ARCHIVED REPORTS_DRYWELL CLOSURE AND INVESTIGATION

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NOA Drywell Closure and Investigation Page 8 of 26 May 30, 2014 4.0 SAMPLING METHODS 4.1 Sampling Objectives The objective of the groundwater and soil sampling below the drywells at the subject property is to confirm the presence or absence of contamination as a result of the industrial use of the drywells. NOA collected the groundwater and soil samples under the supervision of NOA's California Registered Professional Geologist and the San Joaquin County Environmental Health Department. Each drywell was overdrilled, sampled, and grouted separately. The western drywell, DW-1, was overdrilled, sampled and grouted on March 28, 2014. The eastern drywell, DW-2, was overdrilled, sampled, and grouted on April 1, 2014. Samples were picked up by the ' analytical laboratory directly; all laboratory correspondence and results were sent exclusively to EHD who then forwarded all results to NOA. 4.2 Sampling Locations and Depths 4.2.1 Groundwater ' Groundwater samples were collected beneath the two (2) drywells, once drilling and soil sampling activities reached groundwater. For drywell 1, groundwater was first encountered at 1 65.5 feet bgs. The sample to be analyzed for VOCs was collected. In addition, groundwater was measured for pH, temperature, Electrical Conductivity, Dissolved Oxygen, and Total Dissolved Solids. There was not enough groundwater present to collect more samples Therefore, drilling continued until 75 feet bgs when groundwater was again encountered. The remaining groundwater samples were collected. For drywell 2, groundwater was encountered at 58.5 feet bgs. All groundwater samples were collected and groundwater was measured in the field for the previously listed parameters. Six (6) groundwater samples were collected from each of the two (2) drywells. One (1) additional sample split between two (2) identical sampling containers was collected from DW-2 for Replicate Samples Quality Assurance/Quality Control purposes. A total of fourteen (14) groundwater samples were collected for laboratory analysis. The drywell and sampling locations are shown on Plate 6 and Plate 7,Appendix A. 4.2.2 Soil Soil sampling was performed at the bottom of the drywells directly following overdrilling activities. For each drywell, two (2) soil samples were collected from the center of the well between one (1) and two (2) feet below the vertical extent of fifty (50) feet bgs, from fifty-one (51) to fifty-two (52) feet bgs. A five-foot sampling interval was then observed in each well until groundwater was encountered. For drywell 1, groundwater was first encountered at 65.5 feet bgs. Soil samples were collected at fifty-five (55), sixty (60) and sixty-five (65) feet bgs. However, there was not enough groundwater to collect the necessary groundwater samples. Further drilling and soil sampling was required. Soil samples were collected at seventy (70) and seventy-five (75) feet bgs. Groundwater was again encountered at seventy-five (75) feet bgs. One (1) additional soil 902 Industrial Way • Lodi, CA 95240 • 209.367.3701 • Fax 209.333.8303 ©2014 Neil 0.Anderson&Associates,Inc.