COMPLIANCE INFO_JTD 9/3/2025 - Laserfiche WebLink

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INFORMATION SHEET ORDER NO. R5-2015-0058 SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS FOOTHILL SANITARY LANDFILL, INC. FOOTHILL LANDFILL SAN JOAQUIN COUNTY Background The Foothill Landfill is an active, Class III, municipal solid waste (MSW) landfill on North Waverly Road approximately 1.7 miles south of North Shelton Road in San Joaquin County. The landfill has been in operation since 1965, accepting household, commercial, industrial, and agricultural wastes from the City of Stockton and surrounding areas. Approximately 600 tons per day (210,000 tons per year) of wastes were discharged to the landfill in 2014. The landfill consists of two classified MSW landfill units under Title 27 regulations, including Landfill 1 (LF-1) and Landfill 2 (LF-2). LF-1 consists of a single, 80-acre, unlined module referred to as “Module I” that no longer accepts wastes. LF-1 was partially closed in 2006 with an ET cover on its top deck. LF-2 is a Subtitle D compositely-lined, expansion landfill being constructed in phases around LF-1. At projected landfill closure in the year 2082, LF-2 will consist of 10 Subtitle D compositely-lined waste disposal modules encircling and partially overlapping LF-1. See WDR Attachment F: Conceptual Landfill Development Plan. The first LF-2 module, Module 1 (M-1), was constructed immediately south of LF-1. The first phase of the next LF-2 module, M-2, will be constructed in 2015. Other onsite facilities include landfill-associated controls and monitoring systems (e.g., leachate, landfill gas, surface water, groundwater); an onsite borrow area; storm water retention basins/ponds; landfill access roads, maintenance buildings, a scale house; a landfill gas-to-energy plant; and various other landfill-related facilities. Geology The site is underlain by Laguna alluvial deposits and cemented to partially-cemented Mehrten deposits. Laguna soils generally consist of silty sand, clayey silt, and silty clay to approximately 10 feet bgs. Underlying Mehrten deposits generally include clay/claystone, silt/siltstone, sand/sandstone, and conglomerates. In-place hydraulic conductivities generally range from 1 x 10-3 cm/sec (sand/sandstone) to 1 x 10-7 cm/sec (clay/claystone). Groundwater First encountered groundwater at the site occurs at about 200 to 300 feet below ground surface (bgs) in Mehrten sands. The average groundwater elevation at the site is about 45 feet MSL. The uppermost aquifer occurs in Mehrten alluvium (e.g., sandy gravel) with an overall permeability of about 9 x 10–3 cm/sec. The groundwater gradient is typically about 0.0025 ft/ft toward the southeast. There are currently six groundwater monitoring wells at the site, including one background well (MW-4), two side gradient wells (MW-1A, and MW-3), and three down gradient wells (MW-2R, MW-5, and MW-6). MW-2R and MW-3 are Point of Compliance wells for LF-2 (Module 1) and LF-1, respectively, while MW-5 (installed in 2010) and MW-6 (installed in 2015) contiguously monitor both landfill units along the southern site