Environmental Assessment Coquille River Maintenance Dredging
Total Page:16
File Type:pdf, Size:1020Kb
ENVIRONMENTAL ASSESSMENT COQUILLE 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 Coquille River Maintenance Dredging Environmental Assessment EXECUTIVE SUMMARY The Coquille River Navigation Project was authorized by the Rivers and Harbors Acts of June 14, 1880; July 13, 1892; June 25, 1910; March 2, 1919; July 3, 1930; August 30, 1935; and March 2, 1945; and a RHA section 107 project of July 14, 1960. These authorizations include the construction, operation and maintenance of the jetty structures at the entrance to Coquille River and navigational channels and a turning basin. The local sponsor is the Port of Bandon. The purpose of the Coquille River Navigation Project (the “Project”) for the U. S. Army Corps of Engineers (Corps), Portland District is to maintain to maintain the federal navigation channels at their federally authorized depths and widths by periodically removing restricting shoals of naturally occurring sediment material. These ongoing maintenance dredging activities provide adequate channel dimensions for vessel access and use upstream to river mile (RM) 1.3. Snagging operations are authorized to RM 24, however Corps has not performed snag removal for over 20 years nor do they plan to in the near future. Periodic shoals develop within the Coquille River navigation channels due to the buildup of materials from both fluvial and marine origins. Shoals and sedimentation can restrict or prohibit vessel navigation. 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 “critical harbor of refuge” for vessels in need. Two areas are proposed for maintenance dredging as part of the Project: (1) Coquille River Entrance Channel (38,000 cubic yards from RM 0-20 to 1+15); and (2) Bandon Boat Basin Access Channel (9,000 cubic yards from RM 1 south to the marina, less than 1,000 feet). Entrance Channel dredging and placement activities occur between June 15 and October 31 of any given year. The Bandon Boat Basin Access Channel is dredged between July 1 and November 30, after the Entrance Channel dredging is complete. Material from the Entrance Channel is placed at the Offshore Dredged Material Disposal Site (ODMDS), while material from the Access Channel is placed at the ODMDS or in-water Flow-lane Placement Site. Ocean conditions, potential storm surges, inclement weather, and difficulty in crossing the bar to reach the authorized Offshore Dredged Material Disposal Sites (ODMDS) 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 assessments completed for the Project. The analysis finds that the Preferred Alternative would not substantially affect the quality of the environment. June 30, 2015 i Coquille River Maintenance Dredging Environmental Assessment TABLE OF CONTENTS EXECUTIVE SUMMARY ............................................................................................................................... I ABBREVIATIONS AND ACRONYMS ......................................................................................................... V 1. INTRODUCTION ............................................................................................................................ 7 1.1 Purpose and Need ......................................................................................................................... 8 1.2 Authority ......................................................................................................................................... 8 1.3 Funding .......................................................................................................................................... 9 1.4 Project Area ................................................................................................................................... 9 1.5 Background and History .............................................................................................................. 12 1.5.1 Jetty Construction and Repair ............................................................................................ 12 1.5.2 Maintenance Dredging and Improvements ........................................................................ 12 1.5.3 Dredged Material Placement .............................................................................................. 13 2. ALTERNATIVES .......................................................................................................................... 15 2.1 No Action Alternative ................................................................................................................... 15 2.2 Preferred Alternative .................................................................................................................... 15 2.2.1 Proposed Dredge Activities ................................................................................................ 16 2.2.2 Proposed Dredge Material Placement ............................................................................... 17 2.2.3 Proposed Dredge Methods ................................................................................................. 17 2.2.4 Channel/River Management ............................................................................................... 20 3. AFFECTED ENVIRONMENT ....................................................................................................... 21 3.1 Physical Environment .................................................................................................................. 21 3.1.1 Geology .............................................................................................................................. 21 3.1.2 Coastal Processes .............................................................................................................. 22 3.1.3 Hydrology ............................................................................................................................ 26 3.1.4 Sediment Quality ................................................................................................................ 27 3.1.5 Water Quality ...................................................................................................................... 30 3.1.6 Sound ................................................................................................................................. 31 3.1.7 Air Quality ........................................................................................................................... 32 3.2 Biological Resources ................................................................................................................... 33 3.2.1 Aquatic Plants, Animals and Habitat .................................................................................. 34 3.2.2 Shoreline Terrestrial Plants, Animals and Habitat .............................................................. 36 3.2.3 Endangered Species .......................................................................................................... 36 3.3 Other Resources .......................................................................................................................... 43 3.3.1 Cultural and Historic ........................................................................................................... 43 3.3.2 Socioeconomic ................................................................................................................... 45 3.3.3 Recreation .......................................................................................................................... 46 4. ENVIRONMENTAL CONSEQUENCES ...................................................................................... 48 4.1 Physical Environment .................................................................................................................. 48 4.1.1 Geology .............................................................................................................................. 48 4.1.2 Coastal Processes .............................................................................................................. 48 4.1.3 Hydrology ............................................................................................................................ 50 4.1.4 Sediment Quality ................................................................................................................ 50 4.1.5 Water Quality ...................................................................................................................... 51 4.1.6 Sound ................................................................................................................................. 53 June 30, 2015 ii Coquille River Maintenance Dredging Environmental Assessment 4.1.7 Air Quality ..........................................................................................................................