Middle Yakima River Basin Bacteria TMDL

Enfoque: La Carga Diaria Máxima Total (TMDL, por sus siglas en inglés) de Bacteria en la Cuenca del Rio Medio-Yakima

En Español: Para información en español, por favor comuníquese con Cole Provence al (509) 379-3557.

Wide Hollow Creek, Cowiche Creek, and Moxee Drain are three tributaries to the Yakima River near the city of Yakima. These tributaries are on the Washington state list of impaired water bodies, known as the 303(d) list, due to excessive fecal bacteria. We are developing a water quality improvement project in the area to control harmful bacteria sources and bring these tributaries back into compliance with state water quality standards.

Water quality issues

In many areas of the Mid-Yakima River Basin, fecal coliform bacteria and E. coli numbers are much greater that the maximum allowed under state water quality standards, and those numbers are significantly higher between April and October than during the rest of the year.

There are multiple potential sources of bacterial contamination in the middle Yakima River basin, such as:

  • Wildlife feeding and habitat areas.
  • Livestock on commercial and non-commercial farms.
  • Rural, residential, commercial, industrial, and urban stormwater runoff.
  • On-site septic systems and illicit sanitary connections.

Our draft plan

We have drafted the Mid-Yakima River Basin Bacteria Total Maximum Daily Load (TMDL) water quality improvement plan. This draft water quality improvement plan aims to address high bacteria levels in three sub-basins: Cowiche Creek, Moxee Drain, and Wide Hollow Creek. We held a public comment period from Oct. 13, 2020, through Nov. 13, 2020. Currently, we are considering comments and will revise the document if needed. The comments and our response to comments will be included as an Appendix to the plan. Once finalized and implemented, this plan should lead to more functional habitat for coho salmon, bull trout, and other species and ensure safe swimming, fishing, and boating.

You can view comments online in eComments.

Supporting Documents 

What we have done

We conducted several field surveys in the Cowiche Creek, Moxee Drain, and Wide Hollow Creek sub-basins from December 2004 through March 2006; from June through December 2010; and from March through June 2014. We used the data collected during these surveys to develop reach-specific bacteria loading capacities for each tributary, and estimated load reductions necessary to meet these capacities.

We started developing the Mid-Yakima River Basin Bacteria TMDL plan in 2015. We held a public meeting on  on July 28, 2015 to start the process. We held several Technical Advisory Work Group meetings throughout 2016. The project was prolonged due multiple staffing changes and the validation of data collected over such a wide time period. We have opened a comment period for this report. Once the comment period is closed and we review comments, we will prepare the final report with the response to comments in an appendix and submit to the Environmental Protection Agency (EPA) for approval later in 2020.

Why this matters

High levels of bacteria pollution in streams and lakes are a risk for disease to humans and animals that are exposed to contaminated water. Washington state is required to protect the “most sensitive” beneficial uses found in water bodies, which include the ability to wade, swim, and fish in the state’s lakes, rivers and streams.  This water improvement project will specifically reduce bacteria pollution within the Cowiche Creek, Moxee Drain, and Wide Hollow Creek sub-basins.

What actions can help reduce fecal coliform bacteria and E. coli?

Ecology staff work with a wide range of partners who help conduct studies, serve on the advisory committee, participate in planning, and conduct or oversee cleanup activities. Also, we look forward to continuing to work with all residents of the project area. Some key actions that groups and individuals can take to help reduce bacteria include:

  • Improve stormwater management practices
  • Protect existing streamside (riparian) buffers, and plant new ones where possible; these buffers help filter out contamination
  • Identify and renovate failing septic systems
  • Modify livestock management practices to reduce animal contact with surface water
  • Improve irrigation practices to reduce the transport of bacteria into surface water
  • Pick up pet waste, don't let rain wash it into our rivers and streams