Buffalo, NY: Operable Unit 2 Remediation

Buffalo, NY: Operable Unit 2 Remediation

Project Description

Significant Project Features:

  • Continuous Community Air Monitoring Program (CAMP) and erosion controls using best management practices (BMPs) throughout the duration of site activity
  • Prior to starting ISS, GSI was required to clear the 31 acre site of all vegetation and remove any asphalt, construction debris, building materials, process piping and/or foundation piles.
    • Off-site disposal of all clear & grub materials
    • Processing and sizing all concrete and asphalt debris to 3-inch minus.
    • Cleaning and disposal of process piping.
  • Shallow soil mixing via bucket mixing methods introducing a Portland cement grout.
    • Treatment of approximately 240,000 Cubic Yards (CY) of grossly contaminated materials
    • Maximum depth of 16-feet below ground surface
    • Target Unconfined Compressive Strength (UCS) of 40 pounds per square inch (psi)
  • Installation of a perimeter low permeability barrier
    • Treatment of soil extending to the underlying clay confining layer for hydraulic control along the north, east and western extents of the stabilization footprint
    • Introduction of a Portland cement grout and bentonite
    • Target Permeability of 1×10-6 cm/sec
  • Installation of a new access road for the Buckeye Terminal consisting of:
    • Utility installation – domestic and fire water, sanitary, gas, electrical and communication
    • Access Road pavement (approx.. 30,000 SF)
    • Access Road gate, operators, security and fencing.
  • Stormwater Management area including sand filter and associated drainage structures
  • Excavation, disposal and backfill of Hot Spots identified during site characterization
    • Excavation of approximately 1,300 CY of impacted, non-hazardous soil
  • Installation of a 1 foot clean cover system above stabilized soils
    • Clean cover system consisted of a demarcation layer, 6-inches of Type 3 subbase and 6-inches of top soil.

Background:

The ExxonMobil former Buffalo Terminal consisted of the refinery and terminal operations south of Elk Street encompassing approximately 89 acres. To address the environmental conditions, ExxonMobil entered into a Brownfield Site Cleanup Agreement with the NYSDEC. The remedial action of OU-2 consisted of ISS of certain leachable lead-impacted, petroleum, and metals impacted soils, followed by the installation of a clean soil cover system. Impacted soils were treated from the ground surface to the underlying clay confining stratum or 5-feet below grade, dependent on the levels of grossly contaminated media (GCM).

Project Objectives:

Geo-Solutions, Inc. (GSI) was contracted by KR Redevelopment to serve as the prime contractor for the removal of underground obstructions and abandoned utilities during pre-clearing activities, completion of in-situ stabilization via bucket mixing methods, processing of excavated concrete and asphalt, installation of the new Buckeye Terminal access road and utilities, and placement of the soil cover and drainage system. These measures were designed to immobilize and contain impacted soil and groundwater within the site boundaries.

Description of Work: 

Following C&G activities, GSI removed subsurface obstructions from within the footprint of the treatment area(s) using excavators and demolition hammers. Included in this scope was the removal of asphalt, concrete, abandoned utilities, and structures related to the former refinery operations.  Reinforced concrete building and tank pad foundations along with a variety of fill material including bricks, steel structural members, wood, petroleum products, and other types of debris were encountered at various depths.  A variety of known, unknown, active and abandoned utility lines were encountered within the specified treatment area. These lines were either terminated or solidification was performed above and alongside the utility.  Active utilities servicing the existing Buckeye Terminal were capped and relocated along the newly installed access road alignment.

The ISS included the stabilization of approximately 240,000 CY of impacted soil. The 31 acre site was divided into approximately 4,400 cells measuring 20-feet wide by 15-feet long. The ISS extended to depths determined by the Engineer during the site characterization phase. GSI achieved a maximum depth of 16-feet below ground surface (bgs) with an average depth of 6-feet bgs.

Utilizing GSI’s custom built continuous mix plant, a total exceeding 5-million gallons of cement grout was mixed and pumped to the various cells. Introducing a mixture consisting of 4 or 5% PC by weight of soil, target unconfined compressive strength of the stabilized material was 40 psi at an age of 28-days.

A component of the site restoration included the installation of a 120 ft. wide by 12,000ft. long stormwater management area containing a surface sand filter and associated drainage structures.  The sand filter was installed to a depth of 7-feet bgs.  The sand filter is located along the southern extents of the property, and will collect, filter and discharge the stormwater to the Buffalo sewer.  A clean soil cover system was installed across the remainder of the site consisting of the placement of a demarcation fabric, subbase material and topsoil. Subbase material was placed in lifts and compacted to 95% density whereas all topsoil area(s) were seeded.

Project Challenges

 Removal of large quantities of concrete, underground obstructions and abandoned utilities during pre-clearing activities.

  • Relocation of the Buckeye Access Road and utilities while maintaining full functionality;
  • Continued evolvement of scope based on changing field conditions and various conflicts with the design.
  • Schedule – a firm completion date was required of GSI in order for the property Owner to gain approval by the NYSDEC as of the end of the year.