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,1-0d-7997 d-d6Pt l FROM AGE NC 209 956 0700 P. 3 04 April 1997 AGE-NC-95-0112 Page 2 of 5 2 LOGGING Soil was extruded from the remaining brass sleeves and screened for the presence of organic vapor using a photo-ionization detector (PID: Thermo Environmental 580A, 10.0eV, calibrated to isobutylene),and the readings were recorded on the boring logs. Soil was described in accordance with the Unified Soil Classification System(sec Boring Logs,Appendix A). 2.3. SAMPLE ANALYSIS A total of eleven soil samples were analyzed for total petroleum hydrocarbons quantified as gasoline (TPH-g)and volatile aromatic compounds(benzene, toluene,ethylbenzene and xylenes: BTE&X) with methyl tertiary-butyl ether (MTBE) in accordance with EPA methods 8015rn and 8020, respectively. Four soil samples were submitted to Cooper Testing Laboratory in Mountain View for physic al;geotechnical analyses; samples P4-30 and P4-55 were analyzed for organic content_ Samples P4-35 and P4-50 were analyzed for dry weight density and porosity. Due to the nature of the sell types and small sample tube diameter,permeability analysis could not be perforined, 2.4. PETROLEUM HYDROCARBON'S IN SOIL, The estimated mass of petroleum hydrocarbons in soil beneath the former UST location was calculated from data collected prior to and after remediation. Cross section AW was plotted from near MW-5, southwest of the former UST location,to near MW-4, toward the northeast(Figure 2). A generalized stratigraphic cross section was constructed using data from all borings advanced.near the cross-sectional line.Analytical results from soil samples collected prior to remediation were used to estimate the mass of hydrocarbons in soil before initiation of vapor extraction at the site (F igure 3). Analytical results of soil samples collected after remediation was initiated were used to estimated the remaining mass of hydrocarbons in soil at the site(Figure 4). The plume was divided into sections based on analytical results of soil samples. The soil volume and average 1-PH-g concentration for each section was then estimated. A density of 1.83 grams per cubic centimeter or 1399 kilograms per cubic yard of soil was used in calculations(see section 3.3.). The total mass of hydrocarbons was calculated by adding the calculated mass fxom each section.