North Atlantic Right Whale Encounter Rates with Offshore Wind Energy O&M Vessels
Vessel encounter calculations using BOEM's risk assessment tool
Figure 1. Bureau of Ocean Energy Management Atlantic Wind Energy Areas, as of 08/13/2021
Introduction
Offshore wind energy development along the Atlantic Outer Continental Shelf (Atlantic OCS) is rapidly expanding to meet national renewable energy goals. Several endangered large whale species, including North Atlantic right whales (NARW), utilize the Atlantic OCS, and therefore the ability to predict impacts arising from wind energy operations within the Atlantic OCS is essential for responsible offshore wind planning and development. Under the National Environmental Policy Act (NEPA), the Bureau of Ocean Energy Management (BOEM) and other federal agencies are required to conduct environmental assessments of offshore wind development construction and operations plans (COPs). NEPA requires strike risk assessment and mitigation for vessels employed in offshore wind development and operations, and cumulative effects analysis. Under the Marine Mammal Protection Act (MMPA) and the Endangered Species Act (ESA), critically endangered North Atlantic right whales, which occur both seasonally and year-round in wind energy lease areas, are afforded federal protection. The resources NOAA expends on right whales, and has expended for decades, speaks to the importance of the issue.
This report is intended to quantify and evaluate risks associated with offshore wind energy development from vessel operations associated with the 25-35 year life cycle of offshore assets. It is presented as a dynamic document, to be updated regularly, as new information becomes available. Our research indicates that targeted conservation management strategies may reduce vessel strike risks, and may be used to mitigate this new source of vessel strike risks arising from offshore wind energy development. BOEM’s Risk Assessment to Model Encounter Rates Between Large Whales and Sea Turtles and Vessel Traffic from Offshore Wind Energy on the Atlantic OCS, central to this research, was designed for this purpose and appears to be underutilized.
North Atlantic right whale habitat preference for the Atlantic OCS, near-shore and shallow behavior, especially pronounced in mother-calf pairs, puts them acutely at risk for vessel strikes. With most offshore wind development overlapping the NARW seasonal migration route, and potential biological removal (PBR) threshold for the NARW stock at <1 individual (Hayes, et al., 2020), there is no tolerable level of mortality related to offshore wind vessel operations. The acutely high vulnerability, and population value, of reproductive females and calves emphasizes the the need for better protection than is currently planned.
The potential for vessel encounters with NARWs from intensive wind farm operations for the 25-35 year operational life of an offshore wind energy area (WEA) may be seen as a new and significant source of strike risk. To that end, assessments of vessel traffic and potential vessel strike impacts are required from offshore wind project developers. Nevertheless, no detailed assessment of vessel strike risk occurs over all phases of any project, and not cumulatively across multiple projects over time. Those risk assessments are required to inform National Environmental Policy Act (NEPA) decisions. With federal oversight of offshore wind projects, the Bureau of Ocean Energy Management (BOEM) is tasked with evaluating and regulating those strike risks, and to that end, BOEM has developed a vessel risk calculator (VRC) to predict encounter rates, to provide a means to assess vessel encounter risks across wind energy areas along the Atlantic OCS.
This paper reports on our results using the VRC to calculate the rate of vessel encounters with NARWs from routine crew transfers along transits routes to planned Atlantic OCS WEAs. O&M vessel traffic within WEAs is a related source of vessel strike risk, but is not addressed in this report.
Methods
BOEM's Risk Assessment to Model Encounter Rates Between Large Whales and Sea Turtles and Vessel Traffic from Offshore Wind Energy on the Atlantic OCS generates vessel risk calculations (VRC) associated with offshore wind energy. Methodology for the VRC can be found at BOEM 2021-034 and BOEM 2021-035. In this report the VRC was used to calculate vessel encounter rates with right whales for routine crew transfers to wind farms during operations and maintenance (O&M) at these federal lease areas:
Virginia Wind OCS-A 0483, Ocean Wind OCS-A 0498, Atlantic Shores OCS-A 0499, Vineyard Wind OCS-A 0501, Kitty Hawk Wind OCS-A 0508, Empire Wind OCS-A 0512, South Fork Wind OCS-A 0517, Vineyard Wind OCS-A 0534. Additional lease areas will periodically be analyzed and included in this report.
Three series of VRC calculations were run, to encompass a range of crew transfer scenarios for operations and maintenance. The first series relies entirely on O&M vessel transit estimates supplied by wind energy developers. The second series is for a hypothetical blend of SOVs and CTVs, and represents "better practices" in the context of this report. The third series pertains to a hypothetical scenario using SOVs and deployable work boats (DWB) and adherence to seasonal vessel speed rules, and represents an example of potential "best practices," in the context of this report.
Route Selection
Route selection was determined on a best-match basis with O&M bases indicated in COPs and pre-drawn routes supplied with the VRC (for example, Figure 2).
Figure 2. GUI screenshot of BOEM VRC showing O&M route to wind farm with encounter risk heatmap (BOEM 2021)
Publicly Available O&M Transit Estimate Documentation
The VRC requires monthly transit values to calculate encounter rates. The transit values used in this report are based on annual estimates sourced from the following:
Coastal Virginia Offshore Wind Commercial Project, Construction and Operations Plan, Dominion Energy
Ocean Wind Offshore Wind Construction & Operations Plan
Atlantic Shores Offshore Wind Navigation Safety Risk Assessment, EDF/Shell
Vineyard Wind Project Draft Construction & Operations Plan
Kitty Hawk Offshore Construction and Operations Plan
Empire Wind Project Construction & Operations Plan
South Fork Wind Farm Final Environmental Impact Statement
Vineyard Wind South Draft Construction and Operations Plan
Our calculations do not include vessel traffic within wind field areas; only transits from O&M bases to wind fields are addressed. We are mindful that vessel selection, wind development activities, and biological data may change over time, and that BOEM permits developers to take a Project Design Envelope (PDE) approach to their construction and operations plans. Similarly, this report is intended to be a dynamic document and will be kept up to date with new information, as it becomes available.
Modeling Transit and Encounter Rates based on Seasonality
We used the VRC to predict NARW encounter risks for wind farms still in planning and permitting stages, using estimated transit values from COPs. Not all COPs contain transit estimates (see discussion of PDE below), but transit estimates were available for the eight wind energy leases that form the locus for this report. Because COPs give transit estimates as annual values, and the VRC requires monthly transit values, monthly estimates were derived from the annual values supplied. To do this, we applied a seasonality model to produce monthly estimates.
We observed seasonality patterns in AIS vessel data from the two wind farms that are already operational in the OCS-A, Block Island Wind and Coastal Virginia Offshore Wind (figure 3). We used those data to derive estimated monthly transit values for the WEAs examined in this report. As another point of reference, we observed seasonality patterns in AIS data from Beatrice Wind Farm, Scotland, used by BOEM to develop the VRC (OCS Study, BOEM 2021-034).
We used AIS data for Block Island Wind to calculate seasonality for O&M operations in the northeast, using a three-year average (2017-2019) for the crew transfer vessel (CTV) in operation there, Atlantic Pioneer (MMSI 367722360); we used the first full-year (2021) of AIS data for CTV Atlantic Endeavor (MMSI 368169560), at Coastal Virginia Offshore Wind, to calculate seasonality for O&M operations in the mid-Atlantic. Raw AIS data for those areas is available here: Block Island Wind; Coastal Virginia Offshore Wind.
Steps in our methodology to produce monthly transit estimates are as follows:
Step 1. Ratio between (Transit Est/yr.) / (Transit Baseline) = Constant (Table 1)
Step 2. Product of (monthly transit value (Table 2)) x (Constant) = "number of trips” input to the VRC as a whole number (Figure 4)
Notes: Scalability of our seasonality observations of CTVs at small-scale operational wind farms may not be entirely applicable to larger WEAs, and may have limited applicability to SOV concepts generally.
Notes: The VRC uses a default transit speed of 25 knots for CTVs. Our observation of CTV transit speed at Block Island Wind and Virginia Offshore Wind indicate 21 knots is a more realistic average speed and is used instead. Sensitivity analysis of encounter rates in test runs of the VRC using 21 and 25-knot transit speeds resulted in only very minor differences in encounter rates and is not a significant factor influencing our results. There may be seasonal variations in transit speed, which we did not model.
Figure 3. Northeast and Mid-Atlantic Crew Transfer Seasonality, Transits to Block Island Wind (blue), and Coastal Virginia Offshore Wind (red)
Table 1. Transit estimates, AIS baseline values, and Constants for Risk Assessment calculation
Table 2. Monthly transits, Block Island Wind and Virginia Offshore Wind, from AstraPaging AIS data
Figure 4. GUI screenshot of BOEM VRC with parameters for Month, Vessel Category, Vessel Speed, Aversion and Number of Trips
Modeling Transit Estimate Calculations Based on Wind Turbine Totals
Additional encounter predictions may be calculated for lease areas that have not provided published transit rates based on wind turbine totals. BOEM’s Draft Guidance Regarding the Use of a Project Design Envelope in a Construction and Operations Plan (2018), permits lessees to take a Project Design Envelope (PDE) approach when submitting a construction and operations plan (COP), giving them the flexibility to submit a “reasonable range of project designs in a COP, because of the project complexity, the unpredictability of the environment in which it will be constructed, and/or the rapid pace of technological development within the industry.” For example, we see a range of transit estimates in many COPs, reflecting an understandable degree of uncertainty about specific combinations of SOV, CTV and DWB utilization for routine operations and maintenance in offshore wind energy areas.
While we recognize the value of flexibility in taking a PDE approach, it does not, in our view, permit the omission of transit estimates in many COPs. The absence of transit estimates does not “allow BOEM to analyze the environmental impacts of the proposed project,” and it does not allow for analysis of “the cumulative impacts of the “maximum design scenario” alongside other reasonably foreseeable past, present, and future actions.”
Because of the absence of detailed information for some areas, we plan to calculate transit rates in those instances based on the number of wind turbine generators (WTGs) planned by developers. The following wind energy projects represent the first set of lease areas for which we have derived transit values: Garden State Wind, Revolution Wind, Sunrise Wind, Mar Wind, Bay State Wind. These derived transit values will be input to BOEM’s VRC, to calculate encounter rates. When those results are available, they will be included in this report.
Results
We ran the VRC to assess vessel encounter risks to right whales along the Atlantic OCS to capture a range of crew transfer scenarios. The first series of runs relied entirely on O&M vessel transit estimates supplied by wind energy developers. The second series of runs was to test a hypothetical blend of SOVs and CTVs, and represents "better practices" in the context of this report. The third series pertains to a hypothetical scenario using SOVs and deployable work boats (DWB) and adherence to seasonal vessel speed rules, and represents an example of potential "best practices," in the context of this report.
Encounter Risk Assessment using COPs Transit Estimates
BOEM permits offshore wind energy developers to use a Project Design Envelope (PDE) approach in the preparation of COPs. This allows developers to present a range of Transit Estimates, which is the reason the first series of our runs of the VRC included both minimum and maximum vessel transit and vessel-to-whale encounter estimates. Using the VRC, we calculated 584 annual encounters (minimum), (Table 3), and 1,014 (maximum), (Table 4), from the set of eight OCS-A leases.
We made a conservative assumption that routine O&M will more closely align with the minimum values; if there are 584 annual encounters at these 8 leases, then the average annual encounter rate would be 73 (584/8 = 73), for a generic WEA. If that generic value of 73 is applied to all 12 active (Tier 1 & 2) lease areas, we may expect something on the order of 875 crew transfer encounters annually from those wind fields. There are, by our count, 28 OCS-A leases, expected to be operating by the end of this decade. Twenty-eight wind farms, each with a minimum vessel-to-whale encounter rate of 73 annually, would generate an aggregated encounter rate of approximately 2,000 right whale encounters per year, just from crew transfers to wind fields.
Raw BOEM results from these runs of the VRC are available here, linked to .txt output files:
Table 3. Minimum Transit Estimates and Encounter Results; subtotal reflects set of 8 offshore wind leases
Table 4. Maximum Transit Estimates and Encounter Results; subtotal reflects set of 8 offshore leases
Encounter Risk Assessment using Better Practices (SOV Utilization)
Service Operations Vessels (SOV) may be adopted for routine O&M, and would in our view represent "better practices." Using the annual Transit estimate of 52 for Virginia Wind OCS-A 0483, and assuming that it represents SOV utilization, we did a series of runs with the VRC modeled on crew transfers by SOV every two weeks, supplemented with CTVs. If the SOV makes 24 transits annually (every two weeks), there will be 28 unaccounted transits (52 -24 = 28), which we assume to be CTV transits. We assume that SOVs are not subject to seasonal variations, and that seasonality is applied only to CTV transits (Table 5 and Table 6).
The VRC calculated 125.38 annual encounters for our better practices model. We do not know which combinations of crew transfer options each wind farm will adopt, or how they may change over time. Various combinations of SOVs, CTVs, SATVs, DWBs, and helicopters are available for crew transfers, but the SOV/CTV calculation of 125 annual vessel-to-whale encounters represents a marked contrast to 584 encounters. It appears to reflect the difference between SOV and CTV models.
Table 5. Baseline transit values for SOV/CTV concept
Table 6. Encounters calculated for SOV/CTV concept
Encounter Risk Assessment for Best Practices (SOV/DWB Utilization)
To evaluate a hypothetical "best practices" scenario, we used the VRC to calculate encounters using a SOV/deployable work boat (DWB) concept (Table 7). An SOV, on-station on a two-week schedule, supplemented with DWBs for use within wind farms, could achieve a transit rate of 24 per year. This model assumes adherence to vessel speed regulations during months of elevated vessel-to-whale encounter risks.
The VRC calculated 119.10 annual encounters for our best practices model.
Note: SOV/DWB and SOV/CTV concepts produced similar vessel-to-whale encounter rates. The explanation for this is that lower vessel speeds increase VRC encounter rates; BOEM's description of this feature of the VRC is found in BOEM 2021-034. The essential point is that, although encounter rates are similar, vessel strikes at 10-knots are significantly less likely to result in injury or mortality to right whales (Crum, et al., 2019, Martin, et al., 2016, Vanderlaan and Taggart, 2007). In our view, this illustrates the importance of mandatory seasonal and dynamic speed restrictions, for all vessels irrespective of size, including CTVs and DWBs in transit and within WEAs.
Table 7. Encounters calculated for SOV/DWB concept
Discussion
Seasonality Adjustments to Reduce Encounter Rates
If routine O&M maintenance can be optimized for seasonality, to emphasize the lower encounter rates associated with those warmer months, vessel-to-whale encounter rates may be reduced. It appears that warmer months are already favored for wind field operations and maintenance, based on seasonality patterns observed at Block Island Wind and Coastal Virginia Wind. To the extent that it is possible to shift transits from high-risk months to low-risk months, dramatic reductions in encounter rates may be achieved. We plan to do sensitivity analysis using an optimized seasonality model using COP transit estimates to test the effectiveness of seasonality adjustments.
SOV Utilization to Reduce Encounter Rates
Decisions about the type of vessels to be used for crew transfer reflect a range of options influencing encounter risk. Crew transfer vessels (CTVs) have been used extensively in European and United Kingdom offshore wind farms and oil fields, requiring multiple daily transits to deliver and return crew from offshore facilities. Higher transit estimates seen in some of the Northeast and Mid-Atlantic Construction and Operations Plans (COPs) reflect the potential adoption of intensive CTV utilization for crew transfer along the Atlantic OCS and translates to elevated encounter risks to right whales. Some COPs reflect planning for an alternative to CTVs, using vessels to house crew offshore on support operation vessels (SOVs), resulting in lower crew transfer transit rates, and lower encounter rates with right whales. An SOV might remain in position for two weeks to four weeks at a time, suggesting further potential for risk reduction (Offshore Wind Report--Positioning for U.S. Expansion: U.S. Ports and Vessels Innovation, American Bureau of Shipping, 2021). Operations and maintenance crews housed aboard SOVs would reduce the need to return crew to shore-based facilities every day, thereby reducing transit totals, in many cases dramatically.
For recent SOV and CTV orders, acquisitions and utilization, see Offshore Wind Market Report: 2021 Edition, (U.S. Department of Energy, 2021).
Route Selection to Reduce Encounter Rates
Careful selection of O&M bases and routes to wind fields may decrease the frequency of right whale encounters. Certain bases and routes appear to be poor choices in this respect, producing high transit encounter rates. For example, COPs for Vineyard Wind OCS-A 0501 and OCS-A 0534 indicate Vineyard Haven as an O&M base, resulting in elevated encounter rates compared to an alternative O&M base, at New Bedford, Massachusetts.
Application of Speed Restrictions to Reduce Serious Injury and Mortality
Vessels serving federal offshore wind energy leases should be subject to speed restrictions, irrespective of size, with strict adherence to mandatory seasonal and dynamic management areas, irrespective of vessel size, and not subject to carve-outs using Incidental Take Authorizations. See North Atlantic Right Whale Vessel Speed Rule Assessment, NOAA Fisheries, 2020 and Best Management Practices for North Atlantic Right Whales During Offshore Wind Energy Construction and Operations Along the U.S. East Coast, Conservation Law Foundation, National Wildlife Federation, Natural Resources Defense Council, et al., 2019
Incidental Take Authorizations
NOAA has issued 24 Incidental Take Authorizations related to offshore wind energy since 2019 (Protected Resources Regulations & Actions, NOAA). Specifically, these are "incidental harassment authorizations to take, by Level A harassment and Level B harassment, marine mammals during construction of commercial wind energy projects, for offshore wind construction." We are concerned that this pronounced reliance on Incidental Take Authorization indicates potential for overuse and subsequent diminishment of effective legal protection.
Conclusion
Offshore wind energy vessel strikes on right whales may be avoided by adherence to best management practices, such as those outlined here, combined with best practices as described in the 2019 agreement between Vineyard Wind, LLC and the National Wildlife Federation, Natural Resources Defense Council and Conservation Law Foundation. We will continue to make our data, methods and results broadly available and accessible for evaluation on this website, to encourage the adoption of best practices, as new opportunities emerge. Feedback welcome.
Our goal has been to gain a preliminary, quantitative understanding of offshore wind energy vessel encounter risks to right whales. Additional analysis will go into more detail, to capture planning, construction, and operations as they proceed. Examples of future areas of study include: 1. Empirical verification/probability distribution of similarities between BOEM’s definition of encounters and MMPA's definition of Takes ("harassment"). 2. Mathematical optimization of seasonality models. 2. Vessel strike estimates based on encounter calculations. 3. VRC runs to analyze additional active leases (BOEM Tier 1 - 5 wind energy areas, future leases, call areas, remaindered leases, etc.). 4. Analysis of encounter rates, Takes and vessel strike estimates pertaining to O&M traffic within wind fields.
We hope our commitment to transparency and accessibility may give stakeholders and other interested parties opportunities to evaluate and improve on decisions made pursuant to offshore wind development.
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