CORRESPONDENCE_2008 (1/08 TO 6/08)

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Is .0tL 0 Natalia Subbotnikova [EH] From: Michael Carroll [mcarroll@sjgov.org] Sent: Wednesday, April 09, 2008 3:35 PM To: Robert McClellon [EH] Cc: Natalia Subbotnikova [EH]; Luis Gardea; Joyesh Chandra Subject: Adjustment of migration monitoring well design, Corral Hollow Landfill Attachments: CH-TripleHDPE SoilGasWell Figure 1.pdf Good afternoon Robert, Page 1 of 1 This email confirms a voice mail left earlier, regarding the adjustment of the design of replacement perimeter monitoring well at Corral Hollow Landfill. We extended the perforated pipe through each collection (rock) section, whereas the earlier design called for the perforations to extend only into the top of the rock sections. While we believe that collection from the top of the rock section would provide a representative sample of the gas within the rock and in the soil adjacent to the rock, we wanted to remove that question fr6m any future reviewer. I also increased the depth of the well by one foot, from 69 to 70 ft deep. Other than that, the other features of the well remain the same. We understand that we may need to adjust the collection sections to avoid blocking any high - permeability soil lenses we may find while drilling, so the locations of the rock and bentonite are always tentative (you see a note on the drawings regarding this). However, we are not aware of any such lenses at Corral Hollow, and intend to install the bentonite sections just as designed. This well design is a test of the use of the HDPE pipe for use in the wells to be installed in the larger migration monitoring well project at North County and Foothill landfill. We will need the lower probes to extend to the bottom of the well in compliance with Title 27 Section 20925 c 1 C. Regards, W. Michael Carroll, PE Senior Civil Engineer, Solid Waste Division 1810 E. Hazelton Ave. Stockton, CA 95205 Voice: 209-468-8504 Fax: 209-468-3078 4/9/2008