Twin and Ryan Lakes Nutrient TMDL Five Year Review

This report is a review of progress toward meeting the load reductions identified in the Twin and Ryan Lakes Nutrient TMDL (Wenck 2007a). It includes an assessment of actions that have been implemented and the water quality trends that have been observed. Finally, this report describes the actions planned for the next 5 years of the implementation plan and sets forth how progress toward the TMDL will be measured. The three basins of Twin Lake –Upper, Middle, and Lower – and Ryan Lake was formally designated Impaired Waters for excess nutrients in 2002. A TMDL and Implementation Plan were approved in 2007. The TMDL determined that phosphorus load reductions of 58% (Upper), 13% (Middle), 12% (Lower) and 19% (Ryan) would be necessary to ensure the lakes met or exceeded state water quality standards for nutrients. Upper Twin requires a 40% reduction in load from internal sources, and a 64% reduction from the watershed. Because the other lakes are connected in series, the TMDL load reductions for the other lakes could be accomplished by improving the upstream lakes and thus reducing the load from upstream or by reducing watershed loads. The Implementation Plan (Wenck 2007b) identified priority actions and strategies for the first five years of implementation. Some of these were discrete actions or projects, and for the most part those have been completed or are in planning. Other actions such as implementing load reduction and infiltration strategies as opportunities arise are ongoing.