FIELD DOCUMENTS FILE 2 - Laserfiche WebLink

Home Browse Search

George's Service Remedial Action Work Plan Project No.425.2 June 30,2011 • Some oxidants are toxic to humans and some(Fenton's Reagent)can produce significant quantity of explosive off-gas. • Possible production of unwanted by-products in the subsurface, as this reaction is capable of oxidizing a wide range of substrates and causing biological damage. • Low permeability soil horizons are less likely to be penetrated by the oxidant over short injection period. • In 2004 and 2005 GTI performed bench scale testing of ISCO, and in 2005 proceeded with ozone sparging and vapor extraction pilot testing. Monitoring during the pilot test showed that hexavalent chromium was present in the groundwater, so further use of ozone sparging was abandoned. 5.4. Monitored Natural Attenuation Monitored natural attenuation (MNA) consists of long term monitoring of groundwater conditions. Attenuation of a groundwater plume can occur through physical processes such as advection and dispersion, or through biological degradation processes. In theory, biological organisms that can degrade hydrocarbons are ubiquitous in the subsurface. These organisms metabolize the hydrocarbons in oxidation-reduction processes. This is the most economical approach as no infrastructure, equipment or utility costs are involved. The main expenditure is for laboratory analyses of groundwater samples and monitoring/sampling field activities. Concerns and Limitations Achieving Site closure depends on reducing groundwater concentrations within a timeframe acceptable to the appropriate regulatory agencies. It is apparent from the Site's historical groundwater monitoring that natural biological degradation will require a length of time that will not be acceptable to the regulatory agency and is not a feasible option at this time. 5.5. Air Sparging Air sparging is an in situ remedial technology that reduces the concentrations of volatile constituents in petroleum products that are adsorbed to soils and dissolved in groundwater. This involves injection of contaminant-free air into the subsurface saturated zone, enabling a phase transfer of hydrocarbons. The air injection pressure must be sufficient to overcome the head pressure of the overlying water column and the capillary pressure of the subsurface soil. The air flow rates must be as high as possible to deliver air to the subsurface, but must not be high enough to cause excessive off-gassing. If this were to happen, air pressure may cause the vapors to migrate to the surface and spread contamination in the aquifer. The pressurized air will be delivered though a screen that will introduce bubbles into the subsurface. The babbles will form channels or preferential pathways through which the air will flow. While in the channel, air will allow the gasoline to undergo a phase transfer from dissolved to vapor phase. Pulsing the air will cause pathways to collapse and new pathways to form enhancing the degradation process. Geological TeCAKICS Inc. 11 4252 RAP.docx