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Location

Black Mountain, NC

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P&J Role

Prime Contractor

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Completion Date

November 2020


Project Description

The North Fork Spillway and Embankment Improvements Project is designed to update the North Fork Reservoir dam, which was originally built in 1955. Advances in technology since its construction allowed the City of Asheville to determine ways to make the dam more resilient in the face of possible but unlikely storm events. The dam was raised by 4’, with added earth buttressing to reinforce seismic stability, and the principal spillway was improved while a new auxiliary spillway was constructed.

Project Highlights

350,000

CY Earth and Rock Excavated

15,000

CY Structural Concrete

200’ by 600’

Spillway Constructed

50

AC Heavily Timbered Land Cleared & Grubbed

~4,500

SF Foundation Preparation

600

LF Grout Curtain Drilled & Grouted

2.5M

LBs Concrete Reinforcing Steel Installed

15,000

TN Blanket & Chimney Drains

20,000

TN Riprap Placed

250' by 25'

MSE Wall Constructed at Main Dam

2

Bridges Installed

P&J began these improvements in November 2017. The main scope of work was the construction of the new auxiliary spillway, which is approximately 200’ wide and 600’ in length. The control section of the spillway was a Hydroplus design called Fusegates. Earth and rock had to first be excavated to get to the subgrade of the spillway, and material excavated from the spillway was used to buttress the two existing earthen dams from a 2:1 slope to a 2.5:1 slope. A new seepage collection system was also installed prior to the placement of the buttress material.

Due to the placement of the buttress material, the conduit that supplies raw water to the water treatment plant had to be extended. The extension was achieved by casting in place a structural concrete vault that will house a new 36” ductile iron pipe. To not interrupt plant operations, a temporary pumping system was installed during the conduit extension. Modifications were made to the existing intake tower, and the principal spillway was rehabilitated, including the installation of new Obermeyer spillway gates.