INDIANA DEPARTMENT OF ENVIRONMENTAL MANAGEMENT We ProtectHoosiers andOurEnvironment. 100 N. SenateAvenue • Indianapolis, IN 46204 (800) 451-6027 • (317) 232-8603 • www.idem.IN.gov Michael R. Pence Thomas W. Easterly Governor Commissioner 

### August 13, 2015

Ms. Susan Hedman Regional Administrator U.S. EPA, Region V, R-19J 77 West Jackson Boulevard Chicago, Illinois 60604-3507
Dear Ms. Hedman:
Re: Proposed Inclusion ofthe Riverside Ground WaterContamination Site Indianapolis, Marion County, Indiana on the National Priorities List of HazardousWaste Sites
The Indiana Department of Environmental Management (IDEM) is providing this letterto convey its supportto the United States Environmental Protection Agency (U.S. EPA) regarding inclusion ofthe Riverside Ground Water Contamination site on the National Priorities List (NPL) of hazardous waste sites. The Riverside Ground Water Contamination site is a contaminated ground water plumethat encompasses an area of approximately 62 acres and affects two wellfields.
The Citizens Energy Group operates the drinking water utility forthe city of Indianapolis. Rawwater sample results obtained by IDEM from five (5) municipal wells confirmed detections ofvinyl chloride (VC) and trichloroethylene (TCE). TheVC and TCE levels in two ofthe wells exceed U.S. EPA Superfund Chemical Data Matrix benchmarks. The impacted wells provide drinking waterto more than 10,000 people in Indianapolis. IDEM has identified over 100 potential sources ofcontamination to the well fields, including sites in the Voluntary Remediation Program, RCRA Corrective Action Program, Brownfields Program, and the State Cleanup Program, but a definitive source ofthe contamination has not been identified.
This site qualifies for inclusion on the NPL because: 1) The site meets the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) criteria for listing on the NPL, scoring sufficiently high pursuantto the Hazard Ranking System (HRS). 2) The site requires a long-term response action. 

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An NPL listing would allowfor proper and timely investigation ofthe nature and extent of the contamination ofthe potential sources and enable the U.S. EPA to determine cleanup alternatives forthe impacted areas, thereby protecting human health and the environment. The NPL listing appears to be the most viable alternative foraddressing the existing environmental problems.
As the Commissionerof IDEM, I am authorized by Indiana Governor Michael R. Pence to act in these matters on his behalf. I have considered my staff's recommendations and Ifully supportthe designation ofthe Riverside Ground Water Contamanition site for inclusion on the NPL. I request thatthe U.S. EPA assign a Remedial Project Manager and/orOn-Scene Coordinatorto implementthe process. Ifyou require any additional information or have any questions, please contact Mark Jaworski ofthe Site Investigation Program at 317/233-2407 or via e-mail at mjaworsk@idem.in.gov.

ThomasW. Easterly Commissioner

cc: Denise Boone, U.S. EPA Nuria Muniz, U.S. EPA Mark Jaworski, IDEM Rex Osborn, IDEM