Laserfiche WebLink
Vapor Transport <br /> From Groundwater <br /> Into Buildings <br /> � a' 21 <br /> of .1 - <br /> .t-�.¢fib� '` Y� 'L ' � -'"s m a •�'sK�'"�,ti`"' a 'e ' _`� w-: c�y 'F6°' � ..`r�xr �m <br /> hE.1 MODq csCR1P-T014, <br /> The groundwater vapor transport model is based on the approach outlined in <br /> American Society of Testing and Materials' (ASTM's) Risk Based Corrective Action <br /> (RBCA) manual (ASTM, 1995) Vapor emissions from dissolved groundwater <br /> contaminants are estimated using a one-dimensional steady-state vapor diffusion <br /> model, where capillary fringe, vadose zone properties, and building foundation <br /> properties are considered in the estimation of diffusion properties <br /> This is basically the same model as the one used in the Tier 1 spreadsheet <br /> and the ASTM RSCA guidance manual to calculate nsk-based screening <br /> levels in groundwater that are protective of indoor inhalation The <br /> enhancements made by the RISC software are twofold (1) multiple sod <br /> horizons may be considered by using the lens and (2) the groundwater <br /> concentration under the house may be predicted using one of the <br /> groundwater models This second option allows clean-up levels to be <br /> calculated for soil or groundwater that are protective of indoor inhalation for a <br /> plume extending downgradient <br /> This model considers the diffusion of vapors from groundwater through the vadose <br /> zone The model ignores chemical degradation in the vadose zone and advection into <br /> the building (pressure-driven flow) Advection is ignored on the assumption that <br /> capillary fringe diffusion resistance dominates the problem With the capillary fringe <br /> dominating transport, the equations for vapor transport into a building reduce to the <br /> ones presented in this appendix Figure E-1 shows the problem geometry <br /> i <br /> E-9 <br />