Advancing Anadromous Fish Passage Efficiency Lower Shannock ...

Advancing Anadromous Fish Passage EfficiencyLower Shannock Falls Dam RemovalPawcatuck River, Rhode IslandJames Turek 1 , Nils Wiberg 2 , Dick Quinn 3 , Mike Trumbauer 4 ,Kathy Hoverman 4 ,Sean Arruda 2 , Amy Hunt 2 , and Chris Fox 51National Oceanic and Atmospheric Administration, Narragansett, RI;2Fuss & O’Neill, Providence, RI; 3 U.S. Fish and Wildlife Service, N. Attleboro, MA;4KCI Technologies, Sparks, MD; 5 Wood Pawcatuck Watershed Association, Hope Valley, RI

Lower Shannock Falls Dam Removal, along with HorseshoeFalls Fishway and Kenyon Industries Dam RemovalARRA Award, June 2009ImpoundmentKenyon Industries DamDamHorseshoe Falls DamLower Shannock Falls Damand Impoundment

Pawcatuck RiverWatershedProjectSiteRhode IslandMap Source: WPWA

Fish Passage Goal:Unimpeded Passageby Target Species andDesign CriteriaTarget Species:‣Alewife (Alosa pseudoharengus)‣Blueback herring (A. aestivalis)‣American shad (A. sapidissima)‣Atlantic salmon (Salmo salar)‣American eel (Anguilla rostrata)‣Resident fish species (e.g., Brook trout)1,043-Acre Worden Pond85 mi 2 WatershedAlosid Run Period Design Flows:‣10% Non-Exceedance = 85 cfs‣50% Non-Exceedance = 175 cfs‣90% Non-Exceedance = 356 cfsWorden Pond OutletAlosid Run Period Minimum Design Depth:= 9 inches; Maximum Velocity = 7ft/sFish Flow, HEC-RAS, Hydraulic Analyses: KCI TechnologiesPawcatuck River

Lower Shannock Falls DamPre-RemovalLow FlowHigh FlowRun-of-the-river dam7-ft height (4-ft high structureon bedrock), 105-ft length500-Year Event(March 2010)

Site ConditionsHistoricSmoke Stack(Preserved)Knowles Mill Remains (Removed)Impoundment (13+ ft deep)Mills Remains in Downstream Riverbed

Dam Removed

Former Dam and Bedrock Ledge

Weir ConstructionJuly-August 2010Rock ExcavationPlans: Fuss & O’NeillPhotos: C. Fox

Weir 1Weir Constructionand ModificationsWeir 2Void Filling with SandWeir Notch Measurements

Boulder Placementfor Flow Pattern ModificationAugust 26, 2010Sand Bag Placement Testfor Backwatering EffectsPhotos: Fuss & O’Neill

Test Flow MeasurementsAugust 26, 2010Photos: Fuss & O’Neill

Weir 143 FeetWeir 2Weir 3As-built in boldDesign inParentheses(PreliminaryResults)Backwatering weirs at 90 cfs flow (11 November 2010)

90 cfs Flow at WeirsExpected Alosid Migration RouteUpstreamDownstream

Natural Grade DropsExposed withImpoundment Drawdown

Cost SummaryLower Shannock Falls Hybrid Dam Removal(Dam Removal with Nature-like Fishway Component)Feasibility Assessment = ~$42,300Design and Permitting = $187,260(Included SHPO coordination, public workshops, easements)Construction and Oversight = $588,910(Included removal/disposal of 105 cy contaminated sediments, wellreplacement)Post-Construction Monitoring = ~$25,000Total Project Costs = $843,470Cost/Foot-Rise for Construction = $82,000

Lessons LearnedOrganize project team that is well experienced in fishery biology,hydrology/ hydraulics, sediment transport, and water managementComplete nature-like fishways in “dry” conditions to achieve elevationsand other design features requisite for fish passage; test flows duringconstruction if possible to make flow modifications benefiting fishConduct routine post-removal monitoring of target fish presence/abundance and flow depth and velocity at dam removal/nature-likefishway sites to determine if passage goals are metRecognize that quantitative passage performanceevaluation may require 3-5+ years to concludewhether goals are metMonitor post-dam removal site conditions for 3+ years including upstreamriver channel and bank stability, and riparian wetland community metrics