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.
We were hired to install blanking flanges on the upstream end of a high altitude dam in 150 ffw so our client could perform maintenance on the three valves in the outlet works piping of Relief Reservoir.
This remote reservoir is located in the Sierra Nevada Mountains at an elevation of 7,300 ft with no road access to the facility. All equipment and materials for this site is brought in by helicopter or mules. Due to the high elevation and depth of dive operations mixed gas diving was the primary form of diving employed to maximize working bottom time. Due to the greater decompression requirements of mixed gas techniques decompression chambers are utilized to ensure the diver’s safety.
A heavy lift helicopter (Sky Crane) was brought in to transport sectional barge pieces since the the crest of the dam was not wide enough for the dive equipment. Each piece was 15 ft by 7 1/2 ft and weighed over 8,500 pounds. Together they created a 30 ft by 45 ft dive barge. The heavy lift helicopter then lifted two decompression chambers and a dive van from the staging area in Kennedy Meadows to Relief Reservoir,a five minute flight.
Helicopter operations included a comprehensive security plan as the staging area is a high traffic tourist site for pack trains and hikers.
The Manette Bridge Replacement Project is a large WSDOT construction project to replace the aging 80yr. old Manette Bridge during a year-and-half-long project with contractors Manson and Mowat. Construction began in August of 2010 and is scheduled to conclude in early-2012. It will improve travel across the Port Washington Narrows by adding shoulders,widening the pedestrian walkway,and constructing a new roundabout in Manette.
Upon completion in the mid 1920’s,Dix Dam was the largest rock filled dam in the world standing approximately 287 feet above the riverbed. It was built in the private sector by it’s current owner,Kentucky Utilities Company,to create a reservoir for operating a hydroelectric generating station.
Global was selected to perform and manage repair work to an existing earth filled dam. Divers removed debris including cars,trees,and sediment from several areas of the dam and then these areas were surveyed using sonar and tactile methods. Damaged areas of the face slab were covered using sheet membrane secured to the face of the dam. Work took place in up to 140 feet of water.
Pier 2 of the Tanana Bridge near Tok Alaska,divers installed I-Beam whalers to reinforce the existing cofferdam structure from collapse during removal. The sheet pile walls were exposed down to 12 feet below mudline where they were cut off using underwater cutting equipment.
On Pier 3 divers cut the sheet pile at mudline,then drilled 56 1 1/2″ holes into concrete debris. Explosive charges were installed in each hole.
Conditions on the work site were made all the more difficult by temperatures that ranged from -20 to 38 degrees.
A four man dive team was provided to Ledcor Technologies Services,to assist in pulling a messenger line under the ice across the Kvichak River,in Igiugig AK. Holes were cut in the ice across the river and strobe lights were inserted into holes marking the cable path for the diver. Once cable pull was made the diver completed a video inspection of the laid cable.
The location of the project was in a very remote area of Alaska,equipment and personnel were brought onto the site via helicopter from a camp in Igiugig,30 miles away.
The Pride Wyoming,a Bethlehem JU-250-MS design mat rig,was jacked up on location at SS 283A when Hurricane Ike passed in September 2009. The rig was destroyed,leaving debris in three separate blocks. WWCI contracted Global Diving & Salvage,Inc. to assist in the prep,salvage and site clearance of all rig components including ancillary debris removal.
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 performed emergency repairs to a leaking hydraulic system. The repairs were completed at a depth of 175 feet at an elevation of 5,400 feet. With altitude corrections,diving depths were equivalent to 200 feet. To accomplish this task,we mobilized all aspects of a mixed-gas diving spread to French Meadows Reservoir in December,2006.
Together with PG&E personnel,we replaced the existing 14″ hydraulic cylinder and portions of the existing lines. After the replacement of the cylinder,the new cylinder and hydraulic required less than 1/3 of the original hydraulic pressure to operate the gate.
The project was conducted over a three-week time frame involving 25 dives without incident. We were responsible for providing cranes,barges,and environmental controls for the operation. The operational considerations included -30 below zero temperatures and extreme snow accumulations. A major concern of all parties was the potential release of hydraulic fluids into the lake.
All diving and operations were conducted safely and without incident in the extremely harsh deep-diving environment. Environmentally,the project was conducted without incident.