ARCHIVED REPORTS_REVISED DRYWELL CLOSURE AND INVESTIGATION WORK PLAN

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NOA Drywell Closure and Investigation Work Plan Page 7 of 16 March 18, 2014 Revised March 20, 2014 soil sampling will be performed at the bottom of the drywells concurrent with overdrilling activities. Two (2) soil samples will be collected from the center of each well between one (1) and two (2) feet below the vertical extent. Well casing extends to 40 feet bgs. However, total drilled well depths are estimated to be approximately fifty (50) feet bgs. Two (2) soil samples are therefore anticipated to be collected at fifty-one (51) to fifty-two (52) feet bgs. A five-foot sampling interval will then be observed in each well until groundwater is encountered at approximately seventy (70) feet bgs. One (1) additional soil sample will be collected from one (1) of the drywells for Replicate Samples Quality Assurance/Quality Control purposes. The total ' number of soil samples collected from the drywells is estimated to be thirteen (13). The drywell and sampling locations are shown on Plates 5 and 6. 4.3 Sampling Equipment and Collection Methods Field exploration will be performed under the supervision of a California Professional Geologist and/or Engineer. A geologist experienced with investigation and remediation of chemical releases at commercial properties would be present during sampling and drilling to perform sample collection, maintain logs of the boring, and make observations of site conditions. Sample analysis will begin within five (5) days of collection; no preservatives are required for the desired analyses. Groundwater and soil samples will be collected by NOA under the supervision and oversight of EHD. ' 4.3.1 Groundwater A disposable bailer will be used to sample groundwater from the drywells. If a separate floating phase is observed while sampling, a sampling device will be utilized that can collect fluid beneath the floating phase. A clean disposable bailer will be lowered into the wells to collect groundwater and will then be emptied into the appropriate sampling bottles as detailed below. The groundwater sampling equipment and collection methods described below for each drywell are listed in sequential sampling order. Two (2) pre-chilled, pre-labeled 40-ml VOA vials with a Teflon septum lid will be filled for volatile organics testing. Two (2) vials should be obtained for one VOA sample. The samples will be preserved by adding hydrochloric acid to a pH of less than 2. The VOA vials will be filled I completely at a rate of less than 100 milliliters per minute to prevent the presence of headspace. The lid with the Teflon septum will then be tightened onto the vial. The vial will then be turned upside down and tapped to check for the presence of air bubbles. If air is present, the sample will be retaken. The sample will be recorded, labeled and stored at a temperature of approximately 4°C in an ice chest for transportation to the analytical laboratory. One (1) pre-labeled, one-liter amber glass bottle with a Teflon septum will be filled for semi- volatile organics testing. Collection methods specified for volatile organics should be followed. The sample will be recorded, labeled and stored at a temperature of approximately 4°C in an ice chest for transportation to the analytical laboratory. 902 Industrial Way•Lodi,CA 95240-209.367.3701 •Fax 209.369.4228 C2014Neil 0.Anderson&Associates,Inc