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Applying a new technology to petroleum-contaminated sites

Natural source zone depletion technology can optimize site remedies and reduce costs.

Natural source zone depletion (NSZD) is the new technical term for naturally occurring biodegradation processes that reduce petroleum, non-aqueous phase liquids (NAPL) from the subsurface. Petroleum NAPL can seep into soil from oil spills or leaks, resulting in potential groundwater contamination and remediation challenges.

While biodegradation is ubiquitous at petroleum release sites, NSZD biodegradation processes are most significant within the source zones of the contaminating petroleum liquids. In this aspect, it is distinctly different from conventional monitored natural attenuation (MNA) remedies, where contaminant degradation occurs outside the source zone in dissolved plumes.

Carbon dioxide flux chamber collecting NSZD data
Carbon dioxide flux chamber
collecting NSZD data

Early on, CH2M recognized the high value of NSZD science and began working with a prominent research university to deploy new monitoring methods in the field and present new information to regulators, including endorsing its consideration as a viable remedial option and benchmark for other remediation efforts because it is critical to understanding the short and long term fate of hydrocarbons.

NSZD processes represents a paradigm shift in the way petroleum NAPL contaminated sites are managed and remediated. CH2M has collected extensive data demonstrating typical rates of from 200 to 2,000 gallons of petroleum that can be naturally degraded per acre of NAPL source zone per year. These rates are often equal to or greater than other active remediation systems, establishing that in this new paradigm, NSZD monitoring alone, or in combination with an active remediation, can be used to more cost-effectively remediate a site, yet still protect human health and the environment.

CH2M has extensive technical and field experience in NSZD, including site-specific field NSZD monitoring at more than 20 sites, and numerous technical conference presentations. CH2M remediation experts were lead authors of the new American Petroleum Institute Publication, Quantification of Vapor Phase-related Natural Source Zone Depletion Processes—an emerging industry standard which will serve to build technical consistency in this new field. We also contributed to petroleum remediation technical literature in publications for the Interstate Technology & Regulatory Council and CRC CARE in Australia.

Much useful and game-changing technology, like NSZD monitoring, emerges from universities but often lacks a champion in practice. Through the innovative focus of our technology leadership function, we recognize the value of emerging science and seek to advance its application. With the underlying goal to bring useful technology to practice more rapidly, CH2M is a steward of good science and a champion for change that helps to better manage remediation sites.

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