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Page 2 of 2 <br />In fact, reducing the amount of gas needed to clear the probe (by using much smaller tubes to carry the sampled <br />gas) will reduce the potential for the problem brought up by CalRecycle staff — that we do not want to remove <br />so much gas from the soil that we introduce air from the surface, thus diluting the soil gas. <br />Our experience with polyethylene tubing is that they become brittle and break easily and there may not be a way <br />to tell the condition of such plastic tubing once installed within the PVC. <br />However, if the operator wants to install the plastic tubing, they should provide assurance that installing the plastic <br />tubing will not defeat the purpose of gas monitoring and that it will not compromise the integrity of monitoring. <br />I wonder if the experience of CalRecyle staff is gained from PE pipe that is exposed to sunlight. In our case, the <br />tubes will not be exposed to sunlight at all. In our case, the tubes are entirely encased within the existing pipes, <br />and these pipes enclosed within the soil and a protective metal enclosure. <br />We propose polyethylene because it is suitable for the environment in which it will be used, and it is available in <br />colors so we can color -code the tubes (shallow, intermediate deep) and forever avoid confusion as to which <br />tube is to which depth. <br />In addition, the tubes can be easily removed for insertion of television camera. <br />I hope this address any concerns, but if not, please let me know. <br />2/7/2012 <br />