Post-Remediation Performance Assessment at DoD’s Petroleum Impacted Sites

Mr. Tim Appleman | Naval Facilities Engineering Command and Expeditionary Warfare Center

ER-201582

Objective

Fifteen to twenty years ago, SERDP and ESTCP conducted many demonstrations of light non-aqueous phase liquid (LNAPL) removal and plume treatment technologies. Technologies, such as bioventing, dual-phase extraction, and natural attenuation, were demonstrated successfully to show that LNAPL could be removed and benzene, toluene, ethylbenzene, and xylenes (BTEX) plume migration could be controlled.

Based on that work, these technologies were successfully applied at many Department of Defense (DoD) sites. The expectation was that unlike chlorinated solvents, petroleum sites could be closed after a reasonable period of time in the same way that private underground storage tank (UST) sites were being closed. However, in a recent survey of Navy and Marine Corps site remedial project managers (RPMs), almost a third reported continuing remediation and long-term management challenges at petroleum sites.

At many of these sites, early DoD demonstrations of free product removal technologies, such as bioventing and bioslurping, were considered a success and considerable free product was recovered during each demonstration and subsequent full-scale application. However, in the longer term, many of these sites are still struggling to remove enough free product to meet U.S. Environmental Protection Agency (EPA) and state requirements of source control (product mobility) and plume treatment.

A review of post-remediation and long-term monitoring (LTM) data and some selective additional monitoring to evaluate residual risk are needed to accelerate the closure of these sites. The objective of this project is to help DoD make a stronger case for closure of legacy petroleum sites (or at least cessation of active free product recovery, which hundreds of DoD sites continue to do, despite the fact that the remaining free product is highly weathered and poses little risk).

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Technology Description

The team will use the LTM data evaluation at nine sites at Naval Air Station (NAS) Fallon and eight sites at Hill Air Force Base, followed by the supplemental American Petroleum Institute (API)-recommended testing of select soil samples at Site 2, NAS Fallon, to demonstrate the following: (1) After several years of active and passive remediation and long-term monitoring, most DoD sites with petroleum impacts have reached the economic limit of LNAPL recovery; (2) Remaining petroleum product in vadose and saturated zones at many sites is highly weathered over time and does not pose dissolution (leaching to groundwater) or volatilization (vapor intrusion) risk; (3) Although benzene sometimes exceeds Applicable or Relevant and Appropriate Requirements (ARARs), the benzene plume is stable at almost all sites; (4) At a few sites, managing the plume from petroleum additives (e.g., MTBE, 1,2 DCA, or EDB) at the perimeter of the plume is the only remaining risk; (5) State petroleum programs have site closure criteria that can be leveraged even at CERCLA sites. For example, the state of California has published the “Low-Threat Underground Storage Tank Case Closure Policy,” and most states have similar guidance. In Nevada the Division of Environmental Protection has issued risk-based closure guidance that will be applied at NAS Fallon; (6) DoD can use relatively simple tests developed by API to show that the weathered product poses no significant risk at most sites.

ER-201582_project graphic

E-flux Carbon Trap being installed in the field

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Benefits

The results of this study will be used to provide guidance to NAS Fallon and other DoD sites on the use of LTM data and risk-based evaluation of remaining free product to make a renewed case for site closure or some other alternatives that might result in cost savings, including a change in remediation techniques (for instance, from an active to a more passive remediation approach), a reduction in the number of samples taken at sites, or a reduction in the frequency of sampling. (Anticipated Project Completion - 2018)

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Points of Contact

Principal Investigator

Mr. Tim Appleman

Naval Facilities Engineering Command and Expeditionary Warfare Center

Phone: 805-982-4798

Program Manager

Environmental Restoration

SERDP and ESTCP

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