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MODU Frequently Asked Questions (FAQs)

Please find  answers to commonly asked questions related to Mobile Offshore Drilling Units below.

Answers in this FAQ section are not a substitute for applicable legal requirements, nor are they rules (however, some questions may have an answer that comes directly from existing regulation or policy). The answers are not intended to require or impose legally binding requirements on any party. Answers provided represent the OCSNCOE’s current thinking, after researching existing regulations and policy, as well as consultation with Coast Guard Subject Matter Experts. These answers are intended to assist industry, mariners, the public, the Coast Guard and other regulators in applying statutory and regulatory requirements. When available, the FAQ will direct the reader to the official documents, such as the Federal Register, the Code of Federal Regulations or NVICs and policies. The answers provided are subject to change with regulatory or policy updates.

Regulatory Requirements

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 1) What regulatory requirements apply to MODUs examined under "Option A" (33 CFR 143.207(a))?

Foreign flagged MODUs choosing to comply with the "Option A" requirements of 33 CFR 143.207(a) must comply with the design and equipment requirements of 46 CFR Part 108, as applicable to the build date of the MODU. 46 CFR Subchapters F & J are not applicable as the paths to those subchapters are located in 46 CFR Part 107 (§107.231(a)), to which Option A MODUs are not subject. 46 CFR Subchapter S applies as the path to that subchapter is located at 46 CFR 108.301.

Option A MODUs will also typically comply with the operating requirements of 46 CFR 109, per 33 CFR 146.205(a).

Regulatory paths:
33 CFR 143.207(a) > 46 CFR Part 108 (including requirements of 46 CFR Subchapter S, via §108.301)
33 CFR 146.205(a) > 46 CFR Part 109

Additional regulatory guidance:
Marine Safety: Outer Continental Shelf Activities, COMDTINST 16000.76 (previously CG Marine Safety Manual (MSM) Vol II, Section G), Chapters 1 & 3

Note: With the cancellation of NVIC 3-88, there is no active regulatory guidance allowing the use of NVIC 4-78 (46 CFR 109, Appendix A) for Option A MODUs, as the only path to Appendix A is from 46 CFR Part 107 (§107.211(c) and §107.215(c)(2)).

Published 31Dec2018; updated 28Jun2022 to reflect MSM Vol II changes and clarify the note.

 2) Is Appendix A to 46 CFR Part 109 (NVIC 4-78) applicable to foreign flagged MODU’s?

Yes, if the foreign flagged MODU was issued an initial COC prior to June 25, 2014.

On June 25, 2014 NVIC 3-88 was cancelled and the Marine Safety Manual (MSM) Volume II, Section G was updated. With this update, NVIC 4-78 became applicable to foreign flagged MODUs only if it had previously held a U.S. Coast Guard Certificate of Inspection issued under 46 CFR Subchapter "I".

NVIC 4-78 applies to existing U.S. Flagged Mobile Offshore Drilling Units (MODUs) and existing foreign flagged units that meet specific prerequisites as further discussed below. The NVIC is included as Appendix A to 46 CFR Part 109.

"Existing units" are defined as units contracted for which are to be constructed and delivered prior to January 1, 1981.

NVIC 4-78 was historically applied to existing foreign flagged MODUs choosing to be inspected under 33 CFR 143.207(a) and 33 CFR 146.205(a), also known as Option "A". This provision was found in paragraph 3.B.2 of Enclosure (1) to NVIC 3-88, CH-1. Much of the NVIC 3-88, CH-1 content was incorporated into Marine Safety Manual (MSM), Volume II, CH-1, Section G, Chapter 3 (MSM II.G.3) on June 25, 2014 and NVIC 3-88, CH-1 was cancelled at that time.

Current guidance found in Chapter 3 of COMDTINST 16000.76 (previously MSM Vol II, Section G) at G.3.B.1.b (page G3-9) states "Existing MODUs – All existing units will be inspected as in the above paragraph. However, units contracted for before January 3, 1979, and issued a Certificate of Inspection (COI) under 46 Subchapter I [emphasis added] may continue to meet the requirements in force at the time of the COI issuance but must also meet the applicable requirements of 46 Subchapter I-A as specified in Navigation and Vessel Inspection Circular, "Inspection and Certification of Existing Mobile Offshore Drilling Units" (Appendix A of 46 CFR Part 109) until the unit is rebuilt. After a rebuild, the unit must meet the requirements of 46 CFR Subchapter I-A. The definition for REBUILT can be found in 33 CFR 140.10."

While NVIC 3-88, CH-1 allowed all existing units to utilize Appendix A (NVIC 4-78) of 46 CFR 109, the verbiage was modified with incorporation into the MSM to only allow the use of Appendix A by foreign flagged MODUs that were previously an existing U.S. flagged MODU that had been issued a COI under 46 Subchapter I. If a foreign flagged MODU does not meet these prerequisites, the unit can be examined under Option “A”, but cannot utilize 46 CFR 109 Appendix A (NVIC 4-78) and would have to use 46 CFR Parts 108 and 109 that are applicable to the build date(s) of the MODU.

Note: MSM Vol II CH-2 and CH-3 did not affect the content that was incorporated and discussed above for CH-1. CH-3 separated sections A through G of MSM Vol II into individual and independent Commandant Instructions with Section G becoming Marine Safety: Outer Continental Shelf Activities, COMDTINST 16000.76.

See the following flowchart for 46 CFR 109, Appendix A applicability. Files in pdf are available for the NVIC 4-78 Flowchart or the NVIC 4-78 Flowchart Print Version (click on the names).

NVIC 4-78 Flowchart

Published 22May2019; updated 28Jun2022 to reflect MSM Vol II changes.

Manning and Licensing

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 How many lifeboatmen are required on MODUs?

Is the number of lifeboatmen based on the total number of lifeboats onboard or on the number of lifeboats needed for 100% coverage of persons onboard (POB), since these types of units are required to maintain redundancy in lifeboat capacity?

Short answer: It is based on 100% coverage (but could vary/be increased by the Flag State Administration). Let’s take a further look…

Foreign-flagged units are pretty straightforward in that the Safe Manning Document sets the number of lifeboatmen required by the Administration. Many administrations base this off of the total number of lifeboats onboard.

Let’s look at some of the applicable cites to see the intent/how the minimum number would be determined:

2009 MODU 14.10.6 (14.10.5 before the 2017 amendments) requires certificated persons to be placed in command AND second-in-command of EACH lifeboat. Based on this cite, each lifeboat is required to have 2 lifeboatmen (note that this is not based on the capacity of the lifeboat, but is a straight 2-per lifeboat requirement). A typical drillship example with 6 lifeboats provided, 3 on each side (100% POB coverage on each side), would need 12 lifeboatmen based on the wording in this cite. The majority of Administrations choose to use the formula of 2 lifeboatmen multiplied by the total number of lifeboats to obtain the required number of lifeboatmen to list on their Minimum Safe Manning documents.

But wait, 2009 MODU 14.10.5 (14.10.4 before the 2017 amendments) requires sufficient certificated persons onboard to launch and operate the survival craft TO WHICH PERSONNEL ARE ASSIGNED. 2009 MODU 14.10.6 works in concert with 14.10.5. This puts an interesting twist to our 'typical' drillship example, and the station bill will need to be consulted to determine the appropriate number of lifeboatmen based on the boats to be used. A typical drillship meets the design and equipment requirements of 100% capacity on each side (2009 MODU 10.3.1) with 3 lifeboats on each side, but common practice across the industry is to assign personnel to the 4 forward lifeboats as their primary abandonment location/station.

Some examples of lifeboatmen numbers that would meet the intent in our drillship example, in accordance with 2009 MODU 14.10.5 & 14.10.6:
   • 3 lifeboats assigned (100% POB coverage), port or starboard boats (depending on scenario) = 6 lifeboatmen required
   • 4 forward lifeboats assigned (exceeds 100% POB coverage, but personnel are assigned to 4 boats) = 8 lifeboatmen required

2009 SOLAS III/10.4 helps to check the intent and is a little clearer than the MODU Codes, as it uses “each survival craft to be used” in the certificated person(s) requirement (2009 SOLAS was cited as that was the edition applicable when the 2009 MODU Code was adopted, although the cite and the verbiage is the same in the 2020 Consolidated Edition of SOLAS).

Essentially, an Administration that requires 12 lifeboatmen would cover most any muster/abandonment assignments scenario on our typical drillship example. If an Administration requires only 6 lifeboatmen on our example, the station bill/abandonment station assignments should reflect that arrangement (6 lifeboatmen wouldn’t be sufficient if the 4 forward boats were being utilized).

Note: If an Administration requires more lifeboatmen than the station bill/boat assignments require, the number stipulated on the Minimum Safe Manning document MUST be adhered to. If the station bill/boat assignments require more than the Administration stipulates, the required number set forth in the applicable MODU code must be complied with.

1989 MODU 14.9.5 and 14.9.4 are the same as the 2009 MODU cites discussed above.

The MODU Code (1979) does not specifically address the requirement related to manning of survival craft and the requirement will be stipulated by the Administration on the Minimum Safe Manning document. Note that 'emergency procedures' are located within Chapter 10 of the 79 Code, compared to Chapter 14 of the 89 & 09 Codes.

U.S. requirements follow a similar approach for MODUs. 46 CFR 109.323(c) requires a person to be placed in charge of each survival craft TO BE USED. §109.323(c)(1) requires them to be trained/certificated for those duties and §109.323(c)(2) requires the second-in-command for lifeboats permitted to carry MORE THAN 40 persons (41 POB and higher). Note that the biggest difference is that the lifeboat capacity determines when the second lifeboatman is required.

As supplementary guidance to the regulations, CG Marine Safety Manual Vol III/B.2.B.2.f discusses lifeboatmen and when/how many are required and uses the statement "each survival craft to be used" as well. This specific MSM cite is for mechanically-propelled vessels of 100 GRT or more, but is referenced as footnote 15 in B.2.O.1 (MODU sample manning).

Conclusion: Both IMO and U.S. requirements are aimed at providing lifeboatmen for the boats needed to accommodate evacuation of the persons onboard (100% of POB capacity), not providing lifeboatmen coverage for the redundant boats.

Published 14Dec2018; updated 28Jun2022 to reflect MSM Vol II changes and 2009 MODU Code amendments.

Emergency Evacuation Plans (EEPs)

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 1) Is the EEP drill required by 146.125(c)(1) required to be completed once per calendar year or once every 12 months?

Short answer: Once every 12 consecutive months.

Discussion: All elements of the EEP must be exercised through a drill or series of drills on an annual basis.

33 CFR 146.125(c)(1)"At least once a year, all the elements of the Emergency Evacuation Plan (EEP) under §146.140 relating to the evacuation of personnel from the facility must be exercised through a drill or a series of drills. The drill(s) must exercise all of the means and procedures listed in the EEP for each circumstance and condition described in the EEP under §146.140(d)(9)."

The wording is for a "year", rather than a "calendar year", and should be interpreted to mean a 12 consecutive month period. The EEP drill requirements were not part of the proposed rule (24Dec1987), but were added in the final rule (18May1989) as a response to industry comments as published at 54 FR 21568 where it was described as "annually":

"Four comments stated that the EEP regulations should contain a requirement for periodic evacuation drills. The comments stated that periodic interactive drills that test and exercise all the key elements of the EEP are needed to verify that the plan continues to be viable.
The Coast Guard agrees that the periodic drills are necessary to ensure that all personnel are familiar with the EEP. Therefore, a new § 146.125(c) has been added to require that abbreviated EEP drills be held monthly and that a comprehensive drill exercising all elements of the EEP be conducted annually. Also, a new § 146.140(e)(3) has been added to require the operator to ensure that the drills are conducted."

While some USCG operational regulations are specifically worded as a 12-month period, the majority of the types of USCG regulations are categorized as annual or "once in each year" and are treated as a consecutive 12-month period for compliance purposes. A once per "calendar year" requirement could give an extended window of time that would be outside of the intent of periodic training. As an example, a drill in Jan2019 followed by the next drill in Dec2020 could satisfy a once per calendar year requirement, but would clearly exceed the intent of annual, or once a year, training with nearly 24-months passing between drills.

Published 07Oct2021.

 2) What is an "element" of an Emergency Evacuation Plan (EEP) that is referenced in 33 CFR 146.125(c)(1)? Does the annual drill include all equipment (i.e., lifeboats) listed in the EEP?

Short answer: Elements are the components that make up the EEP and yes, the annual drill includes "all" equipment that is listed in the EEP.

Discussion: The phrase "all elements of the Emergency Evacuation Plan" as listed in the emergency drill requirements has often been questioned as to what it really means. Let’s take a look…

33 CFR 146.125(c)(1): "At least once a year, all the elements of the Emergency Evacuation Plan (EEP) under §146.140 relating to the evacuation of personnel from the facility must be exercised through a drill or a series of drills. The drill(s) must exercise all of the means and procedures listed in the EEP for each circumstance and condition described in the EEP under §146.140(d)(9)." [emphasis added]

The term "element" was added to the regulation with the final rule (published 18Mar1989) by the USCG in an effort to address industry comments to the proposed rule (published 24Dec1987).

Please note that the first sentence in the cite states "elements of the EEP under §146.140 relating to the evacuation of personnel from the facility". The requirements of the EEP relating to personnel evacuation are detailed in §146.140(d)(9) through (12) and include recognized circumstances that would place the facility or its personnel in jeopardy and for which a mass evacuation would be recommended. Fires, blowouts, approaching hurricanes and ice floes are specifically mentioned as examples of circumstances that would recommend an evacuation and collisions are another circumstance that is often included in typical EEPs that would initiate an evacuation.

The second sentence in the referenced cite states that "the drill(s) must exercise all of the means and procedures listed in the EEP for each circumstance" [emphasis added] to further stipulate what is required to satisfy the drill requirement.

Means and procedures are listed at §146.140(d)(12) as those for:

  1. retrieving persons from the water during an evacuation;
  2. transferring persons from the facility to the designated type of evacuation method (e.g. designated standby vessels, lifeboats or other evacuation craft);
  3. retrieving persons from the evacuation craft that they were transferred to in the previous requirement; and
  4. the ultimate evacuation of all persons to land, another facility or other location reasonably out of danger for the specific circumstance for the evacuation.

The District Eight OCS OCMI (responsible for the OCS activities on the U.S. OCS in the Gulf of Mexico) has interpreted §146.125(c)(1) "to mean that all lifeboats aboard a facility, shall, at a minimum, be launched with assigned lifeboat crew in order to fulfill the requirements of the annual emergency evacuation drill" in section 5, paragraph a, of D8(OCS) Policy Letter 01-2020, dated 19May2020. The policy letter goes on to discuss alternatives to this requirement in paragraphs 5.d through 5.f.

In the context of lifeboats/capsules, some have questioned if there is a need to test "all" of the boats for units or facilities with multiple boats, or if demonstrating the means and procedures with one, or a sampling of boats, would satisfy the intent. Note that the referenced cite states "all of the means and procedures" and the D8 OCS OCMI has reiterated this in Policy Letter 01-2020.

Also note that while the focus tends to be on lifeboats with this annual requirement, the cite requires exercise of all of the means and procedures for each circumstance that are stipulated in the EEP.

Published 07Oct2021.

Financial Responsibility

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 1) Is a fixed OCS facility, floating OCS facility (FOF) or a Mobile Offshore Drilling Unit (MODU) required to demonstrate Oil Spill Financial Responsibility (OSFR) and/or hold a Certificate of Financial Responsibility (COFR)?

Short answer:
Fixed OCS Facilities and FOFs are required to demonstrate OSFR and MODUs are required to carry a COFR for a tank vessel or a non-tank vessel based on its operation.

The requirements for an OSFR are found in 30 CFR 553 and the requirements for a COFR are found in 33 CFR 138.

This is based on 30 CFR 553.10:
(a) This part applies to any COF [Covered offshore facility] on any lease or permit issued or on any RUE [Right-of-use and easement] granted under the OCSLA or applicable State law.
(b) For a pipeline COF that extends onto land, this part applies to that portion of the pipeline lying seaward of the first accessible flow shut-off device on land.

Covered Offshore Facility (COF) in 30 CFR 553.3 means a facility:
(1) That includes any structure and all its components (including wells completed at the structure and the associated pipelines), equipment, pipeline or device (other than a vessel or other than a pipeline or deepwater port licensed under the Deepwater Port Act of 1974 (33 U.S.C. 1501 et seq.)) used for exploring for, drilling for, or producing oil or for transporting oil from such facilities. This includes a well drilled from a mobile offshore drilling unit (MODU) and the associated riser and well control equipment from the moment a drill shaft or other device first touches the seabed for purposes of exploring for, drilling for, or producing oil but it does not include the MODU; and…,

33 CFR 138.20(b) states:
For the purposes of applying the evidence of financial responsibility required under OPA 90 and this subpart and the limits of liability set forth in subpart B of this part, and in addition to any OPA 90 offshore facility evidence of financial responsibility requirements that may apply under 30 CFR part 553, a mobile offshore drilling unit is treated as -
   (1) A tank vessel when it is being used as an offshore facility; and
   (2) A vessel other than a tank vessel when it is not being used as an offshore facility.

33 CFR 138.230(d) states:
Offshore facilities. The OPA 90 limit of liability or offshore facilities other than deepwater ports, including for any offshore pipelines, is set forth at 30 CFR 553.702.

OSFR and COFR Applicability
  Oil Spill Financial Responsibility Certificate of Financial Responsibility
Mobile Offshore Drilling Unit No Yes
Floating OCS Facility Yes No
Fixed OCS Facility Yes No





Published 08Oct2020; cites updated 01Jul2022 to reflect 01Dec2021 amendments to 33 CFR Part 138.

 2) Does an FOF need to obtain or maintain a COFR before it arrives on location and BOEM's OSFR requirements take effect (i.e., during "tow-out")?

Short answer: FOFs that have been determined not to be vessels by the OCMI are not subject to the COFR requirements of 33 CFR Part 138.

Discussion: The question of whether a COFR applies to an FOF during the "tow-out" of the FOF from the quayside facility/construction yard to the installation location on the OCS has been a longstanding question. The Coast Guard revisited this question with internal discussions between the National Pollution Funds Center (NPFC), Headquarters and District Eight legal offices, District Eight OCS OCMI staff and the OCSNCOE during February of 2023.

Research and discussion affirmed that the COFR requirements imposed by the Oil Pollution Act of 1990 (OPA 90), 33 U.S.C. 2701-2761, and 33 CFR Part 138 that implements COFR requirements apply to vessels. Therefore, if an FOF is determined not to be a vessel, as evidenced by the issuance of a non-vessel determination letter in accordance with CG-OES Policy Letter 01-22, the requirements of 33 CFR Part 138 do not apply to these facilities during the tow-out phase of their construction and installation.

Note that the definitions in 33 U.S.C. 2701 and 33 CFR Part 138.220 are specific in regard to "vessels" and types of facilities and are essential to the applicability of a COFR. These definitions differ from more inclusive definitions of "ship" (i.e., vessel) in 33 CFR Subchapter O and MARPOL.

This non-applicability only applies to the USCG's COFR regulations and requirements if the facility is determined to be a non-vessel. The OSFR is a separate coverage found in BOEM regulations at 30 CFR 553 and provides financial responsibilities associated with the lease and lease-related operations.

NPFC issues a COFR to vessels in accordance with 33 U.S.C. 2716(a) and the regulations that implement the statute. OCS facilities (i.e., offshore facilities) have their own set of requirements under 33 U.S.C. 2716(c).

If an FOF is determined to be a vessel, a COFR would apply and a further determination of the correct limit of liability would need to be considered. This would be in addition to any OSFR requirements for OCS facilities that are determined to be vessels.

Published 14Mar2023.

Navigational Aids

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 1) What are the navigation light requirements for a MODU operating on dynamic positioning (DP), while attached to the seabed (e.g. drilling only, with no other obstructions)?

A MODU operating on DP and attached to the seabed is considered underway, not making way, and restricted in the ability to maneuver.

Lighting configuration:Restricted Maneuverability - Underway, not making way
   - Three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white.

Note: Masthead lights, sidelights and sternlight are NOT required, as the MODU is not making way and anchor lights are NOT required, as the MODU is not considered as "anchored".

Day shape configuration:
   - Three shapes in a vertical line where they can best be seen. The highest and lowest of these shapes shall be balls and the middle one a diamond.

See the follow-on question below, where additional lights and shapes may be required.

Are there additional navigation light requirements that apply to a MODU operating on dynamic positioning (DP), while obstructions exist in addition to the drilling equipment (e.g. ROV ops, subsea ops with the heave-compensated crane, etc.)?

Yes. Due to additional operations where obstructions exist to one side, the MODU may indicate the sides on which other vessels may and may not pass.

Lighting configuration:Restricted Maneuverability with obstructions - Underway, not making way
   - Restricted maneuverability lighting as described above (drilling only), PLUS;
   - Two all-round red lights in a vertical line to indicate the side on which the obstruction exists; and
   - Two all-round green lights in a vertical line to indicate the side on which another vessel may pass.

Day shape configuration:
   - Restricted maneuverability shapes as described above (drilling only), PLUS;
   - Two balls in a vertical line to indicate the side on which the obstruction exists; and
   - Two diamonds in a vertical line to indicate the side on which another vessel may pass.

MODU navigation lighting is also discussed on the USCG Navigation Center’s FAQ page by clicking here.

Published 14May2019.

 2) Do obstruction lights on self-elevating units (i.e., jack-ups) need to be level and focused?

Short Answer:



Note: This answer is based on conventional incandescent-type light assemblies. Manufacturer’s instructions should be consulted for LED lanterns or retrofits to ensure compliance with advertised/intended characteristics and range.

Part 1: Leveling

The "ridges" of the Fresnel lens found on obstruction lights serve a very important purpose. These ridges condense the light to the center of the lens and send out a type of light beam to meet the required range.

If the light is not level the focal plane will either be above or below the vessel. Either condition could reduce the required range, resulting in non-compliance with regulations and not meeting charted characteristics. See the graphical depiction below.

Graphic depicting focal planes of level and non-level aids to navigation lanterns

The leveling of the lantern can be checked via the built-in bubble levels of some lanterns or with the method displayed below (utilized by U.S. Coast Guard short-range aids to navigation technicians).

Graphic depicting how to verify the leveling of an aids to navigation lantern

Part 2: Focusing

There is another issue, especially on larger lights, that has to do with the "focus" of the light. For the light to be in focus, the lamp needs to be lined up with the center of the Fresnel lens. To check this, there are sighting marks (an "O" and "X" pair or two "X" pair) marked at 180° increments on the outside of the lens. When looking through the "O" to the "X" on the opposite side (180°) of the lens, the lamp should fall between the two sighting marks with the sighting marks aligned. The most common issue with the focus on certain model lights is when the bracket for the lamp changer mounts is installed upside down, which moves the lamp out of the focal plane of the lens.

The graphic below illustrates how to verify that a lantern is properly focused.

Graphic depicting how to verify the focusing of an aids to navigation lantern

Published 19Apr2021.