SITE INFORMATION AND CORRESPONDENCE_2001-CURRENT

Home Browse Search

Page 1 of 15 Nuel Henderson [EH] From: Josh Ewert[ewert@geoconinc.com] Sent: Tuesday, December 13, 2011 7:07 AMyy Nc To: Nuel Henderson [EH] �/ 2wy)� get f Cc: Adrienne Ellsaesser[EH]; Mike Infurna[EH]; 'Jim Brake'; 'Gleason, Nicole' PAW I 1 t L lcK�tts�� Subject: RE: 5400 and 5606 Pacific Avenue, Stockton -Well Destruction Information y /I wlb cit r Good Morning Nuel, Thank you for your response to my requests. I wou/Iinow if you also had any comments regarding wells MW-16 and MW-32. My original comments : "MW-16 and MW-32—You state that these wells as of contamination as shown on AECOM's 9-22- 10 Figures 14 and 15. Would you reconsider this dhat these data points are estimated results?Or in the case of MW-32,the estimated result o .6µg/hof benzene is less than its ESL, MCL and WOO and thereby doesn't fit the county's definition of contamination or pollution?" occas u 4 tow 711117 { Regarding the six 1-inch-diameter wells(AS-14,AS-15,AS-17,AS-18,AS-20 and AS-21) and Section 13.17.6: "If the well construction is unknown and/or is located in an area of known or suspected pollution or contamination,the well shall be destroyed by removing all material within the original borehole (including the well casing, screen, filter pack, and annular seal); and the created hole filled completely with appropriate sealing material. " It appears to me that that section 13.17.6. of the San Joaquin County Well Standards does not apply to these wells.The use of"and/or"and the fact that the construction details of the wells are known, gives the County the ability to deem this section not applicable and thereby allow these wells to be pressure grouted while still remaining in compliance with the County Standards. I would just like to restate that I am only requesting this because of the unusual circumstances these 1-inch- diameter wells present. I feel that following Mike Infurna's recommendation of using 15-inch augers to overdrill an 8-inch grout column opens us up to more potential problems. For example, as I understand it,the theory for advancing the 15-inch augers is to essentially use the 8-inch-diameter column of grout to guide the augers thereby keeping them centered on the well. Considering that these wells range between 62 and 105 feet in depth, what happens if the augers wander off the well (which is a reasonable possibility based on my experience and talking with multiple drilling companies about this)? By the time we would see evidence of the augers wandering(assuming we do),we would have lost our grout column guidance and have no assurance that any further drilling would benefit us in destroying the well.Also,we'd be unable to re-center on the well since augers are at depth and sealing the portion of the well beneath where the augers have wandered would become significantly more difficult.The only option I could think of to continue destroying the well would be advancing larger and larger augers which would require tripping into and out of the boring which in itself is undesirable given that some of these wells span multiple hydrostratigraphic units. Now granted, this is a worst case scenario but it is both a possibility and significantly less protective of the County's groundwater than any realistic worst case scenario I can think of involving pressure grouting.As such, I feel strongly that the pressure grouting these wells is warranted. In summary,given that the County Standards as written will allow for the destruction of these 1-inch wells by pressure grouting and given the problems involved in attempting to destroy the wells by overdrilling, I respectfully request the county reconsider its position and allow us to pressure grout these 1-inch-diameter wells. Thank you, 12/20/2011