Even in Texas, winter weather can be cold enough to prevent or delay exterior painting projects. But last year, the residents of Flower Mound, Texas (pop. 45,000), a quiet but fast-growing community on the northern edge of the Dallas/Fort Worth metroplex in Denton County, Texas, used a new, low-temperature epoxy amine coating to begin a $450,000 water tank-painting project in mid-January.
The head start enabled the project to be completed in time for the tank to be returned to service just when record summer heat was driving Dallas-area water consumption to an all-time high.
An internal inspection of the 167-foot-tall, one million-gallon elevated water tank in 1995 revealed significant blistering below the water line and rust bleed and corrosion above the waterline.
Rust bleed in water tanks occurs when condensation collects above the waterline in crevices and on structural steel members. Over time, the coating system in these areas begins to crack and peel. If corrective action is not taken, the condition can progress to a more serious problem such as steel corrosion, which may require structural repair or replacement.
The 75-foot diameter tank, which holds treated surface water provided by the city of Dallas, had not been re-painted since its construction in 1974. A cathodic protection system had helped mitigate corrosion and extend the service life of the existing coating system, but a complete repaint of the potable water tank?s interior and exterior was needed. The town?s officials contracted with the national engineering firm of Kimley-Horn and Associates to write the coating specifications in preparation for bidding.
The specifications were written according to AWWA system #2 guidelines, said Michael Wellbaum, EIT, Kimley-Horn?s Fort Worth office, with input from Sherwin-Williams Dallas-based Specification Specialist Earl Baker. But before the project could begin, a new elevated tank had to be constructed to meet the town?s interim water needs.
?Flower Mound is growing at an extremely fast rate,? Wellbaum said. ?The construction of a new tank served two purposes ? to meet the increasing demand for water in the long term, and to serve the community temporarily while the older tank was out of service for repainting.?
The new, two million gallon composite tank with a concrete pedestal and steel bowl was built to improve water availability and distribution. The $1.8 million water tank took about a year to build, Wellbaum said.
The contract for surface preparation and painting of the existing tank was awarded to TMI Coatings, a contractor specializing in the application of protective coatings and linings for industry, including the removal of lead-based paints from tanks, structural steel, silos and other surfaces in accordance with all OSHA and local EPA requirements. More than half of the contractor?s work involves elevated water tanks, according to Bob Cox, project manager.
?We bid the job pretty aggressively to get winter work,? Cox said. "After reviewing the specifications, I did some cost comparisons and found we could work in cold weather and save significant dollars in materials using an epoxy coating designed specifically for low temperature application to the tank interior."
The coating he recommended was Sherwin-Williams new Epoxide" II Low Temperature Tank Lining.
The NSF-approved coating is formulated for application at temperatures down to 35?F, and provides a corrosion resistant barrier on the interiors of potable, fresh an saltwater storage tanks. Use of the coating system would enable TMI to begin painting in January, when temperatures in the region dip into the 20s at night but typically are warm during the day, Cox said.
Cox had some work to do, though, to persuade Kimley-Horn to allow the substitution.
?Basically, we had to prove the coating?s worthiness,? he said, ?since it is a relatively new product and they were not familiar with it.?
Sherman-Williams Midwest-based Corrosion Specification Specialist Lee Dornbush and Sales Representative Joe Cesarek worked with TMI. Along with Baker, they were instrumental in providing the test results and data necessary to gain the engineering firm?s and the town?s confidence.
?We?re willing to allow substitutions,? Wellbaum said, ?as long as the coating meets the intent of the specifications and our client?s needs.?
Along with the meeting the toxicological and extraction test requirements of NSF Standard 61, the low temperature epoxy coating complies with EPA standards for VOC emissions. Accelerated immersion and cathodic disbondment tests reveal that the coating forms a strong bond to numerous substrates, including steel and concrete, and is compatible with both impressed current and galvanic cathodic protection systems. The coating also conforms to AWWA D102-97 for interior catalyzed epoxy coating systems and is suitable for USDA inspected facilities.
?We are able to make a strong case for the coating system,? Cox said. ?Sometimes the contractor is more informed about what new products are available because we specialize in this area.?
But, price alone is not a sufficient reason to recommend a substitute coating, Cox noted. ?In addition to coating quality, we look at the service and dependability of the supplier. These are most important, and price is next,? he said.
TMI started the project in mid-January and, using a crew of five to six painters, completed the job in early April. The tank?s interior was prepared to SSPC-SP 10 (near white blast) while the exterior was prepared to SSPC-SP 6 (commercial blast). Containment was provided in accordance with regulations for the state of Texas, Cox said. The existing coating was tested for lead content, but lead abatement procedures were not required.
Two coats of the low temperature epoxy were applied to the tank?s interior at 4-6 mils DFT. ?The coating?s low temp properties enabled us to work virtually whenever we wanted to,? Cox said, ?and we had no problem getting the film build and the coverage we needed.?
For the tank exterior, two coats of Sherwin-Williams Recoatable Epoxy Primer were applied at 4-6 mils DFT. The topcoat was Sherwin-Williams PolyLon 1900, a heavy duty, high performance two component polyester-aliphatic urethane coating applied at 2-3 mils DFT. The coating provides an attractive finish and excellent long-term durability even in aggressive environments. Inspection services, which included pinhole and holiday testing of the painted tank, were provided by SG Pinney of Lancaster, Texas.
According to Cox, a pleasant surprise was easy cleanup of the Recoatable Epoxy Primer. ?It acted almost like a dryfall, with overspray wiping clean from surfaces below.? Containment was especially important because the tank was located in a residential area adjacent to a high school. ?We have a lot of experience working in high traffic areas with close proximity to neighbors, so this was not a problem for us,? Cox said.
TMI offers customers a ?confidence guarantee,? and detailed proposals that list each step required to complete the project ? including an explanation of the work to be done, proposed materials, cost to perform the work, time frame in which the work will be done, and a warranty. Foreman Fred Arnold was responsible for the project from start to finish, overseeing all prep work, installation and cleanup on the job.
?Job leaders work on an incentive system and are rewarded for positive feedback from the customer,? Cox said.
Only one surprise altered job plans from those proposed by TMI. When the local high school football team, the Marcus Marauders, won the state championship, community pride induced the town to honor the achievement with a handsome notation emblazoned on the water tank.
?A committee of community planners submitted suggestions, and a new logo was designed by Kimley-Horn. It really looks great,? Cox said.
The residents of Flower Mound, whose water tank was put back into service at a critical time, were not the only ones grateful that work has proceeded through the winter. Due to the use of the low temperature epoxy coating, the work could be done before the hottest summer on record, when intense heat scorched lawns and crops.
Fifty-one times ? more than seven weeks in all ? the afternoon high in the metroplex area reached or exceeded 100?F that year. Sundown brought little relief, with overnight temperatures dropping no lower than 80 degrees F a record 38 times. It was the second-driest April-August period in Texas history, with less than six inches of rain. Only the Dust Bowl year of 1934 was drier.
?We can?t take credit for knowing that the heat wave was coming, but in retrospect, we were glad we made it our goal to complete the job as soon as possible,? Cox said.
