ecological risk assessment: consensus workshop - mc-20 ......era consensus workshop - mc-20a...

Ecological Risk Assessment: Consensus Workshop

An Examination of the Potential Ecological Impacts

of Response Alternatives Being Considered for Sheen Abatement for the Remnants

of the Taylor Energy Company, LLC

MC-20A Platform – Gulf of Mexico

ERA Consensus Workshop - MC-20A Platform - Gulf of Mexico






MC-20A Platform – Gulf of Mexico

A Report to Taylor Energy Company, LLC

James Staves, Leah Robinson, Don Aurand (Compilers)

HDR | Ecosystem Management


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CITATION

Suggested Citation:

Staves, J., L. Robinson, D. Aurand. 2013. Ecological Risk Assessment: Consensus Workshop. An

Examination of the Potential Ecological Impacts of Response Alternatives Being Considered for

Sheen Abatement for the Remnants of the Taylor Energy Company, LLC MC-20A Platform – Gulf

of Mexico. A report to Taylor Energy Company, LLC. HDR | Ecosystem Management, Lusby, MD.

20657. 50 pages.


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TABLE OF CONTENTS

Page

Executive Summary .........................................................................................................................1

1.0 Objectives of the MC-20A CERA Workshop .......................................................................5

1.1 Unified Command Objectives........................................................................................5

1.2 The Application of the Consensus Ecological Risk Assessment Process......................5

1.3 Participants .....................................................................................................................6

1.4 Organization of the Report and the Associated Compact Disc .....................................7

2.0 Overview of Workshop Events ...............................................................................................9

2.1 First Workshop...............................................................................................................9

2.2 Second Workshop ........................................................................................................11

3.0 Background Information .......................................................................................................13

3.1 The MC-20A Platform Accident – September 2004 ...................................................13

3.2 Initial Environmental Investigations ............................................................................16

3.3 Response Activities to Date .........................................................................................17

3.4 Recent Environmental Investigations ..........................................................................19

3.4.1 Creation of Well Review and Sheen Source Work Groups – February 2012 .19

3.4.2 Recommendations from the Well Review Work Group ..................................19

3.4.3 Recommendations from the Sheen Source Work Group .................................19

3.4.4 NOAA Acoustic Survey – July 2012 ...............................................................20

3.4.5 Soil Sampling and Chemical Forensic Analysis – July 2012 ..........................20

3.4.6 July 2012 Sampling Program Results ..............................................................20

3.4.7 February 2013 Sampling Program Results ......................................................21

4.0 Elements of the CERA Process.............................................................................................23

4.1 Geographic Area of Concern .......................................................................................23

4.2 Resources of Concern ..................................................................................................23

4.3 Conceptual Model Matrix ............................................................................................24

4.4 Risk Ranking Process ..................................................................................................25

4.5 Response Options Considered .....................................................................................27

4.5.1 Site Remediation Options ................................................................................27

4.5.2 Intervention and Containment Options ............................................................28

5.0 The Results of the CERA ......................................................................................................29

5.1 Results of the First Workshop......................................................................................29

5.2 Evaluation of the Current Situation .............................................................................29

5.3 Evaluation of Potential Response Options ..................................................................30

6.0 Recommendations and Lessons Learned ..............................................................................35

6.1 Participant Review and Discussion ..............................................................................35


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6.2 Focus Group Discussion Points ...................................................................................35

6.2.1 Focus Group 1 ..................................................................................................35

6.2.1.1 Conclusions .........................................................................................35

6.2.1.2 Recommendations ...............................................................................36

6.2.2 Focus Group 2 ..................................................................................................36

6.2.2.1 Conclusions .........................................................................................37


6.2.3 Focus Group 3 ..................................................................................................38

6.2.3.1 Conclusions .........................................................................................38


6.3 Consensus Recommendations of the Workshop ..........................................................40

6.3.1 Dredging Options .............................................................................................40

6.3.2 Well Intervention .............................................................................................40

6.3.3 Existing Ecological Risk ..................................................................................40

6.3.4 Expanded Response Capability........................................................................41

6.3.5 Contingency Preparedness Capability .............................................................41

6.3.6 Other Conclusions ............................................................................................41

6.3.7 Recommendations ............................................................................................41

7.0 References .............................................................................................................................43

Appendix A: Participants ..............................................................................................................45

Appendix B: MC-20A Reference Materials and Contents ...........................................................47


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LIST OF FIGURES

Figure Description Page

3.1 General Location Map of MC-20 .........................................................................................13

3.2 Site Location and Regional Seafloor Bathymetry Map .......................................................14

3.3 Original Position vs. Post-Failure Position Following Hurricane Ivan ...............................15

3.4 Profile View of Buried MC-20A Well Conductor ................................................................16

4.1 Ecological Risk Ranking Matrix ...........................................................................................26


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This Page Intentionally Left Blank


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LIST OF TABLES

Table Description Page

2.1 Focus Groups, Leaders and Recorders ....................................................................................9

4.1 MC-20 Resources at Risk ....................................................................................................24

4.2 TEC Ranking Sheet (Conceptual Model Matrix) used for the Baseline Analysis ................25

4.3 Modified Risk Ranking Scale ..............................................................................................27

5.1 Modified Risk Ranking Scale ..............................................................................................30

5.2 Detailed Risk Analysis Results - Group 1 ............................................................................31

5.3 Detailed Risk Analysis Results - Group 2 ...........................................................................32

5.4 Detailed Risk Analysis Results - Group 3 ............................................................................33


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ix

LIST OF ABBREVIATIONS AND ACRONYMS Bbl Barrels

BML Below Mud Line

BOEM Bureau of Ocean Energy Management

BSEE Bureau of Safety and Environmental Enforcement

BTEX Benzene, toluene, ethyl-benzene, and xylene

CERA Consensus Ecological Risk Assessment

CD Compact Disc

EPA Environmental Protection Agency

ERA Ecological Risk Assessment

FMMG Fugro-McClelland Marine Geosciences

FOSC Federal On-Scene Coordinator

Ft. Feet

G Gulf of Mexico (for Geographical Scaling)

Gal. Gallon

GOM Gulf of Mexico

HDR HDR | Ecosystem Management

IAP Incident Action Plan

In. Inch

IW Intervention Well

L Local (for Geographical Scaling)

LA DEQ Louisiana Department of Environmental Quality

LLC Limited Liability Company

MC Mississippi Canyon

MMS Minerals Management Service

PoS Probability of Success

R Regional (for Geographical Scaling)

ROV Remotely Operated Vehicle

NOAA National Oceanic and Atmospheric Administration

RRT VI Regional Response Team 6

TEC Taylor Energy Company, LLC

UC Unified Command

USCG United States Coast Guard

USFWS United States Fish and Wildlife Service


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1





MC-20A Platform - Gulf of Mexico

Executive Summary

Taylor Energy Company, LLC’s (TEC) MC-20A Platform was installed in 1984 at a

location about 10 miles southeast of the mouth of South Pass of the Mississippi River in Block

20, Mississippi Canyon Area (MC-20). At the time of the design and installation of the MC-20A

platform it met or exceeded all regulatory requirements for new platform installations in the Gulf

of Mexico (GOM).

In September 2004, Hurricane Ivan entered the GOM, passing about 60 miles east of

MC-20. Ivan alternated between a Category 4 and Category 5 storm as it traveled northward

towards the coast, with maximum wave heights near 100 feet (ft.) and peak wave periods near 18

seconds. These wave heights and wave periods were much larger and longer than those wave

conditions used in structural designs for the Eastern GOM.

The platform was toppled by a regional slope failure, or unprecedented large-scale

mudslide, during Ivan and now lies about 550 ft. down slope and southeast from its original

location. TEC conducted a series of studies and investigations in the years that followed to

determine the sources and magnitude of oil and gas leaks from various locations in the debris

field.

In the summer of 2008, the U.S. Coast Guard (USCG) established a Unified Command

(UC) composed of TEC, USCG, and the Minerals Management Service (MMS), since divided

into Bureau of Ocean Energy Management (BOEM) and Bureau of Safety and Environmental

Enforcement (BSEE), to direct response efforts for the ongoing releases. These included drilling

intervention wells and plugging nine of the wells with the highest release potentials, placement

of containment domes over three observed emission areas, and daily over-flights to monitor

sheen sizes.

As a result of the response efforts, daily observed sheen sizes have steadily diminished, to

the current average observed sheen volume of about 3 gallons (gal.) per day. Sheens from the

downed platform have never been observed to impact the shoreline, or affect fish and wildlife.

Based on the observation that the current response actions were reaching a point of

diminishing returns, the UC decided to convene a broadly-based group of stakeholders with

applicable expertise, and conduct a Consensus Ecological Risk Assessment (CERA) to evaluate

the potential ecological impacts of available response options. HDR Ecosystem | Management

(HDR) was contracted by TEC to facilitate the CERA.


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The CERA process is designed to help environmental managers compare ecological

consequences of specific response options. The process focuses on ecological “trade offs” or

cross-resource comparisons. Seven response options were considered, which fell into two

categories, “site remediation” or “intervention and containment”. Options in the site remediation

category were:

Excavation of contaminated sediments, with onshore disposal;

Capping contaminated sediments with non-contaminated MC-20 sediments; and

No excavation or capping, with natural sedimentation (the current situation, or baseline).

Options in the intervention and containment category were:

Intervention on all remaining wells – with and without potential adverse outcomes;

Intervention on remaining wells with flow potential – with and without adverse

outcomes;

Expanded response capability to reduce the current sheen by 75% using best available

technology; and

Expanded preparedness capability by developing a containment solution for the worst

case discharge (200 barrels [bbl] per day).

The CERA involved two 3-day workshops, led by a facilitator (HDR). A steering

committee composed of representatives from the USCG, TEC, BSEE, and the National Oceanic

and Atmospheric Administration (NOAA1) was established to tailor the CERA process to the

unique circumstances presented by the TEC scenario. The steering committee convened

approximately bi-weekly, and recommended the CERA participants. There were a total of 45

attendees, representing 21 different organizations, companies, or governmental agencies.

The workshops were held at the BSEE office location in New Orleans, LA, during May

13–15, and June 25–27, 2013. Workshop participants were divided into three focus groups. Each

appointed a leader and a recorder and evaluated the seven alternative courses of action. The

initial analysis of the current situation (the baseline) was performed with the aid of a 4x4

Ecological Risk Ranking Matrix, a Resources at Risk Table, and a Conceptual Model Matrix.

The ecological risk was determined by two factors – the recovery time for a resource and

percentage of the natural resource affected. All focus groups concluded that the current situation

presented relatively low levels of ecological risks, meaning that a change in conditions was

recognized, but did not noticeably alter any functions within an ecosystem.

However, when they began the analysis of the remaining options, the participants

concluded that the ranking matrix lacked sufficient sensitivity to discriminate between

anticipated ecological consequences associated with the various alternative courses of action

because all ecological impacts appeared to fall into the lowest category. In general, use of the

forms and scales that were initially proposed for use resulted in all options being rated in the

very low end of the “percentage of resource affected” scale. The participants also had difficulty

utilizing the “recovery time” criterion, since it implies that an exposure to a stressor has ended,

and the oil sheen resulting from the downed TEC platform is ongoing, albeit very limited. For

1 Although NOAA was a member of the Steering Committee to help form this approach and process, its

representative was acting in the role of scientific support to the USCG.


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these reasons, the proposed ranking matrix was not used for the remaining six options, and was

replaced with a simple, one dimensional scale of 1 to 9, where larger numbers indicated higher

levels of concern. For the two lowest and highest categories (i.e., 1, 2 and 8, 9), focus groups

were required to record the rationale for selection.

The baseline condition (natural sedimentation) was assigned a value of 5 (using the

modified scale), so that alternatives could be ranked as either 1 to 4 levels of concern above or

below current conditions. When using this approach, focus groups still considered geographic

and population impacts, but did not use the original ranking system and were also free to discuss

other factors, more specific to each resource of concern. After the assessments of all response

options were completed, each focus group developed their own list of conclusions and

recommendations, which were then merged into a single set of consensus recommendations

through a facilitated plenary session. The participants concluded that current sedimentation processes provide a natural

mechanism for attenuation. However, sedimentation would only mitigate/attenuate sheens

generated by contaminated sediments on-site. The perception of the ecological risk associated

with the current situation at MC-20 was that there is low risk to resources in the general vicinity

of the lease block and no exposure risk to resources outside the local area. Dredging options

were determined to be impractical and to likely have unacceptable or unintended adverse

consequences that could outweigh potential environmental benefits. Well intervention was not

recommended because drilling intervention wells was not expected to provide sufficient

ecological benefit to offset the risks and impacts associated with drilling and plugging

operations, even though multiple well conduits may remain open for potential flow. Any action

taken to expand existing response capability was thought to be ecologically beneficial, but not

measurable. Efforts to improve preparedness capability were expected to be beneficial for MC-

20 in the event of a worst case discharge (up to 200 bbl/day), but additional research and

development would be required. Based on those conclusions, the workshop participants

developed a list of consensus recommendations, acceptable to all participants. The

recommendations are as follows:

Expanded response capability could be a sound option;

Utilization of the site for research and training purposes should be considered; and

Develop contingency preparedness capability to respond to a potential worst-case

discharge scenario.

For the USCG, the group recommends that:

Additional factors (e.g., wind speed, direction, sea state, % of dark/recoverable oil) be

considered in a decision matrix to determine the threshold for response operations;

Analyze historical sheen data to evaluate the frequency and procedures of over-flight

operations. Flights could be triggered by specific operations which disturb bottom

sediments, remote sensing data or other reporting sources. Conduct additional over-

flights when surface expression is calculated above 40 gal.;

Do not pursue additional well intervention because the ecological risks outweigh the

possible benefits; and

Do not pursue dredge/dispose or dredge/cap options because the ecological risks

outweigh the possible benefits.


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1.0 Objectives of the MC-20A Consensus Ecological Risk Assessment Workshop

1.1 Unified Command Objectives

The USCG Sector New Orleans Federal On-Scene Coordinator (FOSC), working in

conjunction with the UC, has been monitoring the ongoing oil discharge since the platform and

25 connected wells were damaged during Hurricane Ivan. Since 2004, nine intervention wells

have been drilled, and a subsea containment system has been installed, but there continues to be

a visible, crude oil sheen on the surface of the water.

In April, 2013, the USCG FOSC convened the Region VI Response Team (RRT VI) to

seek consultation on methods available to assess the ecological risks associated with varying

potential courses of future action. As a result, the UC decided to conduct a formal Ecological

Risk Assessment (ERA) to evaluate the ecological trade-offs and environmental effects, both

beneficial and adverse, of potential response options on the environmental resources at risk. The

objective was to bring in a diverse group of stakeholders and trustees to evaluate possible

mitigation strategies and develop a technologically feasible and environmentally defensible path

forward. That approach was believed to offer the best hope of minimizing adverse environmental

consequences to the ecosystem as a whole, based largely on the expected time to recovery for the

major ecosystem components.

1.2 The Application of the Consensus Ecological Risk Assessment Process

The ecological risk assessment process that was recommended to the USCG by RRT VI

is known as a CERA. Other types of ecological risks assessments have been developed by

various agencies and organizations, but the CERA process has been particularly useful for

contrasting the potential ecological effects of varying courses of action that can be considered

during oil spill planning activities.

In 1998, the USCG began sponsoring efforts to develop a comparative risk methodology

to evaluate oil spill response options. Interest in selecting response options based on a

risk/benefit analysis predates the 1998 initiative, but the current effort is different in that it

emphasizes a consensus-building approach to evaluate risks and benefits.

The USCG sponsored the development of a guidebook on this process: Developing

Consensus Ecological Risk Assessments: Environmental Protection in Oil Spill Response

Planning. A Guidebook (Aurand et al., 2000). The process is designed to help planners compare

ecological consequences of specific response options, especially in nearshore or estuarine

situations. This is particularly important for consideration of dispersants and in-situ burning,

which present difficult analytical issues. The process focuses on ecological “trade offs” or cross-

resource comparisons. Through a structured analytical approach participants find “common

ground” for evaluating impacts and they develop defensible logic to support their conclusions.

The process is consistent with the U.S. Environmental Protection Agency’s (EPA) ERA

guidelines (U.S. EPA, 1998), but emphasizes development of group consensus among

stakeholders. The process uses a series of analytical tools specifically developed for use in a

group environment. It is designed as a planning and training tool and should not be used during


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an active spill event. However, knowledge gained by participants in the consensus-building

process facilitates real time decision making.

The situation evaluated in this CERA differed from those typically encountered in oil

spill planning in several important respects. First, the spill scenario is known and ongoing, and is

not hypothetical. Also, the release rate and the behavior of the spilled oil are understood, based

on the detailed studies of the spill site, and the historical release data available from the USCG

over-flights, so a detailed conceptual model is not necessary. Last, the CERA was used to

contrast ecological impacts of different response, remediation, and mitigation strategies, as

opposed to specific response technologies (i.e., in-situ burning and chemical dispersants). Long

term impacts were not assessed, but acute impacts were in order to support response decision

making. During the CERA process, it was necessary to adapt some of the tools typically used in

the analysis phase to account for those differences, as described in Section 2.0.

Training usually involves two 2- or 3-day workshops lead by a facilitator. The ideal size

is 25 to 30 participants, including spill response managers, natural resource managers and

trustees, subject matter experts, and non-governmental organizations. The goal is to achieve

consensus interpretations of potential risks and benefits associated with selected response options

based on a scenario developed by local participants. Time between the two workshops is used by

participants to research issues of concern before developing final conclusions. The process

focuses heavily on achieving a consensus interpretation of the available technical information.

Therefore, it is important to have broad stakeholder representation in the decision process;

otherwise, results may not be accepted by all stakeholders involved in an actual spill event. This

CERA involved a total of 45 participants, and utilized two 3-day workshops. The training that is

normally provided on the hypothetical oil spill scenario and response methods was replaced with

a series of presentations that described the actual site conditions and actions taken to date.

The workshop process typically includes three primary phases – problem formulation,

analysis, and risk characterization. Details of the process are described in Aurand et al. (2000).

In the first phase (prior to the first meeting) problem formulation, participants (usually a small

subgroup serving as a steering committee) develop a scenario for analysis, identify resources of

concern along with associated assessment thresholds, and prepare a conceptual model to guide

subsequent analysis. In the analytical phase, all the participants evaluate exposure and

ecological effects. The conceptual model, developed in the problem formulation phase, directs

the analysis using standard templates and simple analytical tools that define and summarize the

analysis for each resource of concern and each response option. Finally, participants complete a

risk characterization. During this phase, participants interpret their results in terms of the risks

and benefits of each response option to overall environmental protection as compared with

natural recovery (i.e., baseline). This CERA varied slightly from typical situations, since the

problem was well understood and scenario development was not necessary, but the activities

performed during the analytical and risk characterization phases were similar.

1.3 Participants

Attendees of the workshop fell into the following categories: steering committee

members; participants; technical resources; presenters; and observers. Steering Committee

Members were appointed by the UC, and were responsible for developing the scope of the

CERA, and recommending the workshop participants. The Steering Committee Members

represented the USCG, BSEE, TEC, and NOAA. Participants were individuals who were


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assigned to a focus group and actively participated in all phases of the CERA. Each of the

Participants represented an agency or organization that had jurisdiction, and/or expertise that was

relevant to the CERA. Technical Resources were individuals who had participated in previous

investigations at the site, or possessed unique technical skills relevant to particular remedies

being considered. Presenters were individuals, some of which were also Participants, who made

presentations during the plenary sessions on the results of previous investigations, remedies

being considered, or relevant laws and regulations. Observers were attorneys representing TEC

and the USCG or representatives from Federal and State agencies as stakeholders to the project.

Some individuals initially serving as Technical Resources or Observers were moved to

Participants to replace initial Participants that could not complete the process. Only Participants

were involved in ranking potential remedies being considered, and the development of consensus

recommendations from the focus groups and plenary sessions. A detailed list of attendees, their

affiliation, and their roles is included in Appendix A.

1.4 Organization of the Report and the Associated Compact Disc

This report is one of a series of files on a Compact Disc (CD) prepared as a project

deliverable product. The report summarizes the results of the workshops, and presents the

conclusions and recommendations of the participants. It is formatted to be printed as an

independent, double-sided report. In addition, the CD contains copies of the presentations made

at the workshops by the sponsors or by subject matter experts, as well as copies of documents

provided as reference material by the sponsors. These files are cited at appropriate locations in

the text of the report.


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2.0 Overview of Workshop Events

Following the UC decision to perform a CERA, as detailed in section 1.1, a Steering

Committee composed of representatives from the USCG, TEC, BSEE and NOAA was

established to tailor the CERA process to the unique circumstances presented by the TEC

scenario, plan the workshops, and recommend the CERA participants. The Steering Committee

convened approximately bi-weekly, beginning in late March, and continued to meet until

publication of this document.

2.1 First Workshop

The initial workshop meeting was held at the BSEE office location in New Orleans, LA

during May 13 – 15, 2013. Presentations were made by TEC, governmental representatives and

technical experts on subjects including the CERA process, incident command structure and

function, well decommissioning regulations, well visualization, geotechnical and acoustic

surveys, environmental analyses, sheen observations, site surveys and studies, and response

actions taken to date. Most presentations were included in a participant notebook and are

included in the CD accompanying the final report. In addition, many of the surveys and studies

described were made available to workshop participants as reference materials on site (see

Appendix B).

The first workshop began with welcoming remarks from Captain Peter Gautier (USCG

FOSC). Dr. Don Aurand (HDR) then reviewed the charge to the workshop participants (on the

CD as: “CERA Charge to Participants”), explained the contents of the participant notebook,

provided an overview of the CERA process (on the CD as “Introduction and Meeting

Overview”), and reviewed the schedule of activities for the workshop. An overview of federal

regulations that were relevant to the CERA was then provided by Capt. Gautier (on the CD as:

“USCG Presentation”), Mr. Dave Trocquet and Mr. Lynard Carter (BSEE) (on the CD as:

“BSEE Decommissioning Wells”), finally Mr. Mike Prendergast (BSEE), and Mr. Will Pecue

(TEC) presented two summary videos.

A review of the historic state of hydrocarbon releases at MC-20 was conducted by Dr.

Rich Camilli (Navistry, Inc.) (on the CD as: “GeoTechnical Acoustic Surveys”), and Mr. T.J.

Broussard (BSEE). A working lunch was provided, during which participants were divided into

three focus groups. The Steering Committee established the focus groups with attention given to

achieving a balance in representation between regulatory and technical personnel. The focus

groups then conducted an analysis of the baseline conditions. Each focus group appointed a

leader and a recorder as shown in Table 2.1.

Table 2.1 Focus Groups, Leaders and Recorders

Focus Group Leader Organization Recorder Organization

1 Jason Screws USCG Mike Parker Offshore Operators Committee

2 Jeff Dauzat LA DEQ Sean Fitzgerald USCG

3 Kyle Jellison NOAA Greg Masson USFWS


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Mr. Will Pecue described actions taken by TEC, which included the five phases of well-

decommissioning, the subsea containment system, and the establishment of the UC technical

workgroups (on the CD as: “Five Stages of MC-20 Decommissioning”). Mr. Bill Shedd (BOEM)

provided an overview of natural oil seeps in the Gulf of Mexico, and an analysis of the

probability of future mudslides (on the CD as: “Geophysical Indicators of Natural Seepage of

Hydrocarbons”). Mr. Charlie Henry (NOAA) and Mr. Prendergast described the roles, and

conclusions of the Sheen Source (on the CD as: “Sheen Source Technical Workgroup Results”)

and Well Review (on the CD as: “Overview of MC-20 Well Review Processes”) Technical

Workgroups, respectively. Day 1 concluded with a review of the state of hydrocarbon

contamination and releases at MC-20 by Dr. Chris Reddy (Navistry, Inc.) (on the CD as: “July

2012 Coring Acquisition and Forensic Analysis” & “February 2013 Dome Coring and Results of

Containment Reactivation”), and Mr. Don Shackelford (Halliburton) (on the CD as: “Possible

Sources for Low Volume Intermittent Gas Flow and Response Options”).

Day 2 commenced with a review of the state of hydrocarbon contamination and releases

at MC-20, by LCDR Lushan Hannah, USCG (on the CD as: “USCG Photo Presentation”). A

more detailed description of the CERA process was provided by Dr. Aurand that described the

structure and function of the three focus groups created on Day 1 (on the CD as: “CERA

Presentation”).

The full plenary session discussed the current situations at the site, and how that would be

used as the baseline for future analyses, involving a comparative analysis of the proposed

response options. This session resulted in a decision to make some modifications to the risk

assessment matrices including:

Replacing “Salt Marsh” with “Coastal Marsh”;

Adding birds to intertidal salt marsh sections;

Adding zooplankton to water surface sections;

Changing recovery rate categories in the Ecological Risk Ranking Matrix;

Adding a column for “safety” in the risk summary sheet; and

Removing “costs” from the risk summary sheet.

Each focus group conducted an independent analysis of ecological risks associated with

the baseline condition (Option 3, Natural Sedimentation) and the cumulative scores for the focus

groups are presented in Table 5.1.

The focus groups reconvened in a plenary session to discuss the analysis of the baseline

condition. It was at this point that the concerns with the proposed risk assessment matrix

discussed in Section 4.4 were raised. The facilitator led a full plenary session to develop the

alternative risk ranking matrix and process (Section 4.4) that was used for the remainder of the

CERA workshop. A scale was proposed, similar to the “pain scale” of 1 to 9, that medical

doctors often use (Table 4.3).

The remainder of Day 2 of the first workshop was spent evaluating the proposed response

options against the baseline condition using the modified risk ranking matrix. That process

continued into Day 3. By the end of Day 3, the focus groups had completed their analysis of the

three site remediation options, and the first two well intervention options. The results of those

analyses are provided in Attachments 2 through 4 of the CERA MC-20 Interim Report (on the

CD as: “Interim Report”).


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Day 3 of the first workshop concluded with a brief Steering Committee meeting to assess

the state of satisfaction with the modifications that had been made to the CERA process, and

review overall focus group progress.

During the time that passed between workshops, the Steering Committee continued to

meet bi-weekly. Discussions centered on the remaining two options that had not yet been

evaluated by the focus groups. Based on concerns raised by some of the participants during

Workshop 1, a decision was made to drop intervention and containment Option 3. Option 4 was

replaced with two new options for enhanced preparedness and response capabilities.

2.2 Second Workshop

The second workshop began with a review of the accomplishments of the first workshop.

NOAA trajectory model analyses for focus group consideration were provided (on the CD as:

“NOAA Trajectory Models”). A plenary session review of the Workshop 1 focus group scores

was conducted, and remaining response options were discussed. Focus groups reconsidered

materials from Workshop 1 and scored the remaining options. Focus groups presented their

scores for all options in a plenary session for further discussion.

Day 2 of the second workshop began with a review of technical and engineering

feasibility studies for all options. The focus groups were then asked to discuss the technical and

engineering feasibility studies, and reach conclusions regarding their impacts on their previous

response option evaluations.

During the afternoon of Day 2, the focus groups began the process of drafting their

individual consensus findings, conclusions, and recommendations. On the final day of the second

workshop, the focus groups reviewed their individual findings, and developed the workshop

consensus conclusions and recommendations for the MC-20A CERA, which are presented in

Section 6.0. The second workshop concluded with a review of the report preparation and review

process, and closing comments from the Steering Committee.


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3.0 Background Information

The material in this section is summarized primarily from TEC (2013). It is presented in

chronological order. The final section, Section 3.4.7, dealing with February 2013 survey results

is based on unpublished material presented at the workshop.

3.1 The MC-20A Platform Accident – September 2004

TEC’s MC-20 Platform was installed in 1984 at a location about 10 miles southeast of

the mouth of South Pass of the Mississippi River in Block 20, Mississippi Canyon Area (see

Figure 3.1).

Figure 3.1 General Location Map of MC-20 (Provided by USCG)

The water depth at the site was about 480 ft. in 1984. The MC-20A Platform was a jacket

structure, supported by 8 piles, each 72 inches (in.) in diameter, with 28 well slots. The platform

dimensions at the seafloor were about 225 ft. by 160 ft. According to the regional bathymetry,

the site was at the bottom end of a comparatively steep slope, within a low embankment-like

feature situated between two higher mudflow lobes that extend seaward on either side of the site

(see Figure 3.2). At the time of the design and installation of the MC-20A platform it met or

exceeded all regulatory requirements for new platform installations in the GOM.

In September 2004, Hurricane Ivan entered the GOM, passing about 60 miles east of

MC-20. Ivan alternated between Category 4 and Category 5 classifications as it traveled

northwards towards the coast, with maximum wave heights near 100 ft. and peak wave periods

near 18 seconds. Those wave heights and wave periods were much larger and longer than those

wave conditions used in structural designs for the Eastern GOM.


14

Figure 3.2 Site Location and Regional Seafloor Bathymetry Map (FMMG, 2006)

The platform was toppled by a regional slope failure, or unprecedented large-scale

mudslide, during Ivan and now lies about 550 ft. downslope and southeast from its original

location. Observations of the jacket using a Remotely Operated Vehicle (ROV) showed that the

exposed face of the jacket protrudes only 5 to 10 ft. above the seafloor. This suggests that the

remainder of the jacket is buried to depths of about 150 to 155 ft. below the seafloor.

Actual movement distance of the jacket was about 700 ft. The post-failure drawing on

Figure 3.3 shows the relationship between the original orientation of the platform and its current

toppled position with the base facing northeast and the top deck facing southwest.

Water depths are now about 440 ft. at the original platform location and about 445 ft.

where the platform is resting. The original site is now covered by about 40 ft. of new sediment

that is part of a regional seafloor failure described in Fugro-McClelland Marine Geosciences

(FMMG) (2005). The ROV survey also showed that all four of the exposed piles broke close to

the bottom of the jacket pile guides.

TEC performed field studies to determine the locations of the 30-in. diameter well

conductors. The 30-in. conductors act as the outer (structural) tubular component for each of the

28 wells drilled from the MC-20 platform. The conductors were apparently pulled from the

jacket during the post-failure movements of the platform. Using a drill string that penetrated

beneath the seafloor, the drill string was moved up and down vertically while the drilling vessel


15

Figure 3.3 Original Position vs. Post-Failure Position Following Hurricane Ivan (FMMG,

2006)

traveled along a path. This probing operation continued until the drill string contacted some of

the conductors.

The location and depth at the point of contact was recorded then the operation was

repeated. These studies suggest that the conductors are now strung out in a southeast direction

from the original conductor well bay location towards the base of the jacket wreckage, along the

line shown on Figure 3.3. Depths to the conductors are about 153 ft. below the mud-line (BML)

at the original conductor well bay, and about 69 ft. BML where they were encountered close to

the jacket wreckage, relative to the present seafloor (or about 110 ft. BML at the original

conductor well bay area relative to the 1982 seafloor). The 28 conductors were located on the

MC-20A platform in a 4x7 row grid, with 7-1/2 foot center spacing between each conductor.

Field evidence suggests that these buried conductors remain in a tightly spaced bundle. This

evidence suggests that as the platform toppled the conductors were pulled out near the bottom of

the toppled platform jacket and all buried well conductors still remain in the original 30 ft. x 53

ft. pattern with the (open) end of the conductors just outside the toppled platform on the

northwest side.


16

The profile view of the buried well conductors, developed by TEC, is shown in Figure

3.4. Note the decreasing depth of burial as the conductors move away from the original platform

location (left) towards the current location of the toppled platform (right).

Figure 3.4 Profile View of Buried MC-20A Well Conductor (FMMG, 2006)

3.2 Initial Environmental Investigations

A number of environmental and geophysical investigations have been undertaken by

TEC since the time of the platform collapse. Individual reports are listed in Appendix B and

were made available to the participants during the workshops. These studies occurred from 2004

to 2012, before, during, and after well intervention and containment activities. They are

discussed here in two broad groups, initial and recent environmental investigations.

From November 2004 to November 2006, water column anomalies (interpreted as gas

bubbles, fresh water, and sediment plumes) were detected by a Sub Bottom Profiler. In May

2007, a high resolution geophysical survey conducted by FMMG inferred that the venting was

directly related to the MC-20A wells and the fallen platform. Geotechnical investigations using

piezoprobe tests (a device which measures soil pore pressure and soil pressure dissipation) were

conducted in June 2007, which concluded that hydrocarbon contamination was observed in mud

line samples (at depths of 2 ft.) in the well bay area, and at all “Halibut Basket” (a device which

measures in-situ shear strength of near-seafloor, soft cohesive soils) testing locations. Traces of

hydrocarbons were also observed in samples recovered below the mud line to a depth of 78 ft. in

one boring. In December 2007, at the request of the MMS, predecessor to BOEM and BSEE,

TEC initiated a three phase study that consisted of:

{Attempted}

Well Bay


17

Phase I: Evaluation of the water column;

Phase II: Sediment sampling; and

Phase III: Evaluation of sediment hot spots identified in Phase II.

In Phase I, a total of 67 hotspots were found using ROVs and a mass spectrometer. Of

these, six were recommended for further sampling in Phase II. Phase II sampling utilized an

ROV fitted with a jet nozzle to disturb bottom sediments, which were then analyzed by mass

spectrometer. The results of Phase II led TEC to conduct Phase III studies, which determined the

degree of hydrocarbon exposure through water and sediment sampling. The Phase III study

identified three discrete plumes, labeled A, B, and C. Additional findings were as follows.

1. Phase I, II, and III surveys were self-consistent, suggesting that the greatest

hydrocarbon signature was found near the platform’s original wellhead (well bay)

area.

2. Hydrocarbon ion peak intensity, temperature and salinity data collected during the

Phase I survey suggested an active hydrocarbon leak in this well bay area.

Specifically, the highest hydrocarbon intensities were collocated with bathymetric,

temperature, and salinity anomalies, suggesting that oil, natural gas, and produced

water were actively venting from discrete locations in the seabed (Plumes “A” and

“B”).

3. Phase II contaminated sediment surveys indicated significantly higher hydrocarbon

intensities than Phase I water column surveys, suggesting sediment areas were

contaminated with hydrocarbons. The use of the high pressure pump with jet nozzle

to disturb the sediment near the surface of the seafloor was appropriate. It adequately

transported sediment hydrocarbons into the water column, enabling high-resolution

mapping of sediment hydrocarbon distributions by the mass spectrometer.

4. Hydrocarbon signature from the Phase II survey of sediments varied spatially by

more than 10,000 times in intensity across the survey area.

5. The highest hydrocarbon intensities were generally found within the excavated basin

around the well bay area. It is unclear if this was caused by heavy oil components

pooling in the basin (from the plume), or if these higher contaminated sediments were

exposed during the excavation process.

6. A lower intensity contamination site appeared to be actively venting hydrocarbons

(Plume “C”) near the base (north-east side) of the platform jacket. This site was

visually confirmed to be emitting a small volume of gas at the mud-line.

Additional biological assessments were conducted in August 2008 at the request of

MMS. These were intended to assess impacts to benthic ecology and fisheries. The very loose

sediments at MC-20 did not allow for effective sampling of the benthos. The fisheries study

concluded that “there is an acceptable risk to humans if fish from the MC-20 area are

consumed”.

3.3 Response Activities to Date

TEC commenced the first phase of its decommissioning operation in December 2008

starting with abandonment of its sales pipeline. The second phase, involving the drilling of


18

intervention wells to allow for plugging of those MC-20A wellbores which posed a high

environmental risk commenced in December of 2009 and continued until March 2011 when the

ninth well intervention was completed. The third phase which removed the MC-20A production

deck, took place in June 2011 and the fourth phase of subsea debris collection concluded in July

2011. The potential fifth phase (Site Remediation) is a subject for the CERA process.

In the summer of 2008, prior to the commencement of the first intervention well, the

USCG issued an Administrative Order (USCG, 2008) to TEC requiring the following actions: (1)

immediately deploy an open water skimming asset to mitigate the continuous discharge at MC-

20A until such time that pollution domes are installed; (2) conduct over-flights twice daily to

monitor the discharge from MC-20A and provide the USCG with reports from these over-flights;

(3) install pollution domes to mitigate the continuous discharge in MC-20A no later than

November 1, 2008; and (4) provide an updated Incident Action Plan (IAP) reflecting all

requirements of the administrative order.

By the time the Subsea Containment System was built and ready for deployment, the first

intervention well operation involving the plugging of MC-20 well A-21 had successfully

eliminated Plume B, one of the two oil plumes in the former well bay area where the platform

had originally been located. As a result, the installation sequence allowed Dome A to be installed

over the remaining oil plume (A) in the well bay area, and Dome C to be installed over the

observed gas Plume C near the toppled jacket. While installing Dome C, a small gas emission

was observed from the mud line approximately 20 ft. from Dome C. TEC elected to install the

surplus dome over this emission point and designated it Dome D. The initial (and maximum)

collected oil volume from the containment system (three domes) was approximately 2-3/4

bbl/day (110 gal./day).

On July 28, 2009, the FOSC permitted over-flights to be reduced to once daily based on

the installment of pollution domes in April 2009.

As TEC’s well intervention program continued, sonar observations made with the drilling

rig’s ROV documented further success in the reduction/elimination of the remaining MC-20A

plumes identified in the Come Monday report (2008). Accordingly, collected oil volume has also

been reduced to the point where Dome A and Dome D are now disconnected from the collection

system. At present time, only Dome C remains flowing into the Subsea Containment System

with slightly over 1 bbl. (46 gal.) of oil collected in the 15 months that spanned January 2012

through March 2013.

On March 15, 2012, an IAP (USCG, 2012) was signed by USCG, BSEE, BOEM, and

TEC that outlined charters for Sheen Source and Well Review Work Groups and operational

procedures for monitoring sheens, response thresholds and maintenance of the containment dome

system. The findings of those work groups are included in section 2.2. The UC established the

IAP as the "living document" and official record of the response, with additions/updates as

necessary, including a continuous Incident Command System 214 incident log. On June 25,

2012, an Administrative Order (001-12) was issued to TEC to begin the design and planning for

a new pollution dome system that would be suitable for the environmental conditions found at

the MC-20A discharge site, and submit a written plan that shows a projected timeline for

fabrication and installation to the UC no later than September 1, 2012. Subsequent to TEC

demonstrating that there was no existing system that could eliminate all surface sheens, that

order was amended on November 26, 2012 to require reinstitution of a containment dome system

to capture oil from the MC-20A discharge site and develop a sampling plan for obtaining


19

samples from the oil/gas separator and the area beneath and in the vicinity of containment Dome

C.

The UC agreed to put plans for re-design of the containment system on hold, pending

consideration of the findings of the CERA.

3.4 Recent Environmental Investigations

Following the decommissioning operations described in Section 3.3 above, side-scan

sonar surveys were conducted in June 2010 and June 2011 to confirm that the observed plumes

had been eliminated. The 2011 study also involved the use of divers. Neither sonar nor divers in

either study observed hydrocarbon flow conditions in the study area.

3.4.1 Creation of Well Review and Sheen Source Work Groups – February 2012

In early 2012, the UC commissioned two technical subcommittees with experts from

TEC, BSEE, and USCG (along with NOAA) to review two specific areas. One technical group

was to review the technical risks of further intervention on the remaining 16 wells. The second

work group was instructed to determine the source of the ongoing surface sheen at MC-20.

3.4.2 Recommendations from the Well Review Work Group

For each individual well, the subcommittee members completed a comprehensive

assessment which included: reservoir parameters and a determination on the well’s ability to

flow; historical production history including present gas and oil contact depths; the existing

wellbore components and safety devices; followed by a detailed review of all drilling-related

risks involved with well intervention on that specific well.

The Well Review Work Group then arrived at a consensus position on probability and

consequence of an environmental event for the well in its current state, versus the probability and

consequence of an environmental event for the well, should well intervention be attempted. In

addition, the Work Group determined a consensus Probability of Success (PoS) for the well’s

potential well intervention operation. In 15 of 16 wells reviewed, the Work Group concluded that

additional well interventions would result in either a higher probability of an adverse

environmental event or a worse consequential environmental event, or both.

The Work Group also concluded that the PoS for the remaining well interventions ranged

from a low of 6% PoS (2 separate wells) to a high of 42% PoS with the average PoS over the 16

remaining wells at 21.6%, or a 1-in-5 chance of success.

3.4.3 Recommendations from the Sheen Source Work Group

The Sheen Source Workgroup attempted to answer three basic questions:

What is the source?

What is the environmental impact of the continuing release from the site?

What are the options available for potential mitigation?


20

They attempted to answer these questions by soliciting a wide range of different

questions from the participants and members of the UC, reviewing current information from

existing studies, and developing follow-up investigations to fill any knowledge gaps. They

concluded that based on the existing studies, there appears to be more than one source, and that

releases occur on both an episodic, and relatively continuous basis. The environmental impacts

were thought to be comparable to those associated with natural seeps, but that subject was left

for further analysis by the CERA workshops. There was general agreement that natural

sedimentation processes are occurring, and that the associated natural “capping” process could

have mitigating effects, but there was not agreement on how long that process could take.

3.4.4 NOAA Acoustic Survey – June 2012

Early in the summer of 2012, the NOAA M/V Okeanos Explorer was commissioned to

perform an acoustic survey at the MC-252 Macondo site. BSEE/BOEM requested that should

time allow, the vessel should stop at MC-20 and perform an acoustic survey there as well. After

correcting the original acoustic dataset for recording issues, the sonar dataset found an acoustical

feature originating at the Subsea Collector/Separator (most likely indicating vent line discharges

of gas; where collected gas is separated from the collected liquids and discharged into the water

column) and continuing to the water’s surface with a northward drift. This survey found no other

acoustic anomaly in the water column at MC-20.

3.4.5 Soil Sampling and Chemical Forensic Analysis – July 2012

Initially there was doubt whether the continuing sheen (post commissioning and

containment system installation) was due to release from a leaking well that had not been

plugged (primary source) or a release from sediments containing oil (secondary source).

Accordingly the first new site investigation (in July 2012) was essentially targeted toward

collecting data to verify the source. One of the factors influencing the goals of this sampling

event was the aforementioned multi-beam sonar survey by the NOAA vessel Okeanos Explorer

at the site in mid-April which reported a water column feature consistent with a gaseous release

with bubbles breaking at the surface creating an oily sheen. The July 2012 site investigation

included the following: 1) bottom sediment sampling at twelve locations using both box type

samplers (collecting top one foot of soils) and piston coring (collecting top 5 meters) techniques;

2) collection of sheen samples with forensic chemical comparison against the sediment samples

and prior containment system samples (June 2010); and 3) and acquisition of new data on

reservoir oils in an adjacent producing block (MC-21). The methodology and protocols to be

used in the data acquisition and interpretation were discussed and reviewed beforehand with the

Sheen Source Workgroup members.

3.4.6 July 2012 Sampling Program Results

Sediment samples were taken at different depths in the area of the well bay,

approximately 40 and 50 ft. from containment Dome C, and control samples locations. The

results generally tracked the same outcome as had been determined during the 2007 sampling

program.


21

The highest concentration of petroleum hydrocarbons occurred in the samples collected

in the well bay area. Some of these samples exhibited concentrations as high as 4% by mass.

Typically the hydrocarbon concentrations varied with depth of sediment in that the higher

concentrations occurred in the top 4 meters of the more contaminated sediments although the

concentrations in the very near surface sediments appeared to be less than reported in the 2007

survey.

Sheen oil was collected at three different times during the July 2012 sampling event. It

was determined that the sheen oil collected at the start of the exercise (prior to any bottom

disturbance to collect sediment samples) did not match the oils that were in the sediments from

the well bay.

There was a somewhat closer match between the sheen oil collected after bottom

disturbance with the oil in the sediments. Both the USCG Marine Safety Laboratory and Alpha

Laboratory (used by TEC) conclusions indicate that there was a match between sheen oil and

samples of containment system oil collected by the USCG in June 2010. It was determined that

the oil (in the sheen) weathered in a distance of less than one kilometer and in a time of less than

one hour from the sheen’s origination point on the water’s surface.

Different reservoir samples were collected during May 2012 at the neighboring MC-21

platform in an attempt to get a surrogate match for MC-20 reservoir oils that were no longer

available for comparison purposes. There was a high degree of variability in these samples and

the Sheen Source Workgroup determined these results would not be useful in ascertaining the

origin of the surface sheen at MC-20.

3.4.7 February 2013 Sampling Program Results

The following section provides results of sampling efforts that were not available at the

time of the distribution of the "read ahead" document prepared by Taylor Energy Company, LLC

(on the CD as “Read Ahead Material”). The results were presented on Day 1 of the first

workshop by Dr. Chris Reddy.

In February of 2013, a follow-up sampling program was commenced which focused on

acquiring core samples in the area immediately adjacent to Containment Dome C. Because

divers were not used in the July 2012 operation, the closest a piston core sample could be taken

was 20+ ft. from the containment dome. The 2012 sample nearest Dome C showed a near-

absence of oil, i.e., the concentrations were 75 ppm or lower. In assessing this and other samples,

in the MC-20 dataset, background was defined as 250 ppm of oil. As a point of reference, the

open-end of the well conductors are thought to be roughly 69 ft. below the C dome.

Using saturation divers in the February 2013 operation, Taylor obtained four additional

“push” cores to an approximate depth of 4 ft. on each side of the 10.5 ft. square containment

dome. Sheen samples were also collected in the February 2013 operation, just as in the July 2012

samples, and sent for analysis to the USCG Marine Safety Laboratory.

All four dive cores collected directly adjacent to Dome C were found to have very high

hydrocarbon levels, showing concentrations up to 250,000 ppm. The sediments were found to

vary in composition, both vertically and horizontally, near the containment system. The dive

cores (1-4) were genetically similar and had a wide range of A/B ratios (a diagnostic ratio used

by USCG and Taylor Energy’s contract laboratory to differentiate oil types) pointing towards

multiple primary sources of oil to these sediments. It was concluded that some of the dive cores


22

and sheen samples share a common source. The Coast Guard’s Marine Safety Laboratory

reached a similar conclusion.

Given the variation in composition and concentration among the four cores around the

10.5 ft Dome C, there is no evidence of source recharge. This conclusion is supported by the lack

of homogeneous contamination. Additionally, the maximum oil concentration was found at 2-3

ft. in core depth in three of the four cores. At the deepest depths of these core samples the oil

concentration was less. A recharge situation would show the greatest concentrations of oil at the

lowest interval collected.

In addition to core and sheen samples, gas samples were also obtained from within the

Containment Collector/Separator. The gas sample taken from the vent line of the

Collector/Separator found little evidence of oil suspended in the gas column. The gas sample was

then sent to Isotech Laboratories for a point-of-origin determination and was found to be from a

microbial gas source, and not from a thermogenic or “natural gas” source associated with deeper

gas-bearing reservoirs.


23

4.0 Elements of the CERA Process

The CERA facilitator (HDR) described all elements of the CERA process to the

workshop participants and proposed tools and forms that could be used to assist in each phase.

As was noted earlier, this CERA differed from traditional CERAs in that much of the

information typically provided in a hypothetical scenario was already known based on the

existing situation and environmental studies. Also, the response options being considered did not

include traditionally evaluated response tactics such as dispersants and in-situ burning. As a

result, situational information was provided through technical presentations to all participants.

The workshop participants were then divided into three focus groups, of approximately equal

size and composition, and each focus group evaluated all response options being considered,

using the same CERA processes and tools. The following sections provide a description of the

processes and tools used in typical CERAs, and how they were used, or modified for this CERA.

4.1. Geographic Area of Concern

When using the CERA process for oil spill planning activities, the geographic area of

concern is usually estimated by modeling the hypothetical geographic extent of an oil slick

resulting from a potential oil spill scenario. In the case of the MC-20A CERA, the geographic

scope of the ongoing oil sheen was known, based on historical over-flight data. Impacts of oiling

to particular species or populations could extend beyond the physical perimeter (i.e., birds could

be coated at MC-20, and then migrate to a nesting area), so a three-tiered scale was proposed to

assess the geographic component of potential ecological impacts. The categories proposed were:

1. Local (L)

Restricted to the immediate vicinity of MC-20 (approximately 3 miles radius around

the site)

2. Regional (R)

Central Gulf of Mexico

3. Gulf of Mexico (G)

These categories, in conjunction with the relative percentage of an environmental

resource that is likely to be impacted determine the magnitude of the risk to “resources of

concern.” When the focus groups attempted to use this scale, however, it quickly became

obvious that impacts to almost all organisms would fall into the “Local” category, so the scale

would have little value in contrasting the impacts of the different response options being

considered.

4.2 Resources of Concern

The Resources of Concern are those organisms, populations, or habitats that occupy the

geographic area of concern, and could be at risk if exposed to an environmental stressor (i.e.,

coating from oil sheen or hydrocarbon toxicity). These are typically identified through use of a

resource table. This table design for this CERA was somewhat simpler than many, given the

limited resources at risk and the final version is presented in Table 4.1.


24

Table 4.1 MC-20 Resources at Risk

Resources at Risk Table

REGION HABITAT RESOURCE CATEGORY

Intertidal Coastal Marsh Macrovegetation

Invertebrates

Fish

Birds

Open Marine Environment Benthic Infauna

Epifauna

Water Column Birds

Mammals

Sea Turtles

Fish

Adult shellfish/other invertebrates

Zooplankton (incl. larval fish or invertebrates)

Water Surface Birds

Mammals

Sea Turtles

Fish

Zooplankton (incl. larval fish or invertebrates)

4.3 Conceptual Model Matrix

The conceptual model is a depiction of how various ecological resources might respond

when exposed to stressors. In a typical CERA, the response techniques themselves would be

stressors, in addition to the oil that would remain in the environment if no response actions were

taken. For example, in situ burning introduces additional hazards of heat and air pollution.

Hazards that are typically evaluated include air pollution, aquatic toxicity, physical trauma (i.e.,

trampling or boat strikes), oiling or smothering, thermal, oil contaminated waste materials, and

indirect (i.e., ingestion of contaminated food). For the MC-20 CERA, the participants concluded

that none of the response options evaluated significantly increased the magnitude of any of those

hazards, and elected to utilize a simple, single dimension risk scale that aggregated hazards from

all sources. This allowed assignment of a single risk score for each of the resources at concern

for each of the three focus groups. The form used to record those scores is shown in Table 4.2.


25

Table 4.2 TEC Ranking Sheet (Conceptual Model Matrix) used for the Baseline Analysis

4.4 Risk Ranking Process

A risk ranking process is used to compare and contrast levels of concern about the

potential interaction of resources of concern and stressors that could occur with each of the

response options evaluated. The process is facilitated by the use of a risk ranking matrix, in

which each axis of the matrix represents a parameter used to describe risk. Typically, the

parameters used are the magnitude of potential impacts, which ranges from severe to trivial, and

the recovery potential, which ranges from reversible to irreversible. The risk ranking matrix that

was originally proposed for this CERA was a 4x4 matrix, illustrated in Figure 4.1.

Alternative

S

ea T

urt

les

M

am

mals

C

onsensus L

evel of

Concern

Score

A

dditio

nal A

dvers

e E

vent

Lik

elihood

Score

I

nfa

una

E

pifauna

B

irds

Evalu

ation

Facto

rs

Potential Options

Open Marine EnvironmentIntertidal

Coastal Marsh

Region

Habitats

B

irds

A

dult s

hellfish/o

ther

invert

ebra

tes

Z

oopla

nkto

n (

incl. larv

al fish o

r in

vert

ebra

tes)

B

irds

S

ea T

urt

les

Benthic

F

ish

F

ish

Z

oopla

nkto

n (

incl. larv

al fish o

r in

vert

ebra

tes)

M

acro

vegeta

tion

I

nvert

ebra

tes

Water SurfaceWater Column

M

am

mals

F

ish

Gro

up

Group 1

Group 2

Group 3


26

RECOVERY

>5 years (1) 1 to 5 years (2) 1 month to 1 year (3)

<1 month (4)

% o

f R

ESO

UR

CE

AFF

ECTE

D

> 50 % (A)

1A 2A 3A 4A

20 to 50% (B)

1B 2B 3B 4B

1 to 20% (C) 1C 2C 3C 4C

< 1% (D) 1D 2D 3D 4D

Legend: Dark Red cells represent a “high” level of concern, bright red cells represent a moderately high level of

concern, orange cells represent a “moderate” level of concern, yellow cells represent a moderately low level of concern,

and green cells represent a low level of concern.

Figure 4.1 Ecological Risk Ranking Matrix

Using this matrix, a score of 1A would represent the highest level of ecological concern,

and 4D the lowest. Each resource is assigned a score, and then those scores are combined and

averaged to obtain a composite score for a larger category of resources such as a habitat type.

Color coding is useful for comparing rankings produced by different focus groups that are

aggregated into the larger conceptual model matrix. It is important to note that all risk scores are

dimensionless numbers that represent the level of concern relative to the baseline, no action

alternative. The baseline condition was Site Remediation Option number 3 (CURRENT

SEDIMENTATION), see Section 4.5.1. When the focus groups evaluated this natural

sedimentation alternative, scores for all resources were determined to be in the lowest (green)

category of concern, as discussed in Section 5.3.

When the Focus Groups continued to rank the other response options, however, the

participants concluded that the ranking matrix lacked sufficient sensitivity to discriminate

between anticipated ecological consequences associated with the various alternative courses of

action because all ecological impacts appeared to fall into the lowest category. In general, use of

the forms and scales that were initially proposed for use resulted in all options being rated in the

very low end of the “percentage of resource affected” scale. The participants also had difficulty

in utilizing the “recovery time” criterion, since it implies that an exposure to a stressor has ended,

and the oil sheen resulting from the downed TEC platform is ongoing, albeit very limited. For

these reasons, the proposed ranking matrix was not used for the remaining six options, and was

replaced with a simple, one dimensional scale of 1 to 9, where larger numbers indicated higher

levels of concern. For the two lowest and highest categories (i.e., 1, 2 and 8, 9), focus groups

were required to record the rational for selection.

The baseline condition (natural sedimentation) was assigned a value of 5 (using the

modified scale), so that alternatives could be ranked as either 1 to 4 levels of concern above or


27

below current conditions. When using this approach, focus groups still considered geographic

and population impacts, but did not use the original ranking system and were also free to discuss

other factors, more specific to each resource of concern. The modified risk ranking scale used is

depicted in Table 4.3.

Table 4.3 Modified Risk Ranking Scale

Worst 9 Document

8 Document

7

6

Baseline 5

4

3

2 Document

Best 1 Document

Use of this scale resulted in a single number that indicated the level of concern for each

environmental resource at risk, for each response option considered. The focus groups then

examined all scores for each resource category, and arrived at a single score that was

representative of overall risk for that resource category.

4.5 Response Options Considered

The response options proposed at the beginning of the first workshop are illustrated in the

following sections. After some discussion, consensus was reached early in the first workshop

that these were valid and appropriate options, and no additional options were suggested. Using

the modified risk ranking process described above, each of the focus groups began the process of

ranking all options during the first workshop. Each of the focus groups completed their analysis

of the three site remediation options, and the first two intervention and containment options.

4.5.1 Site Remediation Options

1. Excavation of contaminated sediments; onshore disposal – DREDGE/DISPOSE

2. Using non-contaminated Outer Continental Shelf sediments transported from another

site and deposited over contaminated MC-20 sediments – DREDGE/CAPPING

3. No excavation of contaminated MC-20 sediments, utilize ongoing/current

sedimentation process to cover contaminated MC-20 sediments – CURRENT

SEDIMENTATION


28

4.5.2 Intervention and Containment Options

1. Intervention on All Remaining Wells (two options, the second is an Adverse

Outcome Case) – IW: ALL WELLS

2. Intervention on Remaining Wells with de minimus Flow Potential (two options, the

second is an Adverse Outcome Case) –: POTENTIAL FLOW

3. No Further Intervention Wells - Non-Refundable Mitigation Offset Payment– NO

IW: MITIGATION $$

4. No Further Intervention Wells – Re-Design of Subsea Containment System – NO IW:

NEW CONTAINMENT

In closing discussions for Workshop 1, however, it became apparent that intervention and

containment options 3 and 4 were not well understood, and would be difficult to rank using the

existing methods. Several participants noted that it would be difficult to assess the ecological risk

associated with those options because the actual actions to be taken were not defined. In

addition, It was suggested that financial costs associated with Option 3 (NO IW: MITIGATION

$$) should not be used as a decision criteria for this CERA, and the option should be removed,

which was agreed to by the Steering Committee. It was also recommended that Option 4 be split

into two options addressing improving preparedness and response capacity and the Steering

Committee agreed to the following revised options 3 and 4:

3. EXPANDED RESPONSE CAPABILITY to reduce the current sheen by greater than

or equal to 75% using best available technology to enhance the containment solution.

4. EXPANDED PREPAREDNESS CAPABILITY by planning, developing, and having

ready for deployment a containment solution for the worst case discharge

(approximately 200 bbl/day).


29

5.0 The Results of the CERA

5.1 Results of the First Workshop

The preliminary conclusions reached during the first workshop are included below.

GROUP 1

1. Under current conditions, the existing sheens are expected to be persistent, yet

localized with an overall low level of risk.

2. The cumulative impact to baseline conditions in the Gulf of Mexico or (CPA) is

negligible.

3. The uncertainty and risk associated with options is greater than or equal to any long-

term gain to the environment.

GROUP 2

1. Daily sheens are in conflict with Clean Water Act but current ecological risk is low.

2. Well intervention option adverse outcome outweighs benefit due to potential of cross-

flow, catastrophic loss of well and the drilling activity.

3. Dredging options ecological risks outweighs potential gains.

GROUP 3

1. The overall greatest exposure and effect was physical contact to avian and mammals

(Water surface species -larva, small fish, coral spawn)

2. If impact occurs, there will be a moderate impact to localized populations of adult

mammals and birds however there is a low probability of this occurring.

3. There is accretion of sediments with slight possibility of episodic short term events

with associated releases.

These formed the basis for continuing discussions on areas of consensus during the second

workshop. The evaluation of ecological risk posed by the current situation was also conducted

during the first workshop, and is included in the following sections.

5.2 Evaluation of the Current Situation

The evaluation of ecological risk associated with the current conditions at MC-20 was

conducted by each focus group during the first workshop. The results from each focus group are

presented in Table 5.1.

In Workshop 2, these rankings were revisited within the focus groups, using the modified

risk assessment methodology. This option was considered the baseline option and was given a

score of 5 on a scale of 1 to 9. That rating is contrasted to those for the additional options in

Tables 5.2 through 5.4.


30

Table 5.1 Modified Risk Ranking Scale

5.3 Evaluation of Potential Response Options

Each of the focus groups evaluated all remaining options using the modified risk analysis

scale. Results from each focus group are included in the tables below. Note that Focus Group 1

chose to differentiate between long- and short-term effects for some site remediation options.

Remaining focus groups chose to utilize a single score to represent overall concerns, including

short- and long-term impacts.

R R R R L L L L L L L L L R R R L

4D 4D 4D 4D 3D 3D 4D 4D 4D 4D 4D 4D 3D 4C 4C 4D 4C

R R R R L L N/A R R R R R R R R R R

4D 4D 4D 4D 1D 4D 4D 4D 4D 4D 3D 2D 4D 4D 4D 3D

L L L L L L G G G G L G G G G L

4D 4D 4D 4D 4D 4D 4D 4D 4D 4D 4D 4D 4D 4D 4D 4D

Gro

up

Group 1 4C

Group 2

Group 3

M

acro

vegeta

tion

I

nvert

ebra

tes


M

am

mals

F

ish

Coastal Marsh

Region

Habitats

B

irds

A

dult s

hellf

ish/o

ther

invert

ebra

tes

Z

oopla

nkto

n (

incl. larv

al fish o

r in

vert

ebra

tes)

B

irds

Benthic

Z

oopla

nkto

n (

incl. larv

al fish o

r in

vert

ebra

tes)

A

dditio

nal A

dvers

e E

vent

Lik

elih

ood

Score

I

nfa

una

E

pifauna

B

irds

Evalu

ation

Facto

rs

Potential Options

F

ish

S

ea T

urt

les

S

ea T

urt

les

F

ish

Current Sedimentation (Status Quo)

M

am

mals

C

onsensus L

evel of

Concern

Score



31

Table 5.2 Detailed Risk Analysis Results - Group 1

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5

5 5 5 5 6 6 4 4 4 4 4 4 2 3 3 4 3

5 6 5 6 8 8 6 5 5 6 7 6 7 6 6 5 5

5 5 5 5 3 3 4 4 4 4 4 4 2 3 3 4 3

5 5 5 5 7 7 5 5 5 5 5 5 5 5 5 5 5

5 5 5 5 5 5 4 4 4 4 4 4 2 3 3 4 3

8 7 7 8 6 6 6 6 6 6 7 7 8 7 8 6 8

5 5 5 5 5 5 4 4 4 4 4 4 2 3 3 4 3

8 7 7 8 6 6 6 6 6 6 7 7 8 7 8 6 8

5 5 5 5 5 5 5 5 5 5 5 5 4 5 5 5 5

6 5 5 6 5 5 5 5 5 5 5 5 6 6 6 5 6

Dredge/Capping - long term

Dredge/Dispose - long term5 6 4 3

4

I

nfa

una

E

pifauna

B

irds

5

3 4 34

6

3

5

8

4

8

6

C

onsensus L

evel of

Concern

Score

5

7

6

Evalu

ation

Facto

rs

4

A

dditio

nal A

dvers

e E

vent

Lik

elih

ood S

core


Coastal Marsh

Region

Habitats

Dredge/Capping - short term

Site R

em

edia

tion

Options

5

B

irds

M

am

mals

Current Sedimentation

Dredge/Dispose - short term6

Inte

rvention a

nd C

onta

inm

ent

Options

6

5

5

NOIW: New Containment

5

5

IW: All Wells

IW: Potential Flow

5

Adverse Outcome Case


75% Sheen Reduction

5

2

4

3

8

38

4

5

6 5

8 6

5

6

5

Benthic

M

am

mals

6

5

5

5 5

6 8

M

acro

vegeta

tion

Z

oopla

nkto

n (

incl. larv

al fish o

r in

vert

ebra

tes)

B

irds

Z

oopla

nkto

n (

incl. larv

al fish o

r in

vert

ebra

tes)

I

nvert

ebra

tes

6

5

8

4

7

5

Group 1 Recorder: M Parker Leader: J. Screws

Potential Options

F

ish

S

ea T

urt

les

S

ea T

urt

les

F

ish


F

ish

A

dult s

hellf

ish/o

ther

invert

ebra

tes


32


5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5

7 7 7 7 9 9 N/A 6 7 8 7 7 7 7 8 7 7

6 6 6 6 7 7 N/A 6 6 6 6 6 6 6 7 6 6

6 6 6 6 7 7 N/A 6 6 6 6 6 6 6 7 6 6

9 9 9 9 8 8 N/A 8 8 8 8 8 9 9 9 9 9

6 6 6 6 6 6 N/A 6 6 6 6 6 6 6 7 6 6

9 9 9 9 8 8 N/A 8 8 8 8 8 9 9 9 9 9

5 5 5 5 5 5 N/A 4 4 4 4 4 4 4 4 4 4

6 6 6 6 6 6 N/A 6 6 7 7 7 6 6 6 6 6

Group 2 Recorder: S. Fitzgerald Leader: J. Dauzat


F

ish

A

dult s

hellf

ish/o

ther

invert

ebra

tes

Potential Options

F

ish

S

ea T

urt

les

S

ea T

urt

les

F

ish

9

6

4

6 6

9 8

6

6

4

8

8

6

9

6

7

Inte

rvention a

nd C

onta

inm

ent

Options

8

7

6

EPC: Expanded

Preparedness

5

6

IW: All Wells

IW: Potential Flow

5



ERC: Expanded Response

6 6

Region

Habitats

Dredge/Capping

Site

Rem

edia

tion

Options 5

B

irds

M

am

mals


Dredge/Dispose7

Benthic

M

am

mals

6

5 5

7


Coastal Marsh

7

Z

oopla

nkto

n (

incl. larv

al fish o

r in

vert

ebra

tes)

B

irds

Z

oopla

nkto

n (

incl. larv

al fish o

r in

vert

ebra

tes)

I

nvert

ebra

tes

79

M

acro

vegeta

tion

I

nfa

una

E

pifauna

B

irds

5

C

onsensus L

evel of

Concern

Score

5

7

6

Evalu

ation

Facto

rs A

dditi

onal A

dvers

e E

vent Lik

elih

ood S

core

6

6

4

9

6

9

3

5

6

9

4


33


5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5

5 5 5 5 7 7 5 5 5 5 6 6 7 7 8 5 7

5 5 5 5 7 7 5 5 5 5 6 6 6 6 7 5 6

5 5 5 5 7 7 5 5 5 5 5 5 7 7 7 5 7

8 7 7 8 8 8 7 7 7 7 8 8 9 9 9 9 9

5 5 5 5 6 6 5 5 5 5 5 5 6 6 7 5 6

8 7 7 8 8 8 7 7 7 7 8 8 9 9 9 9 9

5 5 5 5 5 5 4 4 4 4 5 4 4 4 4 4 4

6 6 6 6 7 7 6 6 6 6 7 6 7 7 7 7 7


Potential Options

F

ish

S

ea T

urt

les

S

ea T

urt

les

F

ish

5

7

Group 3 Recorder: G. Masson Leader: K. Jellison


F

ish

A

dult s

hellf

ish/o

ther

invert

ebra

tes

I

nfa

una

E

pifauna

B

irds

M

acro

vegeta

tion

Region

Habitats

B

irds

M

am

mals

A

dditio

nal A

dvers

e E

vent

Lik

elih

ood

Score

39

6

5

6 7

8 8

5

7

8

4

7

8

6

8Adverse Outcome Case


ERC: Expanded Response

5

2

5

7N/A

N/A

9

7

6N/A

4

8

6

Inte

rvention a

nd C

onta

inm

ent

Options

7

6

5

EPC: Expanded

Preparedness

5

5

IW: All Wells

IW: Potential Flow

5

Dredge/Capping

Site

Rem

edia

tion

Options


Dredge/Dispose5

5

Coastal Marsh

7

Z

oopla

nkto

n (

incl. larv

al fish o

r in

vert

ebra

tes)

B

irds

Z

oopla

nkto

n (

incl. larv

al fish o

r in

vert

ebra

tes)

I

nvert

ebra

tes

7

6

5 5

5 7

55

Benthic

M

am

mals

C

onsensus L

evel of

Concern

Score

5

6

6

Evalu

ation

Facto

rs

N/A

N/A

N/A


34



35

6.0 Recommendations and Lessons Learned 6.1 Participant Review and Discussion

The participants reviewed the results of their discussions about the ecological risks and

benefits of the alternatives from both workshop sessions and drafted a list of conclusions and

recommendations for consideration. Each focus group summary and discussion points are

presented verbatim in section 6.2.

The lists of conclusions and recommendations from each focus group were then

reviewed, discussed, and modified by all participants in a plenary session for inclusion in the

final list of consensus conclusions and recommendations for the MC-20 CERA. Those

conclusions and recommendations are listed in section 6.3.

6.2 Focus Group Discussion Points

6.2.1 Focus Group 1

The current situation poses a low2 ecological risk to known biological resources. Multiple

response options for the current situation were considered and the greatest potential for exposure

was the surface/water interface (birds, turtles, fish, and mammals). Ecological impacts associated

with both dredging options are likely to yield short-term negative impacts (increased

hydrocarbon and sediment releases) and small long-term positive impacts (reduced hydrocarbon

releases). Feasibility of both dredging options is highly questionable. Drilling intervention wells,

if successful, could yield improvements to the ecological conditions. However, the relatively

high perceived risks of adverse outcomes, either from direct impacts associated with the drilling

operations or the potential for increased flow make this option unattractive. Options to reduce or

eliminate flow through enhanced containment were felt to be of limited incremental value

compared to the current situation. A fundamental concern is the absence of a clear understanding

of the mechanisms driving the continuing releases that are being attributed to the Dome C area.

Based on the interpretation of the current conditions and assumptions regarding the

mechanisms driving the continuing releases, the following conclusions and recommendations are

posed in the following section.

6.2.1.1 Conclusions

Ecological risks/impacts under current conditions are low.

Dredging options, disposal or capping are not considered practical due to seafloor

sediment characteristics and could have unintended consequences from increased

releases and re-suspension of sediments and contaminants.

Drilling intervention wells for all remaining wells does not provide adequate

ecological improvements when considered in the context of the impacts associated

2 Low - a change in a resource condition is perceptible and localized but it does not noticeably alter the resource

function within an ecosystem.


36

with the drilling operations (seafloor disturbance, operational discharges, risk of

adverse events).

Increasing release recovery rate does not appear to substantially improve ecological

conditions.

Increasing response/containment capabilities to handle a worst case release could

provide small incremental ecological improvements but the probability of occurrence

of this event is estimated to be unlikely (±1:10,000).

6.2.1.2 Recommendations

Improved containment (an order of magnitude improvement in recovery over current

release rates) could be a sound response to the current situation; however a better

understanding of the location(s) of the point(s) of release needs to be developed to

assure proper placement of equipment, quantify the size of the accumulation, and

time period for ongoing releases.

Utilization of the site for research purposes (as a form of mitigation) should be

considered if no viable mechanism for further reducing releases can be identified.

Research programs should include fate and effects of the oil at the surface, response

technology development, use of different materials for subsea containment systems

and a better understanding of subsea conditions (sediment characteristics and

contamination profile, are there continuing inputs of oil).

6.2.2 Focus Group 2

1. Current (natural) sedimentation is the baseline scenario and is expected to provide

ecological benefit through capping of the contaminated sediments (it is what it is).

a. Increased deposition provides enhanced natural recovery without disturbance.

b. There is no apparent additional ecological risk to natural attenuation

c. The current average release (~2 gal./day) is less than the average natural seep

release size (~50 gal./day)

2. Dredge and dispose options are unacceptable because of:

a. Safety concerns

b. Unmitigated expansion of contamination footprint

3. Dredge and cap is less ecologically damaging than dredge and dispose but:

a. Uncertainty of compaction and feasibility of capping substrate (may take several

attempts/cycles) lead to questions of the ultimate success

b. Impact to the benthic communities at the dredge collection site and cap site

4. Intervention of any additional wells:

a. May cause a slight adverse negative impact because of site disturbance (drilling

mud, anchor set/pull)

b. Have a low probability of success for drilling and plugging operations

c. Will create a hazard to navigation because of shipping fairway

d. May create an unacceptable level of ecological risk

e. Will not isolate for cross-flow

5. Intervention of only potential flow wells:


37

a. May cause a slight adverse negative impact because of site disturbance (drilling

mud, anchor set/pull)

b. Have a low probability of success for drilling and plugging operations

c. Will create a hazard to navigation because of shipping fairway

d. May create an unacceptable level of ecological risk

e. Will not isolate for cross-flow

6. Expanded response capability to substantially reduce sheen using best available

technology is marginally ecologically beneficial because it helps to minimize

ecological impact to the water column and water surface. This should focus on

reducing emulsified brown oil transport into the water column and sea surface.

Technological R&D considerations:

Self-dredging of containment structures

Possibility of gas lifting process

Ability to identify active but low-flow areas (identifying location at the mud line)

Redesign hose to surface (e.g., to minimize entanglement, collapse)

7. New technology for dealing with a worst case (200 bbl/day) release

a. May be ecologically beneficial at MC-20 for situations other than intervention

well drilling

b. May be useful for other response operations elsewhere

c. May provide a mechanism for increased benzene, toluene, ethyl-benzene, and

xylenes (BTEX) exposure to the water column

d. May create a complication because of the shipping fairway if storage barges are

used (e.g., for water storage to minimize BTEX release)

e. Requires time to transport on site and deploy

6.2.2.1 Conclusions

The group concludes that current sedimentation provides a natural mechanism for

attenuation.

The ecological risk of dredge/dispose and dredge/capping outweighs any ecological

benefit.

Intervention well drilling in both scenarios (in all wells or just potential flow wells) poses

unacceptably adverse ecological outcomes. All of the wells were determined not to be pluggable

using conventional zonal isolation technology, but the well review team believes that multiple

well conduits may remain open for potential flow.

An expanded response capability would be ecologically beneficial, but this requires

additional research and development. The group suspects that there is probably a gas lift

mechanism close to equilibrium, which is causing venting bubbles to entrain oil from the

sediments into the water column and to the surface. The spatial location/s and distribution/s of

sources at the mud line are not well understood.

An expanded preparedness capability could be ecologically beneficial for MC-20,

assuming that there was a worst-case discharge of up to 200 bbl/day. This capability could be


38

used in place of intervention well drilling, but will require additional research and development.

Additionally, this technology may be useful for unrelated response operations.


Based on ecological impact considerations we recommend the following:

Allow natural sedimentation to continue.

Expand response capability of the existing containment system through additional

R&D.

Develop expanded preparedness capability to respond to a potential worst-case

discharge scenario.

6.2.3 Focus Group 3

During the Ecological Risk Workshop, the group reviewed the current conditions at

Mississippi Canyon Block 20 Taylor Energy Platform A, the available technical analysis of the

site and engaged in discussions about possible response options. The evaluations and

assessments made during this workshop are based on the assumption that there is currently no

recharge or contribution from subsea reservoirs to the contaminated sediments and the source of

surface expression of oil is from contaminated sediments.

Focus Group 3 evaluated the current conditions and response activities, referenced as

“Current Sedimentation.” The group reviewed resources at risk within the coastal marsh, benthic,

water column and water surface habitats. The group perceives the overall greatest risk is physical

contact to birds, mammals, reptiles and surface dwelling species. Other resources evaluated

within the risk matrix table were determined to have a low risk of exposure and/or low risk of

injury.

The group used a consensus evaluation of risk to each resource under Current

Sedimentation as a standard upon which the group evaluated the other proposed response

options. Considerations included the duration of impacts and the period for resource recovery.

Feasibility and cost considerations were not incorporated into our evaluations of ecological risk.

The group's evaluations of the two dredge related options were rated as more detrimental

as contrasted to Current Sedimentation. The dredge options would result in greater surface

expression of oil during execution and increase exposure to resources. In addition, the operation

itself would impact benthic organisms and slightly increase the ecological risk to some water

column species.

The ecological risk of the non-adverse outcome of well intervention options was agreed

to be very similar to the dredge options because of the nature of the operation. The intervention

of all 16 wells poses greater risk than intervening on the two potential flow wells. It is

understood that well intervention options pose risk of resulting in an adverse outcome and the

risk increases with each intervention. The adverse outcome of well intervention options

significantly increase ecological risk to all species in all habitats due to increase in volume and

unknown duration of a discharge.

The Expanded Response option is considered to be better than current sedimentation

because it would reduce the surface expression of oil.


39

The Expanded Preparedness option is considered to be a greater risk because of an

uncontrolled discharge of 200 bbl/day of oil for an undetermined period of time prior to

successful installation of containment system.

Of the options reviewed, the Expanded Response option poses the least risk to resources.

The greatest risk is associated with well intervention options because of the likelihood for an

adverse outcome.

6.2.3.1 Conclusions

Uncertainties that challenge our group include the knowledge of specific and discrete

locations, and source of ongoing oil discharge. Nonetheless, the technical data presented were

sufficient for the purposes of consideration of these options.

The group's overall perception of the ecological risk associated with the current situation

at MC-20 is that there is low risk to resources in the general vicinity of the lease block and no

risk to resources outside the immediate area under current conditions. The risk exists because oil

continues to be discharged. It is considered low risk because of low historic discharge volumes,

unlikely shoreline exposure, chemistry of oil, resiliency of exposed species, natural dispersion

and degradation.

Feasibility was discussed to help frame and understand each response option, but it did

not factor into our ecological risk assessment. The Dredge/Dispose option is considered

infeasible and Dredge/Cap is likely infeasible. The well intervention options are technically

feasible, but are undesirable because of the low probability of success and likelihood of an

adverse outcome. Of the options considered, the Current Situation, the Expanded Response and

the Expanded Preparedness options are feasible.


Given the options reviewed during the workshop, the group recommends implementing

the Expanded Response option because it poses the least ecological risk and is feasible. The

group does not recommend either of the well intervention options with the limitations of current

technology.

The list of options explored during the workshop was not exhaustive, but focused on

specific challenges of this response. The group believes that several other response options have

merit and are worth reviewing:

Agitating the contaminated sediments in order to release captured oil for mechanical

recovery and to accelerate biodegradation

Decommission in place the current containment system, continue monitoring and

respond as situation dictate

Decommission in place the current containment system, continue monitoring and

respond as situation dictate combined with Expanded Preparedness option

Additional implementations could include:

If an expanded response option is implemented, it would be beneficial to include an

Acoustic Doppler Current Profiler and weather buoy in the design


40

Utilize the site for scientific research and training

In reflection of the technical information presented, current situation on site, current

knowledge gaps, conversations among attendees and deliberations during the Ecological Risk

Assessment, the group recommends:

Analyze historical sheen data to revise the frequency and procedures of over-flight

operations

Flights could be triggered by specific operations which disturb bottom sediments,

remote sensing data or other reporting sources

Conduct additional over-flight when surface expression is calculated above 40 gal.

Deploy on-water recovery system when on-water recovery of oil is practicable

6.3 Consensus Recommendations of the Workshop

During the final day of the MC-20 CERA workshop, the participants convened in a

plenary session and combined their individual focus group findings into consensus conclusions

and recommendations. Their findings are presented below, as drafted by the participants.

6.3.1 Dredging Options

Dredging options, disposal or capping are not considered practical due to seafloor

sediment characteristics and could have unintended adverse consequences from increased

releases and resuspension of sediments and contaminants. The ecological risk of dredge/dispose

and dredge/capping outweighs ecological benefits.

6.3.2 Well Intervention

Drilling intervention wells for all remaining wells or just potential flow wells does not

provide sufficient ecological benefits when considered in the context of the risks and impacts

associated with the drilling and plugging operations (probability of success, seafloor disturbance,

operational discharges, risk of adverse outcome)3.

The participants understand that in the absence of drilling intervention wells there

remains a risk for a worst case discharge.

6.3.3 Existing Ecological Risk

Our overall perception of the ecological risk associated with the current situation at MC-

20 is that there is low4 risk to resources in the general vicinity of the lease block and no exposure

risk to resources outside the local area.

3 The UC determined that none of the wells could be plugged by conventional zonal isolation technology.

Additionally, the well review team concluded that multiple conduits may remain open for potential flow. 4 Editor’s Note – The term “low” used in this context was never explicitly defined by the participants during the

plenary session discussion. Individual Focus Groups did offer some clarification (see p. 39 and p. 43) in their

discussions. In the initial ranking of the “status quo” or baseline condition, participants concluded that the use of the


41

6.3.4 Expanded Response Capability

An expanded response capability5 would be ecologically beneficial but not measurable.

This option would require additional research and development.

6.3.5 Contingency Preparedness Capability

A contingency preparedness capability6 could be ecologically beneficial for MC-20 in the

event of a worst case discharge of up to 200 bbl/day. This capability could be used in place of

intervention well drilling, but will require additional research and development. Additionally,

this technology may be useful for unrelated response operations.

6.3.6 Other Conclusions

The group concludes that current sedimentation provides a natural mechanism for

attenuation.

6.3.7 Recommendations

Based on the current situation, we recommend:

Expanded response capability could be a sound option.

Utilization of the site for research and training purposes should be considered.

Develop contingency preparedness capability to respond to a potential worst-case

discharge scenario.

For the USCG, the group recommends that:

Additional factors (e.g., wind speed, direction, sea state, % of dark/recoverable oil)

be considered in a decision matrix to determine threshold for response operations.

Analyze historical sheen data to evaluate the frequency and procedures of over-flight

operations. Flights could be triggered by specific operations which disturb bottom

sediments, remote sensing data or other reporting sources. Conduct additional over-

flights when surface expression is calculated above 40 gal.

Do not pursue additional well intervention because the ecological risks outweigh the

possible benefits.

Do not pursue dredge/dispose or dredge/cap options because the ecological risks

outweigh the possible benefits.

proposed Ecological Risk Ranking Matrix would produce the lowest possible risk ranking due to low percentages of

environmental resources being affected, and estimated recovery periods for each oiling event of less than one month. 5 An expanded response capability is defined as reducing the current sheen by using best available technology to

enhance the containment solution. 6 A contingency preparedness capability is defined as planning, developing, and having ready for deployment a

containment solution for the worst case discharge (approximately 200 bbl/day).


42



43

7.0 References

Aurand, D., L. Walko and R. Pond. 2000. Developing Consensus Ecological Risk Assessments:

Environmental Protection in Oil Spill Response Planning. A Guidebook. United States

Coast Guard, Washington, DC. 148 pages. (Also Ecosystem Management & Associates,

Inc. Technical Report 00-01).

Camilli, R. 2008. Mississippi Canyon 20 Plume and Soil Contamination Survey Project Using

the TETHYS Mass Spectrometer. Come Monday Report.

Fugro-McClelland Marine Geosciences. 2005. Assessment of Seafloor Movements MC20-A

Platform Block 20, Mississippi Canyon Area Gulf of Mexico. Number 0201-5381-1

Fugro-McClelland Marine Geosciences. 2006. Seafloor Failure Analyses MC20-A Platform

Block 20, Mississippi Canyon Area Gulf of Mexico. Report No. 0201-5381-7.

Taylor Energy Company. 2013. Report of Environmental Conditions and Actions Taken to

assess and Minimize Environmental Impact. Mississippi Canyon 20 Gulf of Mexico.

Taylor Energy Company, New Orleans, LA. 25 pages.

U.S. Coast Guard. 2008. USCG Administrative Order 006-08 Taylor Energy Company

Mississippi Canyon Block 20 (MC 20) Platform “A”. September 23, 2008.

U.S. Coast Guard. 2012. Incident Action Plan MC 20 Platform Toppling Taylor Energy

Company LLC.

U.S. Environmental Protection Agency. 1998. Guidelines for Ecological Risk Assessment.

Federal Register 63 (93) of Thursday, May 14, 1998. pp. 26846-26924.


44



45

Appendix A: Participants

First Name Last Name Organization 13-May 14-May 15-May 26-Jun 27-Jun 28-Jun Focus Group

Jerry Alexander Independent Consultant for Taylor Energy X X X X X Technical Resource

Mario Arteaga Plaqumines Parish Government X 1

Don Aurand HDR|EM&A X X X X X X Facilitator

Kyle Baker National Oceanic and Atmospheric Administration X X X X X X 1

Paul Barbre Bureau of Safety and Environmental Enforcement X X X X X X 2

Mike Beatty Beatty & Wozniak (on behalf of Taylor Energy) X X X Technical Resource

Sam Bentley Louisiana State University (on behalf of BSEE) X X 2

Roberto Bernier United States Environmental Protection Agency, Region 6 X X X X X X 3

Dina Bracci Taylor Energy X X X X X X Technical Resource

Darice Breeding Bureau of Ocean Energy Management X X X 2

T.J. Broussard Bureau of Safety and Environmental Enforcement X Presenter

Wade Bryant United States Geological Survey X X X X X X 3

John Calvin Bureau of Safety and Environmental Enforcement X X X 3

Rich Camilli Navistry Inc. (on behalf ofTaylor Energy) X X X X X X 2

Lynard Carter Bureau of Safety and Environmental Enforcement X Presenter

Mike Celata Bureau of Ocean Energy Management X Observer

Jeff Dauzat Louisiana Department of Environmental Quality X X X X X X 2

Norman Duplanits Independent Consultant for Taylor Energy X X X X X X Technical Resource

Denise Fields Taylor Energy X X X X X X Technical Resource

Sean Fitzgerald United States Coast Guard X X X X X X 2

Barry Forsythe United States Fish and Wildlife Service X X X X X X 1

Barret Fortier United States Fish and Wildlife Service X X X X X X 2

Peter Gautier United States Coast Guard X X X X X X Presenter

PJ Hahn Plaquemines Parish Government X 1

Lushan Hannah United States Coast Guard X X X X X X 3

Charlie Henry National Oceanic and Atmospheric Administration X X X X X 1

Chuck Holman Bureau of Safety and Environmental Enforcement X X X X X X 3

Kyle Jellison National Oceanic and Atmospheric Administration X X X X X X 3

James Madere Plaquemines Parish Government X 1

Greg Masson United States Fish and Wildlife Service X X X X X X 3

Tom Meyer Bureau of Safety and Environmental Enforcement X X X X X X 3

Jeffrey Meyers Louisiana Oil Spill Coordinator's Office X X X X X X 1

Michael Miner Bureau of Ocean Energy Management X Observer

Keith Nichols C-K and Associates (on behalf of Taylor Energy) X X X X X X Technical Resource

Ed Overton Louisiana State University (on behalf of NOAA) X X X X X X 2

Mike Parker Offshore Operators Committee X X X X X 1

Will Pecue Taylor Energy X X X X X X 3

Gary Petrae Bureau of Safety and Environmental Enforcement X X X X X 3

Mike Prendergast Bureau of Safety and Environmental Enforcement X X X X X X 2

Chris Reddy Navistry Inc. (on behalf ofTaylor Energy) X X X X X X 1

Leah Robinson HDR | EM&A X X X X X X Notetaker

Mike Sams United States Coast Guard X X X X X X 2

Jason Screws United States Coast Guard X X X X X X 1

Don Shackelford Boots & Coots (on behalf of Taylor Energy) X X X X X X Technical Resource

Bill Shedd Bureau of Ocean Energy Management X X X X 1

Peter Smith Waldamar Nelson (on behalf of Taylor Energy) X X X X X X Technical Resource

Stephen Spencer United States Department of the Interior X X X X X X 1

Jim Staves HDR|EM&A X X X X X X Facilitator

Bret Sumner Beatty & Wozniak (on behalf of Taylor Energy) X X X Technical Resource

David Trocquet Bureau of Safety and Environmental Enforcement X Presenter

Brian Wynne Louisiana Oil Spill Coordinator's Office X 1

Kehui Xu Louisiana State University X Observer

Damian Yemma United States Coast Guard X Observer

Workshop 1 Workshop 2


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Appendix B: MC-20A Reference Materials and Contents


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Additional references not found in the report, but provided to workshop participants include:

Falcini, F., N. S. Khan, L. Macelloni, B. P. Horton, C. B. Lutken, K. L. McKee, R. Santoleri, S.

Colella, C. Li, G. Volpe, M. D’Emidio, A. Salusti and D. J. Jerolmack. 2012. Linking the

historic 2011 Mississippi River flood to coastal wetland sedimentation. Nature

Geoscience. DOI: 10.1038/NGEO1615.

Wang, K. and E. E. Davis. 1996. Theory for the propagation of tidally induced pore pressure

variations in layered subseafloor formations. Journal of Geophysical Research 101(B5):

11,483-11,495.

ecological risk assessment: consensus workshop - mc-20 ......era consensus workshop - mc-20a...

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