Click here to enlarge imageEach of the three CET suppliers own and maintain their own equipment to construct the concrete pedestal and steel tanks. Though each company has constructed dozens of CETs and have been doing so for over 10 years, each company uses a slightly different form system for the pedestal construction; form material varies (steel, wood or composite) and the form height varies (4', 6' or more).
The specification should specify that form panels consist of curved, prefabricated segments designed for full height plastic concrete pressure and provide a uniform pattern of vertical and horizontal rustications for architectural relief. The ACI Standards ensure proper form construction and concrete placement for whatever form height a contractor uses.
The project specification should require that contractors own and maintain their own forming equipment in order to ensure quality construction. The intent of the project specifications should focus on final product and quality requirements and allow the contractors to use their own proven construction techniques.
Qualifications, Experience
Owners and engineers should consider the in-house technical capabilities of all potential suppliers. Contractors should be required to have Professional Engineers with CET design experience on-staff that are licensed in the state where a project is being constructed. Additionally, reasonable experience requirements should be stated in all specifications, being careful not to eliminate qualified bidders.
Most CETs constructed today are 500,000 gallons or larger and all three contractors mentioned above have completed tanks ranging from this size to 2.5 million gallons or more. The specification should be written to require experience constructing tanks of similar capacity to that which is being specified and not exact capacity. This affords the purchaser the flexibility to fairly evaluate the qualifications and experience of the contractors equally, without penalizing them for completing slightly larger or smaller CETs.
To summarize, there is much confusion and misdirection in the CET marketplace as contractors dictate project specifications because there is no standard. Until the AWWA Standards Committee 170 releases the standard for the design and construction of composite elevated tanks, owners and engineers assume the responsibility of establishing project specifications for a CET.
It is in the best interest of engineers, owners and ratepayers to allow qualified and experienced contractors to bid these projects without limiting contractor’s proven methods of construction. Project specifications should allow the flexibility for each contractor to construct a quality and safe product for the owner. Considering that all three manufacturers mentioned in this article are voting members of the AWWA CET Standards Committee, engineers and owners can draw upon the accumulated knowledge and experience of these manufacturers once the standard is issued.
About the Author:
John E. Kraft, P.E., is Vice President of Business Development for Caldwell Tanks Inc. in Louisville, KY. Kraft has been with Caldwell for 15 years, now being responsible for business development for the Tank Company and general management of Caldwell Energy Company. Prior to joining Caldwell, Kraft was an engineer for Allison Gas Turbine, division of General Motors. He is a graduate of Purdue University and a licensed Professional Engineer in several states. He may be reached via e-mail at [email protected].