Siuslaw River, Oregon

Ocean Dredged Material Disposal Sites 

Evaluation Study and Environmental 

Assessment

U.S. Army Corps of Engineers, Portland District

U.S. Environmental Protection Agency, Region 10

April 2010
Abbreviations and Acronyms

CFR Code of Federal Regulations

cfs cubic feet per second

cy cubic yard(s)

CZMA Coastal Zone Management Act

DMEF Dredged Material Evaluation Framework

DPS Distinct Population Segment

EA Environmental Assessment

EFH essential fish habitat

EPA U.S. Environmental Protection Agency

ESA Endangered Species Act

ESU Evolutionarily Significant Unit

km kilometers

m

3

cubic meter(s)

mg/kg milligrams per kilogram

mg/L milligrams per liter

mm millimeter(s)

MDL method detection limit

MLLW mean lower low water

MMPA Marine Mammal Protection Act

MPRSA Marine Protection, Research and Sanctuaries Act

MRL method reporting limit

MSA Magnuson-Stevens Fishery Conservation and Management Act

NAD North American Datum

NEPA National Environmental Policy Act

NHPA National Historic Preservation Act

NMFS National Marine Fisheries Service

OC Oregon Coast (coho salmon)

ODMDS ocean dredged material disposal site

ODFW Oregon Department of Fish and Wildlife

OHV off-highway vehicle

PAH polynuclear aromatic hydrocarbon(s)

PCB polychlorinated biphenyl(s)

ppb parts per billion

ppm parts per million

RM river mile(s)

SEF Sediment Evaluation Framework

SMMP Site Management and Monitoring Plan

SONCC Southern Oregon/Northern California Coast (coho salmon)

TOC total organic carbon

TBT tributyltin

ug/g microgram per gram

ug/kg micrograms per kilogram

ug/L micrograms per liter

USACE U.S. Army Corps of Engineers

U.S.C. United States Code

ZSF Zone of Siting Feasibility
Siuslaw River, Oregon

Ocean Dredged Material Disposal Sites

Evaluation Study and Environmental Assessment

Report Preparers

Wendy K. Briner Biologist CENWP-PM-E

Mark D. Siipola Civil Engineer CENWP-EC-HR

Timothy J. Sherman Biologist CENWP-EC-HR

Kim W. Larson Fishery Biologist CENWP-PM-E

Bert Rader Archaeologist CENWP-PM-E

Michael A. Martin Archaeologist CENWP-PM-E

Jonathan Freedman Ocean Dumping Coordinator EPA, Region 10

Jessica Winkler Biologist EPA, Region 10

Justine Barton Ecologist EPA, Region 10

Karen Bahus Biologist/Writer Consultant
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page i

Siuslaw River, Oregon

Ocean Dredged Material Disposal Sites

Evaluation Study and Environmental Assessment

Table of Contents

PURPOSE AND NEED..........................................................................................................1

Need for Disposal Site Designation....................................................................................1

Background.........................................................................................................................3

Offshore Designation and Disposal History .......................................................................4

AFFECTED ENVIRONMENT..............................................................................................7

Physical Resources..............................................................................................................7

General ...........................................................................................................................7

Siuslaw River Sediments.................................................................................................7

ODMDS Sediments .........................................................................................................9

Oceanographic Circulation ..........................................................................................11

Surficial Geology ..........................................................................................................11

Water Quality................................................................................................................11

Biological Resources ........................................................................................................12

Plankton and Fish Larvae.............................................................................................12

Benthic Invertebrates....................................................................................................13

Fish and Epibenthic Species.........................................................................................14

Commercial and Recreational Fisheries......................................................................14

Wildlife..........................................................................................................................15

Threatened and Endangered Species............................................................................15

Socio-Economic Resources ..............................................................................................16

Cultural Resources........................................................................................................16

Recreational Uses.........................................................................................................16

Commercial Uses..........................................................................................................17

ANALYSIS OF ALTERNATIVES......................................................................................17

No Action Alternative.......................................................................................................18

Upland Disposal Alternative.............................................................................................18

Estuarine Disposal Alternative .........................................................................................18

Ocean Disposal Alternatives.............................................................................................19

Disposal Off the Continental Shelf ...............................................................................19

Continued Use of Existing Sites....................................................................................20

Designation of New ODMDS........................................................................................20

ANALYSIS OF OCEAN DUMPING SITE DESIGNATION PROCESS AND 

ENVIRONMENTAL EFFECTS ..........................................................................................21

Overview...........................................................................................................................21

Defining a Zone of Siting Feasibility................................................................................21

Siuslaw River Zone of Siting Feasibility..........................................................................22
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page ii

Regulatory Criteria for Ocean Disposal Site Selection.....................................................23

Application of Four General Criteria (40 CFR 228.5).................................................23

Application of Eleven Specific Factors (40 CFR 228.6)...............................................29

SUMMARY OF COORDINATION UNDER OTHER APPLICABLE FEDERAL

STATUTES...........................................................................................................................37

Federal Action...................................................................................................................37

Public Comments..............................................................................................................37

Endangered Species Act ...................................................................................................37

Magnuson-Stevens Fishery Conservation and Management Act .....................................39

Marine Mammal Protection Act .......................................................................................39

Coastal Zone Management Act.........................................................................................40

National Historic Preservation Act ...................................................................................40

Tribal Consultation ...........................................................................................................40

SELECTION OF OCEAN DISPOSAL SITES FOR FORMAL DESIGNATION .............40

LITERATURE CITED .........................................................................................................41

List of Tables

Table 1. Siuslaw River Project Dredging Volumes...............................................................5

Table 2. Proposed Siuslaw North and South ODMDS Conflict Matrix..............................24

List of Figures

Figure 1. Siuslaw River Proposed North ODMDS and South ODMDS ...............................2

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

Figure 3. Siuslaw Ocean Disposal Sites Sampling Locations, 2008 ...................................10

Figure 4. Overlay Evaluation of Individual Resources........................................................27

Technical Appendices

Appendix A – Living Resources

Appendix B – Physical Processes and Geological Features

Appendix C – Sediment and Water Quality

Appendix D – Cultural Resources

Appendix E – Recreational Resources

Appendix F – Site Management/Monitoring Plan
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 1

PURPOSE AND NEED

This Ocean Dredged Material Disposal Site (ODMDS) Evaluation and Environmental 

Assessment (EA) was jointly prepared by the U.S. Army Corps of Engineers (USACE) and the 

U.S. Environmental Protection Agency (EPA). The purpose of this evaluation is to provide 

documentation in support of final EPA designation of two ODMDS (North and South) located 

offshore from the Siuslaw River, Oregon (Figure 1). These sites are needed for long-term use by 

the USACE for the federally authorized Siuslaw River navigation project and for use by others 

for disposal of dredged material meeting ocean disposal criteria. This evaluation will assess the 

proposed final designation of the two Siuslaw sites against the statutory requirements set forth in 

the Marine Protection, Research and Sanctuaries Act, as amended (MPRSA), 33 U.S.C. 1401 to 

1445, and the regulations found in Part 228 of Title 40 of the Code of Federal Regulations 

(CFR). These regulations were promulgated in accordance with criteria set out in Sections 102, 

103 and 104 of the MPRSA. This evaluation also outlines EPA’s coordination under the 

National Environmental Policy Act of 1969 (NEPA), 42 U.S.C. Sections 4321 to 4370f; 

Endangered Species Act of 1973 (ESA), 16 U.S.C. Sections 1531 to 1599; Magnuson-Stevens 

Fishery Conservation and Management Act (MSA), 16 U.S.C. Sections 1801 et seq.; Marine 

Mammal Protection Act of 1972 (MMPA), 16 U.S.C. Sections 1361 et seq.; National Historic 

Preservation Act of 1966 (NHPA), 16 U.S.C. Sections 470 et seq.; and the Coastal Zone 

Management Act of 1972 (CZMA), 16 U.S.C. Sections 1451 to 1466, all as amended.

Need for Disposal Site Designation

The EPA undertook this evaluation to determine whether to designate any dredged material 

disposal site(s) near the mouth of the Siuslaw River pursuant to its authority under the MPRSA 

at Section 102(c) in response to several factors. These factors include:

1. The prohibition on further use of the existing Siuslaw Section 103 disposal sites

following the close of the 2009 dredging season pursuant to USACE site selection 

authority under MPRSA Section 103(b), which allows the USACE to select a site under 

Section 103 for a period of 5 years with a maximum 5-year extension with EPA 

concurrence;

2. The understanding that in the absence of an EPA-designated disposal site or sites, any 

necessary open-water disposal would either be precluded or the USACE would have to 

undertake additional short-term site selections, perhaps a number of them, in the future;

3. The clear Congressional preference expressed in MPRSA Section 103(b) that any openwater disposal of dredged material take place at EPA-designated sites, if feasible; and

4. The statutory preference to concentrate, where feasible, any open-water disposal at sites 

that have been used historically, see 40 CFR 228.5(e).
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 2

Figure 1. Siuslaw River Proposed North ODMDS and South ODMDS
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 3

The EPA’s evaluation considered whether there was a need for any disposal site designations for 

long-term dredged material disposal, including an assessment of whether other dredged material 

management methods and/or disposal options could reasonably be judged to obviate the need for 

such designations. Having concluded that there was a need for open-water disposal sites, EPA 

then assessed whether there were sites that would satisfy the applicable environmental criteria to 

support a site designation under the MPRSA Section 102(c).

Background

The MPRSA was passed by Congress in recognition of the fact that the disposal of material into 

ocean waters could potentially result in unacceptable adverse environmental effects. Under the 

MPRSA, the EPA and the USACE were assigned responsibility to regulate the dumping of 

dredged material into ocean waters and to prevent or strictly limit the dumping into ocean waters 

of any material that would “unreasonably degrade or endanger human health, welfare, or 

amenities, or the marine environment, ecological systems, or economic potentialities.”

The EPA administers and enforces the overall permit program for ocean disposal of material 

other than dredged material and designates dredged material disposal sites. The USACE, with 

EPA’s concurrence, issues permits for the disposal of dredged material for the purpose of ocean 

disposal where the USACE determines that dumping will not unreasonably degrade the 

environment or endanger human health, welfare, or amenities, or the marine environment, 

ecological systems, or economic potentialities. While the USACE does not administratively

issue itself a permit, the requirements that must be met before dredged material derived from 

USACE projects can be disposed into ocean waters are the same as those where a permit would 

be issued.

The EPA must consider statutory criteria and evaluate the four general regulatory criteria 

codified at 40 CFR§ 228.5 and the eleven specific regulatory criteria at 40 CFR § 228.6. 

Pursuant to Section 102(c) of the MPRSA, the EPA is responsible for designating sites for the 

disposal of dredged material. The USACE is allowed, with EPA’s concurrence, to select a site 

for ocean disposal of dredged material pursuant to Section 103(b) and (c) of the MPRSA, when a 

feasible disposal site has not been designated by EPA, or when the continued use of an 

alternative site is necessary to maintain navigation and facilitate interstate or international 

commerce, and EPA has determined that the alternative site does not pose an unacceptable risk 

to human health, aquatic resources, or the environment.

An EPA-designated site requires a site management and monitoring plan (SMMP). Use of a 

designated site is subject to the restrictions included in the SMMP and EPA’s designation 

regulations. These restrictions are based on an in-depth evaluation of the site and potential 

disposal activity, as well as public review and comment.

Designation of an ODMDS in itself does not result in disposal of dredged material. A separate 

evaluation of the suitability of dredged material for ocean disposal must be undertaken for each 

proposed use of the site by either the USACE or non-USACE permit applicant. Typically, this 

involves evaluation of the specific disposal activity under the criteria (which can include 

multiple years of use), circulation of a public notice, specific coordination with stakeholders, and 

concurrence by the appropriate EPA region.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 4

The EPA proposes to designate two ocean disposal sites, the North ODMDS and South ODMDS, 

which are located approximately 1 mile offshore of the entrance to the Siuslaw River (see Figure 

1). The proposed North site is 4,800 feet by 2,000 feet, and, based on 2009 bathymetric data, 

ranges from 30 to 115 feet deep. The proposed South site is 3,000 feet by 2,000 feet and ranges 

in depth from 80 to 120 feet deep. 

Offshore Designation and Disposal History

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 Siuslaw bar and entrance 

channel. The Interim ODMDS (Interim Site A on Figure 2) was designated an EPA Interim Site 

in 1977 (40 CFR 228.12) and was used from 1977 to 1996. 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. To address these issues, two 

adjusted and expanded ocean disposal sites, ODMDS B and C, were selected by the USACE 

under Section 103 of the MPRSA (Figure 2, Sites B and C). Site B includes a portion of Interim 

Site A. Material removed from the Siuslaw federal navigation project was first deposited at Site 

C in 1997, while Site B was first used in 1999. Since 1997, material removed from the Siuslaw 

federal navigation project has only been deposited into ODMDS B and C (see Table 1).

Sites B and C experienced some mounding even though disposal restrictions were used to 

enhance dispersal. The Interim Site A vicinity of Site B was avoided until previously placed 

materials could disperse. As a result of the larger sites, reduced overall volumes of dredging and 

disposal, and avoidance of the Interim Site A corner, all disposal restrictions were lifted in 2008. 

Pending final designation by EPA, in 2004 the USACE extended the selection of ODMDS B and 

C for a final 5-year period. Following expiration, the EPA must designate ocean disposal sites 

under Section 102 of the MPRSA in order for dredged material to be disposed offshore of the 

Suislaw River. 

Table 1 presents the volume of material placed offshore of the Siuslaw River. The bulk of the 

material dredged has been placed in the larger Site B. Quantities of dredging overall have 

dropped and future dredged material disposal volumes are not often expected to exceed 100,000 

cubic yards (cy) annually (based on a 13-year average of about 60,000 cy and a range of 22,300-

117,300 cy). Material is expected to be disposed over a period of 20 days of dredging and 

disposal (average is about 7 days; range 3-23 days). Generally, dredging and disposal are 

expected to occur between June 1 and October 31 of each year.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 5

Figure 2. Historical Siuslaw River Ocean Disposal Sites
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 6

Table 1. 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 (Site C)

1998 69.6 (Site C)

1999 43.5 (Site B)

2000 55.1 (Site C)

2001 101.2 (Site C)

2002 117.3 (Site B)

2003 55.0 (Site B)

2004 14.1 (Site B) & 9.0 (Site C)

2005 33.4 (Site B)

2006 22.3 (Site B)

2007 76.0 (Site B)

2008 69.9 (Site B)

2009 91.7 (Site B)

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

At other ocean disposal sites along the Oregon Coast, the EPA and the USACE 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. Similarly, EPA is proposing two expanded ocean disposal 

sites located North and South of the mouth of the Siuslaw River. Generally, material placed 

deeper than 60 feet is less mobile and less available to the active littoral system. To keep more 

material in the active littoral system, EPA proposes a North site configuration that expands the 

existing Section 103 Site B to include the original 1977 Interim site (Site A), and a similar 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 7

relatively “shallow” area to the north of Site A (see Figure 2). Based on likely northerly 

movement of coastal littoral material over the course of the yearly dredging and disposal cycle, 

the EPA proposes to utilize the shallower portions of the North site to the maximum extent 

possible in order to disperse material into the active littoral zone, limit wave effects due to 

mounding, and keep material from reentering the navigation channel to the south. The proposed 

South site’s southern boundary was moved further south, doubling the size of the site, to allow 

for better dispersal should that site be needed. To support annual adaptive management of the 

sites, EPA anticipates annual bathymetric surveys and other management and monitoring at the 

proposed North and South sites in accordance with the Site Management and Monitoring Plan 

(SMMP) (see Appendix F). 

AFFECTED ENVIRONMENT

Physical Resources

General

This section provides a summary characterization of the physical resources in the Siuslaw River 

study area. Additional information is provided in Appendix B: Physical Processes and Geologic 

Features. 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.

Siuslaw River Sediments

This section provides a summary characterization of the sediments to be dredged from the 

Siuslaw River. Additional information is provided in Appendix C. In 1991, the USACE 

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 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 8

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 these samples would meet the marine screening level guidelines 

established in the Sediment Evaluation Framework (SEF 2009)1for 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 the federal channel by the fuel dock. Pore-water TBT was not analyzed due 

to insufficient pore-water 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 to evaluate material proposed 

for dredging. The analytical results of this characterization are consistent with historical data. 

 

1

Pursuant to the Ocean Dumping Regulations at 40 CFR § 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 provides an additional safeguard for material that would otherwise meet the regulatory criteria for 

environmentally acceptable material for ocean dumping without further testing.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 9

Sediment represented by these samples met the marine screening levels guidelines established in 

the SEF for unconfined in-water placement without further characterization.

Sediments were collected in October 2006 from the Port of Siuslaw marina and from the upper 

river channel (RM 5 to 16.5). These samples are considered representative of the material from 

these areas, though dredging above RM 5 is very infrequent. Sediment from the Port’s marina 

ranged in grain-size from 47.3% to 79.4% sand (mean 75.9%), while sediment from the upper 

river channel ranged from 93.6% to 97.0% sand (mean 95.4%). Sixteen samples were submitted 

for physical testing and eight samples (two upstream and six marina) were subjected to chemical 

analysis, including metals, PCB’s, pesticides, chlorinated hydrocarbons, miscellaneous 

extractables, phthalates, phenols, and low and high molecular weight PAH’s. The six marina 

samples were also tested for bulk and porewater TBT. Some samples contained low levels of 

several COC’s, however, none approached their DMEF/SEF screening levels, with all laboratory 

detection levels and quality controls at acceptable levels. 

ODMDS Sediments

This section provides a summary characterization of the sediments in the ocean environment 

offshore of the Siuslaw River. Additional information is provided in Appendix C. 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/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. No detected metal values approached their 

respective SEF marine 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). Detection levels for technical chlordane 

were problematic, with non-detects reported at levels above the SEF marine screening levels. 

These values were not supported by the values found for alpha and gamma chlordane where 

levels separately and additively were well below the SEF marine SL. In addition, the estimated 

and non-detect values are all below the SL of 10 ug/kg currently used for decision-making in 

Puget Sound (where total chlordane is defined as the sum of cis-chlordane, trans-chlordane, cisnonachlor, trans-nonachlor and oxychlordane). Other than chlordane, all other pesticide values 

were below method reporting levels and well below SEF marine screening levels. No PCBs 

were detected.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 10

Figure 3. Siuslaw Ocean Disposal Sites Sampling Locations, 2008

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 below their respective SEF marine 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 marine screening levels.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 11

Oceanographic Circulation

Coastal circulation offshore of the Siuslaw River is directly influenced by large-scale regional 

currents and weather patterns in the northwestern Pacific Ocean. During winter, strong lowpressure systems with winds and waves predominantly from the southwest, initiate strong 

northward currents. During summer, high-pressure systems dominate and consequently, waves 

and wind 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 which creates a mass transport of water offshore resulting in upwelling of bottom water 

nearshore. 

In 1985 (see Appendix B), monitoring of currents in the Siuslaw nearshore area showed that 

summer currents were more frequently to the north and were generally the stronger currents. 

There were onshore-offshore currents during the summer with speeds equal to or greater than 1 

foot/second. Bottom currents in the winter had a strong offshore component. The largest 

percentage of the winter currents was to the north with the majority of the speeds equal to or 

greater than 1 foot/second. Appendix B provides details of the sediment transport processes for 

the Siuslaw River and nearshore area.

Surficial Geology

The geological data collected in 2008 for the ODMDS area showed the mean value for a grainsize of sand was 97.25% with a mean value of 3.71% fine-grained material. Sediments dredged 

from the Siuslaw River entrance channel are similar to the offshore sediments. Grain-size 

analyses for these sediments in 2006 resulted in mean values of 0.2% gravel (shell hash, 0.0% -

0.5% range), 97.1% sand (95.4% - 98.5% range), and 2.7% silt/clay (1.5% - 4.1% range).

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. 

In the summer of 2002, oxygen levels in the water near the Oregon coast plunged so low that 

fishes, crabs, and other marine organisms had to flee or die in the suffocating waters (PISCO 

2009). These low oxygen conditions, commonly called hypoxia, had never been documented in 

Oregon prior to 2002, but have recurred every summer since. The most severe event occurred in 

the summer of 2006 when oxygen levels dropped to historic lows and hypoxic water could be 

found in large areas along the Washington and Oregon coasts. In 2006, the dead zone lasted 4 

months and large areas of the coastal ocean were affected by oxygen levels that dropped as low 

as zero. It is normal to find naturally low-oxygen conditions in deep, offshore waters, e.g., at the 

edge of the continental shelf and slope. However, the occurrence of low-oxygen water close to 

shore (the inner shelf, less than 165’ of water) is highly unusual and had not been reported prior 

to 2002, despite over 50 years of scientific observations along the Oregon coast. No evidence of 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 12

impacts due to hypoxia have been documented in over 34 years of studies at the various 

ODMDSs off the Oregon coast.

Biological Resources

This section summarizes biological conditions in the ocean environment offshore of the Siuslaw 

River. Additional information is provided in Appendix A.

Plankton and Fish Larvae

No specific data is available for zooplankton in the Siuslaw River nearshore area. However, 

Keister and Peterson (2003) provided a discussion of the zooplankton community found off the 

central Oregon Coast (along the Newport hydrographic line). They indicated that the 

zooplankton community is influenced strongly by seasonal variations in wind and current 

patterns. During late spring and summer, northwesterly winds set up flow towards the equator 

and coastal upwelling. Northwesterly winds dominate from April/May-September; periodic 

relaxations or southwesterly storms rapidly affect the hydrograph of nearshore areas. During this 

time period conditions about 30 kilometers (km) offshore are less variable. Boreal neritic 

copepods such as Pseudocalanus mimus, Calanus marshallae, Centropages abdominalis, Acartia 

longiremis, and Acartia hudsonica dominate the coastal plankton during summer (Peterson and 

Miller 1977). In early fall, winds reverse and upwelling ceases; during autumn and winter, 

winds are predominantly southwesterly, the Davidson Current flows toward the pole, and 

offshore surface waters are transported onshore. In winter, the coastal zooplankton is populated 

by warm-water species such as Mesocalanus tenuicornis, Paracalanus parvus, Ctenocalanus 

vanus, Clausocalanus spp., Acartia tonsa, and Corycaeus anglicus (Peterson and Miller 1977).

Auth and Brodeur (2006) examined ichthyoplankton off the central Oregon Coast (along the 

Newport hydrographic line). The dominant taxa collected were northern anchovy (Engraulis 

mordax), slender sole (Lyopsetta exilis), rockfishes (Sebastes spp.), northern lampfish 

(Stenobrachius leucopsarus), and blue lanternfish (Tarletonbeania crenularis). Total larval 

concentration increased from 49.3 per 1,000 cubic meters (m3) in 2000 to 72.0 per 1,000 m3in 

2002, with seasonal concentrations highest in August 2000 (90.3 per 1000 m3) and April 2002 

(151.2 per 1,000 m3). Relatively few larvae were found at depths greater than 100 meters, while 

highest larval concentrations generally were observed from depths of 0 to 50 meters. Larval 

diversity and concentration were higher offshore (46-84 km off the coast) than in nearshore areas 

(9-28 km off the coast). Highest concentrations were normally found at an intermediate station, 

approximately 65 km off the coast. Species designated as either coastal or offshore species by

previous studies were predominantly found in their respective shelf regions. Most larval 

concentrations were positively correlated with temperature and negatively correlated with 

salinity.

Auth and others (2007) examined the ichthyoplankton assemblages from a single station 69 km 

off Heceta Head on the central Oregon Coast. The authors noted that the species composition, 

assemblages, and dominant taxa were similar to those found in other studies conducted in this 

area during summer (Richardson 1973; Richardson and Pearcy 1977; Brodeur et al., 1985; Auth 

and Brodeur 2006). This similarity provided evidence to support the hypothesis of Auth and 

Brodeur (2006) that past sampling along the Newport hydrographic line during summer is 

representative of ichthyoplankton assemblages elsewhere along the Oregon Coast.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 13

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/m2 was 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 August and September 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 the proposed Siuslaw ocean disposal sites. 

The benthic invertebrate fauna in the vicinity of the proposed sites was found to be typical of the 

nearshore, high-energy environment found along the Oregon Coast. The density distribution 

data indicated 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 the 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 Siuslaw nearshore area is typical of the communities found near other ocean 

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

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 that help stabilize the marine sediments. Many of the benthic species in 

the area are able to survive in this dynamic environment being either very mobile or being able 

to react both to natural or man-made perturbations. The benthic community would be expected 

to re-colonize within a period of a few weeks to months after disposal (USACE 1993).
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 14

Fish and Epibenthic Species

Commercially and recreationally important epibenthic species in the Siuslaw nearshore area are 

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 in 

this area. 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 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 20-50 meters (USACE 1992).

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

salmon, winter steelhead, and spring and fall Chinook salmon, 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 nearshore 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.

Commercial and Recreational Fisheries

Based on data from NMFS (2006) for commercial fishing, a total of 38 commercial vessels 

delivered landings to Florence in 2000. Landings were in the following West Coast fisheries 

(data shown represents landings in metric tons/value of landings/number of vessels landing): 

crab (112.8/$562,057/10), groundfish (124.3/$442,781/15), highly migratory species 

(6.9/$11,712/5), salmon (29.7/$113,885/22), shrimp (35.7/$28,529/5), and other species 

(1.5/$6808/5). There were no fish processors operating in Florence in 2000. A total of 41 

commercial vessels were owned by Florence residents in 2000, 19 of which participated in the 

federally managed groundfish fishery. Recreational fishing takes place in the same general areas 

as the commercial fishery but usually closer to shore. For the port complex around Florence, the 

2000 recreational salmonid catch in the ocean boat fishery was 250 Chinook salmon and 472 

coho salmon. The recreational non-salmonid catch was a total of 213 fish. The top species 

landed, in order, included greenstripe, canary, and yelloweye rockfish, and Pacific halibut.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 15

Wildlife

Steller sea lions, harbor seals, and California sea lions are present most of the year in the Siuslaw 

nearshore area. Steller sea lions forage at river mouths and nearshore areas along the Oregon 

Coast. Harbor seals breed in the estuary and on nearshore rocks. The Siuslaw nearshore area 

and shoreline provides important habitat for shorebirds, waterfowl, herons, bald eagles, hawks, 

and many other species of birds. Pelagic birds (e.g., murres, auklets, cormorants) are likely to 

use the area near the proposed Siuslaw ocean disposal sites and adjacent waters for foraging.

Threatened and Endangered Species

Oregon Coast (OC) coho salmon is a federally threatened species that may be present in the 

vicinity of the proposed Siuslaw ocean disposal sites. The Siuslaw River and estuary are 

designated as critical habitat for this species, but the ocean area off the Siuslaw River is not 

designated critical habitat. Coho salmon are present in the vicinity of the proposed ocean 

disposal sites as both adults and juveniles. Adults hold in the offshore area prior to entering the 

estuary to migrate up river to spawn. Juveniles rear in the nearshore ocean area after migrating 

downstream and transitioning to saltwater. Upstream migration of adult coho salmon generally 

takes place from August through November. Juvenile outmigration extends from April through 

June, but peaks in May.

The Southern Oregon/Northern California Coast (SONCC) coho salmon is also federally

threatened and includes all naturally spawned populations of coho in coastal streams between 

Cape Blanco, Oregon, and Punta Gorda, California. The proposed Siuslaw ocean disposal sites 

are not located within designated critical habitat for SONCC coho. This coho species typically 

migrates north along the coast. While migrating individuals may utilize the coastal habitat off of 

the Siuslaw River for migratory purposes, they are likely to be further offshore than the proposed 

ocean disposal sites.

The Southern Distinct Population Segment (DPS) of green sturgeon (Acipenser medirostris) is a 

federally threatened species. Critical habitat has been designated for the species (74 FR 52300, 9 

October 2009). Green sturgeon that spawn to the north, primarily in the Klamath and Rogue 

rivers, constitute the Northern DPS, which is not federally listed. These two DPSs for sturgeon 

were established because they were genetically distinct. Southern DPS green sturgeon may be 

observed in the vicinity of the proposed ocean disposal sites offshore of the Siuslaw River as 

they migrate to northern estuaries during summer and early fall.

The Southern DPS of Pacific Eulachon was proposed threatened in March 2009. Eulachon 

(commonly called smelt, candlefish, or hooligan) are a small, anadromous fish from the eastern 

Pacific Ocean. Eulachon typically spend 3-5 years in saltwater before returning to freshwater to 

spawn from late winter through mid spring. Eulachon occur in nearshore ocean waters and to 

1,000 feet 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 

where eulachon have been documented include the Sacramento River, Russian River, Humboldt 

Bay and several nearby smaller coastal rivers, and the Klamath River in California; the Rogue 

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 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 16

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.

Federally listed avian species that may be present in the Siuslaw offshore area include the 

marbled murrelet, brown pelican, and short-tailed albatross. Threatened marbled murrelets are 

observed in small flocks or as individuals in the ocean throughout the year. Endangered brown

pelicans are abundant from June to September along the coast and in the lower reach of the 

Siuslaw River estuary. The endangered short-tailed albatross may forage in open ocean areas off 

the coast, however the normal range for this species is Alaska and sightings are rare along the 

Oregon coast.

Two shoreline areas in Lane County support breeding and wintering western snowy plovers 

(Charadrius alexandrinus nivosus), a federally threatened species (USFWS 2007). These 

shoreline areas are Heceta Head to the Siuslaw River, and the Siuslaw River to the Siltcoos 

River. These shoreline areas fall outside the limits of the Siuslaw River project and would not be 

affected by ocean disposal activities.

The blue, fin, sei, sperm, humpback, and southern resident killer whales are all federally

endangered and have been observed as migrants off the coast in waters typically farther from 

shore than within the proposed Siuslaw ocean disposal sites. Threatened Steller sea lions are 

year-long residents and forage at the river mouth and nearshore areas along the coast. The 

proposed ocean disposal sites are not located in or near designated critical habitat for the Steller 

sea lion.

Socio-Economic Resources

The City of Florence is bordered by both the Pacific Ocean and Siuslaw River. The 2000 Census 

reported that Florence had a total population of 7,263 people, a 40.7% increase from the 1990 

Census. Based on the 2000 Census, highest employment in Florence was in educational, health 

and social services (22.9%), followed by accommodation and food services (16.6%), retail trade 

(16.1%), government (12.1%), and agriculture, forestry, fishing, and hunting (3.8%).

Cultural Resources

Appendix D provides detailed information concerning cultural resources offshore of the mouth 

of the Siuslaw River. Prehistoric cultural resources are unlikely to be found within the Siuslaw 

River offshore area. Shipwrecks are the most probable cultural resources to be expected within 

the offshore area. A review of the historical records indicates several recorded shipwrecks in the 

Siuslaw offshore area (see Appendix D). Side-scan sonar surveys were conducted in the area, 

and no shipwrecks or other historic remnants were detected. Based on the studies and research 

in Appendix D, there are no known shipwrecks offshore of the mouth of the Siuslaw River.

Recreational Uses

Recreational resources in the area of the proposed Siuslaw River ocean disposal sites are 

described in Appendix E. Although the Siuslaw River area receives recreational use year-round, 

the most popular months are from May through October. Fishing in the area is particularly 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 17

popular because of the excellent fishing opportunities in the Siuslaw River and nearby freshwater 

lakes. Other recreational activities include camping, picnicking, beachcombing, and sightseeing.

The Siuslaw River marks the northern boundary of the Oregon Dunes National Recreation Area. 

This portion of the recreation area contains no developed facilities other than a paved road that 

parallels the shoreline and provides access to the beach and South Jetty area. During the 

summer, beachcombing and sightseeing are the most popular activities. The Siuslaw jetty 

fishery is popular and accounts for a relatively high number of angler use days. The jetties are 

among the best in the state for catching surf perch. The most popular season is May through 

September. Scuba diving is another activity which occurs on the outside of both jetties. The 

main attraction for divers is the opportunity for spear fishing.

A locally important salmon fishery exists offshore of the Siuslaw River. Even though the 

offshore salmon fishing can be productive, a rough bar has periodically limited this opportunity

for most small pleasure craft. Salmon fishing is most popular from May through September 

when ocean conditions are more predictable and salmon are feeding in the nearshore area prior to 

the fall spawning runs.

A smooth bottom offshore of the Siuslaw River has limited the establishment of any substantial 

bottom fish populations. One exception is a small area located just off the mouth which has 

proven productive for flounder fishing. The lack of good bottom fishing opportunities and the 

relatively short salmon fishing season have limited the number of charter boats in the area.

Commercial Uses

The Siuslaw River offshore area supports a moderate commercial fishery primarily for salmon, 

groundfish, and Dungeness crabs. Clams are commercially harvested in the estuary. The fishing 

and tourist industries are a primary source of income to the local economy. No significant 

mineral or petroleum deposits are known to exist in the vicinity of the proposed Siuslaw ocean 

disposal sites.

ANALYSIS OF ALTERNATIVES

A Section 102 site designation allows for long-term sustainable use with no specified time limit 

on the life of the site. Specific regulatory criteria and factors per the MPRSA are analyzed later 

in this document. 

The EPA and the USACE considered several alternatives for disposal of dredged material 

generated from the Siuslaw River navigation project and other projects with authorized users. 

Those alternatives included no action, upland disposal, and estuarine disposal. Alternatives 

considered for ocean disposal included disposal off the continental shelf, continued use of the 

existing ocean disposal sites, and/or designation of new sites. Although other users may require 

dredged material disposal options, the USACE navigation project is the largest and most regular 

source of dredged material in the vicinity. Since other potential, but smaller, users of the site 

would likely face many of the same constraints as the USACE in the disposal of dredged 

material, the discussion of alternatives focuses primarily on USACE navigational dredging. 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 18

No Action Alternative

Under the no action alternative, EPA would refrain from formal designation of any ODMDS for 

the placement of dredged material by the USACE or other authorized persons or entities. If EPA 

did not designate site(s), the USACE has the authority to select alternate sites under MPRSA 

Section 103. The substantive requirements for information and evaluation of a Section 103 site 

are similar to those of an EPA formal designation under Section 102, and site designation under 

Section 103 requires EPA concurrence. In addition, the use of a Section 103 site is limited to 5 

years with one possible 5-year extension. The present sites being used at Siuslaw River are 

Section 103 sites. At the end of the 2009 dredging season, both present sites will have reached 

the 10-year use restriction and will no longer be available for use. The no-action alternative 

would not meet the project purpose, which is to provide dredged material disposal capacity for 

long-term use by the USACE for the federally authorized Siuslaw River navigation project and 

disposal capacity for other potential users. Therefore, the no action alternative was judged by 

both the USACE and EPA to be unacceptable and was dropped from further consideration.

Upland Disposal Alternative

Hopper dredges are self-propelled, seagoing vessels and are the only equipment that can be used 

to dredge the navigation channel because they can move quickly to minimize interference with 

navigation traffic and can adjust to rapidly changing weather and sea conditions. Because 

hopper dredges stockpile dredged material on-board and are designed to bottom dump that 

material, they are most efficiently utilized in conjunction with an in-water disposal area. 

Rehandling of material, moving it from the hopper dredge to another location for disposal, 

introduces an additional cost and logistical component to the process. To dispose of material 

from a hopper dredge to a land-based disposal site would necessitate dredging an in-water sump 

in the estuary, bottom dumping the dredged material from the hopper dredge into the in-water 

sump, and then pumping the material ashore with a pipeline suction dredge. Aside from 

increased costs, this approach would have additional adverse environmental impacts associated 

with the dredging of an in-water estuarine site to be used as the sump. Estuarine sites are both 

highly valued and limited (see below for additional discussion). In addition, a significant 

adverse impact of upland disposal is that naturally occurring sediments would be removed from 

the littoral system. For the purposes of this analysis, regular upland disposal of Siuslaw River 

entrance material is not considered feasible due to the economic and environmental effects 

resulting from nearshore rehandling of dredged material.

Estuarine Disposal Alternative

Estuarine habitat is limited and environmentally sensitive. Placement of dredged material in 

estuarine areas is generally only environmentally acceptable for specific beneficial uses, such as 

in areas where substrate is eroding and the dredged material would be suitable (e.g., fine-grained 

and clean) to supplement existing substrate. In general, disposal of dredged material in estuaries 

would result in greater adverse environmental impacts than disposal in the ocean due to both the 

limited abundance and high productivity of estuaries relative to nearshore oceanic habitats. 

Disposal of material into the estuary would also increase the risk of the material eroding and 

reshoaling in the channel, potentially increasing dredging frequency and/or volumes.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 19

There are operational constraints to estuarine disposal as well. Due to the narrow and shallow 

confines of the Siuslaw River estuary, no suitable estuarine disposal areas were identified that 

could be accessed by a hopper dredge and could accept the volume of material annually dredged 

from the Siuslaw River entrance channel.

Ocean Disposal Alternatives

Ocean disposal alternatives include disposal of the material off the continental shelf, continued 

use, by designation, of the existing Section 103 ocean disposal sites, or designation of a new 

ocean disposal site(s). In addition to general criteria and specific factors required for analysis by

MPRSA, at Siuslaw, EPA has site management criteria that will be applied when managing 

disposal at a designated site, and that help to inform the alternatives analysis. These include 

maximizing site capacity and lifetime by maximizing the volume of material that moves from the 

site into the natural nearshore littoral system; avoiding the potential for mounding and associated 

safety concerns (e.g. encouraging rapid dispersal); supporting safe and efficient site 

use/management and site monitoring logistics; and avoiding adverse effects to unique resources. 

Disposal Off the Continental Shelf

The MPRSA directs EPA to utilize, whenever feasible, locations beyond the edge of the 

continental shelf (Section 102(a)(I), 33 U.S.C. § 1412(a)(I)). This same directive is found in the 

regulations in the general criteria at 40 CFR § 228.5(e). Transporting dredged material off the 

continental shelf presents potentially significant environmental concerns. Benthic and pelagic 

ecosystems near the shelf contain important fishery resources and the effects of disposal 

operations on them are not well understood. Fine-grained sediment and rocky habitats would be 

directly impacted by disposal. These deep-water areas are stable and generally not disturbed by

wave action or sediment movement. Consequently, the benthic invertebrate communities in 

these deep, offshore environments are adapted to very stable conditions and would likely be less 

able to survive disturbance from the immediate impact of disposal and the long-term alteration of 

substrate type. Bottom gradients can be 5% to 25% on the continental slope, making 

accumulated unconsolidated sediments susceptible to slumping. Deposited sediments could be 

transported long distances both downslope, through turbidity currents, and offshore, by nearbottom currents, potentially affecting organisms outside of any designated site.

Disposal off the continental shelf would remove natural sediments from the nearshore Hecata 

Head littoral transport system, a system that functions with largely non-renewable quantities of 

sand in Oregon. While the loss of the present volumes of Siuslaw River dredged material is 

unlikely to result in disruption of the mass balance of the littoral system, the State of Oregon is 

already experiencing erosion/accretion patterns that are adversely impacting beaches, spits, 

wetlands, and other shoreline habitats. Consequently, keeping this material in the littoral system 

is perceived as a benefit and helps to sustain a dynamic equilibrium along the Oregon coast. 

An additional limiting factor in considering a location beyond the edge of the continental shelf is 

logistical feasibility. At and in the vicinity of the Siuslaw River, potential disposal areas located 

off the continental shelf would be at least 15 nautical miles offshore in water depths of 600 feet 

or greater. This distance is well beyond the reasonable haul distance of hopper dredges working 

the Siuslaw River project, which is discussed in greater detail in the discussion of the Zone of 

Siting Feasibility (ZSF). In addition, the feasibility of monitoring a site located off the 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 20

continental shelf is questionable, based on safety, cost, and time constraints correlated with 

increased distance from shore.

Given potential uncertain environmental concerns, coupled with the cost/logistical issues of both 

disposal and monitoring, disposal off the continental shelf is not a feasible alternative. 

Substantial additional investigation would be required to determine the scope of the possible 

environmental impacts of this alternative. Such an investigation is not warranted unless there are 

no suitable sites closer to shore.

Continued Use of Existing Sites

The two existing 103-selected Siuslaw ocean disposal sites (B and C) have been used for 

disposal of dredged material since 1997 (see Table 1 and Figure 2). Based on placement of 

dredged material between 1997 and 2009 at the sites prior to designation, approximately 800,000 

cy total have been placed, for a 13-year average annual loading volume of about 60,000 cy/year. 

Annual bathymetric surveys have shown the potential for mounding at the two previously

utilized Section 103 Sites B and C. Disposal restrictions, until lifted in 2008, were placed on the 

southeast corner of Site B which overlapped the much smaller original 1977 Interim Site A. 

Since there has been a history of mounding at all of the previously utilized Siuslaw ocean 

disposal sites, continued use of existing sites is not considered a viable alternative. 

Designation of New ODMDS

New ODMDS could be evaluated for designation in location(s) that incorporate the existing 

historical disposal sites, or a new disposal site could be designated in an entirely new location. 

EPA and the USACE prefer to continue use of the two existing historical sites because there is a 

clear regulatory preference for the designation of previously used sites (40 CFR 228.5(e)), and 

with expansion and adaptive management, they are anticipated to meet the goals for designation. 

In addition, EPA can utilize past monitoring and surveillance information from these sites for 

designation, and maintain continuity of monitoring, while extending the monitoring program to 

expansion areas. 

The EPA is proposing to increase capacity and minimize mounding by designating both a larger 

North and larger South ODMDS for the Siuslaw River. Generally, material placed deeper than 

60 feet disperses slowly, and is therefore removed from the active littoral system. To keep more 

material in the nearshore active littoral system, 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 

“shallow” (30’ to 60’ deep) area to the north of Site A, away from the river mouth. 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, and to promote dispersal of material from the 

site. The EPA acknowledges that previous studies showed the potential for material disposed 

within the southeastern portions of Site A to re-enter the channel. However, by allowing for 

adaptive management at an expanded North site, EPA and the USACE do not expect measurable 

volumes of dredged material to migrate back into the channel from the proposed North Site. In 

addition, the proposed South site’s southern boundary was moved to the south, away from the 

river mouth, doubling the size of the site. Continued management and monitoring of the new 

Section 102 North and South sites will take place in accordance with a Site Monitoring and 

Management Plan (see Appendix F).
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 21

ANALYSIS OF OCEAN DUMPING SITE DESIGNATION 

PROCESS AND ENVIRONMENTAL EFFECTS

Overview

Formal designation of ocean dumping sites is the responsibility of EPA as stated in the MPRSA. 

The process for site designation is found in the ocean dumping regulations at 40 CFR Part 228. 

The process followed by EPA, Region 10, and the USACE for the proposed Siuslaw River ocean 

disposal sites generally follows the site designation procedures developed by a joint task force of 

EPA and USACE personnel titled, General Approach to Designation Studies for Ocean Dredged 

Material Disposal Sites (EPA/USACE 1984).

The procedures utilize a hierarchical framework that initially establishes the broadest 

economically and operationally feasible area of consideration for site location. A step-by-step 

sequence of activities is then conducted to eliminate critical and/or unsuitable subareas. Further 

evaluation of alternative sites (candidate sites) within this area entails various levels of 

assessment as suggested by the sensitivity and value of critical resources or uses at risk, and 

potential for unreasonable adverse impact presented by the dredged material to be disposed. The 

site designation criteria at 40 CFR §§ 228.5 to 228.6 are applied to the information assembled 

through this process, and a final site or sites are selected and proposed for formal designation.

The MPRSA (33 U.S.C. 1401 to 1445) tasks EPA and the USACE with the joint obligation to 

ensure that ocean disposal will not “unreasonably degrade or endanger human health, welfare, or 

amenities, or the marine environment, ecological systems, or economic potentialities.” The 

EPA’s site criteria and joint EPA/USACE guidance are intended to result in the designation of an 

environmentally acceptable site, oriented toward avoidance of unreasonable degradation or 

endangerment of human health, welfare, or amenities, or the marine environment, ecological 

systems, or economic potentialities, which is operationally efficient. 

Defining a Zone of Siting Feasibility

At the outset, and pursuant to jointly developed guidance titled General Approach to 

Designation Studies for Ocean Dredged Materials Disposal Sites (EPA/USACE 1984), a 

geographic area of consideration referred to as a Zone of Siting Feasibility (ZSF) is a first step 

towards designating a site. According to the guidance, a reasonable distance of haul from the 

dredging site to the disposal site is the determining factor in establishing the ZSF, and will be 

affected by available dredging equipment, energy use constraints, costs, and safety 

considerations. The initial ZSF, once established, is evaluated according to the statutory and 

regulatory criteria under the MPRSA. Each of the criteria is overlain on the preliminary ZSF in 

sequence to eliminate unsuitable areas and determine the location and overall suitability of 

remaining sites, if any, within the ZSF that could be designated for the disposal of dredged 

material. If, based on that evaluation, a suitable site is not located within the initial ZSF, then the 

area of consideration must be expanded in order to ensure that a disposal site can be designated 

that will not unreasonably degrade or endanger human health, welfare, amenities, the marine 

environment, or ecological systems.

Although an ODMDS may be proposed for use and potentially utilized by any person or entity, 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 22

the primary anticipated user for the currently proposed Siuslaw ODMDS is the Corps, who is 

expected to use the site annually for disposal of dredged material from the Siuslaw River 

navigation project. No other potential users of the proposed Siuslaw ODMDS have been 

identified at this time. Therefore, the discussion of the ZSF below is based solely on the Corps’ 

anticipated disposal activities.

On the West Coast, weather and ocean conditions are major considerations and act as significant 

limiting factors when assessing the reasonable distance of haul. Rough seas and adverse weather 

conditions are the norm from October through May on the West Coast. These conditions act to 

limit ocean disposal of dredged material to a narrow window where it is generally safe to work 

from roughly the end of May to no later than mid-October, with a high probability of down time 

due to adverse weather at either end of that period.

The availability of dredging equipment is also a constraint that must be considered in the 

determination of a ZSF for a proposed ocean disposal site, but particularly so for sites on the 

West Coast of the United States. For most of the designated sites in Oregon, the USACE is the 

primary user and must confront equipment availability issues. The USACE evaluates the 

availability of Government or contract equipment annually and allocates the use of government 

dredges for the nation. Hopper dredges are mobile, can work in sea swell conditions up to 10 

feet, and are self-propelled. Therefore, they are generally the only feasible equipment for 

dredging most ocean entrance channel/bar situations.

Hopper dredge availability on the West Coast has been limited. Many hopper dredges working 

in the U.S. are often committed to other work on the Atlantic and Gulf of Mexico coasts and are 

not available to be used elsewhere, except perhaps on an emergency basis. As a result, there are 

typically three hopper dredges working on the West Coast that can be used safely at the Siuslaw 

River. These dredges must also maintain other projects in Oregon, Washington, California, and 

occasionally Hawaii and Alaska.

Siuslaw River Zone of Siting Feasibility

The 8-year average (2002-2009) for dredging at the Corps’ Siuslaw River navigation project is 

57,495 cy. The amount of time necessary to maintain a coastal project (exclusive of weather 

downtime) is a function of dredging a hopper full of material (loading), then transporting that 

material to, and placing it at, the disposal site(s). This is called “cycle time” and the cycle time 

can be different for each dredge. Loading time is essentially fixed based on the characteristics of 

the sediments being dredged, the dredge itself (i.e., pumps, size of hopper, drag arms, etc) and 

the dredging site conditions. The time to discharge material also is basically fixed for a given 

dredge and the type of material, but may vary slightly depending on the disposal methodology

outlined in the Site Management and Monitoring Plan (SMMP). The SMMP will direct disposal 

activities in such a manner to minimize mounding or other environmental effects at the ODMDS. 

Transport time depends primarily on the haul distance to the disposal site as the speed of 

different hopper dredges, when full, are similar. Thus, the critical element for new construction 

or maintenance dredging is the haul distance between the dredging site and the disposal site from 

both a time and cost perspective. A significant haul distance will affect the ability to construct or 

maintain the individual project and very probably would have repercussions on the Corps’ ability

to maintain other West Coast projects.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 23

Under current and foreseeable conditions at the project, the estimated volume of material to be 

removed annually is expected to remain near the current average of 57,495 cy. Based on 

workload, available funding, and other constraints, the Government-owned hopper dredge 

Yaquina is typically expected to be available 6.92 days (according to latest 8-year average) at the 

Siuslaw River navigation project, or a contract dredge is expected to be available for a similar 

length of time. This translates into an 8,309 cy per day average production requirement. The 

rated capacity for the Yaquina is 1,042 cy and the average load for the Siuslaw project is 1,002 

cy/load. Pump time typically is around 65 minutes for the Siuslaw project. Depending on the 

SMMP, environmental conditions, and characteristics of the dredged material, dump time could 

vary from 2 to 6 minutes. The dredge typically works 24 hours per day except for Tuesdays 

when the crew change occurs. The ZSF can be calculated as follows:

Assume 8.29 loads per day (8,309 cy/day  1,002 cy/load = 8.29 loads/day)

Pump time (1.085 hr) + Dump time (0.095 hr) = 1.18 hr/load x 8.29 loads or 9.79 hr/day

24 hr/day - 9.79 hr/day = 14.21 hr/day for transit to and from the disposal site

14.21 hr/day  8.29 loads/day = 1.71 hour transit time for one round trip

1.71  2 = 0.855 hr transit one way

0.855 x 6 kts (vessel speed) = 5.14 nautical miles

Thus, the outer limit of the ZSF for the Siuslaw ODMDS, as limited by the capacity of the 

available dredging plant, average annual dredging quantity, and limited dredging time period, is 

5.14 nautical miles from the Siuslaw River navigation project. This is the area within which 

potential sites will initially be evaluated according to the MPRSA statutory and regulatory

criteria.

Regulatory Criteria for Ocean Disposal Site Selection

The EPA evaluated the four general (40 CFR 228.5) and 11 specific (40 CFR 228.6) regulatory

criteria for site designation in reviewing the currently proposed Siuslaw River North and South 

ODMDS. A conflict matrix format is utilized in Table 2 to simplify and consolidate scoring for 

the general and specific site criteria review process. Each area of consideration on the conflict 

matrix addresses at least one general or specific criterion. A legend defining the matrix 

categories follows the table.

Application of Four General Criteria (40 CFR 228.5)

Minimize Interference with Other Activities (a.). The first of the four general criteria requires 

that a determination be made as to whether the proposed site or its use will minimize interference 

with other uses of the marine environment. This determination was made by overlaying 

individual uses with the resources presented in the Siuslaw Ocean Dredged Material Disposal 

Site Evaluation (USACE 1992) and the more recent appendices prepared for this evaluation. 

The report presented the overlays on a base map giving bathymetry and location of the previous 

ocean disposal sites in the ZSF. The more interactions between various uses and limited 

resources exist, the more critical the area. The overlay process was used to minimize 

interference with other uses of the ocean. The selection of features to use for this determination 

was dependent on whether the resource was considered limited.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 24

Table 2. Proposed Siuslaw North and South ODMDS Conflict Matrix

AREA OF

CONSIDERATION 1/

CONFLICT 2/POTENTIAL CONFLICTNO CONFLICTBENEFICIAL USE

COMMENTS

RELEVANT 

SPECIFIC 

FACTORS

11 Specific 

Factors 3/

(40 CFR 228.6)

RELEVANT 

GENERAL

CRITERIA

4 General 

Criteria 4/

(40 CFR 228.5)

1. Unusual Topography/Unique 

Bottom Features X 1, 6, 8, 11 a

2. Physical Sediment Compatibility X 3, 4, 9 b, d

3. Chemical Sediment 

Compatibility X Periodic monitoring conducted 3, 4, 7, 9 a, b, d

4. Influence of Past Disposal X Mounding due to past disposal 5, 7, 9, 10 a, b, d

5. Living Resources of Limited 

Distribution X 2, 3, 6, 8, 11 a, b, d

6. Commercial Fisheries X Salmon, pelagic fish, crabs 2, 8 a, b

7. Recreational Fisheries X Salmon, pelagic fish 2, 8 a, b

8. Breeding/Spawning Areas X 2, 8 a, b

9. Nursery Areas X Juvenile flatfish and crabs. 2, 8 a, b

10. Feeding Areas X

Juvenile/adult salmonids, marine 

mammals, pelagic birds 2, 8 a, b

11. Migration Routes X

Marine mammals, salmonids, 

pelagic and shore birds 2, 8 a, b

12. Critical Habitat of Threatened 

or Endangered Species X No critical habitat present 2, 8 a, b

13. Spatial Distribution of Benthos X 2, 8, 10 a, b

14. Marine Mammals X

Potential impact to resident and 

migratory species 2, 8 a, b

15. Mineral Deposits X 1, 8 a, b, 

16. Navigation Hazard X

Navigation of small boats around 

the dredge 1, 8 a, b, d

17. Other Uses of Ocean

(cables, pipelines, etc) X 8 a, b, d

18. Degraded Areas X 4, 6, 7 a, b, d

19. Water Column 

Chemical/Physical Characteristics X 4, 6, 9 a, b, d

20. Recreational Uses X

Inconvenience to recreational 

boats 2, 8, 11 a, b, d

21. Cultural/Historic Sites X No shipwrecks identified 11 b

22. Physical Oceanography -

Waves/Circulation X 1, 3, 6, 7 a, b, d

23. Direction of Transport/Potential 

for Settlement X 1, 3, 6, 7 a, b, d

24. Monitoring X 5 a, d

25. Shape/Size of Site X 1, 4, 7 d

26. Size of Buffer Zone X 2, 3, 4, 7, 11 b, d

27. Potential for Cumulative Effects X 4, 7 d
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 25

Conflict Matrix Tables Legend

1/ Definition of “Areas of Consideration”

1. Unusual Topography/Unique Bottom Features: Would placement of material in this candidate site affect 

physical bottom feature that is unique within the local or regional area?

2. Physical Sediment Compatibility: Does the candidate site have similar sediment characteristics to anticipated 

dredged material?

3. Chemical Sediment Compatibility: Does the candidate site have similar chemical characteristics to anticipated 

dredged material?

4. Influence of Past Disposal: Would placement of material in this candidate site be affected by previous disposal 

of dredge material?

5. Living Resources of Limited Distribution: Would placement of material in this candidate site affect any living 

resources that do not have a coast-wide distribution?

6. Commercial Fisheries: Would placement of material in this candidate site affect any commercial fishing activity 

(resource impacts are covered in 8-11)?

7. Recreational Fisheries: Would placement of material in this candidate site affect any recreational fishing activity 

(resource impacts are covered in 8-11)?

8. Breeding/Spawning Areas: Would placement of material in this candidate site affect breeding and spawning 

areas of any species?

9. Nursery Areas: Would placement of material in this candidate site affect nursery areas of any species?

10. Feeding Areas: Would placement of material in this candidate site affect feeding areas of any species?

11. Migration Routes: Would placement of material in this candidate site affect migration routes of species?

12. Critical Habitat of Threatened or Endangered Species: Would placement of material in this candidate site affect 

critical habitat of threatened or endangered species?

13. Spatial Distribution of Benthos: Would placement of material in this candidate site change the benthic 

invertebrate community structure (e.g., fine-gain species to coarse-grain species, etc)?

14. Marine Mammals: Would placement of material in this candidate site affect marine mammals or their habitat 

(e.g., gray whale feeding areas etc)?

15. Mineral Deposits: Would any known mineral deposits be affected by the placement of material?

16. Navigation Hazard: Would the placement of material create a navigation hazard?

17. Other Uses of Ocean: Would placement of material impact other uses of the ocean not addressed elsewhere, 

such as cables, pipelines, tow boat lanes, and pilot transfer points?

18. Degraded Areas: Would disposal in this candidate site continue to affect or improve the degraded area?

19. Water Column Chemical/Physical Characteristics: Would placement of material in this candidate site affect 

water column chemical/physical characteristics?

20. Recreational Uses: Would placement of material affect recreational uses?

21. Cultural/Historic Sites: Would placement of material in this candidate site impact or protect a cultural/historic 

site?

22. Physical Oceanography, Waves/Circulation: Would placement of material affect wave/circulation patterns?

23. Direction of Transport/Potential for Settlement: Would placement of material affect direction of sediment 

transport and/or potential for settlement?

24. Monitoring: Would use of this candidate site affect either on-going monitoring or the ability to monitor using 

conventional methods? Monitoring typically would include periodic hydrographic surveys and could include 

sediment sampling or biological data collection.

25. Shape/Size of Candidate Site: Is the candidate site suitable for the operation and maneuverability 

of a dredge?

Is it oriented so the dredge can place material while heading into the waves?

Is the depth of water sufficient to open the hopper doors/dump scow?

Can the dredge operate safely?

Is the size of the candidate site large enough for long-term use?

26. Size of Buffer Zone: Is the candidates site a sufficient distance from important resources or features to protect 

them from any affect of disposal?

27. Potential for Cumulative Effects: Would placement of material contribute to cumulative affects from other 

activities?
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 26

Conflict Matrix Tables Legend (continued)

2/ Definition of Degrees of Conflict

Conflict: There will definitely be an adverse impact on the resource or the use.

Potential Conflict: There is a possibility of an adverse impact; however, extent and significance are unknown.

No Conflict: There will definitely not be an adverse impact on the resource or the use.

Beneficial Use: There will be a positive impact on the resource or the use.

3/ Eleven Specific Factors for Ocean Disposal Site Selection

1. Geographical position, depth of water, bottom topography, and distance from coast.

2. Location in relation to breeding, spawning, nursery, feeding, or passage areas of living resources in adult or 

juvenile phases.

3. Location in relation to beaches or other amenity areas.

4. Types and quantities of waste proposed to be disposed and proposed methods of release, including methods of 

packaging the waste, if any.

5. Feasibility of surveillance and monitoring.

6. Dispersal, horizontal transport, and vertical mixing characteristics of the area, including prevailing current 1 

velocity, if any.

7. Existence and effects of present or previous discharges and dumping in the area (including cumulative effects).

8. Interference with shipping, fishing, recreation, mineral extraction, desalination, shellfish culture, areas of special 

scientific importance and other legitimate uses of the ocean.

9. Existing water quality and ecology of the site, as determined by available data or by trend assessment or baseline 

surveys.

10. Potential for the development or recruitment of nuisance species within the disposal site.

11. Existence at or in close proximity to the site of any significant natural or cultural features of historical 

importance.

4/ Four General Criteria for the Selection of Ocean Disposal Sites

a. The dumping of material into the ocean will be permitted only at sites or in areas selected to minimize the 

interference of disposal activities with other activities in the marine environment, particularly avoiding areas of 

existing fisheries or shell fisheries, and regions of heavy commercial or recreational navigation.

b. Locations and boundaries of disposal sites will be chosen so that temporary perturbations in water quality or 

other environmental conditions during initial mixing caused by disposal operations anywhere within the site can be 

expected to be reduced to normal ambient seawater levels or to undetectable contaminant concentrations or effects 

before reaching any beach, shoreline, marine sanctuary, or known geographically limited fishery or shell fishery.

c. Effective January 1, 2009, this paragraph, 40 CFR 228.5(c) was removed and reserved, see 73 Fed. Reg. 74983 

(December 10, 2008), and is therefore no longer a criterion in the regulations. 

d. The sizes of ocean disposal sites will be limited in order to localize, for identification and control, any single 

immediate adverse impact and to permit the implementation of effective monitoring and surveillance programs to 

prevent adverse, long-range impacts. The size, configuration, and location of any disposal site will be determined as 

a part of the disposal site evaluation or designation study.

e. EPA will, whenever feasible, designate ocean dumping sites beyond the edge of the continental shelf and other 

such sites that have been historically used.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 27

The following were selected for evaluation of resources of limited distribution:

1. Navigation Hazards Area/Other Recreation Areas

2. Shellfish Areas

3. Critical Aquatic Resources

4. Commercial and Sport Fishing Areas

5. Geological Features

6. Cultural, Historically Significant Areas

Figure 4 is a composite of the above areas and shows high usage areas within the vicinity of the 

Siuslaw ocean disposal sites. The denser the pattern overlap, the more interactions between 

various limited resources exist, thus the more critical the overlap area.

Figure 4. Overlay Evaluation of Individual Resources
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 28

As Figure 4 shows, the adjusted sites are within minimal conflict areas in the ZSF. Disposal 

operations occur generally between June 1 and October 31 of each year. While this represents a 

temporal overlap, communications with USACE personnel indicate no observable conflicts 

between the dredging activities and the fishery. Appendix A contains a discussion of all 

potential conflicts within the ZSF with living resources, and concludes that there are no major 

conflicts or predictable future conflicts.

Minimizes Changes in Water Quality (b). The second of the four general criteria requires 

changes to ambient seawater quality levels occurring outside the disposal sites to be within water 

quality criteria, and that no detectable contaminants reach beaches, shoreline, sanctuaries, or 

geographically limited fisheries or shellfisheries. No significant contaminant or suspended solids 

releases are expected with disposal of Siuslaw sandy material (about 97% of dredged material) or 

disposal of finer-grained material (about 3% of dredged material) (see Appendix C). The 

proposed sites should not have any long-term impact on the water quality, with the primary

impact of disposal activities on water quality expected to be the temporary turbidity caused by

the physical movement of sediment through the water column. There should be no water quality

perturbations moving toward a limited resource. Bottom movement of deposited material is 

discussed in Appendix B.

Interim Sites Which Do Not Meet Criteria (c). Effective as of January 1, 2009, this paragraph, 

40 CFR 228.5(c) was removed and reserved. See 73 Fed. Reg. 74983 (December 10, 2008), and 

is therefore no longer a criterion in the regulations. 

Size of Sites (d). The third general criterion requires that the size, configuration, and location of 

the site(s) be evaluated as part of the study, and that the size be limited. 

Since 1977 specific dredged material disposal sites have been used off the mouth of the Siuslaw 

River. More than thirty-years of monitoring at Siuslaw and other Oregon ODMDS have shown 

that original 1977 Interim Site configurations were too limited in size. Potential mounding 

limited long-term site capacity, and since there has been a history of mounding at the smaller 

previously utilized sites, it is clear that new designated sites should be larger to increase capacity 

and enhance dispersal. 

The USACE 1992 Siuslaw Ocean Dredged Material Disposal Site Evaluation report identified 

two ODMDSs north and south of the entrance. These sites have been used under the Corps 

Section 103 site selection authority since 1997. This tripled the area available for dredged 

material placement compared to the relatively small 1977 Interim Site. Based upon annual 

bathymetric monitoring of the Section 103 sites from 1981 to 2009 (See Appendix B figures B-4 

through B-8), EPA proposes to ensure long-term disposal capacity by enlarging the designated 

sites -- doubling the South Site and expanding the North Site into shallower water. Two sites are 

again being proposed, to ensure site managers can be responsive to the specifics of each dredging 

season based on dredge schedules and recorded seasonal sediment transport patterns north and 

south along the Oregon coast. 

The proposed sites are located within the generally homogeneous sandy habitat off the mouth of 

the Siuslaw River, within a reasonable haul distance from dredging areas and generally removed 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 29

from other use conflicts. They encompass previously used and monitored sites, so past 

monitoring data may be used to manage the sites. The proposed sites now incorporate shallow 

and deep water areas. Use of the shallower portion of the North Site will facilitate increased 

sediment transport thereby increasing long-term site capacity. Preferential utilization of the 

shallow portions of the North Site also meets the management goal of keeping material in the 

littoral system. However, as seen in the 1977 Interim Site, mounding could occur if too much 

material is placed too quickly in shallow water. The designation of multiple sites with deeper 

areas within the sites, allows site managers to be responsive to annual and long-term sediment 

transport patterns. 

The proposed sites are oriented for safe and optimal on-site dredge operations. Oriented with 

their long axis toward the west and northwest, the sites allow hopper dredges leaving the Siuslaw 

to head perpendicular to the dominant wave direction while disposing of dredged material.

Finally, in addition to formal site selection criteria and factors, the size, configuration and 

locations of the proposed sites meet other selection and management considerations important to 

EPA, including maximized capacity of the sites (since a Section 102 site designation is not 

limited to a predetermined number of years), minimized potential for mounding and associated 

safety concerns, maximized volume of material remaining in the littoral system, and avoidance 

of effects to unique resources. 

Sites Off the Continental Shelf or Other Historically Used Sites (e). Any potential disposal 

sites off the continental shelf in the area of the Siuslaw River would be at least 40 nautical miles 

offshore. By contrast, the Siuslaw ZSF extends a maximum of only 5.14 nautical miles from 

shore. The Siuslaw navigation project could not be economically maintained using current 

dredging technology and availability if a site off the continental shelf was used. In addition, use 

of a site off the continental shelf would result in as loss of sediments from the nearshore littoral 

transport system, which could cause detrimental bottom or shoreline changes in the ZSF. 

Further, very little is known of the ecology of benthic communities on the continental slope, and 

disposal in this area could cause impacts of unknown severity. Finally, relative monitoring and 

surveillance logistics would be more costly and difficult at a site located off the continental shelf. 

For these reasons, designation of an ODMDS off the continental shelf is not recommended. The 

proposed sites encompass sites that have been historically used, meeting the second directive of 

this criterion.

Application of Eleven Specific Factors (40 CFR 228.6)

Geographical Position, Depth of Water, Bottom Topography, and Distance from the Coast 

(1). The proposed North and South ODMDS are approximately 1 mile offshore from the 

entrance to the Siuslaw River (see Figure 1). Appendix B contains a discussion of the bottom 

topography of the proposed sites. The two designated sites would be used for disposal of 

dredged material from the Siuslaw River navigation project and other permitted projects.

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

ranges from approximately 30-115 feet), and has the following coordinates (NAD 83):
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 30

44o01’ 31.03”N, 124o10’ 12.92”W

44o01’ 49.39”N, 124o10’ 02.85”W

44o01’ 31.97”N, 124o09’ 01.86”W

44o01’ 13.45”N, 124o09’ 11.41”W

The proposed South ODMDS is 3,000 feet by 2,000 feet with an average depth of 100 feet 

(depth ranges from approximately 80-125 feet), and has the following coordinates (NAD 83):

44o00’ 46.72”N, 124o10’ 26.55”W

44o01’ 06.41”N, 124o10’ 24.45”W

44o01’ 04.12”N, 124o09’ 43.52”W

44o00’ 44.45”N, 124o09’ 45.63”W

Based upon consideration of the location, depth of water, bottom topography, and distance from 

the coast, the proposed Siuslaw ocean disposal sites are expected to be suitable for the disposal 

of dredged material when the material is placed in accordance with the SMMP.

Location in Relation to Breeding, Spawning, Nursery, Feeding, or Passage Areas of Living 

Resources in Adult or Juvenile Phases (2). Aquatic resources of the oceanic region off the 

mouth of the Siuslaw River are described in detail in Appendix A. In addition, EPA evaluated 

possible impacts to species and critical habitat listed under the Endangered Species Act in a 

Biological Assessment (EPA 2009). The proposed ocean disposal sites are located in the 

nearshore area and many nearshore pelagic organisms are found in the water column over the 

sites. These include zooplankton (copepods, euphausiids, pteropods, and chaetognaths) and 

meroplankton (fish, crab, and other invertebrate larvae). These organisms generally display

seasonal changes in abundance. Since they are present in the oceanic region off of most of the 

Pacific Coast, those populations directly off the Siuslaw River are small compared to the overall 

coastal populations. Based on evidence from previous zooplankton and larval fish studies, it 

appears that there will be no impacts to organisms in the water column (Sullivan and Hancock 

1977). 

Benthic samples are discussed in detail in Appendix A. Based on the analysis of benthic samples 

collected from the area of the proposed Siuslaw ocean disposal sites, the sites contain benthic 

fauna common to nearshore, sandy, wave-influenced regions that exist along much of the Pacific 

Coast in Oregon and Washington.

Sediment in and near the proposed Siuslaw ocean disposal sites consists of well-sorted, fine 

sands typical of Pacific Northwest coastal areas (Appendix C). The infaunal community of the 

Siuslaw study area is dominated by gammarid amphipods and polychaete worms. The benthos 

in the area is typical of the communities found near other ocean disposal sites along the Oregon 

Coast, such as Coos Bay areas E and F, the Siuslaw River, and the 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 fish. They also play an active role 

in the breakdown of organic debris and the tube-building species help stabilize the marine 

sediments. Many of the benthic species in the area are able to survive in this dynamic 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 31

environment since they are either very mobile or are able to react both to natural or human 

perturbations. They can readily recolonize disturbed areas.

The Siuslaw nearshore area supports a variety of pelagic and demersal fish species and shellfish. 

Many of these species have a reproductive strategy that includes releasing a large quantity of 

eggs so that some individuals will survive the substantial mortality common to the species during 

the larval and juvenile stages. Crabs in particular release large number of eggs into the water 

column. The larvae that hatch are planktonic for several months before settling to the bottom of 

the estuary and in the nearshore area as young crab. During this time, they are subjected to a 

variety of environmental factors that affect their survival and have a direct affect on adult 

population numbers. 

Numerical modeling of the disposal process by Pearson and others (2006) at the mouth of the

Columbia River showed that predicted impact pressure, shear stress, and mound depth were 

greatly reduced by discharge in deep water (e.g., ocean disposal in 230 and 280 feet of water). 

The study found that vulnerability of crabs to compression (vertical) forces was low and that 

crabs may be vulnerable to injury from surge currents. However, the surge currents from 

modeling the deep-water scenarios were not strong enough to mobilize sediment greater than 1 

millimeter or juvenile Dungeness crabs. Results also suggested that Dungeness crabs were 

vulnerable to injury from burial through effects on crab respiration and survival (Pearson et al., 

2006). Previous studies showed that under burial with 10 centimeters (about 4 inches) of 

material, crabs were unable to recover the respiratory pathway and switched to moving up 

through the sediment, a process that occurred over 24 hours.

Vavrinec and others (2007) performed laboratory experiments to isolate the effects on 

Dungeness crabs from burial by dredged material, and crab response and injury caused by 

tumbling in horizontal surge currents. The horizontal surge current experiments showed no 

damage, 100 percent survival, and the behavioral capability of crabs to recover their proper 

orientation after tumbling. The crabs either maintained their proper orientation on the bottom 

and in the water column, or righted themselves within 2 seconds after being moved by a 3.2 

meter/second (about 10.5 feet/second) surge current.

The crab burial experiments (Vavrinec et al., 2007) showed that survival from burial increased as 

burial depth decreased, and survival increased as crab size increased. Also, male crabs had a 

higher survival rate than female crabs. When restrained and not allowed an escape response, all 

the adult crabs suffocated and died within 24 hours when buried in 8 centimeters of dredged 

material. The observations clearly show that maintaining the respiratory pathway is the key to 

surviving burial. For unrestrained crabs tested in large tanks with sufficient space for escape 

response, survival increased substantially. Escape response and other adaptive behavior clearly 

enabled the subadult and adult crabs to achieve almost 100 percent survival under the same 

burial depth that allowed no survival at all for restrained crabs. For unrestrained age 2+ crabs, 

predicted survival begins to decrease at burial depths greater than 10 centimeters, and is less than 

10 percent at burial depths greater than 16 centimeters. Behavioral observations and survival 

results showed that subadult and adult crabs have the capability to respond to surge currents and 

burial in ways that substantially reduce exposure to stress and allow high survival.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 32

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

salmon, summer and winter steelhead, and spring and fall Chinook salmon, as well as a variety 

of other pelagic and demersal fish species. Seals and sea lions inhabit the lower Siuslaw River 

and coastal area. The Siuslaw nearshore area and shoreline provides important habitat for 

shorebirds, waterfowl, herons, and many other species of birds. Pelagic birds (e.g., murres, 

auklets, cormorants) likely use the area for foraging. Federally listed species that may be present 

in the Siuslaw offshore area were previously discussed in the Affected Environment, Biological 

Resources section of this report.

In general, the locations of the proposed ocean disposal sites do not provide unique breeding, 

spawning, nursery, feeding, or passage habitat. It is unlikely that any of the larger organisms 

(fish, marine mammals, etc.) would experience physiological effects as a consequence of 

disposal because the resulting turbidity plume and physical disturbance to the water column 

would likely cause them to avoid the area. Based on modeling completed by the USACE, water 

column turbidity would be expected to dissipate within a few minutes to half hour. Any

avoidance behavior would be limited to the duration of this physical disturbance. Indirect 

impacts could occur if disposal operations changed the value of the habitat by burying the 

existing benthic community 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). Lastly, evaluation of past disposal activities has not 

indicated that any long-term adverse impacts to living resources have occurred.

Location in Relation to Beaches and other Amenity Areas (3). The proposed ocean disposal 

sites are at least 2,000 feet from the end of the jetties and 3,000 feet from the nearest beach. 

There are no rocks or pinnacles in the vicinity of either site. The Siuslaw River marks the 

northern boundary of the Oregon Dunes National Recreation Area. This portion of the recreation 

area contains no developed facilities other than a paved road that parallels the shoreline and 

provides access to the beach and South Jetty area. Two public recreation areas are located to the 

north of the Siuslaw River. Heceta Beach Park is operated by Lane County with beach access, 

picnic tables, and restrooms. Harbor Vista Park is also operated by the county and offers 15 acres 

of tent and recreation vehicle camping on a year-round basis. It is one of the few campgrounds 

on the Oregon Coast with an ocean view and has restrooms, showers, a playground and hiking 

trails. Beachcombing, sightseeing and clamming are popular activities along the entire coastline. 

The area within the Oregon Dunes National Recreation Area receives a greater amount of use 

because of availability of public access. The proposed designation of the Siuslaw North and 

South ocean disposal sites is not expected to have any impact on the recreational uses of the 

adjacent uplands areas within these recreation areas. 

Types and Quantity of Wastes Proposed to be Disposed of, and Proposed Methods of 

Release, including Methods of Packing the Waste, if any (4). Dredged material subject to the 

MPRSA is not a waste. The sites that are designated will receive dredged materials transported 

by either government or private contractor hopper dredges or dump barges. Current hopper 

dredges or dump barges available for use have capacities ranging from 800 to 6,000 cy. This 

would be the likely volume range of dredged material deposited in any one dredging placement 

cycle. The estimated volume to be removed annually from the Siuslaw River federal navigation 

project will range, but can be placed at the sites in one dredging season by any combination of 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 33

private and government dredges. For example, volumes from 1997 to 2009 ranged from 22,300 

cy to 117,300 cy, giving a 13-year average annual volume of about 60,000 cy. The dredges or 

barges would be under power and moving during disposal.

The bulk of the dredged material to be disposed in the ocean comes from shoals in and near the 

Siuslaw River entrance channel. These shoals consist primarily of marine sand transported into 

the entrance as part of the Heceta Head littoral cell. The material meets marine sediment 

screening level guidelines for chemicals of concern per the Sediment Evaluation Framework 

(SEF 2009), is far removed from known sources of contaminants, and has been characterized 

under the SEF as suitable for unconfined open-water disposal. 

The federally maintained entrance channel into the Siuslaw River is authorized at 18 feet deep 

and 300 feet wide, and runs from deep water to river mile (RM) 0.2. From there upstream to the 

dock at Florence (RM 5.0), the channel is maintained to 16 feet deep and 200 feet wide. A 

turning basin, currently maintained by the Corps at 16 feet deep, 400 feet wide and 600 feet long, 

is located opposite the dock at Florence. The channel from RM 5.0 upstream to RM 16.5 is an 

authorized (though not currently maintained) federal channel, 12 feet deep and 150 feet wide. At 

RM 15.8 the channel widens into a turning basin 12 feet deep, 300 feet wide and 500 feet long, 

also part of the federally authorized, but not currently maintained channel. 

The channel above RM 5.0 has required very infrequent maintenance. A pipeline dredge last 

cleared the shoals at RM 5.5 and 6.0 in 1982. No dredging has been performed above that point 

since 1976. Siuslaw River sediments (to RM 16.1) were last sampled in 2006. These physical 

and chemical analyses indicate that the material is primarily sand, meets marine sediment 

screening level guidelines for chemicals of concern per the Sediment Evaluation Framework 

(SEF 2009), is far removed from known sources of contaminants, and would be characterized 

under the SEF as suitable for unconfined open-water disposal

Feasibility of Surveillance and Monitoring (5). Monitoring and surveillance are both feasible 

within the ZSF and are included as requirements in the SMMP for these proposed sites (see 

Appendix F). At a minimum, annual bathymetric surveys will be conducted in areas that receive 

dredged material. More frequent surveys will be conducted when necessary to ensure 

unacceptable mounding is not occurring that could pose a threat to navigation safety. If actual

field monitoring of the disposal activities is required because of a future concern for habitat 

changes or limited resources, several research groups are available in the area to perform any 

required work. The proposed Siuslaw ocean disposal sites are readily accessible. Most 

surveillance and monitoring work can be performed from small, surface research vessels at a 

reasonable cost, or from the disposal vessel.

Dispersal, Horizontal Transport and Vertical Mixing Characteristics of the Area Including 

Prevailing Current Direction and Velocity, if Any (6). The sediments dredged from the 

Siuslaw River entrance are predominantly marine sands and fluvial gravels. Although the 

Siuslaw River delivers a large sediment load, the bottom contours suggest a rapid distribution 

away from the river mouth. The beaches seem to be in equilibrium, suggesting that littoral 

transport is in balance. From bottom current records, there appears to be a net annual transport 

of sediment to the north. There is some southward sediment transport during summer. During 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 34

summer, the current velocities are variable (see Appendix B). This is due to the constantly

varying river outflow combined with tidal flows to produce a highly variable influence on the 

nearshore circulation.

Sediment movement in the littoral zone consists of two mechanisms depending upon the size of 

the sediment. Anything finer than sand-size is carried in suspension in the water and is removed 

offshore relatively quickly. The almost total lack of silts and clays within the Siuslaw ZSF 

attests to the efficiency of this mechanism. Sediments sand-size or coarser may be occasionally

suspended by wave action near the bottom, and are moved by bottom currents or directly as 

bedload. Tidal, wind and wave forces contribute to generating bottom currents, which act in 

relation to the sediment grain size and water depth to produce sediment transport.

Existence and Effects of Current and Previous Discharges and Dumping in the Area 

including Cumulative Effects (7). No cumulative effects have been documented in the area 

aside from mounding, i.e. lack of material dispersal, within the sites as currently configured. The 

Siuslaw North and South ODMDS are being proposed because of mounding problems associated 

with disposal at the previous 1977 Interim and Section 103-selected ocean disposal sites. The 

proposed North and South sites are located and sized to allow management of the sites – a 

flexible disposal strategy implemented within larger sites to minimize mounding. Per the SMMP, 

annual bathymetric monitoring will be used to track changes in site bathymetry and will be used 

to evaluate potential mounding. The preference for disposal of material in the shallow portions 

of the proposed North Site will provide the positive cumulative effect of returning natural 

material to the Heceta Head littoral cell. 

Interference with Shipping, Fishing, Recreation, Mining Extraction, Desalination, Fish and 

Shellfish Culture, Areas of Special Scientific Importance, and Other Legitimate Uses of the 

Ocean (8).

Shipping. No conflicts with commercial navigation traffic have been recorded in the 

long history of hopper dredging activity. The likely reason for this is the light commercial traffic 

in the Siuslaw River channel.

Commercial and Recreational Fishing. Commercial and recreational fisheries occur in 

and around the proposed Siuslaw ocean disposal sites (see Appendix A). The Siuslaw ZSF area 

supports a moderate commercial fishery primarily for salmon, groundfish, and Dungeness crabs. 

The commercial fishing season generally begins in June and runs through October, subject to 

established catch quotas. During this period, the potential exists for conflicts between a dredge 

and fishing boats. Based on data from the National Marine Fisheries Service (NMFS 2006) for 

commercial fishing, a total of 38 vessels, all commercially registered, delivered landings to 

Florence in 2000, in the following West Coast fisheries: crab, groundfish, highly migratory 

species, salmon, shrimp, and other species. Dungeness crab had the highest landing value at 

$562,057, while groundfish landings were the largest by weight at 124.3 metric tons. A total of 

41 commercial vessels were owned by Florence residents in 2000, 19 of which participated in the 

federally-managed groundfish fishery. 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 35

A locally important recreational salmon fishery exists offshore of the Siuslaw River. Based on 

data from NMFS (2006), there is at least one sport fishing charter business in Florence. There 

were seven sport fishing licensing agents in Florence in 2000, when 4,907 sport fishing licenses 

were sold at a value of $80,163. Even though the offshore salmon fishing can be productive, a 

rough bar periodically limits this opportunity for most small pleasure craft. Salmon fishing is 

most popular from May through September when ocean conditions are more predictable and 

salmon are feeding in the nearshore area prior to the fall spawning runs. The year 2000 

recreational salmonid catch in the ocean boat fishery was 250 Chinook salmon and 472 coho 

salmon.

The Siuslaw jetty fishery is also popular and accounts for a relatively high number of angler use 

days. The jetties are among the best in the state for catching surf perch. A smooth bottom 

offshore of the Siuslaw River has limited the establishment of substantial bottom fish 

populations, however the year 2000 non-salmonid catch was a total of 213 fish including 

greenstripe, canary, and yelloweye rockfish, and Pacific halibut. 

Mineral Extraction. There are no known metallic mineral deposits within the Siuslaw 

ZSF. No exploratory oil/gas wells have been drilled offshore near the mouth of the Siuslaw 

River and no development is expected in the future.

Desalination. There are no desalination plants in the area of the Siuslaw River.

Wave Energy. With the increased interest in alternative energy sources, various wave 

energy projects have been proposed off the Oregon Coast. The Oregon State Governor, in a 

November 2007 news release to the Oregon Fishing Industry, stated that he was asking the 

Federal Energy Regulation Commission to limit the permitting of wave energy to five to seven 

locations. Wave energy projects at those locations will involve numerous generating buoys 

moored offshore with transmission lines running to shore distribution facilities. Currently, no 

wave energy projects are proposed off the Siuslaw River.

Fish and Shellfish Culture. There are no fish or shellfish culture operations in the area 

of the proposed Siuslaw ocean disposal sites.

Marine Reserves. The State of Oregon has initiated efforts to establish a network of 

state marine reserves as part of an overall strategy to manage its marine waters and submerged 

lands. The overall purpose would be to protect, sustain, or restore the nearshore marine 

ecosystem, its habitats, and species. A state marine reserve, as defined by Oregon, is an area 

within Oregon’s state territorial sea or adjacent intertidal area that is protected from all extractive 

activities including the removal or disturbance of living and non-living marine resources. 

Marine reserves are intended to provide lasting protection. Dredging and disposal are identified 

as disturbances and would be banned from areas designated as marine reserves. In 2009, Oregon 

authorized two marine reserves, one at Otter Rock off Depoe Bay and one at Redfish Rocks off 

Port Orford. State agencies are to evaluate potential reserves at Cape Falcon south of Cannon 

Beach, Cascade Head near Lincoln City, and Cape Perpetua near Yachats. State agencies also 

have been directed to support a reserve proposal for the Cape Arago-Seven Devils area, south of 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 36

Coos Bay. None of the sites currently identified are in or near the proposed Siuslaw OSMDS, 

and all coastal ocean disposal site designations will have to avoid marine reserve areas.

Special Scientific Importance. There are no known transects or other scientific study

locations that would be impacted by disposal at the proposed Siuslaw ocean disposal sites.

General Discussion of Other Legitimate Uses. There has not been a demonstrated 

conflict with any of the above listed uses at the historically used ocean disposal sites and no use 

conflicts are expected at the two proposed sites. There is a low potential for future conflicts 

given that the area of the proposed sites has no unique value, is relatively small, and presents few 

potential conflicts with other uses in the vicinity. Since dredged material disposal sites in the 

vicinity have been in use for over 30 years, EPA’s designation of the two proposed Siuslaw 

ocean disposal sites would not be expected to result in any change to the existing uses of the 

area, by any individuals or groups, or any associated economic benefit of those uses.

It should also be noted that EPA is proposing to designate these ODMDS primarily in 

support of the Corps’ operation and maintenance dredging in the Siuslaw River navigation 

channel. The need for that maintenance dredging was recently underscored by U.S. Coast Guard 

in a letter dated March 15, 2010, which characterized the Siuslaw as the most restricted entrance 

bar on the coast of Oregon. The dredging of the entrance bar at Siuslaw is required annually in 

order to facilitate many of the other uses of the area.

The Existing Water Quality and Ecology of the Site as Determined by Available Data or by 

Trend Assessment or Baseline Survey (9). Water and sediment quality analyses conducted in 

the study area and experience with past disposals in this region have not identified any adverse 

water quality impacts from ocean disposal of dredged material (see Appendix C). The ecology

of the offshore area, based mainly on fisheries and benthic data, is that of a mobile sand 

community. Neither the pelagic or benthic communities should sustain any long-term impacts 

due to their mobility and widespread occurrence off the Oregon Coast (see Appendix A).

Potentiality for the Development or Recruitment of Nuisance Species in the Disposal Site 

(10). Nuisance species are any undesirable organism(s) not previously found at a disposal site. 

They are transported to, or recruited to, a site because the disposal of dredged materials creates 

an environment where they can establish. Materials to be dredged and transported to the 

proposed Siuslaw ocean disposal sites historically have been classified as uncontaminated 

marine sands similar to the sediment present at the sites. Potential material dredged from the 

upstream boat basin access channels may include fine-grained material, however only limited 

quantities of fine-grained material from the boat basin access channels have been placed in the 

ocean. Any material proposed for ocean disposal would be subject to sediment quality

evaluation. Therefore, it is highly unlikely that nuisance species could be established at the 

disposal site since habitat or contaminant levels are unlikely to change over the long-term.

Existence at or in Close Proximity to the Site of any Significant Natural or Cultural 

Features of Historical Importance (11). The cultural resources of the Siuslaw River study area 

is described in detail in Appendix D. The cultural resource that has the greatest potential for 

impact by use of the proposed ocean disposal sites is shipwrecks. Potential shipwreck areas are 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 37

evaluated in Appendix D. Historical records show that there are not any shipwrecks within the 

area of the proposed Siuslaw ocean disposal sites.

SUMMARY OF COORDINATION UNDER OTHER APPLICABLE 

FEDERAL STATUTES

Federal Action

The proposed federal action consists of designation of two ocean disposal sites at the mouth of 

the Siuslaw River. 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 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 the statutory

and regulatory criteria for ocean disposal of dredged material. Therefore, actual disposal is an 

indirect effect of site designation and is included in the evaluation of effects under the below 

listed statutes.

Public Comments

EPA received three comments on the proposed rule. All three comments supported the Site 

designations. One commenter asked whether the Sites could be extended to run parallel to the 

coastline in order to create a “speedbump” resulting in decreased wave energy and erosion on the 

beach. The final Sites include shallow areas (less than 50 ft), where more material is expected to 

remain the littoral system, thereby potentially decreasing potential beach erosion. The creation 

of a nearshore “speedbump” or berm would dissipate wave energy reaching the beach, but would 

increase the wave height at the berm, potentially creating an unacceptable safety risk. The same 

commenter asked whether the sandy dredged material could be used to restore an eroded beach 

rather than be disposed in the Sites. The sandy dredged material in the vicinity of these Sites is 

already found in abundance onshore in the nearby Oregon Dunes Recreation Area and onshore 

dune fields. No eroded beaches in the immediate vicinity of the Sites for which this material is 

needed have been identified at this time. Other general questions included in this comment letter 

regarding timing of dredging and disposal, sediment quality, alternatives, etc. are addressed 

elsewhere in this document.

Endangered Species Act

In the Biological Assessment prepared for the proposed action (EPA 2009) and subsequent 

supporting documents, EPA concluded that the indirect effects of designation of the Siuslaw 

ocean disposal sites:
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 38

1. May affect, but is not likely to adversely affect OC coho salmon, SONCC coho salmon, and 

Lower Columbia River coho salmon; no effect to critical habitat for OC and SONCC coho 

salmon.

2. May affect, but is not likely to adversely affect any Chinook ESU; no effect to critical 

habitat.

3. May affect, but is not likely to adversely affect Southern DPS green sturgeon or designated 

critical habitat.

4. Is not likely to jeopardize the continued existence of Southern DPS Pacific eulachon.

5. May affect, but is not likely to adversely affect Steller sea lion, blue whale, fin whale, 

humpback whale, southern resident killer whale; no effect to critical habitat.

6. May affect, but is not likely to adversely affect marbled murrelet, short-tailed albatross, and 

brown pelican; no effect to critical habitat.

7. 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; 

no effect to critical habitat.

The EPA initiated consultation under Section 7 of the Endangered Species Act of 1973, as 

amended, 16 U.S.C. Sections 1531 to 1544, based on this documentation with both the U.S. Fish 

and Wildlife Service and National Marine Fisheries Service (NMFS) by letter dated July 22, 

2009. USFWS concurred with EPA’s “may affect, not likely to adversely affect determination 

for marbled murrelet, short-tailed albatross, and brown pelican via letter dated August 24, 2009. 

NMFS issued a Biological Opinion (BO) on April 21, 2010. NMFS concluded that 

EPA’s action is not likely to jeopardize the continued existence of Oregon Coast (OC) coho 

salmon or southern green sturgeon (Acipenser medirostris), or to destroy or adversely modify

critical habitat designated for green sturgeon. NMFS also concluded that EPA’s action would 

not likely adversely affect southern green sturgeon, euchalon, eastern Stellar sea lions, blue 

whales, fin whales, humpback whales, Southern Resident Killer whales, marine turtle species, or 

critical habitat designated for southern green sturgeon or proposed for green leatherback turtles. 

NMFS concluded that dredging activities were not interrelated to EPA’s action. However, 

NMFS did make a finding that disposal of dredged material at the Sites by the Corps, the 

anticipated primary user of the Sites, was interrelated to EPA’s action. 

NMFS then focused its effects analysis on the effects of disposal at the Sites. Looking 

solely to the effects of disposal of dredged material at the Sites by the Corps from the Corps’ 

Siuslaw River Navigation project, NMFS estimated 19 juvenile OC coho salmon per year were 

likely to be injured or killed by Corps activities. NMFS acknowledged that EPA’s action does 

not authorize or compel site use and will not itself result in disposal of dredged material. NMFS 

found that all incidental take will occur at the project-specific level. Based on this finding, 

NMFS did not find a basis to provide a take authorization in the current BO. NMFS stated that 

all take authorization will occur in subsequent site-specific consultations. 

Finally NMFS included two discretionary conservation recommendations in the BO. The 

first recommendation suggested collaborating with NMFS and the Corps on a methodology to 

evaluate the effects of dredging and disposal on ESA-listed species. The second 

recommendation suggested undertaking a study to determine seasonal distribution, abundance, 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 39

and habitat use of salmon, sturgeon, and marine turtles in the nearshore within and near the 

contour of designated ocean dredged material disposal sites. Such recommendations are purely 

advisory in nature. EPA appreciates that collaboration on a methodology could be helpful and 

supports NMFS and Corps efforts in such an endeavor. EPA also appreciates that the study

recommended by NMFS could contribute to the scientific knowledge base but believes that 

NMFS, the expert Federal agency on seasonal distribution, abundance and habitat use would be 

better suited than EPA to carry out such a study.

Magnuson-Stevens Fishery Conservation and Management Act

In the Essential Fish Habitat (EFH) assessment prepared for the proposed action (EPA 2009), it 

was concluded that the designation of the proposed Siuslaw ocean disposal sites may adversely 

affect 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. However, any 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 these species. Additionally, the following measures were considered by EPA as a 

way to mitigate any adverse impacts to designated EFH. The EPA expects to incorporate these 

measures into the SMMP for the proposed Siuslaw ocean disposal 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.

The EPA initiated consultation under the Magnuson-Stevens Fishery Conservation and 

Management Act, 16 U.S.C. Section 1855(b), based on this documentation with NMFS by letter 

dated July 22, 2009. 

NMFS response, dated April 16, 2010, concluded that the proposed action and the effect of 

disposal at the Sites would have adverse effects on designated EFH in the form of increased 

turbidity and decreases in prey resources. NMFS provided two “conservation recommendations” 

seeking to implement the effects methodology and habitat usage studies included in the ESA 

section of the BO. EPA is responding to these recommendations separately, by letter as required 

under the Magnuson-Stevens Fishery Conservation and Management Act. 

Marine Mammal Protection Act

The EPA determined that the proposed action to designate the proposed Siuslaw ocean disposal 

sites would not result in take or incidental take of any protected marine mammal under the 

Marine Mammal Protection Act of 1972, as amended, 16 U.S.C. Sections 1361 to 1389. The 

Biological Assessment, which evaluated the possible effects on ESA listed marine mammals, 

including Steller sea lions and whales, was provided the NMFS Office of Protected Resources 
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 40

for review on July 22, 2009. In their April 16, 2010 BO, NMFS found that all effects of the 

action are expected to be discountable or insignificant for ESA-listed marine mammals.

Coastal Zone Management Act

EPA submitted a consistency determination pursuant to the Coastal Zone Management Act, 16 

U.S.C. Sections 1451 to 1465, to Oregon’s Department of Land Conservation and Development 

(DLCD) by letter dated January 19, 2010. Via letter dated April 14, 2010, DLCD concurred with 

the EPA that the proposed project is consistent to the maximum extent practicable with the 

enforceable policies of the Oregon Coastal Management Program.

National Historic Preservation Act

National Historic Preservation Act, as amended, 16 U.S.C. Sections 470 to 470a-2, which 

requires Federal agencies to take into account the effect of their actions on districts, sites, 

buildings, structures, or objects, included in, or eligible for inclusion in the National Register. 

The EPA determined that no historic properties would be affected by the proposed undertaking, 

the designation of the proposed Siuslaw ocean disposal sites. The EPA provided that 

determination and supporting evaluation to the State Historic Preservation Officer in the Oregon 

Parks and Recreation Department by letter dated November 24, 2009. The Tribal Governments, 

listed in the next section, were copied on the historic property letter as consulting parties. By

letter dated December 10, 2009, the State Archaeologist concurred that the project would have 

no affect on any known cultural resources.

Tribal Consultation

Government-to-government consultation letters, dated November 24, 2009, were sent to the 

Coquille Indian Tribe, the Cow Creek Band of Umpqua Tribe of Indians, the Confederated 

Tribes of the Grand Ronde Community, the Confederated Tribes of the Siletz Indians, and the 

Confederated Tribes of the Coos, Lower Umpqua and Siuslaw Indians. Tribal comments were 

also solicited during the NHPA process. Follow-up phone calls were made to staff at each of the 

listed Tribes during January 2010. No Tribal comments were received.

SELECTION OF OCEAN DISPOSAL SITES FOR FORMAL 

DESIGNATION

Based on the evaluation of criteria contained in 40 CFR Part 228, the Corps and EPA have 

determined that the Siuslaw River North and South ocean disposal sites are suitable for 

designation. The designation of the ODMD Sites by EPA will be finalized through formal 

rulemaking adopting this Environmental Assessment/MPRSA Criteria Evaluation and the 

appendices to support this action.
Siuslaw River ODMDS Environmental Assessment and MPRSA Criteria Evaluation page 41

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