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PRE-TANK REPLACEMENT Site Assessment Work Plan 4315 Waterloo Road Stockton, CA. Aegis Project No. 89-047 Page 11 All work described herein will be completed according to the health and safety procedures outlined in the site health and safety plan included in Appendix A. A copy of the health and safety plan will be available on site during all field operations. 4.0 METHODS 4.1 Soil Sampling Soil borings and soil sampling will be performed under the direction of a State of California registered civil engineer. The soil borings will be advanced to a depth of approximately five below grade by using a hand auger. The soil borings will be advanced, below five feet to final depth, using a truck-mounted hollow-stem auger drilling rig. To reduce the possibility of cross-contamination between boreholes, all downhole drilling equipment will be steamed cleaned between each boring. To reduce cross-contamination between samples, the split- barrel sampler will be washed in a tri-sodium phosphate solution and double-rinsed between each sampling event. Soil sampling will be done in accordance with ASTM 1586-84. Using this procedure, a two-inch O.D. split-barrel sampler or a two-inch I.D. California-type sampler is driven into the soil by a 140-pound weight falling 30 inches. After an initial set of 6 inches, the number of blows required to drive the sampler an additional 12 inches is known as penetration resistance, or the "N" value. The N value is used as an empirical measure of the relative density of cohesionless soils and the consistency of cohesive soils. Upon recovery, a portion of the soil sample will be placed into a glass jar and sealed for later screening with a PID/OVA. Another portion of the soil sample will be used for classification and description. That part of the soil sample collected in a brass tube within the California-type sampler will be stored at approximately 4° C for transport to the laboratory. 4.2 Soil Classification As the samples are obtained in the field, they are classified in accordance with the Unified Soil Classification System (USCS). Representative portions of the samples are then returned to the laboratory for further examination and for verification of the field classification. Logs of the borings indicating the depth and iden- tification of soil types, the N value, and pertinent information regarding the method of maintaining and advancing the borehole are also made.