Considering the big picture in environmental site remediation: How much is too much?

Contamination by the unauthorized release of a hazardous substance is always a regrettable event. Still, in some cases, particularly mature, urban retail gasoline sites, there’s a point at which the benefits of remediation may be overshadowed by its environmental impact and cost. It may be time for a broader look at how we assess the “big picture” regarding mature hydrocarbon plume site remediation and other types of environmental cleanup.

Consider a typical mature retail gasoline site remediation project: a property with underground storage tanks that have leaked hydrocarbons into the soil. One of the most common ways to remediate the resulting plume is to "pump-and-treat," which involves extracting impacted groundwater for contaminant filtering and proper disposal.

Soil and groundwater analyses at the start of most remediation projects show that contaminant levels decline quickly at first, but the efforts to reduce contaminant levels inevitably reach diminishing returns. In many cases, asymptotic concentration decline is reached before goal concentrations are achieved. So, what should we consider when deciding when treatment is doing more harm than good? The following are critical questions in that evaluation:

• What is the impact of the planned remediation on the environment? In many typical setups, pumps and other equipment are powered by diesel, gasoline, or propane – which consume natural resources and put carbon and other emissions into the air. While this is usually a worthy trade-off in the early stages of remediation, the negative impact of those emissions may eventually exceed the relatively small benefit of reduced soil contaminants when contaminant reduction has reached asymptotic decline. Even an electrically powered site has significant carbon impacts due to how electrical power is generated.
• Is the planned remediation program more of a nuisance to the community than a benefit? Noise from the pumps, generators, air compressors, and other equipment, as well as traffic from vehicles entering and leaving the site, impacts the flow of business and quality of life for people living in the area.
• Will the existing plume negatively impact planned future uses of the site? The treatment process may prevent the property from being developed in a way and timeline that most benefits the community—for example, through an employment-generating business at that location.
• Are there significant opportunity costs to proceeding with remediation? The financial cost of continuing with the remediation may be excessive where there is no tangible benefit to the community. With a generous dose of creativity and cooperation on the parts of the property owners, regulators, and responsible parties, money used to treat the soil is money that could be directed toward activities that meet the community's felt needs. This could include the development of the property for its next use, constructing neighborhood amenities such as a park or playground, or reducing the impact of vagrancy and homelessness.
• What is the current risk of the plume to human health? Depending on the planned uses for the property, exposure to contaminated soil and groundwater may be unlikely to begin with, and the health risks of the unlikely exposure are low. It may be in the community's best interests to rely on natural attenuation for remediation of the remaining contaminants. 

These “big picture” considerations have become increasingly evident to many in our industry, and significant progress has been made to aid in their evaluation. As a result of the development of the United States Environmental Protection Agency’s (US EPA’s) Spreadsheets for Environmental Footprint Analysis (SEFA) software, for example, it’s now possible to get a robust calculation of the carbon footprint for many types of remediation projects.

Software tools like SEFA can accept data inputs such as the type of pumps, fuel source, fuel consumption, the vehicles used to visit the site and how far and how often they must travel, and other factors to measure the environmental, social and economic footprint of the remediation process. These costs can then be weighed against the net benefits of the remediation to determine the best course of action.

Since the adoption of the Low Threat Closure Policy in California in 2012, we've seen a regulatory move toward more consideration of risk-based evaluations for closure determinations. This policy was primarily designed for mature leaking underground storage tank (LUST) cases where the site may still qualify for closure if certain conditions are met. The past decade has provided us with even more information to consider in addition to risk-based assessments, particularly in environmental impact.

Quantifying the environmental, social, and economic costs of our remediation efforts, especially in mature LUST cases, can provide critical guidance on when the costs of those remediation projects outweigh their benefits. Transparency and open communication between environmental consultants and regulators are critical to the success of any remediation project. Consultants, contractors and property owners need to keep local authorities, stakeholders, and state and national regulators informed about the site and what is being done to protect those impacted by contaminants in the subsurface. This way, the concerns of a wide range of stakeholders can be considered in determining the overall best outcome for the property.

The clarity provided by the numbers can be of great use in interacting with the community around the project. Members of the community may have strong ideas about what is important to them regarding the future of the remediation project. They may consider other community needs a higher priority than continued site remediation. A strong community consultation program can help understand these stakeholders’ concerns and priorities.

The idea that remediation work has its own considerable environmental impacts that eventually may outweigh the benefits is not new. However, our efforts to improve our communities with contamination remediation at mature sites stand to benefit greatly from the standardization of additional information. Specifically, the evaluation of remediation implementation carbon footprint, human health risk assessments, and cost analyses in our regular site assessment reports, including remedial action plans and closure evaluations, could profoundly improve our ability to make better decisions for the environment and our communities' future. 

GHD is working diligently to maximize the sustainability of our remediation practices, partly through the focused development of dedicated teams trained in using SEFA software and sustainability analyses. The regular inclusion of the additional considerations outlined above (in environmental impact, human health risk, economic and opportunity cost) can be added to standard site assessments and closure requests voluntarily.

However, we propose that this information is of sufficient importance for regulators to consider and be required in any remediation proposal or closure evaluation. Our communities only stand to gain from environmental professionals and regulators together, taking a broader perspective in our remediation planning based on the things that impact them the most.