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!- <br /> STATE OF CALIFORNIA -Environmental Prot n Agency PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD <br /> CENTRAL VALLEY REGION <br /> 3443 Routier Road, Suite A <br /> Sacramento, CA 95827-3098 <br /> PHONE: 19161 255-3000Cts SEP b AH 11. l51 <br /> FAX: 19161 255-3015 <br /> 13 September 1996 <br /> Mr. Nick Nickerson <br /> Unocal <br /> 2000 Crow Canyon Place, Suite 400 <br /> San Ramon, CA 94583 <br /> LINER DESIGN. 1905 N. BROADWAY, STOCKTON <br /> Thank you for submitting the 10 June Design of a Low-Permeability Liner for the north and south <br /> pond areas at the former PureGro facility. The design plan has been completed with the receipt of <br /> additional information on 26 August and 4 September. <br /> Unocal proposes to excavate the top 14" of soil from each pond area, and then install a geosynthetic <br /> composite liner (GCL), followed by 3" of sand, 9" of aggregate baserock, and finally 4" of <br /> asphaltic concrete. The plan is approved with the following conditions: <br /> 1. The caps shall be designed and constructed to extend laterally a sufficient distance beyond <br /> the boundaries of the affected soils to prevent migration of the water through the affected <br /> soil. <br /> 2. The caps shall be designed, constructed, graded, and maintained to shed rainwater and <br /> prevent ponding. Slope design shall be combined with an effective drainage system to divert <br /> surface drainage away from the covered waste. <br /> 3. Each area to be capped shall be provided with at least two permanent monuments installed by <br /> a hCe..^ed land survey0r or a registered --M! engineer, from which the locations of wastes, <br /> containment structures, and monitoring facilities can be determined throughout the post- <br /> closure maintenance period. <br /> 4. The caps shall be constructed under the direct supervision of a registered civil engineer and <br /> certification shall be provided by that individual on the compliance of the installation with the <br /> design specifications. <br /> 5. A construction certification report shall be submitted to the Board within 90 days following <br /> completion of cap construction. The report shall contain, at a minimum, the following: <br /> a. The results of all the quality assurance and quality control testing (i.e., laboratory and <br /> field permeability results, compaction results, density results, etc.) <br /> b. A graphical depiction of the GCL/compacted subbase layer and the asphaltic concrete <br /> cover layer by means of contour maps, survey data, or point plots. <br />