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Middle Yakima River basin fecal coliform TMDL

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 coliform bacteria. We are developing a water quality improvement project in the area to control fecal coliform sources and bring these tributaries back into compliance with state water quality standards.

Water quality issues

Rapid population increase in the area led to conversions of farm, orchard, and range land into other land uses. This unique checkerboard of land uses includes industrial, urban, transportation, residential, orchard, irrigated agriculture, non-commercial farm, forest, and range.

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.

Water is needed for agriculture, but the waterways are also used for broader and sometimes conflicting uses like stormwater conveyance, fish habitat, and recreational opportunities.

What we have done

We conducted 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 fecal coliform loading capacities for each tributary, and estimated load reductions necessary to meet these capacities.

We developed a draft Mid-Yakima River Basin Bacteria TMDL report for this project. A public meeting on the project was held on July 28, 2015, followed by a public review and comment on the TMDL report from July 28 - September 21, 2015. Several Technical Advisory Work Group meetings were held throughout 2016.

Status of the project

The final version of the report is being prepared and will be submitted to the Environmental Protection Agency (EPA) for approval later in 2017.

Why this matters

Fecal coliform bacteria (FCB) 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 bacteria increases, the risk of people getting sick from playing or working in the water increases. Fecal coliform 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. Surface and subsurface runoff from manure-applied croplands can be a significant contributor in agricultural areas.

People can help keep bacteria out of the water. Properly collect, bag, and trash dog poop. Check your onsite sewage system to make sure it is maintained and working properly. Ensure livestock and manure are kept away from surface water, and that surface and subsurface runoff in agricultural areas is minimized.

Municipalities can help keep bacteria out of the water. Illicit connections of sanitary sewage to stormwater sewer systems must be eliminated. Ordinances should be enacted and enforced that control animal manure disposal.