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Historic Fill Material: More than Meets the Eye

Modified stone and entire brick walls were observed on a project located in downtown Allentown.

It’s not unusual for contaminated soils to be found at a site when there is no obvious spill or release that contamination can be linked to. This scenario is often a consequence of the use of the historic fill materials. In Pennsylvania, historic fill was commonly used prior to 1988, before regulators adopted policies to regulate fill material. Many urban areas are underlain by material that was typically placed during construction to bring an area to a specific topographic elevation. More often than not, this material was previously contaminated because the fill material itself was a byproduct of industrial processes. Historic fill material can be composed of many different elements like wood, coal ash, dredging spoils, construction demolition material, and contaminated soil, which may not be native to the area.

The most common contaminants associated with historic fill are polycyclic aromatic hydrocarbons (PAHs) and metals, such as petroleum constituents or lead. PAHs are created when materials like coal and wood are burned. Lead, Cadmium, and Arsenic, are often causes of concern when dealing with historic fill. Chronic health conditions are associated with each of these metals:

  • Lead: mental lapses; learning disabilities, and kidney damage.
  • Cadmium: negative effects on the kidney, liver, and gastrointestinal tract.
  • Arsenic: negative effects on the kidneys and central nervous system, as well as skin poisoning.

Contaminated historic fill is usually discovered during a Phase I & II Environmental Site Assessment (ESA) or during earth moving activities. Phase I ESAs may identify where the presence of historic fill is likely and a Phase II ESA will confirm any contamination present. Once contaminated historic fill is found several options are available to the remediate the area, depending on the site’s intended use. For instance, a more stringent cleanup plan may need to be developed if the site was a planned residential community versus an industrial site.

Remediation of historic fill can be accomplished in numerous ways. Often the first step would be to register the site with the state’s Brownfield Redevelopment or the Voluntary Cleanup Program. The goal of remediation is to eliminate preferential exposure pathways to humans and to lower the contaminant concentration levels below a standard that is no longer considered a risk to human health that is typically set by the state’s governing agency. Environmental consultants often negotiate with the regulatory agency on behalf of a client and then develop a clean-up or management plan for the site. Excavating and disposing of the contaminated fill then backfilling with regulated material is effective; unfortunately, this is often the most costly and least sustainable method. Other methods of remediation include:

  • DEED Restrictions – Ensure that any future use of the site is limited to industrial or commercial use;
  • Environmental Caps – Impermeable constructed boundaries that can ensure contamination will not leach any farther;
  • Active Remediation – such as in-situ chemical oxidation, bioremediation or thermal remediation, which applies extremely high temperatures to the contaminated area to thermally remediate the contaminants.

Element Environmental Solutions (E2S) has dealt with a historic fill issues on many projects. Historic fill was suspected during a Phase I Environmental Site Assessment of the Homes at Thackston Park project located in York, PA. Prior to redevelopment, the site was previously a dry cleaner and a city park. The park was once the area of row homes that were condemned by the City of York in 1969. A geophysics investigation identified multiple areas with non-native soils and anomalies. During the site characterization, fill material was identified in geotechnical borings across the site. This fill material was used to level and grade the site many decades ago. From an environmental standpoint there were two main concerns: an isolated area containing elevated concentrations of lead located north of the former structure and mercury concentrations that did not exceed the Statewide health standard for soil, but failed preliminary indoor air quality screening models. An environmental cap was utilized at Thackston Park to manage the historic fill, as well as other contaminated soils on site. The historic fill was removed from the impacted area and placed in the deed restricted greenspace area beneath the environmental cap. Sub-slab vapor mitigation systems were installed in each unit to eliminate any indoor air quality concerns. The cleanup has since been approved by PaDEP and has met all Statewide Health Standard levels for all contaminants present at the site.

Another project located in Lancaster County contained a large area of historic fill material containing unsafe levels of arsenic and lead. This site is interesting because for many decades it was an undeveloped agricultural field. There was no evident reason to suspect fill material on site. Shortly after site work began, contractors came across a significant amount of fill material that was not suitable for compaction. A neighbor indicated that low-lying areas of the site were leveled using municipal waste ash in the late seventies. After initially hauling off several triaxle loads of contaminated material, which cost the developers $40,000 in offsite disposal, the construction managers contacted Mark T. Smith, PG to investigate and develop a plan to manage the contaminated fill. Over 4,600 cubic yards of contaminated fill was discovered. Fortunately, the proposed site plan included areas of dedicated open space. Mark Smith went straight to the PaDEP after delineating the area to discuss managing the contaminated fill on site. His proposed plan included moving the fill material to the dedicated open space easement and using clean soil from that area for the retention ponds and site work. The dedicated open space was then deed restricted using an environmental covenant declaring that that area would remain open space. He ultimately saved the owner of the site over $400,000 by safely managing the fill on site and using available soils to backfill the excavation.

Sometimes there’s more to a site than meets the eye. Each project is different and, as seen above, you can’t always assume a site is free of environmental risks just because it was never developed. If you’re interested in learning more about how historic fill can be managed or remediated, contact us and Element will help you through the process.

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