17) Gardens Lake in Sheldrake River, Mamaroneck
The Sheldrake River begins in the northern neighborhoods of New Rochelle, flowing south through several man-made ponds. The northernmost is Carpenters Pond, followed in order to the south by Dickermans Pond, Sheldrake Lake, Goodlife Pond and, finally, Gardens Lake. Each of these impoundments, or ponds, is formed by a dam across the Sheldrake River. Each traps sediment from the river. In fact, Dickermans Pond is no longer a pond at all. It had completely filled in with sediment, providing a medium for invasive plant species like common reeds (Phragmites) and Japanese knotweed.
Gardens Lake is surrounded by a residential neighborhood and Interstate 95. Known as the “duck pond,” this lake also experienced rapid sedimentation, requiring periodic and costly dredging. The accumulation of sediment degraded the lake’s ecosystem and water quality in not only the lake but also the downstream Sheldrake River, Mamaroneck River and Long Island Sound. It also detracts from the lake’s recreational and aesthetic values. The lake, however, has now been fully rejuvenated as part of a comprehensive, multi-phase restoration project completed at the end of 2010. The first phase of this work in 2004 involved the construction of a sediment trap where the Sheldrake River enters the lake. The trap consists of a concrete block and stone weir (underwater wall) across the lake's entrance. Sediment, leaves and other material carried by the river into the lake will drop out of suspension by the slower waters behind the weir, thereby preventing it from entering the lake. The sediment trap needs to be cleaned out at least once a year, but this will be far less costly over the long-term than dredging the entire lake.
The second project phase focused on dredging the some 9,500 cubic yards of sediment from the lake and disposing of this material at off-site locations. This phase included the installation of bypass pipes and control valves to let the town draw down the lake’s water level prior to large storms. By doing so, the town will be increasing the lake’s water storage capacity, thereby allowing the lake to store a greater volume of storm water and helping to lessen the risk of downstream flooding. This phase also included the construction of a band of wetland along part of the lake edge and conversion of lawn surrounding the lake into meadow. Both of these habitats will help improve the lake’s water quality and ecological value. Finally, several catch basins handling drainage to the lake were replaced with units that more effectively capture sediment before it gets into the lake.
To View The Site: The site is next to Myrtle Boulevard and Lakeside Drive (off of Weaver Street) in the Town of Mamaroneck. The pond is surrounded by town parkland and a walking path runs alongside its western and northern shores.
Stephenson Brook originates in the northern neighborhoods of New Rochelle, flowing through the Wykagyl Country Club golf course on its way to Long Island Sound. A well-fertilized fairway lawn flanking a pond on the golf course had been adding an excessive amount of nutrients to the pond before a restoration project was completed in 2000. A small dam across the brook formed the pond. To reduce the amount of nutrients flowing into the pond, brook and, ultimately, Long Island Sound, the County removed sediments and decaying leaves from the pond and created slightly submerged "shelves" around the pond perimeter using surplus sediment held in place by logs made of coconut fiber. The "shelves" were then planted with a variety of aquatic plant species, including yellow iris and buttonbush.
A former plant nursery for Playland Park, this site was abandoned and evolved into an upland meadow. Non-native and invasive porcelain berry vines (Ampelopsis brevipedunculata) eventually overtook the site. The vines smothered most plants in the meadow, including several trees. To combat this invader, the vines were cut and removed by machine. As they re-emerged, they were sprayed with a systemic herbicide. The soil was then tilled and the site re-planted with native grasses and wildflowers. The meadow is now home to a variety of plants and used by birds, mammals and beneficial insects. The meadow also removes pollutants from stormwater runoff before it reaches Long Island Sound.
This popular freshwater pond suffered from sedimentation and excessive amounts of nutrients. It was restored by removing a considerable amount of sediment from the pond, building a weir across the incoming stream channel to trap sediment before it reaches the pond, and creating a pond edge and adjacent conservation buffer strip of native plants around most of the pond. This vegetation filters out stormwater pollutants and enhances wildlife habitat.