Dover Dam DSA - Phases 1 & 2
Location: Dover, OH
Owner: US Army Corps of Engineers - Huntington District
General Contractor: Brayman Construction Corp.
Phase 1 Date Complete: August 2013
Phase 2 Date Complete: January 2015
Brayman was contracted by the U.S. Army Corps of Engineers, Huntington District to provide specialty construction services in support of the Dam Safety Assurance (DSA) projects located in Dover, OH.
DSA, Phase I involved the installation of 36-each, multi-strand anchors in the spillway section of the dam. The anchors range size from 19-strand to 48-strand and were installed in holes sized from 9-inch to 17-inch diameter. The anchor lengths vary from 103-foot to 153-foot. Directionally drilled pilot holes were used to meet tolerances of 1:150.
Scope for DSA, Phase II required the installation of 21-each multi-strand anchors ranging from 9-strand to 54-strand in holes ranging from 9-inch to 19-inch diameter. Lengths varied from 50-foot to 180-foot. The anchors were directionally drilled on the face of the dam to meet a tolerance of 1:150.
In addition the anchors on the face of the dam, 83-each, 5-strand and 13-strand anchors were installed in the downstream apron 13-feet to 20-feet below water. These anchors were originally designed as 2.5-inch diameter Grade 150 bar anchors, but were value engineered to 5-strand to 13-strand anchors. Dewatering was accomplished using a system of precast walls and stackable post-tensioned coffer boxes.
Previously in 2008, Brayman installed 3-inch Grade 150 post-tensioned bar anchors in the gallery of the dam as part of an emergency remediation contract. The new strand anchors installed during DSA Phase 1 and Phase 2 were meant to intersect the existing 3-inch grade 150 bar anchors. This required custom core bits up to 17-inches in diameter. Every anchor that was intended to intersect a previously installed bar anchor in fact did intersect the anchors at depths up to 80-feet. This proved the accuracy of Brayman’s directional drilling system.
Post-Tensioned Precast Walls
Precast and cast-in-place walls were built to increase the height of the dam by 13-feet thus adding storage capacity and mitigating the threat of downstream flooding. Precast panels were detailed to match the existing structure and anchored to the dam with over 500-each post-tensioned undercut anchors. In most locations, the cast-in-place wall is supported on caisson foundations.
Additional Work Items
- Design, fabrication, and installation of a temporary steel access platform along the non-overflow section of the dam. Platform consisted of roughly 2-million pounds of structural steel and supported an 80-ton crawler crane in addition to multiple drill rigs.
- Installation of a 2,200-square foot soil nail wall adjacent to the platform.
- Construction of a two mile access road.
- Significant amount of site restoration.
- All concrete finishes on the dam, including the post-tensioned recess backfill, was color matched and sand blasted to match the existing finish.
2015 Post-Tensioning Institute (PTI) Award of Merit