Congressional District # 08
RITARI POST & POLEEPA ID# MND980904064
Last Updated: March, 2015
Site DescriptionThe 212-acre Ritari Post & Pole site is located approximately 3.5 miles northeast of the small town of Sebeka in a rural area of Wadena County, Minnesota, The site was the location of a wood-preserving facility that operated from 1959 to 1991. The wood-preserving operation used creosote as a preservative until 1966, and following that, used pentachlorophenol (PCP) as a preservative. From 1966 to 1973, the site used a process that allowed approximately 72,000 gallons of PCP to drip from treated wood directly onto the ground. In addition, approximately 3,200 gallons of PCP-contaminated sludge were discharged directly to the ground. The site is located three-quarters of a mile from a wetland area which drains to the Cat River.
Site ResponsibilityThe Minnesota Pollution Control Agency (MPCA) is the lead agency which managed cleanup of the site and continues to oversee the site in coordination with EPA.
Threats and ContaminantsSoils at the site were contaminated with PCP, dioxins and furans. Groundwater at the site was contaminated with PCP and various petroleum compounds which were used as carriers for PCP in the wood treating process.
This site was addressed as a state-lead cleanup. MPCA completed an investigation of contamination at the Site and, in 1994, MPCA and EPA selected a remedy for contaminated soil and groundwater. The soil remedy included excavation of contaminated soils that exceeded 40 parts per million (ppm) PCP or 1 part per billion (ppb) dioxin (tetrachlorobenzodioxin or "TCDD-equivalent"). For PCP-contaminated soils, the remedy required on-site bioremediation in a lined treatment cell. For dioxin-contaminated soil, the remedy required investigation of soil washing as a treatment technology and off-site incineration of remaining dioxin-contaminated soil. The soil remedy for both types of contaminated soil also included a contingency to require consolidation and containment beneath an on-site RCRA-compliant cap if treatment studies or actual treatment for three years indicated that soil cleanup standards would not be met.
In 1999, MPCA and EPA modified the soil remedy in an Explanation of Significant Difference (ESD) to remove soil treatment and incineration from the remedy and invoke the contingency for on-site containment covered by a RCRA-compliant cap. In 2008, the State and EPA modified the remedy for dioxin-contaminated soil to require excavation and off-site disposal. Therefore, the final soil remedy included an on-site disposal unit with a RCRA cap and excavation and off-site disposal of additional soils.
The 1994 groundwater remedy included installing an on-site water supply well and groundwater monitoring. The groundwater remedy also included a contingency to require extraction and treatment if groundwater contaminants exceeded certain levels at the eastern boundary of the site. In a 1999 ESD, the State and EPA determined that it would not be necessary to invoke the contingent remedy for groundwater and that groundwater monitoring would be sufficient. Beyond the property line, the monitoring wells and a private well showed no detection of contamination.
In 1997, EPA and MPCA removed 38 deteriorating drums containing spent PCP solution. This allowed MPCA to decontaminate and move or dismantle certain onsite buildings in preparation for further cleanup. Installation of onsite and offsite monitoring wells and a deeper domestic well for the onsite household were also completed in 1997. Contaminated soils were placed in an onsite, unlined capped cell, for which construction was completed in 2001. A Preliminary Close Out Report (PCOR) was completed in 2001. Maintenance of the onsite capped unit and groundwater monitoring are being performed by MPCA and its contractors.
Five year reviews are conducted at the site. The last review occurred in 2013 and concluded that the remedy was protective of human health and the environment in the short-term because the consolidation cap is being properly maintained and groundwater is being monitored. The review also showed that exposure to remaining contaminants in soil are unlikely to present a risk as long as the property is used for occasional recreation, such as hunting. However, the review recommended that MPCA develop a revised cleanup plan for soil and define the groundwater plume better in one area. Currently, MPCA is in the process of evaluating additional actions for the site.
ContactsRemedial Project Manager, U.S. EPA
leah evison (firstname.lastname@example.org)
Community Involvement Coordinator, U.S. EPA