Our story begins back in 2009, when D&B Engineers and Architects, P.C. was retained by the Village of Scarsdale to develop a comprehensive Storm Water Management Plan. The plan was designed to focus on a long term Capital Improvement Program to achieve water quality improvements and flood mitigation. Emerging as a high priority area contributing to critical flooding locations, the South Fox Meadow Drainage Basin was targeted for improvements, as it discharges directly to the Bronx River Basin. Accordingly, since 2009, the Village and D&B have been busy planning, designing and constructing a number of innovative and exciting storm water improvement projects “showcasing” a unique blend of green storm water practices and flood mitigation techniques. Two specific Green projects are highlighted below.
The Brewster Road Watercourse Stream Stabilization Project. The South Fox Meadow Brook stream bank, just west of Scarsdale High School, was one of the initial projects implemented as part of the Scarsdale Storm Water Management Program. During wet weather events, the velocity of the stream through this portion of the corridor was considerable and caused stream bank scouring and sediment deposition. D&B developed a plan that included stream de-silting to restore the volumetric carrying capacity of the stream channel and installed turf reinforcement mat (TRM) system to protect the stream banks from further erosion. The TRMs were complimented by articulated concrete block and stone rip rap that allowed grass to grow, giving the area a natural look. Using RUSLE model calculations, D&B estimated that sediment, the number one pollutant in the total stream and river segments, was reduced from 40 tons per year to less than 1 ton per year.
The South Fox Meadow Brook Drainage Improvement Project. This project was an opportunity for the Village of Scarsdale to mitigate the frequent flooding that occurred along portions of the South Fox Meadow Brook stream bank. First, HEC-1 and HEC-RAS storm water modeling was completed to identify locations along the stream corridor that offered the greatest potential for reduction in storm water flows, as well as the most benefit for adjacent homes. Two sites were selected for dry-detention ponds. A 10-acre dry detention pond installed at George Field Park was designed to reduce peak runoff flows by 70% during a 3.5 inch rainfall event and a second 3-acre dry detention pond installed at Cooper Green was designed to reduce peak runoff flows by over 50% under the same rainfall conditions.
In addition, a number of Green practices were implemented at these two sites to improve the quality of the water discharging to the stream, including:
One of the largest engineered wetlands in Westchester County was located at George Field Park. A 40,000 square foot area was cleared of invasive plant species, regraded and planted with native species that naturally remove pollutants from the water, as well as create a significant local habitat.
- Over 500 feet of grassy swale was constructed at George Field Park to capture and treat runoff from Greendale Avenue.
- Almost 3,000 square feet of Flexi-Pave®, a 100% pervious surface manufactured from recycled tires, was installed as a walkway between the two sites, which allowed for the removal of all impervious surfaces at Cooper Green.
- Straddling the Flexi-Pave walkway at Cooper Green is also a 3,000 square foot rain garden, which is one of the largest of its kind in Westchester County. The rain garden was planted with flowering indigenous plant species and is designed to allow storm water to pass through the soil “filter” as a means of improving water quality, thereby reducing the potential for pollutants to impact the stream.
The Water Quality Improvement Project at the Public Library. This project is in the design phase and will include the installation of 1,800 square feet of rain garden to treat storm water runoff from the 18,000 square foot library roof, which drains to the South Fox Meadow Brook. This will allow 90% of the 500,000 gallons of runoff per year to infiltrate the ground thus reducing runoff volumes and improving water quality. The rain garden is designed to treat and remove 60% to 80% of the nitrogen, phosphorus, roof metals and sediment prior to the water leaving the site. In addition, a rain cistern system will be installed to capture roof runoff and use the water to irrigate the rain garden, as well as the surrounding landscaping. The system will operate using a Rain Bird ET Manager®, which measures the amount of precipitation and automatically supplies water to the underground drip irrigation system. This type of system virtually eliminates the need to use potable water for irrigation and will save up to 40,000 gallons per year in water usage. A Trident Shark ADS® open channel flow meter will be fitted into the existing drainage manhole to measure the runoff flow in order to identify the reduction in runoff realized by the rain garden infiltration system. The flow meter will operate on a wireless modem and can be started automatically when rain is detected or via a cell phone.
The South Fox Meadow Brook Improvement Project and the Harcourt Woods Improvement Project were partially funded by the Westchester County Flood Mitigation Program. The Library Rain Gardens were partially funded through the Bronx River Watershed Initiative and the National Fish and Wildlife Foundation. All projects meet the objectives set forth in the Village-wide Comprehensive Storm Water Management Plan and the Bronx River Watershed Assessment and Management report and the design of the improvements are consistent with the New York State Department of Environmental Conservation (NYSDEC) Better Site Design and Storm Water Management Design Manual and incorporate “Green Infrastructure” principles where prudent.
Flexi-Pave Walkway and Rain Gardens at Cooper Green Park
The projects highlighted above represent just a few of the innovative storm water management assignments being planned, designed and implemented by the D&B White Plains and Woodbury offices, and forward-thinking clients such as the Village of Scarsdale.
Collectively, these projects showcase D&B Engineers and Architects, P.C.’s commitment and competency in advancing and integrating Green principles and practices into engineering solutions for our clients. Please contact Rob DeGiorgio, P.E., Vice President, at
(914) 467-5300 ext. 16, for more information.