WORK PLANS - Laserfiche WebLink

Home Browse Search

File No. 20-3978-01.WR9 KLEINFELDER December 9, 1996 2.4 Landfill Gas Survey The presence of landfill gas poses a problem to development on or adjacent to the landfill areas. Landfill gas (methane) is explosive and can migrate laterally from landfills over 400 feet depending on soil conditions. Landfill gas is found in landfills that are moist and have a high organic materials content. It is possible that some of the onsite landfills fall into this category. Low cost, temporary gas probes will be driven into each landfill (four probes per landfill) to a depth of approximately 5 to 10 feet below the ground surface (depth will depend upon the resistance offered by the waste in the landfill). The probes will be allowed to equilibrate for a few days and then each probe will be sampled for the presence of methane using a special meter developed for measuring landfill gas (Landtec GA-90). Specifically, measurements will be made for probe pressure, % methane, % oxygen, and % carbon dioxide. Once the measurements are collected, the temporary probes will be removed. 2.5 Groundwater Monitoring Well Installation and Development There are potentially seven individual landfill areas on the site. Three monitoring wells, one up gradient and two down gradient, will be installed at each landfill area. An exception would be if a landfill area is small enough to place only one well down gradient of the landfill. For costing purposes it is assumed that 21 wells will be installed. San Joaquin County Public Health Services Department Environmental Health Division (PHS/EHD) requires the submittal and approval of a boring pen-nit application to drill a boring to groundwater or install a monitoring well. Prior to beginning field activities, Kleinfelder will submit well application permits to PHS/EHD for approval. Underground Service Alert (USA) will also be contacted prior to field mobilization, and a site specific Health and Safety Plan will be completed. The borings will be advanced using a truck-mounted drill rig equipped with 8-inch outer- diameter hollow-stem augers to drill the borings and install the wells. Borings for the wells will be drilled approximately 15 feet below the first encountered groundwater. Depth-to-groundwater is approximately 20 to 27 feet below ground surface. The borings will be sampled at approximately 5 foot intervals for logging the boreholes. While sampling, an experienced geologist will classify the subsurface soil and log the boreholes. The wells will be constructed of Schedule 40, 2-inch diameter PVC blank casing with 20 feet of well screen. Based on previous work at the site the slotted portion of the wells will be 0.020 inches with a RMC #2/12 clean Monterey sand pack. To provide a qualitative indication of possible volatile organic constituents in the breathing zone 'while drilling, a portable photoionization analyzer (PID), will be used to screen the breathing zone around the drill rig. The PID measures total ionizable compounds in parts per million by volume (ppmv) relative to a 100 ppm isobutylene standard. Also, a separate meter will be used to monitor the breathing zone for possible methane or hydrogen sulfide gas and percent oxygen 20-3978-01.WR91MP960143 Page 5 of9 O1996,Kleinfelder, Inc.