City of Norton – Upper Norton Dam and Spillway Improvements

City of Norton – Upper Norton Dam and Spillway Improvements

The City of Norton owns and operates two impoundments for water supply purposes, one situated above the other on Benges Branch, to the south and above the downtown area. The upper dam was completed in 1959 and modified in 1997. The reservoir is a 73 foot deep earthen structure with a maximum capacity of 202 acre-feet. Regulations require that the reservoir be capable of safely passing the Probable Maximum Flood (PMF). The City of Norton partnered with T&L to plan, design, permit and construct improvements to the Upper Norton Dam and spillway.

A summary of T&L’s services includes:

• Preparation of a Preliminary Engineering Report (PER) to evaluate alternative solutions for improvements to the existing impoundment;
• Evaluation of the existing spillway capacity;

The PER recommended that an auxiliary spillway be constructed to increase capacity for passage of the PMF. To retain the same pool elevation and provide an adequate channel for the spillway, a labyrinth spillway (shaped like a “zigzag”) was utilized due to space considerations.

Major design and construction elements included:

• A 50-foot wide reinforced concrete auxiliary spillway chute with energy dissipation at the outlet;
• Structural concrete chute walls to contain spillway flows; and
• A labyrinth weir at the inlet of the spillway.

This project was completed in 2013, with a construction cost of approximately $2,232,000.

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