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Solution to pollution in Bethany's Anchorage Canal

Shannon McNaught * Delaware
shannon.marvel@doverpost.com
Sussex Countian

Construction has begun on an innovative stormwater treatment project in the Bethany Beach area. It is the final step in the Delaware Center for the Inland Bays’ strategy to reduce pollution in the Anchorage Canal drainage area.

The Center for the Inland Bays, in partnership with local communities, the Delaware Department of Transportation and the University of Delaware, has been working for a decade to reduce runoff pollution into Anchorage Canal, which flows to Little Assawoman Bay.

The canal receives runoff from an over 100-acre drainage area that includes about a mile of Coastal Highway and the Sea Colony condominiums. About half of that area is covered by impervious surfaces.

Most of the area’s stormwater is collected through drains along Coastal Highway. It’s piped untreated to Anchorage Canal, polluting it with excessive amounts of nitrogen and phosphorus.

The excess nutrients, combined with poor flushing, cause heavy algae blooms in warmer months. The algae causes low oxygen levels that can harm fish and other aquatic life.

A decade of work

The Center found the Anchorage Canal and other canals that connect to Little Assawoman Bay to be in poor to fair condition in their 2011 State of the Inland Bays report.

They worked with DelDOT and the communities of South Bethany, Middlesex Beach, Bethany Beach and Sea Colony to develop a pollution and stormwater control strategy for the drainage area. Twenty-five improvement projects were deemed necessary in areas where storm water controls were either ineffective or didn’t exist.

In 2011, the plan was put into action by creating wet swales and infiltration pits to treat storm water from the 35-acre Sea Colony complex. The second phase involved creating 16 bioretention areas, which are engineered rain gardens, in the medians of the Coastal Highway to slow down and filter water. In 2014, 17 more bioretention areas were created within highway right-of-ways.

Completing the plan

In their final effort to significantly reduce pollution in Anchorage Canal, the Center is installing a pond and wetland with native vegetation. It will be built in place of the existing northbound turn lane off Coastal Highway onto South Pennsylvania Avenue. A new right-turn lane will be added at the intersection just to the south.

A walking and biking path will be added.

“It serves two key objectives by improving pedestrian safety and removing pollutants from runoff before the water goes into the canals and bay,” said John Gilbert, speaking on behalf of the Sea Colony Recreation Association, which helped with funding.

The total cost, including design and construction of the pond and roadway improvements, was $846,160. In addition to the Sea Colony Recreation Association, the DelDOT’s Transportation Alternatives Program and the Center for the Inland Bays also helped.

The Coastal Highway/South Pennsylvania Avenue project is expected to be finished mid-June and will mark the completion of the Anchorage Canal drainage area pollution and stormwater control strategy.

Eighty-five pounds of nitrogen and 41 pounds of phosphorus per year are expected to be removed.

“This is a significant achievement for clean water,” says Dr. Marianne Walch, the Center’s Science & Restoration Coordinator. “The Anchorage Canal stormwater initiative has been a great demonstration of how communities, government agencies and nonprofit organizations like the Center can work together to achieve important water quality goals.”

Further efforts

The Center is now working on a stormwater masterplan for Dewey Beach to mitigate flooding and improve water quality. The first two projects from that plan will be completed this spring.

Those projects include a living shoreline and outfall retrofit at the bayside end of Read Avenue and a bioretention area at the intersection of Read Avenue and Coastal Highway. Both are funded by the town, DelDOT and the Delaware Department of Natural Resources and Environmental Control’s community water quality improvement grant program.