ARCHIVED REPORTS_2010_22 - Laserfiche WebLink

Home Browse Search

Mr. Robert McClellon December 8, 2010 Page 2 The design and specifications of the new landfill cell are in accordance with United States Environmental Protection Agency (USEPA) Subtitle D regulations and California Code of Regulations (CCR) Title 27 regulations. As part of the expansion, Forward will install new LFG monitoring probes which are proposed to be located between the property boundary and the limit of waste in the new cell. The design and specifications of the new LFG monitoring probes are in accordance with applicable CCR Title 27 regulations detailed below. CCR Title 27 Requirements The scope and requirements for LFG monitoring and control are outlined in the CCR Title 27, Division 2, Chapter 3, Subchapter 4, Article 6. Section 20925 outlines the requirements for the design of the monitoring probes, including the location of the probes with respect to the waste limits, the spacing and depth of the probes, and their configuration relative to the depth of waste. Requirements for LFG monitoring probes include: • Install around the waste footprint but not within the refuse; • Install at or near the disposal site permitted facility boundary; • Install within 1,000 feet of nearest monitoring probe; • Install adjacent to subsurface materials most conducive to gas flow; • Wellbore depth equal to the maximum depth of refuse; • Contain shallow (within 5-10 feet of surface), intermediate (around half the depth of the refuse), and deep (at or near the depth of the waste)monitoring intervals; and • Install above the permanent low seasonal water table, above and below perched ground water, and place adjacent to materials which are most conducive to gas flow. The new LFG monitoring probes have been designed in accordance with the above requirements. There are no requirements in Article 6 pertaining to the setback of LFG monitoring probes from the limit of waste. These new probes are being designed similarly to other existing probes at the Landfill which have been effective in detecting LFG migration. The probe design currently used at the site, an approximately 50-foot setback or less from the waste footprint, has been effective in detecting LFG migration and therefore can be used as a guideline for the placement of the new probes. A probe setback of 50 feet is typical at the site as it allows for traffic flow and equipment operations between the waste limit and the monitoring probes. The Landfill is located in the northern San Joaquin Valley where shallow sediment typically consists of fine-grained clays and silts with interbedded coarser grained sediments deposited in a meandering fluvial environment. A previous geotechnical investigation completed at the Landfill (Geotechnical Investigation Report, Forward Landfill Expansion, San Joaquin County, California, Geologic Associates, revised February 2008) characterized the upper 28 to 40 feet of sediment as highly interbedded sandy silt, clayey silt, silt, and clay. This soil matrix is underlain by a gray-brown interbedded sand, silty sand, and minor clay subunit that extends to approximately 53 to 75 feet below ground surface. The preliminary design of the