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Sacheen Lake, a 320-acre lake located in Pend Oreille County in Northeastern Washington, supports a variety of beneficial uses including fishing, wildlife observation, swimming, water skiing, and boating. The lake is heavily used by lakeshore residents and is regarded as an amenity by the local community. A lake restoration project performed between 1990 and 1998 appears to have controlled the growth of algae and temporarily controlled a serious infestation of Eurasian watermilfoil (Myriophyllum spicatum). In recent years the continued growth of milfoil has presented a considerable challenge to the lake residents who have been funding ongoing management efforts. These efforts have included spot treating with granular 2,4-D and using diver hand removal techniques.
Sacheen Lake was treated with 2,4-D (AquaKleen) on July 8, 2003. AquaKleen was applied using a granular blower at a rate of 100 pounds per acres by a licensed applicator. A total of 35.5 acres were treated at scattered locations around the littoral zone of the lake. DMA*4IVM (liquid formulation) was applied at a rate of two gallons per acre foot to Moon Creek using a drip system under a Special Local Needs label. Moon Creek flows into Lake Sacheen and milfoil growing in Moon Creek continues to reinfest Sacheen Lake. Hand removal techniques in the Creek were not successful in removing all the milfoil. Approximately 0.3 acres of Moon Creek was treated starting on July 8 and ending on July 10, 2003.
Sacheen Lake: Samples were collected from inside and outside (see below) of three treated areas by Sacheen Lake residents who had been trained in sample collection by an environmental consultant. The samples were taken using a Kemmerer sampler at a depth of 2 meters at 24 and 72 hours after treatment.
Site 1
was 100 ft up into the North channel of Moon Creek,
Site 2 was 200 ft out into the lake from the mouth,
Site 3 was in Granite Shores Bay, approximately mid-bay off the Public
Utility District water system intake and approx. 100 ft off the treated
area,
Site 4 was in a 0.1acre treatment area,
Site 5 was in the Narrows treatment area, approx. 3 acre treated,
Site 6 was approx. 500 ft west of the treatment area,
Site 7 was within a 2 acre treatment area at the North end of the lake, and
Site 8 was 300 ft out from the North end treatment area.
Moon Creek: Samples were collected from mid-depth in Moon Creek using a Kemmerer sampler 24 and 72 hours after treatment. The Moon Creek drip application was started at approximately 6 pm on July 8 and ran continuously for 48 hours. The applicator reportedly determined the creek flow through a culvert adjacent to the drip system placement in order to determine the drip rate and tank mixture to achieve the target concentration in the creek flow over this period.
All 2,4-D samples were stored on ice until delivery the next day to the laboratory. All samples were analyzed by an Ecology- accredited laboratory using method number 8151A.
Sacheen Lake was visually surveyed using a boat-mounted viewing tube on August 28, 2003 by the applicator. The treatment efficacy was rated fair with about 70 percent of the milfoil removed. Some areas showed complete removal and other areas showed partial kill with dying plants remaining. No adverse impacts such as algae blooms or fish kills were observed. The applicator also reported that the milfoil in Moon Creek appeared to be gone. Secchi disk readings were 2.9 m on 6/22/03, 4.75 m on 7/20/03, and 4.0 m on 8/18/03(average of two mid-lake sites each).
All 2,4-D samples were below the EPA drinking water standard of 70 ppb by one day after treatment.
Treatment Site: Northeast end of lake (approximately 2 acres treated - samples 7 & 8)
|
Time |
Inside Treatment Area |
Outside Treatment Area |
|
1 Day after Treatment |
17.9 ppb |
16.7 ppb |
|
3 Days after Treatment |
17.1 ppb |
23.7 ppb |
Treatment Site: Northwest end of lake (approximately 3 acres treated – samples 5 & 6)
|
Time |
Inside Treatment Area |
Outside Treatment Area |
|
1 Day after Treatment |
34.1 ppb |
5.9 ppb |
|
3 Days after Treatment |
13.9 ppb |
9.1 ppb |
Treatment Site: Southwest end of lake (approximately 0.1acres treated – samples 3 & 4)
|
Time |
Inside Treatment Area |
Outside Treatment Area |
|
1 Day after Treatment |
44.8 ppb |
22.3 ppb |
|
3 Days after Treatment |
18.4 ppb |
16.5 ppb |
Treatment Site: Moon Creek (inside) Sacheen Lake (outside sample)
|
Time |
Inside Treatment Area |
Outside Treatment Area |
|
1 Day after Treatment |
18.2 ppb |
5.9 ppb |
|
3 Days after Treatment |
3.4 ppb |
13.0 ppb |
Click here to see the NPDES monitoring form for Sacheen Lake (PDF)
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