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R604 UPDATE 21 9-1-1993 Sampling Vapor Streams • The vapor samples are obtained by attaching a dedicated air tight . soft polytubing to a sample port on the well side of the orifice plate on the vapor recovery manifold. The tubing is then connected to a tedlar bag placed inside a vacuum sampler. The sample port is then opened and the vacuum placed on the tedlar bag from the sample vessel allows the tedlar bag to fill with the vapor stream from that particular sample port . Once the tedlar bag is full the valve is closed and the vacuum removed from the sample vessel The tedlar bag contains an air tight locking septum valve which is then closed and locked to secure the vapor sample A small dedicated needle attached to a dedicated 1 cc syringe is then inserted through the sample septum into the tedlar bag The 1cc syringe is purged numerous times before falling it with the sample . All but 0 5 cc of the sample is e3ected into the air before anJecting the remaining 0 5 cc syringe sample into the Shimadzu FID-GC (the calibrant in3ection is 0 . 5 cc) Once the chromatogram is recorded, an instrument blank as run prior to the next sample The instrument blank will indicate if residual peaks are being carried onto the next analysis Vacuum influent readings are obtained from the wells by attaching a manometer calibrated an mm water to sample ports at the well heads These readings show the mm water pressure or vacuum that is being created at each well SUMMARY Estimates of petroleum hydrocarbons remaining an the soil after the confirmation soil sampling that occurred on July 20, 21, 22, 1992 was approximately 3027 pounds Soil sample results from the SB4 confirmation sample boring and vapor samples from the vadose zone well P1 have indicated that the former northeastern pump island area and the surrounding area (AREA C) is now remediated of the contaminant The two remaining areas of impacted soil are AREA A -- (SB5) the area beneath the former western pump island and AREA B (SB3 , SB9 and SB11) the area southeast of the former underground storage tanks Vapor extraction has removed the lighter fractions of gasoline range hydrocarbons found in the soil and has greatly reduced the dissolved contaminant found in the ground water and the capillary fringe Of the estimated 3027 pounds that remained an the soil after the July 22, 1992 sampling, 221 out of an estimated 72 pounds have been removed from AREA A (VSR5) and 2872 out of an estimated 2946 . 5 pounds have been removed from AREA B (MWS, VSB3 , VSB9 and VSB11) This indicates that the majority of degraded gasoline range hydrocarbons has been removed from the soil and ground water at this site Dual instruments, GC FID and GC PID, have confirmed that benzene as no longer a component of the vapor streams Monitoring of the ground water indicates that contaminated ground water associated with MW1 and MW5 has been remedaated and meets the Title 22 and DHS standards. Ground water gradients, page 6