CENEX Supply & Marketing Inc Rinsate

The CENEX Supply & Marketing, Inc. (CENEX), Rinsate site stored and distributed liquid fertilizer and soil fumigant at 300 Division Street in Quincy. The fertilizer and fumigant plant was built in 1974 and operated until 1991. Operational features included an equipment rinse pad, a rinsate storage pond to capture contaminated liquids from rinsing equipment, and fumigant storage tank areas.

The site is in a commercial/industrial area next to a major rail corridor. Quincy High School is about 500 feet southwest of the site. A mobile home trailer park and other residences are about 1,000 feet south and southeast of the site.

Water for area businesses, schools and residents is provided by the City of Quincy public water supply system.

The liquid fumigants stored at the plant contained volatile organic compounds (VOCs), the primary contaminants found in soil and groundwater at the site.

During the early 1980s, fumigant releases were reported. Site investigations found areas where soil and groundwater contamination exceeded state standards and posed a risk to humans and the environment.

CENEX conducted several cleanup actions in the early 1990s. Between August 1994 and February 1995, all former fumigant storage tanks were decontaminated and removed. In 1997, soil from the rinsate pond was removed, and the area was covered with a thin layer of gravel. Monitoring wells were installed on the plant property and in offsite areas to evaluate groundwater contamination. Monitoring results confirmed a contaminated groundwater plume about 0.5 miles long. The plume runs to the southeast and passes beneath a portion of the Quincy High School property. Studies conducted in the late 1990s and early 2000s found no vapor concerns to the school from the plume.

Periodic reviews 

In October 2022, we completed the second periodic review. As a result of a comment we received from CENEX during the public comment period, we revised the periodic review to remove the recommendation to amend the Cleanup Action Plan to include the adjustments to site cleanup levels based on revised practical quantitation limits. Contaminant concentrations in groundwater will still be reported down to the revised practical quantitation limits during routine sampling. This change is documented in our response to comments.

The revised recommended actions to be completed during the next five years are as follows:

• Continue monitoring groundwater at the site
• Sample the domestic water supply well southeast of the West Canal
• Continue optimizing the multisparge and soil vapor extraction systems, which treat contaminants in groundwater and soil gas
• Complete an evaluation of the remediation performance before the next periodic review

Ecology conducted the first periodic review in September 2008 and made the following recommendations: