Government Center Stream Restoration Project


Joint Board Matter with Supervisor Gross
June 19, 2012

Government Center Stream Restoration Project

Madame Chairman,

Supervisor Gross and I would like to share information with you on an exciting project recently designed and constructed by the Stormwater Planning Division. This project is an innovative stream and pond restoration of an unnamed tributary of Difficult Run here at the Government Center. This project has been a unique and cooperative public/private partnership between several County agencies and Wetland Studies and Solutions, Inc (WSSI). WSSI donated services in excess of $100,000 to explore a new technology which may be able to be successfully duplicated on other sites.

In a nutshell, approximately 1,000 linear feet of this badly eroded channel, dry pond and two wet ponds were restored and stabilized; improving volume and water quality function, and re-establishing aquatic and  benthic macro-invertebrate populations in the stream. It also created a positive re-use of sediment dredged from an old farm pond that was in use before the Government Center was built. These ponds and channels serve as an outfall for the Government Center, the Herrity/Pennino complex and part of Fairfax Corner. 

Approximately 800 to 1,000 cubic yards of sediment were dredged from the upper pond and hydraulically blown into geotubes manufactured to fit the width of the eroded streambed.  The sediment was stabilized and ‘thickened’ with a polymer, and water was allowed to drain from these tubes over a period of weeks to form an under-layer for the newly raised streambed. After the water had drained, new fill was placed atop the tubes and anchored with natural boulders, rip rap and even hardwood trees that were harvested from the site. Staff was also able to accomplish the restoration with significant tree preservation. Moving forward, this project will annually remove 10.7 pounds of phosphorous, 20.2 pounds of nitrogen, and 1.5 tons of sediment per year.

This project is truly an innovative and holistic approach to stream restoration and offers exciting future possibilities for what is now the expensive cost to dispose of dredge material from ponds and lakes. It traps the nutrients and metals contained in the sediment that are known contaminants for the Bay. Although it now appears that this technology has proven to be successful, both staff and WSSI took a real gamble on a new concept.

I ask unanimous consent to bring WSSI and the multi-staff team who participated in this project before the Board to be recognized and to provide us with more details on the important aspects of this construction. I also ask that Public Affairs arrange a guided tour for Board members to see this beautifully restored stream.

 


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