Third Five-Year Review Completed, Peoples Natural Gas Superfund Site, Dubuque, Dubuque County, Iowa
The U.S. Environmental Protection Agency (EPA) conducts regular five-year reviews on Superfund sites where cleanups have been conducted. These reviews are required by the Superfund law [42 U.S.C. Section 9621(c)]. EPA Region 7 has completed the third five-year review of the Peoples Natural Gas site in Dubuque, Dubuque County, Iowa.
The site is the location of a former coal gasification plant which manufactured gas from approximately the 1930s to 1954. Production ceased when natural gas was introduced to the community. During the operation of the plant, waste products such as coal tar were generated and disposed at the site. The coal tar contained several hazardous substances that contaminated the soil and ground water at the site. Volatile organic compounds, such as benzene, and polycyclic aromatic hydrocarbons (PAHs) were present in the soil and ground water at levels that could harm people if they were to come into contact with them.
The site occupies approximately five acres and is located between East 11th St. and Kerper Blvd., approximately one-fourth mile east of downtown Dubuque in an industrial area near the Mississippi River. The city of Dubuque owns the eastern portion of the site and the Public Works Department stores equipment on the property. Highway 61 was constructed on the western portion of the site after contaminated soil was removed and treated off site.
Following the completion of a remedial investigation and feasibility study, and an opportunity for public comment on the proposed remedy for the site, EPA presented the selected remedy in a Record of Decision (ROD). The selected remedy included the following actions:
- excavation and treatment of contaminated soil and coal tar;
- extraction and treatment of contaminated ground water in the silty sand and alluvial aquifers; and
- in-situ bioremediation of contaminated soil and ground water;
During the design of the ground water extraction and treatment system, it was determined that extracting water from the deeper of the two aquifers (the alluvial aquifer) would result in contamination being pulled down from the more heavily contaminated silty sand aquifer. The ROD was modified, through an Explanation of Significant Differences, to provide for monitoring, rather than extraction, of groundwater from the alluvial aquifer.
In December 1992, a Consent Decree was finalized with Midwest Gas (currently known as MidAmerican Energy Company), Enron Corporation, the city of Dubuque, and the Iowa Department of Transportation. They agreed to design and perform the site cleanup. MidAmerican Energy has conducted the work at the site. Excavation and treatment of contaminated soil and coal tar was completed in 1998. Extraction and treatment of ground water began in 1996. The system was shut down in 2003 due to problems with the operation of the system. Studies are underway to determine the best approach for dealing with the contaminated ground water. The in-situ bioremediation system operated from October 2000 through October 2002. Periodic monitoring of ground water in the silty sand and alluvial aquifers continues.
The first five-year review was conducted in 2000 and the second in 2005. Both reviews concluded that the site remained protective of human health and the environment.
As part of the five-year review process, EPA conducted an inspection of the site on June 1, 2010. Relevant documents were reviewed including Annual Reports for 2005 through 2009 prepared by MidAmerican Energy and reports of investigations conducted at the site during the same period of time.
This third five-year review concluded the remedy at the Peoples Natural Gas site is protective in the short-term. In order to be certain that the remedy will be protective in the long term, the following follow-up actions listed need to be taken:
- Record of Decision amended to incorporate modified remedy to address contaminated groundwater and reduced cleanup level for naphthalene in groundwater;
- Inspection of, and if needed, repair or replacement of older monitoring wells;
- Evaluation of potential sediment contamination in Dove Harbor;
- Implementation of Environmental Covenants to improve restrictions on future use of impacted properties;
It is planned that these follow-up actions will be implemented by December 31, 2011.
The final report, dated July 22, 2010, and additional detailed site information is available at the following locations:
EPA Records Center
901 N. Fifth St.
Kansas City, Kansas
Carnegie-Stout Public Library
360 W. 11th St.
Questions or requests for information can be addressed to:
Community Involvement Coordinator
U.S. EPA Region 7
901 North Fifth St.
Kansas City, KS 66101
Toll free: (800) 223-0425