Ecological Risk Assessment: Consensus Workshop · 2019-02-05 · Sheen Abatement foi• the...

Ecological Risk Assessment: Consensus Workshop

An Examination of the Potenti~i Ecological Impacts of Response Alternatives Being Considered

for Sheen Abatement for the Remnants of the Taylor Energy Company, LLC

MC-20A Platform -Gulf ofi Mexico

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EIZA Consensus 1~orkshop - MC-20A Platform - Garlf ofNlexico


ERA Consensus Workshop - MG20A Platform -Gulf of Mexico


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


MC-20A Platform --Gulf of Mexico

A Report to Taylor Energy Company, LLC

James Staves, Leah Robinson, Don Aurand (Compilers) HDR ~ Ecosystem Management

Ecosystem Management .. &Associates


ERA Con.sensi.~s W'orksl~op - N/C-20A Platform -Gulf of A~eazco

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 foi• the Remnants of the Taylor• Energy Company, LLC MG20A Platform —Gulf of Mexico. A report to Taylor Energy Company, LLC. HDR ~ Ecosystem Management, Lusby, MD. 20657. 50 pages.

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ERA Consensus YVoy~kshop - ~l~IG20A Platform -Gulf of Mexico

TABLE OF CONTENTS

.:

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

1.0 Objectives of the MC-20A CERA Worl<shop .......................................................................5 1.1 Unified Command Objectives ........................................................................................5 1.2 The ~pp(ication of the Consensus Ecological Risk Assessment Process ......................5 1 .3 Patticipants .....................................................................................................................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 Backgrnun~) inf~rmati~n .......................................................................................................13 3.1 The MG20A I'latforin Accident —September 2004 ...................................................13 3.2 Initial Environmental Investigations ............................................................................1G 3.3 Response Activities to Date .........................................................................................17 3.4 Recent Environmental Investigations ..........................................................................19

3.4.1 Creation of Well Review and Sheen Source Worlc 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 NOAH 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 Pebrtiary 2013 Sampling Program Results ......................................................21

4.0 Clements of the CF.,RA P~•ocess .............................................................................................23 4.1 Geographic Area of Conce~•n .......................................................................................23 4.2 Resources of Concer•n ..................................................................................................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 aild 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


ERA Consensus b~ior•kshop - ~17G20A Platform - Gulf ~f A4exico

6.2 rocus Group Discussion Points ...................................................................................35 6.2.1 Focus Group l ..................................................................................................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 6.2.2.2 Recoinmendations ...............................................................................38

6.2.3 Focus Group 3 ..................................................................................................38 6.2.3.1 Conclusions .........................................................................................38 6.2.3.2 Recommendations ...............................................................................39

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 h.3.7 R~rnmmendations ............................................................................................41

7.0 Refet~ences ................ .43

Appendix A: Par-ticipants ..............................................................................................................45

Appendix B: MG20A Reference Materials and Contents ...........................................................47

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ERA Consensus Workshop - MG20A Platform - Gzr[f of Mexico

LIST OF FIGURES

Figure Description Page

3.1 Gene►•al Location Map of MC-20 .........................................................................................13 3.2 Site Location and Regional Seatloor Bathymetiy Map .......................................................14 3.3 Original Position vs. Post-Failure Position Following Hurricane lvan ...............................15 3.4 Profile View of Buried MC-20A Well Conductoc ................................................................16 4.1 Ecolobical Risl< Ranking Matrix ...........................................................................................26

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FRA Consensus )dinrkshop -ABC-20A Plalfa~m - Gz~lf gTAlesico

This Page Intentionally Left Blank

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F,RA CoJ~sensars I~orkshop - MC-20A Platform -Gulf of Mexico

LIST OF TABLES

Table Description

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

4.1 MC-20 Resources at Ris]< ....................................................................................................24

4.2 TEC Ranki►~g Sheet (Conceptual Model Matrix) used for the Baseline Analysis ................25

4.3 Modred Risl< Ranking Scale ..............................................................................................27

5.1 Modified Risl< Ranking Scale ..............................................................................................30

5.2 Detailed Risl< Analysis Results -Group 1 ............................................................................31

5.3 Detailed Risl< Analysis Results -Group 2 ...........................................................................32

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

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ERA Consensr~s ld~or•kslao~ - ~I~C-20A Platform - Gulf of ~I~lexico


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ERA Consensus Id~orlcshop - MG20A Pla form - Gulf of Mexico

LIST OF ABBREVIATIONS AND ACRONYMS

Bbl Bai-r•els BML Below Mud Lii1e BOEM 13ueeau of Ocean Ene~~gy Managemetlt BSCF, Bureau of Safety and Environmental Enforcement BTEX Benzene, toluene, ethyl-benzene, and xylene CERA ConsensusEcological 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 ~(~M Gulf of Mexico HDR HDR ~ Ecosystem Management IAP Incident Action t'lan 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 (foc 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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ER~I Consensus I~Vo~rkshop - MG20A Platform - Gz~lf of Mexico



ERA Consensus Iliorkshop - MG20A Platform -Gulf of Mexico


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


MC-20A Platform -Gulf of Mexico

Executive Summary

Taylor Energy Company, LLC's (TEC) MG20A 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 (ML-ZU). At the time of the design and ir~slallaliur~ oC tll~ 1~1C-ZOA 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 MG20. Ivan alternated between a Category 4 and Category 5 storm as it traveled northward towards the coast, with maximtun 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 ash and wildlife.

Based on the observation that the current response actions were reaching a point of diminishing returns, the UC decided to convene abroadly-based group of stakeholders with applicable expertise, and conduct a Consensus Ecological Rislc Assessment (CERA) to evaluate the potential ecological impacts of available response options. HDR Ecosystem (Management (HDR) was contt-acted by TEC to facilitate the CERA.

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I:RA Consensus Workshop - MC-201 Platfa•n~i - Gulf'gf A~Jexico

T11e 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 MG20 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 witho~it potential adverse outcomes; • Intervention on cen~aining wells with flow potential —with and without adverse

outcomes; • Expa►Zded i-es~onse capability to reduce the current sheen by 75% using best available

technology; and • Expanded pl•eparedness capability by developing a containi7ier►l sulutiui~ for the worst

c;a5~ 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 (NOAA~) 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, 201.3. Works}1op 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 Rislc 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 t•isks, 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 for►ns and scales t11at 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 utilising the "recovery trine" 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

' 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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ER~1 Co~~sensz~s Workshop - MC-20A Platform -Gulf of Mexico

these reasons, the proposed ~•anlcing matrix was not used for the remaining six options, and was replaced with a simple, one dimensional scale of 1 to 9, where larger ~luinbers 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 fot• selection.

The baseline condition (natural sedimentation) was assigned a value of 5 (using the modified scale), so that alternatives could be i•anl<ed 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 curient 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 MG20 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 wcrc 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 intei-ventio~~ wells was not expected to provide sufficient ecological benefit to offset the risks and impacts associated with drilling and plugging operations, even thoubh 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 i►~ the event of a worst case discharge (up to 200 bbl/day), but additional research and development would lie required. Based o~~ those conclusions, the workshop participants developed a list of consensus recommendations, acceptable to all participants. The i-ecoi~nmendations 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 opeeations 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.


ERA Consensus Workshop - R4G20A Platforr~~ - Gulf of Alexico



ERA Consensus YVorkshop - N(C-ZOA Platform - Ga~[f of Mexico

1.0 Objectives of fihe 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 il~itigation strategies arr~1 ~levclup a technologically feasible and en~~ironmentall~~ defensible path forward. That approach ~~~as b?liPvecl t~ offer the best hope of minimizing adverse environmental consequences to the ecosystem as a whole, based largely ot~ 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. Otllei- 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 aconsensus-building approach to evaluate risks and benefits.

The USCG sponsored the development of a guidebook on this process: Developing Consensus Ecological Risk Assessments: Envrronn~ental P~~otecCion in Oil Spill Response Planning. A Guidebook (Aurand et al., 2000). The process is designed to 11e1p 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-resoui•ce co~~nparisons. Through a structL~i•ed 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


ERA Consensus Workshop - MC-20A Pla form - Gzrlf of Mexico

an active spill event. However, knowledge gained by participants in the consensus-building process facilitates real dine 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 diffetetlt response, ~•emediation, and initigatioi~ 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 iii 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-~overninental 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 researc}1 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 pt•ocess 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 foi-~nulation 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


ER~I Co~~sensa~s id~orkshop - MC-20A Platform - Gulf of Mexico

assigned to a focus group and actively participated in all phases of the CCRA. Each of the Participants represented an agency o~• organization that had jurisdiction, and/or expertise that was relevant to the CERA. Technical Resou~•ces 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 t11e 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 fi les on a Compact Disc (CD) prepared as a project deliverable product. Tire r~eEw~l ~1~111111dt'IZCS the results of the workshops, and prese.nt~ the conclusions and recommendations of the participants. It is formatted to be printed as an independent, double-sided report. I~1 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 fi les are cited at appropriate locations in the text of the report.

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ERA Consensus Wof-kshop - MG20A Plcztfof•m -Gulf of Mexico



GRA Co~~sensus Workshop - MC-20A Platform -Gulf of Mexico

2.0 Overview of Workshop Events

Following the UC decision to perform a CERA, as detailed in secCion L1, a Steering Committee composed of representatives from t11e USCG, TEC, BSEE and NOAA was established to tailor t1~e CCRA process to the unique circumstances presented by the TEC scenario, plan the workshops, and recommend tl~e 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 ~eti~n~ 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 partieipanls as refcrcuc~ materials on site (see Appendix B).

The first workshop began with welcoming remarks from Captaic~ Peter Gautier (USCG FOSC). Dr•. Don Atu~and (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: "GeoTecl~nical 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 Or anization Recorder Or anization 1 Jason Screws USCG Mike Parker Offshore O erators Committee 2 Jeff Dauzat LA DEQ Sean Fitz erald USCG 3 K le Jellison NOAH Gre Masson USFWS

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ERA Consensus Workshop - A~G20A Platform -Gulf of'A7exico

Mr. Will Pecue described actions taken by TEC, which included the eve phases of well-decommissioning, the subsea containment system, and the establishment of the UC technical workgroups (on the CD as: "Five Stages of MG20 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 Slleen Source (on the CD as: "Sheen Source Technical Workgroup Results") and Well Review (on the CD as: "Overview of MG20 Well Review Processes") Technical Worlcgroups, respectively. Day 1 concluded with a t-eview of the state of hydrocarbon contamination and releases at MG20 by Dr. Chris Reddy (Navistry, Inc.) (on the CD as: "July 2012 Coring Acquisition and Foeensic Atlalysis" & "February 2013 Dome Coring and. Results of Containment Reactivation"), and Mc 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 Prescntation").

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 sessio►~ resulted in a decision to make some modifications to the risk assessment matrices including:

• Replacing "Salt Mat-sh" with "Coastal Marsh"; • Adding birds to intertidal salt marsh sections; • Adding zooplatzkton to water surface sections; • Changiizg recovery rate categories in tl~e Ecological Risk Ranking Matrix; • Adding a column for "safety" in the t~isk summary sheet; and • Rei~loving "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 tl~e 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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C~R.4 Consensus I~i~orkrhop - NlG20A Platform -Gulf of Mexico

Day 3 of the fi rst 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 lead not yet been evaluated by the focus groups. Based on concerns raised by soiree 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 woi•]cshop began with a review of the accomplishments of the first workshop. NOAH trajectory model analyses for focus group consideration were provided (on the CD as: "NOAH 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 l and scored the remaining options. Focus groups presented their scores for all options in a plenary session for- further discussion.

Day 2 ~f ll~e 5e~~u~l tivurkshop began with a revie«~ of technical and engineering feasibilit}~ studies for all n~,tinn~. The focus ~;i•oups 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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ERA Consensus I~orkslzop - A~G20A Platform - Gr~lf of Mexico


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ER4 Consensus I~Vorkshop - MC-20A Platform - Gulf of Mexico

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).

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The water depth at the site was about 480 ft. in 1984. The MG20A 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 ti~~~e of the design and installation of the MG20A 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 MG20. Ivan alternated between Category 4 and Category 5 classifications as it traveled northwards towards the coast, with maximum wave 1leights near l00 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.

13


ERA Consensus YVorkshop -ABC-20A Platform - Ga~lf of Mexico

Fib u~•e 3.2 Site Location anc~ Re~Tional Seafloor Bathymetry Map (FMMU, 2006)

The platform was toppled by a regional slope failure, or unprecedented large-scale mudslide, during Ivan and now lies about S50 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 tow 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 t11at is part of a regional seafloor failure described in Fugro-McClelland Marine Geoscienees (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 MG20 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

14


F,~IZA Co~aser~sirs ld~orl~shop - MC-20A Platform -Gulf of Mexico

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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 t11e 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 seefloor). The 28 eonductoi-s were located on the MG20A platform in a 4x7 row grid, with 7-1/2 foot center spacing between each conductor. Fie(d 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.


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

The prole 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).

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Figure 3.4 Profa'lE 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. Geotechilical 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.) i~1 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:

16


ERA Co~~sensus YVorkshop - MC-20A Platform - Gulf of Mexico

• 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 saivpling 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 co~~duct Phase III studies, which determined the degree of hydrocarbon exposure through water and sedi~nei~t sampling. The Phase III study identified three discrete pl~nnes, 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 signat~~~•e was found neat• the platform's original wellhead (well bay) area.

2. Hydrocarbon ion pealc intensity, temperature and salinity data collected during the Phase I survey suggested air active hydrocarbon leal< in this well bay area. Specifically, the highest hyd~•ocarbon intensities were collocated with bathymetric, tei»peraturc, and salinity anomalies, suggesting that nil, nat.iaral gas, acid produced water were actively venting from discrete locations iii 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 dist~•ibutioils by the mass spectrometer.

4. Hydt~ocarbon 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. T}1e very loose sediments at MG20 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

17


ERA Consensus Wor~ksho~ - MG20A Platfo~•n~ - Gz~/f of tVlexico

intervention wells to allow for plugging of those MG20A 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 2071 and the fourth phase of subsea debris collection concluded in July 201 1. The potential fifth phase (Site Reinediation) is a subject for the CERA process.

In fhe summer of 2008, prior to the commencement of the first intervention well, the USCG issLied an Administrative Order (USCG, 2008) to TIC requiring the following actions: (1) immediately deploy an open water skimming asset to mitigate the continuous discharge at MC-20A until such tune that pollution domes are installed; (2) conduct over-flights twice daily to monitor the discharge from MG20A and provide the USCG with reports from these over-flights; (3) install pollution domes to mitigate the continuous discharge in MG20A no later than November 1, 2008; and (4) provide an updated Incident Action Plan (IAP) reflecting all requirements of the administrative order.

By the tune the Subsea Containment System was built and ready for deployment, the first intervention well operation involving the plugging of MG20 well A-21 had successfully eliminated Plume B, one of tl~e two oil plumes i~1 the former well bay area where the platform lead originally been located. As a result, the installation sequence allowed Dome A to be installed over the remaining oil rlume (A) in the well bay area, and Dome C to be installed over the observed gas Plume C neai the toppled jacket. While installing Doine C, a small gas emission was observed from the mud line approximately 2U fit. ti~o~n llome C. TEC elected to install ll►c

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/eli~~nination of the remaining MG20A plumes identified in the Cone 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 MG20A discharge site, and submit a written plan that shows a projected timeline for fabrication and installation to the UC too 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 fi•om the MG20A discharge site and develop a sampling plan for obtaining


FRA Coi~sensr~s PVorkshop - MG20A Platfor~na - Ctrlf of Mexico

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 i~~ the study area.

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

In eat•ly 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 1 b wells. The se~ui►~l

work group was instrucle~l lu e]Clcri7~ine the source of the ongoing surface sheen at I~~C-2~J.

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 consec~uenee 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. Tn 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 Worl< 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?

19


ERA C~onserrsus I~~o~•kshop - MG20A Pla form - Gulf of Mexico

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 X11 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 ~•elatively 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 t11e 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 MG20 and perform an acoustic survey there as well. After correcting the original acoustic dataset for recording issues, the sonar dataset found an acoustical feature uri~;i~iating at the Subsca Collector/Separator (most likely inc~irating vent line discharges of has; ~~~he.i-e c.nllPcted has 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 theee was doubt whether the continuing sheen (post commissioning and containment system installation) was due to release fi•om a leaking well that had not been plugged (primary source) or a release from sediments containing oil (secondary source). Accordingly tl~e first new site investigation (in .Iuly 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 inid-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 (.tune 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 i~lterpretation were discussed and reviewed beforehand with the Sheen Source Worlcgroup 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.

20


f.:RA Consensus 1~Vorkshop - MC-20A P(atfvrrn -Gulf of Mexico

The highest concentration of petroleu►n 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 tleai• surface sediments appeared to be less t11an 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 distui°bance 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 t11e sediments. Soth tl~e USCG Marine Safety Laboratory and Alpha Laboratory (used by TEC) conclusions indicate that there was a match between sheen oil and samples of containme~~t 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 MG21 platfori~n in an attempt to het a surrogate match fir MG20 reservoir oils that were no longer avail~hle 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"). T11e results were presented on Day 1 of the first workshop by Dr. Chris Reddy.

In February of 2013, afollow-up sampling program was cammenced 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 MG20 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 done.

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

21


FRA Consensus i~a~ks/aop - MG20A Platform - Gz~If~ofMexico

and sheen samples share a common source. The Coast Guatd's Ma~•ine 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 setlt to Isotech Laboratories for apoint-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.

22


ERA Consensus Workshop - MG20~1 Platform -Gulf of Mexico

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 CCRA 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. Tl~e 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. I.n the case ~f llie N1G20A C~RA, 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 MG20, and then migrate to a nesting area), so athree-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 MG20 (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 concer»." When thefocus 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 at•ea 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.

23


ERA Consensz.+s YVor•%shop - MC-20.~ Platfo~~in - Gulf ofA7exico

Table 4.1 MG20 Resources at Risl<

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 Fiah 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 smotllecing, thermal, oil conta►ninated waste materials, and indirect (i.e., ingestion of contaminated food). For the MC-20 CERA, the participants concluded that none of the eesponse options evaluated significantly increased the magnitude of any of those hazards, and elected to utilize a sii~~ple, single dimension risk scale that aggregated hazards from all sources. This allowed assignment v{' a single risk score for each of the resources at concern for each of the t11►•ee focus groups. The form used to record those scores is shown in Table 4.2.


F.RA Consensus Workshop - MC-20A Platform - Gulf of Mexico

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

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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 sti•essors 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 i►~npacts, 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.

25


E£~~ Consensa~s Workshop - MC-20A Platform - G~rlf c~f~A~exico

RECOVERY

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

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T,egend: Da~•k Iced cells represent a "high" level of concern, bright red cells represent a moderately high level of calcern, orange cells represent a "moderate" level of coi~cei7~, yellow cells represent a moderately low level of concern, end green oellc ropreeent a lows lf~`~~l c,f cnnnFrn

Figure 4.1 Ecological Risk Ranking Matrix

Using this matrix, a score of lA 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 ~~~atrix. 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 t11e 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. Foc 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

►..


F_RA Consensars YVorkshop - MG20A Platform - Culf of Mexico

below current conditions. When using this approach, focus groups still considered geographic and population impacts, but did riot use the oz-iginal 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 Qocument 7 6

Baseline 5 4 3 2 Document

Best 1 bocument

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. Cach 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

27


ERA Consensus I~Vorksho~ - AJC-20A Pla{form - Gz~lf of n~lexrco

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 takers 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, wl~icli was agreed to by the Steering Committee. It ~~as also recoi~~me.nc~ecl that n~ti~n 4 h~ split into iwn n~ti~ns add~~essin~; 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).

28


FIZA Consensus Workshop - MG20A Platform - Gulf of Mexico

5.0 The Results of the CERA

5.1 Results of fihe First Workshop

The prelimi»ary conclusions reached during the f fi rst workshop are included below.

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

localized with an overall low level of cislc. 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 tl~e df•illing activity. 3. Dr~ec~};i1r~ ~ptious ~cvlogical i°isk~ outweighs potential wins.

C:• 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 I~owever 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 wor]<shop. 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 I to 9. That rating is contrasted to those for the additional options in Tables 5.2 throug115.4.

29


ERA Consensa~s Workshop - NIC-20A Platfo~î~~ - Gz~lf of A~le.xico

Table 5.1 Modified Risk Ranking Scale

Current Sedimentation Status Quo

Region Intertidal Open Marine Environment c O y

Habitats Coastal Marsh Benthic Water Column Water Surface ~a m

N 41

> W

~

N l6

N N

.Q

~ N

d

~ N ~

~

~

C

O

C

O

O

~ C

L

N Y ,`p ~ L

~ L tq ~ J

PotenGalOptions ' ' Z v w ~ `m ~ —

o

d

O '~

~

~ C C >

N

N

~

N

N N

N ~

C y

u

C J

N

'~O Q

~ ~ l6 ~ L C (0 ~ C N C

o °' c ~ E ~ ~ '~ E ~ ~ a~i .o

~ ~ i~ m ~ w m ~ <n u ¢ ~ m ~ in ii g U Q

R R R R R R R L L L L L L L L L L Group1 4C 4D 4D 4D QD 3D- 3Q 4D ,4D 4Q 4D 4D' 4D 3D° 4C `4C 4p 4C

a R R R R L L WA R R R R R R R R R R ` ~tD ; 4D 4D GD 1 D 4D` 4D 4D 4D 4D 3D 2D 4D 4D 4D 3D- o Group 2

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 4p Group3

5.3 Evaluation of Potential Response Options

Each of the focus groups evaluated all rei~naining 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.

30


F.,R,4 Conserrst,~s T~orkshop - MC-20A Platform -Gulf of Mexico

Table 5.2 Detailed Risk Analysis Results -Group 1

Grou 1 Recorder: M Parker Leader: J. Screws

Region Intertidal Open Marine Environment c o

Habitats Coastal Marsh Benthic Water Column Water Surface u,

~ m m > ~ w

~ m

~ m

a r ~

a r ~ d

~ c c o 0

~ O O ~ G N

~ w w. ~ U

Potential Options j ~ a~

N m —

c0

@ _

O

V a ..

.c C

U ~ W ~

(O N

~

N V

C

C

~

J v ~

N

~

@ ftl 'Yt

V/

.0

M=

L

p

"i[ N

~

L'

p C

3 N

>

.i

~ ~

~ N

~p ~ ~ 7

~

to ~

N

~

E

~

L

~p

fl'

~7

C

m

~d ~ ~s ~ ~ a ~ ~ ~ ~ ~ 8 ~ ~ w ~ ° o ~ ~ li 0] ~ W m ~ fn I.L Q N Cl1 ~ (n ti N U Q

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5Current Sedimentation

5 5 5 5

0 5 5 5 5 6 6 4 4 4 4 4 4 2 3 3 4 3 4~~ Dredge/Dispose -long term 5 6 4 3

~ 0 term

5 6 5 6 8 8 6 5 5 6 7 6 7 6 6 5 5 ~ 6 g 6 6 ~ a Dredge/Dispose -short

o5 5 5 5 3 3 4 4 4 4 4 4 2 3 3 4 3 4

~' Dredge/Capping - long term 5 3 4 3

5 5 5 5 7 7 5 5 5 5 5 5 5 5 5 5 5 6Dredge/Gapping -short term 5 ~ 5 5

5 5 5 5 5 5 4 4 4 4 4 4 2 3 3 4 3 4IW: All Wells

5 5 4 3

~ 8 7 7 8 6 6 6 6 6 6 7 7 8 7 8 6 8 8 4@ C <; $ 6 g g c 0 5 5 5 5 5 5 4 4 4 4 4 4 2 3 3 4 3 4 ~ o IW: Potential Flow 5 5 4 3

m a g 7 7 8 6 6 6 6 6 6 7 7 8 7 8 __ 6 8 g 3

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

~ 75% Sheen Reduction 5 5 5 5

~ 6 5 5 6 5 5 5 5 5 5 5 5 6 6 6 5 6 6 2 NOIW: New Containment 6 5 5 6

31


ERA Consensus Workshop - MG20A Platform -Gulf of A7exico

Table 5.3 Detailed Risk Analysis Results -Group 2

Grou 2 Recorder: S. Fitz erald Leader: J. Dauzat

Region Intertidal Open Marine Environment c

Habitats Coastal Marsh Benthic Water Column Water Surface o ,n ~ m m > ~

N N wN N

N N ~ .~

r C N N ~

p ~ 0

N ~

~ ~ V

U ~

~ o o <n a 8

'C ,,N-. w U N

Potential Options N

~ > Z C

U Y

~' ~ L

m m p > W

p '~ N

~ ~

C ~..

C :~

> J

~ N

N m

~ (0 N

N ~

— ~

O y N

N~

O ~

N N

v Q

O ~ ~ C ~ rn

E ~ ~y

~ l6 p_ vi

~ ~ ~(Q

(6 Qp

N O~

C ~

~c C I..L 07 C W C~ ~ (n IL Q N m ~

5

(h

5

I.L N U Q

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5o y

Current Sedimentation 5 5 5 5

a; `° 0 ~ Dredge/Dispose

7 7 7 7 9 9 N/A 6 7 8 7 7 7 7 8 7 7 ~ ~ 9 ~ ~ o

~ ~ Dredge/Capping

6 6 6 6 7 7 WA 6 6 6 6 6 6 6 7 6 6 66 ~ 6 6

6 6 6 6 7 7 N/A 6 6 6 6 6 6 6 7 6 6 6IW: All Welis

6 7 6 6

~ 9 9 9 9 8 8 WA 8 8 8 8 B 9 ~ 9 9 9 g 9 5

9 ~ g 9 roc

crre ~,.sra

~ IW: Potential Flow 6 6 6 6 6 6 WA 6 6 6 6 6 6 6 7 6 6 66 6 6 6 o

m a ~ <;~ ~ rsa3 G~~tt;c~r}~= ` u.,~

9 9 9 9 8 8 N/A 8 8 8 8 8 9 9 9 9- 9 ~ 49 8 8 8 o

~ 5 5 5 5 5 5 N/A 4 4 4 4 4 4 4 4 4 4 45 5 4 4 > ERC: Expanded Response

EPC: E~anded 6 6 6 6 6 6 N/A 6 6 7 7 7 6 6 6 6 6 6 3 6 6 7 6 Pre tiredness

32


FR,4 Consensus 1~Vorkshop - MG20A Platform -Gulf of Mexico

Table 5.4 Detailed Rislc Analysis Results -Group 3

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

Region Interfidal Open Marine Environment c o

Habitats Coastal Marsh Benthic Water Column Water Surface v,

~ m m > ~ w

à~i m

a~i ~

~ ~ r ~ ~

~ C G 0

~

L

N `p p C

N Y

41 'C

N y-

N 4-

N U J

Potential Options > S

N ~

N @

O v

N w ~ _ _ o ~

~ OL C `~ J '6 !p N

N N ~

N C p

~~/~{

N

~

C O Y

N Q

m ~

~ ~

N

~

N Y

~ ~

r=/~ ~

O ~ ~

~ m

M

~

C ~

~

J (0

~q,

N

-°

E

~

f[Q

N

~

~

~ QO

p

y

.o

C

m

~—

~ Lcn

p.

$

~ f/

o

~+

~ ~ ~ LL m W m ~ ~yjVJ LL ~l N W C V, lL ~., v S 3

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 N/A o Current Sedimentation 5 5 5

a; ~6 p 'g,

5 5 5 5 7 7 5 5 5 5 6 6 7 7 $ 5 ~ 6 N/A 5 ~ 5 7 ~ Dredge/Dispose

~ 5 5 5 5 7 7 5 5 5 5 6 6 6 6 7 5 6 6 WA Dredge/Capping 5 ~ 5 6

5 5 5 5 7 7 5 5 5 5 5 5 7 7 7 5 ~ 6 N/A IW: Ali Wells 5 7 5 7

~ 8 7 7 8 8 8 7 7 7 7 8'' 8 9' 9 `~ 9 9 8 5 ~~ h ~ ~ f ,~rte ~ ' ase~ 8 8 7 9

0 5 5 5 5 6 6 5 5 5 5 5 5 6 6 7 5 6 6 WA ~ o IW: Potential Flow 5 6 5 6

~ fl- 8 7 7 8 8 8 7 7 7 7 8 8 9 9 9 9 9 8 3

o~ 8 8 7 9

~ 5 5 5 5 5 5 4 4 4 4 5 4 4 4 4 4 4 5 WA 5 5 4 4Z ERC: E~anded Response

EPC: E~anded 6 6 6 6 7 7 6 6 6 6 7 6 7 7 7 7 7 ~ Z

6 7 6 7 Pre aredness

33


ERA Consensus Wog°ksfaop - MG20A Platform - Gulf of Mexico

Tl1is Page Iptentionally Left Blank

34


ERA Co~~ser7si~s 1~1~or~kshop - A7C-20A Platform -Gulf of Mexico

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 t11e

final list of consensus conclusions and recommendations for the MG20 CERA. Those

conclusions and recommendations are listed in section 6.3.

6.2 Focus Group Discussion Points

6.2.1 Focus Group 1

Tl1e curi~cl~t situation po~e:~ n lo~v~ ecological risk to kno~~n biological resoti~rc~e~s. Mt~ltipl~

~•esponse 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 ace 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 contaimnent 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 i-isl<s/impacts Linder 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.

• Deilling intervention wells for all remaining wells does not provide adequate

ecological improvements when considered in the context of the impacts associated

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

function within an ecosystem.

35


ERA Consensus Gtior/zslzop - A~/G20A Platfor•~n -Gulf of~Mexico

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 iticremental ecological i~nprove~nents 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 locations) of the poii~t(s) of release needs to be developed to

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

time period foi• o»going releases. Utilization of the site for resea►-ch }purposes (as a form of instigation) should be

considered if no viable mechanism for fu►-ther reducing releases can be identified.

Research programs should include fate and effects of the nil 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:

36


F,RA Consensus I~Vorkshop - A1C-?OA Platform -Gulf of Mexico

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 MG20 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. 1»tervelltion 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 convetltional 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 MG20,

assuming that there was aworst-case discharge of up to 200 bbl/day. This capability could be

37


ERA Consensus Forks/zop - MC-20A Pla form - G2ulf of Mexico

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

K&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 silo auil ~~~gaged in discussions about possible response options. The evaluations and assessments made cl~arin~ 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 nil 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 t•isk 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. 'I~'he 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 nan-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.

38


FIZA Consensus Woi^kshop - MG20A Platform -Gulf of Mexico

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.

Tl~e 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 ~ncl c~e~rada.t.i~n.

Feasibility was discussed to help frame and understand each response option, but it did not factor into our ecological risk assessment. l'he llredge/Dispose option is considered infeasible and Dredge/Cap is likely infeasible. The well intervention options are technically feasible, but are undesirable because of t11e 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, tl~e 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 t11e 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 t}1e 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

39


ERA Consensus YVorkshop - A4G?OA Platfon~~ - Gulf of R~lexico

• Utilize the site f'or scientif7c 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 ~e~sirni and combined theie individual focus group findings into consensus conclusions and recotnrnendations. Their findings are presented below, as drafted by the participants.

6.3.1 Dredging Options

Dredging options, disposal or capping are ~1ot 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 i~~ultiple 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


HRA Consenszrs I~~orkshop - MC-20A Platform - Gu[f of~Mexico

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 capability could be ecologically beneficial for MG20 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 inay 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 t1SCG, the group t•ecommends that:

• Additional factors (e.g., wind speed, direction, sea state, % of dark/recoverable oil} be considered in a decisio~l matrix to determine threshold for response operations.

• Analyze historical sheen data to evaluate the ft•equency and procedures of over-flibht 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 be~lefits.

• 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 contaimnent solution for the worst case discharge (approximately Z00 bbl/day).

41


FRA Consensus Workshop - MG20A Platforn2 - Gulf of A~lexico


42


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

7.0 References

Aurand, D., L. Walko and R. Pot1d. 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 Tailure Analyses MC20-A Platform Block 20, Mississippi Canyon Area Gulf of Mexico. Report Nn. 0201-5381-7.

Taylor Energy Company. 2013. Report of Environmental Conditions and Actions Taken to assess and Minimize Environmeri~al Irr~pact. Mississippi Canyon 20 Gulf of Mexico. Taylor Enemy Company, Ne~~~ gleans, I,A 7.5 rakes.

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 Protectio» Agency. 1998. Guidelines for Ecological Risk Assessment. Federal Register 63 (93) of Thursday, May 14, 1998. pp. 26846-26924.

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F.RA Consensus 1~I~orkshop -ABC.-20A P/atforrn - Gzrlf of Mexico


..


ERA Consensus I~T~orkshop - MC-20A Platfoi•rn - Gulf of Mexico

Appendix A: Participants Workshop 1 Workshop 2

First Name Last Name Or anization 13•Ma 14-Ma 15-Ma 26-Jun 27-Jun 28-Jun Focus Group Jerry Alexander Independent Consultant for Taylor Energy X X X X X Technical Resource Mario Artea a Pla umines Parish Government X 1 Don Aurand HDR EM&A X X X X X X Facilitator K le Baker National Oceanic and Atmos heric Administration X X X X X X 1 Paul Barbre Bureau of Safet and Environmental Enforcement X X X X X X 2 Mike Beatt Beatt &Wozniak on behalf of Ta for Ener X X X Technical Resource Sam Bentle Louisiana State Universit on behalf of BSEE X X 2 Roberto Bernier United States Environmental Protection A enc , Re ion 6 X X X X X X 3 Dina Bracci Ta for Ener X X X X X X Technical Resource Darice Breedin Bureau of Ocean Ener Mana ement X X X 2 T.J. Broussard Bureau of Safet and Environmental Enforcement X Presenter Wade 6 ant United States Geolo ical Surve X X X X X X 3 John Calvin Bureau of Safet and Environmental Enforcement X X X 3 Rich Camilli Navistr Inc. on behalf ofTa for Ener X X X X X X 2 L Hard Carter Bureau of Safet and Environmental Enforcement X Presenter Mike Celala Bureau of Ocean Ener Mana ement X Observer Jeff Dauzat Louisiana De arlment of Environmental Qualit X X X X X X 2 Norman Du lanits Inde endent Consultant for Ta for Ener X X X X X X Technical Resource Denise Fields Ta for Ener X X X X X X Technical Resource £oan Fitz erald Unit?rl Statee Cnast Guard X

X X X

X X X X 2 Barry Forsythe United States Fish and Wildlife Service X X X X 1 Borrot Fortior ~Jn~rPr~ .~ratas Fish ~n~i Wildlife Service X

X X X

X X X X 2 Peter Gautier United States Coast Guard X X X X Nresenter 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 Slales 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 NOAH) 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 offaylor 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 Ener y 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


ERA Cor~sensars l~l~o~~kshop - ,MG20f1 Platform - Culf of ,Mexico



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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'E~nidio, A. Salusti and D. J. Jerolmack. 2012. Linking the historic 2011 Mississippi River flood to coastal wetland sedimentation. Nature Geoscience. DOI: 10.1038/NGE01615.

Wang, K. and E. E. Davis. 1996. Theory for the propagation of tidally induced pore pressure variations in layered subseaf7oor fo~•mations. Journal of Geophysical Research 101(BS): 11,483-11,495.

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