The soils at a privately-owned petroleum exploration/production pipe storage yard in Mount Pleasant, Michigan, were contaminated with technologically-enhanced naturally occurring radioactive material (TENORM). The owner wanted the property cleared of contamination concerns so that it would be available for alternative reuse options, including potential residential development. The owner had attempted a voluntary corrective action in the early 1990s, but subsequent investigation of the Site by the Michigan Department of Environmental Quality (MDEQ) found lingering contamination problems in site soils.
The goal of the project, with partial Department of Energy Fossil Energy support, was to demonstrate a cost-effective approach for addressing TENORM-contamination problems characteristic of the oil and gas industry. In the fall of 1998, a Triad-based field effort was initiated that attempted to address site investigation, remediation, and close-out requirements in one field deployment. Three different real-time measurement technologies were used. A dynamic work strategy was developed that targeted site investigation work to areas of concern as they were encountered, and that allowed the characterization work to transition seamlessly to excavation and removal, and then to site close-out data collection. MDEQ representatives were involved in the systematic planning and implementation. The resulting effort selectively removed contaminated media that exceeded state guidelines and successfully "closed" the Site, clearing the Site for unrestricted reuse.
|Site Name||Lease Management, Incorporated|
|Location||Mount Pleasant, MI|
|Project Lead Organization||Private Owner|
|Project Lead Type||PRP Lead|
|Regulatory Lead Program||Voluntary Cleanup Program|
|Triad Project Status||Field Program Completed|
|Reuse Objective Identified||Yes|
A pipe storage yard is maintained by Lease Management, Inc. in Mount Pleasant, Michigan. The company specializes in supporting the oil and gas industry. The 3-acre yard was used to store and refurbish piping and associated equipment used for oil and gas exploration and production purposes. Some of the equipment was contaminated with TENORM-bearing scale. The scale was knocked loose and deposited across the Site through the normal process of handling piping and equipment. The scale characteristic of this Site contained very high levels of radium. By 1991 the owner was aware of the problem and attempted to remove contaminated material (piping and soils) from the Site. In 1997, MDEQ performed a cursory site survey and identified additional locations across the Site where elevated gamma activity was present.
The owner of the Site wanted to clear the Site of contamination concerns to allow re-use. One of the options under consideration was the development of residential units on the property. The State of Michigan has issued guidelines for free-releasing TENORM-contaminated soil media that is defined as a 5 picocuries per gram (pCi/g) activity concentration requirement averaged over a 100 square meter area (MDEQ Drinking Water and Radiological Protection Division, Cleanup Guidelines for Radium-226 to Allow Release for Unrestricted Use). The standard remediation option for TENORM-contaminated materials is removal and disposal at an appropriate facility. In many cases this means out-of-state disposal, which results in high volumetric remediation costs.
The "traditional" analytical method for quantifying radium-226 and/or radium-228 activity concentrations in soils is through collection and analysis of discrete ex situ samples via gamma spectroscopy. There are a number of commercially available real-time methods suitable for field deployment at sites contaminated with radium-226 and/or radium-228. For this Site, three different methods were used, each serving a particular function. They included:
Elevated radium-226 activity concentrations were encountered in surface soils at many different locations scattered across the 3-acre Site. A more detailed analysis of gamma walkover survey data sets identified five distinct areas where radium-226 activity concentrations likely exceeded the State of Michigan's guidelines of 5 pCi/g averaged over a 100 square meter area. Soils from these five areas were selectively scraped with a combination of a front-end loader and a field crew using shovels, supported by real-time measurements. The excavation produced approximately 9 cubic yards of material for disposal. Post-excavation waste characterization of excavated soils slated for disposal found an average radium-226 activity concentration equal to 18 pCi/g. Post-excavation characterization of the Site confirmed that the cleanup guidelines had been achieved, a conclusion the State of Michigan concurred with.
The objective of the project was to identify and remove soils contaminated with TENORM (technologically-enhanced naturally occurring radioactive material;) resulting from oil and gas production activities. Existing contamination prevented reuse of the Site for other purposes.
There are several benefits associated with this project:
The investigation, remediation, and site close-out activities were compressed into one field deployment that lasted several days. The work resulted in a very precise removal of contaminated material, providing the site owner with significant disposal cost savings by minimizing waste streams. The project team estimates that the use of real-time measurement techniques resulted in an analytical cost savings of more than 50%.
The Conceptual Site Model (CSM) for the Site was based on interviews with the site owner, a site reconnaissance, and a review of past practices at the Site. The CSM postulated that contamination at the Site was the product of past pipe and equipment handling activities. Given the source of the contamination, and the immobile nature of contaminated scale, the CSM assumed that contamination would be limited to surface or near-surface soils. The CSM further assumed that contamination could potentially be found anywhere across the Site. The primary question to be answered was whether existing soils at the Site met State of Michigan TENORM release requirements. If a particular area did not, a related question was what soils would need to be removed to bring the Site into compliance. The principal source of uncertainty in answering these questions was the lack of data regarding the contamination status of site surface soils. Representatives from the State of Michigan participated in some of the planning sessions, and concurred with the CSM. The systematic planning process yielded a dynamic work strategy that relied on real-time measurement systems and on-site decision-making to complete site characterization, identify soils requiring excavation, support the excavation work, and acquire the data required to demonstrate cleanup requirement compliance in one field effort. The dynamic work strategy included a methods applicability study at the initiation of the project to ensure that the real-time methods would meet site-specific performance requirements.
The project team consisted of staff from Argonne National Laboratory (ANL), who directed the work; the State of Michigan, who provided regulatory oversight; a small analytical company (NORM Instruments and Services, Inc. [NORM ISI]), who deployed one of the real-time methods; and the property owner, who paid for the remediation and provided field labor. The technical expertise included TENORM regulatory experience, health physics, instrumentation, geohydrology, and sampling program design.
The dynamic work strategy was designed based on four analytical technologies that focused on managing different aspects of uncertainty while allowing decision-making in the field. These technologies were:
The dynamic work strategy used the following sequence:
The decision logic was designed to determine whether specific areas exceeded cleanup requirements. The GWS surveys identified areas of potential concern. HPGe measurements confirmed whether they were of concern or not. The decision logic was structured so that field crews did not demobilize until the team was confident that cleanup requirements had been achieved.
The GWS provided complete, cheap, fast indications of the presence and distribution of surface contamination. Gross activity, however, does not provide quantitative information about the presence and activity concentrations of specific radionuclides.
The NaI was used to assist in the interpretation of GWS data sets. The NaI provided relatively accurate radium-226 activity concentrations in surface soils for specific locations using 5-minute in situ measurements. The NaI, however, was subject to interference effects and so data were used with care.
The in situ HPGe measurements provided relatively definitive activity concentration estimates for radium-226 that could be compared directly to cleanup requirements for specific areas of concern. HPGe measurements, however, are much more expensive than either than GWS or NaI data sets, and require a highly-trained technician to be performed properly.
Off-site fixed laboratory gamma spectroscopy was used as a quality control check on NaI data at locations selected by the project team.
Method applicability studies were built into the overall set of field activities for both the GWS and NaI systems. The purpose of the applicability studies were to demonstrate system performance and identify any site-specific performance issues that might be of concern for the methods. The method applicability study used GWS results to target specific locations across the site for measurement by the in situ NaI differential counter, and for subsequent sampling and off-site gamma spectroscopy analysis. The off-site gamma spectroscopy samples were actually analyzed by both Argonne and the State of Michigan. The results from these analyses indicated no bias in the differential counting system, and demonstrate that the variability observed between NaI and Argonne results was no greater than the variability observed between Argonne and State of Michigan split results. The results were also used to develop site-specific decision levels that could be applied to the balance of the GWS data sets. QC work for both the GWS and NaI differential counting systems was front-end loaded as part of the methods applicability study, including multiple replicate analyses to estimate expected measurement errors and practical detection limits.
Data from the GWS, NaI, and HPGe systems were managed in the field and used to support the overall dynamic work strategy applied to the Site.
TQRS not available
GWS data quality was ensured by:
NaI data quality was ensured by:
HPGe data quality was ensured by:
In addition, MDEQ performed duplicate analyses for selected sample splits to monitor quality of off-site gamma spectroscopy results
Real-time data management and analysis were applied in the field on laptops through the use of spreadsheets and ArcView GIS software. The GWSs generated more than 20,000 individual measurements. Approximately 150 in situ measurements were made with the NaI differential counting system. Approximately 10 in situ measurements were made with the HPGe.
Field work was conducted in October 1998.
|The Application of Adaptive Sampling and Analysis Program (ASAP) Techniques to NORM Sites (5.8 MB)|
To update this profile, contact Cheryl T. Johnson at Johnson.Cheryl@epa.gov or (703) 603-9045.