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511i, 1169:i 111' S. jA r'+ Lammersville School District 202/899.7004 July 16, 1990 20 Groundwater extraction appears to be a viable remediation technique for this site. A groundwator treatment system would be needed to treat water prior to discharge. An analysis of treatment options(air stripping,carbon adsorption,or above-ground biological treatment)and discharge points(sanitary sewer, storm sewer,or re-infiltration) would need to be performed. 9.3 IN SITU SIODEGRADATiON The remedial action of in situ biodegradation involves the development of a hydraulic control system similar to the groundwater extraction and treatment met`tod. In addition, a site-specific nutrient mix is developed to increase hydrocarbon utilizing microbe populations in the groundwater. The nutrients are introduced through the soil and into the groundwater through a well or infiltration gallery to stimulate the growth of the hydrocarbon-utilizing microbes. Oxygen is supplied through the use of an oxidizing agent. The advantages and disadvantages of in situ biodegradation are outlined below: I _.: In situ Eiode radation Advantages _ 1. Treatment of the dissolved hydrocarbons. 2. Decreases the overall length and cost of remediation project. 3. Water is infiltrated back into the subsurface, creating a closed-loop system. In situ Biodegradation Disadvantages 1. Moderate to high initial cost to implement system. 2. Moderate operational and maintenance costs. • Requires continued monitoring and sampling. TM 4. Requires permitting for water discharge. 5. Feasibility study is required. S• Potential operation problems include well plugging, nutrient sorption to soils, and poor oxygen transfer. At the present time, in situ treatment is not being considered as the primary treatment method to remediate the site, owing to the potential operation problems. However, in situ treatment may be studied as an addition to a groundwater extraction system. Investigating this treatment option at a later date would allow time to getter understand the site hydraulics (by running the groundwater extraction system) before nutrients are introduced into the subsurface. Once hydraulic control of the plume is _achieved, and-levels ofhydrocarbons..reduced,-a n.in..situ.feasibility.-study_might.be.perforrned.-to.gather Er. GROUNDWATER TF.cilNOLOGY.INC.