Lake Whatcom stormwater management activities focus on reducing phosphorus levels in Lake Whatcom in response to federal Clean Water Act requirements and the state Total Maximum Daily Load (TMDL) process. Phosphorus promotes algae growth. When algae die, the decomposition process depletes oxygen in the lake. In 1998, Lake Whatcom was placed on the state’s list of polluted water bodies because it did not meet water quality standards for dissolved oxygen. The Washington State Department of Ecology (Ecology) pointed to excess phosphorus as the primary cause of declining oxygen levels. 

Based on this listing, the Ecology began working on a mandatory water quality improvement plan, called the Lake Whatcom TMDL. This plan was finalized and approved by the Environmental Protection Agency (EPA) in 2016. The plan sets the phosphorus reduction target needed for the lake to meet federal and state water quality standards. To learn more about the State Department of Ecology’s 18-year process to study the lake and develop the TMDL, visit the following Ecology website pages:

• Lake Whatcom multi-parameter TMDL overview
• Lake Whatcom Watershed Total Phosphorus and Bacteria TMDL: Vol. 1. Water Quality Study Findings
• Lake Whatcom Watershed Total Phosphorus and Bacteria TMDL: Vol. 2. Water Quality Improvement Report and Implementation Strategy