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T 1994 As was anticipated from stud of the isoc p y oncentration maps, the lens of contaminated soil was found to extend to the east of the building footprint Study of these January trenches revealed that the coarse aggregate base rock only extended some 2-5 feet east of the building footprint As the gravelly base rock was acting as the reservoir for the diesel, it also served as a marker for the extent of diesel occurrence. A concrete footing, several feet deep, formed a barrier to contaminant migration along the western boundary of the building. The contaminated soil to the south of the building had already been excavated, and the northern limit of migration was defined by the circular "non- detected" line, the outline of a pool of contamination in the porous gravel (Figures 2 and 3). Excavation of the diesel lens was completed in late January and early February of 1994 The procedure for removing the saturated lens was that, first, the surface layer of one or two feet which was not saturated with diesel was scraped off the top of the saturated lens with an excavator and stored in two stockpiles on-site. The layer of contaminant-saturated soil was then removed down to the dark brown native clay unit which acted as the lithologic retardant to any downward migration or percolation of the diesel This excavated soil was stored between two layers of polyethylene film, pending the commencement of remediation procedures. A visual inspection of the excavation and soil samples taken from the bottom of the excavation indicated that the contaminated soil beneath the site had been removed The icrosco is Perspective, Gettin the Small Picture SCS Engineers believed that the technologically most efficient and cost effective method for the disposal of the non-volatile fuel contaminants in the diesel laden soil was the biological detoxification of the soils. SCS initially assumed that lighter hydrocarbon fractions, such as gasoline, would not be present at all or would only be present at low enough levels that they would not effect the bio-remediation This turned out to be the case. r ?of eatciifa- ti'�rieFne�t the�sbi>c ,fid� rithianaernetiraF "t X + 1pi?lxpzt]✓ rs.�' "he�so �iasyy'h fnitsiroyz/�'py¢ ` #aeoi PI?s • +h � 4^-qH_G t4pr W lr�' � dsafi� � 4U]C3Og�� r�wkU�r?1i3ri 'lr C)13�6R +' r'�v4 vVd This particular mushroom compost did not contain any chemical sterilization additives, btIt was treated strictly by a steam kill of the various pathogenic organisms that are found in, horse manure: Simplistically, the mechanics of detoxification in this application involves the eventual mineralization of the parent hydrocarbon compound i e diesel, into carbon dioxide, water vapor, and if present, free halogens such as chlormc Based on the chemical analysis, there were no halogens present in this contaminated soil material The bacteria and other microorganisms responsible for the mineralization action are naturally present in the native soil, which is the main reason that we utilized this r iethod The Iocal