Environmental Remediation: What Are The Options?

The purpose of Environmental Due Diligence is to confirm a commercial property is not environmentally impaired.  The industry accepted method for evaluating environmental risks associated with a commercial property is the Phase I Environmental Site Assessment.  If through the Phase I Environmental Site Assessment process an environmental concern is identified, a Phase II Environmental Site Assessment may be recommended.  A Phase II Environmental Site Assessment is a limited intrusive study where soil, soil vapor, and/or groundwater samples are collected and analyzed to determine if the concerns raised by the Phase I Environmental Site Assessment actually translate to the existence of contamination at the property.  If contamination is detected, additional environmental sampling (Site Characterization) is conducted to determine the extent of the contamination.  Once the contamination is sufficiently understood with respect to depth, breadth, chemicals of concern, and media impacted (soil, soil vapor, indoor air or groundwater) a determination of if remediation is necessary is made.

When it comes time to remediate a property, several different remediation technologies are available, each designed to suit the property’s unique characteristics, the environmental clean-up goals, and the financial and time constraints of the project.  Additionally, in many cases a combination of more than one technology can be deployed to provide a comprehensive remedial strategy throughout the life cycle of the project.

 

SOIL REMEDIATION

Soil Excavation and Disposal: Simply, the contaminated soil is excavated, transported off-site to a regulated waste facility, and replaced with clean soil.  As long as verification sampling and analysis results show the remediation goals have been met, the remediation is complete.  Soil excavation can be costly, but the biggest benefit is the speed at which hazardous waste removal can be completed.  This can be critical in the case of a time sensitive property transaction, development project or refinance.  The most common challenges to a soil excavation project are the physical limitations.  The depth of an excavation can be limited by structural restrictions (proximity of buildings to planned excavations) and excavation equipment limitations. Remediation by excavation is most common when dealing with contaminants that are less mobile in soil such as heavy metals, pesticides, and other non-volatile organic and inorganic compounds.  Excavation and off-site disposal is often the only remedial option which can remove nearly 100% of the contamination from a property.

Soil Vapor Extraction: Most commonly used to remediate volatile organic compounds such as gasoline and industrial solvents.  Soil vapor extraction is a technology in which vapor extraction wells consisting of perforated PVC pipes are drilled into the ground and a high powered vacuum is attached to the wells to extract air from the soil.  Along with the air come the volatile chemicals.  The air is then passed through carbon canisters or a furnace to “scrub” or burn the chemicals from the air.  The clean air is then released to the atmosphere.  Relatively speaking, soil vapor extraction can take much longer than a simple excavation; however, soil vapor extraction is less limited by the presence of existing structures or the depth of the contamination.  Wells can be drilled to virtually any depth and can be placed inside or surrounding existing structures.  Once the initial system construction and installation is complete, soil vapor extraction can oftentimes be operated non-obtrusively while normal building operations continue.  Soil vapor extraction can also be much less expensive than soil excavation.

Enhanced Bioremediation:  Natural bacteria which feed on chemicals exist in the subsurface, over long periods of time, will naturally degrade the chemicals of concern.  With enhanced bioremediation, the bacteria colonies are promoted by injecting oxygen and/or “food” into the subsurface to propagate the bacterial colonies and speed up the natural process.  The efficacy is limited by several factors including the natural presence of the appropriate bacteria, soil chemistry, and lithology.  Bioremediation can take much longer than other technologies.  Although accepted in some circles, many consider enhanced bioremediation experimental and unpredictable.

 

GROUNDWATER REMEDIATION

Groundwater remediation is much trickier than soil remediation; however there are several technologies to treat contaminated groundwater.  The type of technology used is dependent on the type of contamination, the phase of the contamination in groundwater (floating product vs. in solution), and the site lithology to name a few.

Pump and Treat: Just as it sounds, pump and treat refers to the extraction of groundwater through groundwater extraction wells (similar to vapor extraction wells but set into the groundwater table) and treatment of the water through carbon canisters or at an off-site treatment facility.  The clean water is then either injected back into the aquifer or discharged to the municipal sewer or storm drain.  Through lessons learned in the last few decades, many remediation professionals consider pump and treat deployed by itself as a less-effective approach, opting to combine the technology with additional remedial strategies to provide successful remediation designs.  Nevertheless, in instances where groundwater contamination is floating away from a site, pump and treat can be quickly deployed to help stabilize the plume.

Air Sparging: Air sparging refers to the injection of air into the groundwater which effectively will “bubble up” through the groundwater and strip the contamination into the rising air.  This is very similar to how an aerator in a fish tank works.  Air sparging is often used in concert with soil vapor extraction, as the vapor extraction wells can capture this rising contaminated air and remove it from the subsurface.

Dual Phase Extraction: Dual phase extraction refers to the method of combining groundwater extraction (pump and treat) with soil vapor extraction.  Essentially, groundwater is continually extracted to lower the groundwater table, exposing the “smeared” contamination in the soil.  Soil vapor extraction is used to remove the contamination by extracting the air from the newly-exposed soil and drawing the contamination along with it.

Chemical Treatment: Chemical treatment involves injecting chemicals into the groundwater, which react with the contaminants, resulting in harmless by-products.  The biggest challenge to chemical treatment is the ability to adequately distribute the “good” chemicals effectively.  Adequate distribution of the chemicals are impeded by the presence of variable soil types (“heterogeneity” of the soil), which can cause uneven delivery, and lack of soil porosity, which can stop the spread of the chemicals.  This technology is gaining acceptance but the results are still considered unpredictable.

Enhanced Bioremediation:  As with bioremediation of soil, bioremediation of groundwater is limited by the natural presence of the appropriate bacteria, the groundwater chemistry, and lithology.

Monitored Natural Attenuation:  In some instances, natural degradation of contaminants can be sufficient in cleaning up the environment without active remediation.  By monitoring groundwater conditions over time and studying the chemistry of the site, predictions are made on the rate of natural breakdown.  If this rate of breakdown shows the cleanup goals can be achieved within an acceptable timeframe and before the groundwater contamination travels too far away from the site, the contamination can be left in place and the groundwater simply monitored periodically to confirm the predictions.  This approach is gaining acceptance, as it can often be the most cost-effective option in resolving a contamination issue.

 

REGULATORY OVERSIGHT

Typically, when remediation is occurring, a regulatory agency oversees the process ensuring the site has been appropriately evaluated, approving clean-up goals, monitoring the remediation process and ultimately approving site closure.  Depending on the current property use and planned future use, there are different acceptable levels of residual contamination that can be left in place.  Obviously, for a residential property or properties with other sensitive uses including schools and hospitals, the clean-up goals are quite stringent.  For commercial and industrial properties, the goals are less rigid.  However, if only the less stringent goals are met, the future use of the property will be limited and those limitations will be spelled out in a deed restriction which runs with the title of the property.

 

THE ENVIRONMENTAL CONSULTANT

Most property investigations do not go beyond the Phase I Environmental Site Assessment phase; however, on the rare occasion that a Phase II Environmental Site Assessment and Site Characterization reveal an unacceptable environmental or human health risk, selecting the right consultant is crucial.  The right consultant can be the difference between unnecessarily spending additional money and wasting months, if not years.

When selecting an environmental consultant to perform remediation on your property, there are a few qualities they should have:

Good Relationships with Regulatory Agencies: An environmental consultant that has experience working with local regulators will already be familiar with their requirements.  Every regulator has a specific “appetite”, especially with respect to site investigations.   Within some agencies, the appetite can be different between individual case workers.  Knowing what the regulator is looking for can save time and money by avoiding unnecessary work or wasting time doing work in fits and starts.

Experience with Different Clean-up Technologies: Since every site is unique, one or more specific technologies may be appropriate for each challenge.  A consultant that has experience with the strengths and challenges of each technology is in the best position to prescribe the best technology for your site.

Well Rounded, Vetted and Diverse Team:  Designing and executing a successful remedial plan is not a one-man or single-discipline task.  Dozens of technical factors can come into play during the remediation phase, including geology, hydrogeology and geochemistry constraints, engineering evaluations, regulatory and compliance requirements, and construction complexities.  A successful remedial team draws from different disciplines to navigate these factors.  Andersen Environmental’s team of Professional Geologists, Certified Hydrogeologists, Professional Engineers, Chemists and seasoned Environmental Professionals bring multi-faceted expertise in implementing successful remedial actions.

Andersen Environmental embodies all of these qualities and more.  Remediation can be overwhelming and often intimidating; we work closely with our clients to provide cost effective and timely solutions.

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