Submitted by Puget Sound Energy
The Port of Tacoma is a deep-water, major shipping hub in the Pacific Northwest. Soon, it will also be home to a new LNG facility capable of providing marine vessels with a safe, reliable, and economic source of liquefied natural gas.
That facility, the Tacoma LNG plant, is a jointly-owned endeavor between Washington State utility Puget Sound Energy (PSE) and its commercial sister company Puget LNG. The project broke ground on Nov. 1, 2016 and, ever since, the plant and its team have continued to successfully reach the milestones that a project of this complexity entails. Along the way, they’ve also achieved a number of newsworthy, industry “firsts” – with more to come.
One of these firsts is what the Tacoma LNG plant will do. When it’s fully operational in the spring of 2021, the facility will be the first LNG bunkering terminal on the west coast of North America. Moreover, it will serve a shared function, providing liquefied natural gas for Puget LNG’s commercial customers, as well as the necessary natural gas reserves for PSE’s utility customers.
This multi-use strategy will optimize resources by combining peak shaving and transportation markets to reach economies of scale and maximize utilization. The Tacoma LNG plant was specifically designed for both functions and, when completed, will operate simultaneously without compromising supply.
“This is particularly important for our key customer, TOTE Maritime, and their need to have their two Alaska-bound ships bunkered weekly with LNG,” said Blake Littauer, Business Development Manager for Puget LNG.
On dry land, the project team has been equally committed to innovation, starting with the design of an underground LNG pipeline by CB&I Storage Solutions that will fuel those TOTE vessels and others like them. Instead of a traditional bunkering barge, the Tacoma LNG facility will fill ships directly from the tank via a dedicated bunkering arm, supplying up to 2,640 gallons per minute from a new pier in the port’s Blair Waterway. Underground LNG pipelines like these are a rarity, and none in the world directly compare to Tacoma LNG’s design with its vacuum-jacketed supply line, nitrogen-purged casing, and underground depth of 11 feet.
The tunnel that houses the pipeline represents another engineering feat. It runs for 800 feet along rights-of-way beneath TOTE’s facility – including crossing under a public street and two railroad tracks. Inside the tunnel, an innovative rolling rack system holds the supply pipeline in place, along with a vapor return, and recirculation, nitrogen and instrument lines. These sections of pipeline were fabricated and partially constructed off-site by Chart Industries, with final assembly done above ground at the Tacoma facility by EPC contractor CB&I Storage Solutions. Once the pipeline was fully formed and tested, the entire assembly was rolled into the tunnel.
“It’s an ingenious design,” said Tacoma LNG Project Manager Jim Hogan. “The pipeline is designed to last for the duration of the plant’s life with no active maintenance, but in event we need to make a repair for some reason, we can pull the entire thing back up above ground.”
Safety Measures
The system also exceeds current state and federal safety standards and underwent a rigorous three-year process to gain government approval. Additionally, the pipeline’s constant nitrogen purge, and methane and temperature sensors, can quickly detect any release of LNG in the unlikely event of a leak.
Extensive design work and engineering ensured that other project features met rigorous standards, too. Federal regulations prescribe seismic requirements for the tank and facility that are much more stringent than those for bridges and overpasses throughout the United States. “Our plant is designed to withstand a once-every-2,450-year earthquake with no loss of LNG,” said Hogan. “As a comparison, U.S. interstate bridges are engineered to a 1,000-year earthquake standard.”
Additionally, the entire facility sits atop approximately 2,000 concrete columns that are 36 inches in diameter and extend to a depth of 80 to 100 feet. These columns create an island of improved soil that will remain in place during an earthquake. They were formed in a unique process where an auger drill removes the soil while simultaneously injecting concrete. In all, 45,000 cubic yards of soil was replaced with the same amount of concrete. This aspect of the project received a Bronze Best in State Award in the Future Value to the Engineering Profession category from the American Council of Engineering Companies (ACEC) in 2018.
Of course, protecting the port’s unique environment remains an ongoing priority. On-site remediation efforts include steps to significantly restore habitat in the surrounding waterways for fish and other marine life. In addition to a new, 50-foot buffer of native plants along the bank of the Hylebos Waterway, 6,900 sq. ft. of wood decking has been removed from an existing pier to provide considerably more light for the aquatic habitat below. Additionally, once construction is complete, up to seven rain gardens (aka “enhanced treatment beds”) will be installed to filter the site’s storm water run-off before it discharges into the Hylebos Waterway. This will greatly improve storm water management on the site, which previously had uncontrolled run-off and numerous buildings coated in lead-based paint and asbestos siding.
Preserving Pre-Existing Structures
Considerable thought was also put into handling the site’s pre-existing structures. While the property boasted a rich history – including operating as a ship yard and subsequent U.S. Navy facility – only two original buildings could feasibly be preserved. One was repurposed as a control room and office facility; the other became a warehouse.
All other buildings needed to be removed, and the team made it a priority to minimize the impact of the demolition and ensuing construction. In all, more than 350,000 sq. ft. of building space was demolished, generating roughly 17,845 tons of debris. However, 83% of those materials were recycled or repurposed – a big source of pride for the entire team. In one of the older buildings, a large number of old-growth wood beams were carefully salvaged for reuse.
“We were also able to save a huge amount of concrete from the demolished buildings to use as fill for on-site grading later,” added Hogan.
That fill was put to good use when the team advanced to the facility’s largest and most distinguishing feature: an eight-million-gallon LNG storage tank, the only one if its kind in North America. Designed and constructed by CB&I Storage Solutions, the Tacoma LNG tank is unique for two reasons: its full-containment tank design and the seismic isolators that support it.
The tank’s 88 foundation isolators above ground are designed to minimize any shaking motion from a seismic event – allowing 26 inches of movement in any direction. Likewise, the facility’s non-pressurized, full-containment tank is as robust as they come. In the LNG industry there are single-containment tanks, double-containment tanks, and full-containment tanks. Tacoma LNG’s is a nickel steel inner tank (which holds the LNG) that’s fully encapsulated by three feet of perlite insulation, and then again by another by two to three feet of post-tensioned concrete outer tank and roof.
This full-containment construction is designed to withstand a total failure of the inner tank with no loss of LNG. With 1,300 tons of steel forming the inner and outer tank, and encased in 11,000 cubic yards of concrete, the tank is as much a visual marvel as a technical one.
Yet, even with so many engineering challenges met, and innovations already achieved, it bears reminding that the biggest first is still to come. As the construction phase of the Tacoma LNG project draws to a close, and the hard work required to commission the plant begins, this state-of-the art facility is poised to serve Puget LNG and PSE customers in early 2021. Doing so will propel the Port of Tacoma, and the Puget Sound, into an exciting new era – joining a growing number of supply points around the world fueling the next generation of low-carbon vessels.
“The Puget LNG facility is leading the way for the maritime industry with the first marine LNG bunkering pier on the West Coast,” Littauer said, “capable of providing our customers with a safe, reliable and economic LNG source that’s cleaner than the alternatives.”
