Publication Summary

Washington State Department of Ecology is required to develop and implement Total Maximum Daily Loads (TMDLs) for impaired waters, and evaluate the effectiveness of the clean-up plan. This report presents an assessment of the effectiveness of total phosphorus (total P) TMDL implementation programs at Fenwick and Sawyer lakes.

Available monitoring data indicate that both lakes have periods when total P concentrations are above their target limits, especially at Lake Fenwick. Consequently, both lakes may likely continue to experience elevated total P concentrations and subsequent eutrophication. The fundamental supposition is noncompliance to the state′s narrative water quality standard for aesthetics.

The Washington State Department of Ecology is required, under Section 303(d) of the federal Clean Water Act and the U.S. Environmental Protection Agency′s implementing regulations, to develop and implement Total Maximum Daily Loads (TMDLs) for impaired waters and to evaluate the effectiveness of the clean-up plan to achieve the needed improvement in water quality. Total phosphorus (total P) TMDLs were developed for both Fenwick and Sawyer lakes, based on the narrative state water quality standard for aesthetics.

Maximum in-lake mean summer total P concentration limits of 19 and 16 µg/L were set for Fenwick and Sawyer lakes, respectively, in their TMDLs to deter progression of eutrophication. Preliminary evaluation of available monitoring data indicates non-compliance to the maximum in-lake mean summer target limits set for total P in the TMDLs at both lakes in a short term. Consequently, violation of the narrative state water quality standard for aesthetics and further eutrophication may exist, based on initial individual year survey of the TMDL data. However, Lake Sawyer seems to be meeting the TMDL target limit as a long-term average.