Skip Top Navigation

Safety, Security, Assessment & Operational Planning for LNG Fueled Ferries:

Safety and Navigational Risk Assessment for LNG-Fueled Passenger Ferry Vessels.

Liquefied Natural Gas


    November 2014

  • The U.S. Coast Guard has completed their initial review of WSF's safety, navigation and security risk assessment that evaluates WSF's proposed use of liquefied natural gas (LNG) as a fuel source for WSF. An updated executive summary of the project, the updated risk assessment reports and appendices are available on the left sidebar.
  • The U.S. Coast Guard is seeking public comments via the Federal Register on the assessments.


For over four years Washington State Ferries (WSF) has been conducting analysis, evaluation and detailed studies on an the viability of  using LNG as a source of fuel for our fleet. LNG is used world-wide in marine applications and provides an opportunity to reduce fuel costs, and better the environment by decreasing emissions.

What is LNG?
In its gaseous state, LNG is the same fuel used to heat our homes and cook our meals. LNG is natural gas that has been cooled to -256 degrees Fahrenheit, at which point it is condensed into a colorless, odorless, non-toxic and non-corrosive liquid. In its liquefied form it occupies 1/640th of its original volume, which makes it easier to transport and store.

Saving money, cleaner environment, energy independence 
WSF burns more than 17 million gallons of fuel each year. Fuel is our fastest growing operating expense, representing 23 percent of the FY13-15 operating budget, compared to 11 percent in FY00-01. Switching from diesel to LNG could save approximately 40-50 percent at today’s pricing.

Operating WSF's vessels with LNG would significantly reduce emissions when compared with today's use of ultra-low sulfur diesel fuel. WSF's Air Emissions Model predicts emission reductions as follows (please note that these reductions use the Issaquah Class ferries as a baseline):

  • 89 percent reduction in particulate matter 
  • 61 percent reduction in nitrous oxide 
  • 28 percent reduction in carbon dioxide
  • 59 percent reduction in sulfur dioxide 

Worldwide examples
Use of natural gas in transportation has been steadily increasing for the last decade. LNG is fast becoming a transportation fuel for transit buses, semi-trucks and ferries.

  • Since 2000 the Norwegian government has allowed the construction and operation of LNG passenger vessels. There are currently 20 car and passenger ferries operating in Norway that are fueled by LNG, view here.
  • Both BC Ferries and Staten Island Ferries are studying options to retrofit their vessels from diesel to LNG fuel.
  • The Quebec Ferries Company (STQ) has contracted for the construction of three new LNG ferries.
  • There are LNG passenger vessels currently under construction or in design for service in Argentina, Uruguay, Finland, and Sweden.

U.S. examples of LNG used in public transportation

Other LNG resources

WSF proposal milestones
Dec. 2011, WSF received conceptual approval from the U.S. Coast Guard to retrofit the propulsion system with new engines on the six Issaquah Class ferries  to use LNG as a source of fuel. 

Sept. 2012, WSF selected Det Norske Veritas (DNV) to complete a safety and security plan, risk assessment, and operational manual for converting to LNG. DNV is a classification body that has been involved in developing international standards for the use of LNG in passenger vessels.

Nov. 2013 WSF submitted a Waterways Suitability Assessment (WSA), which includes a safety and security assessment and risk management plan, to the U.S. Coast Guard for approval. The WSA concluded that the LNG proposal is inherently safe with risks as low as reasonably practicable.

Oct. 2014, the U.S. Coast Guard completed their initial review of WSF's safety, navigation and security risk assessment that evaluates WSF's proposed use of LNG as a fuel source for WSF vessels. The U.S. Coast Guard is holding a 60-day public comment period on the document.

Rendering of LNG tanks on Issaquah class ferry   rendering of LNG tanks on Issaquah class ferry
Renderings of LNG tanks on an Issaquah class ferry (click to enlarge)

Next steps
Below is the status of future key efforts:

  • The U.S. Coast Guard will review public comments, and make any necessary adjustments to the assessment prior to issuing a Letter of Recommendation.
  • Legislative approval Once the U.S. Coast Guard issues a Letter of Recommendation, WSF will then seek legislative approval and funding to move forward.    
  • Design/build LNG propulsion system – WSF will issue a request for proposal (RFP) for the use of LNG on selected ferries. The RFP will require the contractor to purchase and install all the required equipment and get all the required approvals to allow the vessel to obtain a certificate of inspection from the U.S. Coast Guard for operation with LNG as a fuel.
  • WSF could begin the first conversion to LNG as early as spring of 2016.


Joy Goldenberg
WSF Communications Manager