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1990. As was anticipated from study of the isoconcentration maps, the lens of <br /> contaminated soil was found to extend to the east of the building footprint Study of these <br /> January trenches revealed that the coarse aggregate base rock only extended some 2-5 feet - <br /> east of the building footprint. As the gravelly base rock was acting as the reservoir for <br /> the diesel, it also served as a marker for the extent of diesel occurrence A concrete <br /> footing, several feet deep, formed a barrier to contaminant migration along the western <br /> boundary of the building. The contaminated soil to the south of the building had already <br /> been excavat sd, and the northern limit of migration was defined by the circular "non- <br /> detected" line, the outline of a pool of contamination in the porous gravel (Figures 2 and <br /> 3). <br /> Excavation of the diesel lens was completed in late January and early February of 1990 <br /> The procedure for removing the saturated lens was that, first, the surface layer of one or <br /> two feet which was not saturated with diesel was scraped off the top of the saturated lens <br /> with an excavator and stored in two stockpiles on-site. The layer of contaminant-saturated <br /> soil was then removed down to the dark brown native clay unit which acted as the <br /> lithologic retardant to any downward migration or percolation of the diesel This <br /> excavated soil was stored between two layers of polyethylene film, pending the <br /> commencement of remediation procedures. <br /> A visual inspection of the excavation and soil samples taken from the bottom of the <br /> excavation indicated that the contaminated soil beneath the site had been removed. <br /> The Microscopic PersIlective, Getting the Small Picture <br /> SCS-Erigirneer5 believed-that-the technologically-most efficient-and-cost-effective--method <br /> for the disposal of the non-volatile fuel contaminants in the diesel laden soil was the <br /> biological detoxification of the soils SCS irutially assumed that lighter hydrocarbon <br /> fractions, such as gasoline, would not be present at all or would only be present at low <br /> enough levels that they would not effect the bio-remediation. This turned out to be the <br /> case <br /> t Y ° fa- a e °" erii�i�a �rit�iftYily ` oVS`l �xi" iaageutent�of <br /> r.t tr � 2't�.'»s'° �a•Y r i <br /> l7 811]ara L ef :sf1 y� 1X 1`i a r+e►o © ost� icpri Ci' <br /> ru a f• `�w i . rrr I+_ �s:ziwr,'S i=nr ,.,•rcrrts.r "sgy •r � �a'� ,.ter- _� '$'P .r .+� `."�,, <br /> 5 <br /> Yfd d � ♦ r ar x., y � ' S � <br /> resrits t ohi ntonc rn�r logilh d opts +trv_ �_ ir> o ,A <br /> This particular mushroom compost did riot contain any,chemical stefilization additives,but <br /> was treated strictly by-a steam kill of the,various ,pathogenic organisms that are'found in <br /> horse manure:- Simplistically, the mechanics of detoxification in this application involves <br /> the eventual mineralization of the parent hydrocarbon compound, i e diesel, into carbon <br /> dioxide, water vapor, and if present, free halogens such as chlorine Based on he <br /> chemical analysis, there were no halogens present in this contaminated soil material The <br /> bacteria and other microorganisms responsible for the mineralization action are naturally <br /> present in the native soil, which is the main reason that we utilized this method The local <br />