SITE HISTORY - Laserfiche WebLink

Home Browse Search

29 April 2005., .\ . . . AGE-NC-Project No..98-044.0 ` ' •Page•17 of-18- . . •• .. . - �. .._ : . Oxygen depletion in the subsurface is a characteristic'of biodegradation:Tli&bore of a contaminant 'plume is typically under anaerobic conditions wind only the margins,are aerobic. Therefore, even ,though anaerobic biodegradation is much slower than aerobic.biodegradation, anaei'ebic processes ...' e, 'May dominate;the degradation of contaminants:Ground,watei movement will'•gene' 11:'assist inthe ` ,. transport of nutrients in'the saturated zone. . _ ,The objective of the MNA is to collect-ground water samples through techniques which generally minimize undesired exposure to atmospheric conditions when and where allowable;and to monitor for parameters which signal'the natural attenuation ' f dissolved-hydrocarbons. Generally the geochemical parameters-selected:for monitoring are based on the.use of terminal electroh;acceptors as-microorganisms consume hydrocarbons. The sampling for NINA analysis would be.conducted , _ during.the'monitoring events to reduce overall-costs, to established a trend of the.geochemical parameters'and demonstrate the presents of terminal electron acceptors.metabolized by-products. Natural attenuation is normally used where .low. concentrations of hydrocarbons are present, following completion of another form of remediation or in an area where no domestic or irrigation _ wells are threatened. Costs for natural attenuation are generally.lower than most active remediation options; however, costs can be highly variable depending on the duration and type of monitoring required.' Fate and Transport modeling may be used to demonstrate the.potential for hydrocarbons to impact, nearby ground water receptors. Quarterly.grourid,water monitoring may also be.used,to demonstrate, a stable and declining ground;water-plume. ' 8.0. .RECQMMENDATIQNS , The, following recommendations for.remediation- are based upon data collected during the inve's#igatiori"of the property and predicted responses frons the site conceptual'model. .8.1. REMEDIATION 0E-HYDROCARB6N-1MPACTED SOIL ;Nadose;zarie soil impacted?by TFH-d, TPH-g; and BTEX extends vertically to the saturated zone under.the former UST and.surrourfding areas to an approximate depth of 17 feet bsg. Excavation. would require' the removal of a moderate volume of overburden soil in'the former'UST' and surrounding areas.Figure 9 illustrates the approxiinate area-of proposed excavation. Because'there- appears.to be a low-feasibility for bioremediation and monitored natural attenuation,AGE concludes -Advanced Geo$nvfrOimmentih Inc.