Risk-based zoning strategy for soil remediation at an industrial site

After determining at an early stage of the project that the future land use of this New Jersey chemical manufacturing site remain industrial in nature , the site was zoned according to risk. The chemicals of concern (COCs) at the site included relatively low levels of mono- and polynuclear aromatic h ydrocarbons, chlorinated aliphatics, as well as other volatile and semivola tile compounds. Direct human exposure scenarios were the key to the mitigat ion of risks related to soils because the groundwater migration pathway was already interrupted using groundwater recovery. A focused remedial strateg y was developed to ensure that the exposure pathways (inhalation, ingestion , and dermal contact) are alleviated and the remedial measures are protecti ve to the workers operating and/or maintaining the site. The risk evaluatio n process included a preliminary risk assessment (Tier 1) based on a compar ison with pertinent soil cleanup criteria, a prioritization analysis to ran k zones, chemicals and pathways of concern, and an application of the Risk Based Corrective Action (RBCA) approach (Tier 2) for construction worker ex posure scenario. The risk assessment identified selected areas that would b enefit from remedial actions. Prioritization Analysis classified the site i nto five high-priority (comprising 97% of the total health-biased risk), th ree medium-priority (contributing to remaining 2 to 3% of the risk), and ad equately protected areas. The boundaries and volumes of affected areas were delineated based on confirmatory soil sampling sind statistical analyses. The remedial technologies selected for the site have achieved appropriate r eduction in risk to comply with all State regulations and include (in addit ion to the institutional controls): Capping the site where only immobile semivolatile contaminants are present Excavation and on-site treatment of the soils impacted by volatile organic compounds through ex situ low temperature desorption, or alternative "biopi le" treatment and natural attenuation, and Excavation and off-site disposal of limited volumes of soils This risk-based, integral approach helped identify the real significance of contamination present at the site and facilitated the development of suita ble and adequate remedies. Had not if been for this approach, the mere comp arison with soil cleanup criteria would have unnecessarily resulted in deno ting all areas as nuisance contributors, and thus requiring some actions. N ew Jersey Department of Environmental Protection (NJDEP) has approved this approach and contributed to its accomplishment.