Permit 2. BA_USCG Station Siuslaw.pdf

U.S. Coast Guard Station Siuslaw River: Construct Covered Mooring and Correct Shoreline Erosion Project

Draft Biological Assessment

September 2023

Prepared for the U.S Coast Guard by:

Tetra Tech, Inc.

1750 S Harbor Way, Suite 400 Portland, OR 97201

P 503.221.8636 F 503.227.1287 tetratech.com

Project # 100-WTR-T42147

Updated September 2023 by:

Campbell Environmental, LLC

28948 SW Meadows Loop P 503.680.8390 Wilsonville, OR 97070 campbellenviro.com

U.S. Coast Guard Station Siuslaw River i

EXECUTIVE SUMMARY

The United States Coast Guard (USCG) is proposing to replace a boathouse, pier access bridge, and debris screen, and correct shoreline erosion at the United States Coast Guard (USCG) Station Siuslaw

River (Station) in Florence, Oregon. To correct shoreline erosion, the USCG is proposing a durable, long-term solution through the installation of an interlocking steel pile wall along the length of the

Station property waterfront. The replacement covered mooring, or boathouse, will be constructed in the same location as the existing covered mooring but with a larger footprint, and a structure engineered to withstand the elements and future riverbed scour (deepening). The proposed action will include in-water and overwater work, including vibratory and percussion pile driving, with the potential for unavoidable adverse effects to ESA-listed fish species. Upland improvements will include installation of the pile wall near the top of the bank slope, installation of surface swales with gravel trench drains to capture and divert surface water, and grading of the upland bank.

In addition to construction activities associated with the shoreline correction and boathouse replacement, the proposed action includes temporary use of mooring and parking facilities found at the downtown waterfront of Florence. This component of the proposed action is not expected to affect listed species and is not addressed in detail in this document.

Conservation measures and recommendations included in the National Marine Fisheries Service

(NMFS) 2014 Siuslaw River Biological Opinion and additional consultation documents specific to the

USCG project would be implemented during construction to avoid or minimize potential adverse effects to listed species. Conservation measures include, but are not limited to, preparation and implementation of a project-specific Temporary Erosion and Sediment Control Plan, and a Spill

Prevention Control and Countermeasures Plan. Specific pile removal and pile driving conservation measures as well as environmental awareness training would be required of the selected contractor.

Potential adverse effects to ESA-listed species from the proposed action include 1) hydroacoustic disturbance as a result of pile driving, 2) increased turbidity and potential for contamination and reduced water quality, and 3) temporary displacement of migrating coho salmon during construction activity.

This Biological Assessment (BA) evaluates the proposed action for its potential effects on species listed as threatened or endangered under the Federal Endangered Species Act (ESA) and designated critical habitat under the jurisdiction of NMFS and the U.S. Fish and Wildlife Service (USFWS). The effects determinations for ESA-listed species and critical habitats are summarized in Table ES-1 and ES-2.

This BA also evaluates potential effects on Essential Fish Habitat (EFH), as defined by the Magnuson-

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

Sustainable Fisheries Act of 1996. The Magnuson-Stevens Act determinations are provided in Table

ES-3.

U.S. Coast Guard Station Siuslaw River ii

Table ES-1. Summary of Effect Determinations for NMFS-Managed Species.

Table ES-2. Summary of Effect Determinations for USFWS-Managed Species.

Table ES-3. Magnuson-Stevens Act EFH Effects Determination

Essential Fish Habitat Designation Effects Determination

Pacific Coast Salmon Will Adversely Affect

Pacific Coast Groundfish Will Adversely Affect

Coastal Pelagic Species Will Adversely Affect

Common Name (Scientific Name)

ESU/DPS

Status a :Listing b Effect Determination

Critical Habitat Effect Determination

Coho salmon (O. kisutch)

Oregon Coast T:70 FR 37160 LAA LAA

Eulachon (Thaleichthys pacificus)

Southern DPS T:75 FR 13012 NLAA NLAA

Green sturgeon (Acipenser medirostris)

Southern DPS T:71 FR 17757 NLAA NLAA

Humpback Whale (Megaptera novaeangliae)

Central America DPS E:81 FR 62259 NE NE

Mexico DPS T:81 FR 62259 NE NE

Killer Whale (Orcinus orca)

Southern Resident DPS E:70 FR 69903 NLAA NE

a. E: Endangered, T: Threatened

b. Federal Register Citation

LAA = Likely to Adversely Affect NLAA = Not Likely to Adversely Affect NE = No Effect

Common Name (Scientific Name) Status a :Listing b Effect Determination Critical Habitat Effect

Determination

MAMMALS

Pacific marten, Coastal DPS (Martes caurina caurina) T: 85 FR 63806 NE NE*

BIRDS

Marbled murrelet (Brachyramphus marmoratus) T:57 FR 45328 NE NE

Northern spotted owl (Strix occidentalis caurina) T:81 FR 71760 NE NE

Western snowy plover (Charadrius alexandrines nivosus) T:58 FR 12864 NE NE

REPTILES

Leatherback sea turtle (Dermochelys coriacea) E:35 FR 8491 NE NE

Loggerhead sea turtle (Caretta caretta) E:76 FR 58867 NE N/A

Olive ridley sea turtle (Lepidochelys olivacea) T, E:43 FR 32800 NE N/A

a. E: Endangered, T: Threatened

b. Federal Register Citation

NLAA = Not Likely to Adversely Affect LAA = Likely to Adversely Affect NE = No Effect *Provisional effect determination; will not destroy or adversely modify proposed critical habitat

U.S. Coast Guard Station Siuslaw River iii

CONTENTS

EXECUTIVE SUMMARY ........................................................................................................................ I

1.0 INTRODUCTION

1.1 Purpose of The Biological Assessment

1.2 Background

1.3 Purpose and Need For the Proposed Action

1.4 Federal Nexus and Consultation History

2.0 PROJECT DESCRIPTION

2.1 Project Location

2.2 Project Footprint

2.3 Project Elements

2.3.1 Onshore Stormwater Infrastructure Improvements and Sitework

2.3.2 Shoreline Stabilization

2.3.3 Offshore Infrastructure Demolition and Replacement

2.3.4 Temporary Use of Municipal Facilities

2.4 Construction Equipment and Methods

2.5 MLB Operations and Maintenance

2.6 CONSTRUCTION SCHEDULE

3.0 CONSERVATION MEASURES

3.1.1 Water Quality

3.1.2 Noise and Vibration

3.1.3 Hazardous Materials

3.1.4 Habitat Disturbance or Alteration

3.1.5 Collision

4.0 ACTION AREA

4.1 Project Footprint

4.2 Noise

4.2.1 In-air Noise

4.2.2 Underwater Noise

4.3 Turbidity and Sediment Quality

5.0 LISTED SPECIES AND CRITICAL HABITAT IN THE ACTION AREA

5.1 Species and Critical Habitat Addressed in BA

5.1.1 USFWS-Managed Species

5.1.2 NMFS-Managed Species

5.2 Western Snowy Plover

5.2.1 Status and Life History

5.2.2 Use of the Action Area

U.S. Coast Guard Station Siuslaw River iv

5.2.3 Critical Habitat

5.3 Coho Salmon

5.3.1 Status and Life History

5.3.2 Use of the Action Area

5.3.3 Critical Habitat

5.4 Eulachon

5.4.1 Status and Life History

5.4.2 Use of the Action Area

5.4.3 Critical Habitat

5.5 Green Sturgeon

5.5.1 Status and Life History

5.5.2 Use of the Action Area

5.5.3 Critical Habitat

5.6 Marine Mammals

5.6.1 Humpback Whale

5.6.2 Killer Whale

6.0 ENVIRONMENTAL BASELINE CONDITIONS

6.1 Biological Conditions

6.1.1 Estuarine Habitat and Fish Use

6.1.2 Riparian Zones

6.1.3 Wetlands and Submerged Aquatic Vegetation

6.1.4 Developed Upland Habitat

6.2 Hydrology and Water Quality

6.2.1 Hydrology

6.2.2 Water Quality

6.3 Physical Conditions

6.3.1 Substrate and River Bathymetry

6.3.2 Fish Passage

6.4 Critical Habitat

7.0 ANALYSIS OF POTENTIAL EFFECTS TO SPECIES AND CRITICAL HABITAT

7.1 Potential Effects to Species

7.1.1 Noise Disturbance Impacts

7.1.2 Upland Ground Disturbance

7.1.3 Aquatic Habitat Disturbance

7.1.4 Aquatic Habitat Alteration

7.2 Potential Effects to Designated Critical Habitat

8.0 DETERMINATION OF IMPACTS FOR LISTED SPECIES

8.1 Effect Determination for Listed Species

U.S. Coast Guard Station Siuslaw River v

8.1.1 Pacific Coast DPS Western Snowy Plover

8.1.2 Oregon Coast ESU Coho Salmon

8.1.3 Eulachon

8.1.4 Green Sturgeon

8.1.5 Killer Whale

8.2 Effect Determination for Critical Habitat

8.3 Conclusions

9.0 REFERENCES

LIST OF FIGURES

Figure 2-1. Project Location Map

Figure 2-2. Typical section for the preliminary design of a bulkhead wall, with the top of the wall above the 50-year extreme tide level

Figure 4-1. Project Action Area

LIST OF TABLES

Table 2-1. Project Location Details

Table 5-1. ESA-listed Species under Jurisdiction of USFWS, Lane County, Oregon

Table 5-2. NMFS ESA-listed Fish Species With Potential to Occur in the Action Area

Table 5-3. Migration Timing and Spawning Grounds of ESA-listed Fish in the Action Area

Table 5-4. Physical or Biological Features (PBFs) Essential to Conservation of OC Coho Salmon

Table 6-1. Environmental Baseline Summary of OC Coho Salmon PBFs

Table 7-1. Underwater Acoustic Modeling Scenarios

Table 7-2. Acoustic Threshold Levels for Fish and Sea Turtles – Injury and Behavior

Table 7-3. Acoustic Threshold Levels for Fish, Impulsive and Non-Impulsive

Table 7-4. Fish Onset of Injury Threshold Distances (meters) for Impact Pile Driving

Table 7-5. Sea Turtle Onset of Injury Threshold Distances (meters) for Impact Pile Driving

Table 7-6. Fish Injury and Behavioral Onset Criteria Threshold Distances (meters) for Vibratory

Hammer Pile Installation and Removal

Table 7-7. Sea Turtle Injury and Behavioral Onset Criteria Threshold Distances (meters) for Vibratory

Hammer Pile Installation and Removal

Table 7-8. Fish Injury and Behavioral Onset Criteria Threshold Distances (meters) for Drilling

Operations

U.S. Coast Guard Station Siuslaw River vi

Table 7-9. Sea Turtle Injury and Behavioral Onset Criteria Threshold Distances (meters) for Drilling

Operations

Table 7-10. Potential Sources of Turbidity During In-water Work

Table 7-11. Effects to OC Coho Salmon PBFs in the Action Area

APPENDICES

A: Essential Fish Habitat (EFH) Assessment

B: Draft Project Plan Sheets

LIST OF ACRONYMS

BA Biological Assessment

BMPs Best Management Practices

CFR Code of Federal Regulations cfs Cubic feet per second

CH Critical Habitat

CHU Critical Habitat Unit cy Cubic yard dB Decibel dBA A-weighted decibels

DPS Distinct Population Segment

EFH Essential Fish Habitat

EPA U.S. Environmental Protection Agency

ESA Endangered Species Act

ESU Evolutionarily Significant Unit

HAPC

IWWW

Habitat Areas of Particular Concern

In-Water Work Window

IC Impaired Condition

IPaC

LID

MLB

MHHW

Information for Planning and Consultation

Low Impact Development

Motor Lifeboat

Mean Higher High Water

MSA Federal Magnuson-Stevens Fishery Conservation and Management Act

NMFS National Marine Fisheries Service

U.S. Coast Guard Station Siuslaw River vii

NOAA National Oceanic and Atmospheric Administration

NPDES National Pollutant Discharge Elimination System

NPF Not Properly Functioning Condition

ODEQ Oregon Department of Environmental Quality

OHWM Ordinary High Water Mark

PAH Polycyclic Aromatic Hydrocarbons

PBF

PGIS

Physical or Biological Feature

Pollution-Generating Impervious Surface

PFC Properly Functioning Condition

PFMC Pacific Fisheries Management Council

SPCC Spill Prevention, Control, and Countermeasures

SWPPP

TESC

Stormwater Pollution Prevention Plan

Temporary Erosion and Sediment Control

TTS Temporary Threshold Shift

USACE United States Army Corps of Engineers

USCG United States Coast Guard

USFWS U.S. Fish and Wildlife Service

Draft Biological Assessment

U.S. Coast Guard Station Siuslaw River 1

1.0 INTRODUCTION

1.1 PURPOSE OF THE BIOLOGICAL ASSESSMENT

This Biological Assessment (BA) addresses the effects to Endangered Species Act (ESA)-listed and proposed species and their designated critical habitats from the proposed action that is intended to replace a boathouse and associated structures and correct shoreline erosion at the United States

Coast Guard (USCG) Station Siuslaw River (Station) in Florence, Oregon. The USCG is the lead federal agency for this proposed action, titled the USCG Station Siuslaw Construct Covered Moorings and Correct Shoreline Erosion Project (project).

Potential effects to Essential Fish Habitat (EFH) designated under Section 305b2-4 of the Magnuson-

Stevens Act are also addressed. This BA addresses the proposed action in context with Section 7 of the ESA of 1973, as amended, and assures that through consultation with the National Marine

Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS), actions do not jeopardize the continued existence of any threatened, endangered, or proposed species, or result in the destruction or adverse modification of critical habitat (CH).

1.2 BACKGROUND

The USCG is proposing to correct shoreline erosion and replace the covered mooring and appurtenant in-water structures at the Station. To correct shoreline erosion, the USCG is proposing a durable, long-term solution through the installation of a tubular interlocking steel pile wall along the length of the

Station property waterfront. The replacement covered mooring, or boathouse, will be constructed in the same location as the existing covered mooring with a slightly larger footprint and with a structure engineered to withstand the elements and future riverbed scour (deepening).

The Station was established at this site in 1917. Remodeled in the late 1980’s, the Station has upland facilities for administration and operations personnel, service buildings, berthing for on-duty personnel

(Ready Crew), eight housing units, and limited parking situated on the sand bluff. West of the Station, the sand bluff slopes down steeply approximately 40 feet to the Siuslaw River. An offshore boathouse

(covered mooring) with floating docks and debris screen provides covered and open berths for two 47-foot Motor Lifeboats (MLBs) and one 29-foot Response Boat – Small (RB-S II). The Station’s primary mission is Search and Rescue (SAR) operations for commercial mariners, recreational boaters, and surfers. Other missions include escorting fishing vessels across the Siuslaw River bar, towing and marine salvage assistance, environmental protection and fisheries conservation enforcement, maritime law and treaty enforcement, and boating safety regulation enforcement.

The covered mooring is approximately 50 years old, and inspections of the covered mooring and in-water facilities, and past studies of shoreline erosion, revealed that the foundation is threatened by river bottom deepening and is severely overstressed. Shoreline erosion and river bottom scouring threatens both access to, and stability of, the waterside facilities, and the potential for failure of the sand bluff threatens the stability of landside infrastructure. The Station's fuel tank was relocated due to eroding hillside and loss of station land at the top of the sand bluff.

U.S. Coast Guard Station Siuslaw River 2

Since at least 1961, the Station has experienced both severe erosion of the shoreline and subsidence caused by loss of bottom material and river deepening. River currents, tidal flows, and wave energy result in a high-energy environment along the project area shoreline. Past studies indicate that the underlying sedimentary bedrock is eroding at an approximate rate of 1 to 2 feet per year, and the vertical face of the bedrock is visible at the toe of the sand bluff. Investigations into the mechanics of the bluff failure indicated that surface water and precipitation infiltrate into the younger unconsolidated sands and then abruptly travel laterally when they reach the marine terrace deposits.

The USCG implemented a bank stabilization project in 2016 that resulted in placement of a riprap revetment along 220 feet of its shoreline both above and below Mean Higher High Water (MHHW). The revetment project has temporarily slowed the rate of erosion, but a permanent solution that addresses groundwater flow, erosive forces associated with the tidal riverine environment, and scour of the riverbed is needed to mitigate the long-term effects and enable the Coast Guard to maintain operations while preventing future erosion and scouring of the sand bluff and shoreline along the property.

The USCG completed an Environmental Feasibility Study in 2018 which evaluated several alternatives for correcting the shoreline erosion and identified a preferred alternative. The USCG has also developed a preferred alternative to replace the covered mooring. The elements for the preferred shoreline erosion correction and covered mooring replacement alternatives are described in detail in

Section 2.

1.3 PURPOSE AND NEED FOR THE PROPOSED ACTION

The purpose of the project is to correct shoreline erosion and replace the covered mooring with an interior floating dock for two 47’ MLBs, a pier access bridge, and a debris screen within the same location as the existing structures.

The project is needed to ensure the Station can fully meet its mission. On-shore and in-water assets must enable the Station, designated Heavy Weather and Surf, to maintain its Bravo-Zero response standard. This means maintaining the two surf-ready MLBs, and the loss of the covered mooring would interrupt the ability of the station to maintain these boats. If use of the covered mooring at the Station was lost, the Station would need to lease moorings elsewhere upriver which would significantly increase their response time and therefore potentially result in loss of life.

Continued sand bluff erosion will jeopardize more station infrastructure at the bluff onshore edge and adjacent upland facilities. The project would preserve waterfront operations at the Station by correcting the shoreline erosion and scouring and protecting the sand bluff upon which Station infrastructure is established from further erosion. In addition, the covered moorings, built in 1970, are beyond their serviceable life, and the foundation and pile supports have been compromised by the river bottom scour which directly impacts the structural stability of the covered mooring. By replacing the current foundation and supports, the project would help to ensure mission readiness and public safety.

1.4 FEDERAL NEXUS AND CONSULTATION HISTORY

As the lead federal action agency, the USCG has determined its proposed action may affect ESA-listed anadromous fish species, so the USCG is required to consult with NMFS.

U.S. Coast Guard Station Siuslaw River 3

The USCG has not initiated any previous ESA consultations for this project. The Oregon Coast Branch of the Oregon – Washington Coastal Area Office of NMFS in Roseburg, Oregon is anticipated to oversee consultation for this proposed project.

2.0 PROJECT DESCRIPTION

2.1 PROJECT LOCATION

The Station is located on the river right (east) bank at river mile (RM) 1.5 of the Siuslaw River approximately three miles north-northwest of the downtown waterfront of the City of Florence, Oregon

(Table 2-1; Figure 2-1). Vegetated dunes in the Oregon Dunes National Recreation Area, protected by a series of four rock groin structures, are located on the bank of the Siuslaw River opposite of the

Station.

Table 2-1. Project Location Details

Attribute Description

Township, Range, Section T18S, R12W, Sec. 15

Latitude, Longitude (centroid, decimal degrees) 44.00202°, -124.122277°

Nearest City Florence, OR

County Lane

HUC – 6

th Field Bernhardt Creek-Siuslaw River – 171002060804

Siuslaw River Mile (RM) RM 1.5

Current Land Ownership Department of Homeland Security

U.S. Coast Guard Station Siuslaw River 4

Figure 2-1. Project Location Map

U.S. Coast Guard Station Siuslaw River 5

2.2 PROJECT FOOTPRINT

The project footprint, or the limits of direct construction-related ground disturbance, will include onshore and offshore areas of disturbance within the project area. Onshore disturbance, or disturbance above the highest measured tide (HMT), will include upper slope stabilization measures including a new sheet pile wall and a retaining wall, site preparation, demolition, excavation and fill in uplands for stormwater infrastructure improvements, stockpile areas, and fencing to accommodate slope stabilization measures. Offshore disturbance, or disturbance below the HMT elevation, will include removal of up to

71 existing timber and steel H-piles, the boathouse superstructure and pier access bridge, and fixed debris screen supports; and installation of up to 79 replacement steel piles for replacement of the boathouse, access pier bridge, and fixed debris screen.

2.3 PROJECT ELEMENTS

2.3.1 Onshore Stormwater Infrastructure Improvements and Sitework

The existing, upland storm drain system consists of storm drain pipes and structures, and a below-surface horizontal drain array that collects at a triangular soil nail wall catchment area. The collected stormwater and groundwater are combined to discharge near the top of the slope through a controlled outfall protected with rip rap.

Stormwater improvements will include minor modifications including some Low Impact Development

(LID) storm system features that will reduce erosion and sedimentation loss at the project site. No additional impervious surface area will be added as part of the project. The concept is to adjust the existing storm drainage system and convey the stormwater to a single outfall and discharge beyond the new sheet pile wall onto an energy dissipater. Existing drainage structures will be retrofitted with manufactured treatments such as filter inserts for water quality treatment and LID best management practices (BMPs) will be incorporated where feasible to meet the City of Florence stormwater design standards. BMPs included in final designs may include but would not be limited to bioswales with engineered soils/gravel and a subsurface drain to emphasize filtration, storage, and evaporation and transpiration before runoff is conveyed to the outfall. The project will likely result in a slight, net decrease in existing impervious surfaces. The project will include the following onshore stormwater infrastructure improvements:

Addition of drainage swales with gravel trench drains to redirect runoff from the embankment and to slow down the surface flow and collect groundwater flow. The stormwater in the swale will discharge into the triangular soil nail wall catchment area prior to outfalling through a controlled outlet structure.

Addition of a trench drain to collect stormwater runoff currently flowing down the pier access driveway and over the embankment. The trench drain will redirect the runoff into a drainage structure which will release runoff at a controlled rate and prevent stormwater discharge onto the steep slope.

Retrofit or replacement of existing catch basins with water quality filtration unit(s) to treat runoff from impervious surfaces considered to be a significant source of pollutants in stormwater runoff, or pollution generating impervious surfaces (PGIS), before being conveyed and discharged from an outfall at the riprap layer. Filtration units specifically designed to capture specific pollutants such as zinc, copper, and sediments will be installed.

U.S. Coast Guard Station Siuslaw River 6

Reconstruction of drainage outlet structure including water quality filtration inserts.

A grassy swale underlain by a gravel trench will be installed along the top of the steep slope to collect lawn area surface sheet flows and shallow subsurface flows and convey them to the outfall onsite.

A surface-mounted storm outfall pipe anchored to the embankment slope will replace the existing outfall. The new outfall will discharge beyond the new sheet pile wall to an energy dissipater to prevent embankment erosion at the upper elevation.

Minor asphalt pavement repairs in the parking lot where the embankment failure occurred.

Shoreline stabilization including pile walls, a retaining wall and embankment reestablishment with native vegetation as described in the following section.

2.3.2 Shoreline Stabilization

Shoreline stabilization will be accomplished through construction of an upland, steel interlocking pile wall, with the top of the above-grade portion of the wall above the 50-year calculated extreme tide level

(Figure 2-2). The wall will run approximately 400 feet along the top of bank from approximately the north property line to the south property line, with approximately 30 foot returns inland and upslope at either end. The wall will implement a long-term solution by adding a rigid structure consisting of steel sheet or pipe piles, with grouted soil tie-back anchors located near the top of the wall, that would retain the slope sands, and mitigate negative scour effects on the soils landward of the wall. A drainage element (e.g., weep hole) through the wall at the elevation of the Paleosol contact with the Upper Dune

Sand will allow the free draining retention system, such as a nonwoven geotextile or an open-graded aggregate filter, to relieve groundwater flow and prevent piping (loss) of dune sand material.

Figure 2-2. Typical section for the preliminary design of a bulkhead wall, with the top of the wall above the 50-year extreme tide level.

Sheet or pipe pile installation would be a combination of auger predrilling and/or hydraulic press-in installation, as opposed to driven or vibratory installation approaches, which were determined to be less desirable as primary methods of installation, considering the hardness of the Lower Dune Sand layer and the potential for negative impacts to the marginally unstable slope. The wall is planned to be

U.S. Coast Guard Station Siuslaw River 7 installed above HMT, just upslope of the existing riprap installed in 2016, which will be disturbed as little as possible. It should be noted that scour forces in the river at this location are significant and have changed the depth of the riverbed to a great extent in this location over the last sixty years. It is entirely possible that future scour will remove more bank material and remove or relocate the riprap and leave a more significant wall height exposed on the river side. The wall will be structurally designed for this potential future retained height.

Upslope of the proposed pile wall, protection against seepage-induced erosion and washout of lower sands will be provided to prevent undermining and erosion of the silt layer. The sand slope above the wall will be graded to maximum slope of 2H:1V and stabilized and protected through application of a geocell cellular confinement geotextile, nonwoven geotextile filtration system with granular stone embankment material, biotic soil media planted with native vegetation or a combination thereof.

Several surface swales with gravel trench drains will be added to divert surface runoff from sheet-flowing down the embankment and channeling them to the existing underground storm drain system.

The existing outfall at the downstream end of the stormwater system will be extended with a pipe that will be placed at-grade with cutoff concrete collars and outfall beyond the new wall.

A second, smaller wall is proposed near the crest of the slope at the edge of the existing parking lot in the southwest corner of the property. This wall will be a cantilevered design, with the pile embedment taking into consideration the regraded slope of 2H:1V.

2.3.3 Offshore Infrastructure Demolition and Replacement

The Station’s existing covered mooring, bridge, and debris boom will be demolished, and all piles will be removed. Piles supporting the boathouse to be removed include the original timber vertical piles and timber batter piles installed in 1969, and steel H-piles installed in 2008. Demolition debris and materials will be transported to a permitted landfill and/or recycling facility. In total, approximately 71 piles will be removed by vibratory hammer. A conservative estimate for vibratory extraction is 15 minutes per pile. If any timber piles break during removal, the remaining portion of the broken piles will be cut two feet below the mud line. Removed piles will be disposed of in an upland location.

The following new facilities will be constructed: a 4,730 square foot (SF), two-bay covered mooring, including an interior floating dock for two 47’ MLBs, a mezzanine and deck space for engineering shop, storage, PPE and HAZMAT; a 1,220 SF pedestrian bridge, including a small marine diesel fueling platform; a 520 SF exterior floating dock; and a vertical debris screen . Total overwater structures will cover approximately 6,500 SF. It is estimated that up to 79 replacement steel piles will be necessary to reconstruct the boathouse, floating docks, bridge, and debris screen. The new piles will be 16-inch to

20-inch steel pipe piles filled with concrete, and/or 14-inch steel H-Piles which will be installed by vibratory driving and driven to the final tip elevation by impact strikes after the initial vibratory set. The exact sizes and quantities of pipe piles used will be determined through the remaining design iterations.

The new pier access and debris screen will be constructed in approximately the same footprint as the existing structures to minimize riverbed soil disturbance and shadowing from overwater structures. The new covered mooring footprint will be approximately 1,800 SF larger than the existing structure. The southeast corner will be placed in the same location but the west end of the structure will extend 30 ft further out into the Siuslaw River to accommodate the two 47 ft MLB’s. The existing covered mooring width is insufficient for mooring the two 47 ft MBLS’s. This will result in additional shadowing compared to existing conditions.

U.S. Coast Guard Station Siuslaw River 8

To mitigate for the additional pilings (approximately eight), and expansion of the covered mooring

(approximately 1,800 square feet), the Applicant is proposing to purchase 2,000 square feet of estuarine credits from the Wilbur Island Mitigation Bank, and is currently coordinating with the Oregon

Department of State lands on the credit approval and purchase. Estuarine wetlands have historically been degraded and lost in the Siuslaw watershed.

2.3.4 Temporary Use of Municipal Facilities

During demolition and construction of the upland and in-water components described in the previous sections, USCG personnel and equipment will make temporary use of mooring and parking facilities found at the downtown waterfront of Florence. Use of these facilities will not require modification of navigation or mooring facilities and will not result in additional in-water disturbance other than minor noise from daily ingress or egress of USCG MLBs. Due to the low impact of this component of the proposed action, it is not discussed further in this document.

2.4 CONSTRUCTION EQUIPMENT AND METHODS

During Phase I, it is anticipated that the installation of the upland pile wall would be from a barge or similar floating work platform which would also serve as the primary staging area. Typical equipment for this work would include a drill or hydraulic rig (or both), an appropriately sized crawler crane or tracked hydraulic excavator (or both) for mounting and operation of the drill or hydraulic rigs operated from a spud barge, and a support and materials barge. A small support boat and barge tug would be required periodically for positioning equipment or materials. To facilitate construction of the pile wall a bench will be needed on the upper slope (above HMT) for access or another similar means to construct the wall and install the tie-backs. The upper slope will be fully restored including invasive removal and native revegetation with a contractor-required establishment and maintenance period.

During Phase II, upland site and stormwater infrastructure work will require a staging area designated within the Station’s property for heavy equipment and materials. A temporary stockpile area or areas will also be designated. Temporary erosion and sediment control BMPs, including outlet protection, inlet protection, biofilter bags, stabilized construction entrances, sediment fencing, and straw wattles as appropriate for site conditions will be installed prior to ground disturbance. Typical equipment for this work would include one or more appropriately sized tracked hydraulic excavators, wheel loader, track loader, on-road dump truck(s), water pumps, pavement sawing equipment, compacting equipment, paving machinery, and common landscaping equipment. Excavated materials will either be stockpiled for reuse or removed from the site to a permitted landfill as per the final plans and specifications.

Disturbed natural area grades and vegetation will be restored upon completion of stormwater infrastructure upgrades and sitework.

Piling removal is expected to be accomplished with a vibratory pile driver/extractor mounted to a crawler crane operated from an appropriately sized spud barge. Removed piles will be staged on a second demolition debris barge for transportation. All pier pilings and timbers to be demolished are either steel, or wood creosote or salt treated. The contractor will be required to ensure that these timbers are handled and disposed of in accordance with applicable local, state, and federal regulations.

The contractor will also be required to perform all required sampling and analysis and provide any required shipping and disposal paperwork. In addition, if any unidentified or unexpected hazardous materials are discovered during demolition work, the contractor will be required to immediately notify the USCG prior to commencing any further cleanup of the discovered materials.

U.S. Coast Guard Station Siuslaw River 9

Construction of the offshore infrastructure would be accomplished from a barge, or multiple barges, using similar equipment as described above for installation of the pile wall. It is assumed that up to three piles will be driven each 8-hour workday. The actual driving time for each pile could be as much as approximately one hour but is anticipated to be less. Thus, an estimated 29 total days of pile driving

(not all consecutive) will occur over the duration of the project. A full pile driving analysis will be completed to further refine and guide pile installation and the appropriate BMPs for pile installation.

Smaller work vessels and platforms will be utilized to construct the covered mooring superstructure.

Exact equipment requirements and construction means and methods for both phases will be determined through ongoing studies, surveys, and the design-build contractor’s design process using the final engineering designs, specifications, and estimates.

2.5 MLB OPERATIONS AND MAINTENANCE

Noise sources during operations include light and medium duty machinery needed to maintain, load, and unload motorized lifeboats (MLBs) as well as light traffic and human presence. Noise from MLB diesel engines will be audible in the immediate vicinity of the vessels but will not be noticeable outside of the immediate area. Fueling, compressed air, and oily water disposal services would be provided by outside service contractors. During operations, USCG will comply with state and federal regulations for storing, using, and transporting hazardous materials, including creating and maintaining an emergency response plan in case of accidental release.

Minor increases in turbidity may result from propeller wash when MLBs are entering or exiting the mooring area. Such effects will be limited to the area immediately surrounding the boathouse and floating docks, since the MLBs are shallow draft vessels and their primary transit route to and from the mooring area will be via deeper water of the Federal Navigation Channel, which is maintained for depths that will not be affected by turbulence from propellers.

2.6 CONSTRUCTION SCHEDULE

The proposed action at the Station is anticipated to occur over an approximate two-year period in two phases, depending on environmental and regulatory requirements, final plans and specifications, and options awarded to the contractor. It is also noteworthy that procurement of materials such as the steel sheet piling may affect the schedule. The USCG will complete work to occur below the HMT elevation during the ODFW-preferred in-water work window (IWWW) from November 1 to February 15. Over-water construction actions, or those action which will be performed waterward of HMT but above the elevation of HMT, may be performed outside of the IWWW subject to contractor means and methods complying with permitting and ESA consultation conditions.

Based on preliminary project acquisition planning, Phase I of construction will likely commence in

September – October 2024 with the mobilization of materials and equipment to construct the steel interlocking pile wall for shoreline stabilization. Mobilization and staging of materials and equipment for the demolition and construction of the offshore infrastructure would follow and in-water work for offshore infrastructure would occur from November 1, 2024, through February 15, 2025. Remaining overwater work to construct the covered mooring superstructure may extend beyond the IWWW.

U.S. Coast Guard Station Siuslaw River 10

Phase II of construction will begin in approximately June 2025. Work to improve the site stormwater infrastructure will occur from June to approximately late August or early September to coincide with the usually drier weather conditions.

3.0 CONSERVATION MEASURES

Conservation measures will be implemented during construction to avoid or minimize potential adverse effects to protected species covered by this BA. Some measures, particularly those covering hazardous materials, may also apply to operations and/or maintenance of the proposed action.

General conservation measures for implementation during construction are worker environmental rules and regulations awareness training and construction best management practices (BMPs) to avoid or minimize construction activity effects on the sensitive site resources (habitats and species). Other specific measures are outlined below.

3.1.1 Water Quality

Placement of floating silt curtains or similar in-water turbidity barriers around the in-water work area to prevent migration of disturbed fine sediments away from the area of in-water work.

Best engineering and management practices will be employed to minimize water column discharges.

Implementation of a turbidity monitoring framework consistent with the Oregon Department of

Environmental Quality 401 water quality certification, permit terms and conditions, and ESA consultation conservation measures.

Implementation of a Stormwater Pollution Prevention Plan (SWPPP).

Implement a site-specific Temporary Erosion and Sediment Control (TESC) plan to minimize erosion and sedimentation with site appropriate BMPs.

Install and maintain appropriate TESC measures prior to disturbance to avoid and minimize effects to waterbodies, wetlands, and stormwater treatment facilities resulting from clearing, grading, and management of site drainage. This may include placement of silt fencing, wattles, dewatering sediment basin(s), or other protective barriers to ensure that soils are not introduced into waterways.

Revegetation and mulching of disturbed upland areas to minimize runoff of fines during precipitation events.

The construction contractor will limit the amount of soil disturbance to that which can be adequately controlled via constructible BMPs.

Construction entrances will contain either rock pads or tire wash facilities to prevent tracking of soil onto local roadways and to prevent the potential for sedimentation and turbidity of receiving waters as a result of runoff from roadways.

Stockpile areas will be contained and protected by erosion control measures such as silt fencing and straw bales. Stockpiles shall also be covered if inclement weather is forecast.

Appropriate stockpile and staging areas will be identified and approved prior to construction.

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3.1.2 Noise and Vibration

Placement of bubble curtains, properly configured for the water velocity, around 100% of the piling perimeter and full water column when using impact hammers for piling installation.

A soft-start technique will be used during pile driving to allow fish (and marine mammals) to vacate the area before the pile driver reaches full power. For vibratory hammers, the contractor will initiate the driving for 15 seconds at reduced energy followed by a 1-minute waiting period. This procedure shall be repeated two additional times before continuous driving is started. For impact driving, an initial set of three strikes will be made by the hammer at 40 percent energy, followed by a 1-minute waiting period, then two subsequent three-strike sets before initiating continuous driving.

Noise and vibration mitigation through use of devices to muffle equipment, use of quieter equipment, and proper maintenance of marine vessels and equipment.

3.1.3 Hazardous Materials

Implementation of a Spill Prevention, Containment, and Countermeasure (SPCC) plan. Maintain a current copy of approved SPCC plan on-site for the duration of the project and ensure that no work or staging occurs prior to implementing the plan. The approved plan provides site- and project-specific details identifying potential sources of pollutants, exposure pathways, spill response protocols, protocols for routine inspection fueling and maintenance of equipment, preventative and protective equipment and materials, and emergency notification and reporting protocols. Ensure that all workers understand the plan and response and reporting standards.

Absorbent materials will be employed if petrochemical sheen is observed and kept in place until sheen dissipates.

Clean and inspect all equipment to be used for the construction activities prior to arriving at the project site. Ensure that no potentially hazardous materials are exposed, no leaks are present, and that equipment is properly functioning.

An in-water debris boom and oil adsorbent boom will be deployed around all active work areas and in-water equipment during construction and demolition to ensure containment of materials, wastes, debris, and/or contaminants. Care will be taken to prevent debris from entering the water during demolition and construction, and debris will be removed promptly if it does enter the water. Any contaminated wastes will be disposed of at a properly permitted disposal site.

Pile removal BMPs will be employed to prevent potential contaminant release into the environment and include vibratory extraction methods, keeping extraction equipment out of the water, and use of a containment basin on the barge where removed piles will be placed and temporarily stored.

Staging area and storage areas will be designated to store materials, fuel, and equipment.

Equipment will be staged at least 150 feet from any natural water body or wetland to avoid contamination of water bodies or sediments.

Utilize BMPs for controlling pollution from ship mooring and fueling facilities during MLB operations.

3.1.4 Habitat Disturbance or Alteration

To control spread of non-native species, construction equipment will be washed before mobilization, and clean fill material will be required as necessary. The contractor will be required to inspect marine

U.S. Coast Guard Station Siuslaw River 12 equipment. Existing non-native or invasive species will be controlled as feasible without use of pesticides on the site to promote native vegetation growth and dominance.

Riparian vegetation will be preserved to the extent practicable while still allowing constructability.

Tree removals shall be mitigated per applicable local land use ordinances.

Disturbed soils shall be seeded with native species immediately as construction phasing allows.

3.1.5 Collision

All vessels will be restricted to 10 knots (~11.5 mph) speed over ground limit or less where required by the City of Florence in the Siuslaw River estuary.

A monitoring zone of 500 feet will be maintained for all marine mammals.

4.0 ACTION AREA

The ESA requires that potential effects to listed species and those proposed as endangered and threatened be evaluated in relation to the complete extent of area influenced by the proposed action

(the “action area”) (50 CFR 402.02). The action area is defined as all areas to be affected directly or indirectly by the federal action and not merely the immediate area involved in the action (50 CFR

402.02). The project action area includes the project footprint, all terrestrial areas which could be affected by noise extending beyond the project footprint in exceedance of species’ thresholds, and the aquatic area potentially impacted from underwater noise and increased suspended sediment and turbidity from construction activities.

4.1 PROJECT FOOTPRINT

The project footprint, or the limits of direct construction-related ground disturbance, will include upland areas of disturbance associated with site preparation, stockpiling, demolition, excavation and construction for stormwater utilities, road, and parking and hardscape area improvements. It includes the steep embankment of the sand bluff and the shoreline above the 50-year extreme tide level where the pile wall for shoreline stabilization will be constructed. Below the HMT elevation, riprap movement, salvage, and placement as well as piling removal and installation are in-water work activities that will directly disturb the aquatic bed and affect the surrounding water column.

The action area is larger than the project footprint. Of the construction activities discussed above in section three, temporary effects of the action that may extend beyond the project construction footprint include airborne and underwater noise impact area, altered water and sediment quality, and the effects associated with an increase in human activity. The continued discussion of the action area zones of effect discussed below is a conservative estimate of the extent to which water quality impacts could result from the proposed action should BMPs fail, and in which noise disturbance from construction activities has the potential to affect fish and wildlife species.

4.2 NOISE

Noise is most often defined as unwanted sound. Disturbance, in an ecological context, is an event causing some environmental stress over a relatively short period of time. Construction of the proposed

U.S. Coast Guard Station Siuslaw River 13 project will generate point source noise and disturb the surrounding environment. If an animal exhibits behavior in response to a noise disturbance which suggests its safety or survival is at significant risk or that its reproductive effort is potentially compromised, then a noise disturbance may be considered harassment and an adverse effect to wildlife.

Acoustic modeling was performed to analyze the underwater acoustic impacts associated with in-water construction using dBSea software. The underwater sound propagation modeling results, modeling environment, and acoustic conceptual information for underwater acoustics are presented in the acoustic assessment with ranges to the various acoustic threshold levels in tabular and graphical

(sound contour plots) formats (Tetra Tech 2023). Terrestrial noise generated from project construction activities was assessed using the most recent guidance and terrestrial noise spreadsheet provided by the Washington State Department of Transportation (WSDOT 2021).

4.2.1 In-air Noise

The City of Florence has established noise regulations within the City Code Title 6, Section 6-1-2-3:

Unnecessary Noise. The City Code limits noise at the boundary of a noise sensitive property to the following:

50 dBA between the hours of 10:00 p.m. and 7:00 a.m., 60 dBA between the hours of 7:00 a.m. and 10:00 p.m., or

Is plainly audible between the hours of 10:00 p.m. and 7:00 a.m. within a noise sensitive unit, which is not the source of the sound.

Equipment commonly used in construction including hammers, saws, pile drivers, earth moving equipment, compressors and similar equipment is not limited during daytime hours but must comply with the nighttime noise limits (10:00 p.m. – 7:00 a.m.).

USCG Station operations, commercial vessel and recreational boat operations in the Siuslaw River, and traffic along Rhododendron Drive are the primary sources of in-air noise in the project area and immediate vicinity. Land uses in the vicinity of the project include residential, community commercial, and recreational. Received sound levels will fluctuate, depending on the construction activity, equipment type, and distance between noise source and receiver. Construction sound will be attenuated as distance from the source increases, and other factors such as site topography, vegetation, and temperature can further reduce noise over a distance.

Elevated in-air sound levels, generally in excess of 90 dB (as experienced by the receptor), may disrupt normal behavioral patterns and affect wildlife in various ways. The loudest in-air, point source noise generating activity associated with the project will be the use of a diesel pile hammer (impact equipment) used to drive piles. Although limited in overall duration and variable in noise levels based on substrate and other exact variables of the impact and the piles themselves, this activity is estimated to generate a maximum in-air sound level of 105 dBA (as measured from a 50-foot distance from hammer; WSDOT 2021). The in-air noise calculator results indicate sound levels from construction point source noise, including pile driving, may travel up to 5,181 feet from the source in soft site conditions and up to 12,343 feet from the source in hard site conditions before attenuating to traffic or background noise levels. Hard site conditions exist to the west of the project area over the Siuslaw

River and eventual Pacific Ocean and soft site conditions exist to the east over the vegetated land areas.

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4.2.2 Underwater Noise

Pile installation by vibratory set and impact proofing, barging, and marine vessel activities associated with project construction will temporarily increase sound levels in the aquatic environment above background levels. Background noise from natural sources in the marine environment comes from physical and biological processes.