revised final closure plan - Salinas Valley Solid Waste Authority

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Revised Final Closure Plan July 2010 Crazy Horse Sanitary Landfill -25- 103-97133 Leachate Recirculation - The proposed method for leachate and LFG condensate management at the closed CHLF is recirculation. The storage tanks discussed above would still be available as a backup management system. The location of the proposed recirculation gallery is shown on Figures 4 and 6. Leachate recirculation at the CHLF has been analyzed according to the regulatory and operational restrictions presented in Appendix D1 of this report. That analysis determined that a properly design and constructed recirculation system will achieve the following: • Operate within a Title 27 and Subtitle D compliant base liner and operating LCRS system. • The recirculation system should not generate leachate seeps thereby discharging contaminants to surface run-off. Trenches will be located at least 85 feet from the slope face. • The recirculation system is not expected to cause instability in the waste. • The recirculation system is not expected to generate landfill gas beyond the extraction capacity of the active landfill gas extraction system at the site. • Recirculation will be limited so that it does not generate leachate volumes in exceedance of the hydraulic capacity of the LCRS. Furthermore, the proposed recirculation system is compatible with the Class III liner systems at the CHLF and will not harm public health or the environment. Based on the evaluations presented in Appendix D1, the following design criteria are recommended for leachate and LFG condensate recirculation at the CHLF: • Locate recirculation trenches a minimum of 85-feet from any slope face. • Trenches shall be placed towards the downslope end of the topdeck to accommodate surface water drainage with accelerated differential settlement in the recirculation area. • The maximum application rate should be no more than 6,100 gpd or 35 gpd/ft for the proposed 174-foot horizontal trench. • The trench should have a total depth of at least 5 feet with shredded tire particles at least 2 feet thick and 3 feet wide. They should also be preferentially level to evenly distribute liquids. The tire particles shall be covered with 3 feet of compacted soil. Leachate generation should decrease during the postclosure period as the final cover system will significantly reduce rainfall infiltration and the waste mass stabilizes. The Environmental Protection Agency (EPA) evaluated containment performance for numerous landfills throughout the United States (EPA, 2002) and found that following landfill closure with a low-permeability cover, leachate generation rates typically decrease by 90 percent within the first 2 to 4 years and then decrease to near zero within 10 years. The National Research Council (NRC) reported leachate generation decreases to 1 percent of the annual precipitation 10 years after closure with a composite final cover (NRC, 2007). Golder Associates
Revised Final Closure Plan July 2010 Crazy Horse Sanitary Landfill -26- 103-97133 If recirculation were unavailable, the SVSWA would be able to store the quantities collected (approximately 33,000 gallons from October to March of an average year) in the existing onsite storage tanks if leachate generation rates decrease to 10-percent of current rates. Consistent with 27 CCR 20340 and WDR Order No. R3-2007-0003, the LCRS will be monitored by periodic observation and sampling of collected leachate. Annual LCRS testing will consist of visually monitoring the physical condition of the aboveground components and determining that the system is operating properly. As with current monitoring procedures, the LCRS will be tested annually for biofouling using a typical testing procedure of injecting fixed volumes of water into the LCRS clean-outs and comparing to the corresponding LCRS discharge volume. The results will be submitted to the RWQCB. As required by Monitoring and Reporting Program, included in the current WDR Order, leachate monitoring and inspection results are submitted to the RWQCB as part of the semi-annual monitoring report. If no leachate has been detected or pumped during the reporting period, a statement to that effect will be submitted. 2.17 Groundwater Monitoring System 27 CCR 20385 and 20415 Details on the function of the existing groundwater monitoring system were discussed in Section 6.3.1 of the JTD (Vol. 1). The current monitoring system as described in MRP R3-2007-0003 (Appendix A) will continue to be used in the post closure period. No additional monitoring wells are proposed for installation during closure activities. The objectives of the water quality monitoring system for the landfill are to: • Characterize background groundwater quality. • Detect changes in water quality that may result from changes in recharge, possible landfill leakage or other landfill-related factors before such changes affect off-site water quality. • Monitor groundwater elevations and gradients around the landfill. • Fulfill RWQCB WDRs for groundwater monitoring. • Monitor the effectiveness of the selected corrective action alternatives. Geologic and hydrogeologic investigations at the site indicate that groundwater beneath the site occurs within the alluvium, Aromas Sand, Purisma Formation, and the granitic bedrock that underlies the sedimentary units. Groundwater generally flows to the southwest. The groundwater wells that are part of the Detection Monitoring Plan (DMP) network are positioned to provide upgradient (background) and downgradient (point of compliance) water quality monitoring and to better define the occurrence and flow direction of groundwater within the vicinity of the facility. The groundwater DMP system consists of the following wells: • Aromas Sand Aquifer: A-1, A-10, A-14, A-29, A-30, A-31, A-53, A-54, A-55, A-56, A-57, A-58, A-59, and A-60. • Granitic Aquifer: P-4 and A-61. • Purisma Formation Aquifer: P-3, P-7, P-8, P-9, P-10, P-15, and P-16. Golder Associates
Page 1 and 2: REVISED FINAL CLOSURE PLAN (2010) C
Page 3 and 4: Revised Final Closure Plan July 201
Page 31: Revised Final Closure Plan July 201
Page 41 and 42: TABLES Table 1 - CalRecycles Final
Page 43 and 44: Initial Closure Final Cover Phase I
Page 45 and 46: This figure was originally produced
Page 47 and 48: CRAZY HORSE CANYON ROAD CRAZY HORSE
Page 49 and 50: A - 1 - - TYPICAL ARRAY SECTION LEG
Page 51 and 52: ID Task Name Duration Start Finish
Page 53 and 54: LEGEND NOTES REVISED FINAL CLOSURE
Page 55 and 56: LEGEND A-55 SW-1 NOTES REVISED FINA
Page 57 and 58: LEGEND E A-15 NOTES REVISED FINAL C
Page 59 and 60: NE SW A 4 12 LANDFILL CROSS SECTION
Page 61 and 62: LEGEND NOTES J 14 14 OVERSIDE DRAIN
Page 63 and 64: 1 16 16 2B 16 16 2A 16 16 U 4 16 MA
Page 65: V 18 18 NOTES V 18 18 MODULE 1 FINA

revised final closure plan - Salinas Valley Solid Waste Authority

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