UAR/PROP 65 PRE 2019 - Laserfiche WebLink

Home Browse Search

DU POIlt NOSN�stc E Page Two November 2 , 1988 Job No. 1088-M-5 Soil vapor extraction works on the following principles. Liquid-phase hydrocarbons become adsorbed onto the surface of soil particles in the vadose zone as a result of surface tension. Volatile components of the liquid-phase hydrocarbons vaporize until equilibrium is established in the air space between soil particles. Once equilibrium is established, the thickness of the liquid film on the soil remains constant. To reduce the film thickness, and thus the amount of trapped hydrocarbon liquid, the volatilized hydrocarbon concentration in the air space must be lowered. This can be achieved by circulating fresh air through the soil, i.e. , by soil vapor extraction. Remediation will consist of soil vapor extraction accomplished by applying a constant negative pressure, utilizing a low- vacuum blower, on existing wells located at approximately the center of the subject site. Specific air flow rates, contaminant concentrations, moisture elimination system design, influence zones, and air inlet locations will be determined subsequent to implementation of a pilot program designed to gather parameter information for a period of 30 days. The pilot program will consist of low-vacuum pumping of existing wells, as well as hydrocarbon-vapor concentration sampling at various locations within the contamination zone. During the pilot program, contaminated vapor extracted from wells will be pumped through a carbon canister, if necessary, to reduce contaminant levels to San Joaquin County Air Pollution Control Agency acceptable levels. This is intended as an interim remediation technique to assist in the reduction of hydrocarbon contamination until ground water levels are restored or bioremediation can be initiated. We believe that the existing configuration of monitoring wells will suffice. The system will be designed for 24-hour a day service and will include provisions for monitoring the treated air. Air quality standards specified by the San Joaquin County Air Pollution Control District will be adhered to throughout the remediation operations. We are prepared to initiate the start of work, pending your approval .