CHC Fact Sheet: Tugboats (Towing Vessels)
Commercial Harbor Craft Regulation
- Tugboats, also known as towing vessels, are commercial harbor craft equipped with relatively powerful engines and large propellers that work in combination with other harbor craft such as barges or ocean-going vessels.
- A single tugboat may operate in various regions across the State. A towing vessel is considered to operate in California if it is within Regulated California Waters (within 24 nautical miles of the coastline).
- As of 2021, there are ~229 towing vessels (with ~870 engines) statewide in three subcategories: escort/ship assist tugs, push/tow tugs, and articulated tug barges (ATB tugs).
- ATB tugs are specially designed pusher tugs that link to ATB barges transporting smaller quantities of petrochemical products over shorter distances at slower transit speeds compared to ocean-going vessel (OGV) tankers. However, separately, ATB tugs and barges are more similar to other regulated harbor craft in design. Therefore, for these amendments, both the ATB tug and barge are classified as harbor craft.
- Escort/Ship Assist tugs work primarily escorting or assisting OGVs in navigating narrow shipping channels, assisting in docking and undocking, and may work at secondary vocations such as performing barge moves.
- Push/tow tugs operate primarily at pushing or towing barges in vocations related to ocean towing of petrochemical tank barges or freight barges, or near-shore barge moves related to fuel bunkering, offshore supply work, or dredging/marine construction work in inland waterways.
- Under the Current Regulation, towing vessels, are required to use CARB diesel, report to CARB within 30 days of operating in RCW like all other harbor craft, and are required to upgrade to cleaner engines according to the requirements of the in-use rule.
Towing Vessel Population in the Year 2018
San Francisco Bay Area
South Central Coast
North Central Coast
San Joaquin Valley
- Towing vessels are one of the largest emitting categories of commercial harbor craft. In 2023 they will emit 19 percent of total commercial harbor craft PM2.5 emissions, and 23 percent of total commercial harbor craft oxides of nitrogen (NOx) emissions.
- Under the Proposed Amendments, DPM emissions from towing vessels would decrease by 94 percent, and NOx emissions would decrease by 65 percent by 2035.
- Under the Proposed Amendments, towing vessels operating in Regulated California Waters would be subject to the following in-use performance standards:
- use of Tier 4 engines equipped with diesel particulate filters (DPF).
- if engines are rated below 600 kilowatts (kW) and Tier 4 engines are not available in required power subcategories, Tier 3 engines equipped with DPFs.
Compliance Exceptions and Extensions
- Initial compliance dates, by which vessel owner/operators would need to upgrade engines or apply for extensions, are summarized below.
- With full compliance extensions, compliance dates for towing vessels would phase in between 2029 and 2034.
- Vessels operating under low-hour use thresholds within 24 nautical miles of the coast do not have to repower or retrofit their vessels.
- If compliance requires vessel replacement, towing vessel owners can receive up to six years of compliance extensions or 2034, whichever is earlier, if they can demonstrate financial difficulty
Limits – All Other Areas
Limits – DACs1
- Vessels with a berthing location or regularly scheduled stop two nautical miles from a disadvantaged community (DAC).
- The average cost to an individual for shipping a twenty-foot equivalent unit (TEU) of cargo is expected to have a slight cost increase due to compliance costs for escort and ship assist towing vessels and the expected increased rates passed onto container shipping companies for tugboat services.
Average Cost Increase
Average Cost Increase Per TEU Shipped,1,2
- This analysis assumes costs are completely passed through to paying customers.
- The TEU Cost Metric increase includes the combined compliance cost increases for tugs and pilot vessels.