Congressional District # 06
U.S. AVIEXEPA ID# MID980794556
Last Updated: March, 2015
The 6-acre U.S. Aviex Superfund site is located in Cass County, Michigan, just south of the city of Niles. The site is in a residential neighborhood that mostly consists of single family homes. The nearest home is within 100 feet of the facility. Minor agricultural and horticultural activities were performed in the general vicinity of the site.
The U.S. Aviex Company produced non-lubricating automotive fluids at the site from the early 1960s until late 1978. The products were blends of diethyl ether (DEE) and volatile organic chemicals (VOCs). Large quantities of these chemicals were stored on site in tanks and the chemicals were piped to the process area. During operations in the 1960s and 1970s, releases of solvents, such as benzene, trichloroethylene (TCE), tetrachloroethylene (PCE), and DEE, occurred. These compounds have contaminated the private residential wells near the site. In 1972, an underground pipeline containing DEE ruptured during excavation at the plant. In 1978, a large but unknown quantity of chemicals, including TCE, was also released during a fire at the plant. These releases impacted the drinking water aquifer in the area. Contaminants were detected in downgradient private residential wells southwest of the plant as far as one-half mile away.
The United States Environmental Protection Agency (EPA) placed the U.S. Aviex site on the National Priorities List on September 8, 1983.
Site ResponsibilityThe U.S. Aviex site is being addressed through a combination of potentially responsible party (PRP) and state and federal actions.
Threats and ContaminantsPrior to remedial activities being completed at the U.S. Aviex site, the groundwater and soil were contaminated with volatile organic compounds (VOCs). There are no current human health or environmental threats associated with contamination from the site.
In 1983, following Michigan Department of Natural Resources (MDNR) site investigations, U.S. Aviex installed a 200 gallon-per-minute groundwater extraction and treatment system to contain and treat on-site groundwater contamination. U.S. Aviex operated the system for about 10 years. In 1985, U.S. Aviex and EPA signed an Administrative Order on Consent (AOC) to have U.S. Aviex conduct a Remedial Investigation (RI) to determine the nature and extent of site contamination, and a Feasibility Study (FS) to evaluate potential site cleanup alternatives. The RI was completed in 1986. U.S. Aviex then declared bankruptcy and EPA completed the FS.
The RI delineated two areas in need of cleanup: (1) about 13,000 cubic yards of VOC-contaminated soils; and (2) the contaminated groundwater plume extending to Almagus Road, approximately one-third mile from the site.
In 1987 MDNR finished constructing a municipal water supply for about 220 homes affected by the contaminated groundwater plume. In 1988, EPA signed a Record of Decision (ROD) documenting the site cleanup plan. The remedy included:
* A five-well groundwater extraction system;
* Modifying and rehabilitating the existing air stripper to better remove VOCs from the groundwater;
* Monitoring to ensure effective treatment; and
* Conducting a soil flushing action on the soil area.
The groundwater extraction and treatment ("pump-and-treat") remedy was operated briefly by EPA. In 1993, MDNR assumed the long-term response action (LTRA) at the facility. In 1993, study results showed significant contaminant level reduction in the 13,000 cubic yards of soil. A 1993 Explanation of Significant Differences (ESD) was signed that documented the decision to eliminate the soil flushing treatment requirement. In 1993, contamination was found beyond the capture zone of the installed pump-and-treat system. An additional purge well was installed in 2000 to prevent further migration of contaminants, a requirement also documented in an ESD.
The pump-and-treat system effectively in reduced the VOC contaminants to very low concentrations. The 2003 quarterly monitoring data showed that only 1,2-dichloroethane (1,2-DCA) remained above its Safe Drinking Water Act maximum contaminant level (MCL) of 5 ppb. Additional studies conducted by the Michigan Department of Environmental Quality (MDEQ), formerly MDNR, indicated that no contamination was detected in the city of Niles well protection zones. The studies conducted by MDEQ identified two additional small areas of contamination on the U.S. Aviex property - a 100 square-foot "perched" water table located north of the warehouse contained benzene, TCE, 1,2-DCA, and other chemicals at concentrations above MCLs. In addition, an area was found south of the groundwater treatment system that contained PCE, TCE, trichloroethane (TCA), and 1,2-DCA.
MDEQ conducted a pilot study using a new injection treatment method, which decreased the contamination above the perched water table. The pilot study also suggested that in-situ air/ozone treatment would effectively reduce the contamination south of the groundwater treatment system. EPA decided to change the pump-and-treat remedy to monitored natural attenuation (MNA), augmented by the injection method for the area near the warehouse. In addition, EPA began in-situ ozone/air treatment of the area south of the groundwater treatment system. This decision resulted in a change to the 1988 selected remedy, and was documented in a 2004 ROD Amendment. The Amendment included the following six actions:
* Shut down the pump-and-treat system and rely on MNA to further reduce contaminant levels in the groundwater beyond the U.S. Aviex property line;
* Monitor the attenuation of the downgradient contaminants;
* Install and operate an in-situ ozone/oxygen treatment system to assist MNA;
* Update the groundwater clean-up standards to the current MCLs;
* Use the ozone air sparging treatment for the southern area to prevent further off-site migration of contaminated groundwater;
* Provide contingency plan(s) that may include the operation of the existing extraction system with a new air stripper system and/or the installation of a downgradient pump-and-treat system.
EPA conducted the second five-year review (FYR) at the U.S. Aviex site in December 2004. The review found that the remedy was functioning as intended by the ROD, ESD, and ROD Amendment. The pump-and-treat remedy reduced all contaminants of concern, except for 1,2-DCA, to very low concentrations. The review also indicated that 1,2-DCA was present in the groundwater plume primarily north of the capture zone at concentrations ranging from 6 to 35 ppb, slightly above its MCL of 5 ppb. This suggested that the chemical treatment of the perched water table north of the warehouse had eliminated the source of 1,2-DCA. All residual 1,2-DCA is expected to naturally attenuate to below 5 ppb over the next several years.
The 2004 FYR also found that the exposure assumptions, toxicity data, cleanup levels, and remedial action objectives used at the time of the remedy were still valid. MDEQ Part 201 Residential Health-Based Ground Water Criteria reflect concentrations in drinking water that are safe for both long-term and daily consumption. The remedy was determined to be protective of human health and the environment, but in order to be protective in the long term, an assessment of the MNA results must be continued.
In November 2009, EPA issued the third FYR report. The report stated that the remedy remains protective of human health and the environment over the short term and is functioning as intended by the ROD, ESD, and ROD Amendment. Excavation and treatment of the source area soil prevents further contamination of the groundwater. Groundwater contaminant concentrations had declined significantly over the last five years and do not pose a threat to the Niles municipal water supply.
Governmental institutional controls (ICs) are in place, such as municipal zoning ordinances to prevent the installation and/or use of private wells. In October 2011, the state of Michigan, as the site owner, placed a restrictive covenant and easement on the property prior to transferring the property for reuse. Among other things, the covenant prohibits groundwater use or well installation on site. The covenant also prohibits residential use of the property and excavation of the soil at certain depths.
In 2012, MDEQ revised the groundwater monitoring plan by increasing the monitoring frequency from annual to semi-annual and including additional parameters in order to evaluate contaminant biodegradation and Monitored Natural Attenuation (MNA) as a viable long-term remedy. In October 2014, MDEQ collected soil gas samples to characterize the soil gas contamination at the property and to evaluate vapor intrusion (VI) risks at the Site. Information to date suggests it is unlikely that VI is affecting downgradient residences. The report is expected to be completed in late 2015.
In November 2014, EPA completed the fourth FYR for the site. EPA found the remedy to be protective of human health and the environment in the short-term. All residents who were potentially at risk have been connected to the municipal water supply and no exposure to groundwater contamination is occurring. Effective and enforceable ICs that prohibit certain uses and activities at the Site (e.g., groundwater use), have been implemented on the Site property. Some actions need to be taken at off-site areas in order for the remedy to be protective in the long-term. These include: verifying the proper recording of activity and use restrictions on two off-site land parcels to prohibit the potable use of groundwater; increasing the scope of groundwater monitoring and evaluation activities to determine the appropriate measures to stabilize the plume and/or intercept it; and, developing and documenting long-term stewardship procedures.
The MDEQ will maintain the site and conduct annual groundwater monitoring until the cleanup criteria (MCLs) are met.
The U.S. Aviex property was purchased from the state of Michigan in fall 2012 by AVX Properties, LLC. The new owner worked with Howard Township to rezone the property from low-density residential to light industrial use. AVX Properties plans to use the site for an RV and boat storage facility.
In January 2013, EPA issued a Site-wide Ready for Anticipated Reuse (SWRAU) determination for the U.S. Aviex site. The SWRAU confirms that all cleanup goals in the ROD and other decision documents have been achieved for any media that may affect current and reasonably anticipated future land uses so there are no unacceptable risks. The SWRAU also documents that all ICs or other controls required by the remedy and all decision documents have been implemented.
ContactsRemedial Project Manager, U.S. EPA
sheila sullivan (email@example.com)
Community Involvement Coordinator, U.S. EPA