FCWA Occoquan River Crossing Tunnel

As part of the Occoquan River Crossing Project, Drill Tech performed tunnel and shaft excavation with the purpose of increasing the existing main’s quality and sustainability while establishing higher water flow capacity for the city’s drinking supply. Drill Tech’s tunneling operations occurred underneath the river, where the blocky rock ground conditions presented difficulties for excavation. Moreover, the existing facilities and structures of a nearby historic community required strict blasting regulation.

Drill Tech installed a concrete tunnel invert, completed pre-excavation grouting for tunnel improvements, and installed two 42″ steel water main pipes in the tunnel. Utilizing raise bore methods, Drill Tech excavated two additional 7ft diameter shafts to a depth of 90′ below grade.

Lorton, CA

Contract Value:

$5.9M

Delivery Method:

Bid Build

Property Owner:

Fairfax County Water Authority

General Contractor:

Garney Companies, Inc.

Project Overview

  • Drill/blast excavation  
    • 410 LF (12′ wide x 9′ tall) Horseshoe Tunnel
    • 26′ dia. 95′ Shaft
  • 26′ Overburden Shaft Support   
    • Steel Ribs
    • Lagging Boards
  • 24′ Rock Shaft Support  
    • Rock Bolts
    • Mesh
    • Shotcrete
  • Tunnel Support  
    • Rock Bolts
    • Mesh
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