Blue Ridge Manor - Infiltration Experiment

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What is polluted runoff?

Parts of the Chesapeake Bay watershed contain a high percentage of impervious cover – paved or other hard surfaces such as roofs and roadways that prevent rain water from being absorbed into the ground.  Instead, water runs along these surfaces, collecting trash and substances such as motor oil, lawn fertilizers, and pesticides.  This polluted stormwater flows into streams and rivers, where it threatens aquatic ecosystems and public health.  

Effective stormwater management, on the other hand, creates safe paths for polluted runoff to be captured and filtered through the ground before it reaches waterways.  This helps keep the environment clean and our communities healthy!

Overgrown detention basin. Credit: Carroll County.
A surface sand filter with experimental flocculants corrects the drainage issues and serves as a trial run for best practices. Credit: Carroll County.

Project Location: Town of New Windsor, MD

Problem: The detention basin at the Blue Ridge Manor facility in the Town of New Windsor was constructed in the early 1990s during the time when stormwater management focused more on flood control than water quality. Erosion at the outfall, overgrown vegetation, trash, and steep slopes surrounding the basin led to this facility being retrofitted in the fall of 2017.

Solution: Carroll County worked closely with the Town of New Windsor to design and re-construct the facility. The upgraded facility now uses a surface sand filter that provides water quality treatment, channel protection, and peak flow management of a ten year storm for a 31-acre drainage area. While the filter is currently standard practice, the county is striving for an even more cost effective treatment.

Unique aspects of this design are two distinct filter areas in the bottom of the facility each having their own separate underdrain system beneath the filter media. Both filters have the county’s standard sand, soil, and green woodchip materials. One filter includes biochar, a commercially available carbon source, similar to charcoal, which studies indicate increases nitrogen removal. The second filter includes alum, a waste by-product from water treatment processes, that has been shown to reduce phosphorus.

Both filter systems are being monitored by county staff to determine effectiveness of this enhanced filter media. Study results are expected in 2019.

Drainage Area: 31 acres

Impermeable Surface Area: 9 acres

Cost: $531,558 overall

Per acre cost: $59,062

Funding Sources: Maryland Department of Natural Resources grant of $225,490 and joint county/municipal funds of $306,068

Partners: Center for Watershed Protection, Town of New Windsor

Contact information:

Gale Engles | gengles@carrollcountymd.gov | 410-386-2659
Carroll

Key project facts

Project Type:
Bioretention
Scale:
$500,000 - $749,999
Story Focus:
Cost Efficiency, Environmental Benefits, Monitoring
Stormwater Utility Funds:
No
Problem Addressed:
Erosion, Failing Infrastructure, Flooding / Drainage, Runoff Pollution
Year Installed:
2017
State Legislative District:
5
Congressional District:
MD 8th