Millbrook Quarry Zebra Mussel Eradication

Agency: Virginia Department of Game and Inland Fisheries

Location: Virginia

Treatment Type: Toxicant

Treatment Method Used: Potassium Chloride/Potassium Hydroxide

In August 2002, the Virginia Department of Game and Inland Fisheries received a report that zebra mussels were present in Millbrook Quarry. Surveys revealed a density of 20,000-30,000 zebra mussels/m2 present in the quarry. This project was designed to evaluate and select a method of eradication for long-term control of zebra and quagga mussels at Millbrook Quarry.

From 2002 to 2006 the project focused on evaluation, protocols and techniques, as well as on review and emergency procedures. In February 2006 gradual application of potash was carried out over 3 weeks until a final target concentration of 100 ppm was achieved. The site was cleaned up in less than one week, at the target concentration, and eradication was confirmed 6 weeks post-treatment with scuba diving and with video documentation. No zebra mussels were found in the water periphery and no other aquatic animals (i.e., fish) appeared to be affected. From 2006 to 2008, a post project monitoring allowed further analyzation of water chemistry and micro-benthos and showed no significant changes in the system. Further, no anticipated increase of potassium or chloride was detected. At 8 years post-treatment, project follow up (2013-2014 field seasons) confirmed that no adult mussels or veligers have been detected and found and that potassium concentration has declined about 36% without additional changes.


Richmond, V., 2005. Final Environmental Assessment Millbrook Quarry Zebra Mussel and Quagga Mussel Eradication.

Partner Agencies: 

Virginia Department of Environmental Quality


Raymond T. Fernald and Brian T. Watson, Virginia Department of Game and Inland Fisheries

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