Posted by & filed under Environmental, Water & Wastewater Facilities Operations.

Broadbent was contracted by a major petroleum and energy company to provide a third party review and preparation of a Site Conceptual Model for a former aerospace facility in the Central Valley of California. Analysis of historical data indicated that former site operations activities had resulted in contaminant impacts to groundwater. Primary contaminants of concern (COCs included volatile organic compounds (VOCs). On the site, groundwater occurs at approximately 40 feet below ground surface (bgs) and flows towards the east. A soil vapor extraction (SVE) system was installed in 1999 and operated through 2000. A groundwater extraction and treatment system (GWETS) was also installed in 1999 and has operated continuously, since then. The objective of the scope of work performed was to prepare a detailed conceptual site model (CSM) with the intention of potentially evaluating remedial alternatives that would enhance site cleanup and/or reduce or eliminate the necessity of continuous treatment of the GWETS.

Broadbent reviewed all available site documents and prepared a detailed CSM based on this review. During the site review, several data gaps were identified that the previous and current consultants had not yet addressed. These data gaps included:

  • inadequate understanding of Site hydrogeology,
  • inadequate evaluation of groundwater gradient,
  • inefficiency of the operating GWET system,
  • insufficient understanding of regional and/or offsite conditions,
  • insufficient information regarding nearby receptors,
  • and a lack of current evaluation of the site remedial strategy.
Site Conceptual Model of Groundwater

Proper attention to policy and procedures when evaluating a site conceptual model of groundwater identified a number of data gaps in previous reports.

Broadbent presented the findings of this CSM during a meeting attended by project stakeholders, as well as the current Site consultant. During this meeting, many of the elements presented in the CSM were acknowledged by both the client and the current consultant. A shutdown of the GWET system was scheduled, per Broadbent’s recommendation. Many other action items, for future site activities, were also planned. These included additional site research and regulatory meetings and negotiations. The work performed by Broadbent changed the current Site strategy and provided the client the necessary background to make informed decisions regarding ongoing remediation and potential future work at the Site.

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