A project to remove pollutants from storm water before it flows into Little Assawoman Bay is underway near Sea Colony.
The Delaware Center for the Inland Bays, working with Sea Colony and the Delaware Department of Transportation (DelDOT) is retrofitting the existing drainage ditch along South Pennsylvania Ave. to remove pollution in stormwater runoff before it enters a storm drain system that discharges to the Anchorage Canal.
This project is one of many storm water retrofit recommendations identified in a recent assessment of the area led by the non-profit, Center for Watershed Protection, and engineering firm, JMT.
“Part of the assessment project was to identify and prioritize projects that would meet the pollution reduction goal in the area,” said Chris Bason, of the Center for the Inland Bays.
He said they identified 25 different projects within the drainage area and sought to get the most “bang for their buck,” by picking projects that cost the least and remove the most nitrogen and phosphorus.
“This project was close to the top of the list,” he said.
It is also the first one to be implemented.
“The idea is to go in and get storm water quantity and quality controls where there were none or they could be enhanced.”
Bason said engineering firm JMT recommended expanding and reconfiguring the ditch that receives runoff from the high rises at Sea Colony to bio-retention areas, with the idea of trapping and holding the runoff longer, which helps to filter out the pollutants. The end result increases the area of wetlands which help to trap pollution and converts the area into a wet swail area.
Part of the project also includes a series of innovative infiltration pits to direct runoff from the Sea Colony parking lot into the ground where it is filtered before entering the ditch. According to the Center for the Inland Bays, a typical 10-acre surface parking lot will create more than a quarter of a million gallons of storm water after a one-inch rain storm. The project also includes installing filter strips to trap anything running off the highway. .
“Sea Colony saw this as an opportunity to not only do their part to treat runoff, but also as an investment in the beautification of their property,” said Bason. He also said Sposato Landscape will install plantings into a rich compost mix which should provide all the nutrition that the new plantings will need without using chemical fertilizers.
Bason said the work goes toward the goal of the Pollution Control Strategy, which encompasses many voluntary actions that can be taken to help clean up 4500 acres of these types of areas. When completed, in early May, the project will treat runoff from 35 acres, removing excess nutrients nitrogen and phosphorus, as well as bacteria and oils from the water before it reaches the bay.
Sue Barton of the University of Delaware designed the planting scheme for the project, which will include native wild flowers, shrubs, and trees to help slow the water entering the system and process toxins and nutrients.
Planning is also underway with Middlesex Beach and the Town of South Bethany to install a series of bio-retention and infiltration areas in the Coastal Highway-Route 1 median. They plan on using Barton again for the native plantings to help with continuity of the projects.
The project was designed by JMT, and is being implemented by David A. Bramble Inc.
The project is funded by the Delaware Department of Natural Resources Community Watershed Improvement Grant Program, Sea Colony, and the Center for the Inland Bays.
What's the problem with stormwater?
Stormwater is a leading cause of water pollution. In communities built-out prior to more recent stormwater management practices, water from rainfall and snow melt flow directly off of roads, parking lots and other impervious surfaces and into our rivers, streams and bays.
As it washes across paved surfaces, it collects oil, pesticides, fertilizers, sediments, bacteria, and other nutrients and chemicals that can kill aquatic life, make water unsafe for swimming and recreation, and contaminate fishing waters.
Some studies have found that approximately 90 percent of the pollutant-loading is contained in the “first flush” of a one-inch rainfall. Therefore, effective water quality protection requires the treatment of the “first flush” through the use of various preventive and control measures such as this project will provide.
The Center for the Inland Bays is a non-profit organization established in 1994 to promote the wise use and enhancement of the Inland Bays Watershed through habitat protection and restoration, science and research, education and outreach and effective public policy.