Rock Island Dam is located on the Columbia River,approximately 15 miles south of Wenatchee,WA. The development of a crack in a spillway of Wanapum Dam,downstream of Rock Island Dam necessitated a 25 foot drawdown of the tailrace. This created a significant obstacle for the fish migrating upstream; they would not have access to the original fish ladder. With the arrival of the migrating salmon just a few months away,this project took on a critical path very quickly.
Chelan County PUD,owners of Rock Island Dam,contracted Knight Construction from Spokane to install the emergency fish ladder extensions in three areas,two on the west bank and one on the east. Knight,who handled the fabrication and topside support,turned to Global Diving & Salvage,Inc. to provide the diving support for the project. With the compressed schedule required to complete the project,Global and Knight worked closely on scheduling the arrival of the fabricated items and their installation.
The extensions,similar to the structural components of the original fish ladder structure,consisted of steel boxes and flumes used to create pools and steps. These new boxes and flumes were mounted to the face of the dam and in the case of the east side,were suspended from a pipe that spanned two pier noses. The project involved a wide array of construction techniques,including; core drilling,setting of epoxy and mechanical anchors to secure the boxes and frame work in place,wall sawing to remove sections of the dam to allow access at the lower water levels. The steel sections were bolted and in some cases welded in place.
By all accounts the project has been a great success. According to the Wenatchee World,over 20,000 of the expected record 235,000 Chinook salmon migration have already traveled upstream past Rock Island Dam.
Global Diving & Salvage,Inc was contracted by Salt River Project (SRP),operator of Horse Mesa Dam,located 65 miles northeast of Phoenix,AZ,to provide project management and diving services to make repairs of Units 1 through 4. The work on Unit 4,located in 160 feet of water,and on Units 1,2,and 3,located in 260 feet,necessitated the use of saturation divers.
Saturation diving is a method where divers live at a pressure equal to the depth they are working and transit to and from the work area via a diving bell. When not working,they live in chambers that are located on the deck of the barge. A crew of 21 working in two 12-hour shifts are required to support both the divers on deck and those in the water. In saturation diving,decompression is not eliminated; it is delayed until their rotation is over,which is usually 30 days. On this project,it took three days to decompress from the working depth to the surface.
In June 2012,a vertical concrete guide vane located in Unit 4 failed. Divers removed the remaining sections of the damaged vane as well as a second still-intact vane,using wire saws and wall saws. A new steel vane system,consisting of two vertical and nine horizontal vanes,was installed in place of the original concrete structures. The vanes were bolted in place and then filled with grout for added stability. New trashracks were installed in the intake. The bulkheads for Units 1,2,and 3 did not seal adequately to the penstock intakes due to deteriorated concrete on the intake opening face. Divers anchored and sealed new steel sealing frames at each intake location. Inspection also discovered deteriorated concrete at various locations in the three sets of gate guide slots on the upstream face,which was repaired.
We are providing full project management,supervision,and diving services required for the removal of existing stoplog guides,anchors,and grout from the Canyon Ferry Dam face. The removed stoplogs guides will be cleaned and taken to a storage area.
Global is providing diving services to assist with the demolition and removal of an abandoned offshore marine terminal. Existing structure is supported on concrete piling,scope of work involves the removal of an abandoned pipeline as well as assistance with cutting of concrete piling below mud line.
Cheesman Dam,located at 6,842 feet of elevation,is a primary reservoir for Denver Water who provides the potable water to Denver,CO and surrounding areas. Completed in 1905,it was built by Italian Master Masons using finely set and mortared granite blocks. Cheesman was a technological masterpiece and landmark of civil engineering for decades to come.
The Upstream Control Project,Phase 1,encompassed the replacement of three internal gate valves with new hydraulic slide gates located on the upstream face of the dam. The first step was to upgrade the existing Auxiliary,Mid and Low Level outlets,located at 60′,150′,and 200′ deep respectively.
Diver’s worked off of 80-foot by 80-foot sectional barge platform on the reservoir. Due to the depth and the amount of work required a combination of surface and saturation diving was utilized. The Auxiliary level work was done using surface supplied air while the mid and low level outlet work was done using saturation diving.
The original bypass outlets,tunneled through the canyon wall,were enlarged to accept new stainless steel spool pieces,one weighing 29,000 pounds and other two weighing 14,000 pounds each. Divers drilled holes at predetermined location and used underwater explosives to enlarge the openings to accept the new spool pieces. The spools were installed just inside the canyon wall,secured in place with epoxy anchors drilled into the native material,and securely grouted to provide a leak free seal. The new stainless steel slide gates were then mounted to the face of the spool pieces and protected by trash racks to prevent rubble from entering the intake system.
The new valves are operated from a new control structure built on the crest of the dam. This structure houses the hydraulic pump unit and controls which operate the valves. To connect the hydraulic tubing to the valves,holes were drilled from the crest of the dam,exiting into the reservoir next to the gate locations. Hydraulic tubing was installed into the holes and secured in place with grout,connecting the controls on the surface to the individual valves.
In 1929 the City of Portland built Bull Run Dam 1 on Federally protected and restricted land,the Bull Run Watershed. This complex,Bull Run Dam 1 and 2 is a significant source of potable water for the City of Portland and the surrounding area. Due to its location of Federally protected land and fact that we are working in potable water great care has been taken during the project,from complete decontamination of all diving gear and related equipment that enters the water,to complete containment for all mechanical equipment on site. Access to the site is extremely limited,there is no thru access across the top of the dam,all of the equipment had to be staged on top of the dam. The water level has fluctuated over 40 feet during the project,making access to the water extremely difficult.
The dam has seven slide gates mounted to the face of the dam inside a trashrack enclosure. These gates,located at various levels allow the operators the control the flow of water as well as the level (temperature) of the water as it moves through the system. During the project the existing trashracks as well as the supporting beams were found to be severely rusted. They are all being replaced with new galvanized beams and panels. One existing gate,#6 had severely eroded concrete behind the frame where it mounts to the dam wall allowing water to pass even when the gate was closed. Part of the project was the complete removal of the gate,drilling out of the original anchor bolts,repair to the concrete and reattachment of the gate to the dam. This entire process was carried out inside of the trashrack enclosure Tracks were mounted to the underside of the enclosure and the gate was moved to the outside edge where it lifted and set on deck for cleaning and storage while the concrete repairs were being made. The gate was reinstalled and secured with new anchors.
The existing materials were all the original installation,the nuts which secured the stem to the gate were severely corroded and had to be cut off. All of the existing stems were removed and disposed of as well as all of the stem guides and the actuators mounted on the surface. New stems guides were mounted to the face of the dam. New stems were attached to the guides. As stated above,all of the work was carried out inside of the trashrack structure,all of the parts and pieces had to be lowered into the water then cross hauled under the overhead structure and lowered into place. Once installed through the operator floor the stems were attached to new operators and connected to the gate itself. All gates were fully function tested for proper operation.
Part of the project also involved repairs to the spillway. Rolling scaffolding was raised and lowered on the curved spillway surface as needed to access the area to be repaired.
We have been contracted by the Washington Group to provide diving and dive related services as required in the building of Olmsted Dam on the Ohio River. After studying various dam construction methods,the Corps of Engineers (COE) decided to use an innovative method known as “In-the-Dry” for Olmsted Dam. Basically,sections of the dam known as shells are prefabricated on shore in a precast yard and carried out into the river and set in place. The dam consists of two primary areas; the tainter gate section and the navigable pass section.