Moxee POTW

The Moxee POTW (Publically Owned Treatment Works) Site, also known as Moxee City Shop & Stormwater Treatment Plant (STP), is located at 7520 Postma Road, Moxee, at the intersection of Highway 24 and Postma Road in Moxee, Washington. The site is currently the identified as the Moxee City Shop, and was previously used as a sewage treatment plant. The sewage treatment plant is no longer operational as wastewaters are treated at the Yakima regional wastewater treatment facility.

In 1996, a release of petroleum products was discovered during the removal of underground storage tanks. The tank was used for fueling City vehicles. Petroleum contamination has been confirmed for both soil and groundwater. Nitrate contamination has also been confirmed in groundwater.

The site is currently on Ecology’s Hazardous Sites List with a ranking of “3”. Sites on the Hazardous Sites List are a priority for Ecology, and have completed a Site Hazard Assessment (SHA). A SHA provides information about the environmental risk of the site. Risk is based on the amount of contaminants, how toxic they are, and how easily they can come in contact with people and the environment. Sites are ranked relative to each other on a scale of “1” to “5”; with a rank of “5” being the lowest.

In May 1996, the City of Moxee removed two 1,000-gallon gasoline leaking underground storage tanks. About 50 cubic yards of petroleum contaminated soil was excavated, and a bioremediation treatment was used to break down petroleum into less harmful chemicals. 

In August 1996, additional soil was excavated and sampling was performed to verify all the contaminated soil had been removed. Four test pits were dug at this time to collect groundwater samples, and petroleum contamination was confirmed.

In March and October 2012, wells to monitor groundwater contamination were installed, and soil and groundwater samples were collected. Petroleum contamination and nitrates above state cleanup levels were found in groundwater at the site.  

In November and December 2013, additional wells to monitor groundwater were installed, and soil and groundwater samples were collected to help better determine where the petroleum contamination is located, how much is present, and aid in selecting and designing a cleanup remedy.

Reports with descriptions of the work and findings are linked below. You can review additional background and technical documents by using the Documents link below.

Cleanup activities occurred in December 2014 consisting of injecting chemical and biological treatment compounds into soil and groundwater to breakdown the petroleum into non-toxic products. Groundwater monitoring wells will continue to be sampled on a quarterly schedule. The timeline for reaching cleanup goals is expected to be 1 to 2 years.

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