Using Best Management Practices to Control Stormwater at Lemon Creek Watershed

The BMP is an example of an existing basin retrofitted to provide extended detention along with a pond/wetland system. The unique hydraulic design of this BMP provides for dynamic detention with multiple low–flow discharge orifices and an overflow weir. This configuration of the outlet structure provides for the varying discharge flow rates during a rainfall event, thereby maximizing the peak flow attenuation while utilizing the optimized storage.

In addition we installed cascade structures made of rock to mitigate some of the hydraulic grade within the BMP facilities and these functioning cascades added to the aesthetics of the facility. The other unique feature of this retrofit was to provide for forebays at each of the two inlets for sediment capture and velocity attenuation. Overall this retrofitted BMP restored the functionality of the existing basin and at the same time provided water quality improvement, aesthetic enhancement and community benefits.

Other BMPs in the Lemon Creek Watershed include:

• An extended detention pond and micropool at the site of Porzio’s Pond

BMPs were constructed for both the inlet and outlet conditions to eliminate chronic flooding on Woodrow Road. This BMP handles runoff from an area of about 110 acres. To alleviate flooding, an outlet structure in the form of a riser box, with a micropool, were constructed within the pond. The riser box, which provides extended detention, creates a natural variation in water surface elevations while providing for additional storage capacity in the pond, to reduce downstream flooding. Also, the stream that flows downstream of Woodrow Road is maintained by a low flow pipe under the road. This relieves both flooding and bank erosion in the downstream portion of the creek and also provides a supply of water to the Convent Avenue wetland restoration project.

• An extended detention shallow marsh wetland, serving a 130-acre drainage area

The 1.3-acre site is located along the southern end of Convent Avenue. This BMP serves to relieve localized flooding as well as provide an outlet for the storm flow bypass from Porzio’s Pond. Storm flow is detained here and released over a 24-hour period through an outlet weir. The BMP also includes an inlet forebay to aid in the settlement of suspended solids, provision of wetland plantings for nutrient removal, and associated water quality improvements.

• A constructed wetland with an inlet forebay and stabilized outlet that attenuates flow velocities and reduces potential scouring of banks

The inlet forebay aids in the settlement of suspended solids, and the low flow meandering channel assists in flow conveyance. It handles a drainage area of approximately 33 acres.

Project Outcomes and Benefits

• BMPs include constructed wetlands, meandering streams, and other features that provide a natural drainage corridor to convey stormwater runoff. They also remove pollutants and promote terrestrial and aquatic life.
• The Lemon Creek Watershed includes approximately 1,366 acres. Among the eight constructed BMPs are an extended detention basin (Porzio’s Pond) at Woodrow Road, an extended detention shallow marsh system at Convent Avenue, and a constructed wetland with an inlet forebay and stabilized outlet at Amboy Road.