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CASS COUNTY
HOWARD TOWNSHIP
Congressional District # 06
U.S. AVIEX
EPA ID# MID980794556Last Updated: September, 2008
Site Description
The U.S. Aviex site is a six-acre facility, located in the city of Niles, Cass County, Michigan, in a residential neighborhood that primarily includes 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.
Historically, the U.S. Aviex Company produced non-lubricating automotive fluids from the early 1960s until late 1978. During operations in the 1960s and 1970s, there were releases of chlorinated hydrocarbons and diethyl ether to the ground water which contaminated private residential wells near the site. A large but unknown amount of chemicals, including trichloroethylene, was also released during a 1978 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 U.S. Aviex facility was added to the National Priorities List on September 8, 1983.
Site Responsibility
This site is a fund-financed, state lead Superfund Site.Threats and Contaminants
The groundwater and soil are contaminated with volatile organic compounds (VOCs). Direct contact with or ingestion of the contaminated groundwater and soil pose potential health risks. Inhalation of contaminated vapors from the ground water or soil could also potentially cause adverse health effects.Cleanup Progress
U.S. Aviex produced automotive products from the early 1960's to 1978 on a six-acre site in Cass County, just south of Niles, Michigan. The products were blends of diethyl ether (DEE) and volatile organic chemicals (VOCs). Large quantities of these chemicals were stored onsite in tanks and the chemicals were piped to the process area. U.S. Aviex became a Superfund Site as a result of two major incidents: (1) a DEE pipeline rupture and (2) a major fire in 1978.
In 1983, Michigan Department of Natural Resources (MDNR) investigations resulted in U.S. Aviex installing a 200 gallon-per-minute groundwater extraction and treatment system to treat the on-site groundwater contamination. U.S. Aviex operated the system for about 10 years. In 1985 a Consent Decree (CD) was signed between U.S. Aviex and U.S. EPA (EPA) to conduct a Remedial Investigation (RI) to determine the nature and extent of site contamination, and a Feasibility Study (FS) to examine site cleanup alternatives. The RI was completed in 1986. After U.S. Aviex subsequently declared bankruptcy, EPA completed the FS.
The RI delineated two areas in need of cleanup: (1) about 13, 000 cubic yards of VOCs contaminated soils; and (2) the contaminated groundwater plume extending to Almagus Road, approximately one-third mile from the facility.
In 1987 MDNR finished constructing a municipal water supply for about 220 homes affected by the contaminated groundwater plume. In 1988 a Record of Decision (ROD) documenting EPA's cleanup plan was signed. The remedy included:
* A five-well extraction system;
* Modifying and rehabilitating the existing air stripper to remove the VOCs;
* Monitoring to ensure effective treatment; and
* Soil flushing by extraction and treatment.
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 reduction in the 13,000 cubic yards of soil. A 1993 Explanation of Significant Differences (ESD) was signed, documenting the decision to eliminate the soil flushing treatment. In 1993, contamination was found beyond the capture zone of the installed extraction and treatment system. An additional purge well was installed in 2000 to prevent further migration of contaminants, also documented in an ESD.
The pump-and-treat system was effective in reducing the VOC contaminant concentrations to very low levels. The 2003 quarterly monitoring data indicated that only 1, 2-dichorloethane (1,2-DCA) remained present above its maximum contaminant level (MCL) of 5 ppb for drinking water. An MCL is the highest level of a contaminant permitted in a public water supply. Additional studies conducted by Michigan Department of Environmental Quality (MDEQ) indicated that no contamination was detected in the city of Niles well protection zones. However, 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, trichloroethylene (TCE), 1,2-DCA, and other chemicals at concentrations above the MCLs. Also discovered was an area south of the groundwater treatment system that contained tetrachloroethane (PCE), TCE, trichloroethane (TCA), and 1,2-DCA.
MDEQ conducted a pilot study using a proprietary treatment method, which decreased the contamination above the perched water table. The laboratory pilot test suggested that an air/ozone in-situ treatment would effectively reduce the contamination to the south. EPA decided to change the pump-and-treat remedy to monitored natural attenuation (MNA), augmented with BIOX® treatment for the area near the warehouse, and initiate an ozone/air in-situ treatment of the southern contamination. This decision required a change to the 1988 selected cleanup action, and was documented in a 2004 ROD Amendment. The 2004 Amended ROD 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 Aviex facility property line;
* Monitor the attenuation of the down gradient 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 down gradient pump-and-treat system.
Five-year reviews are required whenever waste is left on site above levels that allow for unrestricted use and unrestricted exposure. The first five-year review was conducted in December 2004. The review found that the remedy was functioning as intended by the ROD. The pump-and-treat remedy reduced all contaminants of concern (COC) to very low concentrations except for 1, 2-DCA. The other COCs, i.e., benzene, chloroform, dichloromethane, ethylbenzene, toluene, xylenes, TCE, TCA, and PCE, if present, were at 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 suggests that the chemical treatment of the perched water table north of the warehouse has eliminated the source of 1, 2-DCA. All current residual 1, 2-DCA should attenuate naturally to below its MCL over the next several years. The ongoing operation and maintenance (O&M) activities at the site still include groundwater monitoring, site maintenance, and enhancements to the MNA, including the ozone sparge and treat system. The MDEQ will maintain the site until the groundwater meets the MCL cleanup criteria.
The review also found that the exposure assumptions, toxicity data, clean up levels and remedial action objectives used at the time of the remedy are still valid. MDEQ Part 201 Residential Health-Based Ground Water Criteria reflect concentrations in drinking water which are safe for both long-term and daily consumption. The criteria are calculated using currently available chemical-specific data and EPA risk assessment guidance.
The remedy is currently protective of human health and the environment, and was constructed in accordance with the EPA decision documents. On-site treatment of the perched ground water/soil and the use of in-situ ozone oxidation to address shallow contaminated groundwater augment the current MNA remedy. In order for the remedy to be protective in the long term, an assessment of the MNA activity must be continued to insure protection of human health and the environment.
The next five-year review is scheduled to be completed by December 5, 2009.
Contacts
Remedial Project Manager, U.S. EPAsheila sullivan (sullivan.sheila@epa.gov)
(312) 886-5251
Community Involvement Coordinator, U.S. EPA
cheryl allen
(312) 353-6196
Aliases
US AVIEX