Department of Ecology News Release - July 14, 2014

Examining Lake Spokane for excess nutrients
Results will help determine if source is on-site septic systems

SPOKANE – Scientists from the U.S. Geological Survey will collect groundwater and aquatic plant samples near the Suncrest community in Stevens County for a study on excess nutrients in Lake Spokane.

USGS will be on the lake July 18 in preparation for the study and begin sampling in August.

Too many nutrients like nitrogen and phosphorus in the Spokane River and Lake Spokane cause depletion of dissolved oxygen that fish and other aquatic life need to survive. Excess nutrients can also cause toxic algae blooms that are harmful to human health.

The USGS study, cooperatively funded by the Washington Department of Ecology, will help determine if on-site septic systems are a source of excess nutrients that enter the lake.

Ecology’s Spokane River dissolved oxygen water quality improvement plan, approved in 2010, requires reducing sources of nutrients such as phosphorus to improve the lake’s health.

Scientists will look at nitrogen content in groundwater and aquatic plants along the shoreline near existing homes then compare them to samples taken from areas without homes. Nitrogen from on-site septic systems has a unique chemical signature that can be detected in groundwater and plant tissue.

This study builds on a broader study conducted by Spokane County, which recommends further investigation of densely populated areas that rely on on-site septic systems for wastewater treatment.

The Suncrest community is the most densely populated cluster of on-site septic systems along the lake, with more than 1,300.

A report on the study findings is expected in December 2015.



Brook Beeler, Washington Department of Ecology, 509-329-3478, and @ecyspokane