ARCHIVED REPORTS XR0008636 - Laserfiche WebLink

Home Browse Search

i 1 3.2 In-Situ Vapor Extraction lie In-situ soil vapor extraction utilizes a series of wells to remove VOC from the soil matrix A vacuum is applied to the extraction wells, typically by means of a blower, and VOC vapors contained within soil pore spaces are extracted from the subsurface In-situ vapor extraction can be a time and cost-effective remedial technology in permeable soil, and if contaminants are volatile at ambient temperatures Vapor extraction systems have been shown to efficiently remove lighter-chain hydrocarbons (e g , gasoline) from soil Vapor extraction systems have also been shown to effectively remove floating liquid contaminants, and have a limited effect on dissolved contaminants In general, the vapors brought to the surface will require treatment, unless contaminant concentrations are low Numerous options are available for treatment of extracted vapors In order of decreasing contaminant concentration, treatment options include thermal incineration, thermal oxidation, catalytic oxidation, carbon adsorption, and direct discharge (no treatment) The type of vapor treatment is determined by local air discharge regulations, cost, contaminant types, and concentrations 1 3 3 Physical Containment ' The physical containment of contaminants in soil is accomplished either by the injection of stabilizing agents into the soil matrix or by excavating soil and adding a stabilizing, vitrifying, or encapsulating agent The success of physical containment methods mainly depends on soil matrix grain size Soil with a coarse-grained matrix has a relatively high permeability and low attraction between soil particles, thus enhancing the ability of stabilizing agents to completely penetrate the soil Soil with a fine-grained matrix has a relatively low permeability and higher attraction between soil particles, thus inhibiting the introduction of stabilizing agents and reducing the effectiveness of the stabilizing process The presence of groundwater in close proximity to a containment area complicates placement of stabilizing agents and the ability of the agents to set up at or below the soil/water interface. Because physical containment does not remove or degrade waste material, long-term monitoring may be required This alternative is feasible for a wide range of organic and inorganic compounds 2 0 GROUNDWATER REMEDIATION 2 1 No Acton ' This alternative to groundwater remediation involves a negotiated plan to monitor groundwater quality without an active remediation system Generally speaking, for this option to be considered, free-phase product must not be present on the ' groundwater table For example, it is a matter of policy with the California State Water Resources Control Board regarding leaking underground fuel tanks saes that free-phase petroleum product must be removed from the groundwater table in all cases In any event, contaminants in groundwater must be demonstrated not to pose an immediate and/or long-term threat to the public health