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Page 2 of 16 <br /> estimated results?Or in the case of MW-32,the estimated result of 0.6 µg/I of benzene is less than its <br /> ESL, MCL and WQO and thereby doesn't fit the county's definition of contamination or pollution?" <br /> Regarding the six 1-inch-diameter wells (AS-14,AS-15,AS-17,AS-18,AS-20 and AS-21) and Section <br /> 13.17.6: "If the well construction is unknown and/or is located in an area of known or suspected pollution <br /> or contamination,the well shall be destroyed by removing all material within the original borehole <br /> (including the well casing,screen,filter pack, and annular seal);and the created hole filled completely <br /> with appropriate sealing material. " <br /> It appears to me that that section 13.17.6. of the San Joaquin County Well Standards does not apply to <br /> these wells.The use of"and/or" and the fact that the construction details of the wells are known,gives <br /> the County the ability to deem this section not applicable and thereby allow these wells to be pressure <br /> grouted while still remaining in compliance with the County Standards. <br /> I would just like to restate that I am only requesting this because of the unusual circumstances these f- <br /> inch-diameter wells present. I feel that following Mike Infurna's recommendation of using 15-inch augers <br /> to overdrill an 8-inch grout column opens us up to more potential problems. For example, as I understand <br /> it,the theory for advancing the 15-inch augers is to essentially use the 8-inch-diameter column of grout <br /> to guide the augers thereby keeping them centered on the well. Considering that these wells range <br /> between 62 and 105 feet in depth,what happens if the augers wander off the well (which is a reasonable <br /> possibility based on my experience and talking with multiple drilling companies about this)? By the time <br /> we would see evidence of the augers wandering(assuming we do), we would have lost our grout column <br /> guidance and have no assurance that any further drilling would benefit us in destroying the well. Also, <br /> we'd be unable to re-center on the well since augers are at depth and sealing the portion of the well <br /> beneath where the augers have wandered would become significantly more difficult.The only option I <br /> could think of to continue destroying the well would be advancing larger and larger augers which would <br /> require tripping into and out of the boring which in itself is undesirable given that some of these wells <br /> span multiple hydrostratigraphic units. Now granted,this is a worst case scenario but it is both a <br /> possibility and significantly less protective of the County's groundwater than any realistic worst case <br /> scenario I can think of involving pressure grouting.As such, I feel strongly that the pressure grouting <br /> these wells is warranted. <br /> In summary,given that the County Standards as written will allow for the destruction of these 1-inch <br /> wells by pressure grouting and given the problems involved in attempting to destroy the wells by <br /> overdrilling, I respectfully request the county reconsider its position and allow us to pressure grout these <br /> 1-inch-diameter wells. <br /> Thank you, <br /> 0 40thlogo Josh Ewert I Senior Staff Geologist <br /> Geocon Consultants, Inc. <br /> 3160 Gold Valley Drive Suite 800, Rancho Cordova, CA 95742 <br /> Tel 916.852.9118 Fax 916.852.9132 <br /> www.geoconinc.com <br /> — - ------- ------- ^_ <br /> From: Nuel Henderson [EH] [mailto:nhenderson sicehd.com] <br /> Sent: Friday, December 09, 201110:00 AM <br /> To: Josh Ewert <br /> 12/20/2011 <br />