Originally published at www.pacmar.com
A particularly challenging part of the Seattle SR 520 Floating Bridge Replacement Project involved 275 mixed-gas dives – each to approximately 205 feet of water, with AUS Divers required to perform 45 minutes of in-water decompression, followed by an hour and a half breathing 100-percent oxygen in the topside decompression chamber. Photo courtesy of Associated Underwater Services.
Marine construction projects are continuing along the West Coast, including several large infrastructure projects in Washington and California.
Associated Underwater Services (AUS) has been involved in the Seattle SR 520 Floating Bridge Replacement Project since 2012. At the peak times of the project, 12 employees would work in shifts performing several tasks including crack inspections, keel slab repairs, anchor cable replacements, joining pontoons, cathodic protection, installation of the deviation frames, ROV inspections of the cables, and casing burn offs. Safety has been a priority at all times, with pre-dive safety meetings being held before each shift that covered the dive plan, current conditions, emergency procedures, a crew list, depths, and equipment to be used.
The cable replacement was a particularly challenging part of the work, with about 275 mixed-gas dives having taken place over the project duration – each to approximately 205 feet of water. Divers were required to do 45 minutes of in-water decompression, followed by an hour and a half breathing 100-percent oxygen in the topside decompression chamber. “We also had use of our Seaeye Falcon ROV for doing a series of cable inspections,” says Kirk Neumann, AUS’ General Manager. “The project has gone very well. As the project design evolved, we added crews as needed.” AUS’ part of the project is nearly completed with diving operations to end this spring.
AUS has been working on several Seattle waterfront projects that include the Colman Dock, Pier 57 (where the iconic new Ferris Wheel is located), and the Aquarium Dock. Work includes pile repairs that involve excavating, cutting piles, installing replacement piles, installing forms, and pumping concrete. Equipment usually includes a barge-mounted crane to support the pile repairs. New pile driving is performed with a vibro or impact hammers. According to Neumann, work is not allowed to be done during mid-March to mid-July so as not to disturb herring spawning.
AUS is also helping to stabilize the shoreline for a tunneling project as part of the Alaska Way Viaduct replacement on the Seattle seawall. The team have been sealing cracks and installing an outfall under the fire station in shallow water (40 feet or less) conditions.
Another AUS project involves replacing the Navigational Lock Guide Wall timbers and cables and performing debris removal at Lower Monumental Dam. The US Army Corps of Engineers (USACE) owns and operates this dam and lock on the Snake River. This waterway is navigable from the mouth of the Columbia River to Lewiston, Idaho. Debris removal has involved clearing over 1,700 cubic yards of items such as logs, stumps, tires, and sediment that was blocking the water flow toward the dam generators.
“Using a ROV and sonar, we were able to evaluate pre- and post-debris removal areas to confirm to the USACE, that the proper amount of material had been removed,” explains Neumann. Equipment for the job was a 140-ton crane provided by Duncan Crane with a clamshell bucket that loads debris into trucks for transferring off site. “Scheduling this kind of project is challenging,” says Neumann. “In the spring, we have juvenile salmon running downstream with the run off, and in the fall, the adult salmon are heading upstream to spawn.”
Pacific Pile & Marine (PPM), based in Seattle, has been working on a variety of projects such as the SR 520 Bridge Replacement, and Elliott Bay Seawall Replacement, as well as projects involving remediation techniques and upgrades to marine infrastructure.
The company just finished the Lower Duwamish Waterway Enhanced Natural Recovery/Activated Carbon Pilot Study project for King County, on behalf of the Lower Duwamish Waterway Group (LDWG), which includes the US Environmental Protection Agency (USEPA), Port of Seattle, City of Seattle, and the Boeing Company.
The project was designed to compare the effectiveness of an environmental cap of granularly activated carbon (GAC) material with that of a more conventional capping material of crushed gravel and sand mixture. The goal of the study is to determine whether adding activated carbon to the sand layer can reduce PCB bioavailability (the amount of PCBs that can be taken up by fish and other living things in the river) in sediment as part of Enhanced Natural Recovery (ENR) which is the process of covering contaminated sediments with a thin layer of sand to speed up the process of natural recovery.
Although GAC has been used in several remediation projects, this project had very prescribed procedures of the storage and placement of the GAC that have not been previously utilized or studied. The project required the blended material (ENR+AC) be loaded onto a water-tight barge and be pre-soaked by flooding the barge with water from the Duwamish River for a minimum of 12 hours prior to placement. The blended material was then required to be kept saturated at all times before placement. The intent of the pre-soaking was to wet the AC particles and reduce the amount of air in the AC pore spaces, thus reducing the difference in density between the AC and the ENR material.
“The purpose of these types of projects is Enhanced Natural Recovery,” says Kustaa Mansfield, involved with Business Development at PPM. “It essentially gives Mother Nature a bit of a boost in restoring contaminated sites to a more natural state.” This particular project called for a target cover layer of nine inches with a minimum of 4 inches and maximum placement of one foot. In order to achieve the target lift, material was placed with a Hitachi 1200 long-reach excavator equipped with RTK-GPS and a 5-CY Young environmental bucket. The placement bucket was modified with internal plates to restrict the volume. Material was placed in two 4.5-inch lifts with an offset bucket pattern to achieve the target cover.
“One of the reasons we were selected for this project was because we have one of the most suitable environmental pedigrees in the region for performing these types of cleanup,” Mansfield continues. “PPM is one of only a few contractors in the Pacific Northwest to have performed CERCLA site remediation in recent years, having also been involved in a number of MTCA cleanups, with a modernized fleet of equipment. To our knowledge, the environmental agencies and key stakeholders were very pleased with the way the project went. Now they’re going to monitor the sites for the next few years to determine the effectiveness between the techniques.”
Another capping project recently completed by PPM was for Wyckoff Eagle Harbor site, near Bainbridge. The work involved using reclaimed dredging material from a previous project in Everett for beneficial reuse as a measure of economic and environmental sustainability. The project was not without its logistical challenges, notes Mansfield, due to the site being located adjacent to the Washington State Ferry route, which required sequenced operations and careful coordination with key stakeholders.
An area for which PPM is maybe less known is in the hydro/renewable sector. In past years, PPM completed a design-build run-of-river project for two new greenfield hydro facilities with a combined capacity of twenty 20 MW. For this project, 1,000 meters of above-ground 48-inch welded steel pipe penstock and 950 meters of buried 72-inch welded steel pipe were installed along with a dam and stream diversion, and more than 5,000 cubic meters of cast-in-place concrete. The penstock spanned more than 500 meters of elevation change calling for a cable crane system; the first of its kind installed in North America.
Another project recently completed was the Swan Lake Reservoir Expansion in Ketchikan, Alaska. The project consisted of the installation of a fixed wheel gate and flashboard system to raise the reservoir elevation 15 feet to allow for 25 percent more storage capacity, offsetting up to 12,000 MWh of diesel generation annually; equivalent to 800,000 gallons of diesel fuel. The fixed wheel gate and flashboards were manufactured in Austria and all the components and installation were close tolerance metric. The project consisted of 175 cubic yards of cast-in-place concrete. Both projects were in remote locations, only accessible by boat or plane, and required strong logistical expertise. Equipment and materials were barged to the site from PPM’s Seattle facility.
Currently, PPM is working at the Box Canyon Dam in Ione, Washington. PPM installed a sheet pile cofferdam and performed dredging in support of the construction. The project teams faced historical high and low waters levels as well as extremely inclement weather, more common with their projects in areas of Alaska. “At present, our cofferdam is submerged underwater, so our work won’t be visible until we return in 2018 when the water levels drop and we extract the structure,” explains Mansfield.
A current project is the Seattle Multimodal Terminal at Colman Dock scheduled to commence later this year. PPM is part of a joint-venture team to replace the pivotal hub for the Washington State Ferries (WSF), a division of the Washington Department of Transportation (WSDOT). The modernization will address operational efficiencies needed for continued growth as well as the safety of the aging structure that do not meet current seismic standards. The project will be sequenced and performed in phases to maintain operational use during construction, which is expected to be complete in 2023.
Alameda, California-based Power Engineering Construction Co (PEC), a heavy-civil and marine construction company, is underway with the design and construction of two waterfront projects for the San Francisco Bay Area Water Emergency Transportation Authority (WETA).
The first project, WETA’s Central Bay Operations & Maintenance Facility will support operations of WETA’s Central Bay Area fleet of ferry vessels and will function as an emergency operations center in the event of a regional disaster. The new facility will include a 70-foot tall, four-story building and working yard in addition to a vast over-water marine facility with berthing slips and utility hook-ups for twelve 400-passenger ferries. Boats will be serviced, cleaned, fueled and stored overnight at the facility.
The over-water portion of the facility consists of 14,000 square feet of concrete floats with 10-foot high steel walkway structures anchored to the top. Each steel walkway stands 18 feet above the keel of the float. Once floating and stable in the water, the height of each steel walkway structure is still 12 feet above water. The main float walkway extends more than 450 feet offshore with 6 finger floats each extending 136 feet perpendicular to the main. There are 10 different utility lines running from land out to each of the 12 vessel mooring locations; vessel support utilities include sewer, bilge water, potable water, compressed air, fire suppression, shore power, communications, fuel oil, lube oil, and waste oil. Awarded in May 2016 to Overaa-Power a Joint Venture, this $49M Design-Build 50-year essential facility project is scheduled for completion in March 2018.
At the peak times of the Seattle SR 520 Floating Bridge Replacement Project, 12 employees of Spokane, Washington-based Associated Underwater Services have been working in shifts performing several tasks including crack inspections, keel slab repairs, anchor cable replacements, joining pontoons, cathodic protection, installation of the deviation frames, ROV inspections of the cables, and casing burn offs. Photo courtesy of Associated Underwater Services.
The second project, the WETA Downtown San Francisco Ferry Terminal Expansion Project, is an enlargement of the existing Gate E ferry terminal into three new gates with vessel berthing facilities for up to six boats. The new terminal structure is designed to critical facility standards and provides a spacious layout that is intended to improve service and waiting facilities for ferry riders. There will be weather-protection canopies, large waterside pedestrian promenade areas and a spacious new granite plaza with amphitheater seating. This terminal will also serve as an emergency service facility in the event of a regional disaster.
Waterside project mobilization will allow for continued pedestrian access to the waterfront and current ferry service to remain operational during the entire course of the project. All construction work will be completed from the water using derrick and flat-deck barges. PEC’s fleet of floating equipment includes material barges, derrick barges, and sectional flexi-float barges.
D.B. Alameda, PEC’s 100-ton derrick barge along with its new 250-ton derrick (currently being constructed at a Louisiana shipyard) will drive more than 180 steel pipe piles to support 35,000 square feet of new over-water concrete wharf deck, a new pedestrian bridge, 3 gangways, and 3 floats. Some of the steel piles are as long as 157 feet in order to reach the dense sand lens that underlies the soft bay muds predominant along San Francisco Bay.
The anticipated total construction cost of this Construction Manager at Risk (CMAR) project is $73M. Power Engineering Construction Co. was awarded Phase 1 and will start demolition, dredging and pile driving work in June 2017. The overall project is scheduled for completion in the Fall of 2019.