Laserfiche WebLink
purge volume versus contaminant concentration test should be conducted as <br /> the first soil gas sampling activity at the selected purge test point. The purge <br /> volume test is conducted by collecting and analyzing a sample for target <br /> compounds after the removal of appropriate purge volumes. <br /> 2.3.1 Purge Test Locations: The purge test location should be selected as <br /> near as possible to the anticipated or confirmed contaminant source, <br /> and in an area where soil gas concentrations are expected to be <br /> greatest based on lithology(e.g., coarse-grained sediments). The first <br /> purge test location should be selected through the workplan approval <br /> process or as a field decision in conjunction with Agency staff. <br /> 2.3.2 Purge Volume: The purge volume or"dead space volume"can be <br /> estimated based on a summation of the volume of the sample <br /> container(e.g., glass bulbs), internal volume of tubing used, and <br /> annular space around the probe tip. SummEP canisters, syringe, and <br /> TedlaCm bags are not included in the dead space volume calculation. <br /> The Agency recommends step purge tests of one (1), three (3), and <br /> seven (7) purge volumes be conducted as a means to determine the <br /> purge volume to be applied at all sampling points. <br /> A The appropriate purge volume should be selected based on the <br /> highest concentration for the compound(s) of concern detected <br /> during the step purge tests. The purge volume should be <br /> optimized for the compound(s)of greatest concern in accordance <br /> with Section 2.2 of the ASG 1. <br /> B. If VOCs are not detected in any of the step purge tests, a default of <br /> three(3) purge volumes should be extracted prior to sampling. <br /> C. The step purge tests and purging should be conducted at the <br /> same rate soil gas is to be sampled (see Section 2.5). <br /> D. The purge test data (e.g., calculated purge volume, rate and <br /> duration of each purge step)should be included in the report to <br /> support the purge volume selection. <br /> 2.3.3 Additional Purge Volume Test <br /> A Additional purge volume tests should be performed to ensure <br /> appropriate purge volumes are extracted if: <br /> 1. Widely variable or different site soils are encountered; or <br /> 2. The default purge volume is used and a VOC is newly <br /> detected. <br /> 01/28/2003 -9- <br />