Mordecai Lincoln Dam & Hunters Pond, Scituate, MA

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

2. Vegetation Dam Hunter’s Pond Infilling Coarse Grained Sediment Deposit Fine Grained Sediment Deposit FLOW PROFILE 1690: First dam built on site 1969: Dam breached 1984-85: Current dam constructed 2013: Impoundment nearly full of sediment Submerged Vegetation Vegetation Dam Coarse Grained Sediment Deposit Fine Grained Sediment Deposit FLOW PROFILE

3. Hunter’s Pond Impoundment 12-05-2012 7-20-2010 02-15-2010 06-19-2013

4. 2013 GZADam 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 Spillway Aux. Weir - Culvert Culvert

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

6. Results • Relatively small mobile sediment quantityand 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 Figure: Sediment Sample Locations

7. Dam Removal & Restore Channel/Floodplain • 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. 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 • 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. Source: Bukaty Source: Bukaty Source: Southerland

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

11. EXTRAS

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

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

14. 2013 GZADam Inspection & Repair Summary • Dam Hazard Classification: SIGNIFICANT (class II) • Dam Condition: POOR • Proposed Remedial Actions for Repair: • Clear trees and woody vegetation from embankment and backfill with compacted sand and gravel. • Repair and re-grade upstream slope and install riprap slope protection. • Install a graded filter blanket to control seepage at downstream toe of dam. • Repair and re-grade downstream slope using dumped riprap or rockfill. • Rehabilitate outlet works (repair or replace conduit and slide gate). • 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 2005 1990 1970 1972 2006 2008 2011 2004

17. Dam Construction Wetland formation 0 100 60 40 80 20 years before present Infilling of a Man-made Impoundment Source: TNC open water emergent vegetation floating-leaf vegetation floodplain vegetation

18. Hunter’s Pond Impoundment IMPOUNDED SEDIMENT DELTA POND 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

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