Breakthrough on Blacklick

3 June 2019

US – The first microtunnel drive on the Blacklick Creek Trunk Sewer in Albany, Ohio, made a breakthrough, Aldea Services announced yesterday. It is serving as the construction management team and trenchless design engineers.

The 48-inch inside diameter RCP curved (vertical and horizontal) microtunnel will be 3.154ft (961m) long when completed by trenchless contractor Ward & Burke. The project consists of two curved microtunnel drives of 1,653ft (504m) and 1,501ft (458m), one launch shaft, and two receiving pits. The drives are located from 20ft to 38ft deep in predominantly Cuyahoga Shale with five to 10 per cent of the drive length in glacial soils. Ward & Burke is using a Herrenknecht AVN 1200 slurry MTBM on a grade of 30 per cent.

"Additional project constrains and key stakeholder concerns include protection of groundwater and private wells, a creek crossing, a county road crossing, tie-in to a downstream, newly-constructed sewer tunnel, and disruption to local traffic and residents," said Guadalupe Monge of Aldea.

Construction started on February 4 and the first drive began on March 21. The total drive length from pit wall to pit wall was 1,653ft and the average jacking force experienced was 148t, two interjacking stations were installed but were not used.

"Our average skin friction of 0.080 psi--including the vertical curve--demonstrates that when the jacking pipe has a joint capable of withstanding 55psi external pressure, adequate lubrication can then be distributed to the annulus at an adequate pressure to control the skin friction being applied to the pipe, allowing lower tonnage and greater tunnel distances to be achieved," said Colin Irwin of Ward & Burke.

The average advance rate was approximately 50ft per day, excluding Sundays and holidays, and working two 12-hour shifts per day.

Construction of the final 1,501ft-long drive began on May 14 and will incorporate compound curves with 820ft (250m) and 1,640ft (500m) radii, and a 400ft straight section. Ward & Burke is using Herrenknecht's anti-roll can technology to prevent rolling of the MTBM and increase production.

The extension will provide sanitary sewer service to the areas of Jefferson Township, Plain Township and the City of New Albany.

Lead design engineer for the project is is EMH&T and Forterra supplied the jacking pipe.