Blakely Mountain Dam Lake Ouachita - Seepage Monitoring System.

  

Dam Seepage Monitoring System Installed to monitor Lake Ouachita's Blakely Mountain Dam.

In May 2006, a risk assessment screening was performed for Blakely Mountain Dam as part of the Corps-wide dam safety initiative.

Earthen Dam Safety Action Classification (DSAC) have 5 Ratings - I, II, III, IV, V . -  I is Urgent And Compelling and V is normal.

Blakely Mountain Dam was classified as DSAC II  largely due to recently discovered anomalies in the under-drain system which occurred during construction of the dam.

DSAC Class II - (Urgent) – Dams where failure could begin during normal operations or be initiated as the consequence of an event. The likelihood of failure from one of these occurrences, prior to remediation, is too high to assure public safety; or the combination of life or economic consequences with probability of failure is very high.

The Corps of Engineers installed a monitoring system to keep an eye on seepage at Blakely Mountain Dam. The monitoring system is part of the analysis and response to the 2005 inspection within the overall dam safety program.

 In the wake of the regular 2005 inspection, engineers discovered that a layer of filter material had been installed incorrectly when the dam was originally built in 1953. Filter material is designed to aid normal seepage under the dam. Without it, the seepage must be monitored more closely over time.
All dams are designed to allow for controlled seepage. There are multiple layers of material in the core of the dam that allow a small amount of water to flow through the dam without moving any materials. If material moves, over the long term; it would weaken the structure of the Dam.

“The Dam has performed well over its 50 years of service and we believe at this time that it is functioning normally, however; we need to watch the seepage issue more closely as the Dam continues to age”, said Bob Fitzgerald, Dam Safety Officer for the Vicksburg District.

In order to install the monitoring system the Corps worked with Entergy to lower the level of Lake Hamilton during the normal winter drawdown of 2008 - 2009 the draw down will required the maximum allowed drop of 9 feet in Lake Hamilton.  Nine foot drawdown had occurred three times since 1997 to help control aquatic weed growth.

This expose the piping system under Blakely Mountain Dam that allows seepage so the water can be channeled and the measuring system installed.
Construction should begin in November and be completed by June of next year. The draw down of Lake Hamilton should only last until March.
For more information
contact
Frank Worley, Deputy, Public Affairs, (601) 631- 5053
 



Information courtesy of
U.S. Army Corps of Engineers

c-2017

Case Study: Blakely Mountain Dam

Blakely Dam Age and Safety

Seepage Monitoring System

Blakely Mountain Dam Powerhouse

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