Is It Really Clean?

Is it really clean? Many times, this question is never asked, let alone answered. For us, the question became an issue to our environmental consulting firm during the planning stages of a brownfield remedial project on the south side of Chicago. The 17-acre tract historically supported two small oil terminals, which likely operated during the 1930s and 1940s. Records revealed that both terminals were supported by rail and included aboveground storage tank farms.

Redevelopment of the property would go from manufacturing to residential under the Illinois Voluntary Cleanup Program. Both a start and finish dictated by a pending property transfer/re-development and TIFF supported finance constrained remedial options. The imposed constraints eliminated several options, and the final plan called for excavation, removal and replacement of roughly 60,000 cubic yards of petroleum contaminated soils. Disposition of contaminated materials was through offsite biotreatment. A replacement with clean fill materials brings us to the question: Where to find clean fill soils?

A survey of local and regional earth-moving projects was initially conducted. Short listing those sites meeting physical property constraints followed assessments of suitability regarding cleanliness. Replacement soils had to be risk free and because of the residential re-development of the property, we did not want to inherit another site's problem. This was no small task.

While approved Corrective Action Plans will typically specify clean fills, in practice there are generally no requirements to address the cleanliness of fill soils, let alone a defensible documentation. This is usually left to the judgment and experience of the construction manager. In Illinois, U.S. Environmental Protection Agency (EPA) guidance for developing remediation objectives includes the Tiered Approach to Corrective Action Objectives (TACO). A similar nationally recognized program is the Risk Based Corrective Action (RBCA). In either guidance, risk is broadly defined as the probability of a detrimental occurrence under a certain scenario. Both result in or default to a minimum contaminant concentration below which there is deemed no risk (i.e., no further remediation).

I hope everyone has already picked up on the concentration basis of objective determinations. We somehow lost the fact that risk is also based on the mass at a given level of contamination. Once an objective is determined, remediating to that level is required at all locations. (On this project, the performance criteria were met with the approval of a 20-foot sample grid spacing.) This is quite a safety factor, considering that the model used to establish the basis of the Tier I TACO objective is a ½-acre site consisting of soils from the surface to the top of groundwater, roughly equivalent to a surface area of 200 by 200 feet.

(Certifying a ½-acre remediation parcel requires approximately 117 samples to get the required coverage.) EPA is requiring a high assurance of remediation, as they should. Also, what is returned to the site should be considered equally important. If the Correction Action Plan called for replacement with treated soils, it would be done.

When clean soils were returned to the excavation, documentation was considered important to us to protect both the client and future property owners. Working from the short list of suitable sites, a sampling program was established and site selection for clean soil was based on the probability of analytical results exceeding the remedial objectives for contaminants of concern. The statistical approach was selected as a defensible method to meet a similarly high level of assurances that return soils meet standards EPA sets for remediation of the site.

The difficulty in meeting this internal standard came as a surprise. Numerous excavation projects in the local area were preliminarily screened. The bulk of the projects were excavations for new construction and/or re-build. We found that the majority of construction companies were more than willing to find a home for excess soils, especially if they did not have to pay for the hauling. In some instances, companies were actually willing to deliver to the remedial site free of charge because of the shorter haul distance and potential overall savings. All sites looked at offered "clean" soils. The problem is that companies doing construction do not necessarily assess the environmental concerns as they should. What contractors were offering as clean, not only failed our statistical criteria, but in some cases were outright rejected due to petroleum odors. Others were eventually rejected because of noncompliance to the residential objectives mandated by the TACO guidance.

Some of these same soils were actually used as surface backfills at new home construction sites. One of the sites considered, but rejected upon assessment, was a former leaking underground storage tank (LUST) property that had received a No Further Remediation declaration. Even sites having virgin soil stockpiles were rejected due to the probability of an exceedence upon evaluation of data. In fact, one of these sites is reported to have been used by other environmental contractors as a source of clean backfills and was initially considered for purchase. Crushed concrete was also evaluated and rejected due to the presence of semi-volatile organic concentration above cleanup objectives. Although meeting our statistical criteria, even a State-sponsored floodwater retention project showed low levels of contaminants.

We were not surprised by some of the sites rejected, considering the nature of the areas and soil materials. The presence of low level poly nuclear aromatics (PNAs) in the large stockpiles was a bit unexpected. Where and how these residuals were generated can only be guessed. One possibility is that through fuel line leaks, field servicing and refueling, enough fuel is lost over time. Storm infiltration is able to sufficiently disperse residuals to have them initially detectable in a large stockpile and have them exist in concentrations at levels of potential concern. Another possibility is that soils were moved in freezing weather and drivers sprayed their truck boxes to prevent soils freezing to the steel bed. Though frowned upon, this practice remains alive -- as seen through personal observations.

We were successful in finding an industrial park construction site and were able to direct loaded virgin soils meeting all criteria from cuts and storm water retention structures and transport them to the remediation site for placement and compaction.

It is known that clean soils can be found and should be used in remediation projects. The question is this: What is the risk to the public where the construction norm is not to ask or assess the quality of soils that are freely and indiscriminately placed in and around the community?

If these activities do not pose a risk, then environmental cleanups are jumping through many more hoops than necessary. I support the position that addresses true risk. Dual standards, saying it is ok to do here but not there, fails the public's best interest and leads to an undermining of the need to properly manage residuals and clean up sites where risk is an issue.

I also believe in risk assessment as a tool, but it needs to go farther than just establishing concentrations.

Finally, if it is our responsibility to clean up a site, one should use the experiences of this project to insure it is clean and not relocating and diluting some other problem.

This article originally appeared in the 02/01/2002 issue of Environmental Protection.

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