Dow Chemical’s Oyster Creek Gulfstream plant in Freeport, Texas, is the largest propylene production facility built specifically for that purpose. The materials from this facility are used for food packaging, personal care products, medications and clothing. Dow recognized a means for cost savings by processing shale gas rather than purchasing ethylene and propylene from outside sources. However, there was a catch: the science behind processing this gas required a lot of water to keep machinery cool.
Following a similar strategy in finding and processing from local sources, Dow chose to pump water from the nearby Brazos River. “The ultra clean water allows the cooling system to be more effective and reduce the amount of downtime for the cleaning process each maintenance cycle. Reduction of maintenance downtime reduces operations shutdown costs,” said John Haddox, sales manager for Texas Aquastore. “The water from the Brazos River is treated with an ultramicron filtration system. The filtration system takes out all heavy particles and produces ultra clean water.”
With an in-house treatment option already determined, storing the vast quantity of water became the next course of action. Dow worked with Texas Aquastore to develop a storage solution of three separate tanks each able to hold 1.3 million gal of water. These tanks are glass-fused-to-steel storage tanks from CST Industries measuring 117 ft in diameter to 19 ft in height, but despite their size, construction was quick and cost-effective.
“The Aquastore method of building from the ground up [made the tanks easy to construct]. Had it not been for that single advantage, these tanks would have been much more difficult to construct,” said Jonathan Coulston, project manager for Texas Aquastore. “From first foundation pour to last sheet on the tie-in ring took roughly 12 weeks per tank.”
CST Industries developed these glass-fused-to-steel tanks to satisfy the demand for long-term storage with minimal maintenance and high durability. They are virtually seamless because they do not require the same system of bolts to hold the tank together, which leads to fewer leaks.
While construction of the tanks themselves was speedy, the project did hit some snags along the way, most notably in terms of scheduling. Areas of the project outside the original scope were behind schedule.
“Once we mobilized the job site, we had to change the order in which we had planned on building the tanks to facilitate other contractors being able to maintain their current construction paths,” Coulston said, noting mother nature also reared her head. “Weather was its own monster. Working so close to the coast, it rained on days with 0% chance of precipitation. Wind was a regularly reoccuring problem, as well. When the wind reaches a certain speed, it becomes difficult to control the dome sheets and/or tank panels, so you find something else to do or stand down until it passes.”
These site conditions plagued workers throughout the entire project. And tight quarters made construction even more complicated—only around 2 to 4 ft of working space was available around the sides of the tanks. Aquastore normally requires 10 ft to complete its work. Contractors had to halt construction to move equipment and material for other contractors working on the project.
Despite those complications, the tanks stood tall in the end and met CSE compliance standards due to the site’s use of natural gas. There was a full-time “Hole Watch” and “Alternate Hole Watch.”
“We also used a 4-gas meter in the tank constantly monitoring the atmosphere, and each person in the tank had a personal gas monitor on them at all times,” Coulston said. “Additionally, we used a pair of 24 in. coppus blowers—one blowing out through the roof hatch; the other blowing in through the manway to maintain positive air pressure and move the required amount of air through the space each hour.”
Since installation, the tanks have performed well and the clarified river water from the Brazos River has kept Dow machinery cool during its manufacturing processes.