Griffin Dewatering

Griffin Pioneers Successful Treatment of EPA’s Contaminants of Emerging Concern

Project Background and Challenges

A global general contractor was demolishing and building a deicing facility for the city’s international airport. The project consisted of demolishing of an existing Stormwater and Deicing Collection Facility and constructing of a new Stormwater and Deicing Collection Facility as part of ABIA Terminal/Apron Expansion Project in Austin, TX. The footprint of the shored excavation (soil nail & shotcrete) was approximately ±250ft by ±200ft. The static groundwater was approximately 28ft below existing ground and had to be lowered 2ft below the deepest subgrade excavation to a depth of 34ft.

The groundwater at the Texas site was found to be contaminated with perfluorinated alkyl acids (PFAAs) which are among EPA’s list of emerging contaminants.

Due to their unique properties (for example: oil, water and heat repelling properties) PFAAs are widely used in commercial and industrial applications such as packaging material, coatings, water-proofing and stain-proofing. This stable, persistent and ubiquitously distributed class of organic chemicals have been found to have numerous toxic effects including tumor induction, immunotoxicity and neurotoxicity.

The PFAAs family of chemicals is made up of various long and short chain compounds such as Perfluorobutanesulfonic acid, Perfluorohexanesulfonic acid, Perfluoroheptanoic acid etc.

Short chain PFAAs compounds are especially challenging to remove, and most rely on expensive technologies such as reverse osmosis for the treatment of short chain PFAAs. Griffin applied an innovative mix of filtration media to cost effectively treat for both long and short chain PFAAs. The treated water was comprehensively tested. PFAAs were reduced to non-detect levels at the end of the treatment train. To ensure early detection of any media breakthrough, and to prevent any out of compliance discharges, Griffin incorporated the use of lead-lag series configuration in our treatment methodology.

Griffin’s Solution

Griffin installed a combination Deep Well and Wellpoint Dewatering System(s) and successfully lowered groundwater to the required depth for construction to continue. Griffin also designed and installed a water treatment system to treat the contaminated total flow rate of approximately 500 gpm from dewatering system before discharging to the sanitary sewer. Griffin off-loaded, hydro-tested, installed and started-up the treatment system. On-site training was provided to the designated daily operators. Griffin provided troubleshooting and maintenance assistance as requested by the client. At the end of the project, Griffin removed and disposed the used media, decommissioned and demobilized the system off the site.

Summary information:

  • Description: Project included demolishing of an existing Stormwater and Deicing Collection Facility and constructing of a new Stormwater and Deicing Collection Facility as part of ABIA Terminal/Apron Expansion Project.
  • General Contractor (GC): Hensel Phelps Construction Company
  • GC Point of Contact: Blair Kelly, Project Manager, 512-593-5628)
  • Total Dewatering & Treatment Cost: $1,150,000.00
  • Location: Austin Bergstrom International Airport (ABIA), Austin, TX
  • The Footprint of the Excavation: Approximately ±250ft by ±200ft
  • The Shoring System: Soil Nailing & Shotcrete
  • The Subgrade: Approximately 32ft below existing ground level (El. 458.5)
  • Dewatering System Installation Start / End Dates: 02-08-2016 / 3-21-16
  • Initial Groundwater Depth: Approximately 28ft below existing ground level (El. 462). Based on the water samples collected from dewatering wells on 02-12-16 it was determined that the groundwater was contaminated with Perfluorobutanesulfonic acid a product that had been used for deicing operation at old facility that was demolished.
  • Dewatering System(s): Deep Well & Wellpoint System(s)
  • Drilling Method: Bucket Auger / Wash Rotary
  • Borehole Diameter: 24-inch / 6-in
  • Number of Wells / Wellpoints: 20 each / 70 each
  • Depth of Wells / Wellpoints: ±45ft / 20ft
  • Well Casing/Screen Diameter: 6-inch PVC Riser & Screen / 2-inch PVC Wellpoints
  • Electric Submersible Pump: 1 to 3 horse power (HP) / Wellpoint Pump
  • Total System Flow Rate: ±500 gallons per minute (GPM)
  • Water treatment System Installation Start / End Dates: 04-12-2016 / 04-20-16
  • Dewatering & Treatment Systems Removal Date: 12-29-2016

 

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