CASE STUDY: Gasoline Remediation by the Persian Gulf

Mitigating human risk using source remediation.

Background

At an active bulk fuel storage facility in a city located in Eastern Saudi Arabia, about 60km inland from the Persian Gulf, historical spills and leaks had resulted in up to 3.0 m of gasoline floating on an unconfined, saline aquifer. The urban location required a secure, explosion-proof, low-impact solution that could adjust to seasonal water table fluctuations, withstand corrosion, and function without interfering with the facility’s daily operations.

Location: Eastern Saudi Arabia

Client: Oil & Gas Company

Duration: Ongoing, 3 Years

Project Value: $550,000 CDN

Geology: Unconfined Silty Sand Aquifer

Plume Size: Approx. 100 m2

Approach

The oil & gas company tendered the remediation project for competitive bid to four firms. IRSL partnered with a Middle Eastern Environmental Consulting Firm and, together, they were awarded the project based on their price and innovative approach. IRSL’s partner firm characterized the site. IRSL designed and optimized the remedial system using numerical modeling to maximize the capture zones while minimizing smearing effects and volumes of water requiring treatment.

Vacuum-enhanced Pneumatic Skimming

To contain and remove the LNAPL in the form of free-phase gasoline, IRSL, with their partner, implemented and continue to maintain and optimize a vacuum-enhanced pneumatic skimming system.

Applied Technologies

To capture and recover the gasoline from the surface of the water table, IRSL and their partner installed specialized pneumatic skimmers within 10 wells, in an area extending approximately 60 m2. The chosen system was based on a series of tests, including NAPL transmissivity tests, in select wells. They enhanced the recovery of LNAPL from each 10 cm diameter well using a low-vacuum system, which increased both the rate of recovery and area of influence.

Low Vacuum Enhancement

Intensive testing comparing the effect of the vacuum versus no vacuum indicated that the radii of influence increased from approximately 1 m to greater than 7 m under the vacuum conditions and increased the rate of recovery by 5-fold.

The above-ground vacuum system was housed in a sound-and-explosion-proof, secured container, which required less than 10 m2. A full-time engineer remains on-site throughout the year to continuously monitor, adjust, and optimize the system.

Challenges

  • Located in the city, and considered a high-risk site from a security perspective, the active bulk fuel facility’s rigorous health and safety regulations required working with the facility and loss prevention department to ensure the operating system was safe, sound-and-explosion-proof, and highly secured.
  • Potential for corrosion due to the highly saline groundwater required specialized materials to be used for the skimmers.
  • Seasonal fluctuations in the water table required constant monitoring to ensure optimal gasoline recovery.

Results

  • As a result of continuous optimization, the percentage of gasoline within the fluid recovered has been greater than 99.999% over the recovery period.
  • The NAPL plume has been contained and over 2,500 L of gasoline have been recovered from a 100 m2 area in less than two years.
  • Free product thickness in monitoring wells has decreased by over 90%.

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