ARCHIVED REPORTS_DRYWELL CLOSURE AND INVESTIGATION

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NOA Drywell Closure and Investigation Page 6 of 26 May 30, 2014 3.0 DRYWELL DESTRUCTION 3.1 Pre-Field Activities NOA prepared a Drywell Closure and Investigation Work Plan, dated March 18, 2014 and revised March 20, 2014. This work plan received approval by EHD on March 25, 3014. NOA applied for a Well Destruction permit on March 25, 2014. The permit was approved and issued by EHD on March 26, 2014. The permit is included as Appendix B. Well destruction and sampling activities were originally scheduled with EHD for March 28, 2014. Additional field work was scheduled for April 1, 2014. ' 3.2 Destruction Activities NOA performed well destruction activities under the direct supervision and oversight of Vicki ' McCartney, Senior RENS, with San Joaquin County EHD. The western drywell (DW-1) was over-drilled on March 28, 2014. The destruction of the eastern drywell (DW-2) was performed on April 1, 2014. ' 3.2.1 Well Destruction Methodolaav 3.2.1.1 DW-1 — March 28, 2014. The western drywell (DW-1) was destructed by over-drilling. The drywell consisted of 4 inch i.d. casing in an eight (8) inch diameter gravel pack. Drywell casing extended to forty (40) feet bgs. The drilled depth is estimated to be fifty (50) feet bgs. The well was over-drilled using a hollow stem auger that is twelve (12) inches in diameter to forty-seven (47) feet bgs. The well was then over-drilled using an eight (8) inch hollow stem auger to fifty-one (51) feet bgs. The well was continuously over-drilled until groundwater, at seventy-five (75) feet bgs. Drill cuttings were stored on-site in closed fifty-five (55) gallon drums prior to proper disposal. All material within the original borehole was removed, including the well casing as much as practicable. The i open borehole was then grouted with neat cement (Portland). The grout cement was given sufficient time to settle and set. ' 3.2.1.2 DW-2 —April 1, 2014 The eastern drywell (DW-2) was destructed by over-drilling. The drywell consisted of 4 inch i.d. casing in an eight (8) inch diameter gravel pack. Drywell casing extended to forty (40) feet bgs. The drilled depth is estimated to be fifty (50) feet bgs. The well was over-drilled using a hollow stem auger that is twelve (12) inches in diameter to forty-seven (47) feet bgs. The well was then over-drilled using an eight (8) inch hollow stem auger to fifty-one (51) feet bgs. The well was continuously over-drilled until groundwater, at seventy-five (75) feet bgs. Drill cuttings were stored on-site in closed fifty-five (55) gallon drums prior to proper disposal. All material within the original borehole was removed, including the well casing as much as practicable. The open borehole was then grouted with neat cement (Portland). The grout cement was given sufficient time to settle and set. i t 902 Industrial Way• Lodi, CA 95240 • 209.367.3701 • Fax 209.333.8303 02014 Neil 0.Anderson It Associates, Inc.