Regulatory Assessment – Use of tugs to Protect against Oil Spills in Puget Sound

ITOS – Most cost effective alternative, but also lowest oil spillage averted.


Based on a White House Action Plan issued to the Department of Transportation (DOT), an assessment of the marine safety system in Puget Sound-area waters was conducted to determine whether any additional casualty prevention measures were warranted. In November 1998, Secretary Slater determined that the many existing elements of the region’s marine transportation system comprise a safe system. He went on to indicate that improvements can always be made and among other things that the DOT would fund and manage an analysis of the costs and additional risk reduction benefits that would be afforded by tug escorts or by stationing a rescue tug in the region. The Regulatory Assessment addressed these measures.

Why do the Assessment?

In November 1998, the Coast Guard issued an advanced notice of proposed rulemaking on potential rules that would improve marine safety in Puget Sound-area waters. Prior to any federal rulemaking a cost to benefit analysis must be performed; this assessment fills that role.

Eight alternatives evaluated:

  1. International Tug of Opportunity System (ITOS)
  2. Extend two tug escort requirement for laden single-hull tankers westward to "J" buoy
  3. Provide single tug escort for laden single-hull tankers westward to "J" buoy
  4. Provide single tug escorts east of "J" buoy for all Priority 1 vessels
  5. Provide single tug escorts east of "J" buoy for all vessels greater than 300 gross tons
  6. Provide single tug escorts east of "J" buoy for all vessels greater than 3,000 gross tons
  7. Dedicated rescue tug, to meet response times for all vessels throughout the region
  8. Dedicated rescue tug, to meet response times for tank vessels throughout the region

Assessment Approach

  • Include the Strait of Juan de Fuca and offshore approaches, Puget Sound south to Olympia, and the waters in and around the San Juan Islands.

Assessment Approach (cont.)

  • Make use of national historical oil spill data to project spill rates.
  • Calculate probabilistic oil outflow to project spill rates for double hull vessels.
  • Compare relative effectiveness in averting collisions, powered, and drift groundings.
  • Assess net cost effectiveness (implementation cost / oil spillage averted) of each alternative.
  • Consider clean up costs and environmental damage separately.


  • In year 2000 petroleum carriers pose the greatest risk with 75% of the total projected oil spillage, but by 2025 dry cargo vessels account for 66% of the projected outflow.
  • Number of spills will increase, but overall quantity decreases by 27% primarily because of the phase in of double-hulled tankers.
  • ITOS
  • Most cost effective, least spillage averted
  • Escort Tugs
  • Single tug escort (No.3) is next most cost-effective option.
  • Although alternatives 5 & 6 avert the most potential pollution, they are least cost effective.
  • Rescue tugs
  • Low probability of drift groundings limits effectiveness.

Other Sources

The complete Regulatory Assessment can be found on Internet at

The Thirteenth Coast Guard District Public Affairs Office (dep) created this page on December 27, 1998 and last modified it June 26, 2002. This page may be reproduced locally. If any changes are needed please notify D13 (dep) at 206.220.7237. More Coast Guard information can be accessed at and a complete listing of these fact sheets can be found at