The tunnel was 2,966 yard (2712m) long, wide at water level, and from water to soffit (depending on the water level). At the time of building it was the third longest canal tunnel in the World after Sapperton and Dudley. Thirty-three shafts were sunk during construction with the workings dewatered using a Woodhouse steam engine. Water was provided for the Cromford Canal from the Butterley Reservoir situated on the hill above the tunnel. The Butterley Reservoir is itself crossed by a stone railway embankment currently used by the locomotives of the Midland Railway - Butterley's preserved steam railway. Water flowed from the reservoir directly into the tunnel via an adit along the tunnel from the Western Portal. Above the Eastern portal the Butterley Park Reservoir once provided water to the canal. This Reservoir was filled in during 1935. Both the tunnel and reservoirs were constructed by the Butterley Company, formed in 1790 by Benjamin Outram (1764–1805) and Francis Beresford (died 1801) with William Jessop (1745–1814) and John Wright (1758–1840) joining by 1793.