Refinery / LNAPL Remediation

Construction of Interceptor/Barrier Trench System for Remediation of LNAPL
Oklahoma Refinery SiteRefinery / LNAPL Remediation

StanTech was hired by the facility to design, supervise installation, monitor, and maintain a light non-aqueous phase liquid (LNAPL) interceptor trench system consisting of two trenches.  The primary purpose of the trench system is to recovery LNAPL, thereby preventing potential impact to a nearby creek.  Both trenches are installed at locations designed to prevent the inadvertent discharge of contaminants to the creek.

The first trench (~250’ in length), located just downgradient of LNAPL saturation, consists of a gravel-filled recovery trench equipped with automated recovery pumps to capture and remove LNAPL from the subsurface.  The second trench (~700’ in length), installed at a location further downgradient, is constructed in a similar manner, and also contains an impermeable liner that serves as a barrier.

Additional activities conducted by StanTech include drilling and delineation activities prior to trench design and installation; ongoing system operational checks and maintenance; performance monitoring; and area groundwater gauging and sampling.  As part of the RCRA Facility Investigation (RFI), StanTech also conducted a Screening Level Ecological Risk Assessment (SLERA) to assess impact to creek sediment and surface water for evaluation of potential risks to the environment.

Major activities completed by StanTech for the construction and operation of the LNAPL recovery trenches included:

  • Preparation of a delineation work plan for determination of lateral and vertical extent of impact.
  • Installation of soil borings using the direct push technique and collection of soil samples for analysis of contaminants.
  • Installation and associated permitting of a horizontal boring beneath a railway.
  • Assimilation and tabulation of soil data and Quality Assurance/Quality Control (QA/QC).
  • Design of two LNAPL interceptor trenches and preparation of work plans for approval by the Oklahoma Department of Environment Quality (DEQ).
  • Construction oversight for two LNAPL interceptor trenches in accordance with approved specifications.
  • Trench system pilot testing and system modifications.
  • Preparation of system installation reports for submittal to the DEQ

StanTech continues to conduct monthly remedial system monitoring to ensure that the system and its mechanical components are operating efficiently and effectively.  Additionally, StanTech conducts quarterly groundwater sampling and gauging to monitor system performance and effectiveness.



Oklahoma City – Corporate Office
4300 N. Lincoln Blvd.
Oklahoma City, Oklahoma 73105-5106
(800) 725-8378
(405) 424-8378
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