ARCHIVED REPORTS_XR0009698 - Laserfiche WebLink

Home Browse Search

-� Vapor Extraction Test Report Former Thrifty Oil Service Station # 172 September 14, 1995 • During the constant-flow-rate test from Test Well VW-B, a vacuum level of 16 in. HIO == was measured in the extraction well while extracting vapors at a flow rate of approximately 17.1 scfm Vacuum responses ranging from 0 02 to 0.17 in. HIO were detected in Observation Wells VW-A, VW-C, MW-1, MW-3, MW-4, and MW-g. These observation wells are located at distances ranging from 16 to 97 feet from the test well. • During the constant-flow-rate test from Test Well VW-C, a vacuum Ievel of 5 in. H20 was measured m the extraction well while extracting vapors at a flow rate of approximately 16.3 scfm. Vacuum responses ranging from 0.05 to 0.25 in. HIO were detected in Observation Wells VW-A, VW-B, MW-1, MW-3, MW-4, and MW-g. These observation wells are located at distances ranging from 27 to 67 feet from the test well. Refer to Table 1 for a summary of the field observation data from the constant-flowrate tests and Figure I for the relative well locations. 4.2 SOEL PERMEABILITY TO AIR Estimates of soil transrtussibility to air (kh/µ) and radii of influence can normally be calculated • by applying pairs of vacuum and distance data obtained in the field to the Darcy solution if the data meets the following criteria: I. The distances of the two observation wells from the test wells should differ by a muiimum of 10%. 2. The difference in vacuum pressures between the two observation wells should be at least 0 3 in. HIO, and the two observation well pressures should be non-zero. Since the data obta;ned from observation well pairs during vapor extraction testing did not meet the above criteria, soil transmissibility(kh/µ)and permeability(k) to air were calculated by using the extraction well data as one of the well data sets for each observation well pair. This method gives valid well pair data that meets the Darcy solution criteria. The following average transmissibility and permeability to air values were calculated from the steady-state data using the Darcy solution presented m Appendix D. The individual calculated well pair values are reported at the end of Appendix D. Test Well VW-A (screened 5 to 35 feet below grade): • Soil transmissibility to air value (kh/µ): 11,032 d-ft/cp • Vertical extraction interval (h): 35 feet • Sod permeability to air (k): 5.67 darcy . - 3