Lake Whatcom multi-parameter TMDL

Water quality issues

Lake Whatcom serves as the drinking water source for about 96,000 people in the Bellingham area. The lake is popular for recreation, and the area around it has become a popular place to live.

The primary water quality concern is low levels of dissolved oxygen (DO) as a result of increased levels of phosphorous and fecal coliform bacteria. A lack of oxygen threatens the survival of fish and aquatic plants.

Stormwater is the chief source for phosphorous and bacteria. Roofs, roads, driveways, and lawns speed the flow of stormwater to the lake without the benefit of filtering out the phosphorous and bacteria. In undeveloped areas, stormwater can slowly seep into the ground where it is filtered naturally before it reaches the lake. Computer predictions show the lake would meet state standards for dissolved oxygen if there was 86 percent less development than existed in 2003. Since then, zoning laws have allowed more development in the watershed.

These concerns triggered a water quality improvement project, the Lake Whatcom TMDL. The goal is to determine how much pollution the lake can process and still achieve acceptable levels of oxygen.

What's been done

EPA approved the Lake Whatcom TMDL in 2016. The City of Bellingham and Whatcom County have a budget and timeline to implement the TMDL in 50 years, and a written enforcement process that allows residents to confirm how codes are being enforced.

Status of the project

The City of Bellingham and Whatcom County developed and are taking action on the Lake Whatcom watershed total phosphorus and bacteria TMDL implementation plan approved in 2017. This plan outlines milestones for the years 2018 – 2029 that demonstrate the city and county are on track to meet the proposed timeline and budget requirements for full implementation of the TMDL. 

Actions include:

• Updating milestones and stormwater permits every five years.
• Educating the public about the proper handling and disposal of pet waste to reduce exposure to stormwater.
• Highlighting and forecasting phosphorus reduction programs and projects that might take place, but have not gone through the budget planning process.
• Updating the 2019 – 2025 Western Washington Phase II Municipal Stormwater Permit.

Next steps

• The CE-QUAL W2 lake response model update is underway and anticipated to be complete by early 2023.
• The city and county are working to submit updated 2024 – 2029 milestones that will include the following five years of forecasted phosphorus reduction programs and projects. 

Why this matters

Dissolved oxygen levels in Lake Whatcom fail to meet state water quality standards now and have the potential to get much worse. This makes the problem harder to fix. Impacted water requires more treatment to make the drinking water safe and this process creates more trihalomethanes, a byproduct that some studies link to cancer.

Phosphorus is the main cause of Lake Whatcom’s low-oxygen problem. Phosphorus occurs naturally. It is found in soil and human and animal waste, and is added to some detergents. Sources of phosphorus include runoff from bare soil and developed areas. Development increases the amount of phosphorus entering the lake in stormwater.

Phosphorus feeds algae growth, and excess phosphorus creates larger algae blooms. Bacteria that consume dying algae deplete the oxygen that fish and other aquatic life need to survive. When oxygen levels are low, phosphorus is released from lake sediment and re-enters the water, perpetuating the cycle.

Fecal coliform bacteria originates in human and animal waste. Runoff carries the bacteria from the ground and from failing septic systems to ditches and creeks, which deposit it into the lake. Eleven tributaries feeding Lake Whatcom fail to meet state standards for fecal coliform bacteria. The bacteria create a health risk for people who work or play in and around the water.

Roofs, driveways, and lawns interrupt the absorption and filtration provided by forests and soils, instead sending phosphorus-laden stormwater rushing to the lake. Communities must modify existing and future development to create the same effect as removing development. The filtration of stormwater through soil or sand filters helps address phosphorus and fecal coliform.