Project Scope & Design Considerations
The purpose of the project is to improve the water quality and reduce the stream flow into the downstream creeks, rivers, and eventually the Chesapeake Bay. The way to do this is to stabilize the streambed and improve the connection between the streambed and the floodplain. The extent of this project is for the entire length of the streambed upstream of the crossing under Wakefield Drive. In addition to the main streambed, several stormwater outfalls that feed into side streams joining the main stream will also be part of the project. The most visible of these tributary streams are crossed by Golden Gate, Natural, and Tappan Zee bridges.
The objective is to do this in a manner that preserves the natural ambiance of the parkland. There are several side benefits to a project such as this. The renovated streambanks are better vegetated with native plant species. Fish and other aquatic animals can have improved habitat and repopulate restored streams fairly rapidly after the construction is complete.
Several remediation concepts will likely be applied to this project, including:
- The areas immediately downstream of the stormwater outfalls will be reshaped to dissipate some of the flow energy.
- The streambed will be substantially raised using large rocks and fill and the remaining smaller streambanks will have a much more gradual slope so that significant stormwater will overflow the streambanks into the natural floodplain.
- Native species will be planted along the gradually sloped streambanks. Biodegradable matting is applied to stabilize the streambanks for the first year until the vegetation takes hold.
- A series of riffles (shallow areas with turbulent water flowing over rocks) and pools will be created in the main stream.
Some of the design objectives include:
- Minimize the loss of healthy mature trees.
- Minimize the width of the swath necessary for construction equipment access.
- Maintain the current natural ambiance of the parkland. Materials brought in will be compatible with the current parkland environment.