CH2M shared newly developed guidance on natural source zone depletion (NSZD) during a technical webinar with industry leaders in the oil and gas, manufacturing, chemicals and transportation sectors. NSZD is a new term that describes naturally occurring processes that biodegrade or reduce petroleum, non-aqueous phase liquids (NAPL) in the subsurface. Petroleum NAPL can seep into soil from oil spills or leaks, resulting in potential groundwater contamination and remediation challenges.

Matthew Sutton, President of CH2M’s Private Sector business stated, “Bringing new technology applications to more effectively remediate petroleum contaminated sites demonstrates the thought leadership and practical application clients rely on us for. Using our top-level expertise, in the form of technical guidance and expert consulting gives our clients the edge in operational performance and improving the bottom line.”

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. Previously unaccounted for with MNA, NSZD biodegradation processes result in generation of gases. When converted to source zone reductions, these gases represent a far more significant mass loss mechanism than previously understood.

Taking into account and quantifying the NSZD processes represents a paradigm shift in the way petroleum NAPL contaminated sites are remediated and managed. CH2M has collected extensive data demonstrating rates of petroleum that can be naturally degraded. These rates are often equal to or greater than some active remediation systems, establishing that NSZD monitoring alone, or in combination with an active remediation, can be used to more cost-effectively remediate a site.

Recognizing the high value of emerging NSZD science to clients early on, CH2M was one of the first to work with a prominent research university to deploy new monitoring methods and present new information to regulators, including endorsing NSZD as a viable remedial option and or a benchmark for other remediation efforts.

With extensive technical and field experience in NSZD, CH2M Principal Technologist Tom Palaia, who led the webinar, and colleagues Laura Gergely and Jeff Fitzgibbons 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. CH2M petroleum remediation experts also contributed to petroleum remediation technical literature for the Interstate Technology & Regulatory Council and CRC CARE in Australia.