Notable for a number of ‘firsts’, the new LNG plant on the US west coast will bunker vessels and provide local utility customers with natural gas
A deep-water, major shipping hub in the US Pacific Northwest, the Port of Tacoma will soon be home to a new LNG facility capable of refuelling marine vessels. Jointly owned by Washington State utility Puget Sound Energy (PSE) and its commercial, sister company Puget LNG, Tacoma LNG has achieved several industry ‘firsts’ since its ground-breaking on 1 November 2016.
One of these ‘firsts’ is that when it opens in Q2 2021, Tacoma LNG will be the first LNG bunkering terminal on the west coast of North America. Moreover, it will serve a shared function, providing LNG for Puget LNG’s commercial customers, and the necessary natural gas reserves for PSE’s utility customers. This multi-use strategy will optimise resources by combining peak shaving and transportation markets to reach economies of scale and maximise utilisation. 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,” says Puget LNG business development manager Blake Littauer.
Another ‘first’ is the design of Tacoma LNG’s underground LNG pipeline by CB&I Storage Solutions, which will allow the refueling of TOTE Orca Class 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 9,300 l/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 3.35 m.
“Vessels that switch from diesel to LNG will reduce greenhouse gases [by] more than 30%”
The tunnel that houses the pipeline represents another engineering feat; it runs for 244 m 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 vapour 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,” says 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 the event we need to make a repair for some reason, we can pull the entire thing back up above ground.”
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 event of a leak.
Extensive design work and engineering was carried out on other project features to meet rigorous safety standards. US federal government regulations prescribe seismic requirements for the tank and facility that are more stringent than those for bridges and overpasses. “Our plant is designed to withstand a once-every-2,450-year earthquake with no loss of LNG,” says Mr Hogan. “As a comparison, US interstate bridges are engineered to a 1,000-year earthquake standard.”
Additionally, the entire facility sits atop approximately 2,000 concrete columns that are 91 cm in diameter and extend to a depth of 24 to 30 m. 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, 34,400 m3 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. Additionally, once construction is complete, up to seven rain gardens – ‘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.
Considerable thought was also put into handling the site’s pre-existing structures. While the property has a rich history – including operating as a shipyard and subsequent US 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, with a priority on minimising the impact of the demolition and ensuing construction. In all, more than 32,516 m2 of building space was demolished, generating roughly 18,131 tonnes of debris. However, 83% of those materials were recycled or repurposed. “We were also able to save a huge amount of concrete from the demolished buildings to use as fill for on-site grading later,” adds Mr Hogan.
That fill was put to good use when the team advanced to the facility’s largest and most distinguishing feature – a 30.3M litre LNG storage tank and 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 minimise any shaking motion from a seismic event – allowing 66 cm of movement in any direction.
Likewise, the facility’s non-pressurised, 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) which is fully encapsulated by 0.9 m of perlite insulation, and then again by another 61 to 91 cm 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 tonnes of steel forming the inner and outer tank and encased in 8,400 m3 of concrete, the tank is as much a visual marvel as a technical one.
As the construction phase of the Tacoma LNG project draws to a close, work is underway to commission the plant, which 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 the spotlight as the first LNG bunkering facility on the west coast – joining a growing number of global supply points 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, capable of providing our customers with a safe, reliable and economic LNG source that’s cleaner than the alternatives,” says Mr Littauer. “Vessels that switch from diesel to LNG will reduce greenhouse gases [by] more than 30% and dramatically reduce dangerous particulate emissions, advancing the shipping sector’s transition towards decarbonisation,” he concludes.