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ATTACHMENT I <br /> Responses to Central Valley Regional Water Quality Control Board <br /> Comments on the Work Plan for the Tracy Service Center Underground Tank <br /> Investigation. <br /> The following responses are provided to comments received from the Central Valley <br /> Regional Water Quality Control Board (June 16, 1987) regarding our work plan. The <br /> Regional Board's comments are duplicated below followed by our responses. <br /> Comment: 1. Has the underground tank in question been removed? If so, was the <br /> surrounding soil contamination delineated and mitigated: If not, <br /> these tasks should be initiated immediately. The work plan does <br /> not discuss this aspect of the project. <br /> Response: 1. The underground tank can be scheduled for removal in October 1987 <br /> pending confirmation by the San Joaquin Local Health District. <br /> Comment: 2. A report and proposal for specific well locations should be <br /> prepared after Phase I soil gas work and submitted for regulatory <br /> concurrence. Phase II work should not be initiated until approval <br /> is received. <br /> Response: 2. The report and proposed well locations are included as part of this <br /> submittal . Phase II work will not be initiated until approval is <br /> received from the San Joaquin Local Health District. <br /> Comment: 3. Although two-inch wells are acceptable, four-inch wells have the <br /> advantages of better development, easier purging and sampling, are <br /> much more useful for aquifer testing, can possibly be used for <br /> extraction/recovery wells, and can be installed using the same <br /> drilling technique. I recommend that PGandE consider installing <br /> four-inch monitoring wells on-site. <br /> Response: 3. PGandE prefers to install two-inch wells with the understanding <br /> that we may need to install larger diameter wells if <br /> extraction/recovery wells are necessary. Some of the advantages of <br /> two-inch wells are that they take less time to recover after <br /> purging (particularly in clayey soils which are present at the <br /> service center) , less soil is removed from the ground during <br /> installation (larger augers must be used to install four-inch <br /> wells) and much less water must be removed during purging and <br /> development. <br />