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Record of Decision System (RODS)

ONALASKA MUNICIPAL LANDFILL

Abstract

Site Name:  ONALASKA MUNICIPAL LANDFILL
Address:  SPORTMAN RD 
City & State:  ONALASKA  WI  54650
County:  LA CROSSE
 
EPA ID:  WID980821656
EPA Region:  05
 
NPL Status:  Currently on the Final NPL
 
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R05-90/125
ROD Date:  08/14/1990
Operable Unit(s):  01
 
Media:  SOIL GROUNDWATER
 
Contaminant:  VOCS, BENZENE, TOLUENE, XYLENES, TCE, OTHER ORGANICS, PAHS
 
Abstract:  THE 11-ACRE ONALASKA MUNICIPAL LANDFILL SITE INCLUDES A 7-ACRE LANDFILL OWNED BY THE TOWNSHIP OF ONALASKA, WHICH IS LOCATED IN CENTRAL-WESTERN WISCONSIN. THE BLACK RIVER AND ITS ASSOCIATED WETLANDS ARE 400 FEET WEST OF THE SITE AND LIE WITHIN A WILDLIFE AND FISH REFUGE. THE SITE WAS OPERATED AS A SAND AND GRAVEL QUARRY UNTIL THE LATE 1960S, WHEN IT WAS CONVERTED AND USED AS A MUNICIPAL LANDFILL UNTIL 1980. ALTHOUGH THE SITE WAS PRIMARILY USED TO DISPOSE OF MUNICIPAL WASTES, SOLVENT WASTES WERE ALSO DISPOSED OF ONSITE UNTIL 1976. APPROXIMATELY 320,000 GALLONS OF LIQUID SOLVENT WASTE AND APPROXIMATELY 1,000 DRUMS OF SOLVENT WASTE WERE EITHER BURNED WITH OTHER TRASH ONSITE OR POURED DIRECTLY INTO HOLES FOR BURIAL IN THE SOUTHWESTERN PORTION OF THE LANDFILL. THE TOWNSHIP CAPPED THE LANDFILL IN 1982, BUT SUBSEQUENT ONSITE INVESTIGATIONS REVEALED GROUND WATER CONTAMINATION WITHIN AND AROUND THE SITE. GROUND WATER FLOWS BENEATH THE LANDFILL, WHERE IT COMES INTO CONTACT WITH SOLVENTS LEAKING FROM THE SOLVENT DISPOSAL AREA. THE GROUND WATER FLOWS IN A SOUTHWESTERLY DIRECTION AND A GROUND WATER CONTAMINANT PLUME HAS MIGRATED FROM THE SOUTHWESTERN EDGE OF THE LANDFILL AND APPEARS TO BE DISCHARGING INTO THE WETLANDS. THIS RECORD OF DECISION ADDRESSES TWO OPERABLE UNITS, THE GROUND WATER PLUME AND THE CONTAMINATED SOIL ADJACENT TO THE SOUTHWESTERN PORTION OF THE LANDFILL, WHICH IS A MAJOR SOURCE OF GROUND WATER CONTAMINATION. THE PRIMARY CONTAMINANTS OF CONCERN AFFECTING THE SOIL AND GROUND WATER ARE VOCS, INCLUDING BENZENE, TOLUENE, XYLENES, AND TCE; OTHER ORGANICS INCLUDING PAHS; AND METALS INCLUDING ARSENIC AND LEAD.

THE SELECTED REMEDIAL ACTION FOR THIS SITE INCLUDES IN-SITU BIOREMEDIATION OF THE SOLVENT-CONTAMINATED SOIL AND, IF FEASIBLE, A PORTION OF THE LANDFILL DEBRIS; PUMPING AND TREATMENT OF THE GROUND WATER PLUME USING AERATION, CLARIFICATION, AND FILTRATION, FOLLOWED BY DISCHARGE OF THE TREATED GROUND WATER INTO THE BLACK RIVER AND ONSITE DISPOSAL OF THE SLUDGE GENERATED DURING THE TREATMENT PROCESS; RECONSTRUCTION OF THE LANDFILL CAP AND INSTALLATION OF A PASSIVE METHANE GAS VENTING SYSTEM TO CONTROL THE GAS BUILDUP UNDER THE CAP; GROUND WATER MONITORING; AND IMPLEMENTATION OF INSTITUTIONAL CONTROLS INCLUDING DEED RESTRICTIONS LIMITING GROUND WATER AND SURFACE WATER USE. THE ESTIMATED PRESENT WORTH COST FOR THIS REMEDIAL ACTION IS $8,000,000, WHICH INCLUDES AN ANNUAL O&M COST OF $164,000 FOR 30 YEARS.

PERFORMANCE STANDARDS OR GOALS: CHEMICAL-SPECIFIC SOIL CLEANUP STANDARDS WERE NOT PROVIDED BUT WILL BE ESTABLISHED ONCE THE REDUCTION RATE FOR BIOREMEDIATION HAS BEEN DETERMINED DURING THE PILOT-SCALE TEST. CURRENTLY, THE ESTIMATED CLEANUP GOAL IS AN 80-95 PERCENT REDUCTION OF THE ORGANIC CONTAMINANT MASS IN THE SOIL. GROUND WATER AT THE LANDFILL WASTE BOUNDARY WILL MEET SDWA MCLS OR NON-ZERO MCLGS. CHEMICAL-SPECIFIC CLEANUP STANDARDS FOR THE GROUND WATER BEYOND THE SITE BOUNDARY ARE BASED ON STATE CLEANUP LEVELS AND INCLUDE BENZENE 0. 067 UG/1, TOLUENE 68.6 UG/1, XYLENES 124 UG/1, TCE 0.18 UG/1, ARSENIC 5 UG/1, AND LEAD 5 UG/1. THE RECONSTRUCTED CAP IS PROJECTED TO REDUCE THE RATE OF PRECIPITATION INFILTRATION BY 80 PERCENT, THEREBY MINIMIZING CONTAMINANT MIGRATION TOWARD THE GROUND WATER.
 
Remedy:  THE SELECTED REMEDY IS A FINAL REMEDY, AND IT USES TREATMENT TO ADDRESS THE PRINCIPAL THREATS AT THE SITE - THE GROUNDWATER CONTAMINANT PLUME AND A MAJOR SOURCE OF GROUND-WATER CONTAMINATION (THE NAPHTHA-CONTAMINATED SOILS). THE SELECTED REMEDY ALSO ADDRESSES THE LONG-TERM, LOW-LEVEL THREAT POSED BY THE LANDFILL CONTENTS AND CONSISTS OF THE FOLLOWING COMPONENTS:

* EXTRACTION AND TREATMENT OF THE GROUND-WATER CONTAMINANT PLUME TO MEET FEDERAL DRINKING-WATER STANDARDS AND STATE GROUND-WATER QUALITY STANDARDS. THE TREATED WATER SHALL BE DISCHARGED INTO THE ADJACENT BLACK RIVER IN COMPLIANCE WITH THE SUBSTANTIVE REQUIREMENTS OF THE WISCONSIN POLLUTANT DISCHARGE ELIMINATION SYSTEM (WPDES);
* RECONSTRUCTION OF THE LANDFILL COVER (CAP) IN COMPLIANCE WITH CHAPTER NR 504.07, WISCONSIN ADMINISTRATIVE CODE (WAC) LANDFILL CLOSURE REQUIREMENTS;
* IMPLEMENTATION OF ENHANCED, IN SITU BIOREMEDIATION IN THE NAPHTHA-CONTAMINATED SOILS AND, IF FEASIBLE, WITHIN A PORTION OF THE LANDFILL DEBRIS. THE ESTIMATED TARGET CLEANUP GOAL FOR BIOREMEDIATION IS 80-95 PERCENT REDUCTION OF THE MASS OF ORGANIC CONTAMINANTS. A TREATABILITY STUDY AND A PILOT-SCALE TEST WILL BE PERFORMED TO DETERMINE THE SOIL CLEANUP STANDARD FOR BIOREMEDIATION;
* PERIODIC MONITORING OF THE GROUND-WATER CONTAMINANT PLUME;
* IMPOSITION OF DEED RESTRICTIONS LIMITING SURFACE AND GROUNDWATER USE AT THE SITE; AND,
* CONTINUED RELIANCE ON STATE INSTITUTIONAL CONTROLS GOVERNING GROUNDWATER USE WITHIN THE PROXIMITY OF LANDFILLS AND THE DEVELOPMENT OF LANDFILLS.
 
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