County Trail. The Lofts residence has access to the trail by a newly constructed pedestrian bridge over the river, providing access over the Saw Mill River to the South County Trailway for biking and hiking. SESI provided all coordination and construction oversight for the construction and bridge placement over the Saw Mill River. SESI also provided the permitting through the Village of Hastings-on-Hudson, the Department of Environmental Conservation, and the Westchester County Parks Department.

Stormwater is impacted when precipitation falls on some impermeable surfaces. The water picks up various chemicals along its path- i.e. motor oil in the parking lot, fertilizers in the lawn, etc- which can affect the ecosystem of the waterway to which the runoff flows. This site utilizes two stormwater infiltration systems as the project’s Best Management Practices (BMPs) to treat stormwater runoff from a majority of the development area prior to direct discharge into the Saw Mill River. One of the infiltration basins utilizes a vortex valve, to further reduce discharge rates. There are also several minor drainage areas which, due to site topographic constraints, cannot drain to the infiltration systems. Runoff from these areas is carried to Contech CDS-4 manufactured stormwater treatment devices, which are approved by NYSDEC. Once treated, the stormwater runoff is conveyed through the manholes and pipes and ultimately discharged into the Saw Mill River.

Additionally, the stormwater management design incorporates the use of permeable pavers along the perimeter of the site access road. These pavers help to treat the stormwater, and allow for infiltration and groundwater recharge. This process of treatment and recharge takes time and therefore reduces immediate runoff from the site while the pavers add aesthetic value to the project.

As a result of the innovative stormwater treatment measures employed on the site, the impervious coverage for the property decreased from 2.31-acres pre-construction, to 1.98-acres in the developed condition. This reduction in impervious coverage generates a benefit by reducing the amount of stormwater runoff and how quickly it exits the site. Due to the design nature of the two infiltration facilities and permeable pavers, treated runoff will infiltrate into the ground through different soil media to remove contaminants, and has the added benefit of further reducing peak runoff discharge to the Saw Mill River.

The Site Engineering Design, State Agency Permitting, and Geotechnical Design Services were all performed by SESI Consulting Engineers D.P.C. In addition, SESI provided full construction observation during the building and site construction.

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