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Record of Decision System (RODS)

TYBOUTS CORNER LANDFILL

Abstract

Site Name:  TYBOUTS CORNER LANDFILL
Address:  US RTE 13 & DEL RTE 71 
City & State:  NEW CASTLE  DE  19720
County:  NEW CASTLE
 
EPA ID:  DED000606079
EPA Region:  03
 
NPL Status:  Currently on the Final NPL
 
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R03-86/019
ROD Date:  03/06/1986
Operable Unit(s):  01
 
Media:  GROUNDWATER SOIL
 
Contaminant:  BENZENE, TCE, VINYL CHLORIDE, VOCS, XYLENES
 
Abstract:  THE TYBOUTS CORNER LANDFILL SITE IS LOCATED IN NORTHERN DELAWARE, APPROXIMATELY TEN MILES SOUTH OF WILMINGTON, IN NEW CASTLE COUNTY. THE LANDFILL CONSISTS OF TWO FILL AREAS. THE MAIN FILL IS ABOUT 47 ACRES IN SIZE AND IS LOCATED NEAR THE CONFLUENCE OF PIGEON RUN AND RED LION CREEK. A SMALLER FILL AREA, ESTIMATED TO BE ABOUT FOUR ACRES, IS LOCATED JUST WEST OF PIGEON RUN. THE SITE WAS ORIGINALLY A SAND AND GRAVEL PIT. WHEN THE LANDFILL BEGAN TO OPERATE, PLANS INDICATE THAT NO CLAY LINER OR OTHER IMPERVIOUS MATERIAL WAS PLACED BELOW THE FILL AND NO IMPERVIOUS CAP WAS PLACED ON THE TOP OF THE FILL FOLLOWING ABANDONMENT. TYBOUTS CORNER LANDFILL WAS USED BY THE NEW CASTLE COUNTY DEPARTMENT OF PUBLIC WORKS AS A MUNICIPAL SANITARY LANDFILL FOR THE DISPOSAL OF MUNICIPAL AND DOMESTIC REFUSE FROM DECEMBER 1968 UNTIL JULY 1971. IN ADDITION, INDUSTRIAL WASTES WERE DISPOSED THERE DURING THE ACTIVE LIFE OF THE LANDFILL. THESE INDUSTRIAL WASTES INCLUDED; TRICHLOROETHYLENE, VINYL CHLORIDE, 1,2-DICHLOROETHANE, BENZENE AND VARIOUS OTHER ORGANIC AND INORGANIC CHEMICALS.

THE MAIN THREAT POSED BY TYBOUTS CORNER LANDFILL IS THAT THE HAZARDOUS SUBSTANCES DISPOSED OF IN THE LANDFILL ARE CONTAMINATING THE LOCAL AND REGIONAL AQUIFERS WHICH ARE A MAIN SOURCE OF WATER FOR THE REGION. THE SELECTED REMEDIAL ACTION FOR THIS SITE INCLUDES; EXCAVATION OF ALL MUNICIPAL AND INDUSTRIAL WASTES, AS WELL AS CONTAMINATED SUBSOILS IN THE WEST FILL AND CONSOLIDATION WITH THE MAIN FILL; CAPPING OF THE CONSOLIDATED MAIN FILL AREA WITH A MULTI-LAYERED RCRA CAP; INSTALLATION OF A SUBSURFACE DRAIN OR TRENCH SYSTEM; IMPLEMENTATION OF A HEALTH AND SAFETY PLAN; AND ESTABLISHING A MONITORING PROGRAM. IN ADDITION, THE OFFSITE PLUME OF CONTAMINATED GROUND WATER IN THE UPPER HYDROLOGIC ZONE (UHZ) OF THE POTOMAC WILL BE PUMPED AND TREATED OR OTHERWISE DISPOSED OF, EITHER ONSITE OR OFFSITE AT A LOCAL SEWAGE TREATMENT PLANT. THE GOAL OF THE OFFSITE GROUND WATER TREATMENT WILL BE TO REDUCE THE LEVEL OF CONTAMINANTS TO 100 PPB OF TOTAL VOLATILE ORGANICS, AND 10-4 CANCER RISK LEVEL FOR CANCER-CAUSING CONTAMINANTS. DURING THE PUMPING, INSTITUTIONAL CONTROLS WILL BE UTILIZED TO PREVENT USE OF CONTAMINATED GROUND WATER. THE ROD DOES NOT PROVIDE ESTIMATED CAPITAL COST AND ANNUAL O&M COSTS FOR THE SELECTED REMEDIAL ACTION.
 
Remedy:  1) THE WEST FILL WILL BE EXCAVATED AND CONSOLIDATED WITH THE MAIN FILL. EXCAVATION WILL INCLUDE ALL MUNICIPAL AND INDUSTRIAL WASTES AS WELL AS CONTAMINATED SUBSOILS. THE AMOUNT OF CONTAMINATED SUBSOIL TO BE REMOVED WILL BE BASED ON A SITE-SPECIFIC CHEMICAL FATE AND TRANSPORT ANALYSIS. THIS ANALYSIS WILL BE CONDUCTED TO ENSURE THAT NO SOIL REMAINS IN PLACE WHICH COULD CAUSE GROUND WATER CONTAMINATION TO EXCEED THE STANDARDS ESTABLISHED IN THIS RECORD OF DECISION. THE EXCAVATED AREA WILL BE BACKFILLED WITH SUITABLE CLEAN FILL MATERIAL.
2) A MULTI-LAYERED CAP THAT COMPLIES WITH RCRA WILL BE PLACED OVER THE CONSOLIDATED MAIN FILL AREA TO SIGNIFICANTLY REDUCE OR ELIMINATE THE VERTICAL INFILTRATION OF PRECIPITATION.
3) A SUBSURFACE DRAIN OR TRENCH SYSTEM WILL BE INSTALLED TO PROHIBIT CONTINUED LATERAL MIGRATION OF GROUND WATER THROUGH THE FILL AND TO COLLECT EXISTING LEACHATE FROM THE FILL. THE MULTI-LAYERED CAP AND THE SUBSURFACE DRAIN/TRENCH SYSTEM TOGETHER ARE INTENDED TO DEWATER THE CONSOLIDATED FILL. THIS GROUND WATER DIVERSION SYSTEM AND MULTI-LAYERED CAP WILL BE MAINTAINED UNTIL THEY ARE NO LONGER NEEDED.
4) THE OFFSITE PLUME OF CONTAMINATED GROUND WATER IN THE UPPER HYDROLOGIC ZONE (UHZ) OF THE POTOMAC WILL BE PUMPED AND TREATED OR OTHERWISE DISPOSED OF, EITHER ONSITE OR OFFSITE. DURING THE PUMPING, INSTITUTIONAL CONTROLS WILL BE UTILIZED TO PREVENT USE OF CONTAMINATED GROUND WATER. THE GOAL OF THE OFFSITE GROUND WATER TREATMENT WILL BE TO REDUCE THE LEVEL OF CONTAMINANTS TO 100 PPB OF TOTAL VOLATILE ORGANICS WITH SEPARATE STANDARDS FOR CANCER-CAUSING CONTAMINANTS. THE LEVELS FOR THESE SPECIFIC SUBSTANCES ARE LISTED IN THE BODY OF THE RECOMMENDED ALTERNATIVE AND ARE SELECTED TO MEET A 10-4 CANCER RISK LEVEL AT THE BOUNDARY OF THE LANDFILL PROPERTY. A 10-4 LEVEL WAS SELECTED BECAUSE IT IS NOT TECHNICALLY FEASIBLE TO ATTAIN THE 10-6 RISK LEVEL. EPA WILL EVALUATE GROUND WATER CONTAMINATION LEVELS AFTER THREE, SIX AND TEN YEARS OF PUMPING AND TREATING. IF THE STANDARDS ARE MET AT ANY OF THE EVALUATION POINTS, PUMPING WILL BE DISCONTINUED. IF, AFTER A TEN-YEAR PUMPING PERIOD, STANDARDS HAVE STILL NOT BEEN MET, EPA WILL EVALUATE THE TECHNICAL FEASIBILITY OF MEETING THE STANDARDS AND SET NEW ONES IF NECESSARY. PUMPING MAY BE TERMINATED IF IT IS SHOWN THAT NO REASONABLE MODIFICATION OF THE PUMPING SYSTEM WOULD PRODUCE SIGNIFICANT IMPROVEMENT. EPA WILL THEN EXAMINE THE NEED FOR ADDITIONAL MONITORING LOCATIONS TO ASSURE THAT THE INFLUENCE OF ANY OFFSITE PRODUCTION WELL WILL NOT CAUSE THE REMAINING CONTAMINATED GROUND WATER FROM TYBOUTS CORNER LANDFILL TO MIGRATE AWAY FROM THE SITE.
5) CONTAMINATED WATER GENERATED BY EXCAVATION, CONSTRUCTION, SUBSURFACE DRAINAGE SYSTEM COLLECTION AND GROUND WATER PUMPING WILL EITHER BE SENT TO A LOCAL SEWAGE TREATMENT PLANT OFFSITE, OR TREATED ONSITE. IT IS POSSIBLE THAT A COMBINATION OF THESE TWO TREATMENT SYSTEMS AND LOCATIONS WILL BE USED. ALL TREATED WATER WILL MEET NPDES STANDARDS BEFORE DISPOSAL TO SURFACE WATERS, INCLUDING ANY PRETREATMENT REQUIREMENTS IF THE SEWAGE TREATMENT IS UTILIZED. ALL WATERS WILL BE DISPOSED OF IN COMPLIANCE WITH LOCAL, STATE AND FEDERAL LAW.
6) A HEALTH AND SAFETY PLAN WILL BE IMPLEMENTED FOR ALL ACTIVITIES DESCRIBED IN THIS RECORD OF DECISION. DURING EXCAVATION AND CONSTRUCTION ACTIVITIES, AIR MONITORING WILL BE CONDUCTED TO ENSURE THE SAFETY OF THE ONSITE WORKERS AS WELL AS TO PROTECT THE RESIDENTS LIVING NEARBY THE EXCAVATED AREAS.
7) A MONITORING PROGRAM WILL BE ESTABLISHED TO ENSURE THAT GROUND WATER QUALITY, SURFACE WATER QUALITY, THE MULTI-LAYER CAP AND AIR QUALITY ARE MAINTAINED.
 
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