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PAR 1085 – Denver WWTP South Secondary Improvements

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Colorado, USA
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Public / Government
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36 months
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715 square mile
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Western Summit/McCarthy Joint Venture
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Western Summit
PAR 1085 addition was part of upgrading the aging 1960s-era treatment facility by adding capacity, improving operating capability, and upgrading treatment methods to meet more stringent effluent requirements for nitrogen and ammonia removal, as required by the district's discharge permit.
The South Secondary Improvements project included adding six activated sludge aeration basins, associated centrate and return activated sludge re-aeration basins, five new pump stations and other upgrades to existing systems.
thumb par 1085 denver wwtp south secondary improvements about 1

Project Challenges

PAR 1085 presented several challenges, as the construction schedule was crucial for keeping the existing treatment plant functional and getting the new systems online before the January 2015 deadline. High-strength mass concrete was the majority of the placements, and strict quality control measures were in place throughout the project.
The specification for the mass concrete had tight parameters, and the delivery schedule was fast-paced to get each component built. Many high rates and large volume placements took place in the summer's heat. This was problematic because of the low concrete placing temperature needed for the thermal protection plan.

Project Solutions

When the mass concrete placements started, the project was behind schedule, and the contractor looked to BURNCO to help catch up. To meet the schedule, BURNCO implemented ice in concrete batching to lower the starting temperature of the mix before delivery.
The mass concrete mix called for a low water/cement ratio, a consistently low thermal temperature, and a waterproofing admixture was specified. BURNCO designed a mix that met this criterion by working with our team of vendors, Western Summit and Carollo.
To help control the temperature, we placed most of the concrete starting at midnight or early in the morning. Placing 900 cubic yards in 5 hours required excellent coordination with the onsite and plant batch personnel. The project finished on time because of the construction team's great teamwork and innovative thinking.

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