Laserfiche WebLink
' DRAFT <br /> ' • Equilibrium partitioning occurs between dissolved chemicals in groundwater and <br /> chemical vapors at the air-water interface. <br /> • Steady-state vapor- and liquid-phase occurs as diffusion through the capillary fringe, <br /> ' vadose zone, and foundation cracks. <br /> • None of the chemical is lost as it diffuses towards ground surface(that is, no <br /> ' biodegradation). <br /> • Continuous and thorough atmospheric mixing (dispersion) of the emanating vapors <br /> occurs in the receiving air. <br /> 1 <br /> • It is assumed that there is no capillary zone, resulting in conservative estimates of <br /> VOC emissions from groundwater to air. <br /> • The vadose zone was conservatively described using the ASTM default values for <br /> total porosity,water-filled porosity, and air-filled porosity. <br /> • The values for the other variables in the ASTM equations are the ASTM default <br /> values(Table 10). <br /> • Where available, project- and Site-specific parameters were used and are presented in <br /> ' Table 10. <br /> For VOCs in groundwater, indoor and outdoor air concentrations were estimated by <br /> multiplying a groundwater source concentration for each chemical by the corresponding <br /> ' indoor and outdoor volatilization factors, respectively. For VOCs in soil, indoor and <br /> outdoor air concentrations were estimated by multiplying the soil source concentration by <br /> the corresponding indoor or outdoor volatilization factor and dividing the product by the <br /> vadose zone soil moisture to estimate air concentrations from soil VOCs in soil moisture. <br /> 1 SOMA 99-2218 10 12/10/99 <br />