The Puget Sound region is a unique network of mountain peaks, plateaus, rivers, lakes, and marine waters. These natural wonders make Pierce County a beautiful place. Maintaining healthy water quality in the streams, rivers and lakes that connect the Cascade Mountains to Puget Sound is essential to the quality of life and prosperity of Pierce County residents, businesses and wildlife.
Water quality has declined in most areas of Pierce County as the population and development have grown over the past century. The most common water quality concerns in Pierce County streams are high levels of bacteria, nitrogen and phosphorus, elevated summer temperature and low dissolved oxygen concentrations.
The Benthic Index of Biotic Integrity (BIBI) score is calculated using benthic macroinvertebrate (bugs living on the bottom of streams) samples collected at least once every five years.
The Water Quality Index (WQI) score is calculated using monthly stream water quality sampling for bacteria, pH, dissolved oxygen, temperature, turbidity, total suspended solids, total nitrogen and total phosphorus.
Watershed health is classified into three categories—low, marginal and high—using BIBI and Water Quality Index scores.
Pierce County Planning and Public Works monitor water quality monthly at 53 Pierce County streams. Benthic samples from a subset of streams are collected every summer. The Pierce Conservation District and Tacoma-Pierce County Health Department sample water quality in lakes each summer.
Surface Water Management (SWM) collects water level and weather data for a number of projects. Local live weather station data can be found here.
The monitoring section helps ensure Pierce County meets the requirements of the National Pollutant Discharge Elimination System (NPDES) Phase I Municipal Stormwater Permit. SWM collects local data to measure whether water quality is getting better or worse and identify patterns in healthy and impaired Puget Lowland streams and Puget Sound urban shoreline areas. SWM also collects data for NPDES driven modeling and Total Maximum Daily Load (TMDL).
Pierce County conducts shellfish beach sampling and coordinates with the Tacoma-Pierce County Health Department and other partners on programs to keep pollutants out of shellfish beds.