Mill River Dams Feasibility Study River Restoration and Diadromous Fish Passage January 31st, 2008 Prepared for: Massachusetts Riverways Program Riverways Program, DFG 251 Causeway St., Suite 400 Boston, MA 02114 3602 Atwood Avenue Suite 3 Madison, WI 53714 TABLE OF CONTENTS 1. Executive Summary........................................................................................................ 5 1.1. State Hospital Dam ................................................................................................ 5 1.2. West Britannia Dam............................................................................................... 8 1.3. Whittenton Pond .................................................................................................... 9 2. Introduction .................................................................................................................. 13 2.1. Project Team and Scope of Work ........................................................................ 15 2.2. Report Format...................................................................................................... 15 3. Data Collection............................................................................................................. 16 3.1. Existing data ........................................................................................................ 16 3.2. Field data.............................................................................................................. 16 4. Background Information............................................................................................... 20 4.1. Natural History .................................................................................................... 20 4.2. Fisheries History.................................................................................................. 20 4.3. Cultural Resources............................................................................................... 21 4.4. Geologic history................................................................................................... 27 4.5. Geomorphic History ............................................................................................ 28 5. Existing Conditions ...................................................................................................... 30 5.1. Modern landuse.................................................................................................... 30 5.2. Existing Geomorphology..................................................................................... 31 5.3. Wetland Resources .............................................................................................. 32 5.4. Basis for projecting wetland resource alterations ................................................ 35 6. Hydrologic and Hydraulic Analysis ............................................................................. 38 6.1. Hydrology ............................................................................................................ 38 6.2. Hydraulic Modeling and Flood Profile Analysis ................................................. 48 2008 Inter-Fluve Inc. 6.3. Fish Passage Hydraulic Design............................................................................ 58 7. Sediment Characterization............................................................................................ 65 7.1. Sediment volume estimation................................................................................ 65 7.2. Sediment Grain Size Analysis ............................................................................. 65 7.3. Due diligence ....................................................................................................... 66 7.4. Sediment quality – background information........................................................ 67 7.5. Sediment quality – State Hospital........................................................................ 69 7.6. Sediment quality – West Britannia ...................................................................... 70 7.7. Sediment quality – Whittenton Pond ................................................................... 72 7.8. Regulatory Perspectives on Quality Testing Results in Relation to Project Implementation .................................................................................................... 73 8. State Hospital Dam: Design Options............................................................................ 76 8.1. Existing Conditions (No action or minimal action alternative) ........................... 76 8.2. Full removal......................................................................................................... 80 8.3. Fish passage bypass channel................................................................................ 84 8.4. Conceptual Cost Estimates – State Hospital Dam ............................................... 87 9. West Britannia Dam: Design Options .......................................................................... 89 9.1. Existing Conditions (Do Nothing Option)........................................................... 89 9.2. Full removal......................................................................................................... 93 9.3. Rock ramp (with dam repair)............................................................................... 97 9.4. Fish bypass channel (with dam repair) ................................................................ 98 9.5. Fish ladder (with dam repair)............................................................................... 99 9.6. Conceptual Cost Estimates – West Britannia Dam............................................ 101 10. Whittenton Pond Dam: Design Options ..................................................................... 102 10.1. Existing Conditions (No action or minimal action alternative) ......................... 102 10.2. Full removal – Whittenton Dam ........................................................................ 107 2008 Inter-Fluve Inc. 10.3. Fish ladder (with dam reconstruction) ............................................................... 115 10.4. Fish bypass channel (with dam reconstruction)................................................. 116 10.5. Rock ramp (with dam reconstruction) ............................................................... 116 10.6. Conceptual Cost Estimates – Whittenton Pond Dam......................................... 119 11. Morey’s Bridge Dam: Recommendations .................................................................. 120 12. Citations...................................................................................................................... 121 Appendices Appendix A – Detailed cost estimates Appendix B - Due diligence summary Appendix C – Natural resources report Appendix D – HEC-RAS modeling results/summary tables Appendix E – Geolabs Report Appendix F – Infrastructure notes Appendix G – Fish Passage computations Principal authors: Martin Melchior, Michael Burke, and Michael Chelminski 2008 Inter-Fluve Inc. 1. Executive Summary This study examined the feasibility of various fish passage and river restoration options for the three downstream impoundments on the Mill River in Taunton, Massachusetts (Figure 1-1). We conclude that fish passage and river restoration are feasible, and we offer concept level design options for alternatives at each dam. 1.1. State Hospital Dam The State Hospital Dam is an earthen fill dam with a concrete spillway (8 ft head) impounding a pond area of approximately 5.2 acres. The impoundment contains a maximum of 30,000 cubic yards of deposited sediment consisting primarily of sand. No Action Alternative – As part of the study, we examined the implications of no action at each structure. No action at the State Hospital Dam would result in continued riverine habitat degradation through sediment deposition, organic material buildup, invasive plant proliferation, thermal pollution, and concentration of nutrients and pollutants. These negative effects of dams are well documented in numerous studies (Baxter 1977, Dauta et al. 1999, Petts 1984, Poole and Berman 2001, Schuman 1995, Stanley et al. 2002, Ward and Stanford 1979, 1987). No action also results in continued selective removal of fine material from the downstream reach, resulting in over-widening of the channel and homogenization of in-stream habitats (Gray and Ward 1982, Ligon et al. 1995, Ward and Stanford 1983). No action with regard to river restoration and fish passage will require continued dam inspection, maintenance and eventual repair or replacement to keep the dam in compliance with Massachusetts Department of Dam Safety standards. The cost of these activities is typically borne by the dam owner. All dams continue to degrade, and without regular maintenance and repair, the risk of flooding due to dam failure increases. No action results in continued liability risk to the dam owner and continued risk to public safety (Graber et al. 2001). Dam Removal Alternative – Removal of the State Hospital Dam is feasible and would fulfill the goals of the project. Dam removal would result in passage for diadramous fish (alewife, blueback herring) and other species (eg. American eel, amphibians), free flowing conditions, restored riparian and in-stream habitat, lower water temperatures, increased dissolved oxygen concentrations and the reestablishment of river dependent fish and