Agenda - Council Work Session - 03/29/2011

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3.0 Project Background 3.1. Previous Subsurface Investigation Results Former Oasis Mart RAP /CCP Project SP- 09- 003784A November 16, 2009 Page 2 A limited subsurface investigation was conducted by DPRA in 1994 to evaluate site soils as part of an environmental due diligence project for Scrivner /Gateway Foods. One soil boring was advanced adjacent to and south of the underground storage tank (UST) basin and pump islands. One soil sample was collected at 5 feet below ground surface (bgs) and analyzed for benzene, toluene, ethylbenzene, total xylenes (BTEX), total recoverable petroleum hydrocarbons (TRPH), and total hydrocarbons as gasoline (THCG). All concentrations were below laboratory method reporting limits except TRPH, which was detected at 90 mg /kg. The State Duty Officer was notified of the release, and the site assigned Leak # 7470 by the Minnesota Pollution Control Agency (MPCA) on June 27, 1994. The results of the limited subsurface investigation were submitted to the MPCA (DPRA, 1994). Based on the results of the subsurface investigation, the MPCA issued a No Corrective Action Required letter on September 30, 1994. Petroleum- impacted soil was encountered during piping and dispenser upgrade activities in 1999. Approximately 15 cubic yards of petroleum- impacted soil was stockpiled, then screened with a photo - ionization detector (PID) and sampled for petroleum volatile organic compounds (PVOCs), diesel range organics (DRO), gasoline range organics (GRO), and total lead by Liesch & Associates. Stockpiled soils had a maximum PID reading of 40.2 parts per million (ppm). Soil analytical results were compared with Tier 2 Residential Soil Reference Values (SRVs). With the exception of GRO and DRO, for which Tier 2 SRVs have not been established, all compounds were at least one order of magnitude below their applicable Tier 2 Residential SRVs. A total of 8.14 cubic yards of the petroleum- impacted soil was taken to C.S. McCrossen for thermal treatment; the remaining petroleum- impacted soil was re -used as backfill during upgrade activities. The results were reported in Liesch, 1999. A Limited Site Investigation (LSI) was conducted by R.J. Rykken Consulting, Inc. in 2004 (RJR, 2004) to evaluate soil and groundwater in the vicinity of the UST basin, which was described as containing two 10,000 - gallon USTs, and pump islands. The LSI consisted of three soil borings located adjacent to and east, west, and south of the UST basin and pump islands. No visual and olfactory indications of soil impacts were observed, and PID readings did not exceed 0.0 ppm. No soil analytical samples were collected; however, groundwater samples were collected from each soil boring at 17 feet bgs. Groundwater samples were analyzed for BTEX and GRO, but did not exceed laboratory method reporting limits for the parameters tested.