|Fayette Square Stormwater Retrofit Project|
Stormwater runoff occurs when precipitation from rain or snowmelt flows over the land surface. The addition of roads, driveways, parking lots, rooftops and other surfaces that prevent water from soaking into the ground to our landscape greatly increases the runoff volume created during storms. Stormwater runoff also picks up and carries with it many different pollutants that are found on paved surfaces such as sediment, nitrogen, phosphorus, bacteria, oil and grease, trash, pesticides and metals.
The Fayette Square Stormwater Retrofit Project will utilize green infrastructure to capture, cleanse and reduce stormwater runoff using plants, soils and microbes. At the site scale, green infrastructure consists of site-specific management practices (such as interconnected natural areas) that are designed to maintain natural hydrologic functions by absorbing and infiltrating precipitation where it falls. Bioretention areas function as soil and plant-based filtration devices that remove pollutants through a variety of physical, biological, and chemical treatment processes. Stormwater is collected into the treatment area which consists of a grass buffer strip, sand bed, ponding area, organic layer, planting soil, and plants. Runoff passes over or through a sand bed, which slows the runoff's velocity and distributes it evenly along the length of the ponding area. The ponding area consists of a surface organic layer and/or groundcover and the underlying planting soil. Water is ponded and gradually infiltrates the bioretention area or is evapotranspired. Stored water in the bioretention area planting soil exfiltrates over a period of days into the underlying soils before water is recharged into Wolf Creek.
Currently, the shopping center parking lot has four concrete gutters that convey surface runoff directly to Wolf Creek. The storm drainage system is not regulated under the National Pollutant Discharge Elimination System permit program, or any city or county ordinances, thus they are considered “non-point” sources. The surface runoff from the parking lot is known to contain oil, grease, and toxic chemicals that are harmful to biological life. In the winter months an added elevation of salts, from de-icing, also enters the stream. To remedy this problem, the proposed project will eliminate direct surface runoff from the Fayette Square parking lot to Wolf Creek. The project will involve removing/ disconnecting four concrete gutters from the parking lot and installing a bioretention filter strip. The bioretention filter strip will be installed between the edge of the parking lot and Wolf Creek, and will serve to reduce pollutants and sedimentation from stormwater runoff before this water enters Wolf Creek.
Long term Goals/Objectives
• Remove concrete plumes from the South Parking lot
• Install bioretention cell to slow down stormwater and filter surface runoff before entering Wolf Creek
• Install interpretive signs to explain stormwater management and BMP practices
Currently surface water flows directly from the parking lot into Wolf Creek