First Five-Year Review Begins, Railroad Avenue Groundwater Contamination Site, Polk County, Iowa
The U.S. Environmental Protection Agency (EPA) conducts regular five-year reviews on Superfund sites where cleanups have been completed. These reviews are required by the Superfund law [42 U.S.C. § 9621(c)]. EPA Region 7 has initiated the first five-year review of the Railroad Avenue Groundwater Contamination Site in Polk County, Iowa. The site is located in West Des Moines, a suburb of Des Moines, Iowa, and consists of the West Des Moines (WDM) water treatment plant well field, the area of observed groundwater contamination, and the potential source areas of the contamination. The site is approximately 1,000 acres in size. The WDM well field contains 22 WDM water supply wells (WDMW).
The site was first identified in 1993 when a routine water distribution sample, collected by the City of West Des Moines showed contamination. Contamination in the WDMWs was formally brought to the attention of EPA after a site investigation was conducted by the Iowa Department of Natural Resources (IDNR) at the Stearns Automotive site in 1996.
EPA performed a Preliminary Assessment/Site Inspection (PA/SI) in 1997 that identified two groundwater contaminant plumes at locations along Railroad Avenue.
An Expanded Site Inspection (ESI) was conducted by EPA in 1999 to confirm the results of the PA/SI and to investigate additional areas. Results from the ESI confirmed that there were two separate source areas and groundwater contaminant plumes in the northern and southern portions of the study area. Results also indicated a need for further investigation east of the Northern Plume and south of the Southern Plume to further delineate the plume areas and to locate any other potential source areas. Samples collected by IDNR in 2000 confirmed the results of the ESI. Remedial Investigations were performed in several phases in both plume areas between April 2001 and May 2005. The Railroad Avenue Groundwater Contamination Site was added to the National Priorities List in September 2002.Because there are two separate and distinct plumes, the site has been separated into two operable units (OUs): OU1 - Northern Plume, and OU2-Southern Plume. Despite extensive efforts, no responsible party has been identified for OU1. EPA is the lead agency for OU1. Delevan, Incorporated (Delevan) is the only currently identified potentially responsible party (PRP) for OU2. IDNR is the lead agency for OU2.
A Record of Decision (ROD) for Interim Remedial Action for the Northern Plume (OU1) was approved on September 26, 2003. This interim ROD addressed those contaminants associated with OU1 impacting WDM water supply wells (MDMW-12 and -13). The remedy selected included institutional controls, active restoration of the aquifer, treatment of extracted contaminated groundwater, and beneficial reuse of treated groundwater by the WDM water treatment plant. The remedy also included increasing the treatment capacity of the WDM water treatment plant by constructing new aerators.
Groundwater contaminants in the Northern Plume are chlorinated volatile organic compounds (VOCs), primarily trichloroethene (TCE). Northern Plume contaminants that are not captured by the WDM well field (eastern portion of OU1) are addressed in a separate ROD signed on September 19, 2005. The remedy selected in this ROD consists of institutional controls, aquifer restoration through natural attenuation, and performance monitoring to confirm the effectiveness of the attenuation process.
The source area for the Northern Plume has not been identified.
A ROD for the Southern Plume (OU2) was signed on September 11, 2006, and addresses OU2 groundwater contaminants that are not captured by the WDM well field or air-sparging wells.
Groundwater contaminants in the Southern Plume are chlorinated VOCs, primarily TCE. TCE was used as a degreasing solvent by the PRP. An underground used-solvent storage tank that was removed approximately 20 years ago by the PRP is the suspected source of the OU2 contamination.
Remediation of the Northern Plume (OU1) is being performed by EPA. EPA performs routine sampling of groundwater monitoring wells and surface water locations. The data is used to confirm the rate and direction of groundwater contaminant migration and to evaluate the effectiveness of the natural attenuation process.
Remediation of the Southern Plume (OU2) is being performed by the PRP, Delevan. Under a cooperative agreement with EPA, the WDM Water Works performs quarterly sampling of the aerator influent and effluent and provides the water quality data to the PRP on a quarterly basis. The PRP evaluates the data to identify possible performance issues with the aerators or other issues that suggest the performance of the remedial system may be inadequate. The PRP is also responsible for operation, maintenance, and annual monitoring of the source area air sparging system, and sampling of associated monitoring wells and select WDMW water supply wells.
This will be the first five-year review conducted for the Railroad Avenue Groundwater Contamination Site. During this five-year review, EPA will evaluate the institutional controls placed on the property, inspect the site, and study site files and information to make sure the remedy continues to be protective. We encourage the community to tell us about site conditions or any concerns.
At the end of the review, a final report will be prepared and will be available in the site information repositories. The goal is to complete the review and report in June 2011.
Detailed site information is available at the following locations:
West Des Moines Public Library
4000 George M. Mills Civic Parkway
West Des Moines, Iowa
EPA Region 7 Records Center
901 North Fifth Street
Kansas City, Kansas
If you have questions or need additional information on the Railroad Avenue Groundwater Contamination Site or the five-year review process, please contact:
Community Involvement Coordinator
EPA Region 7
901 North Fifth Street
Kansas City, Kansas 66101
Toll free: 1-800-223-0425