SIUSLAW RIVER, OREGON, 

OCEAN DREDGED MATERIAL DISPOSAL 

SITE DESIGNATION

BIOLOGICAL ASSESSMENT

FOR LISTED SPECIES INCLUDING COHO SALMON, CHINOOK 

SALMON, GREEN STURGEON, PACIFIC EULACHON,

MARINE MAMMALS, MARINE BIRDS, TERRESTRIAL BIRDS, 

INVERTEBRATES AND PLANTS

ESSENTIAL FISH HABITAT ASSESSMENT

FOR GROUNDFISH, COASTAL PELAGIC, 

AND SALMONID SPECIES

PREPARED BY

U.S. ENVIRONMENTAL PROTECTION AGENCY

REGION 10, SEATTLE, WASHINGTON

July 2009
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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TABLE OF CONTENTS

BIOLOGICAL ASSESSMENT.................................................................................................................... 1

INTRODUCTION...................................................................................................................................... 1

PROPOSED ACTION................................................................................................................................ 4

History of Ocean Disposal Sites ....................................................................................................... 4

ENVIRONMENTAL BASELINE................................................................................................................. 7

Physical Characteristics .................................................................................................................... 7

Overview of Aquatic Resources...................................................................................................... 11

ESA-Listed Species Status and Occurrence in the Vicinity of the Proposed Siuslaw Ocean 

Disposal Sites.................................................................................................................................. 22

ASSESSMENT OF EFFECTS ................................................................................................................... 27

Coho Salmon................................................................................................................................... 28

Chinook Salmon.............................................................................................................................. 29

Green Sturgeon ............................................................................................................................... 29

Pacific Eulachon ............................................................................................................................. 30

Marine Mammals............................................................................................................................ 30

Coastal Birds................................................................................................................................... 30

Cumulative Effects.......................................................................................................................... 31

Determination for ESA-Listed Species and Designated Critical Habitat ....................................... 31

ESSENTIAL FISH HABITAT ASSESSMENT............................................................................................. 33

Potential Effects of the Proposed Action on EFH........................................................................... 35

Determination for Essential Fish Habitat........................................................................................ 38

LITERATURE CITED ............................................................................................................................. 39

LIST OF TABLES

Table 1. ESA-listed Fish, Marine Mammals, Marine Turtles, Marine Birds, and Terrestrial Bird, 

Invertebrate and Plant Species that may occur in the Action Area............................................... 3

Table 2. Siuslaw River Project Dredging Volumes............................................................................. 6

Table 3. Dominant Benthic Invertebrate Fauna by Station, August 2008 ......................................... 11

Table 4. Dominant Benthic Invertebrate Fauna by Station, September 2008.................................... 13

Table 5. August 2008 Trawl Data, Siuslaw ODMDS........................................................................ 18

Table 6. September 2008 Trawl Data, Siuslaw ODMDS .................................................................. 20

Table 7. Species with Designated EFH Offshore from the Siuslaw River as Provided by NMFS.... 34

LIST OF FIGURES

Figure 1. Proposed Siuslaw River North and South Ocean Disposal Sites.......................................... 2

Figure 2. Historical Siuslaw River Ocean Disposal Sites.................................................................... 5

Figure 3. Siuslaw River ODMDS Sampling Locations, 2008 ........................................................... 10

Figure 4. 2008 Densities of Benthic Invertebrates, Siuslaw ODMDS............................................... 14

Figure 5. 2008 Diversity of Benthic Invertebrates (H’), Siuslaw ODMDS....................................... 15

Figure 6. 2008 Diversity of Benthic Invertebrates (SDV), Siuslaw ODMDS ................................... 15

Figure 7. 2008 Species Richness of Benthic Invertebrates, Siuslaw ODMDS.................................. 16
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS 

Designation

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BIOLOGICAL ASSESSMENT

INTRODUCTION

The U.S. Environmental Protection Agency (EPA) is proposing final designation under the Marine 

Protection, Research and Sanctuaries Act of 1972, as amended, 33 U.S.C. §§ 1401 to 1445, 

(MPRSA), for the two proposed ocean dredged material disposal sites (ODMDS). These sites are

located approximately 1 mile offshore of the entrance to the Siuslaw River on the central Oregon 

Coast (Figure 1). The proposed North site is 4,800 feet by 2,000 feet with an average depth of 90 

feet, and the South site is 3,000 feet by 2,000 feet with an average depth of 78 feet.

The primary anticipated user of the proposed Siuslaw North and South ocean disposal sites is the 

U.S. Army Corps of Engineers (USACE), who anticipates using the site for disposal of dredged 

material from the federally authorized Siuslaw River navigation project. Persons or entities who 

want to use the proposed sites for disposal of suitable dredged material must seek a permit, or in 

the case of the USACE, meet the substantive requirements for a permit, including EPA 

concurrence, before the proposed ocean disposal sites may be used. The EPA’s proposed site 

designation does not authorize any disposal activity.

In March 2009, the list of federally listed species that may occur in the Siuslaw River coastal area

(Lane County, Oregon) was obtained from the National Marine Fisheries Service (NMFS) by mail 

and from the U.S. Fish and Wildlife Service (USFWS) website. This Biological Assessment (BA) 

is being prepared pursuant to Section 7(c) of the Endangered Species Act of 1973 (ESA), as 

amended, 16 U.S.C. §§ 1531 to 1544 to evaluate the effects of designation of the proposed ocean 

disposal sites on the federally listed fish, marine mammals, marine turtles, coastal birds, and 

terrestrial bird, invertebrate and plant species that may occur in the Siuslaw River action area 

(Table 1).

Under the ESA, “action area” means all areas to be affected directly or indirectly by the federal 

action and not merely the immediate area involved in the action (50 CFR §402.02). Indirect effects 

are those effects that are caused by or will result from the proposed action and are later in time, but 

are still reasonably certain to occur (50 CFR §402.02). For this BA, the action area for the Siuslaw 

coastal area includes the two ocean disposal sites, the water column within the disposal sites, and 

an area 200 feet in every direction from the boundaries of the disposal sites (see Figure 1). 

Disposal of material at the two proposed ocean disposal sites is an indirect effect of site designation 

and the most likely environmental impacts of disposal (turbidity, physical disturbance, and benthic 

effects) would generally be limited to this action area.

Effects to essential fish habitat (EFH) are being assessed in that attached Essential Fish Habitat 

Assessment, pursuant to the Magnuson-Stevens Fishery Conservation and Management Act (Public 

Law 94-265), as amended by the Magnuson-Stevens Fishery Conservation and Management 

Reauthorization Act (MSA) of 2006 (P.L. 109-479). The species that have designated EFH in the 

vicinity of the proposed Siuslaw North and South ocean disposal sites include five coastal pelagic 

species, numerous groundfish species, and coho and Chinook salmon. The same general concept 

as described for the ESA “action area” is used for the EFH Assessment.
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Figure 1. Proposed Siuslaw River North and South Ocean Disposal Sites
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Table 1. ESA-listed Fish, Marine Mammals, Marine Birds, and Terrestrial Bird, Invertebrate and 

Plant Species that may occur in the Action Area

Species Status Federal Register (FR)

Listing Critical Habitat

OC Coho Salmon

Oncorhynchus kisutch Threatened 73 FR 7816; 2/11/2008 73 FR 7816; 2/11/2008

SONCC Coho Salmon

Oncorhynchus kisutch Threatened 70 FR 37160; 6/28/2005 64 FR 24049; 5/5/1999

Lower Columbia River Coho Salmon

Oncorhynchus kisutch Threatened 70 FR 37160; 6/28/2005 Not applicable

Lower Columbia River Chinook

Oncorhynchus tshawytscha Threatened 70 FR 37160; 6/28/2005 70 FR 52630; 9/2/2005

Upper Willamette River spring run 

Chinook Oncorhynchus tshawytscha Threatened 70 FR 37160; 6/28/2005 70 FR 52630; 9/2/2005

Upper Columbia River spring-run 

Chinook Oncorhynchus tshawytscha Endangered 70 FR 37160; 6/28/2005 70 FR 52630; 9/2/2005

Snake River spring/summer run 

Chinook Oncorhynchus tshawytscha Threatened 70 FR 37160; 6/28/2005 64 FR 57399; 10/25/1999

Snake River fall-run Chinook

Oncorhynchus tshawytscha Threatened 70 FR 37160; 6/28/2005 58 FR 68543; 12/28/1993

Southern DPS Green Sturgeon

Acipenser medirostris Threatened 71 FR 17757; 4/07/2006 Proposed 73 FR 52084; 9/8/2008

Southern DPS Pacific Eulachon

Thaleichthys pacificus

Proposed 

threatened 74 FR 10857; 3/13/2009 None designated or proposed

Eastern DPS Steller Sea Lion

Eumetopias jubatus Threatened 62 FR 24345; 5/05/1997 58 FR 45269; 8/27/1993

Blue Whale

Balaenoptera musculus Endangered 35 FR 18319; 12/02/1970 None designated

Fin Whale

Balaenoptera physalus Endangered 35 FR 18319; 12/02/1970 None designated

Humpback Whale

Megaptera novaeangliae Endangered 35 FR 18319; 12/02/1970 None designated

Southern Resident Killer Whale

Orcinus orca Endangered 70 FR 69903; 11/18/2005 71 FR 69054; 11/29/2006

Marbled murrelet

Brachyramphus marmoratus Threatened 57 FR 45328; 10/01/1992 61 FR 26255; 05/24/1996

Brown Pelican

Pelecanus occidentalis Endangered 35 FR 8491; 06/02/1970 None designated

Short-tailed albatross

Phoebastria (=Diomedea) albatrus Endangered 35 FR 8491; 06/02/1970 None designated

Western snowy plover

Charadrius alexandrinus nivosus Threatened 58 FR 12864; 03/05/1993 70 FR 56969; 09/29/2005

Northern spotted owl

Strix occidentalis caurina Threatened 55 FR 26114; 06/26/1990 57 FR 1796; 01/15/1992

Oregon silverspot butterfly

Speyeria zerene hippolyta Threatened 45 FR 44935; 07/02/1980 45 FR 44935; 07/02/1980

Fender’s blue butterfly

Icaricia icarioides fenderi Endangered 65 FR 3875; 01/25/2000 71 FR 63861; 10/31/2006

Kincaid’s lupine

Lupinus sulphureus ssp. kincaidii Threatened 65 FR 3875; 01/25/2000 71 FR 63861; 10/31/2006

Willamette daisy

Erigeron decumbens var. decumbens Endangered 65 FR 3875; 01/25/2000 71 FR 63861; 10/31/2006

Bradshaw’s desert parsley

Lomatium bradshawii Endangered 53 FR 38448; 09/30/1988 None designated
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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PROPOSED ACTION

The proposed action consists of designation of the proposed North and South ODMDS located 

approximately 1 mile offshore of the entrance to the Siuslaw River on the central Oregon Coast (see 

Figure 1). For both sites, the disposal site, placement area, and drop zone are identical. The 

proposed North ODMDS is 4,800 feet by 2,000 feet with an average depth of 90 feet (depth ranges 

from approximately 30 ft to 120 ft), and has the following coordinates (NAD 83):

44o01’ 31.025”N, 124o10’ 12.917”W

44o01’ 49.393”N, 124o10’ 02.848”W

44o01’ 31.965”N, 124o09’ 01.857”W

44o01’ 13.454”N, 124o09’ 11.408”W

The proposed South ODMDS is 3,000 feet by 2,000 feet with an average depth of 78 feet (depth 

ranges from approximately 80 ft to 125 ft), and has the following coordinates (NAD 83):

44o00’ 46.724”N, 124o10’ 26.551”W

44o01’ 06.405”N, 124o10’ 24.448”W

44o01’ 04.123”N, 124o09’ 43.516”W

44o00’ 44.446”N, 124o09’ 45.626”W

Use of the proposed Siuslaw North and South ocean disposal sites would be for disposal of material 

dredged from maintenance of the federal navigation project at the Siuslaw River, and through 

separate Section 103 permit evaluations pursuant to the MPRSA for the disposal of suitable dredged 

material from other dredging projects. Each specific proposal to dispose of dredged material at the 

proposed Siuslaw sites would require a permit, or in the case of the USACE, a demonstration that 

substantive permit requirements have been met, before disposal could occur.

History of Ocean Disposal Sites

An Interim ocean disposal site, or areas in the same vicinity, have been used by the USACE Portland 

District since 1929, when hopper dredges began to work the bar and entrance channels. The Interim 

ODMDS (Area A on Figure 2) was designated an EPA Interim Site in 1977 (40 CFR 228.12).1 It 

was suspected that ocean currents were transporting dredged material placed in the Interim Site back 

into the Siuslaw entrance channel. In 1986-1987, the USACE completed dye and seabed drifter 

studies (USACE 1988). Results demonstrated dredged material deposited south and/or east of the 

centroid of the interim site, with prevailing north to northwest winds, could possibly drift back across 

or into the Siuslaw entrance channel. The Interim site also experienced mounding to 14 feet relative 

to the 1981 bathymetry due to its small size and the volume dredged. Therefore, two adjusted ocean 

disposal sites, ODMDS B and C, were selected by the USACE under Section 103 of the MPRSA 

(Area B and C on Figure 2). Since 1997, material removed from the Siuslaw federal navigation 

project has been deposited into ODMDS B and C (see Figure 2 and Table 2). 

Site B and C have also experienced mounding. Disposal restrictions, until lifted in 2008, were 

placed on the southeast corner of Site B which overlapped the Interim Site A. In addition the bulk of 

the material dredged has been placed in the larger Site B. Pending final designation by EPA, the 

USACE extended the selection of ODMDS B and C for a final 5-year period in 2004 (expires in 

2009). Following expiration, the EPA must designate ocean disposal sites under Section 102 of the 

MPRSA in order for dredged material to be disposed of at this location. Table 2 presents the volume 

of material placed offshore of the Siuslaw River. 

 

1 EPA’s interim designations were superseded by later statutory and regulatory changes.
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Figure 2. Historical Siuslaw River Ocean Disposal Sites

 Area A = EPA-designated Interim ODMDS used for dredged material disposal from 1977 to 1996.

 Areas B & C = USACE-selected Section 103(b) ODMDS used for dredged material disposal since 1996.

 Proposed North ODMDS = upper rectangle encompassing Areas A + B.

 Proposed South ODMDS = lower rectangle encompassing Area C.
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Table 2. Siuslaw River Project Dredging Volumes

Fiscal Year Dredging

Volumes (x 1,000 cy)

1929-1977 2,800.0

1977 139.3*

1978 191.4*

1979 246.6*

1980 94.2*

1981 388.4*

1982 193.4*

1983 213.3*

1984 221.1*

1985 271.2*

1986 218.8 *

1987 215.8 *

1988 114.5 *

1989 116.8 *

1990 99.0 *

1991 65.9 *

1992 194.2 *

1993 239.6 *

1994 223.3 *

1995 121.6 *

1996 84.8 *

1997 40.0 (C)

1998 69.6 (C)

1999 43.5 (B)

2000 55.1 (C)

2001 101.2 (C)

2002 117.3 (B)

2003 55.0 (B)

2004 14.1 (B) & 9.0 (C)

2005 33.4 (B)

2006 22.3 (B)

2007 76.0 (B)

2008 69.9 (B)

* Dredged material from 1977 to 1996 was placed in the EPA-designated Interim ODMDS (Area A).

Future dredged material disposal volumes are not expected to exceed 100,000 cy/annually (based on 

a 10 year average of about 53,000 cy and range of 22,300-99,975 cy) and material is expected to be 

disposed over a period of 20 days of dredging and disposal (average is about 7 days; range 3-23). 

Generally, dredging and disposal are expected to occur between June 1 and October 31 of each year. 

EPA’s primary goals in locating the proposed ODMD sites were to maximize the capacity of the 

sites since a Section 102 site designation is indefinite, minimize the potential for mounding and 

associated safety concerns, and maximize the volume of material that remains in the littoral system. 

Since there has been a history of mounding at all of the previously utilized sites, it was clear that the 

sites should be expanded to increase capacity and minimize mounding. At other ODMD sites along 
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the Oregon Coast, EPA and the Corps have found that the strategy of placing a site to the north and 

another to the south of the river mouth has worked well (Coos Bay, Umpqua, etc.), primarily because 

it allows for adaptive management of the sites given a dynamic current environment. Therefore, 

EPA is proposing both a north and south site for the Siuslaw River ODMD sites. Generally, material 

placed deeper than 60 feet remains where it is placed and is therefore, removed from the active 

littoral system. To keep more material in the active littoral system and to potentially feed the beach, 

EPA proposes a North Site configuration that expands the existing 103 Site B to include the original 

1977 Interim Site (Site A), and a similar area to the north of Site A (see Figure 3). EPA 

acknowledges that previous studies showed the potential for material disposed at Site A to re-enter 

the channel. However, considering that there are now two larger sites proposed, allowing for 

adaptive management, EPA and the Corps do not expect measurable volumes of dredged material to 

migrate back into the channel from the proposed North Site. To further address potential mounding, 

the proposed South Site’s southern boundary was moved to the south, doubling the size of the Site.

EPA proposes to utilize the shallower portions of the North Site to the maximum extent possible in 

order to keep material in the active littoral zone, limit wave effects due to mounding, and keep 

material from reentering the navigation channel. Annual bathymetric surveys have shown the 

potential for mounding at the two previously utilized Section 103 Sites B and C. Continued 

management and monitoring of the new Section 102 North and South sites will take place in 

accordance with a Site Management and Monitoring Plan (SMMP), which is currently being drafted 

and will be available for public comment before EPA finalizes its proposed action to designate the 

proposed Siuslaw North and South ocean disposal sites.

ENVIRONMENTAL BASELINE

Physical Characteristics

The Siuslaw River estuary covers about 1,780 acres and opens into the Pacific Ocean about 160

miles south of the mouth of the Columbia River. It lies within the Heceta Head littoral cell, which 

extends for about 56 miles from Heceta Head south to Cape Arago. The estuary is fed mainly by 

Siuslaw River, which is 108 miles from its mouth to headwaters and has a drainage basin of 773 

square miles. The watershed encompasses part of the Coast Range, with the Siuslaw River 

extending inland to Cottage Grove. The coastal zone of the littoral cell consists of a wide plain that 

is 1- to 2-miles wide, covered by active and stabilized sand dunes backed by the mature upland 

topography of the Coast Range. The lower portion of the Siuslaw River is bordered by broad 

alluvial flats. Between the Siuslaw River and Yaquina River estuaries, the continental shelf is at its 

widest along the Oregon Coast, extending over 44 miles offshore forming the Heceta Bank. Just 

south of the Siuslaw River, the shelf begins to narrow and is only about 19 miles wide at the mouth 

of the Umpqua River. At the mouth of the Siuslaw River, the first 2 miles or so of the shelf is 

covered with sand. From there a thin layer of mud (about 1-inch thick) mantles the surface.

The Heceta Head littoral cell is the largest on the Oregon Coast. Landward of the cell, the coast is 

primarily beach-fronting sand dunes. Headlands are located at the north and south landward ends of 

the cell. Three major river systems enter the cell. From north to south, these are the Siuslaw River, 

the Umpqua River (largest of the three), and the Coos River.

Ocean water circulation near the proposed Siuslaw sites is directly influenced by large-scale regional 

currents and weather patterns in the northwestern Pacific Ocean. During the winter, strong lowpressure systems with winds and waves predominantly from the southwest contribute to strong 
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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northward currents. During the summer, high-pressure systems dominate and waves and winds are 

commonly from the north. In both seasons there are short-term fluctuations related to local wind, 

tidal and bathymetric effects. Along the Oregon Coast, there is a southerly wind in summer that

creates a mass transport of water offshore resulting in upwelling of bottom water nearshore.

Siuslaw River Sediments

In 1991, the Portland District collected 10 sediment samples from the Siuslaw River federal 

navigation channel for physical analysis; one sample from the turning basin at river mile (RM) 5.0 

near Florence was subjected to chemical analyses (USACE 1991). Sediments were found to be 

99.9% poorly graded sand with low volatile solids content (1.1%). The median grain size of 0.32 

millimeters (mm) was that of medium sand. The results of the chemical analysis from the turning 

basin had metals concentrations below established levels of concern. No pesticides, polychlorinated 

biphenyls (PCBs), polynuclear aromatic hydrocarbons (PAHs), or phenols were detected.

In 1996, 10 surface grab samples were collected from the entrance to RM 8 (USACE 1996). These 

samples were subjected to physical tests, with grain-size ranging from 100% to 92.7% (mean 98.6%) 

poorly graded sand with volatile solids content ranging from 1.4% to 0.3% (mean 0.8%). The mean 

grain-size was that of medium sand (0.294 mm).

In 2001, eight surface grab samples were collected from the entrance to RM 6 (USACE 2001). All 

samples were submitted for physical analyses, with grain-size ranging from 100% to 97.9% (mean 

99.2%) poorly graded sand with volatile solids content ranging from 0.42% to 3.0% (mean 1.29%). 

The mean grain-size was that of medium sand (0.29 mm). Two samples were selected for chemical 

analyses to include metals, total organic carbon (TOC), PCBs, chlorinated hydrocarbons, phenols, 

phthalates, miscellaneous extractables, and PAHs; one sample was submitted for organotin (TBT -

pore water method) analysis. The samples submitted for chemical analysis were taken from the 

federal channel near the outfall to the sewage treatment plant and near the boat dock. The one 

sample analyzed for TBT was collected near the boat dock. Sediment represented by samples 

collected during this sampling event would meet the guidelines established in the Sediment 

Evaluation Framework (SEF 2009)

2

for unconfined in-water placement without further 

characterization.

In August 2006 (Sherman 2007), seven samples were collected from the Siuslaw entrance to RM 5. 

All samples were submitted for physical analyses, with grain-size ranging from 98.5% to 95.4% 

poorly graded sand (mean 97.1%), with volatile solids content ranging from 0.69% to 2.24% (mean 

1.14%). One sample was selected for chemical analyses to include metals, TOC, PCBs, chlorinated 

hydrocarbons, phenols, phthalates, miscellaneous extractables, and PAHs. Two samples were 

submitted for TBT analysis, one from the turning basin adjacent to the marina and the second from 

 

2

 Pursuant to the Ocean Dumping Regulations at 40 C.F.R. § 227.13(b), dredged material which meets the 

following criteria is environmentally acceptable for ocean dumping without further testing: (1) dredged 

material composed primarily of sand, gravel, rock, or any other naturally occurring bottom material with 

particle sizes larges than silt, and the material is found in areas of high current or wave energy such as streams 

with large bed loads, or coastal areas with shifting bars and channels; or (2) dredged material for beach 

nourishment or restoration and is composed primarily of sand, gravel, or shell with particle sizes compatible 

with material on the receiving beaches; or (3) when the material is substantially the same as the substrate at the 

proposed disposal site and the site from which the material is taken is far removed from known existing and 

historical sources of pollution such that there is a reasonable assurance that the material has not been 

contaminated by such pollution. The use of the SEF screening levels provide additional safeguards for 

material that would otherwise meet the regulatory criteria for environmentally acceptable material for ocean 

dumping without further testing.
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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the federal channel by the fuel dock. Pore-water TBT was not analyzed due to insufficient porewater volume in the samples, a result of the high sand content. The chemical analyses showed only 

low levels of contamination in any of the samples, with all levels well below their respective SEF 

screening levels. No pesticides, PCBs, PAHs, chlorinated hydrocarbons, or miscellaneous 

extractables were detected in any of the samples. Several metals, phthalates, phenol, and dibutyltin 

were detected, but at low levels and well below their respective screening levels. Detection levels 

were sufficiently low enough to evaluate material proposed for dredging. The analytical results of 

this characterization are consistent with historical data. Sediment represented by the samples 

collected during this sampling event met the guidelines established in the SEF for unconfined inwater placement without further characterization.

ODMDS Sediments

In August 2008, 10 surface-grab sediment samples were collected at ODMDS B and C (proposed 

North and South sites) with a 0.96 m2 modified Gray-O’Hara box core sampler (Figure 3). Three

samples (01, 02 and 03) were collected from east to west on the centerline of Site B. Three samples 

(07, 08 and 09) were collected from east to west on the centerline of Site C. Four reference samples

were collected north, south, and between Sites B and C (04, 05, 06, and 10). All samples were 

subjected to physical and chemical analysis.

Physical Analysis and TOC. The mean value for a grain-size of sand or greater was 97.25% with a 

mean value of 3.71% fine-grained material (less than 230 sieve); mean value for TOC was 0.107%.

Metals. Sediments were analyzed for 10 metals. Of these, all but antimony (Sb), silver (Ag), and 

mercury (Hg) were present in all of the samples. Antimony was not present in any sample at 0.02 

ppm. No detected metal values approached their respective SEF screening levels.

Pesticides/PCBs. Chlordane was reported as technical chlordane in one sample (01), and alpha and 

gamma Chlordane in three samples (01, 02, 06). All values were below method reporting levels and 

well below SEF screening levels. No other pesticide was detected. No PCBs were detected.

Chlorinated Hydrocarbons, Phthalates, Phenols, and Miscellaneous Extractables. No chlorinated 

hydrocarbons were detected. Several phthalates, miscellaneous extractables, and phenols were 

detected at very low levels; all were well below their respective SEF screening levels.

PAHs. Various “low molecular weight” and “high molecular weight” PAHs were detected, but at 

very low levels and well below their respective SEF screening levels.

Water Quality

Water quality throughout the action area is expected to be typical for seawater of the Pacific 

Northwest. There is no reason to expect significant chemical contamination in either the water or 

sediments as few industries are located along the estuary. A large data set regarding the impact of 

dredged material disposal on the water column was accumulated in the early 1980s, and focus has 

shifted away from the water column pathway to one having more direct contact with bulk or 

suspended sediment. Currently, water column tests are rarely performed unless there is a “reason to 

believe” a water column release may occur.
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Figure 3. Siuslaw River ODMDS Sampling Locations, 2008
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Overview of Aquatic Resources

Benthic Invertebrates

Field sampling in October 1984 and January 1985 gathered information on benthic invertebrates at 

14 stations off the mouth of the Siuslaw River (USACE 1992). Another benthic study was 

conducted at 11 offshore stations in September 1988 (USACE 1992). During these studies, the 

Siuslaw offshore area exhibited diverse benthic invertebrate communities. A total of 135 taxa were 

collected in October 1984, 106 taxa in January 1985, and 163 taxa in 1988. Densities were very 

similar in 1984 and 1985, with approximately 2,200 individuals/m2collected. An average of 4,445

individuals/m2was collected in the 1988 survey. Polychaetes (annelid worms) were the numerically 

dominate species collected during the 1984-1985 sampling periods. Scoloplos armiger, Chaetozone 

setosa, and Megelona sacculata were the dominant polychaete species, reaching densities of 

approximately 2,500/m2, 1,500/m2, and 1,400/m2, respectively. Other dominant species collected 

included the amphipods Eohaustorius sencillus, Mandibulophoxus gelesi, and E. sawyeri. The area 

also had a large number of sand dollars, Dendraster excentricus. In 1988, the dominant polychaete 

species was Owenia fusiformis, although the density of this polychaete was low to moderate when 

compared to other coastal areas. Another dominant polychaete collected was Spiophanes bombyx.

Field surveys were conducted in 2008 by Marine Taxonomic Services (USACE 2009) to supplement 

earlier benthic invertebrate data and provide current information on fish and epibenthic species 

present in the area of ODMDS B and C (proposed North and South sites). The benthic infaunal 

study used a modified Gray-O’Hara box core to take five biological cores at each of the ten sampling 

stations (Figure 3). The demersal fish and epibenthic study used a 12-foot semi-balloon otter trawl 

with a 0.25-inch mesh liner to take 20-minute (bottom time) trawls at each of the six trawl sites. 

Both studies were undertaken in August and September 2008.

The benthic invertebrate fauna collected in 2008 were typical of the nearshore, high-energy 

environment found along the Oregon Coast. Tables 3 and 4 provide the dominant species at 

collected at each station in August and September 2008, respectively. Figure 4 shows the densities 

of the animals per square meter at each station, and Figures 5, 6, and 7 show the diversity and 

species richness of benthic invertebrates at each station.

Table 3. Dominant Benthic Invertebrate Fauna by Station, August 2008

Station and Species,

August 2008

Number of 

Animals

Animals per

square meter

Station 1

Nemertinea 213 443.04

Diastylopsis dawsoni 578 1202.24

Siliqua sp juv. 243 505.44

Spiophanes bombyx 216 449.28

Scoloplos armiger 70 145.60

Station 2

Nemertinea 408 848.64

Diastylopsis dawsoni 162 336.96

Siliqua sp juv. 780 1622.40

Scoloplos armiger 38 79.04

Guernea reduncans 70 145.60
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Station and Species,

August 2008

Number of 

Animals

Animals per

square meter

Station 3

Nemertinea 80 168.48

Siliqua sp juv. 97 201.76

Scoloplos armiger 78 162.24

Magelona sacculata 64 133.12

Mandibulophoxus gilesi 62 128.96

Station 4

Scoloplos armiger 77 160.16

Spiophanes bombyx 114 237.12

Siliqua sp juv. 1008 2096.64

Diastylopsis dawsoni 172 357.76

Nemertinea 514 1069.12

Station 5

Magelona sacculata 78 162.24

Scoloplos armiger 78 162.24

Siliqua sp juv. 1856 3860.48

Nemertinea 379 788.32

Dendraster excentricus juv. 59 122.72

Station 6

Nemertinea 157 326.56

Diastylopsis dawsoni 1364 2837.12

Siliqua sp juv 365 759.20

Spiophanes bombyx 110 228.80

Scoloplos armiger 75 156.00

Station 7

Nemertinea 376 782.08

Diastylopsis dawsoni 106 220.48

Siliqua sp juv 617 1283.36

Spiophanes bombyx 153 318.24

Scoloplos armiger 39 81.12

Station 8

Nemertinea 347 721.76

Diastylopsis dawsoni 678 1410.24

Siliqua sp juv 433 900.64

Spiophanes bombyx 50 104.00

Dendraster excentricus juv 56 116.48

Station 9

Nemertinea 255 530.40

Diastylopsis dawsoni 234 486.72

Siliqua sp juv 743 1545.44

Macoma sp juv 40 83.20

Spiophanes bombyx 39 81.12

Station 10

Nemertinea 284 590.72

Diastylopsis dawsoni 156 324.48

Siliqua sp juv 226 470.08

Spiophanes bombyx 115 239.20

Scoloplos armiger 80 166.40
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Table 4. Dominant Benthic Invertebrate Fauna by Station, September 2008

Station and Species,

September 2008

Number of 

Animals

Animals per

square meter

Station 1

Nemertinea 214 445.12

Guernea reduncans 132 274.56

Heteropodarke heteromorpha 65 135.20

Spiophanes bombyx 89 185.12

Diastylopsis dawsoni 78 162.24

Station 2

Nemertinea 761 1582.88

Guernea reduncans 304 632.32

Neomysis kadiakensis 129 268.32

Mytilis sp juv. 79 164.32

Dendraster excentricus 43 89.44

Station 3

Alienacanthomysis macropsis 148 307.84

Nemertinea 82 170.56

Scoloplos armiger 137 284.96

Mandibulophoxus gilesi 70 145.60

Chaetozone nr. setosa 34 70.72

Station 4

Nemertinea 541 1125.28

Siliqua sp juv. 340 707.20

Macoma sp juv. 290 603.20

Diastylopsis dawsoni 78 162.24

Tellina sp juv. 88 183.04

Station 5

Nemertinea 445 925.60

Cirripedia 191 397.28

Siliqua sp juv. 269 559.52

Macoma sp juv. 92 191.36

Tellina sp juv. 72 149.76

Station 6

Diastylopsis dawsoni 183 380.64

Tellina sp juv. 232 482.56

Siliqua sp juv. 336 698.88

Macoma sp juv. 462 960.96

Glycinde armigera 215 447.20

Station 7

Nemertinea 264 549.12

Siliqua sp juv. 113 235.04

Macoma sp juv. 136 282.88

Spiophanes bombyx 83 172.64

Scoloplos armiger 62 128.96

Station 8

Nemertinea 314 653.12

Mytilis sp juv. 273 567.84
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Station and Species,

September 2008

Number of 

Animals

Animals per

square meter

Guernea reduncans 106 220.48

Siliqua sp juv.. 66 137.28

Scoloplos armiger 49 101.92

Station 9

Nemertinea 355 738.40

Scoloplos armiger 66 137.28

Mandibulophoxus gilesi 63 131.04

Siliqua sp juv. 36 74.88

Spiophanes bombyx 30 62.40

Station 10

Nemertinea 256 532.48

Siliqua sp juv. 355 738.40

Macoma sp juv. 205 426.40

Mytilis sp juv. 145 301.60

Tellina sp juv. 142 295.36

Figure 4. 2008 Densities of Benthic Invertebrates, Siuslaw ODMDS DENSITIES OF INVERTEBRATES

0

1000

2000

3000

4000

5000

6000

7000

1 2 3 4 5 6 7 8 9 10

STATIONS

ANIMALS PER METER SQUARED

August, 2008 September, 2008
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Figure 5. 2008 Diversity of Benthic Invertebrates (H’), Siuslaw ODMDS

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

1 2 3 4 5 6 7 8 9 10

STATIONS

Shannon-Weaver Index

August, 2008 September, 2008

Figure 6. 2008 Diversity of Benthic Invertebrates (SDV), Siuslaw ODMDS

0.0000

0.1000

0.2000

0.3000

0.4000

0.5000

0.6000

0.7000

0.8000

0.9000

1.0000

1 2 3 4 5 6 7 8 9 10

STATIONS

SIMPSON DIVERSITY VALUE

August, 2008 September, 2008
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Figure 7. 2008 Species Richness of Benthic Invertebrates, Siuslaw ODMDS

0.0000

2.0000

4.0000

6.0000

8.0000

10.0000

12.0000

1 2 3 4 5 6 7 8 9 10

STATIONS

SPECIES RICHNESS

August, 2008 September, 2008

The density distribution data indicates large juvenile recruitment of most species from spring 

spawning. This recruitment includes both opportunistic short-lived species (Spiophanes bombyx) 

and longer-lived species (razor clams, Siliqua sp. juv. and Dendraster excentricus). The large 

recruitment of these longer-lived species and the recruitment of some shorter-lived species, mostly 

polychaeta and crustacea, indicate good ocean conditions in spring and summer months in this area.

The crustaceans showed some population spikes throughout the data; however, the same species 

were not always the driving factors. Gammarid amphipods were often present but also present were 

Diastylopsis dawsoni (Cumacea) and barnacles (Cirripedia), which showed up on hard features such 

as snail shells and the occasional rock. The echinoderms were driven by Dendraster sp. 

juv/Dendraster excentricus and the other miscellaneous groups were largely populated by 

Nemertinea and juvenile holothuroids.

The benthos in the area of the ocean disposal sites is typical of sandy bottom communities found 

near other disposal sites along the Oregon Coast, such as Coos Bay sites E and F, Rogue River, 

Siuslaw River and Chetco River (Hancock et. al., 1981; USACE 1985, 1988a, 1988b, 1990). This 

benthic community, largely dominated by very mobile organisms, provides an important link in the 

marine food web. These organisms serve as a direct food source for other benthic organisms and 

demersal fishes. They also play an active role in the breakdown of organic debris and the tube 

building species help to stabilize the bottom sediments.

Many of the benthic species in this study are able to survive in this dynamic environment being 

either very mobile or being able to react both to natural or man-made perturbations. They readily 

recolonize in disturbed areas such as dredging scars or disposal site events.
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Fish and Epibenthic Species

The commercially and recreationally important epibenthic species in inshore coastal areas of Oregon 

include shellfish and Dungeness crab (Cancer magister). Clam beds are located on the north side of 

the Siuslaw estuary at RM 1. Gaper clams (Tresus capex) are the dominant bivalves harvested. 

Dungeness crab adults occur on sandflat habitat along the entire Oregon Coast. They spawn in 

offshore areas and occur in the estuary when conditions are favorable in late summer and fall.

The nearshore area has been known to be a squid spawning area with the location and size varying 

annually (USACE 1992). Although there have been incidental catches of squid within 1.5 nautical 

miles of the mouth of the Siuslaw, there has been no directed squid harvest within this area. There 

have been reports of egg capsules and adults caught in trawls, as well as the presence of egg capsules 

on crab gear. Outside of the 1.5 nautical mile radius from the mouth, there have been directed squid

harvests south of Heceta Head to Cape Perpetua. Squid spawn between at water depths of 5 to 40 

meters, with maximum spawning occurring at 15 meters. After hatching, they school in the middle 

of the water column, moving toward the surface as they mature. Mature squid feed mostly at water 

depths of 20 to 50 meters (USACE 1992).

The nearshore area off the Siuslaw River supports anadromous salmonids including coho salmon 

(Oncorhynchus kisutch), winter steelhead (Oncorhynchus mykiss), and spring and fall Chinook 

salmon (Oncorhynchus tshawytscha), as well as a variety of other pelagic and demersal fish species. 

Other pelagic species include the Pacific herring (Clupea harengus pallasi), northern anchovy

(Engraulis mordax), and surf smelt (Hypomesus pretiosus).

Demersal species present in the inshore area are mostly residents and include a number of sculpins, 

sea perch, and rockfish species associated rocky habitats, as well as flatfish species occurring 

predominantly over open sandflats. Flatfish include English sole (Parophrys vetulus), sanddab 

(Citharichthys sp.), and starry flounder (Platichthys stellatus). English sole and starry flounder, 

along with the sand sole (Psettichthys melanostictus), spawn in the inshore area in the summer and 

juveniles of these, as well as other marine species, may rear in the Siuslaw estuary.

Field surveys were conducted in August and September 2008 by Marine Taxonomic Services 

(USACE 2009) to provide current information about the fish and epibenthic species present in the 

area of ODMDS B and C (proposed North and South sites). Tables 5 and 6 show the trawl results 

with numbers of individuals, average size, and size range for the fish and crabs captured.
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Table 5. August 2008 Trawl Data, Siuslaw ODMDS

August 2008 Trawl# 1 2 3 4 5 6

Cancer 

magister

Dungeness Crab - Female

number of individuals 14 3 3 6 60 7

size range (mm) 40-140 120-150 110-140 125-140 30-162 55-175

average size (mm) 114.1 140 126.6 131.6 50 133.6

Cancer 

magister

Dungeness Crab - Male

number of individuals 5 2 2 188 5

size range (mm) 120-155 75-165 135-145 32-150 130-140

average size (mm) 138 120 140 47.7 136

Bothidae

juv.

Juvenile Flat Fishes

number of individuals 1 2 1

size range (mm) 41 20-42 38

average size (mm) 41 31 38

Citharichthys

sp.

Sanddab

number of individuals 4 1 2 1

size range (mm) 70-170 110 110 55

average size (mm) 113 110 110 55

Engraulis

mordax

Northern Anchovy

number of individuals 1

size range (mm) 90

average size (mm) 90

Enophrys

bison

Buffalo Sculpin

number of individuals 1 4 1

size range (mm) 118 90-135 100

average size (mm) 118 115 100

Gadidae

Pacific Tom Cod

number of individuals 47 94 13 116 129 39

size range (mm) 50-175 52-185 60-190 56-188 48-185 55-170

average size (mm) 78.6 79 102.7 87.1 85.9 96.7

Isopsetta 

isolepis

Butter Sole

number of individuals 150 144 80 131 2 54

size range (mm) 40-200 45-172 40-210 50-220 140-143 45-235

average size (mm) 117 118 120 125.2 141.5 149

Leptocottus 

armatus

Staghorn Sculpin

number of individuals 30 17 14 9 12

size range (mm) 128-190 139-189 145-205 115-192 110-170

average size (mm) 162.6 162.4 163.7 143 140.6

Liparis

pulchellus, 

Liporidae

Showy Snailfish

number of individuals 27 24 15 4 1 3

size range (mm) 16-120 18-150 20-112 14-34 53 120-150

average size (mm) 34.5 37.2 40.6 22 53 133.3

Liparididae

juv.

Snail Fish

number of individuals 2 1

size range (mm) 16-18 20

average size (mm) 17 20

Ophiodon 

elongatus

Ling Cod

number of individuals 2 1 1 2

size range (mm) 112-150 120 135 100-100

average size (mm) 136 120 135 100

Osmeridae

Smelt

number of individuals 31 7 27 26 2

size range (mm) 32-112 35-102 28-110 30-90 95-97
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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August 2008 Trawl# 1 2 3 4 5 6

average size (mm) 65.3 71.7 59.4 50.5 96

Parophrys

vetulus

English Sole

number of individuals 45 38 11 147 15 43

size range (mm) 82-330 35-265 67-285 45-275 87-120 38-240

average size (mm) 152 157.5 146.1 140.5 105.4 129

Pholis 

ornata

Saddle Back gunnel

number of individuals 20 4

size range (mm) 130-190 85-145

average size (mm) 166 120

Pleurenectidae

juv.

Flat Fishes

number of individuals 71 26 30 16 5 1

size range (mm) 28-53 30-45 27-88 30-45 35-46 50

average size (mm) 37.7 37.1 39 36.4 39.8 50

Psettichthys 

melanostictus

Sand Sole

number of individuals 1 3 1 3 4 10

size range (mm) 48 143-195 175 165-250 152-192 115-200

average size (mm) 48 171 175 195 171.5 147.8

Raja

binoculata

Big Skate

number of individuals 1

size range (mm) 365

average size (mm) 365

Scorpaenidae

Juvenile Rock Fish

number of individuals 2 2 1

size range (mm) 45-52 50-53 60

average size (mm) 48.5 51.5 60

Stellerina

xyosterna

Prickle Breasted Poacher

number of individuals 140 149 87 139 30 8

size range (mm) 15-63 116-131 17-65 18-72 18-60 25-56

average size (mm) 38.1 40.6 37.6 40.3 36.2 40.75

Pallasina

barbata

Tube Nose Poacher

number of individuals 6 4 3

size range (mm) 73-149 47-77 68-170

average size (mm) 96.2 62.75 105.3

Pisaster

brevispinus

Pink Short Spined Starfish

number of individuals 1

(not measured)

Crangon spp, Cancer larval forms, isopods, 

amphipods, mysids, drift algae (present but 

not counted)

X X X X X X
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Table 6. September 2008 Trawl Data, Siuslaw ODMDS

September 2008 Trawl# 1 2 3 4 5 6

Cancer

magister

Dungeness Crab - Female

number of individuals 2 1 1

size range (mm) 50-55 45 135

average size (mm) 52.5 45 135

Cancer 

magister

Dungeness Crab - Male

number of individuals 6 8 2 18 4

size range (mm) 108-165 45-170 110-140 110-180 8-138

average size (mm) 138.6 110 125 136.9 70.5

Citharichthys

sp.

Sanddab

number of individuals 1 13 2 8 4 16

size range (mm) 105 90-125 120-150 90-150 50-188 90-174

average size (mm) 105 109.2 135 109.4 114.5 114.6

Gadidae

Pacific Tom Cod

number of individuals 49 5 1 1 13

size range (mm) 50-130 80-130 102 120 88-178

average size (mm) 99.8 95 102 120 130.2

Hexagrammos 

decagrammus

Kelp Greenling

number of individuals 1

size range (mm) 108

average size (mm) 108

Isopsetta

isolepis

Butter Sole

number of individuals 37 7 9 15 48 22

size range (mm) 38-210 55-190 125-200 55-170 110-220 84-170

average size (mm) 120.6 129.3 158.3 117.9 141.8 133.1

Leptocottus 

armatus

Staghorn Sculpin

number of individuals 16 2 1 9 23 1

size range (mm) 105-200 140-160 130 120-160 95-140 115

average size (mm) 135.75 150 130 138.8 115.1 115

Liparis 

pulchellus

Showy Snailfish

number of individuals 1 6 1 4 2

size range (mm) 59 55-145 135 65-180 80-130

average size (mm) 59 77.5 135 100 105

Osmeridae

Smelt

number of individuals 57

size range (mm) 30-110

average size (mm) 49.5

Parophrys 

vetulus

English Sole

number of individuals 23 11 9 13 10 33

size range (mm) 45-170 49-180 45-140 42-125 40-125 44-150

average size (mm) 88.6 96.8 65.1 69.3 56.9 73.5

Pleurenectidae

juv.

number of individuals 2 4 9 1

size range (mm) 50-50 45-50 40-50 45

average size (mm) 50 47.5 47.4 45

Psettichthys 

melanostictus

Sand Sole

number of individuals 1 3 2 3 5 3

size range (mm) 215 110-180 180-250 145-150 140-190 130-180

average size (mm) 215 150 215 148.3 167 154
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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September 2008 Trawl# 1 2 3 4 5 6

Raja 

binoculata

Big Skate

number of individuals 1 1

size range (mm) 235 280

average size (mm) 235 280

Stellerina

xyosterna

Prickle Breasted Poacher

number of individuals 38 5 38 8 30

size range (mm) 40-100 50-70 20-85 55-140 45-120

average size (mm) 55.1 60.6 49.2 74.1 63.3

Pallasina

barbata

Tube Nose Poacher

number of individuals 4 3 1 7 4

size range (mm) 55-100 95-100 100 75-100 90-110

average size (mm) 78.75 96.6 100 89 98.3

Pisaster

brevispinus

Pink Short Spined Starfish

number of individuals 1 1 4

(not measured)

Crangon spp, Cancer larval forms, isopods, 

amphipods, mysids, drift algae (present but 

not counted)

X X X X X X

The trawl data shows that non-commercial species are present in the ODMDS area. These included

quantities of krill (Mysidacea) and various species of sand shrimp, mostly of the genus Crangon 

along with several species of fish. These data also showed several commercially and recreationally 

important species in the study area. Most of the specimens are juvenile or sub-legal individuals. 

Commercially and recreationally important species included the following:

 Cancer magister (Dungeness crab)

 Citharichthys sp. (sand dab)

 Isopsetta isolepis (butter sole)

 Psettichthys melanostictus (sand sole)

 Ophiodon elongates (ling cod)

 Parophrys vetulus (English sole)

The trawl samples denote this near shore area as a nursery ground with an abundant food source. 

Most of the species encountered in the trawl samples were benthic feeders that tend to utilize the 

shallower areas both because of the abundant food and because of fewer predators. The majority of 

the fish and crabs captured in the trawls were juveniles and young of the year. However, larger crabs 

and fish have the ability to avoid the trawl net.
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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ESA-Listed Species Status and Occurrence in the Vicinity of the 

Proposed Siuslaw Ocean Disposal Sites

The federally listed species that may occur in the Siuslaw River coastal area (Lane County, Oregon) 

was obtained from the NMFS and USFWS websites. Table 1 details the listed species and 

designated critical habitat that may occur in the action area. Those species and critical habitat are 

addressed further below.

Coho Salmon

Coho salmon are distributed throughout the Pacific Ocean north of central California. This 

anadromous salmonid exhibits a relatively short 3-year life cycle. Adults typically reenter 

freshwater in late summer through fall, spawn by mid-winter, and die thereafter. Variation is 

exhibited between and within populations of coho salmon. Depending upon water temperature, 

incubation in river gravels requires 1.5 to 4 months. Juvenile coho salmon rear in freshwater up to 

15 months after emerging from the gravel. They undergo considerable instream migration during 

this period in the upper tributaries to find suitable winter and summer rearing habitat (Miller and 

Sadro 2003). After rearing, smolts outmigrate to the ocean in the spring as age 1+ juveniles.

Juveniles tagged by Miller and Sadro (2003) in Coos Bay, an estuary to the south of the Siuslaw 

River, showed that residence time in the lower reach of South Slough in Coos Bay was brief, 

averaging 5.8 days with a range of 4.2 to 6.2 days (based on a sample size of four fish). Residence 

time in the upper portion of Isthmus Slough of Coos Bay was considerably longer. Fish occurred in 

the upper area for up to 8 months before becoming smolts and moving down into the lower portion 

of the slough. Although the fish appeared to have the capability of moving through the lower portion 

of the slough and into the ocean in 24 hours or less, their combined behavior of holding and 

occasionally moving upstream with flood tides prolonged their residence. This behavior may be 

necessary for their final adaptation to salt water before entering the ocean and is presumed to be 

representative of behavior along the Oregon Coast.

For several months before they disperse into the open ocean, coho typically stay in nearshore areas 

close to their natal streams (Groot and Margolis 1991). Juvenile coho from California to British 

Columbia typically migrate northward along the coast, generally remaining over the continental shelf 

within sight of land and at depths less than 90 to 150 meters (Groot and Margolis 1991).

Juvenile coho salmon feed primarily on aquatic invertebrates while in freshwater, but fish become an 

important prey as they grow larger (Groot and Margolis 1991). In estuarine and marine 

environments, chum and pink salmon fry, as well as larvae of pacific crab are important prey. 

Typically, coho salmon spend two growing seasons (approximately 18 months) in the ocean before 

returning to their natal streams to spawn. However, precocious male ‘jacks’ return after 6 months.

NMFS announced listing of Oregon Coast (OC) coho salmon as a threatened species on February 4, 

2008 (73 FR 7816). The listing includes all naturally spawned populations of coho salmon in 

Oregon coastal streams south of the Columbia River and north of Cape Blanco, including the Cow 

Creek (ODFW stock # 37) coho hatchery program. Critical habitat also was designated. The 

Siuslaw River and estuary were designated as critical habitat but the ocean waters off the Siuslaw 

River were not. Therefore, there is no designated critical habitat for OC coho in the action area.
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Since 1950, fish spawning surveys conducted by the Oregon Department of Fish and Wildlife 

(ODFW) in standard index areas along the Oregon Coast have been used to assess the status and 

trends of coastal coho salmon populations. Annual estimates (1990-2006) of the total spawning 

escapement of naturally produced adult coho for the Siuslaw River are shown below (Jacobs et al., 

2002 and http://oregonstate.edu/Dept/ODFW/spawn/index.htm).

1990 1991 1992 1993 1994 1995 1996 1997 1998

2,685 3,740 3,440 4,428 3,205 6,089 7,625 668 1,089

1999 2000 2001 2002 2003 2004 2005 2006

2,724 6,767 11,024 57,129 29,257 8,443 16,907 5,869

Coho spawning primarily occurs during November and December in coastal Oregon streams. 

However in the Mid-coast Monitoring Area (includes Siuslaw River), coho stocks generally exhibit 

the most protracted spawning timing on the coast, with significant portions of the spawning run 

occurring throughout November and into mid-January (Jacobs et al., 2002). Peak juvenile 

outmigration is typically observed from early March through early April (with the range extending 

from early February through early July).

The Southern Oregon/Northern California Coast (SONCC) coho ESU was listed as threatened on 

May 6, 1997 and includes all naturally spawned populations of coho salmon in coastal streams 

between Cape Blanco, Oregon, and Punta Gorda, California (62 FR 24588). A NOAA technical 

memorandum (Good et al., 2005) found that recent data do not suggest any marked change in the 

abundance or distribution of SONCC coho. Critical habitat was identified on May 5, 1999 (64 FR 

24049). In that final rule, designated critical habitat, “consists of the water, substrate, and adjacent 

riparian zone of estuarine and riverine reaches” in specified hydrologic units of river reaches 

accessible to coho salmon within the listed ESU (64 FR 24049). The proposed Siuslaw ocean 

disposal sites are not located within designated critical habitat for the SONCC coho ESU. This coho 

ESU, like other west coast coho ESUs, typically migrate north along the coast. Therefore, SONCC 

coho may utilize the action area for migratory purposes, however, migrating individuals are likely to

be further offshore than the action area.

In 2005, SONCC coho ESA status was reaffirmed as threatened and three artificial propagation 

programs were added as part of this ESU: (1) Cole Rivers Hatchery (ODFW stock #52), Rogue 

River, Oregon; (2) Trinity River Hatchery, Trinity River, California; and (3) Iron Gate Hatchery, 

Klamath River, California (70 FR 37160). The NMFS determined that these artificially propagated 

stocks are no more divergent relative to the local natural population(s) than what would be expected 

between closely related natural populations within the ESU (70 FR 37160).

Also in 2005, the Lower Columbia River Coho Salmon ESU was listed as threatened and includes all 

naturally spawned populations of coho salmon in the Columbia River and its tributaries in 

Washington and Oregon, from the mouth of the Columbia up to and including the Big White Salmon 

and Hood Rivers, and includes the Willamette River to Willamette Falls, Oregon, as well as twentyfive artificial propagation programs (70 FR 37160). 

Chinook Salmon

Several ESUs of Chinook salmon listed in 2005 (70 FR 37160) could potentially be in the action area 

during disposal activities. Those include the Lower Columbia River Chinook (threatened), Upper 

Willamette River spring-run Chinook (threatened), Upper Columbia River spring-run Chinook 

(endangered), Snake River spring/summer run Chinook (threatened), and Snake River fall-run 
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

24

Chinook (threatened). All of these ESUs have designated critical habitat, but only the Upper 

Willamette River Chinook has designated critical habitat within the action area (from the line of 

extreme high tide to a depth of 100 ft and inclusive of Lane County). None of these ESUs spawn in 

the Siuslaw River, but they are ocean-type Chinook and adults may be transiting the action area 

during disposal activities. 

Green Sturgeon

The threatened Southern distinct population segment (DPS) of the green sturgeon includes all green 

sturgeon that spawn within the Sacramento-San Joaquin rivers. Critical habitat was proposed for the 

Southern DPS in September 2008 (73 FR 52084). The proposed ODMD sites are within the 

proposed critical habitat. However, neither dredging nor disposal of dredged material are proposed 

as activities that may affect the proposed primary constituent elements proposed within that 

geographic area. Green sturgeon that spawn to the north, primarily in the Klamath and Rogue rivers, 

constitute the Northern DPS, which is not federally listed. The Northern DPS and the Southern DPS 

were found to be genetically distinct. Israel and others (2004) showed genetic differences between 

one group of San Pablo Bay and Columbia River fish and a second group of Klamath River and 

Rogue River fish.

Green sturgeon spend more time in the marine environment than other sturgeon species (Adams et 

al., 2002). Green sturgeon spawn in their natal rivers and migrate downriver to the ocean after 3 to 5 

years and disperse along the coastline. Green sturgeon have delayed sexual maturity, somewhere 

from 13 to 20 years, and they apparently only spawn every 2 to 5 years (Moyle 2002). Green 

sturgeon in the ocean can be assumed to remain largely inside the 100-meter depth contour and 

typically occupy depths of 40-70 meters (Erickson and Hightower 2007). In the Rogue River, green 

sturgeon spend approximately 6 months in fresh water annually and have been captured as far 

upriver as RM 65 (105 km) and emigrate to the ocean between October and January (Erickson et al., 

2002; Erikson and Webb 2007). Southern DPS green sturgeon, radio-tagged in the Sacramento 

River, have recently been shown to occur seasonally in Willapa Bay, as well as other northern 

estuaries including the Columbia River estuary during the summer and early fall (Moser and Lindley 

2007). Although there appears to be substantial spatial overlap in the two DPSs, the Northern DPS 

appears to utilize smaller river estuaries, such as the Siuslaw River estuary, to a greater extent than 

the Southern DPS (NMFS 2007).

The NMFS identified one of the major threats to the Southern DPS green sturgeon as harvest in the 

spawning and natal areas of the Sacramento-San Joaquin rivers and in more northern ocean, coastal, 

and estuarine waters. In the northern fisheries, it is during their aggregation in estuaries that the 

greatest catch of Southern DPS green sturgeon occurs. In northern waters, green sturgeon are 

captured either in directed sturgeon fisheries in estuarine waters, as by-catch in salmon gillnet 

fisheries in estuaries and rivers, or in coastal trawl fisheries along the West Coast (NMFS 2007). 

Historically, harvest came predominately from the Columbia River (51%), coastal trawl fisheries 

(28%), the Oregon fishery (8%), and the California tribal fishery (8%; Adams et al., 2002).

Moser and Lindley (2007) propose that green sturgeon utilize northern estuaries to optimize their 

growth potential in summer by foraging in warm, saline estuaries and caution that altering the quality 

of estuarine habitats could negatively affect this species throughout its range.

Habitat use and food habits of green sturgeon in northern estuaries have not been investigated in 

detail. Digestive tract contents from 46 commercially caught Columbia River green sturgeon were 

found to contain only algae (species unknown) and pebbles. A digestive tract sample from one 
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Rogue River green sturgeon contained an exoskeleton of one crayfish (Pacifasticus spp.) and algae 

(ODFW 2005). The Rogue River fish was likely from the Northern DPS. Collection of green 

sturgeon from Willapa Bay showed that they fed on burrowing thalassinidean shrimp that are 

abundant in the bay (Moser and Lindley 2007). Adults captured in the Sacramento-San Joaquin 

delta were benthic feeders on invertebrates including shrimp, mollusks, amphipods, and small fish 

(Houston 1988; Moyle et al., 1992). Juveniles in the Sacramento River delta fed on opossum 

shrimp, Neomysis mercedis and Corophium amphipods (Radtke 1966).

From 2000 to 2004, ODFW conducted a study of coastal streams to examine characteristics of green 

sturgeon populations in Oregon. The Siuslaw River was sampled during 3 weeks in May and June 

2003 with gill nets, seines, and underwater cameras. This location was chosen based on areas 

previously noted by anglers as supporting sturgeon, however, no green sturgeon were captured 

during this time period (Farr and Rien 2003). According to NMFS (see 73 FR 52084), Southern 

DPS green sturgeon presence is likely, but not confirmed in the Siuslaw River estuary. The Siuslaw 

River estuary is not identified as proposed critical habitat for Southern DPS green sturgeon (see 73 

FR 52084). Southern DPS green sturgeon may occur at or near the proposed North and South 

Siuslaw ocean disposal sites as they migrate to northern estuaries during summer and early fall.

Pacific Eulachon

The Southern Distinct Population Segment (DPS) of Pacific Eulachon was proposed threatened in 

March 2009 (74 FR 10857). Eulachon (commonly called smelt, candlefish, or hooligan) are a small, 

anadromous fish from the eastern Pacific Ocean. Eulachon typically spend 3 to 5 years in saltwater 

before returning to freshwater to spawn from late winter through mid spring. Eulachon occur in 

nearshore ocean waters and to 1000 feet (300 m) in depth, except for the brief spawning runs into 

their natal (birth) streams. In the continental United States, most eulachon originate in the Columbia 

River Basin. Other areas in the United States where eulachon have been documented include the 

Sacramento River, Russian River, Humboldt Bay and several nearby smaller coastal rivers (e.g., 

Mad River), and the Klamath River in California; the Rogue River and Umpqua Rivers in Oregon; 

and infrequently in coastal rivers and tributaries to Puget Sound, Washington. The NMFS Status 

Review for Eulachon concluded that eulachon were thought to occur in “rare” relative abundance in 

the Siuslaw River (NMFS 2008). Although eulachon migrate along the coast, little is known about 

eulachon use of the nearshore and marine habitat.

Marine Mammals

The Steller sea lion, listed as threatened in 1990 and reconfirmed as threatened for the Eastern DPS 

in 1997 (58 FR 45269), breeds along the West Coast of North America from California’s Channel 

Islands to the Kurile Islands and the Okshotsk Sea in the western north Pacific Ocean. They are 

year-long residents along the Oregon Coast, and are expected to occur as migrants in the vicinity of 

the proposed North and South Siuslaw ocean disposal sites. Steller sea lions are known to haul out at 

10 sites along the Oregon Coast: Columbia River South Jetty (Clatsop County), Ecola State Park 

(Clatsop County), Three Arch Rocks (Tillamook County), Cascade Head (Tillamook County), Seal 

Rock (Lincoln County), Sea Lion Caves (Lane County), Cape Arago (Coos County), Blanco Reef 

(Curry County), Orford Reef (Curry County) and Rogue Reef (Curry County). Of these sites, Orford 

Reef and Rogue Reef are rookeries and are designated critical habitat for Steller sea lion. Designated 

critical habitat at both the Rogue and Orford Reefs includes an air zone that extends 3,000 feet above 

the site measured vertically from sea level and an aquatic zone that extends 3,000 feet seaward in 

state and federally managed waters [50 C.F.R. § 226.202(b)]. Orford Reef and Rogue Reef are 
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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located over 80 miles south of the action area. Therefore, the proposed North and South Siuslaw 

ocean disposal sites are not located in or near designated critical habitat for Steller sea lion.

Steller sea lion population counts for Oregon have increased since 1977, when the statewide non-pup 

population totaled 1,431, to 4,169 in 2002, an annual rate of increase of about 3.7% (Brown et al. 

2002). Brown and others (2002) also found that the pup counts for the Rogue Reef have increased 

over time, from 492 in 1990 to 746 in 2002, and at Orford Reef from 298 in 1990 to 382 in 2002, 

although the pup counts have not been completed annually. Steller sea lion numbers appear to be 

lower off Oregon in the winter than summer. However, exchange between rookeries by breeding 

adult females and males (other than between adjoining rookeries) appears low (Angliss and Outlaw 

2005). Steller sea lions forage at river mouths and nearshore areas along the coast. Roffe and Mate 

(1984) determined that proximity to the mouth of a river was the most important factor in 

determination of forage areas.

The blue whale, fin whale, humpback whale, and southern resident killer whale are all listed as 

endangered and occur as migrants in waters off the Oregon Coast. The population status of most of 

these species is described in the 2007 U.S. Pacific Marine Mammal Stock Assessments (Carretta et 

al., 2007). According to Maser and others (1981), blue whales occur off the Oregon Coast in May 

and June, as well as August through October. Blue whales typically occur offshore as individuals or 

in small groups and winter well south of Oregon. Fin whales also winter far south of Oregon and 

range off the coast during summer. Whaling records indicated that fin whales are harvested off the 

Oregon Coast from May to September. Humpback whales primarily occur off the Oregon Coast 

from April to October with peak numbers from June through August. Green and others (1992) 

observed 35 humpback whales near Heceta Bank (approximately 15-30 miles off the Oregon Coast 

in Lincoln and Lane counties) in June 1990. They noted that humpback whales were particularly 

concentrated in Oregon along the southern edge of Heceta Bank and found this species primarily on 

the continental shelf and slope.

The southern resident killer whale population contains three pods (or stable family-related groups)—

J pod, K pod, and L pod—and is considered a stock under the Marine Mammal Protection Act. 

Their range during the spring, summer, and fall includes the inland waterways of Puget Sound, Strait 

of Juan de Fuca, and Southern Georgia Strait. Their occurrence in the coastal waters off Oregon has 

been documented. Little is known about the winter movements and range of the southern resident 

stock. The southern resident population is currently estimated at about 88 whales, a decline from its 

estimated historical level of about 200 during the mid- to late-1800s. Critical habitat was designated 

for this whale in 2006 (see 71 FR 69054), but is restricted to Washington State.

Coastal Birds

The species list from the USFWS website identified the federally listed species that may occur in 

Lane County, Oregon. From this list, EPA ascertained that the proposed Siuslaw ocean disposal 

sites are within the range of three listed coastal avian species for which USFWS has primary

responsibility. These include marbled murrelet, short-tailed albatross, and the brown pelican (see 

Table 1). Critical habitat has been designated for the marbled murrelet, but it is restricted to upland 

areas and does not include any marine areas, such as the proposed ocean disposal sites. The brown 

pelican was proposed for delisting in February 2008 (73 FR 9407) and does not have any designated 

critical habitat. Likewise, no critical habitat has been designated for the short-tailed albatross.

Marbled murrelets are observed in small flocks or as individuals in the ocean and near coastal 

embayments throughout the year. Brown pelicans are seasonally abundant (June to September) 
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along the Oregon coast and in the lower reaches of various estuaries. Most brown pelicans on the 

Oregon coast are immature birds but the population includes some post-breeding adults that have 

dispersed northward from breeding locations in California and Mexico. Neither species is known to 

utilize the sea floor at the proposed sites for foraging and feeding although prey organisms might be 

present in the vicinity. Marbled murrelets and brown pelicans seem to prefer shallower waters 

(depth no greater than 40 feet) to forage. Because they have a preference for shallower waters, they 

are unlikely to be affected by the accumulation of disposed material on the ocean floor in the deeper 

portions of the proposed sites. The shoreward portions of the disposal sites would be located within 

approximately 30 feet of water and the physical disturbance associated with disposal could result in 

temporary decreases or displacement of foraging activity. Brown pelicans are commonly observed 

in and around human activities and appear to be habituated to human activity.

The short-tailed albatross was historically hunted for feathers, but currently, the primary threat to the 

continued existence to the species is posed by a catastrophic volcanic or weather event at one of the 

small handful of breeding locations in Japan. The short-tailed albatross may occur in the vicinity of 

the proposed Siuslaw ocean disposal sites during the summer months and may utilize the waters for 

foraging and feeding.

Terrestrial Birds, Invertebrates and Plants

The USFWS identified two listed terrestrial bird species, two listed invertebrate species, and three 

listed plant species for Lane County, Oregon (see Table 1). Critical habitat has been designated for 

the western snowy plover (70 FR 56969) and the northern spotted owl (57 FR 1796), but no 

designated critical habitat for either species is located within the action area. The western snowy 

plover may breed along the near the Siuslaw River. However, western snowy plover breeding and 

feeding occur on beaches rather than in open water. Therefore, the western snowy plover would not 

be expected to be present within the action area.

The Oregon silverspot butterfly occupies coastal headlands or Coast Range peaks that provide 

specific habitat features, primarily because of the presence of its host plant, the early blue violet 

(Viola adunca). This butterfly species would not occur in the Siuslaw action area because there is no 

suitable habitat present. The northern spotted owl, Fender’s blue butterfly, Kincaid’s lupine, 

Willamette daisy, and Bradshaw’s desert parsley are not aquatic, would not be at the proposed sites, 

and therefore, would not be affected by EPA’s action.

ASSESSMENT OF EFFECTS

In reviewing the potential effects of EPA’s action (final designation of ocean dredged material 

disposal sites) on the species identified by NMFS and USFWS, EPA finds that site designation itself 

has no direct impact on any of the identified ESA-listed species or designated critical habitat. This 

finding is supported by EPA’s analysis that site designation does not create or confer rights on any 

person to use a designated site upon the effective date of site designation. Persons or entities who 

seek to use a site must first obtain a federal permit, or in the case of the USACE, meet the 

substantive permit requirements, in order to actually use a designated ocean dredged material 

disposal site. This process would include meeting the requirements of applicable statutes and 

regulations. The use of a site is managed through adherence to the Site Management and Monitoring 

Plan (SMMP) which must be finalized prior to site designation. The SMMP outlines site use 

requirements, monitoring protocols, and incorporates adaptive management principles for ongoing 

use of the site. EPA recognizes, however, that site designation is intended to have a practical result. 

When sites are designated, it is expected that such sites will be used by persons or entities meeting 
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the statutory and regulatory criteria for ocean disposal of dredged material. Consequently, and 

consistent with the Biological Opinions prepared by NMFS at other projects where ocean disposal of 

dredged material occurs, EPA has considered that certain ESA-listed species may potentially be 

affected by an actual disposal of dredged materials at designated sites. Actual disposal is an indirect 

but reasonably certain outcome of site designation.

Dredging itself is not dependent on the site designation because other disposal alternatives are 

available. Other in-water sites could be proposed by the USACE and/or material could be disposed 

of at upland locations. Therefore, the dredging is not caused by and will not result from the 

proposed action (indirect effect), the dredging has independent utility (interdependent effect), and the 

dredging does not depend on site designation for its justification (interrelated effect). Therefore, 

EPA has not included the effects of dredging in the assessment of effects of the proposed site 

designations.

Coho Salmon

EPA’s proposed site designation would not have a direct physical effect on the proposed disposal 

site. Disposal of dredged material at the proposed Siuslaw ocean disposal sites will have an effect on 

the water column and the bottom habitat. The disposal plume will pass through the water column 

and create a turbid environment that may cause fish to move out of or avoid the area. The bottom 

habitat would be impacted in the portion of the disposal area where the material hits bottom and 

buries the existing benthic community at the site. Loss of benthic invertebrate populations on the 

bottom in portions of the disposal site is not likely to have an effect on food resources for either adult 

or juvenile coho salmon. Indirect impacts could occur if disposal operations changed the value of 

the habitat by burying the existing benthic community in portions of the disposal sites where dredged 

material is deposited. The benthic community would be expected to re-colonize within a period of a 

few weeks to months after disposal, limiting any effects to forage fish (USACE 1993). Both adults 

and juveniles feed principally on pelagic species which are not associated with bottom habitat. The 

only exception is sand lance, which could be impacted in the disposal site area if individuals are 

buried in the sand during disposal operations. Though normally pelagic, sand lance bury themselves 

in the sand as a defense mechanism. However, sand lance are very abundant in the coastal inshore 

area and it is unlikely that the number of sand lance impacted during disposal events would have a 

significant impact on the size of sand lance populations. Since the adjacent area consists of very 

similar habitat to that of the proposed Siuslaw sites, the avoidance of the disposal area would not 

result in increased predation or decreased food availability for coho.

Adult and juvenile coho could potentially be migrating through the action area during use of the 

proposed ocean disposal sites. Oregon Coast coho would be migrating through the site as they 

transit between the Siuslaw River and the ocean and vice versa. SONCC and Columbia River coho 

could be migrating along the coast and through the sites during disposal activities, but would 

typically be expected to be further offshore than the action area. The proposed ocean disposal sites 

do not provide any unique or relatively higher value habitat for coho salmon migration, rearing, 

resting, or foraging. It is unlikely that adult coho would experience physiological effects as a 

consequence of disposal because they are capable of faster swimming speeds and can avoid the 

resulting turbidity plume and physical disturbance to the water column. Modeling recently

completed by the USACE for the Umpqua River ODMD sites showed that water column turbidity 

would be expected to dissipate within a few minutes for 97% of the dredged material disposed 

(sandier material), and within a half hour for finer grained sediments, which at the Umpqua comprise 

about 3% of dredged material (USACE 2008). Sediment grain sizes in the Siuslaw channel are 

similar, but with a slightly lower percentage of fine grained sediment. Therefore, it is reasonable to 
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expect that the modeling results from the Umpqua would be a conservative estimate of water quality 

turbidity persistence after disposal. Any adult coho avoidance behavior would be limited to the 

duration of this physical disturbance. 

Outmigrating juvenile OC coho could experience physiological effects as a result of the disposal of 

dredged material by the Corps or other entity as described in the 2009 NMFS biological opinions 

(BOs) for the Rogue and Umpqua ODMD site designations. In those BOs, NMFS concluded 

“although NMFS anticipates indirect effects from EPA’s action, it does not anticipate any take will 

be caused by the site designation and adoption of the SMMP. Any further analysis of the effects of 

disposal of dredged material at the disposal site and issuance of an incidental take statement with 

reasonable and prudent measures and non-discretionary terms and conditions to minimize take will 

be prepared when the disposal permit is requested by the action agency.” Therefore, any 

physiological effects to OC coho resulting from the disposal of dredged materials at the proposed 

sites would be considered indirect effects of EPA’s site designation action.

Oregon Coast coho experienced a recruitment failure (recruits failed to replace the parental 

spawners) in the late 1990s. However, Good and others (2005) found that the 3-year period from 

2000 to 2002 produced a nearly fourfold increase in spawners for the entire ESU. Good and others

(2005) also found that recent data do not suggest any marked change in the abundance or distribution 

of SONCC coho. Given that disposal in the vicinity of the currently proposed Siuslaw North and 

South ocean disposal sites has occurred since 1977, is unlikely that temporary disposal related 

impacts described above are resulting in any long-term negative effects to Oregon Coast, SONCC 

coho, or Columbia River coho ESUs. It is more likely that changes in the ESU populations are 

related to much broader regional fluctuations.

Chinook Salmon

Like SONCC and Lower Columbia River coho, Chinook typically migrate along the coast. 

Therefore, chinook may utilize the action area for migratory purposes. Those migrating individuals 

may experience similar effects to foraging and passage as discussed above for coho. Chinook would 

also be expected to avoid the area during the brief period of turbidity. Since these migrating fish 

would be larger than outmigrating juvenile OC coho and more capable of avoiding the dredge 

material plume, they would not be expected to experience any direct physical impacts from dredged 

material falling through the water column.

Green Sturgeon

According to NMFS analysis supporting the listing of the Southern DPS of green sturgeon, “the 

principal factor for decline of the Southern DPS is the reduction of the spawning area to a limited 

area of the Sacramento River” (see 71 FR 17762). No spawning habitat for the Southern DPS is 

located in the vicinity of the proposed Siuslaw ocean disposal sites. Southern DPS green sturgeon 

may occur at or near the proposed ocean disposal sites as they migrate to estuaries further north, 

including the Columbia River estuary during the summer and early fall. Use of the proposed sites 

would result in physical disturbance to the water column and turbidity, which may cause adult green 

sturgeon to temporarily avoid the disposal area during disposal events. Since the adjacent area 

consists of very similar habitat to that of the proposed Siuslaw sites, the avoidance of the disposal 

area would not result in increased predation or decreased food availability for green sturgeon. In the 

2009 BOs for EPA’s designation of the Rogue and Umpqua ODMD sites, NMFS determined that 

younger, subadult green sturgeon that may be in the action area during disposal would be at risk for 
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physical impacts associated with the discharged dredged material due to their slower swimming 

speed and that these fish would have a high likelihood of experiencing physical injury or death.

Critical habitat was proposed for the Southern DPS green sturgeon in September 2008 (73 FR 

52084), but that critical habitat has not been designated. Critical habitat was proposed in the action 

area, but only for the primary constituent elements (PCE) of food, passage, and water quality. The 

activities listed in the proposal which may affect those PCEs include bottom trawl fishing, tidal/wave 

energy, and point and non-point source pollution. Dredging and deposition of dredged material were 

not listed in the activities that may affect the relevant PCEs in coastal marine waters between 

Winchester Bay, OR and the Columbia River estuary. Therefore, no long-term effects to Southern 

DPS green sturgeon proposed critical habitat are expected.

Pacific Eulachon

According to the NMFS analysis supporting the proposed listing of the Southern DPS of Pacific 

Eulachon, the most significant threat to eulachon and their habitats are changes in ocean conditions 

due to climate change (see 74 FR 10870). Dredging is identified as a low to moderate threat to 

eulachon primarily due to spawning related impacts. However, impacts associated with disposal of 

dredged material were not identified as a threat to eulachon. Due to the relative rare abundance of 

eulachon in the Siuslaw River, the potential for eulachon to be in the action area during disposal 

activities is low. In addition, little is known about eulachon use of the nearshore and marine areas, 

such as the proposed ODMD sites. The indirect effects of EPA’s site designation, disposal of 

dredged material at the proposed sites, would result in physical disturbance to the water column and 

turbidity, which may have unknown impacts to any eulachon in the vicinity. 

Marine Mammals

For the Steller sea lion, the proposed Siuslaw North and South ocean disposal sites are not located 

near identified haul out and rookery sites. Disposal in the vicinity of the proposed sites has occurred 

regularly since 1977 and since that time, the Oregon population of Steller sea lions has increased 

steadily. Therefore, it is unlikely that disposal activities at the site are negatively impacting the 

species. It is expected that sea lions would avoid the sites temporarily during disposal of dredged 

material.

The blue whale, fin whale, humpback whale, and southern resident killer whale occur as migrants in 

waters off the Oregon Coast typically farther from shore than the action area. Whale species would 

likely avoid the ocean disposal areas during disposal operations. As described above, any impacts to 

salmonid prey species for killer whale would be expected to be temporary. Current vessel traffic 

already includes transit to similarly located disposal sites since a site has been in use in the vicinity 

of the currently proposed locations since 1977. The proposed disposal site designations are not 

expected to result in any increase in vessel traffic and therefore, no effects to marine mammals 

associated with vessel transit (vessel strikes, oil spills, etc.) are expected to result from the project.

Coastal Birds

The marbled murrelet, short-tailed albatross, and brown pelican are known to occur in the vicinity of 

Oregon coastal estuaries and adjacent ocean. However, no critical habitat for these species has been 

designated in the ocean. Disposal activities are expected to create a limited and temporary turbid 

environment which could cause prey fish to move out of or avoid the immediate area during a 

disposal event. It is also possible that minor behavioral changes by individual birds may occur (e.g., 
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individuals could be displaced a few dozen to several hundred feet by the presence of the 

dredge/barge) to avoid the immediate area during and immediately following any individual disposal 

event.

Cumulative Effects

Cumulative effects are defined as, “those effects of future State or private activities, not involving 

Federal activities, that are reasonably certain to occur within the action area of the Federal action 

subject to consultation” (50 CFR §402.02). The shoreline areas adjacent to the proposed Siuslaw 

ocean disposal sites are undeveloped as the Oregon Dunes National Recreation Area is located south 

of the mouth of the Siuslaw River and the Harbor Vista County Park is located to the north of the 

River mouth. Existing development in the area occurs primarily in Florence, located approximately 

2.5 miles southeast from the river’s mouth. However, the action area encompasses a radius of 200 

feet from the two proposed sites and does not include any shoreline. Currently the only anticipated 

user of the disposal sites is the USACE. Neither EPA nor the USACE has identified any future nonfederal actions that would affect ESA-listed species or their habitat.

Determination for ESA-Listed Species and Designated Critical 

Habitat

Coho Salmon

Based on the above assessment of the effects, it is concluded that the proposed action may affect, and 

is likely to adversely affect OC coho salmon and may affect, but is not likely to adversely affect

SONCC coho salmon and Lower Columbia River coho salmon. Critical habitat for OC coho salmon 

has been designated and the primary constituent elements (PCEs) include “offshore marine areas 

with water quality conditions and forage, including aquatic invertebrates and fishes, supporting 

growth and maturation.” However, NMFS did not designate any specific areas based on these PCEs. 

Therefore, the proposed action would result in no effect to designated critical habitat for OC coho 

salmon. Critical habitat has been designated for SONCC coho and “consists of the water, substrate, 

and adjacent riparian zone of estuarine and riverine reaches” in specified hydrologic units of river 

reaches accessible to coho salmon within the listed ESU (64 FR 24049). Designated critical habitat 

for SONCC does not include ocean waters and therefore, the proposed action would result in no 

effect to SONCC critical habitat. No critical habitat for Lower Columbia River coho has been 

designated.

Chinook Salmon

Based on the above assessment of effects, it is concluded that the proposed action may affect, but is 

not likely to adversely affect Lower Columbia River Chinook, Upper Willamette River spring-run 

Chinook, Upper Columbia River spring-run Chinook, Snake River spring/summer run Chinook, or 

Snake River fall-run Chinook. Since none of these species spawn in the Siuslaw River and only the 

Upper Willamette River Chinook has designated critical habitat within the action area, the proposed 

action will have no effect on designated critical habitat for any of these ESUs.

Green Sturgeon

Based on the above assessment of the effects, it is concluded that the proposed action may affect, and 

is likely to adversely affect Southern DPS green sturgeon. Use of the Siuslaw North and South ocean 

disposal sites for disposal could result in temporary avoidance behavior in adult green sturgeon, but 
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smaller subadult fish would be less able to avoid the area due to slower swimming speeds. 

According to the NMFS analysis supporting the listing of the Southern DPS of green sturgeon, “the 

principal factor for decline of the Southern DPS is the reduction of the spawning area to a limited 

area of the Sacramento River” (71 FR 17762). The proposed Siuslaw ocean disposal site 

designations would have no effect on the spawning area for the Southern DPS and is only expected 

to result in temporary and minor modifications to migratory pathways. Also based on the above 

assessment, the proposed action to designate two ODMD sites at the mouth of the Siuslaw River will 

not destroy or adversely modify proposed critical habitat for Southern DPS green sturgeon.

Pacific Eulachon

Based on the above assessment of the effects, it is concluded that the proposed action is not likely to 

jeopardize the continued existence of Southern DPS pacific eulachon. Use of the Siuslaw North and 

South ocean disposal sites for disposal could result in temporary avoidance behavior in any nearby 

eulachon. According to the NMFS analysis supporting the proposed listing of the Southern DPS of 

pacific eulachon, the most significant threat to eulachon and their habitats are changes in ocean 

conditions due to climate change (see 74 FR 10870). The proposed Siuslaw ocean disposal site 

designations would have no effect on climate related impacts or spawning areas for the Southern 

DPS and is only expected to result in temporary and minor modifications to migratory pathways. No 

long-term effects are expected to occur to pacific eulachon.

Marine Mammals 

Based upon the above assessment of the effects, it is concluded that the proposed action may affect, 

but is not likely to adversely affect Steller sea lion, blue whale, fin whale, humpback whale, southern 

resident killer whale. There is no designated critical habitat for the above listed species in the action 

area and therefore, the proposed action will have no effect on designated critical habitat for Steller 

sea lion or southern resident killer whale. Steller sea lions are expected to avoid the sites during 

disposal activities. The whale species generally occur as migrants much farther from shore than the 

action area, and it is likely that they would avoid the ocean disposal areas during intermittent 

disposal activities. 

Coastal Birds

Based on the above assessment, marbled murrelets, short-tailed albatross, and brown pelicans may 

temporarily avoid the disposal areas during active disposal activities. Therefore, the proposed action 

may affect, but is not likely to adversely affect marbled murrelet, short-tailed albatross, and brown 

pelican. Since no marbled murrelet critical habitat is located within the action area, the proposed 

action will have no effect on designated critical habitat for marbled murrelet.

Terrestrial Birds, Invertebrates, and Plants

None of the other listed bird, invertebrate, or plant species is likely to be present in the action area. 

Therefore, the proposed action would have no effect on western snowy plover, northern spotted owl, 

Oregon silverspot butterfly, Fender’s blue butterfly, Kincaid’s lupine, Willamette daisy, and 

Bradshaw’s desert parsley. The proposed action will also have no effect on any designated critical 

habitat for these species.
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ESSENTIAL FISH HABITAT ASSESSMENT

Pursuant to the Magnuson-Stevens Fishery Conservation and Management Act (Public Law 94-265), 

as amended by the Magnuson-Stevens Fishery Conservation and Management Reauthorization Act 

(MSA) of 2006 (P.L. 109-479) and its implementing regulations at 50 C.F.R. Part 600 Subpart K, 

federal agencies are required to consult with NMFS with respect to any action authorized, funded, or 

undertaken, or proposed to be authorized, funded or undertaken, that may adversely affect essential 

fish habitat (EFH). An “adverse effect” is defined as “any impact that reduces quality and/or 

quantity of EFH.” Adverse effects may include “direct or indirect physical, chemical, or biological 

alterations of the waters or substrate and loss of, or injury to, benthic organisms, prey species and 

their habitat, and other ecosystem components, if such modifications reduce the quality and/or 

quantity of EFH.” 50 C.F.R. § 600.910(a). The objective of federal agency consultation is to 

determine whether or not the federal agency’s proposed action “may adversely effect” designated 

EFH, i.e. those waters and substrate necessary to fish for spawning, breeding, feeding, or growth to 

maturity, for fish species regulated under a Federal fisheries management plan (FMP). If, as a result 

of the consultation, NMFS determines an action would adversely affect EFH, NMFS then determines 

whether or not Conservation Recommendations are needed. Conservation Recommendations are 

non-binding measures designed to “avoid, minimize, mitigate, or otherwise offset adverse effects on 

EFH resulting from actions or proposed actions authorized, funded, or undertaken by [a federal] 

agency.” 50 C.F.R. § 600.905(b). If NMFS determines Conservation Recommendations are needed, 

NMFS notifies the Federal agency of the determination and of the recommendations. Federal 

agencies are required to provide a written response to NMFS after receiving Conservation 

Recommendations. MSA § 305(b)(4)(B). The Federal agency response must describe the measures 

the agency proposes for avoiding, mitigating, or offsetting the impact of the activity on EFH or must 

explain its reasons for not following the recommendations provided by NMFS. 50 C.F.R. § 

600.920(k)(1). 

By letter dated March 30, 2009, NMFS provided EPA with a list of species, with designated EFH in

the vicinity of the proposed Siuslaw sites. The list was based on NMFS’ general knowledge of the 

presence of EFH as determined by studies conducted by NMFS for groundfish, coastal pelagic 

species, and Pacific Coast salmon. The NMFS conducted groundfish stock assessment studies in the 

areas offshore of California, Oregon, Washington, and southern British Columbia triennially from 

1977 to 2001 (Weinberg et al., 2002). The 2001 assessment collected data from depths ranging from 

55 to 500 meters and provides useful information on the distribution of groundfish species. A 

detailed discussion of EFH for groundfish is provided in Appendix B of Pacific Coast Groundfish 

Fishery Management Plan as amended through Amendment 19 (PFMC 2006). The report includes 

life history descriptions (Part 2), EFH text descriptions (Part 3), and habitat suitability maps for 

groundfish species of the Pacific Coast with associated life history stages. The most recent 

groundfish Stock Assessment and Fishery Evaluation document was published in 2006. A detailed 

discussion of EFH for coastal pelagic species is provided in Amendment 8 to the Coastal Pelagic 

Species Fishery Management Plan (PFMC 1998) and a recent Stock Assessment and Fishery 

Evaluation Document, June 2007. The salmon EFH is discussed in the Pacific Coast Salmon Fishery 

Management Plan as revised through Amendment 14 (PFMC 2003). All of this information was 

reviewed to assess the possible impacts to these species’ EFH from the proposed action. EPA 

reviewed the list of species provided by NMFS against the areas EPA proposes to designate as the 

Siuslaw sites and assessed whether or not the proposed action to designate the sites may adversely 

affect EFH for any of the species with designated EFH in the action area. 
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Table 7. Species with Designated EFH Offshore from the Siuslaw River as Provided by NMFS

Groundfish Species Common Name Life Stage

Larvae Juveniles Adults

Rockfish Species

Sebastes melanops Black Rockfish X X

Sebastes goodie Chilipepper X X

Sebastes rastrelliger Grass Rockfish X

Sebastes mystinus Blue Rockfish X X X

Sebastes caurinus Copper Rockfish X

Sebastes paucispinis Bocaccio X

Sebastes nigrocinctus Tiger Rockfish X

Sebastes maliger Quillback Rockfish X

Sebastes entomelas Widow Rockfish X X

Sebastes saxicola Stripetail Rockfish X X

Sebastes proriger Redstripe Rockfish X

Sebastes miniatus Vermillion Rockfish X

Sebastes rufus Bank Rockfish X

Sebastes rosaceus Rosy Rockfish X

Sebastes pinniger Canary Rockfish X X

Sebastes crameri Darkblotched Rockfish X

Sebastes zacentrus Sharpchin Rockfish X X

Sebastes diploproa Splitnose Rockfish X X

Sebastes levis Cowcod X

Sebastes helvomaculatus Rosethorn Rockfish X

Sebastes borealis Shortraker Rockfish X

Sebastes flavidus Yellowtail Rockfish X

Sebastes ruberrimus Yelloweye Rockfish X

Sebastolobus alacanus Short-spine Thornyhead X

Sebastes alutus Pacific Ocean Perch X X

Sebastes auriculatus Brown Rockfish X

Sebastes nebulosus China Rockfish X

Sebastes variabilis Dusky Rockfish X

Sebastes aleutianus Rougheye Rockfish X X

Sebastes brevispinis Silvergray Rockfish X

Flatfish Species

Atheresthes stomias Arrowtooth Flounder X

Platyichthys stellatus Starry Flounder X X

Parophrys vetulus English Sole X X

Psettichthys melanostictus Sand Sole X X

Isopsetta isolepis Butter Sole X

Citharichthys sordidus Pacific Sanddab X

Eopsetta jordani Petrale Sole X

Lepidopsetta bilineata Rock Sole X

Glyptocephalus zachirus Rex Sole X

Pleuronichthys decurrens Curlfin Sole X

Hippoglassoides elassodon Flathead Sole X

Other Species

Scorpaenichthys marmoratus Cabezon X

Hexagrammos decangrammus Kelp Greenling X X

Raja binoculata Big Skate X

Raja inornata California Skate X

Raja rhina Longnose Skate X

Ophiodon elongatus Lingcod X X

Gadus macrocephalus Pacific Cod X X X

Hydrolagus colliei Spotted Ratfish X X

Squalus acanthias Spiny Dogfish X

Anoplopoma fimbria Sablefish X X X
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

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Groundfish Species Common Name Life Stage

Larvae Juveniles Adults

Triakis semifasciata Leopard Shark X

Galeorhinus galeus Soupfin Shark X X

Merluccius productus Pacific Hake X X

Salmon Species Common Name

Oncorhynchus kisutch Coho Salmon

Oncorhynchus tshawytscha Chinook Salmon

Coastal Pelagic Species Common Name

Sardinops sagax Pacific Sardine

Scomber japonicus Pacific (Chub) Mackerel

Engraulis mordax Northern Anchovy

Trachurus symmetricus Jack Mackerel

Loligo opalescens California Market Squid

Potential Effects of the Proposed Action on EFH

The proposed sites have been selected to minimize impacts to ocean resources by avoiding unique 

areas and areas of greater biological productivity. The proposed sites have been sized large enough 

to handle disposal material for at least a 20-year period and will be managed to minimize impacts 

within the sites. In addition, both historical and recent studies have been conducted to further 

characterize the sites and help in their management and use.

Table 7 shows the fish species with designated EFH in the Pacific Ocean offshore from the Siuslaw

River. Disposal of dredged material at ocean disposal sites will have a temporary effect on the water 

column and benthic habitat at the disposal sites. Turbidity resulting from disposal may persist within 

the water column for a period of a few minutes to a half hour (USACE 2008) and the benthic 

community may take a few weeks to months to re-colonize. However, the proposed sites generally 

represent only a small portion of the overall EFH for any of the species listed below.

Groundfish Species EFH

Rockfish Species. Fourteen of the rockfish species shown in Table 7 (stripetail, redstripe, 

vermillion, bank, speckled, canary, darkblotched, sharpchin, splitnose, rosethorn, shortraker, 

yelloweye, Pacific ocean perch, and short-spine thornyhead) are expected to occur at water depths 

deeper than those occurring at the proposed ocean disposal sites. Because the proposed sites do not 

provide suitable aquatic habitat, no effects to EFH for these rockfish species are anticipated.

The remaining rockfish species shown in Table 7 rely on nearshore habitats such as shallow bays and 

nearshore rocky areas, and many are closely associated with kelp and eelgrass beds. All life stages 

are associated with some type of structure such as areas with vertical relief, mixtures of rocks and 

boulders, rock ridges, crevices of rock outcrops, pinnacles, and artificial reefs. Because the 

proposed sites do not provide the preferred aquatic habitat or habitat complexity, no adverse impacts 

to EFH for these rockfish species are anticipated.

Flatfish Species. Two of the flatfish species shown in Table 7 (rex and flathead) are expected to 

occur at water depths deeper than those occurring at the proposed Siuslaw sites. Because these sites 

do not provide suitable aquatic habitat, no effects to EFH for these flatfish species are anticipated.

The life stages of the remaining flatfish species (arrowtooth and starry flounder; English, sand, 

butter, petrale, rock, and curlfin sole; and Pacific sanddab) would likely be present in the water 

column over the proposed sites and could potentially be impacted by disposal operations. The 
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

36

proposed Siuslaw sites do provide suitable EFH for these flatfish species. Trawl data from August

and September 2008 found sanddab and English, sand, and butter sole at the proposed sites.

Cabezon and Kelp Greenling. Both of these species are abundant all year in estuarine and subtidal 

areas. Larvae and young juveniles are pelagic and have been found offshore in waters over 300 

meters in depth. Juveniles settle to the bottom and are found primarily in shallow-water bays and 

estuaries. Kelp greenling lay eggs on or between rocks or in algae beds. Rocky bottoms and cobble 

substrata are the most frequently used habitats by cabezon. Because the proposed Siuslaw sites do 

not provide the preferred aquatic habitat or habitat complexity for cabezon and kelp greenling, no 

adverse impacts to EFH for these species are anticipated.

Big Skate. Big skates are relatively abundant in northern and central California, but are not common 

south of Point Conception. Records show big skates inhabiting water as shallow as 3 meters, but in 

survey catches in the North Pacific they are found most frequently on the outer shelf in waters 50 to 

200 meters deep. Over their range, big skates have been taken from waters up to 800 meters deep; 

however, few occur deeper than 350 meters. Juveniles are associated with soft bottom sediments. In 

an assessment of habitat types and associated fish assemblages at Heceta Bank off the southern 

Oregon Coast, adult skate were most commonly found in habitat consisting of mud substrate and 

populated by sea urchins. They were evenly and sparsely distributed over mud bottoms, and usually 

lay on the bottom. The proposed Siuslaw sites provide suitable EFH for this species. Trawl data 

from August and September 2008 found a few big skates at the proposed sites.

Lingcod. Lingcod are an estuarine mesobenthal species that occurs in depths from 0 to 475 meters. 

Spawning occurs from 3 to 10 meters below mean lower low water over rocky reefs in areas of swift 

currents. Larvae occur in near shore areas from winter to late spring. Larger larvae are epipelagic, 

primarily found in the upper 3 meters of the water column. Juveniles settle in estuaries and shallow 

waters along the coast while older juveniles move offshore as they grow but are most common in 

waters greater than 150 meters. Adults prefer slopes of submerged banks 10 to 70 meters below the 

surface with sea weeds, kelp and eelgrass beds that form feeding grounds for small prey fish. They 

also prefer channels in rocky intertidal areas with swift currents that concentrate plankton and 

plankton feeding fish. Based on these habitat requirements, the proposed Siuslaw sites would not 

provide suitable EFH for lingcod. 

Pacific Cod. Pacific cod are a member of the inner shelf-mesobenthal community. The majority of 

Pacific cod are found at depths from 50 to 300 meters with spawning occurring at depths from 40 to 

265 meters. The eggs are demersal, adhesive, and are found sublittorally. Larvae and small 

juveniles are pelagic, with the highest abundance in the upper 15 to 30 meters of the water column. 

Larvae are found over the continental shelf from winter through summer. Small juveniles occur in 

depths from 60 to 150 meters gradually moving to deeper water with increased age. Larger juveniles 

and adults are parademersal occurring over mud, sand and clay, and occasionally coarse sand and 

gravel bottoms. Based on these habitat requirements, the proposed Siuslaw sites would not provide 

suitable EFH for Pacific cod.

Spotted Ratfish. Ratfish are a middle shelf mesobenthal species that occur in depths from 0 to 913 

meters. They are most abundant in depths from 100 to 150 meters. They also occur in estuaries 

during the winter and early spring to feed and mate. Ratfish are generally a deep water species that 

prefer low relief, rocky bottoms or exposed gravel or cobble. They are not commonly found over 

sand or boulders. Based on these habitat requirements, the proposed Siuslaw sites would not provide 

suitable EFH for ratfish. 
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

37

Spiny Dogfish. The spiny dogfish is an inner shelf-mesobenthal species with a depth range of 0 to 

1,236 meters. From survey data, most dogfish inhabit waters less than 350 meters deep. They occur 

from the surface and intertidal areas to greater depths, and are common in inland seas such as San 

Francisco Bay and Puget Sound and in shallow bays from Alaska to central California. Adult 

females move inshore to shallow waters during the spring to release their young. Small juveniles 

(<10 years old) are pelagic while subadults and adults are mostly sublittoral-bathyal. Subadults are 

found on muddy bottoms when not found in the water column. The proposed Siuslaw sites may 

provide suitable EFH for spiny dogfish.

Sablefish. Sablefish are an inner shelf-bathybenthal species that occurs in deep water. Sablefish are 

most abundant in depths from 200 to 1,000 meters but have been reported to depths of 1,900 meters. 

Spawning occurs at depths greater than 300 meters. Larvae and young juveniles are pelagic and may 

move inshore and remain there for up to 4 years to rear. Older juveniles and adults inhabit 

progressively deeper water and are benthopelagic on soft bottoms. Based on these habitat 

requirements, the proposed Siuslaw sites would not provide suitable EFH for sablefish.

Leopard Shark. Leopard sharks are found from southern Oregon to Baja California. This species is 

most abundant in northern California bays and estuaries and along southern California beaches. 

They are common in waters less than 20 meters deep and use estuaries and shallow waters for 

pupping and feeding/rearing grounds. Leopard sharks are associated with artificial structures such as 

piers and jetties and a variety of bottom habitats such as hard, mixed, unconsolidated, and vegetated 

bottoms. Based on these habitat requirements, the proposed Siuslaw sites would not provide suitable 

EFH for leopard shark. 

Soupfin Shark. Soupfin shark are an abundant coastal pelagic species that ranges from Canada to 

Mexico. They inhabit bays and muddy shallow water areas where they are associated with the 

bottom. They occur in depths from 2 to 471 meters. Adult males occur in deeper water in northern 

California, while females occur closer to shore in southern California. Juveniles are also more 

abundant in the southern portion of the range associated with the females. Juveniles also occur in 

bays such as San Francisco Bay to rear. Soupfin shark exhibit large coastal migrations; the 

population moves north in the summer and south in the winter. The proposed Siuslaw sites may 

provide suitable EFH for soupfin shark.

Pacific Hake. Pacific hake is a migratory species that inhabits the continental slope and shelf from 

Baja California to British Columbia. Juvenile hake usually reside in shallow coastal waters, bays, 

and estuaries with adults occurring further offshore, usually at depths from 50 to 500 meters. Along 

the Pacific Coast from British Columbia to California, adults use a narrow band of feeding habitat 

near the shelf break for 6-8 months per year. Based on these habitat requirements, the proposed 

Siuslaw sites would not provide suitable EFH for Pacific hake.

Coastal Pelagic Species EFH

The nearshore area off the Siuslaw River has the potential to provide EFH for northern anchovy 

(Engraulis mordax), Pacific sardine (Sardinops sagax), Pacific (chub) mackerel (Scomber 

japonicus), jack mackerel (Trachurus symmetricus), and California market squid (Loligo 

opalescens). The EFH for the four coastal pelagic fish species is the water column except for the 

market squid, which spawns in specific spawning grounds on the bottom. The proposed Siuslaw

sites may provide suitable EFH for these four pelagic fish species.
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

38

Market squid range from Mexico to Alaska, although they are most abundant from Monterey Bay to 

Mexico. Although they are considered pelagic they actually occur from the surface to depths of 800 

meters. They prefer ocean salinities and are rarely found in bays, estuaries, or near river mouths. 

Squid spawn in dense schools on the bottom in spawning areas that range in depth from near shore 

shallow areas to depths of 800 meters. Known spawning areas are inshore protected areas with sand 

or mud bottoms at depths from 5 to 55 meters. Squid spawning off Oregon has been observed from 

May to July. No squid spawning areas have been identified in the vicinity of the proposed Siuslaw

sites. Consequently, the proposed Siuslaw sites do not provide suitable EFH for market squid.

Salmon Species EFH

The nearshore area offshore from the Siuslaw River has the potential to provide EFH for Chinook 

salmon (Oncorhynchus tshawytscha) and coho salmon (Oncorhynchus kisutch). The proposed 

Siuslaw sites may provide EFH for Chinook and coho salmon as a migratory area for adults and 

juveniles. 

Determination for Essential Fish Habitat

There is a potential to impact EFH for some flatfish species (arrowtooth and starry flounder; English, 

sand, butter, petrale, rock, and curlfin sole; and Pacific sanddab), big skate, spiny dogfish, Soupfin 

shark, four coastal pelagic fish species (northern anchovy, pacific sardine, pacific mackerel, and jack 

mackerel), and Chinook/coho salmon by use of the proposed North and South ocean disposal sites

near the Siuslaw River. The amount of habitat potentially impacted by site use, however, is expected 

to be very small compared to the total EFH habitat identified for each of the species evaluated. In no 

case does the habitat provided by the proposed Siuslaw sites represent any unique habitat that is 

limited in distribution. Therefore, although the designation of the Siuslaw sites may adversely affect 

EFH for the above listed species, those effects are expected to be minor and temporary and are not 

expected to reduce the quality and/or quantity in any significant way for any EFH for any of the 

species listed above. 

The following measures have been considered by EPA as a way to mitigate any adverse impacts to 

designated EFH at the proposed Siuslaw sites. EPA expects to incorporate these measures into the 

site management and monitoring plans for each of the proposed Siuslaw sites. 

1. Dredged material to be disposed at the Siuslaw North and South ocean disposal sites must 

determined to be suitable for unconfined, aquatic disposal. In the event that any dredged 

material is not suitable for unconfined, aquatic disposal, the dredged material found unsuitable 

will not be disposed at the Siuslaw ocean disposal sites, but will be placed at acceptable upland 

disposal sites.

2. Bathymetry at the Siuslaw North and South ocean disposal sites will be monitored on a regular 

basis to ensure that mounding is not occurring. 
Biological Assessment & Essential Fish Habitat Assessment, Proposed Siuslaw River ODMDS Designation

39

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