In Situ Technology Applications
Versar's remediation specialists have the training and practical knowledge to design in situ technical approaches to achieve your remediation goals. We develop safe, environmentally compliant solutions that are cost effectively deployed to minimize long-term restoration costs by achieving site closure as rapidly as possible.
Versar remediation specialists have worked with many different approaches for chemical and biological treatment at our clients’ job sites. We often use combined remediation technologies or use them sequentially to achieve different treatment goals at different stages in the overall remediation project. We apply chemical and biological reagents by subsurface drilling or direct-push technology (Geoprobe™), and supplement drilling by hydraulic or pneumatic fracturing of the soil to create expanded treatment zones when soil conditions are impermeable or non-porous.
Subsurface microbiological conditions may be amenable to enhanced reductive dehalogenation to transform chlorinated solvents (and related compounds) to less toxic and/or less concentrated forms. Natural geochemical conditions at a site may be well suited for implementation of innovative solutions such as biogeochemical in situ reductive dechlorination (BiRD™), a unique process that uses native iron and sulfate conditions to destroy chlorinated solvents.
The use of emulsified vegetable oil substrates, along with carbon amendments like dairy whey, simple sugars like molasses, and other specialty compounds that provide bacterial populations with micronutrients and specific growth factors to enhance the biological destruction of contaminant mass has been highly successful in the appropriate setting. If the necessary bacteria are not indigenous to the site, bioaugmentation may be necessary to "grow" the appropriate bacteria through inoculation of soil and/or groundwater with bacteria grown in a laboratory from a similar site. In situ chemical oxidation may be enhanced by other processes and products such as surfactants that help absorbed contaminants to be released from soil mass or by using stabilizers to slow the chemical reactions, allowing the chemical reagents to remain in place longer in the subsurface and contact more contaminants through flow and diffusion.
Versar remediation experts use in situ technologies as preferred approaches to achieve environmental restoration with the goal of reducing project life cycle costs and the time to accomplish cleanup.
In situ technologies generally reduce or eliminate the following:
- Site disturbances caused by construction
- The need for utility services like electric power, water, and sewer
- The generally high capital investment required for traditional remediation equipment
- The impact of the environmental footprint of the project
Versar has specific knowledge and capabilities related to in situ technologies. Our goal is to minimize site disruption, allowing you to continue using your property as appropriate. Let us present you with detailed options to achieve your project objectives using in situ chemical and biological remediation in a cost-effective and non-intrusive manner.
Versar has significant, ongoing state-of-the-art experience with in situ enhanced bioremediation (ISEB) as a viable treatment technology for both soil and groundwater contamination resulting from many different contaminants of concern (COCs). We focus on applying the ISEB strategy to a target treatment area, combining the benefits of biostimulation and/or bioaugmentation to treat plumes of chlorinated solvents (CVOCs), pesticides, and petroleum products, and other COCs. Using ISEB, we have developed approaches to destroy contaminant mass to concentrations below state and/or federal target levels within a prescribed time when project duration is a primary driver. We have also developed bioremediation programs to achieve targeted mass destruction over time, then transition to a monitored natural attenuation approach for sites where project duration is not the primary driver, where costs become prohibitive, or land use is not expected to change over time (i.e., remains an industrial setting with land use controls in place). The practice of bioremediation as an environmental treatment technology has advanced tremendously in the last ten years as the physical, chemical, and biological processes that occur in the subsurface environment have been studied and performance data has been collected and analyzed at numerous bioremediation project sites throughout the world.
In-situ chemical oxidation (ISCO) and in-situ chemical reduction (ISCR) are two widely used treatment approaches for environmental restoration sites. ISCO/ISCR involves the introduction of a chemical oxidant or reducing agent, respectively, into the subsurface to transform groundwater and/or soil contaminants into less harmful chemical species. The four most commonly used oxidants include 1) permanganate (MnO4-), 2) hydrogen peroxide (H2O2) and iron (Fe) (Fenton-driven, or H2O2-derived oxidation), 3) persulfate (O5S2-), and 4) ozone (O3). ISCR is most often used to treat COCs via the injection of granular iron filings under reducing conditions in groundwater, and often leads to synergistic physical, chemical, and microbiological reactions that destroy targeted COCs.
Chemical technologies are widely applicable to a broad range of COCs because many contaminants react at relatively high rates in comparison to natural biological process (e.g., natural attenuation). ISCO/ISCR may be used successfully for COCs absorbed onto soil and/or dissolved (or mixed) with site groundwater. While these facilitated chemical reactions are rapid and often more complete due to the addition of specific reagents, substrates, and amendments, there are inherent difficulties associated with chemical handling, heat generation and the frequent mobilization of naturally occurring soil constituents like metals (arsenic, chromium). Still, when the subsurface environment at a remediation site is characterized adequately and geochemical conditions are favorable, chemical technologies are highly successful in achieving site closure rapidly and economically.