FRANKLIN FALLS DAM

PEMIGEWASSET RIVER - Merrimack River Basin - Franklin, NH

DRAINAGE AREA : 1,000 sq.mi.

PERMANENT POOL: 307.0 Ft NGVD (Backwater)

DAM
Type: Rolled earth
Length: 1,740 Feet
Top Elev = 416.0 Ft NGVD

FLOOD CONTROL STORAGE
Capacity: 150,600 Acre. Feet
2.8 Inches of Runoff
Area at Crest: 2,800 Acres

CONTROL WORKS
Type: 2 Conduits
Size: 22' Horseshoe
Length: 542 Feet
Invert Elev = 300.0 Ft NGVD
Capacity (Full Pool): 41,000 cfs
Gates (Type): Broome
Number: 8 (4 ea. conduit)
Size (ea. conduit): 3 @ 7'-6" x 16'
1 @ 4'-6" x 10'
Channel Capacity = 18,000 cfs

SPILLWAY
Type: Chute Spillway/Ogee Weir
Length: 546 Feet
Elev = 389.0 Ft NGVD

SPILLWAY DESIGN FLOOD

• Original Design Criteria:
• Rainfall Excess = 13.3 inches
• Initial Pool Level = Full
• Flood Control Outlet Gates = Operable
• Peak Inflow = 210,000 cfs
• Peak Outflow = 205,000 cfs
• Max. Pool = 411.0 ft-NGVD
• Freeboard = 6.0 ft
• Current HMR 51 & 52 Criteria:
• Rainfall Excess = 15.3 inches
• Initial Pool Level = Full
• Flood Control Outlet Gates = Operable
• Peak Inflow = 338,000 cfs
• Peak Outflow = 327,000 cfs
• Max. Pool = 416.5 ft-NGVD
• Freeboard = 0.5 ft

RECREATIONAL FACILITIES: Profile Falls picnic area with picnic tables and grills, portable bathroom, trails and parking areas.

TOTAL COST: $7,947,200

PLACED IN OPERATION: October 1943

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