SUBMARINE CABLES IN OLYMPIC 

COAST NATIONAL MARINE 

SANCTUARY: HISTORY, IMPACT, AND 

MANAGEMENT LESSONS 

AUGUST 2018| sanctuaries.noaa.gov | MARINE SANCTUARIES CONSERVATION SERIES ONMS-18-01
U.S. Department of Commerce

Wilbur Ross, Secretary

National Oceanic and Atmospheric Administration

RDML Timothy Gallaudet, Acting Administrator

National Ocean Service

Russell Callender, Ph.D., Assistant Administrator

Office of National Marine Sanctuaries

John Armor, Director

Report Authors:

Liam Antrim1

, Len Balthis2, and Cynthia Cooksey3

1

Olympic Coast National Marine Sanctuary

2

National Centers for Coastal Ocean Science

3

National Marine Fisheries Service

Suggested Citation:

Antrim, L., Balthis, L., Cooksey, C. 2018. Submarine cables 

in Olympic Coast National Marine Sanctuary: History, 

Impact, and Management Lessons. Marine Sanctuaries 

Conservation Series ONMS-18-01. U.S. Department of 

Commerce, National Oceanic and Atmospheric 

Administration, Office of National Marine Sanctuaries, Silver 

Spring, MD. 60 pp. 

Cover Photo:

OCNMS. 
i

About the Marine Sanctuaries

Conservation Series

The Office of National Marine Sanctuaries, part of the National Oceanic and Atmospheric 

Administration, serves as the trustee for a system of marine protected areas encompassing 

more than 620,000 square miles of ocean and Great Lakes waters. The 13 national marine 

sanctuaries and two marine national monuments within the National Marine Sanctuary 

System represent areas of America’s ocean and Great Lakes environment that are of special 

national significance. Within their waters, giant humpback whales breed and calve their 

young, coral colonies flourish, and shipwrecks tell stories of our maritime history. Habitats 

include beautiful coral reefs, lush kelp forests, whale migration corridors, spectacular deepsea canyons, and underwater archaeological sites. These special places also provide homes 

to thousands of unique or endangered species and are important to America’s cultural 

heritage. Sites range in size from one square mile to almost 583,000 square miles and serve 

as natural classrooms, cherished recreational spots, and are home to valuable commercial 

industries.

Because of considerable differences in settings, resources, and threats, each marine 

sanctuary has a tailored management plan. Conservation, education, research, monitoring 

and enforcement programs vary accordingly. The integration of these programs is 

fundamental to marine protected area management. The Marine Sanctuaries Conservation 

Series reflects and supports this integration by providing a forum for publication and 

discussion of the complex issues currently facing the sanctuary system. Topics of 

published reports vary substantially and may include descriptions of educational programs, 

discussions on resource management issues, and results of scientific research and 

monitoring projects. The series facilitates integration of natural sciences, socioeconomic 

and cultural sciences, education, and policy development to accomplish the diverse needs 

of NOAA’s resource protection mandate. All publications are available on the Office of 

National Marine Sanctuaries website (http://www.sanctuaries.noaa.gov).
ii

Disclaimer

Report content does not necessarily reflect the views and policies of the Office of National 

Marine Sanctuaries or the National Oceanic and Atmospheric Administration, nor does the 

mention of trade names or commercial products constitute endorsement or recommendation 

for use.

Report Availability

Electronic copies of this report may be downloaded from the Office of National Marine 

Sanctuaries website at http://sanctuaries.noaa.gov. 

Contact

Carol Bernthal, Superintendent

Olympic Coast National Marine Sanctuary

115 E. Railroad Ave., Suite 301 

Port Angeles, WA 98362

Carol.Bernthal@noaa.gov
iii

Table of Contents

Table of Contents...............................................................................................................iii

Abstract.............................................................................................................................. iv

Key Words.......................................................................................................................... v

Introduction......................................................................................................................... 1

Cable History ...................................................................................................................... 5

Monitoring ........................................................................................................................ 10

Results............................................................................................................................... 16

Discussion......................................................................................................................... 42

Literature Cited ................................................................................................................. 48

Acknowledgements........................................................................................................... 52

Glossary of acronyms ....................................................................................................... 53

Appendices........................................................................................................................ 54
iv

Abstract

Two submarine cables were installed by plow burial in the seafloor through Olympic Coast 

National Marine Sanctuary for the Pacific Crossing fiber optic telecommunications system 

in 1999 and 2000. At the time, there were no published studies on impacts of submarine 

cable installation to seafloor habitats or biological communities. This made it challenging 

for resource management and permitting agencies to determine appropriate measures 

associated with these installations. A reasonable assumption was that the trenching 

required to bury the cables could disrupt benthic communities. As a result, the 

authorization to install the cable in Olympic Coast National Marine Sanctuary required 

post-installation field studies to monitor the impact of cable installation on benthic habitats 

and biological communities and the extent of recovery over time. 

A cable inspection survey contracted by PCL in 2001 revealed that significant portions of 

each PC-1 cable in the sanctuary were not buried to 0.6 meter depth, and considerable 

lengths of cable were unburied or suspended above the seafloor. Protracted negotiations 

between PCL, Tyco, OCNMS, U.S. Army Corps of Engineers, and the Makah Tribe 

resulted in an agreement requiring cable re-installation throughout the sanctuary. Reinstallation of the PC-1 cables was accomplished in 2006. Data analyzed in this report are 

from surveys completed between 2000 and 2004.

The monitoring program used a crewed submersible and remotely operated vehicle to 

collect video and still imagery of the seafloor. Benthic sediment grabs were collected 

across the affected area to characterize the seafloor and to verify habitat interpretation at 

locations where acoustic mapping data were available. Post-installation field studies 

conducted by sanctuary staff found recovery of seafloor habitats and biological 

communities to be relatively rapid, within months to a few years, particularly in areas of 

granular substrates. The longest lasting impacts may be changes to the physical structure 

of the seafloor along the trench. Investment in higher resolution data during the route 

planning phase can improve both cable burial and alignment of expectations between 

project proponents and marine area managers.

Sanctuary managers are responsible for balancing the needs of society, the ecological 

condition of natural resources, and consideration for existing uses of the area. The 

information presented in this report provides useful scientific information about the 

sanctuary’s benthic habitats as well as management implications and monitoring 

recommendations for cable installations. Effective cable route planning can help identify 

areas susceptible to significant or persistent impacts that could be avoided during project 

construction. In areas where user conflicts are clearly identified, such as where bottom 

contact fisheries are conducted, post-installation surveys of submarine cables are

recommended to identify where exposed cables put fishers at risk of snagging gear or 

damaging submarine cables.
v

Key Words

submarine cables, seafloor habitat, marine protected area, national marine sanctuary 
1

Introduction

Submarine cables are laid on the seafloor between land-based stations, typically for 

communications and electricity transmission. The first submarine communication cables 

were laid in the 1850s to carry telegraph messages. Modern telecommunications cables use 

optical fiber technology to connect continents across vast stretches of oceans. In nearshore 

and shallow waters where these cables are vulnerable to damage from fishing trawlers, 

anchors, earthquakes, and other external aggressions, burial of submarine cables for 

protection has been common practice since the early 1980s. Today, cable burial typically 

is recommended in waters shallower than 1,500 to 2,000 meters and is often accomplished 

using large seaplows towed across the seabed. The wedge-shaped plowshare (sometimes 

also a disc cutter) penetrates into the seabed to create a trench within which the cable is 

laid. With target burial depths of one meter or more, these seaplows are massive, skid

across the seafloor and cut deep into surface sediments. Jetted water can also be used to 

penetrate sediments and facilitate cable burial. Such cable burial methods physically 

disturb a swath of seafloor along the cable route. 

The Pacific Crossing-1 system (PC-1) consists of approximately 11,201 nautical miles 

(20,800 km) of submarine fiber optic cable for telecommunications between North 

America and Japan. This PC-1 system includes two cables originating in Washington state: 

PC-1 North that links to Japan and PC-1 East that links to Grover Beach, California. Off 

Washington state, the cables land at Mukilteo, Washington, and lie in U.S. waters through 

the Strait of Juan de Fuca. At the western end of the strait and across the northern portion 

of Olympic Coast National Marine Sanctuary (OCNMS, or sanctuary), both PC-1 cable 

routes run for approximately 29 nautical miles (52 km), roughly parallel to one another and 

separated by several hundred meters at water depths of 100-330 m (Figure 1). In 

November/December 1999 (PC-1 North) and February/March 2000 (PC-1 East), Tyco 

Submarine Systems, Ltd. (Tyco), on contract to Pacific Crossing, Ltd. (PCL), installed 

these cables off Washington using a Sea Plow VII, weighing 15.4 tons or over 30,000 

pounds (SEA 1999; Figure 2). The minimum anticipated service life for these cables was 

25 years (David Evans and Associates 1999).
2

Figure 1: Map showing location of PC-1 cable routes across the northern portion of OCNMS.

.

Figure 2: Sea Plow VII, similar to one used for initial PC-1 cable installation across OCNMS. The unit is 8.3 

m long, 4 m wide, 4.2 m tall and weighs 14.5 tons.
3

OCNMS is a federally designated marine protected area of special national significance, 

recognized for its rich natural resources and cultural values. OCNMS was designated in 

1994 and is one of 13 sites currently designated in U.S. waters under the authority of the 

National Marine Sanctuaries Act (NMSA; 16 U.S.C. § 1431 et seq.). OCNMS protects 

about 8,259 km2 of the Pacific Ocean between Cape Flattery and the mouth of the Copalis 

River, which cover the continental shelf as well as parts of three major submarine canyons. 

It has a coastline of about 217 km. This area contains an array of benthic habitats from 

rocky hard bottom to diverse soft-bottom sands and muds. Unconsolidated, soft-bottom 

sediments comprise the majority of habitat in the sanctuary (Figure 3). The soft-bottom 

habitats of OCNMS support a rich, diverse community of benthic fauna (Nelson et al. 

2008). Benthic fauna play critical roles in the ecosystem, including sediment bioturbation 

and stabilization, organic matter decomposition and nutrient regeneration, and secondary 

production and energy flow to higher trophic levels (Danovaro et al. 2008, Thistle 2003, 

Gage 2003, Gray 1981, Tenore 1977). Soft-bottom seafloor habitats are important 

reservoirs of marine biodiversity (e.g., Hessler and Sanders 1967, Jumars 1976, Hecker 

and Paul 1979, Rex 1981, Grassle and Morse-Porteous 1987, Grassle and Maciolek 1992, 

Nelson et al. 2008). From a cultural perspective, the Olympic Coast has sustained human 

communities for at least 6,000 years. The sanctuary lies within the traditional fishing areas 

for four coastal Indian tribes: the Makah, Quileute, and Hoh tribes, and the Quinault Indian 

Nation. Over 180 documented shipwrecks have historical association with the Olympic 

Coast.
4

OCNMS regulations prohibit specific activities within or beyond sanctuary boundaries that 

could injure sanctuary resources or qualities (15 CFR § 922.152). Because PC-1 submarine 

cable installation involves significant seafloor disturbance and placement of a structure on 

the seabed, it would not be allowed under 15 CFR § 922.152(a)(4), which prohibits

“drilling into, dredging or otherwise altering the seabed of the sanctuary; or constructing, 

placing or abandoning any structure, material or other matter on the seabed of the 

sanctuary”. But the NMSA also directs NOAA to “support, promote, and coordinate 

scientific research on, and long-term monitoring of, the resources of these marine areas;

[and] to facilitate to the extent compatible with the primary objective of resource 

protection, all public and private uses of the resources of these marine areas not prohibited

pursuant to other authorities” (16 U.S.C. 1431 (b)(5) and (6)). Thus, OCNMS regulations

can allow exceptions to these otherwise prohibited activities through established permitting 

processes. 

Figure 3: Predominant benthic sediments along PC-1 routes 

in OCNMS include unconsolidated soft mud and sand 

composition with bedrock outcrops and boulders. (Coastal & 

Marine Ecological Classification Standard).
5

Cable History

Permitting

Pacific Crossing applied for and received permits from Army Corps of Engineers and 

OCNMS to install PC-1 cables through the sanctuary. Cable burial is the primary method 

used to protect cables from external aggressions in continental shelf areas with active 

fisheries, and was an industry standard identified by PCL throughout PC-1 project 

planning. The Supplemental Environmental Assessment prepared by the cable installer 

indicated the seafloor, described as primarily gravel, cobble, sand, and clay along the 

preferred route through the sanctuary (C&C Technologies 1999), was suitable for burial 

(SEA 1999). The OCNMS permit for this project, issued in November 1999 

(Authorization/ Special Use Permit Number OCNMS-01-99), contained special conditions, 

including condition 2.A.v, which reads: 

“Within the Sanctuary, the cables shall be buried wherever possible. Where 

plow-burial is not possible, ROV burial shall be used. The authorization/special 

use Permit holder shall seek to bury the cables in sediments to a depth of 

between 0.6 – 1 m. Plow-burial shall be undertaken in such a way and at such 

speeds so as to minimize turbidity. If burial is not possible due to the substrate 

encountered, the Permit holder shall notify the sanctuary Superintendent and 

positions shall be provided to fishing groups, OCNMS, NMFS, Coast Survey, 

and the U.S. Coast Guard at the completion of construction. No blasting shall

be allowed in the Sanctuary.” 

This language acknowledged that in limited locations the target burial depth might not be 

achieved due to the substrate or other conditions encountered. Nevertheless, the permit 

provisions sought to minimize conflicts with bottom contact commercial fisheries, acute 

and chronic disturbance to the seafloor and natural resources, and the risk of cable failure

and disturbance during repairs. 

Cable Installation and Burial

The requirement for cable burial as the primary method of cable protection in water depths 

less than 1000 meters is an industry standard. It was prioritized from the start of PC-1 

project planning in the Desk Study Report, the first document to review the cable routes 

and recommend requirements for submarine cables proposed for the entire PC-1 cable 

network (C&C Technologies 1998). Addressing cable protection it states, “Cable burial, 

where feasible, should be considered essential to cable protection... Simultaneous cable 

burial by plough to a minimum of 1.0 m should be considered as the primary method” 

(C&C Technologies 1998). The Final Route Survey Report noted that “the single greatest 

threat to the integrity of submarine cables is bottom trawling” (p. 34, C&C Technologies 

1999). Bottom trawls used in the study area can penetrate more than 0.1 m into most 
6

seafloor sediments and as much as 0.3 m in soft substrates (SEA 1999). The SEA stated 

the objective “to provide the maximum separation between cables and fishing gear that 

may penetrate the seabed” (SEA 1999). From the cable owner’s perspective, these repeated 

statements of intent and need to bury the PC-1 fiber optic cables emphasize the importance 

of cable burial for maintenance of cable integrity. Lack of success in achieving cable burial 

to >0.6 meter depth over significant portions of the PC-1 routes in OCNMS would put the 

cables at significantly higher risk of damage and fault from external aggressions. For the 

PC-1 system in OCNMS, this is a particular concern because light wire armored (LWA) 

cable was used where bottom fishing activity was well documented. LWA cable is 

designed to be protected by burial (C&C Technologies 1998, David Evans and Associates 

1998, SEA 1999). It was not designed to withstand persistent suspension, exposure, and 

external aggression, and typically is not used where seabed exposure is anticipated (Wilson 

and June 2002). 

Effective cable burial reduces the possibility that additional disturbance to benthic 

communities would be necessitated by cable repair. The SEA, completed before permit 

issuance specifically to address the OCNMS portion of the system, stated “There is only a 

1.5 percent chance that there would be a repair due to submerged plant failure within the 

sanctuary over the entire 25 year design life of the system.” This risk estimate includes 

malfunction in a repeater, or in-line amplifiers periodically incorporated into the cable, as 

well as cable fault from physical damage to the cables. 

In 2000, it was not a common industry practice to conduct a thorough post-installation 

inspection of achieved cable burial, which could have been accomplished by visual 

inspection of the cable route(s) to note where unburied cable was visible or using 

equipment designed to measure cable depth relative to the sediment surface. 

Consequently, an assessment of achieved cable burial success was not completed 

immediately after the PC-1 cable installations through OCNMS. Post-installation reports 

based on data collected during installation operations indicated the cables were 

“successfully buried” throughout the sanctuary, with relatively shallow burial by jetting at 

cable crossings (Tyco 2000a, Tyco 2000b). These data, however, document plow and cable 

tension parameters and do not consistently and accurately reflect the achieved cable burial, 

or position of the cable relative to the seafloor in its installed state. 

The first visual inspection of PC-1 cables in the sanctuary was conducted in 2000 by 

OCNMS during the habitat and biological community recovery study. Video taken along 

the PC-1 East cable route revealed that considerable portions of cable were unburied and 

suspended above the seafloor. This prompted an inspection status survey of PC-1 cables 

by the permittee in June 2001, which was limited to the cable route segments within 

OCNMS. This survey revealed that 6.2 percent of PC-1 East in OCNMS was unburied 

(3.4 kilometers cumulative length, including 1.7 kilometer cumulative length of cable 

suspended above the seafloor) and 1.6 percent of PC-1 North was unburied (0.8 kilometer 

cumulative length, including 0.2 kilometer cumulative length of cable suspended above the 

seafloor) (ERM 2002). Unburied and suspended sections were widely distributed over the 
7

PC-1 routes through the sanctuary and at some locations appeared to be at risk as exposed 

cable occurred in areas with active commercial fishing. In addition, at numerous places 

the cables were found to be suspended over boulders, points at which physical abrasion can 

damage cables resulting in an operational failure or fault. Adding to this concern, surveys 

conducted in 2001 by OCNMS, about 18 months after cable installation, revealed damage 

to the outer protective layers of the cable and exposed metal armoring in several places. 

By September 2003, fraying of the outer protective layers of cable and exposure of metal 

armoring appeared to have increased over time where cable was suspended over rock near 

the western edge of the sanctuary. OCNMS was concerned primarily about three issues: 

risk to commercial bottom trawl fishers of gear snags on exposed cable, limitations on 

access to usual and accustomed fishing grounds of the Makah Tribe, and exposed cable 

susceptible to faults requiring repeated repairs and seabed disturbance in the future. 

After the unsuccessful burial was discovered, a cable burial status survey was completed 

in June 2001, and the results were summarized in two reports (ERM 2001, ERM 2002). 

These reports concluded that sediment type encountered, seabed conditions, and post-lay 

burial operations were the principal causes for not attaining 100 percent cable burial. 

For an independent evaluation, NOAA contracted with marine geology experts who 

reviewed geophysical data and post-installation seafloor video. Their analyses concluded 

that 1) sediments along the existing PC-1 routes in OCNMS are suitable for sea plow burial 

with exception of limited areas (Greene and Watt 2002; Bornhold 2003); 2) it is unlikely 

that new sediment deposits would eventually cover and protect the cable where it was 

unburied (Greene and Watt 2002, Bornhold 2003); 3) strumming or vibration of unburied 

cable would prevent natural burial of the cable and could result in further excavation of the 

cable (Greene and Watt 2002); and 4) inadequate pre-installation geophysical 

characterization of the cable routes in OCNMS, inattention to potential problem areas, and 

deviation from the proposed cable routes likely contributed to cable burial of <0.6 meter 

depth (Bornhold 2003). 

NOAA also contracted cable installation experts who reviewed geophysical data, cable 

installation records, and post-installation seafloor video to conclude that two operational 

factors contributed significantly to shallow buried, unburied, and suspended PC-1 cables 

in OCNMS: high residual tension, or tension remaining on the cables after installation, and 

plowing speed (Wilson and Darbyshire 2003). During installation even where the plow 

penetrated effectively into sediments, patterns of fluctuating and generally high residual 

tension levels in some locations prevented the cable from remaining buried deep under 

sediments. Compounding this issue, these experts concluded that the average installation 

speeds were high for the sea conditions and substrates encountered particularly during 

installation of PC-1 East. High residual tension also likely contributed to sub-standard 

burial at the two cable crossings along the PC-1 routes in OCNMS. At crossings points 

submarine cables are surface laid, not plow-buried, and post-lay water jetting operations 

are employed to bury cable. Burial on both PC-1 cables was generally poor at cable 

crossings where substrates appeared conducive to cable burial, indicating that tension in 
8

the cables limited effectiveness of jetting operations. Tension on the cables prevents them

from relaxing into fluidized sediments during jetting operations. In general, it is probable 

that cable burial depth could have been improved during initial installations by reducing 

the plow speed and giving greater attention to residual tension (Wilson and June 2002). 

It must be acknowledged that seaplow installation of submarine cables is not an exact 

science. Cable burial is susceptible to a multitude of unpredictable and immeasurable 

pressures, forces and circumstances that should be considered during planning, permitting,

and evaluation phases of submarine cable projects (Wilson and Darbyshire 2003, ERM 

2002).

Monitoring Requirement

In 1999, buried installation of fiber optic submarine cables was a relatively recent 

technology, and environmental impacts of this technology were not well documented. 

Furthermore, the Sea Plow VII used to install the PC-1 cables weighed nearly 15 tons. The 

massive tool uses a disc cutter to lift a soil wedge at a 35° angle and the 0.3 meter wide 

plowshare can penetrate over a meter into sediment as the cable is laid. In addition, the sea 

plow’s skids move across the sediment surface applying pressure, which can crush 

epibenthic organisms over an installation swath 5.8 meters (19 feet) wide (SEA 1999).

Therefore, a requirement of PCL’s sanctuary permit was to fund what permit language 

called “a comprehensive monitoring program,” which OCNMS implemented to determine 

impacts to the seafloor habitat and biological communities from cable installation and to 

assess the recovery of these communities over time. This monitoring program supported 

an evaluation of dual goals of OCNMS: conservation of natural and maritime heritage 

resources and multiple use, as articulated in the National Marine Sanctuaries Act (16 

U.S.C. §§ 1431 et seq.). Specifically, post-installation monitoring was to address the 

question: “Can this type of human-caused disturbance be accommodated while conserving 

biological diversity within a national marine sanctuary?” 

OCNMS began habitat and community recovery monitoring of the PC-1 East cable in 

September 2000, less than one year following installation. PC-1 North had been installed 

several months earlier, and was not as suitable as the more recent installation for evaluation 

of initial impact. Video and grab samples were taken to characterize the seafloor biological 

communities and habitats along the PC-1 cable routes and in adjacent areas that were not 

disturbed by cabling for comparison. Additional surveys were completed in 2001, 2003,

and 2004 and included portions of both PC-1 cables in the sanctuary. 

While the goal of this monitoring program was to assess physical disturbance and 

biological community recovery from the cable installation, one objective had been to 

compare this disturbance, a one-time event, to that from chronic commercial bottom 

trawling. Unfortunately, the lack of precise location data from trawling, its widespread 
9

impact (i.e., across habitat types), and the high spatial resolution required for the cable 

assessment precluded this. 

The monitoring program also provided an opportunity to establish baseline information on 

benthic communities within the northernmost portion of the sanctuary, where future cable 

laying was most likely to occur. Information on benthic communities and benthic habitats 

within the sanctuary, combined with estimates of recovery from submarine cable 

installation, would provide natural resource managers with information critical for future 

cable permitting and the ability to improve the design of future impact assessments.
10

Monitoring

To reach the seafloor at depths of 100 meters or more and to conduct surveys along a 

narrow swath where the cables were placed, the monitoring program required use of a 

submersible and remotely operated vehicle (ROV). Although no survey was conducted 

immediately after installation of the cable in late 1999, OCNMS completed surveys in all 

years between 2000 and 2004, except 2002 when efforts were thwarted by equipment 

failures. The crewed submersible Delta, owned by Delta Oceanographics, was used in 

September 2000 and September 2001 (Figure 4), and an ROV, the Canadian Scientific 

Submersible Facility’s ROPOS, was used in September 2003 and August 2004 (Figure 5). 

Though installation occurred in the fall and the surveys occurred in the spring/summer 

months, because of the depth of the benthic habitat, NOAA assumed there was not a strong

seasonal signal in the microbenthic community being monitored. Both platforms had 

cameras to collect video and still imagery, manipulator arms and tools for benthic 

collections, and a cable sensor to locate the cable where a visible trench was not apparent. 

During these surveys of the PC-1 cable routes, benthic sediment grabs were collected 

across the northern sanctuary area using a Smith-McIntyre grab sampler (0.1 m2 sample 

area). These sediment samples were used to characterize the sanctuary’s seafloor, to verify 

habitat interpretation at locations where acoustic mapping data were available.

Figure 4: The Delta submersible owned and operated by Delta Oceanographics
11

Figure 5: The ROPOS ROV owned and operated by the Canadian Scientific Submersible Facility

Physical Disturbance from Plow-Burial 

Monitoring for physical disturbance focused on a 2-3 m swath captured by the ROV’s 

cameras along the cable route and trench that typically remained where the plowshare cut 

into sediment. Physical disturbance to seafloor substrate and habitat was documented as 

presence/absence of a visible trench, essentially a linear scar or depression across the 

seafloor along the cable route, and qualitative characterization included differences in 

shape, size, and persistence in relation to sediment types. 

Physical Disturbance from Fish Trawls

Given the recognition of impacts in the area caused by bottom trawling, and the potential 

conflict between cables and fishing gear, a reasonable monitoring objective would be to 

compare the physical and biological impacts of both. Unfortunately, data on fishing 

intensity in the area are lumped into 10 by 10 nautical mile blocks, and the fishing itself 

can be conducted across multiple habitat types during any given deployment. For a study 

on cable impacts, comparisons were required within habitats, and in proximity to a 

comparatively narrow cable trench, which required much finer scale sampling. Comparing

cable vs. bottom trawl impacts would require a different study design than used here. 

Survey Design

A stratified-random sampling design was used to survey the benthos along the cable route 

and in locations away from the cable route within the sanctuary. Strata and corresponding 

survey transects (Figure 6) were based on bottom type (sand, mud, gravel). Areas along 

the PC-1 cable routes with exposed and suspended cable were not included in these 

surveys, first because of the risk of gear entanglement or damage to the cable by 
12

submersible or ROV operations. Secondly, the continued disturbance caused by movement 

of an exposed or suspended cable precludes the evaluation of recovery.

Figure 6: Locations of video survey transects along cable route, primarily along PC-1 East which was installed 

approximately six months prior to the initial monitoring surveys.

Seafloor Habitat

To plan initial surveys, seafloor habitat types along the PC-1 routes were characterized 

using available side scan sonar imagery and video taken during the cable laying process. 

Following completion of each OCNMS survey, habitat characterization was refined by 

review of video and classification of the primary and secondary sediment types using 

categories of substrate texture of mud, sand, and gravel following Greene et al. (1999).

Benthic Grab Sampling

To characterize the benthic community in the northern sanctuary and general vicinity of 

the PC-1 cable routes, sediment grab samples were collected using a Smith McIntyre grab 

sampler (0.1 m2) deployed from the research vessel. Samples were collected 

opportunistically along the cable routes when ROV operations were halted, and along 

transects and opportunistically over a larger area (Figure 7). Grab samples were not 

collected within 0.2 km of the cable routes due to risk of exposed cables. Benthic infauna 

samples were processed on the vessel by wet sieving sediment through a 1 mm screen, then 
13

collecting and preserving biota retained on the screen. Specimens were sent to expert 

taxonomists for enumeration and identification to the lowest feasible taxonomic level. 

Samples for grain size analysis were subsampled from grab samples and sent to a qualified 

laboratory for analysis.

Figure 7: Smith McIntyre benthic grab stations, 2000 – 2004.

Population and community-level indices were used to characterize the benthic infaunal 

assemblages inhabiting the soft-bottom sediments. These included species richness, H′ 

diversity (Shannon and Weaver 1949) derived with base-2 logarithms, density (m-2

) of total 

fauna (all species combined), and density of numerically dominant fauna. Similarities in 

the community of benthic infauna among stations were examined by hierarchical cluster 

analysis using double-square-root-transformed abundance. Group-average sorting 

(unweighted pair-group method; Sneath and Sokal 1973) was used as the clustering method 

and Bray-Curtis dissimilarity (Bray and Curtis 1957) was used as the resemblance measure 

for abundance data aggregated to taxonomic order, and represented as a dendrogram in 

which samples were ordered into groups of increasing similarity based on resemblances of 

component-species abundances. Ordination methods on unaggregated species data (nonmetric multidimensional scaling; NMDS) were used to assess similarity of benthic 

assemblages within and among three sediments types (sand, gravel, mud). Principal 
14

Components Analysis (PCA) of abiotic data (sediment type and water depth) was 

performed on normalized data. Similarity Percentage (SIMPER) one-way analysis among 

the three dominant sediment types was completed on data aggregated to the order level to 

quantify the percentage contribution of each order to the overall similarity/dissimilarity 

within and between habitat types. All multivariate analyses were performed in PRIMER 

6 (Clarke and Gorley 2006). 

Cable Route Transects and Sediment Samples

Directly along the cable route and adjacent control areas, sediment and organisms were 

recorded from video and still photography, and suction samples were collected using tools 

attached to the submarine and ROV. Video provided information on the epibenthic 

community, or organisms living on or visible at the sediment surface. Suction samples 

provided information on organisms living both on (epibenthos) and within (infauna) 

sediments.

Video transects were established directly along the cable route (on cable; Figure 6) where 

the cable was buried, and control transects were along a parallel route offset about 50 m to 

the south from the cables. It was assumed that a route close and parallel to the cable route 

would provide the closest equivalent to the habitat and species composition present before 

disturbance from the cable laying. The submersible (2000, 2001) or ROV (2003, 2004) was 

equipped with a video camera and two or four lasers emitting parallel beams to allow 

quantitative analysis from video footage. The width of the field of view was calculated as

ffffffffff ww wwh (mm) = [( ww ⋅ ss )/mm ] ⋅ 0.01,

where lw = distance between lasers (10 cm), sw = viewable screen width (39 cm), and mw

= on-screen measured distance (in cm) between lasers. The total area of each transect 

segment was calculated as field width x length (50 m), and used to estimate invertebrate 

density (# m-2

) as count/area. Videos were acquired at ~1 knot survey speed.

Within each habitat type, video transects were selected following a stratified random 

sampling approach. Three 20-minute video transects were selected in each habitat type 

along both the cable corridor and the parallel or control route 50 m to the south. The start 

point for these transects was randomly selected within the habitat type using Geographic 

Information System software. The ability to complete three, 20-minute transects of a 

particular habitat type depended on the homogeneity of the bottom habitat. For instance, 

if gravel habitat was encountered, it may not have extended far enough to allow for >60

minutes of video. The number of transects completed was dictated by the number of 

successful dives during field operations in a given year.

Video review was conducted by OCNMS staff in two stages. First, substrate type (sand, 

mud, or gravel), cable burial status (buried or exposed), and trench depth were 

characterized. Next, epibenthic invertebrate taxa were counted and identified to the lowest 
15

taxonomic level possible. Paired transects (On cable vs. Control) were post-processed in 

a Geographic Information System (GIS) and partitioned into 50-m segments. From each 

paired transect, every other 50-m segment was selected for analysis in order to minimize 

spatial autocorrelation. The paired 50-m segments were matched geographically between 

years, so that matching, paired 50-m segments were used for within and between years

comparisons (even though not all transect segments were surveyed in each year of 

sampling).

Collection of three replicate suction samples (0.1 m2 x 6 cm deep) was attempted within 

each habitat type along the cable corridor and the parallel or control route. To collect these 

samples, a metal ring 0.1 m2 in area was placed on the seafloor, and a suction hose 

manipulated by the ROV was used to pull the upper 6 cm of deposits with water through a 

filter (1 ml mesh), on which organisms were captured. Specimens were sent to expert 

taxonomists for enumeration and identification to the lowest feasible taxonomic level.
16

Results

Physical Disturbance

Physical disturbance to seafloor habitats from cable installation was visible along the 

installation route. A linear depression in the seabed substrate, was clearly present in years 

immediately following cable installation along significant portions of PC-1 cable routes 

(Figure 8). During the first post-installation survey, approximately 10 months after 

installation, the trench typically looked wedge shaped with vertical face up to 0.5 m tall on 

one side where well defined, particularly in areas of cohesive sediments (e.g., clays). 

Where there were non-cohesive or unconsolidated substrate types, the trench scar on the 

seafloor was shallower, more symmetric, and lacked a distinct vertical face.
17

Figure 8. Examples of seafloor disturbance and visible trench along PC-1 cables in OCNMS. Vertical face 

on side of trench is more distinct in middle photo. Bottom photo shows exposed cable in visible trench through 

gravel/cobble substrate. 

Because trench data were not recorded in a systematic manner during video review, 

interpretation of this information was qualitative and limited to presence/absence of a 

visible trench. In general terms, a trench was visible more often than not in 2000-2003 in 

video transects. No survey was completed in 2002. More observations of trench presence 

were recorded in 2000 and 2001 than in 2003, suggesting surficial substrate recovery to 

pre-installation conditions. By the 2004 survey, completed more than 4.5 years after cable 

installations, no observations of visible trench were recorded; trench absence was routinely 

recorded.

The persistence of a visible trench was dependent on substrate type. Trench presence or 

absence was noted along video transects, with 57 percent of observations in areas 

dominated by sand, 29 percent by mud, 10 percent by clay, and 4 percent by gravel. 

Trenches were observed almost exclusively in sand (60 percent) and mud (40 percent)

habitats, all years combined. Few observations of visible trench (<2 percent) were recorded 

where the substrate was predominantly clay. A visible trench was never noted where 

substrate was predominantly gravel in 2000 or later years. The proportion of visible trench 

observations at different substrate types changed over time, with a lower proportion of 

observations of visible trench in mud and higher proportion in sand substrate between 2000 

and 2003. In 2000, 56 percent of visible trench observations were in sand substrate and 44 

percent in mud substrate. By 2003, 83 percent of visible trench observations were in sand 

substrate and 15 percent in mud substrate.

Benthic community characterization of northern sanctuary waters

A total of 133 grab stations were sampled from 2000 to 2004 for benthic infauna (see Figure 

9 and Appendix A). Stations were broadly distributed across the northern sanctuary, 

between 48.1o N and 48.5o N, as far west as 125.4o W, within and adjacent to the Juan de 

Fuca Canyon complex at water depths between 40 and 1035 meters depth. Of those 133 
18

stations 114 stations, all collected during 2000 and 2001, had corresponding grain-size 

information and could be used for the analysis of spatial patterns associated with substrate 

type (Table 1 and Appendix B).

Table 1. Water depth and key benthic community metrics averaged by year, dominant sediment type, 

and year x dominant sediment type for 2000 and 2001.

Mean Water

Depth (m)*

Mean

Richness

(#taxa/grab)

Mean

Diversity

(H ́/grab)

Mean

Density

(#/m2)

Year 2000 567.2 28 3.9 869.0

2001 165.3 41 4.4 1450.5

Sediment Type Gravel 358.2 44 4.8 1226.1

Sand 334.2 35 3.9 1409.6

Mud 346.6 15 3.3 349.0

Year x Sed. Type 2000 Gravel 493.6 33 4.5 690.9

Sand 633.0 27 3.5 1231.0

Mud 644.4 9 2.8 203.3

2001 Gravel 166.9 60 5.2 1981.6

Sand 149.6 40 4.2 1520.0

Mud 211.2 17 3.5 415.2

*The mean water depth was very different between those two years, making the comparison problematic.

A total of 29,322 organisms representing 860 invertebrate taxa from 18 broad taxonomic 

groups were collected in benthic grab samples. Of the 860 invertebrate taxa, 538 were 

identified to the species level. Annelida was the dominant taxonomic group by abundance 

(65.7 percent) followed by Mollusca (11.3 percent), Echinodermata (7.5 percent) and 

Cnidaria (2.2 percent). Figure 9 depicts percent abundance of these groups and an “other” 

category comprised of 13 taxonomic groups combined that accounted for 13.2 percent of 

the total abundance.
19

Figure 9. Dominant taxa by percent abundance for benthic grab data. Data were combined for 2000, 

2001, 2003 and 2004.

The top 50 dominant taxa from all years are listed in Table 2. The dominant species across 

the sampling area, by both abundance and frequency of occurrence, was an annelid, the 

polychaete Galathowenia oculata, a member of Family Oweniidae, which occurred at 67

percent of the stations. The brittlestar Ophiura sarsii, an echinoderm, was the third 

dominant taxon by abundance and occurred at 40 percent of the stations sampled across 

the survey area. The bivalve mollusk Axinopsida serricata, was the ninth dominant taxon 

by abundance and occurred at 26 percent of the stations.
20

Table 2. Dominant taxa in 0.1m2 Smith McIntrye grab samples, 2000-2004.

Taxon

Mean 

Density 

(#/m2)

Percent 

Frequency Phylum Class Order Family

Galathowenia oculata 124.1 67.2 Annelida Polychaeta Oweniida Oweniidae

Spiophanes berkeleyorum 52.4 39.2 Annelida Polychaeta Spionida Spionidae

Ophiura sarsii 39.8 39.9 Echinodermata Ophiuroidea Ophiurida Ophiuridae

Pholoides asperus 33.5 45.7 Annelida Polychaeta Phyllodocida Pholoididae

Spiophanes bombyx 28.7 4.4 Annelida Polychaeta Spionida Spionidae

Sternaspis nr. fossor 18.7 24.2 Annelida Polychaeta Sternaspida Sternaspidae

Polycirrus sp. complex 13.1 30.4 Annelida Polychaeta Terebellida Terebellidae

Notoproctus pacificus 11.6 25.2 Annelida Polychaeta Capitellida Maldanidae

Axinopsida serricata 11.0 25.9 Mollusca Bivalvia Veneroida Thyasiridae

Amphipholis pugetana 9.6 17.7 Echinodermata Ophiuroidea Ophiurida Amphiuridae

Ampharete finmarchica 9.3 30.7 Annelida Polychaeta Terebellida Ampharetidae

Myriochele olgae 9.3 13.3 Annelida Polychaeta Oweniida Oweniidae

Idanthyrsus saxicavus 9.2 30.4 Annelida Polychaeta Terebellida Sabellariidae

Typosyllis heterochaeta 8.7 26.6 Annelida Polychaeta Phyllodocida Syllidae

Magelona longicornis 7.8 19.4 Annelida Polychaeta Spionida Magelonidae

Pista wui 7.8 27.6 Annelida Polychaeta Terebellida Terebellidae

Anthopleura artemisia 7.7 1.4 Cnidaria Anthozoa Actiniaria Actiniidae

Melinna elisabethae 7.7 27.6 Annelida Polychaeta Terebellida Ampharetidae

Glycera nana 7.4 47.8 Annelida Polychaeta Phyllodocida Glyceridae

Nicomache personata 7.4 13.6 Annelida Polychaeta Capitellida Maldanidae

Ischnochiton trifidus 6.8 31.4 Mollusca Polyplacophora Neoloricata Ischnochitonidae

Pectinaria californiensis 6.5 21.5 Annelida Polychaeta Terebellida Pectinariidae

Lepidozona mertensii 6.4 16.4 Mollusca Polyplacophora Neoloricata Ischnochitonidae

Sipuncula sp. Indet. 6.3 21.8 Sipuncula

Nynantheae sp. 6.2 3.7 Cnidaria Anthozoa Actiniaria
21

Taxon

Mean 

Density 

(#/m2)

Percent 

Frequency Phylum Class Order Family

Maldanidae sp. Indet. 5.8 23.5 Annelida Polychaeta Capitellida Maldanidae

Euclymeninae sp. Indet. 5.8 18.1 Annelida Polychaeta Capitellida Maldanidae

Petaloproctus sp. 5.8 6.8 Annelida Polychaeta Capitellida Maldanidae

Cirratulidae sp. Indet. 5.7 18.4 Annelida Polychaeta Spionida Cirratulidae

Dipolydora socialis 5.7 21.8 Annelida Polychaeta Spionida Spionidae

Rhodine bitorquata 5.6 28.3 Annelida Polychaeta Capitellida Maldanidae

Onuphis iridescens 5.5 28.3 Annelida Polychaeta Eunicida Onuphidae

Prionospio jubata 5.5 27.3 Annelida Polychaeta Spionida Spionidae

Thyasira flexuosa 5.5 26.6 Mollusca Bivalvia Veneroida Thyasiridae

Petaloproctus borealis 5.4 10.2 Annelida Polychaeta Capitellida Maldanidae

Asclerocheilus beringianus 5.1 15.7 Annelida Polychaeta Opheliida Scalibregmatid

Euclymeninae sp. 4.8 13.6 Annelida Polychaeta Capitellida Maldanidae

Maldane sarsi 4.8 14.3 Annelida Polychaeta Capitellida Maldanidae

Pista estevanica 4.7 24.6 Annelida Polychaeta Terebellida Terebellidae

Anobothrus gracilis 4.7 17.7 Annelida Polychaeta Terebellida Ampharetidae

Echiurus alaskanus 4.7 3.1 Echiura Echiurida Echiuroinea Echiuridae

Macoma carlottensis 4.6 12.6 Mollusca Bivalvia Veneroida Tellinidae

Nicomache sp. 4.6 9.9 Annelida Polychaeta Capitellida Maldanidae

Nemertinea sp. Indet. 4.6 23.5 Nemertea Nemertinea

Corella willmeriana 4.5 10.6 Urochordat Ascidiacea Phlebobranchiata Corellidae

Amphissa columbiana 4.5 20.5 Mollusca Gastropoda Neogastropoda Columbellidae

Ninoe gemmea 4.5 27.3 Annelida Polychaeta Eunicida Lumbrineridae

Decamastus nr. gracilis 4.4 8.9 Annelida Polychaeta Capitellida Capitellidae

Mediomastus sp. Indet. 4.3 20.1 Annelida Polychaeta Capitellida Capitellidae
22

Using benthic infaunal data from 2000, 2001, 2003, and 2004, spatial patterns in density 

(Figure 10) and H′ diversity (Figure 11) were visualized using inverse distance weighting, 

a GIS spatial interpolation method, within the survey area. Inverse distance weighting does 

not take into account the spatial structure of the sample points and results are influenced 

by the spacing and density of the sampling points. Given the geographic spread of the grab 

samples combined with the likely heterogeneity of the seabed, the reader is advised to 

assess interpolated values with caution. There is a general trend of decreasing density 

moving across the survey area from east to west, which corresponds to increasing distance 

from shore and increasing depth. Spatial patterns in H′ diversity appear to be more varied 

across the survey area and are likely associated with small-scale heterogeneity in bottom 

sediments, which can range from coarse gravel-sand to a much finer mud in this region. A 

lack of paired grain-size data for all stations precluded further assessment of these patterns,

so detailed analysis of relationships between benthic infauna and abiotic variables was 

limited to stations sampled in 2000 and 2001. Results from PCA on normalized abiotic 

data highlighted a distinct separation in stations by bottom type and indicated a slight 

increase in fine sediments with increasing water depth (Figure 12; Table 3).

Figure 10: Spatial interpolation of density within the survey area for benthic grabs. Darker colors indicate 

increasing density. Classification scale based on equal intervals. Derived from 2000, 2001, 2003, and 2004 

benthic grab data.
23

Figure 11: Spatial interpolation of H ́ diversity within the survey area for benthic grabs. Darker colors 

indicate increasing H ́ diversity. Derived from 2000, 2001, 2003, and 2004 benthic grab data.

Figure 12: Principal Components Analysis (PCA) on normalized abiotic data for 2000 and 2001 benthic grab 

stations.
24

Table 3. Summary of results of principal component analysis (PCA) on normalized abiotic data for 2000 

and 2001. Eigenvalues and percent of variation explained by the first 3 ordination axes are given. Linear 

coefficients (eigenvectors) of each PC are given for each abiotic variable.

PC1 PC2 PC3

Eigenvalues 2.54 1.4 0.9

percent of variation

li d

50.9 28.0 17.5

Eigenvectors

Gravel -0.198 0.802 0.001

Sand -0.444 -0.572 0.203

Silt 0.581 -0.142 -0.242

Clay 0.588 -0.061 -0.064

Water Depth 0.284 0.081 0.947

Results of non-metric multidimensional scaling of benthic invertebrate abundance derived 

from 2000 and 2001 benthic grabs are displayed in Figure 13. From this ordination plot it 

is clear that there is a separation in stations driven predominantly by grain size. Coarse, 

gravel bottoms have the highest benthic invertebrate diversity and richness, while mud

habitats have the lowest (Table 1). It is likely that water depth is also an important factor 

in species distribution; however, covariance in water depth by year (Table 1) made it 

impossible to evaluate depth or inter-annual variation in a meaningful way.

Figure 13: Ordination plot derived from non-metric multidimensional scaling (NMDS) of Bray-Curtis 

similarities calculated from square root transformed invertebrate abundance on un-aggregated 2000 and 

2000 benthic grab data.

Given the high levels of diversity found within the survey area and the large number of 

rare species, taxa were aggregated to taxonomic order to facilitate analysis of community 

spatial patterns. The non-metric multidimensional scaling based on species similarities 

generally separated stations into three groups, which were associated with dominant

bottom type: gravel, sand, and mud. The percent contribution of the most important orders
25

(i.e., those with percent cumulative contribution > 90 percent) responsible for these patterns 

are provided in Table 4 by dominant sediment type. While polychaete worms (i.e., orders 

Terebellida, Phyllodocida, Capitellida, Spionida, Oweniida, Eunicida) are dominant in all 

three sediment types, gravel bottom habitats are generally more diverse, with brittle stars a 

dominant order (Ophiurida) compared to mud habitats, where amphipods dominate. 

Polychaetes comprised over 50 percent of invertebrates in sand habitats.

Table 4. Results of the similarity percentage (SIMPER) one-way analysis among the three dominant 

sediment types for 2000 and 2001 benthic grab samples. Taxa aggregated to the order level.

Dominant Sediment Type Order

Percent

Contribution

Cumulative

Percent

Contribution

Gravel - average similarity 61 percent Terebellida 8.8 8.8

Phyllodocida 8.7 17.5

Capitellida 8.6 26.1

Ophiurida 7.5 33.6

Spionida 6.9 40.4

Amphipoda 6.0 46.5

Eunicida 5.1 51.6

Neoloricata 4.5 56.1

Sabellida 4.2 60.3

Oweniida 3.7 64.0

Decapoda 3.7 67.6

Cnidaria 2.9 70.5

Bryozoa 2.8 73.3

Nemertinea 2.8 76.1

Phlebobranchiata 2.5 78.7

Veneroida 2.4 81.1

Opheliida 2.2 83.3

Terebratulida 2.1 85.5

Porifera 1.8 87.3

Sipuncula 1.8 89.0

Neogastropoda 1.5 90.5

Sand - average similarity 55 percent Spionida 10.8 10.8

Oweniida 10.7 21.5

Phyllodocida 8.79 30.2

Capitellida 8.6 38.8

Amphipoda 8.2 47.0

Terebellida 7.8 54.8

Veneroida 7.1 61.9
26

Dominant Sediment Type Order

Percent

Contribution

Cumulative

Percent

Contribution

Eunicida 6.6 68.6

Ophiurida 5.8 74.4

Gadilida 2.7 77.1

Neogastropoda 2.4 79.5

Nemertinea 2.0 81.5

Sabellida 2.0 83.5

Decapoda 1.8 85.3

Sternaspida 1.8 87.1

Orbinida 1.6 88.7

Opheliida 1.5 90.2

Mud - average similarity 48 percent Amphipoda 11.2 11.2

Eunicida 10.5 21.7

Veneroida 9.9 31.6

Phyllodocida 8.7 40.3

Spionida 8.4 48.7

Gadilida 7.5 56.2

Terebellida 7.3 63.5

Spatangoida 6.1 69.6

Sternaspida 4.5 74.1

Oweniida 4.4 78.5

Opheliida 4.3 82.8

Ophiurida 3.3 86.1

Cumacea 3.1 89.2

Capitellida 2.4 91.6
27

Benthic Community on Cable Route - Video Transects

From video footage, epibenthic community data from paired (On Cable vs. adjacent 

Control) 50-m segments were analyzed for 14 transects surveyed in 2000, 2001, 2003, and 

2004 (Figure 6). All but one of the 14 transects were on the PC-1 East cable (the cable 

most recently installed prior to the first sampling, and thus more suitable for monitoring 

impact and recovery). For each transect and treatment (On Cable vs. Control), from six to 

22 segments were available for analysis in any given year, resulting in a total of 837 

segments (Table 5).
28

Table 5. Number of 50-m segments sampled showing associated sediment type (m=mud, s=sand, g=gravel) by transect as seen in Figure 6 treatment 

(Control/On), and year. Subtotals appear in the margins. 

2000 2001 2003 2004 Subtotals Sediment type

Transect Control On Control On Control On Control On

17-19 7m 7m 7m 7m 28 All mud

27-29 12m 4m, 

8s

12m 13m 11m 4m, 

8s

20m 18m 110 94 mud, 16 sand

31-33 10m 10g 5s, 

12g

11s, 

6g

54 10 mud, 16 sand, 28 gravel

34-36 11m 10m 9m 9m 16m 16m 71 All mud

40-42 2s, 4g 7s 3s, 

14g

18s 17s, 

5g

15s 5m, 

17g

17s, 

5g

129 5 mud, 79 sand, 45 gravel

43-45 10g 1m, 

9g

8g 8g 10g 10g 56 1 mud, 55 gravel

46-48 20s 19s 17s 16s, 

1g

73 72 sand, 1 gravel

49-51 3s, 9g 2s, 

10g

2s, 9g 4s, 

7g

12s 12s 70 35 sand, 35 gravel

52-54 10s 10s 8s 8s 36 All sand

55-57 8m 8m 7s 7s 30 16 mud, 14 sand

58-60 2s, 5g 4s, 

3g

7s 7s 28 20 sand, 8 gravel

79-81 1s, 7g 6s, 2g 3s, 7g 2s, 

8g

3s, 8g 11s, 

6g

58 26 sand, 32 gravel
29

85-87 11m, 

1g

3s, 

9m

12s 12s 48 20 mud, 27 sand, 1 gravel

88-90 12g 12g 11g 11g 46 All gravel

SUBTOTALS 36 36 110 111 106 100 170 168 837
30

A total of 204,689 epibenthic organisms, representing 82 invertebrate taxa from 17 broad 

taxonomic groups, were identified from the processed video recordings. Roughly half of 

total abundance was unidentified shrimp (Order Decapoda, 80,591 individuals) and brittle 

stars (Genus Ophiura, 26,628 individuals). Unidentified shrimp were present in 74 percent

of sampling units, with a mean density of 2.8 m-2 per segment (averaged over 837 

segments). In contrast, Ophiura brittle stars exhibited a high degree of patchiness, 

occurring in only 3.3 percent of segments (mean density per segment = 1 m-2). The 10 

dominant epibenthic taxa, in order of decreasing mean density and percent frequency of 

occurrence, are listed in Table 6.

Table 6. Abundance, mean density, and frequency of occurrence (percent of segments) of ten dominant 

taxa in order of decreasing mean density (a) and percent frequency of occurrence (b).

a

Taxon Group Total Abundance

Mean Density 

(# m-2)

Frequency 

(percent of 

segments)

Other Shrimp Shrimp 80591 2.77 73.8

Brittle Star - Ophiura Brittle Stars 26628 0.91 3.3

Munida Squat Lobster Squat Lobsters 17030 0.58 38.9

Strongylocentrotus Urchin (white) Urchins 12272 0.40 56.4

Encrusting White Sponge Sponges 7180 0.31 35.0

Brown Ball Sponge, Solitary Sphere Sponges 5931 0.25 52.6

Yellow Cloud Sponge >3cm Sponges 6184 0.23 48.7

White Cloud Sponge >3cm Sponges 5731 0.23 52.6

Allocentrotus Pink Urchin Urchins 5317 0.19 52.6

Branch Sponge Sponges 2635 0.11 7.8

b

Taxon Group Total Abundance

Mean Density 

(# m-2)

Frequency

(percent of 

segments)

Other Shrimp Shrimp 80591 2.77 73.8

Strongylocentrotus Urchin (white) Urchins 12272 0.40 56.4

Brown Ball Sponge, Solitary Sphere Sponges 5931 0.25 52.6

White Cloud Sponge >3cm Sponges 5731 0.23 52.6

Allocentrotus Pink Urchin Urchins 5317 0.19 52.6

Yellow Cloud Sponge >3cm Sponges 6184 0.23 48.7

White Cidarina-like snail Snails 1968 0.08 41.9

Munida Squat Lobster Squat Lobsters 17030 0.58 38.9

Encrusting White Sponge Sponges 7180 0.31 35.0

When aggregated to broad taxonomic group, unidentified shrimp were still the dominant 

group in terms of abundance, but sponges displaced brittle stars as the second most 

abundant group (Table 7). The brittle star group, which also includes Genus Ophiopholis

and other, non-commensal brittle stars, was the third dominant group in terms of 

abundance, but only occurred in 47 (~ 6 percent) of the 837 segments analyzed. Of these 

47 segments, 21 percent were in mud habitat, 47 percent were sand, and 32 percent were 

gravel. However, only 0.1 percent of brittle star abundance was in mud substrate; 61.8
31

percent of abundance was in sand, and 38.1 percent of abundance occurred in gravel 

habitat.

Table 7. Abundance, mean density, and frequency of occurrence (percent of segments) of ten dominant 

taxonomic groups in order of decreasing mean density (a) and percent frequency of occurrence (b).

a Group Total Abundance Mean Density 

(# m-2)

Frequency 

(percent of segments)

Shrimp 80887 2.78 75.3

Sponges 39253 1.59 74.3

Brittle Stars 26711 0.91 5.6

Squat Lobsters 18210 0.63 51.6

Urchins 17981 0.60 80.9

Corals 6608 0.25 28.9

Snails 6170 0.22 72.2

Bryozoans 3023 0.09 24.3

Hermit Crabs 1952 0.08 48.5

Anemones 1724 0.06 53.3

b Group Total AbundanceMean Density 

(# m-2)

Frequency

(percent of segments)

Urchins 17981 0.60 80.9

Shrimp 80887 2.78 75.3

Sponges 39253 1.59 74.3

Snails 6170 0.22 72.2

Sea Stars 1570 0.06 60.1

Anemones 1724 0.06 53.3

Squat Lobsters 18210 0.63 51.6

Hermit Crabs 1952 0.08 48.5

Corals 6608 0.25 28.9

Results of non-metric multidimensional scaling of mean invertebrate density from transect 

video, averaged over segments for each transect-treatment-year combination, are displayed 

in Figure 14. Most of the separation was between transects (and possibly years), while 

treatments (On Cable vs. Control) for the same transect and year tended to be similar. 

Vectors of habitat variables are superimposed on the plot and represent directions in the 

ordination space towards which the environmental vectors change most rapidly and to 

which they have maximal correlations with the ordination configuration (Oksanen et al.

2017). Lengths of arrows are proportional to correlation with the ordination; hence, 

P_MUD (the proportion of segments having mud habitat type for a given transecttreatment-year combination) was most highly correlated with the observed distribution of 

benthic fauna, followed by P_SAND, P_GRAVEL, DEPTH, and DISTANCE. For 

example, transects composed of all mud segments (i.e., 17-19, 34-36; Table 5) occur in the 

extreme upper left portion of the plot. Segments for transect 55-57 were either all mud (in 

2003) or all sand (2004); transect 85-87 was composed of all sand segments in 2004 and 

mostly mud in 2001; transect 40-42 comprised a mix of mostly sand or gravel segments,

but it was one of the shallower transects as well as the most distant (Figure 6). The apparent 

separation by year (the numbers within each symbol), with 2004 transects off to the upper 
32

right of the plot, can also be explained by habitat type. For example, for transect 55-57, 

2004 segments were all sand, while in 2003 they were all mud; for transect 85-87, the 2004 

transects were all sand, and the 2001 transects were mostly mud (Control 92 percent mud, 

On 75 percent mud). Similarly, transect 58-60 segments were all sand in 2004; those in 

2001 were a mix of sand and gravel (Control 71 percent gravel, On 43 percent gravel). 

These results suggest that habitat type (mud vs. sand or gravel) best explains the observed 

patterns, with lesser influences of depth and distance from shore. All of the environmental 

variables listed above except for distance from shore were significant (p<0.05) based on a 

permutation test (999 permutations) that fits environmental vectors having maximal 

correlation with the ordination (Oksanen et al. 2017).

Figure 14. Ordination plot derived from non-metric multidimensional scaling (NMDS) of Bray-Curtis 

dissimilarities calculated from square-root transformed mean invertebrate abundance based on analysis of 

video. Numbers inside symbols indicate year of sampling (0=2000, 1=2001, 3=2003, 4=2004). Vectors of 

environmental variables are superimposed on the plot (see text for detailed description).
33

Results of permutational analysis of variance using distance matrices, with Bray-Curtis 

dissimilarity as the distance measure, found no significant differences in invertebrate 

assemblages between Treatments (On Cable vs. Control). Furthermore, analysis of 

multivariate homogeneity of group dispersions, analogous to Levene’s test for 

homogeneity of variances in a multivariate setting, suggested that the variation within each 

group was similar (Figure 15). Taken together, the foregoing results do not suggest that

invertebrate assemblages differ significantly along the cable route (On) compared to 

reference (Control). In fact, it appears that differences were mainly due to environmental 

effects, principally habitat type.

Figure 15: Plot illustrating results of analysis of multivariate homogeneity of group dispersions (variances). 

Distances to centroid and 90percent confidence ellipses are shown for each of the two treatments (Control = 

triangle, On=circle).

A similar pattern emerged upon performing the ordination on individual transect segments, 

rather than pooled transects as in Figure 14. In this case, mud, sand, and gravel (Figure 16) 

represent averages of ordination scores for each level of the habitat factor (measured on

individual segments), while DEPTH and DISTANCE vectors are as described for Figure 

14. As noted above, segments for transects in all-mud habitat (17-19, 34-36) occur in the 
34

left portion of the ordination plot (extreme negative values for NMDS1, mostly positive 

values for NMDS2). Other differences due to habitat type, depth, or distance from shore 

that were noted previously still hold, although the large number of symbols (837 individual 

segments) in the plot make it a bit more challenging to read and interpret.

Figure 16. Results of non-metric multidimensional scaling ordination of individual transect segments. Symbol 

color corresponds to transect; symbol shape differentiates on-cable versus control. Environmental variables, 

either as habitat factor levels (mud, gravel, or sand) or vectors (depth, distance from shore), are superimposed 

on the plot.

Comparisons of number of taxa, Shannon H′ diversity, and log-transformed density among 

habitat types (Figure 17) also suggest differences among habitat types; all three metrics 

were significantly lower for mud habitat than for either sand or gravel. The greatest 

difference was between mud and gravel (and, to a lesser extent, mud and sand), although 

the difference between sand and gravel was also significant (Figure 17; all pair-wise 

comparisons significant, p < 0.01).
35

Figure 17. Box-and-whisker plots of number of taxa, Shannon H′ diversity, and log-transformed density by 

habitat type (m=mud; s=sand; g=gravel). Lower panel presents 95percent confidence intervals (Tukey) for 

pair-wise comparisons among the three habitat types (overall ANOVA p<0.001 for all three benthic 

metrics).

Because of the mix of different habitat types among segments within individual transectyear combinations as noted above, comparisons among transects, treatments, and years 

were also made separately for each habitat type (mud, sand, gravel). In each case, however, 

no significant difference between treatments (On Cable vs. Control) was found, and the 

results of analysis by habitat type were similar to the overall results described above.

Benthic Community on Cable Route - Suction Samples

Suction samples were analyzed for benthic invertebrates, both epibenthos and infauna, 

collected from paired treatments (On Cable vs. Control) at 14 transects in 2000, 2001, and 

2004. For each Transect-Treatment-Year combination, from one to seven replicates were 

collected and enumerated with respect to species composition.

A total of 12,975 organisms, representing 569 taxa, were identified in 139 replicate 

samples. Dominant taxa included arrow worms (Sagitta sp.), the polychaete Galathowenia 

oculata, the notched brittlestar Ophiura sarsii, the eualid shrimp Eualus pusiolus, and 
36

calanoid copepods (Calanoida sp. Indet.). Table 8 lists the 50 dominant taxa, which made 

up 72 percent of the total abundance. Measures of mean richness (# of taxa), diversity 

(Shannon H′), and density by transect, treatment, and year are listed in Table 9.
37

Table 8. List of 50 dominant taxa, in order of decreasing mean density, identified in 139 suction sample replicates collected in 2000, 2001, and 2004.

Species

Mean

Density 

(#/m2)

Frequency

(percent) Phylum Class Order Family

Sagitta sp. Indet. 114.5 53.2 Chaetognatha Sagittoidea Aphragmorpha Sagittidae

Galathowenia oculata 107.5 66.2 Annelida Polychaeta Oweniida Oweniidae

Calanoida sp. Indet. 35.5 47.5 Arthropoda Copepoda Calanoida

Ophiura sarsii 34.8 41.0 Echinodermata Ophiuroidea Ophiurida Ophiuridae

Thysanoessa spinifera 33.4 43.9 Arthropoda Malacostraca Euphausiacea Euphausiidae

Eualus pusiolus 30.9 41.0 Arthropoda Malacostraca Decapoda Hippolytidae

Spiophanes berkeleyorum 27.1 28.1 Annelida Polychaeta Spionida Spionidae

Pholoides asperus 18.8 36.7 Annelida Polychaeta Phyllodocida Pholoididae

Prionospio jubata 17.1 43.2 Annelida Polychaeta Spionida Spionidae

Tellina carpenteri 16.4 28.8 Mollusca Bivalvia Veneroida Tellinidae

Meterythrops robusta 13.2 25.9 Arthropoda Malacostraca Mysidacea Mysidae

Amphipholis pugetana 13.1 20.1 Echinodermata Ophiuroidea Ophiurida Amphiuridae

Ciona sp. Indet. 12.6 19.4 Urochordata Ascidiacea Phlebobranchiata Cionidae

Parathemisto pacifica 11.0 18.0 Arthropoda Malacostraca Amphipoda Hyperiidae

Axinopsida serricata 10.4 30.2 Mollusca Bivalvia Veneroida Thyasiridae

Sternaspis nr. fossor 9.9 25.9 Annelida Polychaeta Sternaspida Sternaspidae

Ischnochiton trifidus 9.2 41.7 Mollusca Polyplacophora Neoloricata Ischnochitonidae

Adontorhina cyclia 9.1 28.8 Mollusca Bivalvia Veneroida Thyasiridae

Amphissa columbiana 7.3 29.5 Mollusca Gastropoda Neogastropoda Columbellidae

Euclymeninae sp. Indet. 6.8 26.6 Annelida Polychaeta Capitellida Maldanidae

Bryozoa sp. Indet. 6.5 49.6 Bryozoa

Pacifacanthomysis nephrophthalma 6.4 10.8 Arthropoda Malacostraca Mysidacea Mysidae

Ampharete finmarchica 6.3 25.2 Annelida Polychaeta Terebellida Ampharetidae

Macoma sp. 6.1 17.3 Mollusca Bivalvia Veneroida Tellinidae

Ampelisca careyi 6.0 18.7 Arthropoda Malacostraca Amphipoda Ampeliscidae

Chaetozone sp. Indet. 6.0 16.5 Annelida Polychaeta Spionida Cirratulidae

Syrrhoe longifrons 5.1 17.3 Arthropoda Malacostraca Amphipoda Synopiidae

Lepidozona mertensii 5.0 17.3 Mollusca Polyplacophora Neoloricata Ischnochitonidae

Euphausia pacifica 4.7 7.2 Arthropoda Malacostraca Euphausiacea Euphausiidae

Cyclocardia ventricosa 4.6 23.7 Mollusca Bivalvia Veneroida Carditidae

Idanthyrsus saxicavus 4.6 21.6 Annelida Polychaeta Terebellida Sabellariidae
38

Species

Mean

Density 

(#/m2)

Frequency

(percent) Phylum Class Order Family

Cnidaria sp. Indet. 4.2 29.5 Cnidaria

Polycirrus sp. complex 4.2 23.0 Annelida Polychaeta Terebellida Terebellidae

Terebellidae sp. Indet. 4.2 12.9 Annelida Polychaeta Terebellida Terebellidae

Mediomastus sp. Indet. 4.1 20.9 Annelida Polychaeta Capitellida Capitellidae

Nuculana minuta 4.1 20.1 Mollusca Bivalvia Nuculoida Nuculanidae

Westwoodilla caecula 4.1 22.3 Arthropoda Malacostraca Amphipoda Oedicerotidae

Polycirrus californicus 4.0 20.9 Annelida Polychaeta Terebellida Terebellidae

Amphipholis squamata 3.8 9.4 Echinodermata Ophiuroidea Ophiurida Amphiuridae

Pulsellum salishorum 3.8 20.9 Mollusca Scaphopoda Gadilida Pulsellidae

Polynoidae sp. Indet. 3.7 20.9 Annelida Polychaeta Phyllodocida Polynoidae

Terebellides stroemi 3.7 20.9 Annelida Polychaeta Terebellida Trichobranchidae

Amphipholis sp. Indet. 3.7 13.7 Echinodermata Ophiuroidea Ophiurida Amphiuridae

Pista estevanica 3.7 24.5 Annelida Polychaeta Terebellida Terebellidae

Glycera nana 3.6 23.7 Annelida Polychaeta Phyllodocida Glyceridae

Macoma carlottensis 3.5 10.8 Mollusca Bivalvia Veneroida Tellinidae

Nutricola lordi 3.4 11.5 Mollusca Bivalvia Veneroida Veneridae

Polydora sp. 1 3.4 1.4 Annelida Polychaeta Spionida Spionidae

Cirratulidae sp. Indet. 3.4 23.0 Annelida Polychaeta Spionida Cirratulidae

Sipuncula sp. Indet. 3.4 16.5 Sipuncula
39

Table 9. Mean richness (taxa/sample), diversity (Shannon H′), and density (#/m2) of suction samples by 

transect, treatment, and year.

Transect Treatment Year Replicates

Mean Richness

(taxa/sample)

Mean 

Diversity

(H′)

Mean 

Density

(#/m2)

14-16 Control 2000 2 9.5 2.1 355

14-16 On 2000 4 11.3 2.1 485

17-19 Control 2000 4 15.3 2.8 888

17-19 On 2000 4 19.3 2.8 1688

27-29 Control 2000 2 19.5 3.7 385

27-29 On 2000 4 15.8 3.4 368

27-29 Control 2001 4 28.8 4.0 893

27-29 On 2001 4 25.3 3.9 838

27-29 Control 2004 2 23.5 4.2 605

27-29 On 2004 3 12.0 2.2 540

31-33 Control 2000 4 31.0 4.4 683

31-33 On 2000 4 15.8 3.8 228

34-36 Control 2000 4 19.0 3.5 518

34-36 On 2000 3 12.3 2.3 750

34-36 Control 2004 5 15.2 3.4 332

34-36 On 2004 5 16.0 2.9 498

40-42 Control 2000 4 25.5 2.3 1503

40-42 On 2000 6 15.3 3.1 428

40-42 Control 2001 4 40.3 4.7 985

40-42 On 2001 4 30.0 3.8 950

43-45 Control 2001 4 74.5 5.6 2140

43-45 On 2001 2 64.5 5.2 2050

46-48 Control 2001 4 55.3 5.3 1190

46-48 On 2001 2 29.5 4.2 520

49-51 Control 2001 4 17.5 3.5 423

49-51 On 2001 4 25.0 3.3 1608

52-54 Control 2001 4 45.3 3.8 2105

52-54 On 2001 2 63.0 4.5 2620

55-57 Control 2001 4 32.0 3.4 1388

55-57 On 2001 2 43.0 3.4 2430

55-57 Control 2004 2 37.5 3.8 1140

55-57 On 2004 5 27.2 4.3 508

58-60 Control 2001 2 38.0 4.2 1305

58-60 On 2001 2 35.0 4.8 585

79-81 Control 2001 4 51.8 5.1 1140

79-81 On 2001 4 28.3 3.7 1008

79-81 Control 2004 3 24.0 4.4 417

79-81 On 2004 3 20.3 3.6 390

85-87 Control 2001 2 40.0 4.8 1065

85-87 On 2001 4 27.8 3.9 998
40

Results of non-metric multidimensional scaling of invertebrate abundance by transect, 

treatment, and year (pooled replicate samples) derived from the suction sample data appear 

in Figure 17. Vectors of environmental variables (depth, distance from shore) fit to the 

ordination are superimposed as arrows on the plot. Depth was correlated significantly with 

the ordination configuration (p<0.05); distance from shore was not. Although sediment 

data were not available for these specific suction samples, the plot shares some features in 

common with ordinations performed previously with the video transect data (as in Figure 

13). For example, transects previously observed in the video data to have consisted of all 

or mostly mud segments (17-19, 34-36, 27-29) appear as before on the left side of the 

ordination plot (negative NMDS1). Sediment samples from transect 14-16, which was also 

the deepest site (326 m), were mostly mud (70 percent silt+clay). As before with the video 

data, permutational analysis of variance did not find any significant differences in 

assemblages between Treatments (On Cable vs. Control).

Figure 12. Ordination plot derived from non-metric multidimensional scaling (NMDS) of Bray-Curtis 

dissimilarities calculated from square-root transformed invertebrate abundance in suction samples. Numbers 
41

inside symbols indicate year of sampling (0=2000, 1=2001, 4=2004). Vectors of environmental variables 

(depth and distance) are superimposed on the plot.
42

Discussion

Cable Impacts

The data from the physical and biological observations in this study suggest that, in general,

the impacts from cable installation were limited in both scope and scale in all affected 

habitats, and that habitat recovery following the installation was fairly rapid, and that it 

varied by habitat type. The rate of recovery of benthic community composition could not 

be determined because it differed more by habitat type, transect location and year of 

sampling than by treatment (On or Off cable). Less impact was likely in the areas where 

complete burial was accomplished than in locations with exposed cable, where movement 

could cause persistent bottom disturbance.

Physical disturbance 

The persistence of visual evidence of the trench varied with location and depended on 

several natural factors, including type of seafloor substrate, in-fill rate of new material, and 

water movement (i.e., near-bottom currents or wave action). Where gravel dominated the 

substrate, habitat recovery from the physical disturbance of the sea plow was rapid, with 

no trench evident less than one year after installation. These tend to be areas with higher 

energy caused by waves and currents, which winnows finer sediments (Bornhold 2003) but 

facilitates in-filling of the trench by larger sediments. Where sand, mud, or clay dominated, 

a visible trench was discernible in places for more than three years after cable installation. 

Clay is more cohesive than sand or mud, and a sea plow reportedly can bury cable in clay 

substrate without leaving a deep trench (SEA 1999). Although a trench was noted in some 

areas of clay substrate in this study, a visible trench was more commonly evident in mud 

and sand than in clay. Because the supply of new sediment to the study area is scarce 

(Greene and Watt 2002), material filling a trench most likely comes from redistribution of 

local materials. Mud consists of finer grained particles than sand, and mud deposits 

typically indicate a lower energy seafloor environment than sand. Thus, one might expect 

mobile particles in a sand habitat to redistribute and fill a depression more quickly than in 

a mud dominated habitat. Curiously, the trench along PC-1 cable routes in OCNMS 

persisted longer in sand substrate than in mud or clay, suggesting fairly active redistribution 

of mud in the area. Along the PC-1 cable routes, areas do exist where mobile sands occur 

at water depths greater than 100 meters, as evidenced by large sand waves (Bornhold 

2003). Here, the cable trench could quickly be obscured, but surveys were not conducted 

in these high energy, sandy areas. 

By 2004 or more than 4.5 years after cable installations, a visible trench was not evident in 

surveyed areas regardless of substrate type. In general terms, the physical habitat within 

OCNMS had returned to pre-installation conditions within five years of cable installation. 

Some of the few published studies on submarine cable installation on seafloor habitat and 
43

biota focus on the Hibernia Atlantic fiber optic cable installed in 2000 in the western Gulf 

of Maine. The sea plow used for the Hibernia Atlantic installation had a larger disturbance 

footprint with its water-jetted plowshare and target burial depth of 1.5 m, resulting in a 

trench initially estimated at 3 m wide (Auster et al. 2013). The cable trench was noticeably

less prominent two years after installation (Grannis 2005), but it remained visible in places 

10 years after installation (although substrate type and other seafloor conditions were not 

specified where this was evident; Auster et al. 2013). Elsewhere, persistent alteration of 

seafloor substrate has been demonstrated where surface laid submarine cables traverse hard 

rock substrates (Kogan et al. 2003). 

Benthic Community

Benthic communities reported here are similar to an earlier study conducted in the 1960’s 

(Lie and Kisker, 1969) and in 2003 (Nelson et al. 2008). The northern portion of OCNMS 

supports a diverse assemblage of benthic communities, with sediment type being the 

primary abiotic factor controlling community composition. Annelid worms (primarily 

polychaetes) were the most abundant infauna and were broadly distributed across the study 

area and its various sediment types. Coarse, gravel sediments support a distinct infaunal 

community with the highest diversity and density. In comparison, there was a distinctly 

lower species diversity in mud habitats. On the sediment surface, roughly half of total 

abundance was accounted for by amphipods and brittle stars. Amphipods were abundant 

and widely distributed across sediment types. Brittle stars were more patchy in their 

distribution, predominantly associated with sand and gravel substrate and far less 

commonly found on mud. When both epibenthic and infaunal organisms are considered, 

annelid worms (mostly polychaetes) and bivalves (mostly clams) account for over 75

percent of total invertebrate abundance. 

In the context of impacts from undersea cables, benthic communities along the cable route 

in Olympic Coast National Marine Sanctuary were indistinguishable from those in control 

areas during the post-installation surveys. More precise sampling of fauna in sediments in 

the trench itself might have enabled a more highly resolved assessment, but logistical and 

safety issues precluded that. Even if it had been possible, it is likely that such sampling 

would have only confirmed the conclusion of a limited spatial impact of the cable 

installation.

Challenges of the Study Design and Conduct

Several aspects of data interpretation highlight the challenges of study design and research 

in deep, offshore areas. Two types of human-made disturbance occur in the study area. 

Plow burial of telecommunications cables is a single, but acute disturbance event. Bottom 

trawl fishing for groundfish typically occurs repeatedly over multiple years. Precise data 

were available for the cable installations, but data documenting historic and ongoing 

disturbance from bottom trawl fisheries were limited and spatially imprecise. As noted by 

Jennings et al. (2001) for New England waters, in the early 2000’s there were very few 

sources of data to quantify levels of trawling disturbance in U.S. waters on appropriate 
44

temporal and spatial scales, and few studies examined trawling effects across quantifiable 

gradients of disturbance, such as differing levels of bottom trawl frequency. This was the 

case for OCNMS. For example, the largest data set available was National Marine 

Fisheries Service (NMFS) fish blocks, 10 X 10 nautical mile squares in which non-tribal, 

commercial bottom trawl frequency numbers were lumped. Individual trawls typically 

were recorded as an event occurring within a designated fish block with no information on 

a specific location, trawl pathway or continuation into an adjacent fish block. In 

comparison, the cable installation disturbance occurred on a known date over narrow strips 

about 6 m wide along a defined route, and monitoring could focus along a cable corridor 

about 1 – 2 m wide. In essence, the study design for low and high fishing intensity would 

have to be based on a generalized sense of trawling intensity. Lacking were specific data 

on the number of times a trawl may have traversed a location along the cable route, and the 

timing of recent disturbance from trawl passes at that location. Recent trends in electronic 

monitoring of bottom trawl activity will significantly improve the precision in these data 

and enhance our ability to evaluate the impacts of trawl fisheries in the context of other 

seafloor disturbance activities. 

While trawling impacts could not be evaluated, trawling may have affected the data 

collected here. Even if we assume that the impact was similar at controls and treatment 

sites, the lack of a true control cannot be ignored. Therefore, it was not possible to evaluate 

the impact of disturbance from plow burial without the confounding factor of trawling 

disturbance. Here again, more precise data now collected for bottom trawling activity will 

improve the ability to identify control, or unimpacted sites, and to distinguish impacts from 

different disturbance activities. 

Statistical analysis was confounded by both the consistency and completeness of the 

available data set. The precision and resolution of seafloor substrate and habitat data for 

the study area were poor when this monitoring program began, making sample site 

selection difficult, sometimes erroneous, and leading to unbalanced sampling. Weather 

conditions and equipment problems sometimes prevented surveys of all planned transects, 

resulting in an incomplete data set for some years. This all affected the strength of statistical 

analyses and the ability to resolve differences among variables. 

Differences between transects and years also overwhelmed separation between treatments, 

which suggests that the distribution of invertebrate taxa was similar along the cable route 

(On) compared to reference (Off cable or Control). Differences in invertebrate community 

metrics between On-cable and Control were not statistically significant. In cases where 

the difference was significant, measures of abundance, richness, and diversity were as 

likely to be higher On-cable as for Control segments. Thus, there does not appear to be a 

consistent pattern in any of the calculated metrics with respect to On-cable vs. Control 

treatment comparisons.

Management Implications
45

Experienced project proponents and marine area managers alike recognize that operations 

on and under the water are challenging for many reasons, particularly construction or 

installation projects such as cable laying and scientific surveys at water depths in excess of 

100 meters. Numerous factors are at play, such as surface sea state, near-bottom currents, 

unexpected substrates and slopes encountered, and equipment malfunctions, any of which

can result in variances between planned and achieved results. In planning and 

environmental impacts assessment phases of construction projects, project proponents will 

likely have more technical knowledge of marine technology than scientists and marine area 

managers. To avoid differences in expectations, project proponents need to be realistic and 

transparent about what can be accomplished, and effectively communicate uncertainty with 

marine area managers. Marine area managers need to clearly articulate their concerns, 

recommendations to mitigate potential negative impacts, and terms or conditions of 

approvals or permits granted. All involved need to acknowledge potential for deviations 

from the ideal. Realistic expectations are best understood when supported by adequate 

information and evaluated by appropriate expertise. 

One challenge identified by this project is that marine area managers, typically with 

scientific, policy, and resource management experience, may not have technical expertise 

in subjects like marine construction or cable installation. Government agencies that 

manage marine areas may lack financial resources to contract for the appropriate expertise 

to assess potential project impacts, particularly in understudied environments such as deepsea environments. This discrepancy in technical knowledge can lead to unrealistic 

expectations or lack of alignment in expectations of project proponents and marine area 

managers. One solution is to have fees associated with permits that are adequate to support 

agency staff and contractor time associated with evaluation and processing of complex 

projects. In addition, fair market value charges for access to or use of public lands can 

support administrative, monitoring and other aspects of permit and project management. 

With the Pacific Crossing submarine cable project, one conclusion reached by NOAA is 

that more investment during the route planning phase could have improved both achieved 

cable burial and alignment of expectations between project proponents and marine area 

managers. Improved detail or higher resolution data collected for route planning surveys 

could have been more effective in identifying problem areas along PC-1 routes where 

achievement of target burial depth would be a challenge, such as slopes, highly mobile 

sediments, subsurface boulders, and dense or consolidated substrates that compromised 

PC-1 cable burial operations. Investment in data acquisition and analysis during route 

planning benefits all involved. In support of this, the permittee’s cable burial status report 

concluded that areas where the PC-1 cables were exposed and at risk from external 

aggression resulted largely from differences between pre-installation analysis and as-found 

substrate, the primary cause of ineffective cable burial (ERM 2002). From a marine area 

manager’s perspective, improved route planning also could serve to avoid areas of high 

ecological value and habitats most susceptible to physical disturbance. These include areas 

with high density of emergent biota or biogenic habitats (e.g., corals and sponges) that form 

essential fish habitat and hard substrates where more persistent impacts are anticipated. 
46

Unfortunately, availability of such ecological data along the PC-1 cable routes was also 

poor when project planning and installation occurred, and there was limited to no capacity 

to incorporate avoidance of ecologically valuable or vulnerable areas into route cable 

planning. Installation of PC-1 cables occurred when OCNMS was initiating its efforts to 

conduct seafloor mapping and habitat characterization within the sanctuary with modern 

acoustic and camera technologies. Now, nearly 2 decades later, OCNMS has acquired 

accurate bathymetry data and completed substrate and habitat characterization on a broad 

scale covering the sanctuary area. Although these bathymetry data can be considered high 

resolution (<1m accuracy), data for seafloor surface substrate composition and presence of 

biogenic habitats is more generalized and less precise. In particular, accurate identification 

of biogenic habitats requires visual confirmation, a process that is very time and resource 

consuming over a broad area. Whereas seafloor data available today would support more 

informed route planning than was possible in the late 1990’s, even currently available data 

would need to be supplemented with more detailed surveys along a construction route, for 

example to collect subsurface data to locate near-surface bedrock and bolder fields. 

As the information and experience base for a given topic grows, the ability to predict and 

assess impacts to natural resources is improved. In this case, there were no previous studies 

on the scale and persistence of seafloor impacts associated with sea plow installation of 

submarine cables. In addition, the project was located in deep marine waters where 

existing data were relatively sparse and environmental studies are challenging and costly 

to implement. With limited available information, managers needed to assess the scale and 

duration of natural resource impacts from this large construction project, which was 

accomplished through post-installation studies funded by the permittee along the PC-1 

cable routes. Without funding from Pacific Crossing that was required through the 

permitting process, it is unlikely these studies would have been completed. Of potential 

interest to both industry and marine area managers, this monitoring revealed that recovery 

of seafloor habitats and biological communities can be relatively quick, within months to 

a few years where soft or depositional substrates exist. Areas of hard substrate or emergent, 

slow-growing biogenic habitats are where impacts could be more severe and persistent. 

Thus, one finding from these studies is that areas susceptible to persistent post-installation 

impacts should be identified during the route planning phase and avoided during 

construction to the extent possible.

In the early 2000s, it was not common practice to conduct post-installation surveys to 

document achieved cable burial status. Of value to the cable owner, post-installation 

surveys can identify where cables are at risk from external aggression and where remedial 

actions could be considered. Presumably the cable owner would balance risk to cables 

with expense involved with a post-installation survey and remedial actions. However, in 

areas where user conflicts are clearly identified, such as where bottom contact fisheries are 

conducted, post-installation surveys funded by a project proponent may be necessary to 

identify where exposed cables put existing users, such as commercial fishers at risk of 

snagging gear or damaging submarine cables. Marine area managers have the 
47

responsibility to balance allowing installations and consideration of existing uses of the 

area. 

Throughout the permitting process and the negotiation of the reinstallation of the cable, 

OCNMS supported the Makah Tribe’s involvement as a way of fulfilling our treaty trust 

responsibility. The 1855 Treaty of Neah Bay with the Makah Indian Tribe, and subsequent 

legal interpretations of treaty language, governs the relationships between the federal 

government and the Makah Tribe. NOAA’s treaty trust responsibility includes the 

protection of treaty trust resources, tribal access to treaty resources and the sustainable 

implementation of treaty rights. In the case of permitting the installation of fiber optic 

cables, NOAA needed to ensure that the Makah’s access to their usual and accustomed 

fishing areas was not restricted.

With the PC-1 cables in OCNMS, post-installation monitoring of the seafloor addressed 

the question - can this type of human-caused disturbance be accommodated while 

conserving biological diversity within a national marine sanctuary? The documented 

recovery of seafloor habitat and biological community demonstrated in this study indicated

that single, temporary event disturbance of submarine cable installation can be tolerated 

where substrates are unconsolidated and, given the narrow footprint of a cable route, such 

disturbance could be consistent with long term protection of biological communities within 

marine protected areas. 
48

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pp.
52

Acknowledgements

Authors would like to acknowledge former Olympic Coast National Marine Sanctuary 

staff who contributed significantly to this work. Mary Sue Brancato and Ed Bowlby 

were the principal investigators who put substantial effort into planning, conduct, and 

preliminary data analysis for the surveys covered in this report. Katie Brenkman 

supported these surveys in numerous ways, particularly as lead for data management. 

Jennifer Bright completed numerous hours of post-survey video review for 

characterization of habitats and invertebrate observations. These studies were funded by 

the permittee, Pacific Crossing, Ltd. This report was improved significantly by 

suggestions provided by anonymous peer reviewers of the draft manuscript.
53

Glossary of acronyms

GIS Geographic Information System 

NMDS Non-metric multidimensional scaling 

NMFS National Marine Fisheries Service 

NMSA National Marine Sanctuaries Act

NOAA National Oceanic and Atmospheric Administration

OCNMS Olympic Coast National Marine Sanctuary

PCA Principal Components Analysis

PCL Pacific Crossing, Ltd.

PC-1 Pacific Crossing-1 

ROV Remotely Operated Vehicle

SEA Supplemental Environmental Assessment

SIMPER Similarity Percentage

Tyco Tyco Submarine Systems, Ltd.
54

Appendices

Appendix A. Olympic Coast National Marine Sanctuary station information and summary of key benthic 

community characteristics for 0.1m2 Smith McIntyre grab samples, 2000-2004.

Station Latitude 

(DD)

Longitude 

(DD) Year

Water 

Depth 

(m)

Num. 

of 

Reps

Mean 

Richness 

(#taxa/grab)

Mean 

Diversity 

(H ́/grab)

Mean 

Density 

(#/m2)

BCS5 48.2502 -124.8801 2000 205 5 33.8 3.0 2790.0

HFI1 48.3969 -125.1614 2000 558 3 35.3 4.6 646.7

HFI2 48.3840 -125.1743 2000 594 3 30.0 4.3 896.7

HFI3 48.3770 -125.1965 2000 579 3 9.7 2.9 140.0

HFI4 48.3650 -125.1692 2000 588 3 19.7 4.1 310.0

HFI5 48.3612 -125.2136 2000 594 3 10.3 3.2 136.7

HM01 48.4233 -124.6433 2000 438 4 25.5 4.3 537.5

HM02 48.4323 -124.6929 2000 378 4 26.8 2.8 1207.5

HM03 48.4496 -124.7772 2000 871 3 39.0 4.7 1046.7

HM04 48.4487 -124.7772 2000 867 3 11.0 1.7 1416.7

HM05 48.4470 -124.7956 2000 1000 3 33.7 4.0 1273.3

HM06 48.4324 -124.8688 2000 938 3 11.3 1.9 980.0

HM12 48.4083 -124.9583 2000 885 4 29.3 4.5 742.5

HM13 48.3981 -124.9652 2000 730 4 25.0 4.4 407.5

HM14 48.3903 -124.9920 2000 941 3 22.3 2.4 2143.3

HM15 48.3942 -125.0510 2000 359 3 29.3 4.5 483.3

HM16 48.3986 -125.0852 2000 376 3 44.7 5.2 863.3

HM17 48.3851 -125.1170 2000 366 3 24.0 3.8 730.0

HM18 48.3822 -125.1588 2000 404 3 34.0 4.7 560.0

HM19 48.3755 -125.1635 2000 450 3 28.7 4.4 496.7

HM20 48.3768 -125.1832 2000 560 3 22.0 4.1 376.7

HM21 48.3790 -125.2577 2000 423 3 35.0 4.9 526.7

HM22 48.3581 -125.2882 2000 459 3 31.7 4.5 626.7

HM23 48.3616 -125.2949 2000 380 3 29.7 4.5 586.7

HM24 48.3446 -125.3412 2000 377 3 24.3 4.1 476.7

HM25 48.2502 -124.9430 2000 602 3 29.7 3.8 1140.0

HM26 48.2703 -124.9400 2000 632 3 29.0 3.4 1646.7

HM27 48.2693 -124.9456 2000 641 3 35.3 3.5 1826.7

HM28 48.2712 -124.9699 2000 632 3 33.3 4.6 633.3

HM29 48.3250 -124.8848 2000 555 3 23.0 3.5 843.3

HM30 48.3252 -124.8714 2000 497 3 34.7 4.0 1676.7

HM41 48.2505 -124.9411 2000 600 1 24.0 3.7 990.0

HM43 48.2524 -125.0432 2000 858 1 13.0 2.8 510.0
55

Station Latitude 

(DD)

Longitude 

(DD) Year

Water 

Depth 

(m)

Num. 

of 

Reps

Mean 

Richness 

(#taxa/grab)

Mean 

Diversity 

(H ́/grab)

Mean 

Density 

(#/m2)

HM44 48.2496 -125.0920 2000 376 1 26.0 4.7 360.0

HM45 48.2502 -125.1412 2000 382 1 40.0 5.0 700.0

HM46 48.2502 -125.1879 2000 450 1 40.0 5.0 700.0

HM47 48.2502 -125.2377 2000 550 1 32.0 4.4 660.0

HM60 48.3886 -125.1212 2000 373 1 29.0 4.0 880.0

HM61 48.3588 -125.2887 2000 452 1 46.0 5.2 870.0

HM62 48.3603 -125.2665 2000 597 1 5.0 2.2 90.0

HM63 48.3630 -125.2335 2000 594 1 9.0 3.1 140.0

LFI1 48.4358 -124.7210 2000 588 3 30.3 4.4 623.3

LFI2 48.3942 -125.0751 2000 367 3 41.7 4.9 956.7

LFI3 48.3776 -125.1214 2000 379 3 34.3 4.3 883.3

LFI4 48.3476 -125.3359 2000 376 3 36.7 4.6 763.3

LFI5 48.4111 -124.9382 2000 802 3 29.7 4.0 923.3

MFI1 48.3975 -125.0065 2000 950 1 30.0 3.0 2200.0

MFI2 48.3687 -124.9621 2000 370 3 46.7 5.0 1090.0

MFI3 48.3680 -124.9540 2000 383 3 16.7 2.8 800.0

MFI5 48.4435 -124.8111 2000 1035 3 24.0 3.3 1140.0

HFI101 48.3762 -125.2333 2001 185 3 11.7 3.3 176.7

HFI102 48.4020 -125.0480 2001 111 3 19.0 4.1 290.0

HFI103 48.3875 -125.2452 2001 172 3 42.3 4.5 1023.3

HFI104 48.3555 -125.2497 2001 180 3 9.3 3.0 116.7

HFI105 48.3740 -125.2025 2001 178 3 13.3 3.6 186.7

HFI106 48.4040 -125.0177 2001 226 3 28.7 4.2 713.3

HFI107 48.3607 -125.2030 2001 178 3 17.7 4.0 260.0

HFI108 48.3680 -125.2105 2001 179 3 11.7 3.3 163.3

HM105 48.4468 -124.7507 2001 243 1 94.0 6.1 6060.0

HM107 48.4428 -124.7993 2001 306 1 31.0 1.9 4880.0

HM108 48.4443 -124.8147 2001 319 1 69.0 5.4 2370.0

HM109 48.4310 -124.8410 2001 334 3 39.0 4.4 1220.0

HM111 48.4277 -124.9280 2001 256 1 40.0 3.6 1790.0

HM112 48.4000 -124.9335 2001 224 3 25.0 3.4 786.7

HM113 48.4250 -124.9413 2001 257 1 25.0 3.5 700.0

HM114 48.4223 -124.9552 2001 260 1 14.0 2.9 400.0

HM115 48.4088 -124.9607 2001 276 1 10.0 2.7 380.0

HM116 48.4038 -124.9623 2001 246 1 42.0 5.0 1830.0

HM117 48.3913 -124.9748 2001 190 3 62.7 5.6 1796.7

HM118 48.3878 -124.9910 2001 279 3 16.7 3.4 560.0

HM119 48.4002 -125.0792 2001 113 3 45.0 5.1 940.0
56

Station Latitude 

(DD)

Longitude 

(DD) Year

Water 

Depth 

(m)

Num. 

of 

Reps

Mean 

Richness 

(#taxa/grab)

Mean 

Diversity 

(H ́/grab)

Mean 

Density 

(#/m2)

HM120 48.3835 -125.0830 2001 115 1 67.0 5.8 1810.0

HM121 48.3762 -125.1013 2001 118 3 45.0 5.0 933.3

HM122 48.3762 -125.1255 2001 118 3 39.3 3.2 1870.0

HM123 48.3812 -125.1638 2001 147 1 53.0 5.5 810.0

HM124 48.3298 -124.7497 2001 43 1 37.0 4.4 1610.0

HM125 48.3483 -124.7608 2001 64 1 41.0 3.1 3920.0

HM126 48.3703 -124.7698 2001 81 1 68.0 5.1 2820.0

HM127 48.2903 -124.8905 2001 117 3 30.7 3.8 1366.7

HM128 48.2992 -124.9428 2001 227 3 43.7 4.1 1440.0

HM129 48.3802 -125.1520 2001 116 1 54.0 5.5 1100.0

HM130 48.3995 -125.2103 2001 178 1 9.0 3.1 100.0

HM131 48.3405 -125.2090 2001 182 1 16.0 4.0 200.0

HM132 48.3577 -125.3097 2001 118 1 61.0 5.5 1230.0

HM133 48.4021 -124.8688 2001 340 1 31.0 3.6 1520.0

HM134 48.3702 -124.8895 2001 337 3 30.3 3.5 1273.3

HM135 48.5009 -124.9131 2001 81 1 67.0 5.6 1720.0

HM136 48.4805 -124.9796 2001 95 1 60.0 3.6 2730.0

HM137 48.4502 -125.0606 2001 176 3 29.0 3.4 1696.7

HM138 48.4198 -125.0988 2001 107 1 26.0 3.8 540.0

HM139 48.3201 -125.1207 2001 113 3 58.7 5.2 1510.0

HM140 48.3172 -125.2301 2001 184 1 15.0 3.8 190.0

HM141 48.3140 -125.3263 2001 105 1 36.0 5.0 620.0

HM142 48.3195 -125.0416 2001 202 1 21.0 3.7 380.0

HM145 48.4360 -124.7137 2001 165 1 67.0 5.6 1760.0

HM146 48.4328 -124.6997 2001 132 1 88.0 5.7 3560.0

HM148 48.4277 -124.6743 2001 132 1 92.0 5.8 4540.0

HM149 48.4250 -124.6617 2001 132 1 57.0 5.3 2070.0

HM150 48.4232 -124.6513 2001 124 1 81.0 5.8 2460.0

HM151 48.3332 -125.3283 2001 113 1 21.0 3.8 490.0

HM152 48.3510 -125.3287 2001 117 1 25.0 4.4 400.0

HM155 48.3285 -124.7863 2001 40 1 36.0 4.6 1260.0

HM156 48.3503 -124.7837 2001 50 1 28.0 3.4 1470.0

HM157 48.3513 -124.8247 2001 69 1 49.0 5.3 1940.0

HM158 48.3817 -124.9718 2001 109 1 68.0 5.1 2440.0

HM159 48.4700 -124.9139 2001 155 1 42.0 4.7 1030.0

HM160 48.4659 -125.0327 2001 113 1 57.0 5.1 1380.0

HM161 48.4454 -125.0642 2001 184 1 28.0 3.3 1610.0

HM162 48.3988 -125.1068 2001 108 1 62.0 5.0 1850.0
57

Station Latitude 

(DD)

Longitude 

(DD) Year

Water 

Depth 

(m)

Num. 

of 

Reps

Mean 

Richness 

(#taxa/grab)

Mean 

Diversity 

(H ́/grab)

Mean 

Density 

(#/m2)

HM163 48.3506 -125.1237 2001 163 1 41.0 4.2 1110.0

HM164 48.3448 -125.1624 2001 152 1 43.0 5.0 890.0

HM165 48.3589 -125.0014 2001 115 1 74.0 5.8 1640.0

CH8 48.3480 -125.2954 2003 122 4 41.8 5.0 882.5

CL5 48.3817 -125.1271 2003 116 3 48.0 5.3 826.7

FH6 48.3550 -125.2815 2003 165 4 44.0 5.0 907.5

FH7 48.3744 -125.2225 2003 182 4 8.0 2.6 120.0

FH8 48.3832 -125.2149 2003 182 4 13.0 3.5 205.0

FH9 48.3725 -125.2184 2003 182 4 12.8 3.4 185.0

SF1 48.4196 -124.6820 2003 87 2 64.0 5.8 1260.0

OC04001 48.2452 -125.0100 2004 215 3 69.3 5.2 2130.0

OC04003 48.1470 -124.9955 2004 270 3 38.7 4.8 686.7

OC04004 48.1274 -125.0618 2004 144 3 74.7 5.6 2156.7

OC04005 48.1116 -125.1416 2004 208 3 16.0 3.7 300.0

OC04011 47.2983 -124.7850 2004 271 3 24.7 4.3 396.7

OC04013 48.1090 -125.0630 2004 167 3 55.7 5.3 1253.3

CH1 48.3814 -125.2659 2004 123 1 48.0 5.4 840.0

CH10 48.3915 -125.0379 2004 121 3 30.7 4.2 873.3

CH3 48.3897 -125.0222 2004 206 1 47.0 5.4 850.0

CL7 48.3683 -125.1412 2004 115 2 40.0 5.2 695.0

FH2 48.3698 -125.2475 2004 184 2 14.0 3.5 295.0

FH3 48.3819 -125.1847 2004 172 2 19.0 3.9 380.0

FL1 48.3929 -125.1297 2004 116 3 26.7 4.7 413.3
58

Appendix B. Olympic Coast National Marine Sanctuary grain-size characteristics for 0.1m2 Smith McIntrye 

grab samples, 2000-2001.

Station Gravel 

(percent)

Sand (percent) Silt (percent) Clay (percent) Mud (Silt+Clay)

(percent)

BCS5 0.3 93.9 6.1 0.3 6.4

HFI1 44.2 32.2 17.1 6.6 23.7

HFI2 0.4 23.0 49.3 27.9 77.2

HFI3 0.5 5.5 58.5 35.5 94.0

HFI4 35.4 43.4 9.9 11.1 21.0

HFI5 0.5 4.0 74.8 20.7 95.5

HM01 63.6 30.7 4.3 1.3 5.6

HM02 70.9 19.0 9.4 1.2 10.6

HM03 17.3 18.5 31.5 32.4 63.9

HM04 4.9 43.5 35.8 15.1 50.9

HM05 0.3 53.2 39.2 8.0 47.2

HM06 0.3 85.1 7.6 7.7 15.3

HM12 16.8 36.9 32.4 13.8 46.2

HM13 77.0 9.6 10.5 2.5 13.0

HM14 0.5 82.7 11.5 5.9 17.4

HM15 53.2 31.5 10.3 4.7 15.0

HM16 44.1 40.2 10.4 5.2 15.6

HM17 0.3 94.2 3.0 2.8 5.8

HM18 44.0 32.6 13.8 8.8 22.6

HM19 17.0 50.6 19.4 13.0 32.4

HM20 0.4 19.7 60.0 20.0 80.0

HM21 61.2 23.7 5.4 9.3 14.7

HM22 37.1 19.1 26.6 17.3 43.9

HM23 45.4 34.3 9.1 11.1 20.2

HM24 1.6 94.5 1.0 2.8 3.8

HM25 0.4 23.6 63.1 13.8 76.9

HM26 0.4 36.8 51.1 12.1 63.2

HM27 0.4 46.8 41.3 11.2 52.5

HM28 63.4 18.7 14.1 4.2 18.3

HM29 80.7 13.3 6.2 0.4 6.6

HM30 0.5 42.5 47.8 9.8 57.6

HM41 0.4 21.4 66.2 13.6 79.8

HM43 0.3 6.8 76 16.6 92.6

HM44 52.4 30.3 9.4 8.2 17.6

HM45 60.9 21.3 9.5 8.3 17.8

HM46 43.6 27.8 18.3 10.6 28.9

HM47 0.3 69.7 18.4 11.6 30.0
59

Station Gravel 

(percent)

Sand (percent) Silt (percent) Clay (percent) Mud (Silt+Clay)

(percent)

HM60 0.3 95.1 3.9 1.3 5.2

HM61 37.6 34.6 18.3 9.6 27.9

HM62 3.2 9.7 64.6 22.7 87.3

HM63 0.5 9.1 59.5 30.9 90.4

LFI1 59.8 31.1 7.1 2.1 9.2

LFI2 49.3 39.7 5.9 5.4 11.3

LFI3 0.6 95.6 2.0 2.0 4.0

LFI4 80.8 14.8 3.8 1.1 4.9

LFI5 0.4 53.7 34.9 10.5 45.4

MFI1 1.6 75.4 17.2 6.0 23.2

MFI2 27.7 40.1 25.2 6.8 32.0

MFI3 1.8 63.7 24.4 10.4 34.8

MFI5 11.1 35.4 28.2 25.5 53.7

HFI101 0.3 6.2 74.0 20.1 94.1

HFI102 63.1 17.9 12.2 7.0 19.2

HFI103 14.8 73.0 7.0 5.2 12.2

HFI104 2.6 7.1 66.5 24.8 91.3

HFI105 0.3 6.8 74.0 18.4 92.4

HFI106 0.4 54.8 34.9 9.9 44.8

HFI107 0.3 19.2 60.6 20.7 81.3

HFI108 0.5 6.8 73.0 20.7 93.7

HM105 55.4 28.8 12.0 3.9 15.9

HM107 2.9 87.9 6.6 2.3 8.9

HM108 41.7 49.0 8.0 1.9 9.9

HM109 4.1 43.8 37.7 14.8 52.5

HM111 0.3 82.9 12.1 4.4 16.5

HM112 0.4 58.5 31.2 10.8 42.0

HM113 48.4 28.8 18.2 5.0 23.2

HM114 0.3 51.4 31.3 16.8 48.1

HM115 6.7 36.8 42.5 14.1 56.6

HM116 61.7 20.7 14.8 2.9 17.7

HM117 44.9 28.1 18.2 8.8 27.0

HM118 0.3 82.7 12.0 5.8 17.8

HM119 0.5 86.9 8.4 4.9 13.3

HM120 29.8 60.4 6.7 3.9 10.6

HM121 18.0 60.3 14.9 7.1 22.0

HM122 0.3 94.2 4.2 2.1 6.3

HM123 33.6 48.2 11.5 6.3 17.8

HM124 0.3 93.3 5.8 1.6 7.4
60

Station Gravel 

(percent)

Sand (percent) Silt (percent) Clay (percent) Mud (Silt+Clay)

(percent)

HM125 0.5 49.3 44.0 6.9 50.9

HM126 17.0 66 13.5 3.0 16.5

HM127 0.3 69.5 24.2 6.3 30.5

HM128 45.1 37.4 14.0 1.1 15.1

HM129 23.4 60.7 9.0 7.5 16.5

HM130 0.3 4.9 70.0 25.1 95.1

HM131 0.7 6.5 72.0 21.2 93.2

HM132 51.4 30.0 11.1 8.0 19.1

HM133 0.8 23.2 57.7 19.3 77.0

HM134 3.0 20.6 62.6 15.0 77.6

HM135 52.7 29 14.2 4.5 18.7

HM136 19.3 62.6 13.8 4.1 17.9

HM137 3.2 85.3 8.7 3.3 12.0

HM138 0.3 91.1 6.5 2.0 8.5

HM139 57.6 19.9 12.5 9.4 21.9

HM140 0.3 6.2 71.0 23.9 94.9

HM141 28.8 38.2 20.0 13.6 33.6

HM142 0.3 18.1 61.0 20.6 81.6

HM145 62.9 28.9 7.3 1.4 8.7

HM146 36.0 42.1 18.2 3.6 21.8

HM148 40.8 36.5 19.6 3.2 22.8

HM149 44.8 40.2 12.3 3.1 15.4

HM150 38.4 49.6 8.1 3.4 11.5

HM151 0.6 97.0 2.4 0.3 2.7

HM152 0.6 93.6 5.3 0.8 6.1

HM155 0.3 92.3 7.4 0.9 8.3

HM156 0.3 93.3 5.6 1.5 7.1

HM157 0.7 79.5 17.7 2.4 20.1

HM158 11.1 53.0 28.0 8.5 36.5

HM159 8.2 83.0 7.5 1.2 8.7

HM160 41.1 37.5 17.2 4.4 21.6

HM161 0.3 82.0 17.6 0.4 18.0

HM162 0.3 96.6 2.7 0.4 3.1

HM163 6.8 87.7 5.6 0.4 6.0

HM164 53.6 31.3 11.6 3.8 15.4

HM165 40.0 35.0 17.5 7.5 25.0