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Mr Nuel Henderson, Jr, SJCPHS July 1, 2003 Remedial Action Pian ARCO Station No 6100 Page 10 Air bubbling (AB) is typically used in conjunction with soil vapor extraction AB involves the use of an air compressor to infect low volumes of ambient air into existing monitoring or vapor wells Either a 1/4 -inch or a %2 -inch tubing, connected to a ceramic diffuser, is placed at the bottom of the well Air flow rates in the range of 1 to 2 cfin are injected into the wells Petroleum hydrocarbons dissolved in groundwater are volatilized and captured by the vapor extraction system In addition, AB enhances insitu biodegradation through increased dissolved oxygen content in groundwater Dual Phase Extraction Dual Phase Extraction (DPE) involves concurrent extraction of groundwater and soil vapors from a common extraction well under vacuum conditions DPE provides a means to accelerate removal of dissolved groundwater contamination, remediate capillary fringe and smear zone sails, and facilitate removal of vadose zone soil contamination A DPE system will address removal of the adsorbed phase hydrocarbons in the soil above and below the water table, as well as the hydrocarbons dissolved in groundwater A high-vacuum blower (liquid ring blower) is connected to a pipe (drop-tube) installed . within a well that has openings only in the lower portion of the well Once the soil vapor and groundwater are removed from the subsurface, they are partitioned aboveground by an air/water separator The hydrocarbon-laden vapors and groundwater are then channeled to separate treatment systems The soil vapors are typically treated with thermal or catalytic oxidizers, and groundwater is treated using granular activated carbon vessels (GAC) Since the groundwater encountered in wells on-site is perched, and an established groundwater table beneath the site has not been identified, DPE is not a viable remedial alternative Applying high vacuums might result in wells running dry within a few hours or days Moreover, design and implementation of a treatment and disposal system for a limited quantity of groundwater is neither practical nor cost effective Bioremediation Bioremediation is engineered degradation of petroleum hydrocarbons in soil and groundwater Bioremediation technologies are effective in mitigating petroleum hydrocarbon impact to soil and groundwater Passive bioremediation technologies applicable to soil treatment are mainly ex-situ treatment such as land farming and incineration, etc , which consist of excavation of impacted soil In-situ bioremediation technologies, such as bioventing, peroxide, and ozone infection, etc , have also been used to remediate petroleum hydrocarbon impact to the vadose zone P 1Bp-Arca for URS161001Reports\Arco 6100 RAP doc