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DATA GAP ASSESSMENT WORK PLAN AND PATH TO CLOSURE REVIEW Chase Chevrolet, 424 N. Van Buren Street Proposed Scope of Work January 2, 2018 a minimum) to avoid damaging subsurface utility lines that could not be identified using conventional methods. 4.4 SOIL BORING ADVANCEMENT A California C-57 licensed driller will be contracted to advance the boreholes for SB-2 and SB-3 using dual-walled direct push drilling equipment. The boreholes will be advanced at least five feet past first water, anticipated to be approximately 15 to 20 feet bgs. After the collection of soil and grab groundwater samples are complete, the boreholes will be properly destroyed by introducing neat cement grout through a tremie pipe and completing at the surface with concrete dyed to match the existing grade. 4.5 SOIL VAPOR WELL INSTALLATION Soil vapor probes SV-1, SV-2, and SV-3 (locations shown on Figure 2) will be installed using a 4- inch diameter hand auger in accordance with procedures described in Appendix E of this work plan. The hand augers will be advanced within the retail space on the north side of the parking garage. At this time, the floor on the retail space is still dirt, so sawcutting will not be needed. Hand auger activities will be performed under the supervision of a California Professional Geologist. Detailed field records of all activities will be recorded by Stantec field personnel including site conditions, names of field personnel, pertinent dates and times, etc. The boreholes for the vapor wells will be advanced using a 6-inch diameter hand auger to a depth of approximately 6 feet bgs. The vapor well implant will be set at a depth of approximately 5.50 feet bgs in the middle of an approximately 1-foot thick filter pack emplaced at the bottom of the borehole. The vapor probe implant will be attached to a 5.75-foot length of 1/4-inch diameter Tygon or Nylaflow® tubing and a Swagelok® type valve will be attached at the opposite end. A small diameter well box will be set in concrete on the unpaved surface within the vacant retail space. Well construction details will be recorded onto a well construction field log. Upon completion of the well installation, the well will be allowed to equilibrate a minimum of 48 hours before soil vapor samples are collected. 4.6 SOIL SAMPLE COLLECTION AND ANALYSIS Soil samples from the proposed soil borings will be collected for examination of soil stratigraphy, qualitative analysis for the presence of residual hydrocarbons (i.e. field screened using a photoionization detector [PID]), and laboratory analysis. Soils encountered within the borehole will be described in accordance with the Unified Soil Classification System (USCS) under the direction of a California Professional Geologist. Soil samples will be collected at a depth of 5 feet bgs using an AMS hand auger core sampler. The hand auger used is specifically designed to collect relatively undisturbed soil samples by inserting a clean stainless steel or brass soil sample sleeve in the bucket of the auger. The soil sample sleeve is filled as the hand auger is Stantec bm \\us1312- f02 \ workgroup\ 1857 \active\ 185703766 \ 05_report_deliv \ deliverable \ work_plan \ 185703766_20180102_424_van_buren_work_plan_final.docx 4.2