Caldwell Tanks, Inc. in Louisville, Ky. was awarded the 2021 STI/SPFA Elevated Tank of the Year for the Lincoln District Elevated Water Storage Tank.

We had an opportunity to speak about the project further with Kevin Gallagher, P.E., Vice President of Caldwell Tanks, Inc.

YouTube video

Caldwell Tanks completed a 1,000,000-gallon pedesphere style tank for Illinois American Water.

A pedesphere is a slender column that supports a large spherical or spheroidal elevated water storage tank, commonly referred to as a golf ball on a tee.

The 1,000,000-gallon tank you see here with the city of Lincoln, Ill. and the profile of Abraham Lincoln, is the largest elevated pedesphere style tank designed, constructed, and built in the last several years. 1,000,000-gallon is about the largest capacity that pedesphere style tanks are commonly built.

The tank was built to accommodate a new water treatment plant being built to supply a growing area around Lincoln, Ill. In addition to being one of the largest pedespheres built in recent years, it also has the intricate logo of the bust of Abraham Lincoln that was featured on a calendar in 2022 as well.

The capacity of the tank is 1,000,000-gallons. 370 tons of steel, steel plate primarily, were required to build this project. The steel is in thicknesses up to two inches at its maximum thickness, so there was a significant effort in design, fabrication, construction, and welding to complete this very high profile and challenging project.

At the top of the pedestal, the tank transitions into the tank container above and we call that double curved the hard way. A typical double curved piece that’s up in the ball of the tank will be curved in both the vertical and horizontal direction, but they’ll be put together in pieces to form an entire spherical or spheroidal section. A particularly challenging part of the tank is that transition from pedestal to tank where it’s double curved the hard way.  Those transition dyes are designed and fabricated, typically by the manufacturers. A very limited number of manufacturers have experience in this style of tank, particularly at this capacity.

The monolithic footing is poured just prior to the ring wall being poured. The rebar projects from the cutting into the ring wall that supports the tank.

Weather can be a challenging item to manage on storage tank projects as well.

The tank takes shape. Everything has been welded together, and the roof plates are set.

The access tube is essentially used as a crane with a center mast and a boom coming off of it, which lifted large subassemblies which are constructed on the ground and then lifted into place, set into place with key plates and other aligning mechanisms, and then the welding is completed. What wasn’t done on the ground was done in the air.

The tank is 142 feet, one inch overall in height. The height of the column, just the center pedestal, is 91 feet, and the diameter of the tank is 74 feet at its equator.

In this project, there happened to be a few subassemblies where multiple pieces were put together and then those few assemblies were put together on site.

Ladders and manholes allow for dry access through the pedestal, through the base ground, through the pedestal, through the access tube, all the way up to the roof of the tank.

Illinois American Water is the owner of this water storage tank and celebrated the city of Lincoln’s heritage with the bust of Abraham Lincoln.

We would like to thank some of the many, many folks who worked on this critically important project. In addition to all of the folks at American Water, we would like to recognize Farnsworth Group, who served as American Water’s consulting engineer for the project; all the folks at Caldwell, who worked so hard on the design, the fabrication, and the construction of the elevated water storage tank; and many of the key subcontractors that were part of the Caldwell team, including W.F. Johnston Construction, who did the foundation, the site work, and the site piping; Newman Company Contractors who performed the field coatings application; Windemuller who did the electrical for the project; and Corrpro on the cathodic protection.

Lastly, we’d like to thank the folks and the customers in the city of Lincoln, Ill., and the folks in the area who are served by Illinois American Water. It was an honor to serve on this project and to help deliver key infrastructure that will likely be part of the city and American Water system for 100 years or more going forward into the future.

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Published Date

January 9, 2023

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