LA CROSSE COUNTY
Congressional District # 03
ONALASKA MUNICIPAL LANDFILLEPA ID# WID980821656
Last Updated: December, 2014
The Onalaska Municipal Landfill site consists of a 7-acre landfill situated on an 11-acre parcel of property adjacent to the Black River in the Town of Onalaska (population 4,000). The surrounding area is rural and consists primarily of agricultural lands, although several homes are located nearby. The landfill area was formerly a sand and gravel quarry before it was used as a municipal landfill. From 1969 to 1980, the Township of Onalaska operated the landfill, where municipal refuse was commingled with industrial solvents such as naphtha, toluene, and trichloroethene.
The U.S. Environmental Protection Agency (EPA) proposed the site to the National Priorities List (NPL) in September 1983 and finalized the site on the NPL in September 1984.
Site ResponsibilityThis site is being addressed through federal and state actions.
Threats and ContaminantsThe solvents from the landfill contaminated the groundwater beneath the site as well as an adjacent homeowner's drinking water well that the Town of Onalaska replaced in the early 1980s. A floating layer of hydrocarbons, which acts as a source of groundwater contamination, was found to be emanating from the landfill.
Cleanup ProgressEPA, in consultation with the State, began a remedial investigation and feasibility study (RI/FS) at the site in 1988. The RI/FS was completed in 1990, when EPA issued a cleanup decision. The decision document, known as a Record of Decision (ROD), called for construction of a landfill cover (cap), a groundwater extraction and treatment system, and a bioremediation system to address the risks posed by the contamination at the site.
EPA, in concert with the State, began constructing the selected remedy in 1993. The construction work was completed in July 1994 and was documented in a preliminary close-out report (PCOR). Operation of the groundwater extraction and treatment and the bioremediation systems commenced at that time. It was estimated that the bioremediation system would operate for about five years and that the groundwater extraction and treatment system would operate for a minimum of 10 years. After 10 years of operation, the control of the site would be turned over to the state.
The groundwater extraction and treatment system pumped out 1.8 billion gallons of water for treatment via air stripping, significantly reducing the levels of contaminants in the groundwater plume. Metals are the only contaminants that remain above the cleanup standards. The bioremediation system, which simply supplied oxygen (air) to the subsurface soil where the hydrocarbon layer was located, reduced the concentrations of the hydrocarbons in the soils. The bioremediation system was discontinued in 1998 after soil gas data showed that the system was no longer contributing to the cleanup.
On November 13, 2001, EPA signed an explanation of significant differences (ESD) for the site. The ESD allowed for the temporary shutdown of the groundwater treatment system to study natural attenuation as an alternative to clean up the remaining groundwater contamination. The groundwater treatment system was shut down on November 26, 2001. The Wisconsin Department of Natural Resources (WDNR) took over the operation and maintenance of the site in June 2002 and also continued the natural attenuation studies at the site.
On September 24, 2012, EPA and WDNR issued a ROD Amendment to amend the 1990 ROD. The ROD Amendment called for the permanent shutdown of the pump and treat system, changed the cleanup standards to State enforcement standards and federal drinking water standards, and called for the replacement of two private drinking water wells.
The first five-year review for the site was completed in 1998, and the second, third, and fourth five-year reviews were completed in 2003, 2008, and 2013, respectively. The April 2013 five-year review identifed only a few issues that needed to be resolved, including the replacement of the two private drinking water wells (as called for in the 2012 ROD Amendment) and the need to further evaluate the metals contamination in groundwater. EPA completed the replacement of the two private drinking water wells in June 2013. EPA and the State are collecting additional groundwater data at the site to further evaluate metals. This data will be used to determine if metals in the groundwater are causing any risk to human health and the environment.
ContactsRemedial Project Manager, U.S. EPA
demaree collier (firstname.lastname@example.org)
Community Involvement Coordinator, U.S. EPA
AliasesONALASKA MUNI LDFL