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Record of Decision System (RODS)

NEW BRIGHTON/ARDEN HILLS/TCAAP (USARMY)

Abstract

Site Name:  NEW BRIGHTON/ARDEN HILLS/TCAAP (USARMY)
Address:  JCT HWY 10 & MN HWY 96S 
City & State:  NEW BRIGHTON  MN  55112
County:  RAMSEY
 
EPA ID:  MN7213820908
EPA Region:  05
 
NPL Status:  Currently on the Final NPL
 
ROD Type:  Record of Decision
ROD ID:  EPA/ROD/R05-87/058
ROD Date:  09/25/1987
Operable Unit(s):  06
 
Media:  GROUNDWATER
 
Contaminant:  HEAVY METALS (LEAD, ARSENIC, CHROMIUM), PCB, VOCS
 
Abstract:  THE TWIN CITIES ARMY AMMUNITION PLANT (TCAAP) IS LOCATED NORTH OF THE TWIN CITIES OF MINNEAPOLIS/ST. PAUL, MINNESOTA AND COMPRISES THE NORTHERN EDGE OF THE NEW BRIGHTON/ARDEN HILLS/ST. ANTHONY (NBAHSA) SUPERFUND NPL SITE. FOURTEEN IDENTIFIED SOURCE AREAS EXIST IN THE TCAAP AND THREE SITES ARE EXPECTED TO BE THE SOURCE OF VOC CONTAMINATION EMANATING FROM THE SOUTHWEST BOUNDARY. THE U.S. ARMY ESTIMATES APPROXIMATELY 26 POUNDS PER DAY OF VOC CONTAMINANTS ARE MIGRATING OFF TCAAP INTO THE GROUND WATER AT THE SOUTHWEST BOUNDARY OF TCAAP. THIS CONTAMINATION IS MIGRATING IN BOTH THE HILLSIDE SAND AQUIFER AND THE DEEPER PRAIRIE DU CHIEN/JORDAN AQUIFER (BOTH ARE AQUIFERS THAT SUPPLY WATER TO THE CITIES OF NEW BRIGHTON AND ST. ANTHONY). BOTH OF THESE CITIES HAVE MADE MODIFICATIONS TO THEIR WATER SUPPLY DUE TO GROUND WATER CONTAMINATION. FROM 1982 TO 1984 VARIOUS MUNICIPAL WELLS WERE DEEPENED, SHUT DOWN OR HAD CARBON FILTERS INSTALLED. SEVERAL PRIVATE WELL USERS ADJACENT TO THE TCAAP SITE WERE CONNECTED TO CITY WATER SUPPLIES. THREE PREVIOUS RODS FOR THE NBAHSA SITE HAVE RECOMMENDED AN ADDITIONAL WELL FOR NEW BRIGHTON FROM AN ALTERNATE AQUIFER, CARBON TREATMENT FOR TWO OF ST. ANTHONY'S WELLS AND CONSTRUCTION OF A BOUNDARY GROUND WATER RECOVERY SYSTEM (BGRS) TO INTERCEPT THE CONTAMINANT PLUME. THIS OPERABLE UNIT SOURCE CONTROL RODS ADDRESSES OPERATION OF THE BGRS, COLLECTION OF OPERATING DATA IN ORDER TO EVALUATE THE SYSTEM AND MODIFICATION OF THE SYSTEM, AS NECESSARY, TO ENSURE INTERCEPTION OF CONTAMINATED GROUND WATER IN THE TWO AFFECTED AQUIFERS. THE PRIMARY CONTAMINANTS OF CONCERN AFFECTING THE GROUND WATER INCLUDE; PCBS, BENZENE, TOLUENE, TCE, VOCS, ARSENIC, CHROMIUM, LEAD AND METALS.

THE SELECTED REMEDIAL ACTION FOR THIS SITE INCLUDES; OPERATION OF A SIX-WELL SYSTEM TO EXTRACT GROUND WATER MIGRATING FROM THE SOUTHWEST CORNER OF TCAAP AND TREATMENT WITH AIR STRIPPING. APPROXIMATELY 300,000 GALLONS PER DAY WILL BE UTILIZED FOR IN-PLANT USE WITH THE REMAINDER DISPOSED OF BY REINJECTION/INFILTRATION THROUGH THE ARSENAL SAND AND GRAVEL PIT; EVALUATION OF OPERATING DATA AND MONITORING RESULTS AND IMPLEMENTATION OF ANY ADDITIONAL MEASURES REQUIRED TO CAPTURE CONTAMINATED GROUND WATER MIGRATING FROM THE SITE. THE ESTIMATED CAPITAL COST FOR THIS REMEDIAL ACTION IS $4,000,000 WITH ANNUAL O&M OF $120,000. ADDITIONAL CAPITAL EXPENDITURES MAY OCCUR IF MODIFICATIONS TO THE SYSTEM ARE NEEDED TO ACHIEVE ADEQUATE WATER QUALITY.
 
Remedy:  - OPERATION OF A GROUNDWATER EXTRACTION SYSTEM USING EXISTING WELLS WITH POSSIBLE EXPANSION OF THE SYSTEM AS REQUIRED FOR THE PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT IN BOTH THE PRAIRIE DU CHIEN/JORDAN AND HILLSIDE SAND AQUIFERS.
- EXTRACTION OF CONTAMINATED GROUNDWATER FOR HYDRAULIC GRADIENT CONTROL AT THE SOUTHWEST BOUNDARY OF THE TCAAP.
- CONTAMINATED GROUNDWATER WILL BE TREATED TO MEET DISCHARGE REQUIREMENTS.
- PRIOR TO 150 DAYS AFTER STARTUP ANY MODIFICATIONS REQUIRED TO ADEQUATELY PROTECT BOTH THE HILLSIDE SAND AND PRAIRIE DU CHIEN/JORDAN AQUIFERS WILL BE EVALUATED USING THE DATA COLLECTED IN THE FIRST 90 DAYS AND SUBMITTED TO U.S. EPA AND MPCA.
- 150 DAYS AFTER U.S. EPA AND MPCA DETERMINE THE PROPOSED MODIFICATIONS TO BE CONSISTENT UNDER PART XIV OF THE TCAAP FEDERAL FACILITY AGREEMENT, THE MODIFICATIONS WILL BE CONSTRUCTED AND OPERATED.
 
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