AWARD OF MERIT: Water Structures Category

REPAIRS TO THE MORRIS SHEPPARD DAM AND POWERHOUSE AT POSSUM KINGDOMW LAKE

Graford, Texas

Submitted by Jaster-Quintanilla, Dallas, LLP

The Morris Sheppard Dam, constructed between 1938 and 1941, impounds the Possum Kingdom Lake, highly regarded as one of the most beautiful lakes in Texas. The cast-in-place concrete powerhouse sits at the base of the 190 ft (58 m) tall, 2015 ft (614 m) long dam structure.

Maintenance personnel observed that cracks and spalls had developed in the heavily reinforced exterior walls of the powerhouse. Further investigation of the existing conditions revealed that extensive corrosion of the embedded reinforcing steel was causing the 4 to 6 in. (10 to 15 cm) thick concrete cover to shear off at the exterior face of the reinforcement.

Other areas of concern included:
• Delaminated concrete on the sloped top and vertical face of large encasement blocks that anchored the 12 ft (3.7 m) diameter Penstock pipes that feed water from the lake to the generators’ turbine wheels; and
• Spalling concrete beneath several of the large concrete struts located between the massive buttresses that support the dam’s concrete slab.

Sixty-five years worth of exposure to the elements had taken its toll on the Morris Sheppard Dam and Powerhouse. Nevertheless, the Brazos River Authority authorized funds for the necessary repairs in the 2006 budget to properly maintain this investment.

Budgeted at $1.7 million, the repairs to the Morris Sheppard Dam and Power­house were completed in August 2007 at a cost of less than $1.1 million, only 11.6% over the Contractor’s original bid amount of $985,000.

Owner
Brazos River Authority
Waco, Texas

Project Engineer/
Designer
Jaster-Quintanilla, Dallas, LLP
Dallas, Texas

Repair Contractor
Restek, Inc.
Buda, Texas

Materials Supplier/
Manufacturer
Sika Corporation
Lyndhurst, New Jersey