ADVANCING WATER ADVANCING WATERMARCH 2012 AUGUST 2010 QUICK FACTS Project Name: Blue Ridge Dam Rehabilitation Location: Blue Ridge, Georgia Owner: Tennessee Valley Authority Design Engineer: Rizzo & Associates Contract Amount: $24.3 million Start Date: April 2010 Completion Date: September 2012 FEATURE PROJECT: BLUE RIDGE DAM REHABILITATION by Chris Coston The Blue Ridge Dam is located on the Toccoa bulge forming at the bottom of the penstock including Tom Hufft, Pat Bennett, and Lance River near the Tennessee and North Carolina that extended 60 feet from end to end, and up Bunyan. Anthony Mravunac was on site early borders, just outside the small mountain town to two feet high in the middle. in the project helping with scheduling, of Blue Ridge, Georgia. Construction of the submittals, RFIs, and setting up the project. semi-hydraulic earth-filled dam began in 1925 Because of the bulge and other issues that Cedric Joor helped set up the safety program, by the Tennessee Electric Power Company have been noticed from routine inspections and then Brandon Blevins stepped in and (TEPCO), and was completed six years later through the years, as well as the need to meet took on the role of Garney Safety Manager. in 1931. The dam is 167 feet high, stretches modern dam safety standards and seismic Steve Culp was also on site for a few months 1,000 feet in length, and is approximately 950 requirements, TVA decided to repair the helping out with change order billings and feet wide at the base. Soon after the dam was penstock while stabilizing the intake tower and tracking all of the T&M work. Tyler Boehning built, the Tennessee Valley Authority (TVA) both sides of the dam in the process. After started with Garney as a laborer foreman on was established and they acquired the Blue several meetings with TVA to discuss this project. With a solid team in place, we Ridge Dam along with many other dams and planning, sequencing, budgeting, and were ready to take on this challenging project. reservoirs in the Tennessee River watershed. compiling a very strong proposal, Garney was Today, TVA is the largest public power awarded this project in early 2010 and company in the United States. mobilized on site in May of that year. The Blue Ridge Dam was originally equipped After the proposal and most of the planning with a 14-foot diameter steel penstock which was complete, masterminds Mike Heitmann carried water through the dam from the intake and Greg Harris passed the construction torch tower to the hydroelectric generator at the to the project team, led by Senior Project powerhouse. This penstock was damaged in Manager Mark Abram, Project Manager Chris the 1930s when a decision was made to drain Coston, and General Superintendents David the pipe without lowering the reservoir Cronister and Jerry Taylor. A handful of other elevation on the upstream side of the dam. Superintendents came in from all over the The extreme head pressure resulted in a country to help make this project successful FEATURE PROJECT: BLUE RIDGE DAM REHABILITATION Blue Ridge and tourists to the area who use the lake for recreation and relaxation were not thrilled with the drawdown. However, once the rehabilitation project is complete, TVA will no longer have to drawdown the lake for their routine inspections of the penstock like they have had to do every five years in the past. Once the soldier pile wall was in place and the lake drawdown level was reached, Garney began excavating down to the top of the existing penstock. The location of the These 30-foot joints were shipped via railcar First, we installed a large dewatering system breach was at the downstream end of the from the manufacturer in California to a rail on the downstream face of the dam which penstock near the powerhouse. Due to more yard in Atlanta, Georgia. Due to the limited included drilling eight deep wells, 29 eductor unsuitable soil conditions that were space on site, we had to keep most of the wells, two new piezometers to monitor the encountered here, we were able to obtain a pipe joints at the rail yard until we were ready water level, and seven new inclinometers to large change order to utilize two of Garney’s to install them. Each joint required its own monitor horizontal movement of the dam. largest trench boxes (34’L x 10’H) along with oversized tractor trailer along with escorts to Once the dewatering system was in place, we 28-foot spreaders that were installed around make the two-hour trip from Atlanta to the job began installing an anchored soldier pile wall the existing pipe to allow removal of site in north Georgia. When a 50,000-pound to reinforce the earthen dam prior to approximately 32 feet of the top half section joint was unloaded and lowered into the breaching the existing penstock. This is when of the existing liner. Breaching the penstock breach, it was placed on a custom built pipe we saw the first signs of unsuitable conditions was only the beginning. Before the new steel carrier that sat on top of a custom track. The in the form of a sinkhole after drilling out for liner could be installed, the steel bulge had to carrier was pushed upstream using a forklift one of the I-beams. This was the first of many be cut out and removed, and the water until the new pipe reached its destination, and large changes to the scope and, ultimately, coming out of the bulge and other places then a unique air bag system in the floor of the contract. throughout the penstock had to be minimized. the pipe carrier would be inflated to bell the pipe into position. Once in position, each pipe As this work was occurring, the drawdown of However, the biggest challenge the project was blocked up and tack welded. The carrier Lake Blue Ridge was also underway. Before team faced prior to installing the new liner would then return to the breach to receive the penstock could be emptied and breached, was to remove a 180-foot long concrete filled another piece of pipe, and the welding crew the lake pool elevation had to be lowered 65 steel girder. The girder, which was located in would begin sealing the new joint. Here feet. As one could imagine, the residents of the downstream end of the penstock, again, work only stopped twice a day every extended from the pipe invert to the crown 12 hours for shift changes. and averaged 16 inches thick. The ultimate solution was to cut the girder into individual There were 30 full joints that made up the 7-foot square sections weighing 11,000 lbs. new 900-foot penstock liner. After every four each, using an oxygen lance that burns at joints, or 120 linear feet, a bulkhead was built temperatures over 8,000º Fahrenheit. Then between the new liner and the existing one. each piece was carried by a rubber tire forklift The annulus space of each section was then approximately 300 feet to the breach area pumped full with grout to stabilize the new where each piece was lifted out using a pipe. Although the project was delayed over a 220-ton crane. The daunting task of removing this one million pound support took crews working around the clock, seven days a week for more than a month, which ended up costing more than $2 million to execute. Once the bulge and girder were removed, and the water intruding into the existing penstock was minimized, the installation of the new liner could begin. The new steel pipe was 12.5 feet in diameter and one inch thick. Page 2 FEATURE PROJECT: BLUE RIDGE DAM REHABILITATION month at the beginning due to unsuitable conditions and restrictions beyond our control, the first major milestone of beginning the refill of Lake Blue Ridge on April 1, 2011 was obtained. This was largely due to the Garney Team’s planning, managing, and willingness to basically live on site for six months until the penstock work was completed. In addition to relining the penstock, six post-tensioned anchors were required to be installed at the intake tower foundation. The anchors extended into the underlying rock, and after installation, were stressed to provide stabilizing forces to the tower. Reinforcement plates were also installed at the dividing wall between the intake tower gates. All this work was performed inside the intake tower, and like much of the penstock work, even during the deep drawdown was still almost 100 feet To date we have installed 99,000 tons of below the lake surface elevation. course aggregate and fine filter material to the downstream embankment as well as 76,000 The other major tasks of the project were on tons of rock fill. There are still 89,000 tons of and have had zero lost time incidents. This the exterior of the dam. The upstream face of rock fill that remain in order to complete the has been a wild ride since the beginning, and the dam was reinforced with approximately downstream face. We estimate that we will thanks to a large number of employee-owners 93,000 tons of course aggregate, fine filter have placed more than 375,000 tons of both on the ground and behind the scenes, material, and rip rap. This work was material once the project is complete, the Blue Ridge Dam Rehabilitation Project will performed during the drawdown in order to requiring approximately 21,000 truckloads. As end up being a very successful job for Garney use the dry access to the upstream face.