CSCE Monthly Dinner Meeting at the Norwalk Inn

March 22, 2023

Please join CSCE at our monthly meeting at the Norwalk Inn on Wednesday, March 22, 2023. At this meeting, Daniel McCarthy, P.E., of Preload, LLC, will give a presentation on the Unique Design-Build Features of Three 22-Million Gallon Prestressed Concrete Water Storage Tanks at the Baltimore County-Fullerton Reservoir. As the General Contractor of this $75,000,000 project, Preload was responsible for all aspects of tank design and project execution including excavation of over 1,000,000 cubic yards of soil, installation of large diameter yard piping interconnections, vault structures, sodium-hypochlorite disinfection facility, electrical, instrumentation & various other project aspects. The three large partially buried AWWA D110 Type-3 prestressed concrete tanks featured 300-ft diameter x 41-ft tall main walls, column supported flat roofs and double concentric ‘C’ precast concrete baffle walls. The structural tank floor was designed to support the interior concrete baffle walls & roof columns with minimal differential settlement.

This was the largest single contract in the history of the prestressed concrete tank industry. The structural work was completed between 2017 and 2020 and the system went into full operation in 2022. Preload’s main site and piping subcontractor was Allan Myers, Inc., and the Schnabel Foundation Co. provided specialized geotechnical investigations for the Team. The owner is Baltimore County, and their Design Consultant was Gannett-Fleming, with Peer Design Review by Hazen and Sawyer. 

The discussion will mainly focus on basic structural design and construction of the tank components, including structural mat concrete floors; sliding base cylindrically precast-prestressed concrete wall panels with seismic cable anchors to the floor; concentric C-shaped precast concrete baffle walls (for chlorine contact time) designed for sloshing seismic loads; 300-foot diameter column supported concrete two-way flat slab roofs designed without expansion joints which were virtually ‘crack-free’ using new temperature & shrinkage reinforcement formulas which are now part of ACI350-20 Code). An on-site concrete plant was established for the project. A brief overview of the geotechnical investigation, foundation design, and removal and replacement of unsuitable soils on one of the three tanks will also be discussed. The construction is designed with sustainability in mind using efficient thin concrete flat plate and cylindrical shell elements with special attention given to durability and low lifetime maintenance requirements.