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Sarale Farms Page 2 16500 West Clifton Court Road October 30, 2012 Stockton, California 95206 • Use seventy-percent isopropyl alcohol as a leak detector; • Fill each boring by pouring grout made of Type 1111 portland neat cement into the borehole once the soil gas samples have been collected; and • Analyze the soil gas samples for total petroleum hydrocarbons as gasoline by Environmental Protection Agency (EPA) Method TO-3; benzene, toluene, ethylbenzene, and total xylenes (BTEX); methyl tertiary-butyl ether (MTBE), ethyl tertiary-butyl ether (ETBE), tertiary-amyl methyl ether (TAME), di-isopropyl ether (DIPE), and tertiary-butyl alcohol (TBA) by EPA Method TO-15; and isopropyl alcohol by EPA Method 8015M/TO-15. The EHD approves the work plan to collect soil gas samples with the following conditions that are partially based on Advisory—Active Soil Gas Investigations, dated April 2012 published by the California EPA Department of Toxic Substances Control, Los Angeles Regional Water Quality Control Board, and San Francisco Regional Water Quality Control Board: • Allow two hours, instead of twenty minutes, for equilibration to take place after probe installation, and before completing shut-in and leak testing, prior to purging the system and collecting soil gas samples; • Postpone collecting soil gas samples within five days of a significant rainfall event of a half inch or greater and during the passage of a frontal system; • Use of Teflon® tubing is recommended for soil gas sampling and low-density polyethylene tubing is not recommended; • Analyze soil gas samples collected in Tedlar bags within six hours of sample collection; • Detection limits for all chemicals of concern must be equal to or less than the commercial Environmental Screening Levels (ESLs) for soil gas published by the San Francisco Bay Regional Water Quality Control Board and the California Human Health Screening Levels (CHHSLs) published by the California EPA; • Quantify all detections of the leak check compound at or below the reporting limit of the target analytes rather than at an arbitrary detection limit determined by the laboratory, such as 10 micrograms per liter (pg/L). If the laboratory reports the concentration of the leak check compound at greater than or equal to ten times the reporting limit for the target analytes, then corrective action is necessary; • Collect one duplicate soil gas sample; and • If the laboratory uses liquid standards to calibrate the instruments and perform quality control for the soil gas samples, then EPA Methods TO-3 and TO-15 are not appropriate methods to use for soil gas samples. Having received concurrence from the CUF, the EHD directs that the nearby domestic well be sampled and the groundwater analyzed for TPH-g, BTEX, MTBE, ETRE, DIPS, TAME, TBA, 1,2-dichloroethane (1,2-DCA), 1,2-dibromoethane (EDB) and naphthalene. Notify the EHD prior to the domestic well being sampled so that an inspector can be present. Also, at the direction of the CUF, collect soil samples at each borehole and analyze the soil for the same compounds as those listed above for groundwater samples. Compare soil concentrations to ESLs published by the San Francisco Bay Regional Water Quality Control Board for health risks from direct exposure.