CORRESPONDENCE_1992-1993 - Laserfiche WebLink

Home Browse Search

San Joaquin C(290ty Proj-^" 939-01.09 March 2, 1992 Page 2 The intermediate level probe at gas wells GW-1, GW-4, and GW-10 were purged and sampled for the ten Air Solid Waste Assessment Test (AirSWAT) compounds. Samples were collected in evacuated Summa polished cannisters and sent to a certified laboratory for gas chromatography/mass spectrometry analysis of trace volatile organic compounds (VOCs). The analytical results will be reported before the next scheduled gas well monitoring in late March. The migrant labor housing west of the landfill was inspected and monitored for landfill methane concentrations, using a Foxboro OVA 128 flame ionization detector (FID). Forty-five housing units were monitored, which included the 25 units closest to the landfill property line. The monitoring effort was focused on points of utility penetrations of floors and walls, in addition to ambient air monitoring. Because of constraints from the site closing time, the 20 additional monitored units were distributed evenly over the property areas further from the landfill. The site operations building was also monitored. No methane was detected in any monitored structure. The instrument detection limit was 0.4 parts per million by volume (ppmv) of methane. Underground vaults and manholes were also monitored for combustible gas concentrations. The recent storms had saturated the ground and flooded many of the vaults, decreasing the probability of detecting landfill gas in exterior areas. No methane was detected in any of the underground structures monitored. From the observations of the monitoring staff and conversations with Mr. Bob Reed of the Housing Authority, the houses appear to be well-isolated from potential gas intrusion. Mr. Reed stated that the soil pads below the units were compacted to 97 percent of maximum Proctor density, to minimize the potential for differential settlement and concrete slab cracking. Two membranes were integrated into the concrete floor slabs, and a passive gas venting system was included below the slabs and in the utility trenches. EMCON staff noted no cracks in the floors, walls, or ceilings of the houses and only very minimal hairline cracking of exterior concrete pavements.