Fisherman's Channel Dredging Draft Initial Study Appendices

358 Pages·2016·9.26 MB·English

by  Heather Waldrop

Appendix A
White Slough Beneficial Reuse Plan Drawings

Appendix B
Eelgrass Mitigation Plan

JANUARY 2016 DRAFT
Eelgrass Mitigation Plan for the  
Fisherman’s Channel Dredging Project  

P R E P A R E D F O R P R E P A R E D B Y
Humboldt Bay Harbor, Recreation, and  Stillwater Sciences
850 G Street, Suite K 
Conservation District 
Arcata, CA 95521 
601 Startare Drive 

Eureka, CA 95501 

Stillwater Sciences
DRAFT Eelgrass Mitigation Plan for the Fisherman’s Channel Dredging Project

Suggested citation:
Stillwater Sciences. 2016. DRAFT Eelgrass Mitigation Plan for the Fisherman’s Channel Dredging
Project. Humboldt County, California. Prepared by Stillwater Sciences, Arcata, California for the
Humboldt Bay Harbor, Recreation, and Conservation District, Eureka, California.

Cover photos: Photos taken by Stillwater Sciences 2014–2015. Eelgrass at mouth of Fisherman’s
Channel (top left), Fields Landing Mitigation area (top right, bottom right, and bottom left).

January 2016 Stillwater Sciences
i
DRAFT Eelgrass Mitigation Plan for the Fisherman’s Channel Dredging Project

Table of Contents

1  INTRODUCTION AND BACKGROUND ........................................................................... 1 
1.1  Project Description ...................................................................................................... 1 
1.2  Impacts on Existing Eelgrass Beds .............................................................................. 4 
1.3  Regulatory Setting and Compliance Requirements ..................................................... 6 
1.4  Proposed mitigation ratios ........................................................................................... 6 
1.5  Mitigation Approach .................................................................................................... 7 
1.6  Sea Level Rise ............................................................................................................. 9 
2  PROPOSED EELGRASS MITIGATION ............................................................................ 9 
2.1  Existing Ecological Conditions.................................................................................. 10 
2.2  Mitigation Implementation ........................................................................................ 11 
2.2.1  Piling removal ..................................................................................................... 11 
2.2.2  Gravel/cobble fill excavation .............................................................................. 12 
2.2.3  Eelgrass establishment ........................................................................................ 12 
2.2.4  Best management practices ................................................................................. 13 
2.3  Mitigation Goals and Performance Criteria ............................................................... 13 
2.4  Monitoring ................................................................................................................. 14 
2.4.1  Fields Landing mitigation area ............................................................................ 14 
2.4.2  Fisherman’s Channel dredging area .................................................................... 14 
2.5  Expectation of Success .............................................................................................. 14 
2.6  Sea Level Rise ........................................................................................................... 15 
3  REPORTING ........................................................................................................................ 15 
4  REMEDIAL ACTION PLAN .............................................................................................. 15 
5  LITERATURE CITED ........................................................................................................ 16 

Tables
Table 1. Projected sea level rise1 in Humboldt Bay, per CCC .................................................... 9 

Figures
Figure 1. Project area. ................................................................................................................... 2 
Figure 2. Fisherman’s Channel Dredging Area. ........................................................................... 3 
Figure 3. Existing eelgrass coverage in Fisherman’s Channel overlaid with dredging footprint
and eelgrass impact interval. ......................................................................................... 5 
Figure 4. Fields Landing mitigation area. ..................................................................................... 8 
Figure 5. Remnant pilings and gravel/cobble fill in the mitigation area. .................................... 10 
Figure 6. Eroding shoreline, remnant pilings, and gravel/cobble fill in the mitigation area. ...... 11 

January 2016 Stillwater Sciences
ii
DRAFT Eelgrass Mitigation Plan for the Fisherman’s Channel Dredging Project

1 INTRODUCTION AND BACKGROUND
1.1 Project Description
The Humboldt Bay Harbor, Recreation, and Conservation District (Harbor District) is proposing
to conduct maintenance dredging of Fisherman’s Channel as part of a beneficial reuse dredging
pilot project (Project) to facilitate improved navigation in the channel via dredging and
subsequent beneficial reuse of the dredged sediments for salt marsh restoration at the White
Sough Unit of the Humboldt Bay National Wildlife Refuge (Refuge). Fisherman’s Channel is
located in King Salmon, California, approximately 2.5 miles south of the City of Eureka along
Humboldt Bay (Figure 1). Currently, Fisherman’s Channel is inaccessible to larger vessels at a
lower low tide due to a bar that has formed at the channel entrance. Dredging of the mouth of
Fisherman’s Channel and main channel is proposed to take place in summer or fall 2016. The
areas to be dredged are shown in Figure 2. Dredging activities for the King Salmon residential
canals that connect with the Fisherman’s Channel are not part of this Project because the
feasibility, funding, and timeline for dredging those canals are unknown at this time.

The Project objectives are described in the project description of the California Environmental
Quality Act (CEQA) Initial Study and summarized below:
 Dredge the channel in the Fisherman’s Channel to restore safe and consistent boat
navigation at all tidal heights
 Provide dredged material to the White Sough Unit of the Refuge for beneficial reuse by the
United States Fish and Wildlife Service (USFWS) for salt marsh restoration
 Carry out the Project to provide agencies with operations data that will facilitate future
dredge and beneficial reuse design, permitting, and implementation elsewhere in Humboldt
Bay
 Conduct water quality monitoring that will guide future dredging operations elsewhere
within Humboldt Bay
 Implement and monitor success of eelgrass (Zostera marina) and longfin smelt (Spirinchus
thaleichthys) mitigation
 Establish an acceptable standard protocol for sediment sampling methods and analysis for
future dredging to focus on Constituents of Concern (COC) and possibly reduce
redundancy in the sampling suite
 Provide Harbor District staff with dredging and beneficial reuse experience, particularly to
address boat navigation, habitat restoration, and sea level rise issues within Humboldt Bay
 Inform a Humboldt Bay Sediment Master Plan

Portions of this Project have the potential to impact eelgrass and longfin smelt, requiring
mitigation. The very low risk of take of longfin smelt associated with the Project will be fully
mitigated through implementation of this eelgrass mitigation plan. The purpose of this mitigation
and monitoring plan is to identify the amount of eelgrass habitat that requires mitigation, identify
the location for completing the mitigation requirement, outline mitigation conceptual design and
implementation steps, define performance criteria, describe the monitoring and reporting
protocols, and describe the maintenance and remedial action plans.

January 2016 Stillwater Sciences
1