Water Quality Improvement Project
Selah Ditch Area:


Selah Ditch is east of the Cascade Mountains in Yakima County, Washington State. It is about one mile north of the city of Yakima. Climate in the area is generally mild and dry. Most precipitation comes during the late fall to early spring months.

Selah Ditch is a man-made drainage canal, originally made for dewatering a high water table to allow the city of Selah to continue to grow. It collects water from point and nonpoint sources: mainly irrigation supply water, irrigation runoff, urban storm water, and industrial/municipal discharges. It then discharges into the west side of the east fork of Taylor Ditch.

Water quality issues

Based on studies and water samples, Selah Ditch was placed on Washington State's 1996 and 1998 303(d) lists due to violations of the state water quality standards for ammonia, chlorine, and dissolved oxygen. On the 2004 list the ditch was listed only for fecal coliform bacteria and temperature. Studies found some impaired levels of dissolved oxygen, but due to insufficient data it was not listed for dissolved oxygen.

Selah Ditch - looking downstream to the southwest from Upper Reach, Washington State.  Photo from 'Selah Ditch Multiparameter Total Maximum Daily Load: Technical Assessment', Ecology publication number 05-10-020.

Why this matters

Fecal coliform is a type of “bacteria” common in human and animal waste. It can make people sick and cause the closure of shellfish harvesting beds. Bacteria can get into our 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 waterbody. Cooler water can hold more dissolved oxygen that fish and other aquatic life need to breathe. Warmer water holds less dissolved oxygen. Threatened and endangered salmon need cold, clean water to survive.

Status of the project

The Department of Ecology, with the help of local groups in the watershed, developed a total maximum daily load (TMDL) report. The report provided results of water quality studies on the ditch, recommendations for bringing the water quality up to meet state standards for fecal coliform bacteria and temperature, and an implementation strategy on how to accomplish the recommendations. Ecology sent the finalized TMDL to EPA for approval. EPA approved the document in September 2006.

Wasteload allocations were applied to the publicly-owned treatment works (POTWs) and stormwater discharges through their National Pollutant Discharge Elimination System (NPDES) permits and best management practices (BMPs). For temperature issues, mainly due to solar radiation, the recommendation was application of load allocations in the form of increased shading over parts of the ditch.

Past chlorine problems have been eliminated due to the city of Selah's POTW converting to ultraviolet (UV) disinfection. Past ammonia problems have not continued, so there is insufficient data to warrant a continued listing.

Technical information

Selah Ditch Multiparameter Total Maximum Daily Load: Technical Assessment (Ecology publication)

Selah Ditch Multiparameter Total Maximum Daily Load: Water Quality Improvement Report (Ecology publication)

Related information

Little Klickitat River Watershed Temperature Total Maximum Daily Load (Ecology publication)

Teanaway Temperature Total Maximum Daily Load – Submittal Report (Ecology publication)

WRIA 39: Upper Yakima Watershed Information (Water web site)


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Last updated May 2009
  Water resource inventory area (WRIA) 39 map, Washington State.


#39 (Upper Yakima)

Water-body Name:
Selah Ditch

Fecal coliform

# of TMDLs: 3

TMDL approved by EPA

Contact Info:
Greg Bohn
Phone: 509-454-4174
Email: Greg.Bohn@ecy.wa.gov

Central Region
Department of Ecology
1250 West Alder Street
Union Gap, WA 98903-0009