ECI – Engineers Construction

Engineers Construction recently completed the 3rd and final drive for the drainage tunnels on the Middlebury Railroad Tunnel Project.  The three drives were each 60-in-diameter cased bores in mixed-face and mostly rock conditions using a motorized small boring unit system provided by Robbins.  The drive lengths were 135, 152, and 137 feet each with a cut opening of 62.5 inches.  ECI used PermaLok steel casing for an outer liner and an American Augers 60-1200 for a jacking system and spoil removal.  The steerable and manned tunnel boring machine used a laser grade system to maintain line and grade.  Each drive was installed to within tolerances and within 1 inch of line and grade.

The rock consisted of limestone with a maximum unconfined compressive strength of around 19,000 psi.

The remaining work on this early work package contract is to finish contact grouting (outside casing grout fill), install the final carrier pipe inside of the casings, install the new precast concrete storm drain manholes, and backfill the launch and receiving shafts.  Once this drainage work is complete, the main railroad tunnel work will commence.

The launch shaft consisted of a 40-ft-diameter shaft excavated to a depth of 38 feet.  The launch and the receiving shafts were all located immediately adjacent to the tracks of the Vermont Railway.

ECI is a subcontractor to Kubricky Construction (Wilton, NY).  The Owner is the Vermont Agency of Transportation.  The project is located in Middlebury, Vermont.  More information on the Middlebury Tunnel is available on the VTrans project website: https://vtrans.vermont.gov/projects/middlebury/about.  And, the weekly blog by Mr.  Jim Gish (Middlebury Tunnel Public Liason):  https://www.middleburybridges.org/single-post/2018/11/15/2018-Update-57?utm_campaign=de0383ab-4151-4c4a-ab64-3c08df5fb02f&utm_source=so.

VTrans has also posted a youtube drone video: