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Workplan for Preliminary Site Assessment(Monitoring Wells) Addendum Flag City New West Station t#1003,6437 W Banner Avenue,Lodi California Page 2 . March 9, 2005 —The SJCEHD issued a letter requesting NWP to perform a subsurface investigation at their site This letter serves as a written directive to NWP to perform their own subsurface investigation June 2005 —Apex submitted a Fund Application to the UST Cleanup Fund on behalf of NWP July 15, 2005 —Apex submitted a workplan titled, Workplan for Preliminary Site Assessment, proposing nine direct push soil borings at the site July 15, 2005 —In a phone conversation, the SJCEHD refected the soil boring workplan and issued a letter requesting a workplan for the )Installation of monitoring wells onsite and an offsite downgradient well within 200-feet of the UST basin (Appendix A) MONITORING WELL INSTALLATIONS Apex proposes to install four monitoring wells onsite (MW-1, MW-2, MW-3A, and MW-3B) and two offsite monitoring wells (MW-4A and MW-4B) Offsite wells MW-4A and MW-4B will be installed in the Microtel parking lot located at 6428 West Banner Street, southeast of the site Proposed onsite well locations are shown on Figure 3 and the offsite wells are shown on Figure 4 • During AGE'S investigation, the water bearing zone from 10 to 30 feet below ground surface (bgs) was designated the First Zone and the water beanng zone from 40 to 50 feet bgs was named the Second Zone Well Construction Details All proposed monitoring wells (MW-1, MW-2, MW-3A, MW-3B, MW-4A, and MW-4B) will be installed utilizing a hollow stem auger ng and completed as 2-inch diameter monitoring wells The proposed wells will be constructed using Schedule 40 PVC and screened with 0 020-inch slotted screen Depth to groundwater is approximately 13 feet-bgs Wells MW-1, MW-2, MW- 3A, and MW-4A will be completed in the First Zone to 25-feet bgs and screened from 5 to 25 feet bgs Wells MW-3B and MW-4B will be installed in the Second Zone to a total depth of 50 feet bgs and screened from 45 to 50 bgs The wells annular space will be backfilled with a Monterey sand pack from total depth to 2-feet above the screened interval, followed by 2-feet of hydrated bentonite and Portland cement to the surface The well casings will be protected with locking expansion caps and traffic-rated vault boxes To prevent cross contamination at well location MW-3 due to its close proximity to the tank basin, well WM-3B will have conductor casing installed from 0- to 42-feet bgs, the middle of the bentonite seal SOIL SAMPLING