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Underground Storage Tanks (USTs)

Expedited Site Assessment

The expedited site assessment (ESA) process is a framework for rapidly characterizing UST site conditions for corrective action decisions. This concept has been described with other names including: accelerated site characterization, rapid site characterization, and expedited site investigation. ESA's have been made possible by the recent development of improved, cost-effective methods for rapid sample collection and field analysis of soil gas, soil, and groundwater. Where appropriate (or necessary) conventional sampling and analytical methods can be used to augment the ESA process. An ESA is typically conducted in a single mobilization that can last several days and is distinguished by the following features:

  • Field-generated data and on-site interpretation
  • Flexible sampling and analysis
  • Field presence of senior staff empowered to redirect the investigation in response to new data

The ESA process contrasts with conventional site assessments in which a significant amount of data analysis and interpretation is completed off-site at a later date. As a result, conventional assessments:

  • Take weeks or months to produce a preliminary report
  • Require several phases of investigation often with repeated mobilizations
  • Delay effective corrective action decisions

Because of their recent development and the rapidly evolving nature of ESA tools and techniques, EPA has prepared a guidance manual to help state regulators understand the ESA process so that they can more effectively oversee and promote ESA's to improve the remediation process.

EPA has produced an extensive manual that describes various tools that may be used in the ESA process.