COMPLIANCE INFO_1994-1996 - Laserfiche WebLink

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City of Stockton - French Camp Landfill TL 394-0028-02 April 28, 1994 Page 3 3.0 FIELD PROCEDURES Field activities are summarized in the following subsections. Standard operating procedures for relevant field activities are described in Attachment A. 3.1 Gas Probe Installation. Twining drilled eight soil borings to depths ranging from 10 to 15 feet BSG using 6-5/8-inch diameter hollow-stem augers. Soil samples were collected at five-foot intervals beginning at five feet BSG for lithologic purposes only. A Twining geologist logged the soils in accordance with the Unified Soil Classification System. Boring logs are present in Attachment B. Drill cuttings were stored on and covered by plastic. Soil disposal is the responsibility of thb client. The soil gas probes (SGPT through SGP8)were constructed of 1-inch diameter schedule 80 polyvinyl chloride well casing and 0.02-inch machine slotted well screen. Casing and well screen were flush threaded. Each gas probe was screened in the lower five feet. Rubber stoppers were placed at the top of the screened section and at the top of the casing. Teflon tubing extends through the rubber stoppers from approximately one foot below the bottom stopper to approximately one foot above the top stopper. Samples are to be obtained through the Teflon tubing. Construction diagrams for the soil gas probes are presented in Attachment C. Coarse-grained sand was placed from the bottom of the boring to approximately two feet above the top of the machine slotted casing. Approximately one foot of bentonite pellets was placed on top of the filter pack, and the remaining annular space was filled with a sand- cement grout containing three to five percent powdered bentonite. The bentonite pellets were hydrated prior to the placement of the grout. Steel standpipes were installed to approximately 1.5 feet above ground surface, secured in place with concrete, and locked. Drilling and probe installation activities were supervised by a Twining geologist. The Twining geologist worked under the direct supervision of a California registered geologist. Ms. Carol Oz of the San Joaquin County Environmental Health Department was on site during grouting activities. 3.2 Soil Gas Monitoring. Following probe installation, soil gas concentrations were measured using a Gastechtor Model No. 1314SMPN calibrated for methane. Sampling procedures consisted of a five minute warm up for the meter and at least two minutes of purge time for each probe.