ENVIRONMENTAL ASSESSMENT CHETCO RIVER MAINTENANCE DREDGING Prepared For US Army Corps of Engineers Portland District PO Box 2946 Portland, OR 97208 Prepared By 600 University Street, Suite 610 Seattle, WA 98101 June 30, 2015 Chetco River Maintenance Dredging Environmental Assessment EXECUTIVE SUMMARY The Chetco River Federal Navigation Project was authorized by the Rivers and Harbors Acts of: March 2 1945, October 27 1965, and December 4 1981; with modifications from the Water Resources Development Act (WRDA) 1992. These authorizations include the construction, operation and maintenance of two jetty formations, and other navigation-related features, and maintenance of the navigation channels through the mouth of the Chetco River. The local sponsor is the Port of Brookings- Harbor. The purpose of the Chetco River Federal Navigation Project (the “Project”) is for the U. S. Army Corps of Engineers, Portland District (Corps), to maintain the Entrance Channel and the Brookings-Harbor Commercial Boat Basin Access Channel at their federally authorized depths and widths by periodically removing channel-restricting shoals of naturally occurring sediment material. These ongoing maintenance dredging activities provide adequate channel dimensions for vessel access and use upstream to approximately river mile (RM) 0.3. By maintaining adequate navigational dimensions, the Project further serves to decrease waiting times and increase navigability for vessels crossing the entrance bar. The main Entrance Channel shoals rapidly in late winter and early spring due to coastal littoral processes. The inner portion of the Entrance Channel and the Boat Basin Access Channel periodically shoal due to a buildup of material from upstream areas and lower fluvial origins. Shoals and sedimentation can restrict or prohibit vessel navigation and dredging to authorized depths and widths is critical to keeping the river and harbor open and to sustaining important navigation components of the local and state economy, as well as maintaining a U.S. Coast Guard (USCG) “critical harbor of refuge” for vessels in need. Two areas are proposed for continued maintenance dredging as part of the Project: (1) the Chetco River Entrance Channel (70,000 cubic yards from RM 0-20 to 0+30); (2) 9,000 cubic yards from the Brookings- Harbor Boat Basin Access Channel. Dredged material is placed within two authorized and approved in- water material placement locations. Dredging and placement activities occur between about June 1 or July 15 to October 31 depending on the specific location (of any given year). Funding, ocean conditions, potential storm surges, inclement weather, and difficulty in crossing the bar to reach the authorized Offshore Dredged Material Disposal Sites (ODMDS) or Nearshore Placement Site all preclude safe and effective operations of necessary dredging activities during the Oregon Department of Fish and Wildlife (ODFW) preferred in-water work period. Most dredging operations work 24-hours per day depending upon weather, staffing, and other factors. Multiple environmental effects from dredging and placement activities on resources in the Project vicinity were considered in this Environmental Assessment (EA), which updates prior environmental June 30, 2015 i Chetco River Maintenance Dredging Environmental Assessment assessments completed for the Project. The analysis finds that the Preferred Alternative would not substantially affect the quality of the environment. June 30, 2015 ii Chetco River Maintenance Dredging Environmental Assessment TABLE OF CONTENTS EXECUTIVE SUMMARY ............................................................................................................................... I ABBREVIATIONS AND ACRONYMS ........................................................................................................ IV 1. INTRODUCTION ............................................................................................................................ 6 1.1 Purpose and Need ......................................................................................................................... 6 1.2 Authority ......................................................................................................................................... 7 1.3 Funding .......................................................................................................................................... 8 1.4 Project Area ................................................................................................................................... 8 1.5 Background and History .............................................................................................................. 11 1.5.1 Jetty Construction and Repair ............................................................................................ 11 1.5.2 Maintenance Dredging ....................................................................................................... 11 1.5.3 Dredged Material Placement .............................................................................................. 12 2. ALTERNATIVES .......................................................................................................................... 14 2.1 No Action Alternative ................................................................................................................... 14 2.2 Preferred Alternative .................................................................................................................... 14 2.2.1 Proposed Dredging Activities ............................................................................................. 15 2.2.2 Proposed Dredge Material Placement ............................................................................... 16 2.2.3 Proposed Dredge and Placement Methods ....................................................................... 16 2.2.4 Mechanical Dredges ........................................................................................................... 18 2.2.5 Channel Management During Dredging ............................................................................. 19 3. AFFECTED ENVIRONMENT ....................................................................................................... 20 3.1 Physical Environment .................................................................................................................. 20 3.1.1 Geology .............................................................................................................................. 20 3.1.2 Coastal Processes .............................................................................................................. 21 3.1.3 Hydrology ............................................................................................................................ 25 3.1.4 Sediment Quality ................................................................................................................ 26 3.1.5 Water Quality ...................................................................................................................... 28 3.1.6 Sound ................................................................................................................................. 29 3.1.7 Air Quality ........................................................................................................................... 30 3.2 Biological Resources ................................................................................................................... 31 3.2.1 Aquatic Plants, Animals and Habitat .................................................................................. 32 3.2.2 Shoreline Terrestrial Plants, Animals and Habitat .............................................................. 35 3.2.3 Endangered Species .......................................................................................................... 36 3.2.3.1 NMFS Jurisdictional Species .............................................................................................. 37 3.3 Other Resources .......................................................................................................................... 42 3.3.1 Cultural and Historical ........................................................................................................ 42 3.3.2 Socioeconomic ................................................................................................................... 44 3.3.3 Recreation .......................................................................................................................... 45 4. ENVIRONMENTAL CONSEQUENCES ...................................................................................... 47 4.1 Physical Environment .................................................................................................................. 47 4.1.1 Geology .............................................................................................................................. 47 4.1.2 Coastal Processes .............................................................................................................. 47 4.1.3 Hydrology ............................................................................................................................ 49 4.1.4 Sediment Quality ................................................................................................................ 50 June 30, 2015 i Chetco River Maintenance Dredging Environmental