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I ,e I 'W a 0 <br /> .2al 4 California Regional Water Quality Control Board Valley Region <br /> Robert Schneider,Chair 9Central <br /> Winston H.Hickox Gray Davis <br /> Secretary for Sacramento Main Office Governor <br /> Envirownental Internet Address: http://www.swrcb.ca.gov/rwqcb5 <br /> Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000-FAX(916)255-3015 Ho <br /> 14 August 2002 AUG 15 2002 <br /> Mr. Kevin Basso ENVIRONMENT HEALTH <br /> General Manager PERMIT/SERVICES <br /> Forward Inc. <br /> PO Box 6336 <br /> Stockton, CA 95206 <br /> LINER PERFORMANCE APPRAISAL—PERFORMANCE DEMONSTRA TIONFOR A <br /> SINGLE COMPOSITE LINER, FORWARD AND AUSTIN ROAD LANDFILLS, SAN <br /> JOAQUIN COUNTY (Case No. 2209 & 2148) <br /> On 26 March 2001 Central Valley Regional Water Quality Control Board staff(staff)requested that <br /> Forward Inc. provide a demonstration that any future waste containment units fulfill the performance <br /> standards for a Class II landfill. On 21 February 2002 Forward Inc. submitted "Leachate Attenuation <br /> Analyses Prescriptive Clay Liner, Forward Landfill"and on 21 March 2002 staff provided comments <br /> for that document. On 10 July 2002 Forward provided the Performance Demonstration for a Single <br /> Composite Liner that responded to those comments. Staff's comments on the liner performance <br /> demonstration are as follows: <br /> 1. The new document includes a revised Leachate Attenuation Analyses Prescriptive Clay Liner as <br /> an Appendix to the demonstration. This appendix models natural attenuation of VOCs as <br /> leachate passes through the compacted clay liner(CCL). The models used, BIOCHLOR and <br /> BIOSCREEN, simulate the reduction of VOC concentrations by the processes of dispersion, <br /> sorption, and biodegradation. Model inputs include flow rates, chemical retardation factors, and <br /> published natural attenuation rates. The model projects greatly reduced VOC concentrations in <br /> leachate when it exits the CCL. Staff remains skeptical that two feet of clay contain sufficient <br /> nutrients and substrate to support the levels of biodegradation projected by the model. <br /> Additionally, the small amount of clay in a two feet thick CCL may have insufficient sorption <br /> capacity. We believe that although the CCL is engineered to achieve a very low hydraulic <br /> conductivity and thus a long residence time, the mass of clay contained within the two feet thick <br /> CCL is very small and will be the limiting factor that determines how much attenuation can <br /> occur. If peer reviewed research that we are not aware of, supports VOC attenuation in similar <br /> compacted clay, we would reconsider this aspect of your demonstration. Without supporting <br /> documentation, staff must conservatively assume that chemical concentrations in leachate that <br /> exits the CCL will be similar to initial concentrations. Please revise Appendix A to include <br /> average (over the last 5 years) Forward landfill leachate unaffected by attenuation to calculate <br /> concentrations released at the base of the liner and to model the expected impacts to <br /> groundwater. Staff will make decisions based on this worse case assumption; any leachate <br /> California Environmental Protection Agency_ <br /> Q*Recycled Paper <br /> The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. <br /> For a list of simple ways you can reduce demand and cut your energy costs,see our Web-site at http://www.swreb.ca.gov/rwqcb5 <br />