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Martinez, Genesis [EHD] From: ehsitemitigation [EHD] Sent: Thursday, May 19, 2022 5:20 PM To: Gregory Gibson;Andrew Francis; ggebhardt@ci.lathrop.ca.us Cc: Eddy Teasdale; rodb@bradleyandsonsdrilling.com; Shih, Steven [EHD] Subject: RE: Lathrop Test Well Permit Attachments: 20220519171555503.pdf Gregory, Glenn,Andrew: The EHD has reviewed your work plan to install 3 nested monitoring wells in one 12-inch boring,for the purpose of eventually installing an Aquifer Recharge Well (ASR)well to inject water into the groundwater aquifer. The EHD has quite a few concerns regarding these wells that need to be addressed before EHD can move on to approving it: 1) Please provide document from State Water Resources Control Board which has authority over any ASR projects, that they have no objection to installing these monitoring wells for the purpose of future ASR 2) EHD has concern with location of the monitoring wells if they're too close (10', 10 yards?)to the future ASR well. When monitoring wells are to be destroyed, cement grout will have to be placed/pumped into the well casings and the gravel/sand packs under possibly tremendous pressure. Given enough pressure the grout may have an adverse effect on any nearby wells. Please discuss how to mitigate this possibility(i.e. further distance between the MW and the ASR well?) 3) EHD requires Stove Pipe be installed instead of a traffic box 4) Annular space requires 2 inches width thickness (SJC Well Standards 4.7.4) around each well casing. Please discuss the method you plan to use to ensure that requirement is met, especially when three 2-inch well casings are being installed inside a 12-inch boring to 800 feet. Will centralizers be used? What kind of centralizers, etc. 5) While EHD understands that the well design on Figure 2 is for"permitting and conceptual purposes only", please provide a corresponding lithological profile and discuss how the design can protect against potential migration of contaminants between lithological lavers, especially when the two proposed filter packs seem to be 120' and 160' in length. 6) Grain-size of the filter pack shall be matched to the slot size of the well screen (SJC Well Standards Section 13.10.2). Please discuss. 7) Filter pack material shall be placed in the well boring by use of a tremmie pipe or equivalent (Section 13.10.6). Please discuss. 8) Strongly recommend surge blocking the well before placing the transition seal or the annular seal (Section 13.10.7). If surge blocking is not to be done, please discuss how to avoid having the sand settle and creating bridging after the transition seal and annular seal are placed 9) There is no discussion of the grout materials for the annular(sanitary)seal in the work plan. Sealing material shall consist of neat Cement, Bentonite neat cement grout, or Bentonite clay(Section 13.12.3). Please discuss. 10) EHD had experienced problems in the past destroying nested wells,to that point that many had to be destroyed by detonation. Provide to EHD a proposal how these nested wells are be destroyed when they are no longer in service,which include both the well casings as well as the filter packs,that will meet SJC Well Standards for monitoring wells. (i.e. pressure grout may not be the answer as you would have to fill 120 to 150 feet of void space of the filter packs from what looks to be about a 10'section of screen, and against whatever head pressure at that depth.) Please discuss. 11) Please be aware that grout must be delivered by tremmie pipe down to the bottom of the well, and from there on up to the top (Section 13.17.8). 12) Please have Ron Bradley the C57 fill out the bottom of the LCD (see attached) authorizing Andrew to sign in place of him on the well permit application (since Andrew had already signed on the permit application.) 1