The California Air Resources Board (CARB) has expanded its Commercial Harbor Craft rule, imposing stricter emissions standards for a wider range of vessels operating in state-regulated waters. Initially adopted in 2008 and amended over the years, the rule applies to new and existing diesel engines on ferries, tugboats, and other commercial workboats.
The latest amendments, effective Dec. 31, 2024, require affected vessels to run EPA Tier 3 or Tier 4 engines, with the inclusion of diesel particulate filters (DPFs) when they become commercially available. “After that date, a non-compliant vessel may no longer be operated in the regulated waters of California,” CARB stated in its final ruling.
DPFs are aftertreatment devices installed in exhaust systems to capture carbon soot particles emitted by diesel engines. These particles are then burned off in a process called regeneration, which requires high temperatures. Marine engines, such as those used in California’s tugboat fleet, operate at lower speeds, necessitating much higher burn-off temperatures — up to 1,500°F, nearly 250% hotter than those required for existing road vehicle DPFs.
No marine retrofit DPFs have been verified to meet CARB’s Level 3 emissions reduction standards, CARB told WorkBoat in March, noting that manufacturers Rypos, Franklin, Mass., and Nett Technologies, Mississagua, Ontario, are working to verify their DPFs while others have expressed interest in applying for verification.
Some Tier 4 engines include DPFs in their EPA-certified configuration. Once verified, CARB said it will issue an executive order listing compatible engines.
INDUSTRY CONCERNS
The rule has drawn pushback from the maritime industry, which cites concerns over technology availability, repower costs, and implementation timelines. Safety concerns are also at the forefront, as operators worry DPFs could impact vessel performance and fire potential could threaten mariners’ lives. Despite this, CARB maintains that these measures are necessary to reduce emissions from harbor craft in California waters.
Maritime advocacy groups, such as the American Waterways Operators (AWO), have voiced concerns over what they see as impractical and costly regulations that could compromise both safety and business viability.
According to AWO, one of the most pressing concerns remains the limited engagement from CARB leadership despite repeated attempts by industry representatives to establish a dialogue. AWO director of state advocacy Kyle Burleson expressed disappointment over CARB’s lack of responsiveness.
According to Burleson, the current regulatory process has not provided the same level of cooperation from CARB as the initial ruling did in 2008. Burleson noted that since joining AWO in 2022, he has seen minimal direct interaction with CARB leadership, citing zero interaction with the CARB board members responsible for creating the rule. AWO has offered CARB the opportunity to visit tugboats and observe firsthand how the rule impacts vessel operations, though these invitations have been ignored, Burleson said.
To address some of the rule’s challenges, the industry pursued legislative relief through Assembly Bill 1122 (AB 1122). The bill sought to allow bypass devices on DPFs, ensuring that vessels could maintain full power during critical maneuvers.
“The bill is pretty straightforward. It would allow for bypass devices on DPFs so an operator could choose when to put those devices into regeneration, because that process could take up to 90% of your horsepower,” Burleson explained. “That’s not something you want happening while escorting an oil tanker, as is required under federal law in San Francisco Bay.”
In September 2023, AWO president Jennifer Carpenter told WorkBoat, “We are really prioritizing the DPF issue because it is so important to safety. That is why we are focused on working with the [California] legislature to not abolish the DPF requirement but make sure that there are safeguards before it’s implemented.”
Despite AB 1122’s bipartisan support, Calif. Gov. Gavin Newsom vetoed the bill in October 2024, leaving operators with limited options. Safety concerns surrounding DPFs remain. “The last thing you want is to have a tugboat doing a job where it can’t have that full horsepower to stop a 1,000' cargo vessel,” Burleson said.
While fires involving DPFs have been reported on trucks and school buses, no casualties have resulted. In those cases, drivers and passengers were able to evacuate to safety on the side of the road. “Mariners don’t have that option,” Burleson said. “They’re either going to become firefighters, life raft occupants, or both, and that’s certainly what we want to avoid.”
Another hurdle is the absence of CARB-approved DPFs for towing vessel engines. “Of the 27 Tier 4 engines identified by CARB, only four have DPFs, and none are large enough to serve as a main engine on a towing vessel,” said Burleson.
Financially, compliance with the rule poses a significant burden on the industry. A pre-pandemic estimate placed compliance costs at $1.3 billion, a figure likely to be higher today due to inflation and supply chain challenges, Burleson said. Shipyard availability is another concern. “There’s not a ton of shipyards on the West Coast, and they book out over a year in advance,” Burleson said. “An operator has to book their shipyard time, order their equipment, and hope the stars align so all the work can be done in the time allotted. That’s a lot of uncertainty, and it’s really hard to run a business that way,” he said.
CARB maintains that shipyard capacity is sufficient, citing an analysis conducted during its rulemaking. “The capacity is sufficient to accommodate the volume of work resulting from the amended regulation,” a CARB representative told WorkBoat, citing Appendix E, page E-46 in the CHC ruling. “In the case where a DPF cannot be installed within the six-month window due to either shipyard scheduling issues or supply chain delays, the regulation provides an extension pathway,” the spokesperson said.
As a result of the rule, some operators are leaving California rather than attempting compliance. “From 2023 to 2024, we saw about a 15% reduction in vessels operating in California,” noted Burleson. “One of our members is talking about moving 20% of their fleet out of California.”
Industry stakeholders, including agriculture groups and vessel operators, remain engaged in efforts to amend the rule. “We’re not done with this rule by any stretch,” said Burleson. “We’ve had multiple meetings with groups who are just as concerned as we are.”
AN OPERATOR’S APPROACH
Despite industry resistance, some operators are taking a proactive approach. Curtin Maritime, a marine services company based in Long Beach, Calif., has invested heavily in repowering its fleet. Vice president of operations Chase Henderson emphasized the company’s long-term strategy. “These rules might be postponed, but they aren’t going away,” he said.
Owning a shipyard has given Curtin a compliance advantage. Within the past year, the company has repowered five tugs, replaced 12 generators, and repowered a crane — primarily without grant funding. “We have a whole team … and all they’re doing is repowering … and getting everything into compliance,” he said. “We’re covering most of these costs ourselves … paying primarily out of pocket for all of the engines,” Henderson said.
When asked about other operators, Henderson’s remarks echoed those of AWO, noting that some operators have closed shop, downsized their fleets, left the state, or sold their companies due to the inability to keep up with the regulation.
Henderson provided an example of the challenges in maintaining compliance. “We repowered a boat to Tier 3 four years ago. Last year, we ripped out the Tier 3 engines and put Tier 4 engines in,” he said. For California operators without their own shipyards, making such upgrades would be even more costly and difficult to arrange.
Given Curtin’s financial investment toward maintaining compliance, Henderson voiced concern over inconsistent enforcement. “We’re spending millions to update our fleet, yet we see operators coming in and out of California with non-compliant vessels that aren’t registered in CARB’s database, facing no enforcement or repercussions,” he explained. “That makes it difficult for us to compete. If CARB wants to impose these rules, enforcement needs to be uniform,” he said.
Despite the challenges, Curtin Maritime remains committed to compliance, viewing its cleaner fleet as a competitive advantage. In some cases, cleaner engines have helped the company secure contracts requiring the best available emissions technology.
“We’re repowering as fast as we can,” Henderson said.
