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' jjjr r- Mr. Jim Barton RWQCB March 29, 2013 Page 7 Direct Push Drilling and Abandonment Borings will be advanced using direct push method. Prior to advancing the boring, and after utility clearance, the location will be hand cleared to a minimum of.3 to 5 feet bgs, depending on purpose. Borings used for the collection of a 5 foot soil gas sample will only be hand cleared to 3 feet to allow for a minimum 2-foot of undisturbed soil above the sample depth prior to sample collection. All other drilling locations will be hand cleared to 5 feet bgs. During boring advancement, drilling information will be recorded in the-field notes and on boring logs. Soil types encountered during borehole advancement will be logged consistent with the Unified Soil Classification System. Where soil and groundwater samples are to be collected, borings will be continuously cored and captured in clear acetate liners. Upon completion, each boring will be .backfilled to ground surface using a. 5 percent bentonite grout (consisting of 5 pounds of powdered non-beneficiated bentonite mixed with 10 gallons of potable water and one 94-pound sack of Type II Portland cement). Boring abandonment information will be recorded in the field notes. Abandonment will be conducted in accordance with all SJCEHD regulations. Soil Vapor Sampling Soil vapor samples will be collected from the approximate depths listed in Table 1. Samples will be collected in SUMMA canisters through steel probes following guidelines published in Advisory-Active Soil Gas Investigations (California .Environmental Protection Agency, 2010). After drilling to near sample depth, probes will be placed by pounding the sample rod with a pneumatic hammer at the surface to set the probe depth. Soil vapor sampling information will be recorded in the field notes. The steps for this procedure are described in the following section. Soil Vapor Sampling Procedures Sample T The "Sample T" is mentioned multiple times in the following procedure. This device controls soil gas flow while purging and sampling. 1) The Sample T is comprised of stainless steel tubing, a 4-way fitting, two vacuum gauges, and four valves, configured as follows: a) Arm 1 attaches the 4-way fitting to the vacuum pump inlet. A ball valve, to isolate the pump from the Sample T, and a vacuum gauge are plumbed into the line,which now forms the base of the Sample T. b) Arms 2, 3, and 4 are identical and interchangeable, each consisting of a ball valve attached to the 4-way fitting. The other (available) side of each ball valve has a male screw-type connector. •S