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Record of Decision System (RODS)

MAIN STREET WELL FIELD

Abstract

Site Name:  MAIN STREET WELL FIELD
Address:  1120 N MAIN ST 
City & State:  ELKHART  IN  46514
County:  ELKHART
 
EPA ID:  IND980794358
EPA Region:  05
 
NPL Status:  Currently on the Final NPL
 
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R05-91/156
ROD Date:  03/29/1991
Operable Unit(s):  02
 
Media:  SOIL GROUNDWATER
 
Contaminant:  VOCS, PCE, TCE, XYLENES, OTHER ORGANICS, PAHS, METALS, ARSENIC
 
Abstract:  THE 48-ACRE MAIN STREET WELL FIELD (MSWF) SITE IS IN ELKHART, ELKHART COUNTY, INDIANA. THE WELL FIELD PROVIDES THE PRIMARY WATER SUPPLY FOR THE 44,000 CITY RESIDENTS. ADJACENT TO THE SITE ARE SEVERAL INDUSTRIAL PROPERTIES, EXCEL AND DURAKOOL TO THE EAST; ELKHART PRODUCTS TO THE WEST THAT USED TCE AND OTHER ORGANIC SOLVENTS AS PART OF THEIR OPERATIONS. THE SITE IS BOUNDED BY CHRISTIANA CREEK TO THE NORTH AND THE ST. JOSEPH RIVER TO THE SOUTH. MSWF IS LOCATED IN BOTH A WETLANDS AND A FLOODPLAIN, AND OVERLIES A SOLE SOURCE AQUIFER. SINCE THE EARLY 1900S, AN ONSITE TREATMENT AND PUMPING STATION HAS BEEN USED FOR THE PURIFICATION AND DISTRIBUTION OF WATER TO THE SURROUNDING COMMUNITY. THE WELL FIELD CONTAINS 17 PRODUCTION WELLS, TWO INTERCEPTORS USED AS PRODUCTION WELLS, TWO 2-MILLION GALLON STORAGE TANKS, AN AIR STRIPPER FACILITY, AND RECHARGE PONDS. SITE CONTAMINATION FIRST OCCURRED DURING THE 1950S WHEN PHENOLS FROM A NEARBY FUEL TANK FARM, EAST OF THE WELL FIELD, WERE DETECTED IN ONSITE WELLS. THE CONTAMINATION WAS MITIGATED BY EXCAVATING SIX RECHARGE PONDS AND DIVERTING THE WATER TO THOSE PONDS FROM CHRISTIANA CREEK. DURING ROUTINE SAMPLING IN 1981, EPA IDENTIFIED TCE CONTAMINATION IN ONSITE WELLS. SAMPLING WELLS WERE INSTALLED ON THE EXCEL AND DURAKOOL PROPERTIES, AND THE RESULTS OF THIS TESTING INDICATED THESE INDUSTRIES WERE THE LIKELY SOURCES OF CONTAMINATION. SUBSEQUENTLY IN 1981, THE CITY CONSTRUCTED TWO EASTERN INTERCEPTOR WELLS, WHICH DISCHARGED TO CHRISTIANA CREEK, AND REMOVED THE NEARBY PRODUCTION WELLS FROM SERVICE. AS A RESULT, TCE LEVELS IN FINISHING AND PRODUCTION WELLS DROPPED SIGNIFICANTLY. IN 1984, TCE LEVELS ON THE WEST SIDE OF THE FIELD INCREASED, AND EPA SUSPECTED A SECOND PLUME HAD IMPACTED THE WELL FIELD. A 1985 RECORD OF DECISION (ROD) PROVIDED FOR CONSTRUCTION OF AN AIR STRIPPING FACILITY TO TREAT WATER FROM THE SEVEN PRODUCTION WELLS AND THE TWO EASTSIDE INTERCEPTIONS. SUBSEQUENT INVESTIGATIONS FURTHER CHARACTERIZED ONSITE CONTAMINATION AND LED TO THE DISCOVERY OF A TCE-CONTAMINATED PAINT LAYER ON THE SOIL IN EASTERN AREA OF THE SITE. THIS ROD ADDRESSES MANAGEMENT OF MIGRATION OF THE WESTERN CONTAMINANT PLUME, AS WELL AS SOURCE CONTROL ON THE EAST SIDE OF THE WELL FIELD. A THIRD REMEDIAL ACTION MAY BE NECESSARY IF FURTHER ONSITE CONTAMINATION IS IDENTIFIED. THE PRIMARY CONTAMINANTS OF CONCERN AFFECTING THE SOIL AND GROUND WATER ARE VOCS INCLUDING PCE, TCE, AND XYLENES; OTHER ORGANICS INCLUDING PAHS; AND METALS INCLUDING ARSENIC.

THE SELECTED REMEDIAL ACTION FOR THIS SITE INCLUDES TREATING 22,000 CUBIC FEET OF CONTAMINATED SOIL BY IN-SITU VACUUM EXTRACTION; REMOVING THE SOIL CONTAINING THE 60 CUBIC YARDS OF SOIL CONTAINING THE PAINT LAYER, FOLLOWED BY OFFSITE INCINERATION OR SUITABLE TREATMENT BASED ON WASTE CHARACTERIZATION AND OFFSITE DISPOSAL IN ACCORDANCE WITH THE LAND DISPOSAL RESTRICTIONS SOIL AND DEBRIS TREATABILITY VARIANCE; CONSTRUCTING NEW INTERCEPTOR WELLS ON THE WEST SIDE OF THE FIELD; CONTINUED PUMPING AND TREATMENT OF GROUND WATER USING THE EXISTING AIR STRIPPING UNIT; GROUND WATER MONITORING; AND IMPLEMENTING INSTITUTIONAL CONTROLS INCLUDING DEED RESTRICTIONS. THE ESTIMATED PRESENT WORTH COST FOR THIS REMEDIAL ACTION IS $3,370,000, WHICH INCLUDES AN ESTIMATED ANNUAL O&M COST OF $130,000 FOR 20 YEARS.
 
Remedy:  THIS OPERABLE UNIT IS THE SECOND FOR THIS SITE. THE FIRST OPERABLE UNIT PROVIDED AN ALTERNATE WATER SUPPLY BY SELECTING AIR STRIPPING AS THE COST EFFECTIVE REMEDY. THE FUNCTION OF THIS SECOND OPERABLE UNIT IS TO PROVIDE REMEDIATION OF SOIL AND GROUND WATER CONTAMINATION IN AREAS OF KNOWN CONTAMINATION ON THE EAST SIDE OF THE WELL FIELD AND WELL FIELD RESTORATION BY INTERCEPTING THE PLUME FROM UNDEFINED SOURCES ON THE WEST SIDE OF THE WELL FIELD. A THIRD OPERABLE UNIT MAY BE REQUIRED IF ADDITIONAL SOURCES ARE IDENTIFIED.

THE MAJOR COMPONENTS OF THE SELECTED REMEDY INCLUDE;
* IN-SITU VACUUM EXTRACTION OF VOCS IN CONTAMINATED SOIL;
* REMOVAL OF A SMALL PAINT LAYER AND OFF-SITE DISPOSAL IN ACCORDANCE WITH THE SOIL AND DEBRIS TREATABILITY VARIANCE;
* INSTALLATION OF NEW INTERCEPTORS ON THE WEST SIDE OF THE WELL FIELD TO PREVENT CONTINUED PLUME MIGRATION INTO THE WELL FIELD AND PROVIDE WELL FIELD RESTORATION;
* CONTINUED USE OF THE EXISTING AIR STRIPPER TO ASSURE A CLEAN DRINKING WATER SUPPLY;
* GROUND WATER MONITORING TO ASSURE ADEQUATE PERFORMANCE OF THE AIR STRIPPER AND ATTAINMENT OF GROUND WATER STANDARDS;
* DEED RESTRICTIONS ON EAST SIDE PROPERTY WITH CONTAMINATED SOIL UNTIL THE SOIL AND GROUND WATER CLEANUP STANDARDS ARE MET.

PERFORMANCE STANDARDS OR GOALS; PERFORMANCE STANDARDS FOR SOIL AND GROUND WATER ARE BASED ON A (10-5) EXCESS LIFETIME CANCER RISK. CHEMICAL-SPECIFIC GOALS FOR SOIL INCLUDE TCE 100 UG/KG. INTERCEPTOR WELLS WILL REMAIN OPERATIONAL AS LONG AS PLUMES ENTERING THE FIELD HAVE CANCER RISK LEVELS GREATER THAN (10-6). CHEMICAL-SPECIFIC GOALS FOR GROUND WATER INCLUDE PCE 0.6 UG/L AND TCE 1 UG/L.
 
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