Feasibility Studies & Corrective Action Plans

Following the completion of chemical characterization in site media (i.e., soil, soil vapor and groundwater) and development of a Conceptual Site Model (CSM) that has determined remediation at a site is necessary to reduce concentrations, a Feasibility Study (FS) can be completed to determine the technical and economic feasibility of applicable remediation technologies for achieving project cleanup goals. Once a suitable remediation technology has been selected, a Corrective Action Plan (CAP) detailing the selected remediation technology, including engineered design specifications and drawings, can be prepared for agency approval and implementation.

Remediation Systems

Remediation systems use a variety of physical and chemical processes to remove or treat contaminants. Remedial strategies include:

• Air Sparging – is a groundwater remediation technique that entails injecting contaminant-free air into the saturated zone.  The injected air moves upward through the saturated zone soils as bubbles and / or through air filled channels. Through in-situ air stripping, the injected air volatilizes and removes dissolved and adsorbed phase VOC contaminants from groundwater as they preferentially partition into the vapor phase and are transported to the unsaturated zone. A positive side effect of AS is that the injected air raises the dissolved oxygen content of groundwater which enhances in-situ aerobic biodegradation of hydrocarbons. Thus, this technology provides for both the physical removal and biodegradation of hydrocarbons in groundwater and saturated zone soil.

• Soil Vapor Extraction –  is a remedial technology that physically removes VOC contaminants in the unsaturated zone liberated by air sparging by applying a vacuum to this zone via extraction wells.  The vacuum induces a subsurface flow of soil pore air/soil gas containing volatile vapors to the wells.  As the soil gas is drawn towards the vacuum source, the equilibrium between the VOC phases (i.e., free phase, adsorbed phase, vapor phase and dissolved phase) in the subsurface changes, causing enhanced partitioning into the vapor phase. The vapors are then collected and delivered to a treatment unit where they are either destroyed or captured prior to venting the clean air stream to the atmosphere. In the unsaturated zone, clean air is pulled in from the periphery to replace air extracted from the contaminated area.  The VOCs in the unsaturated zone liberated by air sparging then volatilize into the new air and are continuously removed by the extraction system. 
• Dual Phase Extraction (DPE) – also known as multi-phase extraction, vacuum-enhanced extraction, or bioslurping, is an in-situ remediation technique used to remove contaminants from both soil and groundwater. Extraction wells are installed into the contaminated area with screened sections that extend through the contaminated soil and groundwater zones. A high vacuum is applied to the extraction wells drawing contaminants into the wells. The extracted mixture of contaminated groundwater and soil vapor is separated into liquid and vapor phases. The liquid phase is treated to remove contaminants, while the vapor phase is passed through a vapor treatment unit (e.g., activated carbon, thermal oxidation) where they are either destroyed or captured prior to venting the clean air stream to the atmosphere.
• In-Situ Chemical Oxidation or Reduction (ISCO / ISCR) – involves the injection of reactive chemical oxidants or reductants into groundwater and soil for the primary purpose of rapid and complete contaminant destruction. 
• In-Situ Thermal Remediation (ISTR) – ISTR is a technique for source zone remediation of organic compounds with a high degree of certainty for achieving remedial objectives and refers to the application of high heat (80 to greater than 100 degrees Celsius) to subsurface groundwater and soil by various methods, with a focus of remediating source zone contamination by vaporizing the contaminants via sub-surface heating, followed by contaminant extraction and treatment. Relative to other conventional remedial alternatives, ISTR technology is capable of rapidly treating organic compounds below screening thresholds and even non-detectable concentrations in many instances.