Catawba Dam ESSI Phase I & II
Earthen embankment construction for dam enhancement
Quick Facts
Location
Nebo, North Carolina
Role
Prime Contractor
Completion Date
February 2011
Project Overview
The Duke Energy Carolinas Bridgewater Hydroelectric Project, located near Nebo, North Carolina, comprises the Paddy Creek Dam, Catawba Dam, and Linville Dam, collectively forming Lake James. Based upon a nationwide effort initiated by the Federal Energy Regulatory Commission (FERC) to improve the performance of existing dams during large earthquake events, Duke Energy Carolinas was required to implement embankment seismic stability improvements (ESSI) to comply with FERC requirements. The engineering designs approved by Duke Energy Carolinas for the ESSI projects included the construction of large earth and/or concrete structures along the downstream slopes of the dams to mitigate potential damage in the event of a future earthquake.
Project Highlights
120K+
CY of Material Excavated
8,400
Tons of Aggregate Base Placed
19,800
SY of Flexterra Placed
223K
CY of Site Development Excavation
365K+
CY of Foundation Excavation and Spillway Channel Material
77,750
CY of Fine And Coarse Blanket and Chimney Filter Drain Material
148K+
CY of Foundation Backfill Placed
700K
CY of Berm Embankment Placed
150K
CY of Material Relocated For Haul Roads
71,126
Tons of Aggregate For RCC Imported
48,500
CY of RCC Buttress and Wing Walls
2,385
CY of Spillway Face Demolished
15,225
CY Cast-In-Place Concrete
147K+
Man-Hours With 0 Lost-Time Accidents In Combined Phases
Phillips Contribution
Phillips was awarded the contract for the construction of the Catawba Dam ESSI Phase I & Phase II Projects. The Phase I Project involved preparation for the actual modification of the dam and spillway structure. Specific activities performed by Phillips included grading and construction of a temporary entrance from State Route 126; clearing, grubbing, and stripping of 10 acres around the project site; installation of erosion and sediment control measures; construction of two sediment basin structures; construction of support facility pads; excavation; placement of 8,400 tons of aggregate base and FlexTerra; and temporary seeding of three acres.
The Phase II Project was 150 acres in size and involved the construction of a new earthen embankment downstream from the original dam. Specific activities performed by Phillips included clearing and grubbing of 116 acres around the project site; construction of haul roads and retention ponds; installation of erosion and sediment control measures; site development excavation; foundation dewatering including design, installation, operation/maintenance, modifications, and systems removal; foundation excavation and spillway channel material; installation of fine and coarse blanket filter drain material; placement of foundation backfill and berm embankment; installation of an inclined chimney filter drain and seepage collection channel; and final site restoration, including seeding and mulching of 150 acres, degrading of haul roads which required the relocation of material, and seedling reforestation of 135 acres. Additional activities performed by Phillips included import of aggregate for Roller Compacted Concrete (RCC) and construction of RCC buttress and wing walls, demolition of spillway face and resurfacing of the demolished spillway face with concrete, demolition of the right bulkhead and wing wall, and conversion of 68’ of the right bulkhead to a new ogee crest spillway.
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