Our client, a large multi-national chemical company, approached us with a unique environmental challenge: (1) soil and groundwater at our client's former chemical plant property contained several types of contaminants, (2) our client had a potential buyer for the property, (3) the regulators were both risk-averse and inflexible, and (4) our client's local consultant had already proposed a conventional, but expensive, remediation. There was a lot of work to be done to satisfy both our client and the regulator.
The approximate 6-acre property included old, abandoned buildings formerly used to manufacture chemicals. During decommissioning of the building, our client encountered distinct areas of historical contamination, including (1) petroleum hydrocarbons, (2) metals, and (3) herbicides from a variety of previous operations.
Complicating the regulatory sensitivity of the matter, the property was immediately adjacent to artificial recharge basins for the drinking water aquifer for the community. This artificial recharge caused annual water table fluctuations of 25 feet. Additional project concerns included:
Similar to getting a second opinion regarding a medical condition, we often provide an environmental second opinion for our clients. Typically, these second opinions are for potentially-expensive environmental remediation projects.
During our peer review of the data and previous investigations, we found that the consultant's Conceptual Site Model (CSM) was inadequate. The CSM is critical in selecting a remedial approach. The CSM is, in essence, the consultant's synthesis of their understanding of the site geology, hydrogeology, and distribution and fate of contaminants. If the CSM is not "robust," the remedial plan can easily be ineffective, more costly than necessary, and/or "take forever."
Our peer review identified several gaps in the existing data. The regulator was already concerned due to the sensitive location of the property with respect to the public water supply. So these data gaps left the risk-averse regulator the "logical" approach of dig-and-haul remediation.
One of the key sticking points with the regulators, and rightfully so, was protecting the underlying aquifer. The regulator's position was that any contaminant at any concentration would negatively affect the underlying aquifer. Accordingly, having a robust CSM that was defensible was critical to gaining the regulators' confidence in any approach to remediation. As mentioned, the site had multiple contaminants, including organic and inorganic compounds. These contaminants "behave" differently in the subsurface relative to degradation and mobility.
Shoring up the CSM meant gathering enough data to show that we (1) understood the dynamics of the artificial recharge of the aquifer, (2) knew where the contaminants were (and, as importantly, were not), and (3) could show how our approach would protect the aquifer.
With respect to understanding the aquifer dynamics, the site already had many groundwater monitoring wells both on, and off, the property. The client had monitored many of these wells for years. We strategically installed a few more monitoring wells in areas of soil contamination and along property boundaries. We combined (1) the new data with (2) historical data and (3) the groundwater model that had been prepared by the local municipality to convince the regulator that the aquifer was safe (even if we did nothing to the contamination in soil).
To better define the nature and extent (horizontal and vertical) of the contaminants in soil, we conducted a refined delineation sampling event. From these additional data, we demonstrated that the specific types of contamination (petroleum hydrocarbons, metals, and herbicides) occurred in separate areas of the property. The spatially distinct areas of impact allowed us to approach each area/contaminant type independently and get step-wise remediation "approval" of the individual areas while we continued negotiating the remaining areas.
Our client's goals for remediation were two fold. First, get regulatory approval, and second, make sure they could sell the property for residential development.
Previously proposed remedial actions to meet these goals focused on costly, broadbrush excavation and off-site disposal (over 10,000 tons of soil at approximately $7,000,000). While this approach was generally acceptable to the regulator, it was far from cost effective for our client. Additionally, due to the depth of the petroleum contamination (down to 55 feet), complete removal by excavation was impractical. However, anything less than complete removal was problematic for the regulator.
As previously stated, different chemicals behave differently in the subsurface. Understanding these behaviors and combining them with a robust CSM provided an opportunity to evaluate and implement individual remedial actions for the distinct areas with impact.
Metals Remediation: The refined delineation sampling indicated metals contamination occurred in 15 distinct areas. The refined delineation permitted targeted "dig-and-haul" remediation that was cost effective and easily negotiated with the regulator. This approach reduced dig-and-haul for metals-impacted soil substantially.
Petroleum Hydrocarbon Remediation: The petroleum hydrocarbon contamination was the result of an old tank farm (circa 1940s to 1960s) where Bunker C and #2 fuel oils were stored and handled for many years. Part of the complicating factor was that the artificial recharge of the aquifer created a "smear zone" in the subsurface from about 30 feet below grade (high water table) to 55 feet below grade.
The regulators were very concerned that this smear zone would continue to be a "source" of hydrocarbon contamination every time the annual aquifer recharge (and subsequent drawdown) forced the groundwater back and forth through the "smeared" residual hydrocarbons.
We used historical groundwater data to demonstrate to the regulators that this residual hydrocarbon contamination was immobile. As a further measure to reduce the hydrocarbon impact, we remediated the soil using insitu chemical oxidation (ISCO).
Although the ISCO treatments removed much of the hydrocarbon mass, a certain portion was unaffected by the oxidants. This confirmed the recalcitrant nature of the old and weathered petroleum and further demonstrated that this portion of the hydrocarbon impacts did not affect the groundwater and would not be a future source of contamination to the aquifer. Ultimately, we were able to negotiate leaving the residual hydrocarbon impacts in place and adding a restrictive covenant to the deed. In this manner, future exposure to the residual impacts was eliminated while not impeding the future property redevelopment.
Herbicide Remediation: Herbicide contamination occurred in the soil at mainly two distinct locations. We used our Environmental Fate and Treatability Laboratory to investigate potential alternatives to off-site disposal (which would be extremely expensive). We conducted bench-scale tests of herbicide-contaminated soil to confirm we could utilize ex-situ, on-site bio-enhanced degradation. We treated 1,300 cubic yards of contaminated soil arranged in elongated piles inside one of the vacant buildings on the property. After 12 months, we were able to return the now-acceptable soils to the on-site excavation areas.
Our "secret" to environmental closure of this old chemical plant is the same secret behind how we have helped our clients for more than 30 years. That is, we insist on developing a robust CSM so our clients have a thorough understanding of the site. This then allows our clients to explore cost-saving options to site closure.
In this case, our robust CSM, as well as scientific understanding of the physical and chemical dynamics of the site, enabled us to develop a strategic remediation plan and achieve regulatory approval. We were able to complete our remediation for $2,000,000, saving our client $5,000,000. Our client subsequently sold the property to a residential developer.
Our client's director of regulatory affairs wrote to us saying, in part, "I appreciate the fact that you have saved us a substantial amount of money by providing cost-effective remedial investigation and cleanup approaches acceptable to the California, Georgia, Michigan, and New Jersey regulatory agencies."
Dragun Corporation is an industry leader in Environmental Regulatory Issues and Consulting for clients across North America and internationally. From manufacturing and real estate to chemical companies and livestock agriculture and municipalities. At Dragun, science, engineering, and decades of expertise converge through in-depth critical analysis, conceptualized approaches, and technical application. The result is an environmental site assessment, remediation, compliance assessment, or expert services support that helps clients in diverse industries.
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