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Mordecai Lincoln Dam & Hunters Pond, Scituate, MA Bound Brook.

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Presentation on theme: "Mordecai Lincoln Dam & Hunters Pond, Scituate, MA Bound Brook."— Presentation transcript:

1 Mordecai Lincoln Dam & Hunters Pond, Scituate, MA Bound Brook

2 Hunter’s Pond Infilling Coarse Grained Sediment Deposit Fine Grained Sediment Deposit Vegetation Dam FLOW Submerged Vegetation PROFILE Coarse Grained Sediment Deposit Fine Grained Sediment Deposit Vegetation Dam FLOW PROFILE 1690: First dam built on site 1969: Dam breached : Current dam constructed 2013: Impoundment nearly full of sediment

3 Hunter’s Pond Impoundment

4 2013 GZA Dam Inspection & Repair Summary Dam Hazard Classification: SIGNIFICANT (class II) Dam Condition: POOR GZA’s opinion of probable cost, for all recommended work: $450,000 - $750,000. Dam & Bridge Bridge Culvert Aux. Weir - Culvert Spillway

5 2013 Princeton Hydro Dam Removal Feasibility – Scope of Work 1.Preliminary Evaluation of Ex. Information & Site Conditions 2.Delineation of Regulated Resources 3.Survey and Mapping 4.Preliminary Hydrology & Hydraulics (with gage) 5.Sediment Mapping, Characteristics, Analysis 6.Historic Review 7.Public Meetings 8.Preliminary Design Plans for Dam Removal

6 Results Figur e: Sediment Sample Locations Relatively small mobile sediment quantity and general lack of contamination. Mordecai Lincoln Road begins overtopping in flows in excess of the 100-year event Dam removal has little effect on upstream water levels during the 100- and 500-year storm events, with the maximum effects (decrease in water level) during the lowest flows Flow must be maintained through both outlets so as not to increase water levels during the 100-ye regulatory event. It is recommended that flow not be increased through the auxiliary outlet during storm events Dam removal will not change normal tidal influence on the former impoundment, which currently extends to base of both outlets

7 Proposed Restoration Actions: for Removal: Full demolition and removal of dam’s spillway, concrete apron, & fishway Slip-lining culvert under Mill building & reconfiguration of the upstream inlet Re-creation of approximately 700 linear feet of bifurcated channel to follow the legacy flow paths ; Stabilization & conversion of impoundment to ~2 ac of naturalized vegetated floodplain. Dam Removal & Restore Channel/Floodplain PH’s opinion of probable cost = $263,000

8 Cost Comparison Summary Dam Repair Construction Estimate $450,000 - $750,000 (with permitting & engineering, without construction oversight) Preliminary Dam Repair Construction Estimate $263,000 (with permitting & engineering, without construction oversight) Possible Additional Costs: Additional pipe under building???? Replacement of the bridge???? Sediment management $50,000 - $100,000 Construction Oversight by Engineer $25,000 - $35,000

9 Additional Benefits of Dam Removal Source: Bukaty Source: Southerland Eliminates a large part of O&M (dam, road, culvert, etc.) Exceptional benefit to river herring and other fish & wildlife Avenue for historical preservation Jives with bike path and other recreational goals NUMEROUS opportunities for funding assistance compared to other options.

10 Next Steps 1.Town approval to support project (2013) 2.Apply for NFWF grant opportunity (January 2014) 3.Determine project role of Moredecai Lincoln barn (2014) 4.Engage consultant for engineering design & permitting ( ) 5.Engage next level review of historical resources (2014) 6.Dam Removal bid solicitation (2015) 7.Dam Removal (2015) 8.Ecological Monitoring (2015…)

11 EXTRAS

12 Example of Dam Removal - Rakes Pond Dam Removal, PA 2011 – Rakes Pond 2012 – Post Dam Removal

13 1998 – Millport Dam Impoundment 1998 – Impoundment drawdown 1999 – Impoundment 1 growing season later 2008 – Impoundment 10 yrs later Example of Dam Removal - Millport Dam Removal, PA

14 2013 GZA Dam Inspection & Repair Summary Dam Hazard Classification: SIGNIFICANT (class II) Dam Condition: POOR Proposed Remedial Actions for Repair: 1.Clear trees and woody vegetation from embankment and backfill with compacted sand and gravel. 2.Repair and re-grade upstream slope and install riprap slope protection. 3.Install a graded filter blanket to control seepage at downstream toe of dam. 4.Repair and re-grade downstream slope using dumped riprap or rockfill. 5.Rehabilitate outlet works (repair or replace conduit and slide gate). 6.Repair concrete defects at spillway. GZA’s opinion of probable cost, for all recommended and potential work, was estimated to be $450,000 - $750,000.

15 Mordecai Lincoln Dam & Hunters Pond Bound Brook

16 Example of a Mill Pond Infilling - Heminway Pond Transition From 1970 to 2011 Watertown, CT

17 open water floating-leaf vegetation emergent vegetation floodplain vegetation Dam Construction Wetland formation years before present Source: TNC Infilling of a Man-made Impoundment

18 Hunter’s Pond Impoundment 4/17/2008 Pre growing season aerial of pond with impounded sediment delta submerged 6/18/2010 summer aerial of impoundment with vegetated impounded sediment delta IMPOUNDED SEDIMENT DELTA POND

19 Community Concerns Expressed at 1 ST Neighborhood Discussion Existing Wildlife Dam Alternatives & Funding Aesthetics (i.e. mudflats) Dam Safety Road & Bridge Safety Flooding Sediment Infilling and Dredging


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