Remedial Investigation/recommended action-1995

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� � Sailors World, Inc. Summit Project No. 922030 � October 5, 1995 Page 6 � concentrator and transferred directly into the gas chromatograph column via a heated transfer line for chromatographic sepazation. BTEX and GRO standards were analyzed daily to generate � -response factors for each analyte. Blank samples were analyzed for approximately 10 percent of the field samples. Concentrations of benzene above the Minnesota Department of Health Risk Limit (HRI.) of 10 parts per billion (ppb) were detected at P-3 (829 ppb) and P-4 (224 ppb). Results of the chemical analysis of groundwater samples collected during this phase of the �� project are presented in Table 2. In June 1995, water samples were collected at Geoprobe� test probe locations, the Sailors World water supply well, and Lake Minnetonka. Seven groundwater samples and one soil sample were collected at test probe locations P-9 through P-15, and were analyzed on site for BTEX, GRO, � 1,2,4-TMB and 1,3,5-TMB utilizing the analytical capabilities of the Geoprobe�. Two of these groundwater samples were split and sent to an independent laboratory for analysis of BTEX, M'TBE, and GRO. Results indicated benzene concentrations exceed the HRL at P-14 (205 ppb) � and at the off-site probe location, P-12 (15 ppb). Concentrations of BTEX, NITBE, GRO, 1,3,5- TMB and 1,2,4-TMB were not detected at P-9, P-10, P-11, or P-13. Low concentrations of benzene (3.3 ppb) were detected near the former UST basin at P-15. A slight decrease in � benzene concentrations appears to have occurred during the past year in the area of the probes that were completed near Lake Minnetonka, P-4 and P-14. �� A groundwater sample was also collected at the water supply well in June 1995. Analytical results from samples collected at the water supply well did not indicate the presence of petroleum � hydrocarbons at or above method detection lirnits. A surface water sample was collected from Lake Minnetonka from approximately 20 feet from � shore in June 1995. Concentrations of petroleum hydrocarbons were not detected in the water sample. A summary of results of chemical analysis performed by the Geoprobe� are included in Table 2. Table 3 summarizes analysis completed by the laboratory and the laboratory report is � included in Appendix IV. 3.5 Groundwater Measurements and Hydraulic Properties � Prior to abandonment of the test robes, roundwater levels were measure P g d at test probe locations P-9, P-10, P-11, P-12, and P-14 using an electronic water-level indicator and temporary � 3/a-inch diameter polyvinyl chloride (PVC) pipe and flush-threaded PVC screens. Groundwater measurements were made using a Solinst Model 102 water level indicator. According to the � manufacturer, the accuracy of this instrument is approximately 0.04 foot. However, groundwater measurements were recorded to the neazest 0.01 foot. The water-level indicator was cleaned before and after each measurement with a solution of inethanol and water. The depth to water � within each well was recorded at the time the measurement was completed. Measurements were obtained by lowering the probe of the water level indicator into the PVC pipe until the device indicated that the water surface was encountered. The depth to the water surface was then � i