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S f 15 February 2000 AGE-NC Project No 98-0448 Page 28 of 33 9 3 1 Nutnent Requirements And Toxicity The microbes require certain essential nutrients that are usually available In ground water If supplemental nutrients are required, such as nitrogen and phosphorus as ammoiuum pho'sphate in ' liquid phase,the quantity is usually very low However, a Waste Discharge Permit is required by the RWQCB for the infection of nutnents into groundwater, furthermore, the RWQCB has been very ' reluctant to issue Waste Discharge Permits Typically,the microbes utilized In bioremediation of ground water are aerobic and commonly require ' additional oxygen to supplement dissolved oxygen concentrations in ground water Generally, several air spargmg or in-well aeration sources are sufficient to provide the necessary oxygen However, in some cases the addition of hydrogen peroxide or other oxygen source is necessary I } 9 3 2 Monitoring Activities After inoculation, the inoculation wells and ground water monitoring wells should be monitored for several months by periodic field measurements oforganlc vapor,carbon dioxide and oxygen Ground water samples should be collected and analyzed for petroleum hydrocarbons, bacterial populations and nutrient availability If morutonng indicates areas of slow remediation, additional inoculations Imay be required I9 3 3 Feasibility Studies In-situ bioremediation at the site has a low feasibility, the results of the microbial enumeration and Iphysicochemical analysis in soil indicated that hydrocarbon degrading organisms were generally inadequate to support microbial growth and bkoremedial activity The analysis indicated that biodegradation was occurring at a slow rate due to the small percentage of biodegraders The Ilaboratory suggested that an alternative carbon sources (i a organic debris) may be the dominant food source for native microorganisms Based on the assumption that the gasoline release occurred a minimum of 20 years ago, laboratory analysis of soil and ground water samples collected during the ongoing site investigation suggests that little apparent natural attenuation has occurred during the last 20 years 9 3 4 Duration IDuration Land cost) of in-situ bioremediation are dependent on the volume of soil and/or water to be remediated, the number of inoculation and monitoring wells, the average concentrations of Advanced GeoEmlronmental,Inc