US contractor Kenny Construction has begun mobilisation of the Borman Park Tunnel scheme in Gary, Indiana.
The contract, awarded by client American Water Works Service at a price of $37.2M in January this year, involves construction of a new 5.2km long Lake Michigan intake tunnel and pump station. A pre-construction meeting at the end of January resulted in a mobilisation date being set for early February.
The overall scope of project construction includes a 58.5m deep, 2.6m diameter intake shaft 1.6km out into Lake Michigan with a submerged intake crib; a 5.2km long rock tunnel lined to an id of 3m, a 72.6m deep vertical pump shaft that will include a 9.8m id, 41m deep concrete caisson to rock, and a 31.5m deep, 7.9m id vertical concrete lined shaft in rock.
The tunnel will be driven using a Robbins 3.8m diameter TBM with the machine slated to go to face in late July. Both the tunnel and shafts will be mined through Silurian and Devonian dolomite strata, except for the top portions of the shafts which will be excavated through overburden of fine sands and clays. Immediately above the bedrock surface there is a fairly uniform layer of glacial till. The tunnel overburden thickness varies between 32.8m and 46m. The dolomite is described as having good tunnelling properties with RQD’s ranging between 70 to 90% and UCS’s in the range of 6 600 to 24 000psi.
The scheme designed by US company Harza Engineering is scheduled for completion by 1 February 2003.
