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' 4 John Yoakum [EH] From: John Yoakum [EH] Sent: Thursday, September 05, 2013 11:21 AM To: 'Larry Witwer' Subject: RE:420 W Yosemite - Rainwater car wash Larry, We have found CMT tubing to be almost impossible to remove. It is not plastic, it is more like Teflon. It does not grind up, it stretches, sometimes wrapping itself around the auger. The center boring is too small to put a centering rod larger than about 3/4" into,so following the well boring is very difficult. The tubing comes off a large spool when it is installed,so it does not follow a straight path. The tubing twists, bends and corkscrews. We have tried over-boring the outside of the grout column,with large augers, but with limited success. Putting a 50 grain cord down the middle does not take out all seven chambers, usually you will get the center and one exterior chamber. Using this method,the cord is inserted into the middle chamber and then neat cement its used to fill all seven chambers prior to setting off the charge. This is then followed by over-drilling with large diameter augers. We have seen almost every possible combination for taking these out,except cryogenics,and all have had minimal success. Leaving them in the ground is not an option due to the tendency for the channels to cross-talk and run contamination from one level to another. At depths approaching 200', we have had almost no success on removing these,and have had some augers left in the ground from the attempt. This is not to say how you are to remove these wells, but over-drilling does not work and will not be permitted. Hopefully you can come up with a method that we have not tried that will allow you to remove all the contents of the well. Johnny Yoakum Senior REHS San Joaquin County Environmental Health Department From: Larry Witwer fmailto:larW0bamiadini.com1 Sent: Thursday, September 05, 2013 10:17 AM To: John Yoakum [EH] Subject: RE: 420 W Yosemite - Rainwater car wash John, t