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ATC Associates Inc. r v 1117 Lo e Palm Avenue, Suite 201 v Modesto, California 95351 209-579-2221 ASSOCIATES I N C . fax: 209-579-2225 r � • Zone B: from 35 to 45 feet bgs, and • Zone C: from 65 to 75 feet bgs. r SCOPE OF WORK two Planning and Permit Acquisition Prior to commencement of drilling activities, ATC personnel will conduct a site walk and mark the ground surface for Underground Services Alert (USA). USA will be contacted at least 48 hours prior to any field work to allow time for utility companies to identify any underground lines, pipes, or utilities that may be affected by subsurface investigation activities. The locations 1.0 of the proposed borings will be evaluated with respect to utilities identified by USA and a private utility locating service, if warranted. Following approval of the Workplan, ATC will obtain boring permits from the SJCEHD. Off-site access authorization will be sought for proposed r monitoring wells located off-site to the west. ATC will require authorization from off-site property owners prior to conducting drilling activities. As an alternative, ATC will seek an encroachment permit from the city of Tracy. ,. Groundwater Zone A Delineation r The proposed scope of work described in this workplan is intended to evaluate the lateral and vertical extent of dissolved petroleum hydrocarbons. The lateral extent of the petroleum r hydrocarbon plume in shallow groundwater (zone A) is generally defined to the south in the vicinity of MW2 and MW3, but is not well defined to the north and west. Data collected in 2004 in association with the CPT investigation suggest groundwater is impacted at depths of 41 and 67 r feet bgs below the UST area. \ � 1 -� Existing monitoring wells MW1 through MW8 are screened within shallow groundwater Zone ` A. Three new monitoring wells are proposed to evaluate the lateral extent of shallow groundwater impact. One shallow monitoring well is proposed to be installed off-site to the west across Holly Drive, and two shallow monitoring wells are proposed to be installed in the northern portion of the site—one in the northwestern corner, and the other in the northeastern corner. The three proposed groundwater Zone A monitoring wells will be installed using a hollow stem auger equipped drilling rig. Drilling will be conducted by a State-licensed (C57) drilling company. Continuous soil sampling will be conducted to at least 20 feet bgs. A field geologist r will be present to log drill cuttings. Descriptions of soil types encountered will be recorded on well logs. A minimum of three soil samples will be collected for laboratory analyses from each boring, one one from the highest PID reading above the water,table, one from si to ten feet bgs, and one directly above the capillary fringe. A reasonable eQrt will be made tocollect soil samples representative of the vadose zone. Soil collected within 'the saturated,7one or aquifer may not 6 I 1 j ATC Associates Inc. S:\Environmental\25847.0037\Work Plan additional vert-hor delineationTH2.doc G �