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A.. g~~~~:~~c. 1801 Highway 8, Suite 114 St. Paul, MN 55112 612/636-2427 FAX:612/636-8552 September 7, 1990 Mr. Rick Jopke City of Roseville 2660 Civic Center Drive Roseville, MN 55113 Subject: Ground Water/Contamination Sub-Surface Remediation System B-Dale Amoco 2164 North Dale Street Roseville, Minnesota Delta No. 10-88-535 Dear Mr. Jopke: Enclosed are 25 copies of the plans for the remediation system at the referenced site. Delta Environmental Consultants, Inc. (Delta), on behalf of Amoco Oil Company, is requesting permission to implement construction of the remediation system. As we discussed in our meeting on Wednesday, August 29, 1990, leaking distribution lines and underground storage tanks have contaminated the local ground water and sub-surface soils. The lines and tanks have been replaced but some contamination remains. A soil venting system will address the issue of sub-soil contamination. A ground water recovery system will address the ground water contamination. During the operation of the soil vent system, air is drawn through the soils and removed by extraction points which are plumbed into a vacuum blower. The blower and piping manifold are housed in a treatment building. The vapors removed by the vacuum blower are exhausted to the atmosphere. The locations of the extraction vents and the treatment building are shown in Figures G-3.1 and G-3.2. Contaminated ground water will be removed via a ground water recovery well. The location of the recovery well (RW-1) is depicted in Figures G-3.1 and G-3.2. Ground water, mixed with gasoline, is pumped back to the treatment building and into a gasoline/water separator tank. Water flows from the separator tank to a diffused aeration tank. Dissolved hydrocarbons are volatilized out of the water and exhausted to the atmosphere. The treated water is discharged to the sanitary sewer system. A process flow diagram outlining the various treatment stages can be found in Figure 1-1. The treatment building is constructed of wood with vinyl siding. It houses the equipment required for the remediation process. The layout of equipment in the interior of the building is shown in Figure Li. The construction specifications of the building are shown in Figure Ai. The building will be set on a concrete. pad with a bermed edge. The berm will have a containment volume Practical Solutions to Environmental Concerns