Award of Excellence: Industrial Category
Hyperbolic Cooling Tower Column and Lintel Beam Cathodic Protection
Submitted by Existing Structures Engineering
Jacksonville Electric Authority—St. Johns River Power Plant
Existing Structures Engineering
Cape Canaveral, Florida
Structural Preservations Systems, Inc.
Deer Park, Texas
Jarden Zinc Products
Hyperbolic cooling tower No. 2 at St. John’s River Power Park in Jacksonville, FL, stands 450 ft (137 m) tall and 360 ft (110 m) in diameter. When deterioration was noticed, a condition evaluation performed found the lintel beam and columns in poor condition with chloride testing results exceeding the recommended standard chloride threshold value. Several factors contributed to the deterioration—the brackish water being used in the tower and the airflow from the Atlantic Ocean and the river traveling throughout the cooling tower were producing high oxygen and chloride levels.
Over the years, several attempts at repair proved ineffective, so in addition to repairs, a cathodic protection system consisting of encapsulating zinc mesh anodes within a stay-in-place fiberglass form filled with cementitious grout was recommended. The scope work included installing 120 lintel beam jackets and 240 column jackets for a total of 34,000 square ft (3160 square meters) of jacketing. Prior to installation, delaminated concrete was removed, concrete surfaces profiled to a minimum ICRI CSP 3, and the corroded reinforcing bars cleaned.
Work was scheduled for a 5-week period during an outage; however, an unforeseen delay occurred to accommodate a chemical cleaning of the internal tower “fill” or “packing” media. In response, the contractor, with plant management approval, decided on a 24/7 schedule. Adding to scheduling challenges were three other contractors working on the tower during the same period, making the daily planning meeting held with the owner and other contractors invaluable. Coupled with the skill of the crew, putting in more than 16,000 hours, the contractor addressed these challenges and met the client’s aggressive schedule.