Record of Decision System (RODS)
EAST BETHEL DEMOLITION LANDFILL
|Site Name:||EAST BETHEL DEMOLITION LANDFILL|
|Address:||HWY 65 AT 22 1ST AVE|
|City & State:||EAST BETHEL TOWNSHIP MN 55011|
|NPL Status:||Deleted from the Final NPL|
|ROD Type:||Record of Decision|
|Abstract:||The 60-acre East Bethel Demolition Landfill is a permitted landfill located in East Bethel, Anoka County, Minnesota. Abundant wetlands are present in the general vicinity of the landfill and the closest surface water body, Neds Lake, is located 1,000 feet from the site. The site overlies four aquifers, two of which appear to be hydraulically connected. Land use in the area is predominantly recreational, agricultural, and commercial. Since 1969, the landfill has been owned and operated by the Sylvester Brothers Development Company. Beginning in 1971, the site accepted mixed demolition debris, along with a small amount of municipal waste; and from 1969 to 1976, a limited amount of industrial waste also was accepted at thelandfill. In 1981, the county modified the landfill ground water requirements, and during routine sampling, identified elevated levels of VOCs and other compounds in onsite monitoring wells. The source of site contamination stems from the 1.2 million yd of solid and industrial waste debris disposed of onsite. In 1989, at the request of the County, an interim response action pumping (IRAP) system was installed, which included a metals precipitation tank to remove iron and an air stripping column to remove VOCs, with discharge to an onsite wooded area. This ROD addresses the contaminated onsite ground water, as 0U1. A future ROD will address the landfill, which is the source of contamination, as 0U2. The primary contaminants of concern affecting the ground water are VOCs, including benzene, PCE, and TCE. SELECTED REMEDIAL ACTION: The selected remedial action for the site includes installing a ground water capture system in the A/B and C horizon aquifers and pretreating approximately 140 million gallons of contaminated ground water using precipitation, flocculation, and clarification to remove metals, followed by air stripping to remove VOCs; providing additional aeration via a rip-rap spill way, prior to discharge to Neds Lake; and disposing of any sludge generated during the treatment process offsite in accordance with RCRA requirements. The estimated present worth cost for this remedial action is $4,196,722, which includes an annual O&M cost of $246,605 for 30 years. PERFORMANCE STANDARDS OR GOALS: Ground water remediation goals are based on the more stringent of SDWA MCLs and MDH Recommended Allowable Levels (RALs). Chemical-specific ground water cleanup goals include benzene5 ug/l; 1,1-DCA 70 ug/l; 1,2-DCA 4 ug/l; 1,2-DCE 70 ug/l; 1,1,2,2- tetrachlorethylene 5 ug/l; 1,1,2trichloroethylene 5 ug/l; and vinyl chloride 0.1 ug/l. INSTITUTIONAL CONTROLS: Not provided.|
This operable unit is the first of two operable units for the site. The operable unit described in this decision document addresses ground water contamination. The second operable unit will address the source of contamination, the landfill.
The remedy selected for ground water contamination consists of withdrawal of contaminated ground water, treatment of ground water, and discharge of treated water, as well as continued monitoring of the contaminated aquifers. This remedy addresses remediation of ground water by eliminating or reducing the risks posed by the site, through engineering controls.
The major components of the selected remedy include:
* The installation of a ground water capture system in the A/B and C-horizon aquifers;
* Treatment of captured ground water utilizing metals pretreatment with diffused aeration; and
* Additional aeration via a rip-rap spillway prior to discharge to Neds Lake.
This action will require operation and maintenance activities to ensure continued effectiveness of the remedial alternative. The action being taken is consistent with Section 121 of CERCLA as amended by SARA, 42 U.S.C. Section 9621 and MERLA.
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