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r <br /> , y <br /> 1 14 November 1995 ^ <br /> AGE-NC Project No 95-0121 <br />' Page 11 of 20 <br /> = ti <br /> yards would require treatment or disposal Approximately 1,000 cubic yards of excavated soil would <br /> be"clean" overburden <br /> 1t V- Ty <br /> However, since the hydrocarbon-impacted soil extends off-site, it is unlikely that all of the impacted <br /> soil can be removed, thereby leaving impacted soil as a potential source of hydrocarbon-impact on <br /> the ground water ` <br /> 1 r <br /> Once excavated, the soil must then be treated on-site or disposed of off-site Replacement backfill <br /> material must be imported if off-site disposal is chosen The cost for excavation, treatment/disposal <br /> Iand backfilling would likely be between $80 00 and $120 00 per cubic yard, depending upon <br /> concentrations of hydrocarbons Total costs for excavation and treatment or disposal could therefore <br /> approach $250,000 ' <br />' 63 IN-SITU BIOREMEDIATION <br /> Acceptance of this treatment technology by the regulatory'commumty has grown in recent years, as <br /> success has been achieved at sites in California and elsewhere , <br /> £ <br />' 6 3 1 PRINCIPLES , <br /> For this remediation method, hydrocarbon-degrading bacteria are propagated in a liquid medium, <br /> which is,then infected into inoculation wells screened through the interval of contamination If ground <br /> water has been impacted, strategically located ground water monitoring wells can be used for <br /> inoculation Once in the contaminant plume, the bacteria degrade the hydrocarbons and spread <br /> Ilaterally and vertically by migrating and reproducing, creating an advancing remediation front <br /> Hydrocarbon-degrading bacteria metabolize hydrocarbons and assimilate,the resulting organic <br /> chemicals into biomass for reproduction and growth, and release water and carbon dioxide as waste <br /> products The light-end hydrocarbon's are consumed first, followed by heavier hydrocarbon, Y <br /> molecules , - <br /> I6 3 2 NUTRIENT REQUIREMENTS AND TOXICITY - <br /> The bacteria require certain essential nutrients, which are usually available in native soil If . <br /> supplemental nutrients are needed,, the quantities and concentrations are' generally `very low, <br />• comparable to the quantities and concentrations utilized for light agricultural use <br /> Y <br /> V , <br /> I 1 jl <br />■ I t „ i ' I , i Y ' <br /> + t <br />