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t E � _ Y • LATERAL AND VERTICAL INVESTIGATION OF CONTAMINATION 1 The deep boring is located at VW-7 First the boring will be drilled and the sod sampled every 5 feet The position of this boring is close to the main contamination We will drill until we obtain two consecutive 5 foot sod samples which show non-detectable contamination We plan to use a mobile laboratory during the drilling The laboratory will test for TPH, BTEX and MtBE using EPA 8015M, 8020 The laboratory will retain the samples and ran the Oxygenates test EPA 8260 when they return to the laboratory After we have confirmed that we are at least 10 feet below the contamination the well will be backfilled with bentonite grout to 45 feet We will then place the casing for a vapor Extraction well as shown in Figure 5 of the Work Plan dated August 21, 1998 2 Oxygen Release Agent (ORC) is a possible alternative to clean up this site One of the main reasons the groundwater, at this site, has continued to remain contaminated is that the water level has been rising since January 1997 when it was at 46 feet bgs It is now at 33 feet bgs This rise has caused the water to come into contact with soil contamination The Vapor Extraction system was placed in operation in July 1997 Since that time the water has risen about 8 feet The VES system did not have enough time to clean up the contaminated soil before the water rose The volume above the water table has been diminishing and the VES is still removing 20 pounds of gasoline every day We believe the area from the water table to the surface is much cleaner than it was a year ago The contamination, in the submerged porton of the former vadose zone, will be reduced through natural attenuation However, it may not have enough time to complete this process The recent quarterly monitoring shows that the level of contamination outside the old tank pit has diminished The vapor extraction system is working and when installed the air sparging will continue to decrease the contamination At this time we do not believe it will be cost effective to use ORC at this site There has already been a large amount of money spent to install and operate the Vapor Extraction System Air Sparging and one more vapor extraction well is recommended at this time If there are any questions please contact me at 527-1247 Yours truly, �EREL' S o4nusen RG #6506 - Na C+6� Enclosures 9 Figures 1 Air Operating Permit OrCAuFd�t�` Cc Mr Roger Liston, Darpetro, Inc