Significant Project Features:

• In-situ solidification (ISS) of approximately 13,900 CY Hex-Chromium impacted soil via
  bucket mixing.
• Permeable Reactive Barrier approximately 300 LF and over 9,600 VSF backfilled with
  sand/ZVI for groundwater treatment.

Description of Work

• Excavation and backfill of approximately 300 linear feet of a permeable reactive barrier.
• Use of guar slurry during excavation to maintain trench side walls and stability
• Bucket mix work platform 8’ deep for groundwater cutoff and trench side wall stability.
• Backfill with sand/ZVI mixed via a volumetric mixer.
• Sand/ZVI backfill placed with a mini-excavator and skid steer utilizing a lead-in trench.
• In-Situ Solidification of approximately 13,900 CY’s of Hex-Chromium impacted soil via
  bucket mixing and an ALLU rotary head.

Key Project Objectives

• Completion of PRB trench along the adjacent Bliss Brook and wetland areas.
• Completion of ISS through unexpected subsurface conditions including boulders and large
  cobbles.

Project Challenges

• PRB trench alignment underneath active overhead power lines. The overhead lines were
  de-energized during the excavation and backfill, but restricted equipment size and
  operation ability.
• Small available footprint for spoil discharge and backfill placement due to adjacent Brook,
  wetland, and unavailable adjacent properties.
• Unexpected shut downs during trench excavation, causing slurry to breakdown.
• Nested cobble layers that created slurry loss during excavation.
• Difficult subsurface conditions during ISS including boulders and other obstructions causing
  refusal.