Tonasket School District 404

The Tonasket School District site operates as the Tonasket primary and secondary school campus. In May 1995, four underground storage tanks (USTs) were removed.

Results of analyses collected during UST removal indicated that three of the USTs had leaked. Additional excavation was performed in an attempt to remediate impacted soil at all three release sites. Excavation was stopped when it became apparent that the integrity of nearby building structures was threatened if excavation continued.  

Both impacted areas present a low threat to human health and the environment given the non-volatile nature of the contaminants, depth of the contaminants, and depth to groundwater in the vicinity. It was determined that both impacted areas would be managed in-place with the use of institutional controls. A restrictive covenant was recorded for the site.

Based upon cleanup activities and the recording of the restrictive covenant, Ecology has determined the site is no longer a threat to human health and the environment. A no further action determination was issued in 1999.

Periodic reviews are conducted every 5 years by Ecology for sites that have institutional controls. The review is intended to examine the effectiveness of cleanup activities and to assure the continued protection of human health and the environment.

Periodic review results

Based upon site visits, no repair, maintenance or contingency actions have been required. The Tonasket School District continues to occupy the site. Asphalt, building structures, landscaping and play fields continue to serve as a surface cover to prevent exposure by ingestion or direct contact to contaminated soils. Use of the site as a primary and secondary school facility is not likely to expose contaminated soils, and is a compatible land use as long as the surface cover is maintained.  

As a result of changes to Model Toxics Control Act (MTCA) Method A cleanup levels for TPH-D and TPH-O in 2001, several of the confirmation samples collected from the site are no longer above MTCA Method A cleanup levels.  
 
Soils with TPH-D and TPH-O concentrations higher than MTCA Method A cleanup levels are still present at the site. However, the surface covers and land use prevents human exposure to this contamination by ingestion and direct contact with soils. The restrictive covenant for the property will ensure that the integrity of the surface cover will be protected through maintaining the current use of the site and prevent activities that will expose contaminated soils.