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15634 Steinegul, Escalon Page 2 • Analytical results of the soil sample taken at 90.5 feet below surface grade (bsg) during the installation of MW-2 were 0.017 parts per million (ppm), 0.020 ppm, <0.005 ppm, and 0.166 ppm of BTEX, respectively. Analytical results of the soil sample taken at 100 feet bsg from Boring k2 (B2) were non-deters at 1 ppm TPH-g, and non-detect at 0.005 ppm BTEX. MW-2 is located approximately 60 feet west of B-2. Therefore, the vertical extent of the contamination in the soil at the site has not been defined. PHS/EHD recommends additional work to define the vertical extent of the contamination. • Analytical results of the water sample from MW-4 were 1,900 ppb of TPH-g, and 33 ppb, 3.8 ppb, <0.3 ppb, and 54 ppb of BTEX, respectively, and 300 ppb of MTBE. MW-4 is located approximately 60 feet west of former UST area. The groundwater elevation data indicates that groundwater flow is east southeast as stated in the report. PHS/EHD agrees with BSK that additional monitoring wells are required to define the west, south, and east extent of the plume of contaminated groundwater. PHS/EHD recommends conducting one more round of quarterly sampling before installing additional monitoring wells. • Pursuant to California Code of Regulation, Title 23, Division 3, Chapter 16,Article 5, a report of the results of the analysis of ground water samples from the monitoring wells should be submitted to PHS/EHD every three months or less. The monitoring wells on site were last sampled February 5, 1999. The next round of quarterly monitoring should occur no later than June 28, 1999. Submit report of the monitoring event by August 10, 1999. Donna Heran, REHS, Director Environmental Health Division Jeffrey Wong, REHS Margare�REHS LOP/Site Mitigation Unit IV Supervisor C: CRWQCB, Central Valley Region-Mark List C: BSK&Associates-John C. Pfeiffer