Bluestone Dam Rehabilitation
Location: Hinton, WV
Owner: US Army Corps of Engineers, Huntington District
General Contractor: Brayman Construction Corp.
Value: $75.92 Million
Date Complete: November 2011
Dam Safety Assurance Phase 2B
Brayman was contracted to provide specialty construction services in order to upgrade the stability of Bluestone Dam, located in Hinton, WV.
This project involved the installation of 162 high capacity rock anchors, ranging from 6 to 61 strands, to upgrade the stability of the existing dam. With rock anchors as deep as 275' and the close proximity of adjacent anchors, drill tolerances of 1:150 were required so that the rock anchors did not intersect embedded items in the dam or other anchors.
Brayman utilized directional drilling techniques to satisfy such tolerances. The project also included the design and construction of two temporary soil nail walls, excavation and placement of 13,000cy of embankment along with the extension of 3 penstocks.
Modification Phase 2 – Spillway Anchors
Through our proven success with the installation of the dam anchors in the beginning phase, our team negotiated directly with the USACE for the installation of an additional 54 anchors. This scope also included the design and construction of a 780lf steel platform on the spillway to support anchor operations. The platform was able to support two, 85-ton crawler cranes in addition to multiple drill rigs and other support equipment. These anchors were located in both the east abutment and spillway sections. Similar to the initial dam anchors, the anchor holes required a minimum tolerance of 1:150.
Gallery and Apron Relief Drains
Work was performed on relief drains located in the inspection gallery and in the apron of the spillway. Relief drains minimize uplift pressure on the dam.
Gallery work, included cleaning 275 existing drains by enlarging the drain diameters 1/4”. This was accomplished by reaming the entire length of the drains (+16,000lf). Installation of 40 new relief drains was accomplished by core drilling to depths up to 120’. Vibrating wire peizometers were also installed at eight of these locations. As the gallery only measures 6’ wide by 8’ tall at peak, the tight space offered a challenge for the drilling team.
Apron work was performed from barges located in the stilling basin downstream of the dam. Existing relief drains tied to a drainage network were extended up to 25’ at 49 locations. Divers located the existing drain holes and verified the installation angle. As the sluice gates for the dam remained active, the schedule for the stilling basin was created keeping the barges away from all open gates.