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NOW, r� • Retain the services of Advanced Technologies Laboratories (ATL), a California-certified analytical laboratory(ELAP No. 1838)to perform the analyses of soil samples if warranted. • Retain the services of Morrow Surveying, a California-licensed land surveyor, to provide latitude �... and longitude coordinates and top of casing elevations for each of the new monitoring well locations. 3.2 Field Activities 3.2.1 Well Installation Activities V The well installation activities will consist of the advancement of four HSA-drilled soil borings (MW-16 through MW-19) for the purpose of installing groundwater monitoring wells. The proposed NMI boring locations are depicted on Figure 10. Three of the borings will be located downgradient of the former USTs and one will be located upgradient to monitor background concentrations. V Each boring will be advanced to approximately 15 feet below first encountered groundwater for a total depth of approximately 60 feet utilizing a HSA drill rig. Soil samples will be obtained in 6-inch- diameter stainless steel sample tubes at selected depth intervals for logging and screening purposes, and analytical testing where warranted. Logging of each boring will be performed utilizing the Unified Soil Classification System. A California Professional Geologist (PG) will provide office and field direction for the drilling and logging operations. Boring logs depicting the soil conditions encountered will be included in the report. The soil samples will also be field screened with a photo-ionization detector (PID) to assess possible qualitative indicators of volatile organic compounds (VOCs) in the soil samples collected. The PID readings will be recorded on the field boring logs. Each monitoring well will be constructed using 2-inch-diameter Schedule 40 PVC casing. The lower portion of each well will be constructed with a 20-foot section of 0.020-inch slotted PVC well screen casing. A filter pack consisting of Monterey #2/12 silica sand or equivalent will be placed around the screen from the bottom of the boring to approximately one foot above the screen zone. Following introduction of the filter pack material, the wells will be pre-developed by swabbing with a surge block Wad to assist in settlement of the filter pack and to minimize the potential for bridging. A 2-foot-thick transition seal consisting of hydrated bentonite chips will be placed above the filter pack. Above the seal, a mixture of bentonite powder and cement will be placed to within 1 foot of grade level. A traffic-rated well box set in concrete will be used to complete construction. Quality assurance/quality control (QA/QC) procedures will be provided during the field exploration activities. These procedures will include cleansing/rinsing of the sampling equipment between sampling intervals, hot water pressure-washing downhole drilling equipment prior to and between borings, and providing chain-of-custody documentation for each sample transferred to the laboratory. Project No.Stockton Yard,Task Order No.45 -5- Caltrans Contract 03A1368,EA No. 10-ON8300 Project No.S9300-06-45 January 28,2009 NMI