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Page 3 of 4 <br /> ESL for benzene is extremely low, 0.084 ug/m3). However, benzene was detected in the <br /> indoor air samples at concentrations just above the concentrations detected in the ambient <br /> air samples. Benzene was detected in ambient air samples at concentrations between 0.45 <br /> and 0.48 ug/m3 and benzene was detected in indoor air samples at concentrations of 0.57 <br /> and 0.65 ug/m3 <br /> Although the benzene concentrations are above the ESL for benzene in indoor air, the <br /> cancer risk and hazard quotient are not exceeded when using the 0.65 ug/m3 <br /> concentration in an HHRA; I ran an HHRA model using 0.65 ug/m3 benzene and the <br /> cancer risk was calculated at 4.8*10-7 and the hazard quotient was calculated at 1.6*10-2. <br /> Now to answer your questions: <br /> 1. Terra-Petra has a professional engineering license in all the states. See this link for <br /> their qualifications, http://www.terrra-r)etra.com/aualifications <br /> 2. The only mechanical piece of the system is the fan. The Fantech HP 190SL is <br /> specifically designed for residential use and to run quietly. I have been assured by <br /> Terra-Petra that the fan is very quiet. Additionally, Jeff Skelton is familiar with the <br /> type of fan and concurred that it runs quietly. I have left a message with the <br /> manufacturer to try and get the decibel level of the fan. I will contact you when I <br /> hear back from them. <br /> 3. There is no operational manual for the system in general. The mechanical part of <br /> the system is the fan; the only manual I can locate for the fan was included in <br /> Appendix B of the work plan (the installation instruction manual and specification <br /> manual). <br /> 4. 1 don't know the exact reason the pipe along the eastern wall of the crawl space <br /> does not run the entire length. I would presume that it was not necessary to <br /> produce the desired air exchanges in order to create the negative pressure in the <br /> crawl space. The piping and system was designed by a competent professional <br /> engineer with extensive experience in this field and based on his calculations this is <br /> the design that was prepared. I realize I might not have answered your question <br /> very well. If you would like I can contact Terra-Petra and ask them specifically why <br /> that pipe is shorter than the others. <br /> Let me know if you have any other questions or comments. <br /> Thanks, <br /> Brian W. Millman <br /> California Professional Geologist #8574 <br /> Advanced GeoEnvironmental, Inc. <br /> Stockton • Santa Rosa - Monterey - Brea • Spokane - Reno • Dallas <br /> 1-800-511-9300 <br /> bmillman anadvgeoenv.com <br /> www.advgeoemcom <br /> This email/fax message is for the sole use of the intended recipient(s)and may contain confidential and privileged <br /> information.Any unauthorized review,use,disclosure or distribution of this email/fax is prohibited. If you are not the int.r:ded <br /> recipient,please contact the sender by email/fax and destroy all paper and electronic copies of the original message <br /> From: Vicki McCartney [EH1 [mailto:vmccartney@sjcehd.com] <br /> Sent: Wednesday, March 14, 2012 11:23 AM <br /> 3/29/2012 <br />