Region 5 Superfund (SF)

U.S. EPA REGION 5
DANE COUNTY
DUNN

Congressional District # 02

CITY DISPOSAL CORP. LANDFILL

EPA ID# WID980610646
Last Updated: July, 2006

Site Description

The City Disposal Corporation Landfill (CDCL) site is located on approximately 38 acres of land in Dane County, Wisconsin. The landfill was opened in the mid-1960s and closed in 1977. During the years of the site's operation, the surrounding area was rural. With the growth of the Madison area, this is changing. Household wastes, industrial wastes, general construction wastes, and debris were disposed of at the site. Industrial wastes included, but were not limited to, discarded solvents from plastics manufacture, paint wastes, oily residues, etc. Total volume of wastes disposed of is approximately 700,000 cubic yards. Of the 12 cells which existed at the site for waste disposal, Cells 6 and 12 received largely industrial wastes. The site was placed on the National Priorities List (NPL) in 1984. In 1987 and 1988, various potentially responsible parties (PRPs) entered into an agreement with the United States Environmental Protection Agency (U.S. EPA) to conduct a remedial investigation and feasibility study (RI/FS). This effort was completed in 1992. The main groundwater contaminants associated with the site include: tetrahydrofuran (THF), 2- butanone, acetone, carbon tetrachloride, trichloroethene, and toluene. 

Site Responsibility

Utilizing a Consent Decree, Waste Management of Wisconsin has taken technical lead in performing necessary remedial design, remedial construction, and day-to-day operation and maintenance of treatment facilities.  U.S. EPA and Wisconsin DNR perform oversight of such activity, and review effluent quality reports and other maintenance records as generated by Waste Management of Wisconsin. 

Threats and Contaminants

Onsite groundwater and soil are contaminated with volatile organic compounds (VOCs). Potential health threats to people include: drinking contaminated groundwater, accidentally ingesting contaminated soil, inhaling contaminated dust and air particles, and coming into direct contact with contaminated groundwater and soils. Grass Lake, a habitat for sandhill cranes and other wildlife, is located about 700 feet northeast of the site and could be subject to pollution from site runoff. 

Cleanup Progress

In September 1992, U.S. EPA signed a record of decision (ROD), calling for placement of a nonhazardous waste cover over the majority of the site, placement of a hazardous waste cover over Cells 6 and 12, landfill gas venting and treatment, and groundwater extraction and treatment along with appropriate monitoring. In March 1993, U.S. EPA issued a unilateral administrative order (UAO) which required that a remedial design and remedial action (RD/RA) be conducted.  (Note - As of the summer of 2005, the UAO has been replaced by a Consent Decree which will now serve as the primary enforcement document covering site work). 

The remedial work at the City Disposal Corporation Landfill site has proceeded in two distinct phases. It was reasoned that a reduction in infiltration of precipitation through the waste mass would help in simplifying groundwater control efforts. Hence, following remedial design approval by the agencies, installation of the landfill gas collection system and clay cap was performed from June through October 1995. Work on the collection system involved the excavation of trenches followed by the installation of piping. The cap included a two-foot thick clay cap over the entire landfill, a 40-mile high density polyethylene geomembrane cap, a geonet/geotextile composite drainage layer over Cells 6 and 12, and an 18-inch cover soil and six-inch topsoil layer over the entire landfill. Attention shifted to groundwater control elements of the remedy. Since treatability tests, using site water samples, indicated nearly equal weight to treating groundwater by biological or physical-chemical means, U.S. EPA and the Wisconsin Department of Natural Resources (WDNR) worked with the potentially responsible party in devising a strategy that would promote the remedial action and help provide information to determine the most efficient and cost-effective means of permanent treatment. 

In June 1997, U.S. EPA signed with WDNR's concurrence, an explanation of significant differences (ESD) which allows groundwater extraction and interim treatment at the nearby Madison Publicly Owned Treatment Works (POTW). Under most circumstances, water could not be hauled more than five days per week, and usually only daily, and about 8,000 to 10,000 gallons of contaminated groundwater could be transported daily. WDNR carefully reviewed the ability of the POTW to accept such groundwater for an interim period of about six months and concluded that the POTW could successfully treat the groundwater. 

From September to December 1997, the potentially responsible party installed extraction pumps, electrical hookup, piping, tanks, etc. Monitoring results were compiled and temporary offsite hauling of collected groundwater began in early 1998. Basically, the degree of change in contaminant levels had provided the potentially responsible party with information necessary to make a commitment to a permanent treatment system at the City Disposal Corporation Landfill. Using information derived from the interim remedial groundwater action, design for the permanent onsite treatment system was completed in 1999, and construction of the system had begun. Construction continued in spring 2000 when the fixed-film bioreactor system came on line. Discharge is first routed to a wetland area, and subsequently to a swale to Badfish Creek.  Effluent limits were assigned by WDNR.  Monitoring will check on effluent quality and aquifer response. 

U.S. EPA signed a construction completion report for the site in June 2000, and an open-house tour was conducted for interested citizens.  The site is now in the operation and maintenance stage.  Since groundwater treatment operations began, very good removal efficiency has usually been achieved for primary contaminants of concern, such as THF (95 to 99 percent ) prior to discharge.  Initially, there were two to three very short-term episodes of process upset due to high/low water level alarm malfunction, but they were quickly repaired. After about 1.5 years of operations, organic strength of influent groundwater to be treated began a significant and steady rise. Accordingly, in August 2002 the groundwater treatment system was retrofitted, by converting an equalization to a second bioreactor tank. Since this change, discharge has again been achieving effluent limitations.

A second Five Year Review Report was completed and signed for the CDCL site in February 2005.  The primary technical finding was that site remedies as executed continue to be protective of human health and the environment.  However, there is room for improvement regarding volume of groundwater which the site treatment system is capable of handling.  The Five Year Review found that for a significant proportion of the time, the contaminated groundwater treatment system was operating within prescribed effluent limits. However, the significant organic strength of the influent groundwater generated by the extraction wells is such that extraction pumping rates have had to be throttled back. This reduction of potential extraction volume/throughput is of concern to the agencies for at least two primary reasons - a.) Time to achieve eventual site groundwater remedial goals is extended. From the data compiled to date we cannot say that we see an overall groundwater data trend as yet indicating progress toward groundwater remediation goals. b.) There is a risk that the reduced pumping rate could fail to adequately capture the plume of contaminated groundwater, such that future off-site migration is a possibility.

As of November 2005, technical consultants for Waste Management of Wisconsin, Inc., the current owner and a former operator of the site preforming site cleanup with oversight from U.S. EPA and WDNR, are conducting pilot studies to dose contaminated groundwater "in-situ" with oxidizing agents prior to the water being pumped into the bioreactor treatment system.  Results will be evaluated to see if scale-up of this technique is advisable, in an effort to improve groundwater treatment efficiency.  

 Initial results with the oxidizing agents were encouraging during early 2006.  In June 2006, a report describing pilot work highlights is expected.  U.S. EPA  and WDNR will evaluate this report to determine if scale-up is warranted.

 

Contacts

Remedial Project Manager, U.S. EPA
Karen Mason-Smith (mason-smith.karen@epa.gov)
(312) 886-6150

 

Aliases

CITY DISPOSAL CORP LDFL
CITY DSPL SAN LDFL
CITY DISPOSAL CORP LANDFILL

 

Site Profile Information

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