SUMMARY OF THE REMEDIATION TECHNOLOGIES DEVELOPMENT FORUM
NAPL CLEANUP ALLIANCE
CASPER REFINERY WORKING GROUP
April 3, 2001
1:30 p.m.Ė3:00 p.m.
On April 3, 2001, the following members of the Remediation Technologies Development Forumís (RTDFís) Refinery Alliance met in a conference call:
Eva Davis, U.S. Environmental Protection Agency (EPA)
Jeff Hostetler, TriHydro Corporation
Randy Jewett, Texaco Group
John Meyers, ThermoRetec Consulting Corporation
Ali Tavelli, Wyoming Department of Environmental Quality
Kent Udell, University of California at Berkeley
Also present was Christine Hartnett of Eastern Research Group, Inc. (ERG).
The Casper Refinery Working Group has formed to address contamination at a refinery site in Casper, Wyoming. Ali Tavelli said the workgroup is in the process of defining goals and developing a strategy for site investigation and cleanup. She said that John Meyers used an interesting approach at a site in Colorado. She asked Meyers to describe his work so that call participants could determine whether similar techniques should be employed at the Casper site.
INVESTIGATIONS PERFORMED AT A SITE IN COLORADO
Meyers noted that a cleanup project is being performed for two active
refinery sites near Denver, Colorado. (The refineries are next to each other,
and are being treated as one site.) The refineries, which have been operational
since the 1930, have a combined capacity of about 90,000 barrels per day. A
slurry wall has been installed and containment systems have been constructed.
Despite these remediation efforts, contaminant concentrations in downgradient
ground water are above regulatory standards. Therefore, in 1998, the site owners
entered into a joint consent order with the state and EPA Region 8. The owners
agreed to implement interim measures that: (1) prevent contaminants from migrating
off site, and (2) recover free product to the maximum extent practicable. Meyers
said that his discussion would focus on efforts to accomplish the latter objective.
Before initiating any investigatory or cleanup activities, Meyers said, the site owners worked with regulatory agencies to identify clear remediation goals. Rather than focusing on non-aqueous phase liquid (NAPL) removal, Meyers said, the decision was made to focus on reducing NAPL mobility. Once a goal had been chosen, a targeted investigation was performed to glean more information about the siteís subsurface conditions. This investigation had four objectives: (1) estimate the nature and extent of free product, (2) identify product type and distribution properties, (3) estimate the volume and mobility of free-phase product, and (4) design a conceptual product recovery system. Meyers described the techniques used during the investigation and the conclusions that emerged. These are the highlights of his discussion:
Mobility = (Oil conductivity)
ī (True thickness of product in the soil)
Meyers said that the new maps allow investigators to identify areas with high saturation levels and decent mobility. This gives investigators a better chance of targeting important areas for remediation. The investigation has helped site owners, regulators, and remediation designers understand the magnitude of the problem at the site. Now that the problem is better quantified, it is easier to determine what can reasonably be accomplished during cleanup. Meyers said that the product mobility curve will be used to select a cleanup endpoint. It is crucial to pick an endpoint before remediation efforts are initiated, he said. Otherwise, how will investigators know when to shut off a remediation system? The NAPL evaluation also allowed investigators to make product recovery performance predictions that will provide a benchmark for comparing to actual performance.
Meyers said that efforts have been initiated to move forth with remediation activities at the Colorado site. After several different remediation schemes were evaluated, water flooding was selected as the preferred choice. The systemís design is being finalized and a pilot study will be initiated soon. Udell said that he is eager to see what results are obtained using an ambient water flood. It may be interesting, he suggested, to follow up with a hot water flood.
PATH FORWARD FOR THE CASPER REFINERY SITE
Tavelli asked whether the site investigation methodologies that Meyers discussed would be useful at the Casper site. Call participants reached a consensus that using the ROST‘ tool was a good idea: it is relatively cost effective, relatively simple to implement, and it provides good qualitative data. It would also be useful, they said, to collect cores in the areas that are shown to have intense fluorescence. Obtaining ROST‘ data and correlating it with oil saturations will allow investigators at the Casper site to refine their understanding of the subsurface.
Call participants also listed some other analytical techniques that might have merit:
Call participants agreed to think more about the analytical techniques that would be best to use at the Casper site. In the meantime, Tavelli and Hostetler will put together a draft statement summarizing the workgroupís goals. This will be circulated to workgroup members for approval before being sent to the NAPL Cleanup Alliance members. Call participants talked briefly about the goals, and agreed that remediation will need to be accomplished in multiple stages at the Casper site. First, an active remediation technology will be needed to remove large quantities of NAPL to ďcut the head off the dragon.Ē Then, once a certain endpoint is reached, the remediation system will be shut off and natural attenuation will be expected to reduce contaminants to concentrations below maximum contaminant levels. Two important questions will need to be addressed: (1) What endpoint should be used? and (2) How long a timeframe is reasonable to accomplish the entire cleanup?
Hostetler said that the workgroup needs to produce a work plan for the Casper site within the next couple of months. By the end of the year, he hoped, site investigation would be completed, results would be compiled, and potential remediation technologies would be identified.