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Draft Supplemental Environmental Impact Report Page IV.G-21 • Forward Inc. Landfill 2018 Expansion Project . In addition, the RWQCB will review the updated Joint Technical Document OTD), the leachate ; collection system, and associated monitoring, and could require changes to the planned leachate collection system or monitoring. Implementation of the described protection measures and long-term operations and maintenance procedures would reduce the impact to a less-than-significant level. Impact GA: If not properly managed,the volume of leachate generated from the expansion • areas could result in potential groundwater impacts. • More refuse would be generated by the expanded landfill than would be under the existing landfill operating permit, so that there is a potential for more leachate to be produced over time . given the additional 8.2 million cubic yards (CY)of landfilling covered by the expansion. The • base liner system design would be required to be in compliance with the current WDRs for the existing facilities and in accordance with 27 CCR,Section 20330 requirements for a Class II liner system. • Spacing of LCRS lateral pipes and headers was determined by HELP2 leachate generation modeling performed by GLA and modified by the higher historical indications of leachate volume. Leachate will be collected and discharged to the new onsite leachate ponds that will • replace the old ones. If during the service life of the landfill, the demand on the leachate • impoundment exceeds capacity, Forward would implement an alternative leachate management plan. Leachate in excess of the impoundment's capacity would either be pumped to temporary onsite tanks, trucked for offsite disposal at the City of Stockton Municipal Utility Department wastewater treatment plant, or trucked to another offsite licensed treatment and disposal facility. Leachate stored in the temporary onsite tanks may be released back into the • impoundment at a later date. The following measures are proposed as part of the project: • • The proposed measures to address concerns about additional leachate generation as a result of the expanded landfill will be addressed in the JTD with the presentation of the updated • EPA HELP model results based on the projected volumes of refuse, a historical analyses of actual leachate generation volumes (which were at significantly higher volumes than the model predicted for peak year rainfall) and the description of the leachate collection system designed to meet the maximum probable leachate generated. Engineering control systems (leachate collection system, drainage control, groundwater and gas controls),monitoring • programs, and institutional controls have been presented in the JTD, which has been • reviewed by the RWQCB. Reporting on leachate generation volume and quality is a requirement of the RWQCB-stipulated progress reporting through the various proposed landfilling phases. • • The landfill cell anchor trenches would be elevated 2 to 3 feet above the surrounding land to minimize the possibility of water from major storm events draining into the cells and • adding to the volume of leachate. • Implementation of these procedures would reduce the impact to a less-than-significant level.