SITE INFORMATION AND CORRESPONDENCE FILE 2

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From: Silva, Larry Sent: Thursday, June 19, 2014 9:14 AM To: 'Gabriel Gonzalez [EH]' Cc: Adrienne Ellsaesser [EH] Subject: RE: 620 West Charter Way, Stockton Gabriel, This morning when clearing well MW-5 for over-drill,we located a 4-inch diameter line adjacent to well casing(see attached picture). It is located approximately 1.5 fbg. At this time, I'm uncertain what this line is for. It's not connected to MW-5. It also wasn't picked up in our pre-field subsurface utility clearance activities. Based on how it's located adjacent to MW-5, it appears to have been installed after MW-5 was installed. I'm in the process of gathering more information. We will likely request a variance to destroy MW-5 by pressure grout methods. I will let you know what I find. Thank you, Thank you, Larry From: Silva, Larry Sent: Wednesday, June 18, 2014 5:59 PM To: 'Gabriel Gonzalez [EH]' Subject: RE: 620 West Charter Way, Stockton Hi Gabriel, Due to the subsurface utilities that were identified adjacent to wells MW-3 and MW-7, CRA requested a variance to destroy these wells by pressure grout versus over-drilling methods. Yesterday I discussed with you over-drilling these wells by installing a 5-foot section of casing and drilling through it. The casing would act as a guide so augers do not wander and potentially damage nearby utilities. However, after obtaining additional details this afternoon, I would like to revert to our previous request to not over-drill, but to pressure grout these wells for the following reasons: • Well MW-3 is only 13 inches away from the closest marked utility(electrical). The utility trench may only be 7 inches away. An AT&T line was also marked 2 feet away. Turns out well MW-3 was not installed in the center of well box, but was installed more to the west and is actually closer to marked utilities than thought. • Well MW-7 is located 26 inches away from electrical line.The utility trench may only be 20 inches away. • An distance of approximately 24 inches in diameter will be needed to install casing. Due to the close proximity of the utilities,there is a high likelihood of encountering pea gravel in the utility trenches,which will make installation of casing problematic. o The utilities are located at approximate elevations and distances where area will be exposed and concrete added to secure casing. Consequently, managing pea gravel from caving in the cleared area and managing concrete from traveling through pea gravel will be problematic. This is especially a concern at MW-3 which has several utilities located on either sides. o After concrete dries for a couple days and well is over-drilled,the removal of concrete will require working in tight spaces, which poses potential safety concerns. Also,the concrete will generate additional waste to dispose. • The station is opened 24 hours. The multiple steps involved to install casing will interrupt service station operations. 2