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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2009-0049 -2- SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS HARNEY LANE LANDFILL SAN JOAQUIN COUNTY 6. The facility is subject to federal municipal solid waste (MSW) landfill regulations (Title 40, Code of Federal Regulations, Part 258, or "Subtitle D") because it accepted MSW after the effective date of Subtitle D regulations (9 October 1991) and did not qualify for any exemptions. For example, the facility did not qualify for the limited _exemption applicable to facilities that stopped accepting MSW before (and closed within six months after) the applicable federal deadline (9 October 1993), because the landfill did not close until November 1994 (see 40 CFR 258.1(d)). The facility also did not qualify for the small landfill exemption (see 40 CFR 258 (f)(1)) due to its size and evidence of groundwater impacts from the landfill. WASTES AND UNIT CLASSIFICATION 7. The landfill accepted wastes defined as "inert" and "nonhazardous" under Title 27, sections 20230 and 20220, respectively. Septage and other liquid wastes were not accepted at this facility. 8. Approximately 350 tons per day (125,000 tons per year) of waste, including household waste, commercial refuse, construction debris, and agricultural waste, was discharged to the landfill prior to its closure. Waste disposal was by the trench fill method. Approximately 7 million cubic yards of waste are estimated to be in place at the facility. The maximum thicknesses of waste in the landfill units are estimated to be at least 80 feet in LF-1 and 50 feet in LF-2, respectively. 9. Waste was discharged to a series of trenches excavated in an east-west direction. The lowest elevation of waste is unknown, but is estimated to be about 58 feet mean sea level (MSL) based on boring logs for groundwater monitoring wells installed at the site. This elevation corresponds to a depth of about 40 feet below ground surface (bgs). See Finding 23. 10. Both landfill units are existing, reclassified units under Title 27, section 20080(4), since they operated prior to, and closed after, 27 November 1984. Previous WDRs reclassified the landfill to Class III from a previous Subchapter 15 designation. 11. Both landfill units are unlined and neither has a leachate collection system. SITE DESCRIPTION 12. The site is in the Central Valley alluvial plain near the edge of the Sierra Nevada Foothills. The surrounding terrain is relatively flat with an average grade of about one half percent toward the west. Surface elevations within one half mile of the site range from about 95 feet MSL to the east to about 70 feet MSL to the west. 13. Land uses within the landfill vicinity include agriculture, dairies, industrial, and low- density residential development. Other uses in the area include water conveyance, roads, utility easements, and (immediately north of Landfill 2) a migrant labor camp on state-owned land operated by the San Joaquin County Housing.Authority. The migrant labor camp includes unlined ponds used for the treatment and disposal of domestic wastewater from the camp and for the detention of storm water runoff from