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C. Landfill Gas (LFG) This project does not include drilling in refuse; however, landfill gas (LFG) is known to travel through soil under some circumstances. When buried in a landfill, refuse and other organic material produces LFG, which is approximately 50 percent methane by volume and may contain other contaminants. LFG can move through soils, especially through sandy layers that exist at the site. In confined spaces, the lower explosive limit of methane is 10 percent by volume. Methane concentration limits can be detected with the proper test equipment. SWD will ensure the work area methane concentration is below the explosive limit with a GEM 2000 before starting the project. Potential hazards associated with LFG are due to: 1. Oxygen defiance in the landfill gas 2. Combustible characteristics of landfill gas 3. Potential for hydrogen sulfide in LFG Potential hazards include: a. Fire b. Explosion c. Asphyxiation D. Refuse Refuse will not be excavated in this work. Both landfills contain household refuse, demolition debris, tree trimmings, and miscellaneous refuse. To the best knowledge of SWD, hazardous materials have not been disposed at the both sites. Unidentified drums may be present in the refuse at HLSL. If drums are uncovered during drilling, the area will be cordoned off and San Joaquin County Environmental Health (EHD) officers notified. The area shall be flagged and excluded from the work zone until the drum can be characterized. At no time workers shall attempt to remove or handle any such item. 1.04 USE OF SITE A. WORK HOURS The working hours at both sites shall be Monday through Friday from 7:00 am to 5:00 pm excluding any public holidays. "Working" means any time when work is in progress on site. Working hours does not include equipment maintenance. Construction Specifications San Joaquin County Groundwater Monitoring Wells Page 2 of 9 Public Works Dept Revised 11-23-09 Solid Waste Division