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TECHNICAL SUMMARY

Study Title Assessing the Impact of Oil Spills using Three-Dimensional Oil Spill Modeling 

(NSL PC-16-03)

Report Title Assessing the threat from oil spills in the Southern California Bight

Report Number(s) (OCS 

Study) BOEM 2024-042

Completion Date of Report August 2024

Number of Pages 46

Award Number(s) M16PG00008

Sponsoring OCS Region or 

Office Pacific

Applicable Planning Area(s) Southern California

Fiscal Year(s) of Study 

Funding FY 2016: $260,000; FY 2017: $68,000; FY 2018: $0; FY 2019: $150,000

Costs by Fiscal Year FY 2017: $264,550; FY 2018: $27,720.68; FY 2019: $35,700; 

FY 2020: $149,999.16; FY 2021: $0; FY 2022: $0; FY 2023: $0; FY 2024: $0

Cumulative Project Cost $477,969.84

Project Manager(s) Christopher Barker and Amy MacFadyen

Affiliation of Project 

Manager(s)

Emergency Response Division, Office of Response and Restoration, National 

Ocean Service, National Oceanic and Atmospheric Administration

Address of Project 

Manager(s) 7600 Sand Point Way NE, Seattle, WA 98115

Principal Investigator(s) Dylan Righi, Christopher H. Barker, Amy MacFadyen

Keywords Oil spill modeling, spill response planning, oil and gas platform, Pacific Outer 

Continental Shelf

ABSTRACT: The Southern California TAP (Trajectory Analysis Planner) provides a regional analysis of 

the most probable transport pathways from spills originating from any of the 23 Federal drilling platforms 

and four pipeline locations for use in spill planning and preparedness. To generate the statistical TAP 

database, the GNOME model was run 200 times for each designated source site within defined seasons 

using forcing from high resolution regional ocean and atmospheric models. A web-based interactive 

viewer (WebTAP) was developed to display the statistical results based on user selected inputs for source 

site, spill volume, season and level of concern. The viewer is publicly available and can be accessed at 

https://tap.orr.noaa.gov. 

BACKGROUND: The General NOAA Operational Modeling Environment (GNOME) is an oil fate and 

transport model developed and used operationally by NOAA for emergency spill response. Spill 

trajectory predictions rely on environmental information such as ocean currents and winds, which are 

highly variable, and can typically be predicted with reasonable accuracy for only a few days. For 

applications relevant to BOEM, like planning and preparedness work, the user doesn't know when or 

where a spill might occur. In this case, it is more informative to have a tool that incorporates historic 

weather and ocean currents to explore a wide range of possible outcomes in the case of a spill. In order to 
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address this need, NOAA’s Office of Response and Restoration (ORR) and the Bureau of Ocean Energy 

Management (BOEM) partnered through an Interagency Agreement to develop a Trajectory Analysis 

Planner (TAP) implementation for the Southern California Planning Area.

OBJECTIVES: Results from this study will aid BOEM to conduct oil spill risk analyses and determine 

potential impacts from hypothetical oil spills to environmental and/or cultural resources in the Southern 

California Planning Area. By using realistic weather and ocean current forcing to develop oil spill 

trajectory statistics for potential spills, this TAP project allows a user to estimate what areas could be 

impacted by a potential spill from one of the region’s platforms or pipelines. Questions that can be 

explored using the TAP results include: How much oil could be present at threatened locations? How long 

do responders have to respond? What sources are the most likely threats to sensitive locations and 

resources?

METHODS: A regional TAP implementation involves the development of a database of the results from 

a large number of simulated spill trajectories. These trajectories are computed with the GNOME model 

with realistic spill scenarios and historical environmental information. For this project, the trajectories 

were run using forcing from a high-resolution (1 km grid spacing) Regional Ocean Modeling System 

(ROMS, Shchepetkin and McWilliams 2005) hindcast. The meteorological model used in this study was 

the Weather Research and Forecasting model (WRF, Skamarock et.al. 2008), a next-generation mesoscale 

numerical weather prediction system designed for both atmospheric research and operational forecasting 

needs. Modeled spills were started at the locations of Federal offshore oil and gas operations in southern 

California, and at four locations representing pipelines servicing a subset of those platforms.

To generate the TAP database, the GNOME model was run 200 times for each designated source site 

within defined seasons. This is intended to capture the variability in winds and ocean currents—each 

model run or “scenario” uses a randomly selected start date from the 10-year ROMS and WRF model 

outputs available for currents and winds. Each scenario estimates oil weathering and movement over 21 

days from a 5 day continuous release of 200 barrels per day. A unique aspect of the Southern California 

Bight TAP project is that each simulated spill is carried out with the specific oil type found at each source 

platform or pipeline—this allows the trajectory results to be influenced by weathering of the oil in the 

environment. 

The spills used to generate the regional statistics were initialized in GNOME at the ocean surface. A well 

blowout model (the Texas A&M Oil spill Calculator (TAMOC) was also used to explore the evolution of 

the buoyant oil and gas plume arising from a potential shallow water well blowout including the potential 

for development of subsurface oil layers. Once oil droplets separate from the buoyant plume, particle 

tracking models like GNOME are well suited to predict further transport and fate.

The TAP viewer accesses the statistical database and visualizes the results allowing response planners to 

answer a myriad of questions about possible spill behavior in the region. As part of this project, NOAA’s 

Emergency Response Division has developed a web-based version of the TAP viewer (WebTAP) to 

enable this tool to be more flexible and easily available for oil spill response planners.

RESULTS: The results of the Southern California Bight TAP project are available for the 27 source sites 

in the WebTAP viewer at https://tap.orr.noaa.gov. The interactive TAP viewer allows response planners 

to tailor the output to examine the most relevant regional concerns. For each site, results include an 

“Impact Analysis” which is a statistical composition of the 200 individual model trajectories for a

particular season. A regional “threat map” shows the percentage of spills that result in a volume of oil 

greater than a user specified level of concern reaching gridded locations on the map. This “Impact 

Analysis” view gives a quick overview of the locations most likely to be impacted from a spill from a 

particular location.
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The “Oiling Analysis” result focuses on specific locations of concern, such as specific environmentally 

sensitive shoreline areas or marinas, to explore this question: How much oil from a release site could 

reach a particular location of concern? Another result that can be selected is the “Response Time 

Analysis” which shows the amount of time it would take oil originating from a particular source site to 

reach locations within the region.

Finally, “Threat Analysis” results considers all the source sites together to determine which ones are most 

likely to impact a particular location above a specified level of concern. This is most useful if there is a 

particularly sensitive location (e.g. a coastal marsh) and planners wish to know which potential spill 

location poses the greatest threat.

In addition to detailing the TAP methodology and results, the project report also contains an appendix 

detailing the results from the subsurface well blowout simulations. In the scenarios investigated, the bulk 

of the oil rose to the surface quickly (within hours).

CONCLUSIONS: The results of this study will be important for BOEM and other planners to better 

understand the risk from an oil spill in the Southern California Planning Area. The development of an 

interactive, web-based TAP viewer provides a flexible interface for utilizing the results to answer user 

specific questions. The viewer hosts results from not only this present study but also from previous and 

future TAP studies developed by ORR (including the U.S. Arctic, San Francisco Bay, San Diego Bay, 

Lake Sabine and Lake Calcasieu). Future work will continue to add new regional studies along with 

further enhancements to the viewer – for example, export of the results for GIS-based systems allowing 

overlaying of these results with other relevant geospatial datasets (e.g., Environmental Sensitivity 

Indices). 

STUDY PRODUCT(S): Deliverables produced by this study include: 

1. Statistical datasets on probable impacts from spills originating from 27 source sites in the Southern 

California Bight (23 Federal drilling platforms and 4 pipeline locations). 

2. Web-based publicly available viewer for querying and displaying results in the datasets.

3. BOEM study report detailing the methodology, providing information on how to use the viewer, and 

study results: 

Righi D, Barker CH, MacFadyen A. 2024. Assessing the threat from oil spills in the Southern 

California Bight. Camarillo (CA): U.S. Department of the Interior, Bureau of Ocean Energy 

Management. 46 p. Report No.: OCS Study BOEM 2024-042. Contract No.: M16PG00008. 

 
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MAP OF STUDY AREA: Figure 2 of report OCS BOEM 2024-042 

Figure 2. Map of twenty-three drilling platform locations in the northern Southern California Bight used 

as source sites for the TAP development.