Case Study - Shoecoft Lake, Snohomish, Washington The Problem Eurasian Milfoil was rapidly colonizing this 160 acre residential lake north of Seattle, WA. This invasive weed was well established in the northern and southern bays of the lake. In addition to the problem posted to this lake, a stream system connected the lake to a chain of additional residential lakes downstream. While Sonar Aquatic Herbicide has been used routinely by our firm to eradicate this invasive weed from impacted lakes, a whole lake treatment was beyond the resources available to the commumity. In addition, there was a downstream tribal fish hatchery that was concerned about any product applied to the lake. The Solution A Unique Barrier Curtain System to isolate the treatment areas. This project was the first every to utilize a barrier curtain to contain an aquatic herbicide in close proximity to the target areas while not impacting the rest of the lake. The southern curtain covered approximately one half mile and isolated 22 infested acres. The northern barrier was approximately 900 feet long and isolated about 5 acres. Sonar AS was applied at two week intervals to maintain a lethal dose and FasTEST monitoring was performed both in the treatment areas and outside the barriers. The results were stunning. The milfoil was completely controlled within the enclosures, there was no herbicide detected outside the barriers and hense no impact to the native plants in the lake and now downstram movement of this material. Regular diver inspections have documented that the lake remains milfoil free five years post treatment