zebra mussel eradication

[fishingwidow]

Saw a summary article on this in an industry mag. today. Seems pretty expensive, but successful. The links got some great background & further info. too.

http://www.dgif.state.va.us/zebramussels/

To kill the zebra mussels through exposure to potassium, the entire quarry was injected with 174,000 gallons of potassium chloride solution over a 3-week period from January 31 to February 17, 2006. The solution was delivered each morning to the site, and then pumped from land-based storage tanks through a floating supply line to a 22-foot work boat outfitted with a specially designed diffuser assembly on its bow. Potassium concentrations throughout the quarry and in adjacent surface waters were measured each weekend during the treatment. The target concentration was 100 milligrams of potassium per liter of water (mg/l, or parts-per-million - ppm); far below the level that would invoke environmental or human health concerns, but more than twice the minimum concentration needed to kill all the zebra mussels. Sampling at various depths and locations in the quarry after treatment revealed potassium concentrations ranging from 98 to 115 ppm, and no potassium leakage from the quarry into adjacent waters has been detected.

No land disturbance was required, as the staging area and setup occurred within the disturbed uplands surrounding the quarry. No disturbance of substrate or bottom sediments within the quarry occurred. No land disturbing activities in or adjacent to Broad Run took place, though Broad Run is being monitored for groundwater infiltration of potassium from Millbrook Quarry.

How do you know the treatment was successful?
Concentrations of potassium were monitored at various depths along transects established throughout the quarry, both during and after "charging" of the quarry, to ensure that lethal concentrations were achieved and maintained. Then, several weeks after treatment was completed, four separate methods of confirming eradication of the infestation were implemented. First, over a thousand mussels were scraped from rocks at numerous sites around the quarry during informal assessments, revealing no live mussels. Second, VDGIF scuba divers who had documented the extent of the infestation during pre-eradication studies conducted a visual inspection of the quarry, searching for live zebra mussels but finding none. Third, Aquatic Sciences L.P. conducted extensive video survey and documentation of the dead zebra mussels through use of a robotic camera. Finally, eighty bioassays of 100 live zebra mussels each were placed at various locations and depths throughout the quarry and thus exposed to the treated quarry water. After 31 days of exposure to the treated quarry water, 100% of the test mussels had died. None of the 100 "control" zebra mussels held in untreated water drawn from Broad Run died during their bioassay period. In dramatic contrast, other aquatic wildlife including turtles, fishes, aquatic insects, and snails continue to thrive in the quarry.