Clover Creek multi-parameter project
The Clover Creek watershed is in Pierce County. The creek flows through Tacoma's urban growth areas, Lakewood, Joint Base Lewis-McChord (JBLM), and empties into Lake Steilacoom.
Tests show that its water quality is impaired by low levels of dissolved oxygen, warm water temperatures, and bacteria. We're working with local governments and other interested parties to address these pollution problems.
Water quality issues
Portions of Clover Creek and its tributaries do not meet the state criteria for dissolved oxygen (DO), fecal coliform, and temperature. From 1991 to 1992, U.S. Geologic Survey data showed that three out of five DO samples fell below criteria on Morey Creek, and three samples with temperatures beyond the temperature criteria on Clover Creek at Gravelly Lake Drive. From 1993 to 2001, our data showed four additional high temperature readings. We've also recorded multiple instances of high fecal coliform throughout the watershed. Our 2016 source assessment data collection effort confirmed these water quality problems.
What we have done
Through March 2014, we collected water quality data as part of a source assessment effort. We found that the water in most areas of Clover Creek was very degraded.
- Concentrations of fecal coliform exceeded state standards at 13 of 22 study sites. In addition, fecal coliform concentrations in stormwater samples exceeded standards at 15 stream sites and one stormwater outfall.
- Dissolved oxygen concentrations did not meet the minimum daily DO criteria at four of the six sites monitored during the summer (May through September), and all but one study site exceeded temperature criteria.
- A study of benthic macroinvertebrates showed the biological condition to be poor at two sites and very poor at four sites.
Status of the project
Given the small size of the watershed, the nature of the pollution sources, and our limited resources, we decided to use an alternative to the total maximum daily load (TMDL) approach. We're working to improve water quality directly by implementing fixes to address the pollution sources identified in the Clover Creek water quality assessment.
This effort is similar to a straight to implementation (STI) process because we are focusing on implementation rather than planning, but it is different because we are not the project lead. Pierce County has jurisdiction over much of the watershed and has elected to serve as the lead for implementation efforts.
We're working closely with Pierce County, other local governments, and stakeholders to identify priority river reaches and pollution sources, and develop an implementation strategy to address these problem areas. Pierce County will conduct long-term water quality monitoring to assist with adaptive management efforts and track overall progress.
If water quality fails to improve we may decide to use the TMDL process at a later date.
Why it matters
Oxygen dissolved in healthy water is vital for fish and aquatic life to survive. It is more difficult for aquatic animals to transfer oxygen from water to blood than it is for air-breathing animals to transfer oxygen from air to blood. Therefore, it is critical that there is an adequate amount of oxygen in the water to sustain aquatic life. Oxygen is also necessary to help decompose organic matter in the water and bottom sediments, along with other biological and chemical processes.
Fecal coliform is a type of bacteria common in human and animal waste. It indicates that sewage or manure is entering a water body. As the level of fecal coliform increases, the risk of people getting sick from playing or working in the water increases. Bacteria can get into waters from untreated or partially treated discharges from wastewater treatment plants, from improperly functioning septic systems, and from livestock, pets, and wildlife.
Water temperature influences what types of organisms can live in a water body. Cooler water can hold more dissolved oxygen that fish and other aquatic life need to breathe. Warmer water holds less dissolved oxygen. Many fish need cold, clean water to survive.