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• • 00 URS. Robert McClellon February 22, 2005 Page 2 of 3 REVISED SCOPE OF WORK In the remediation plan addendum, URS proposed to install a third set of gas-migration monitoring probes and two extraction wells using the construction protocols SJCEHD had previously approved in the work plan dated November 13, 2003, and the work plan addendum dated December 12, 2003. It is our understanding that the following protocols may be changed from those previously approved by SJCEHD. • These probes were constructed where a single probe was installed within each boring with a screened interval from 15 feet below the ground surface (bgs) to 6 feet bgs. The results of the geophysical survey indicate that the landfill at some locations may be as deep 30 feet. It is our understanding that SJCEHD will observe the upcoming field activities and, with their concurrence, allow us to alter the construction of the probes in the field at that time from the protocols described in the above 2003 work plan and work plan addendum. The issues to be considered are screened interval depths and whether single or dual probes are installed within each boring. In addition the following items were discussed: • "Aeronautical stainless steel ball-valve" was specified by SJCEHD in an e-mail message to URS dated May 7, 2004, for installation at each of the gas-migration monitoring probes. It is our understanding that SJCEHD will accept another ball-valve manufacturer with another type of metal (i.e.,brass). • In our work plan dated September 13, 2004, URS proposed that "Following the installation of these gas-migration monitoring probes, landfill gas will be measured within each probe." It was our intent to measure the landfill gases immediately following the installation of the probes. However, we learned that though methane was not found in several probes immediately following installation, it was measured a week there following installation. It is our understanding that SJCEHD preference's is to measure the landfill gases within the probes several days following the probe's installation. SCHEDULE We contacted you on February 15, 2005 to inform SJCEHD that, given weather conditions, we were unable to install the gas-migration monitoring probes and extraction wells on February 16, 2005, and have scheduled our drilling contractor on their next available date of March 24, 2005 to install the probes and extraction wells. KAWprocess\25532\022205.doc