The document summarizes plans for the removal of Bunker Pond Dam and restoration of the stream. It provides background on the dam's construction in 1865 and deterioration over time. Removal is proposed rather than rehabilitation due to flooding risks and lack of funding for repairs. Removal is estimated to cost $180,000 and would improve habitat and allow fish passage on the Lamprey River. Sediment testing was conducted and a deconstruction plan created involving draining, concrete removal, and bank stabilization. Stream restoration designs include rock structures and plantings to reduce erosion.
15. Background Constructed in 1865 The dam is currently owned and operated by the NHDES since 1959 It is considered a low hazard structure by the NHDES Prone to flooding NHDES Upstream of Bunker Pond Dam 4
16. Background 15’ high 76.8 sq. mi. of drainage area Originally installed for hydropower for local mills 5
17. History 1746 - Joshua Folsom opens mill on the east side of the Lamprey. The pond is named after David Bunker, who owned a woolen mill. Historical assessment is an important part of permitting in order to identify the significance of potential historical resources. Permits can be deferred if the site contains valuable historical resources. Courtesy of Madelyn Williamson – Epping Historical Society 6
18. Original Scope Rehabilitation Sidewall cracking Sidewall expansion Seepage Groundwater flow Bank erosion Flood control West side of Bunker Pond Dam 7
19. Removal Dam no longer serves a purpose Contributes to upstream flooding More economic than rehabilitation Natural resources Marine life Plant life Water quality Downstream of Bunker Pond Dam 8
20. Funding Repair Annual Cost to Operate: $3,800/yr. Average Dam Restoration Cost: $800,000 Little to no Funding Provided for Repair Removal Estimated Removal Cost: $180,000 More Funding Provided Because of Effect on Ecology 9
21. Natural Resources Lamprey River as the most significant coastal river for anadromous fish. Lamprey is a National Wild & Scenic River NH Fish and Game Commission 10
39. Bridge Post-Removal Bunker Pond Dam 2-GEL Plan: Plan 04 4/18/2010 Route 27 Bridge .1 .045 .1 155 Legend 150 EG 100 yr WS 100 yr 145 Elevation (ft) Crit 100 yr 140 Ground 135 Bank Sta 130 125 0 200 400 600 800 1000 1200 1400 Station (ft) 21
40. Proposed Stream Restoration Geomorphic Stream Rock Structures to reduce bank erosion Planting of wild flowers and slope seeding Monitoring will be required in the months post removal The Cross-Vane, W-Weir, and K-Hook Vane by David Rosgen 22
41. Proposed Stream Restoration The Cross-Vane is a grade control structure that decreases near-bank shear stress, velocity and stream power. Structures locations will be determined post removal Possible locations Before Route 27 Bridge channel River bends within Bunker Pond 23
42. Proposed Stream Restoration Approximately 50 cubic yards of rip rap removed from the dam site Can be used to create cross- vanes 24
44. Deconstruction Plan Dewatering Draining via flood gate Bedrock at approx. 4’ Portadam will be put in place Any water remaining will be pumped out From Portadam brochure 26
45. Deconstruction Plan Removal of Concrete Removal will begin at the east abutment and progress to the west abutment Approx. 270 tons of concrete Concrete will be recycled for $35/ton at ERRCO in Epping, NH 27
46. Deconstruction Plan Post-Removal Rip-rap removal Seeding and jute mats on banks Portadam will be removed and reinstalled to divert water back to original stream flow http://www.gregsindigenouslandscapes.com.au/images/JuteMat.JPG 28
Located in Epping NH where the lamprey river crosses under route 27
April 16 – 18, 2007 - Lamprey River nr. Newmarket – 8450 cfs > 100 year storm event. May 14 – 17, 2006 - Lamprey River nr. Newmarket – 9100 cfs > 100 year storm event.
Q100 at dam – 4930 cfsDischarge capacity at dam = 4820 cfs 1’ frbrd, 5936 cfs top of damIncluded in the 76.8 is at least 30 registered dams
NH Fish and Game CommissionWiswall Dam in Durham is having a fish passage put inNational wild and scenic rivers are not usually damned
Current accessible anadromous fish habitat in coastal rivers vs. potential habitat in the Lamprey River (in miles).