The decision of the City of Olathe, KS to pursue a design-build delivery method to expand its existing 17-mgd water treatment plant to 36 mgd and then retaining Carollo Engineers to perform a feasibility study, were essential first steps towards achieving a successful project conclusion.
Following the feasibility study, the City not only contracted with Carollo for 30% design of the expansion; but also a joint venture of Carollo Engineers and Garney Construction to complete the design and construct the treatment plant expansion. This award-winning design-build project included the integration of membrane filters into the existing retrofitted lime-softening facility.
The decision-making process
A critical factor in the decision-making process was that the City of Olathe needed to complete the first stage of the plant’s expansion in less than a year. At the same time, the single greatest challenge to achieving this schedule milestone was the need to develop a workable yard-piping configuration, that included the existence of a large number of basins and outlet location.
This challenge was resolved by the Carollo/Garney team developing a computer model to optimize piping sizes and location; and completing the complex yard piping with a 72-hour plant outage with seven major tie-ins. The tie-ins were completed 26 days ahead of schedule, resulting in an estimated savings of $40,000 due to not needing to purchase water from a neighboring utility.
The use of design-build delivery, in this instance through a fixed-price procurement, further enabled City managers to take advantage of the opportunities to integrate innovative solutions for the project. Among the many innovative ideas that made it possible to design and construct the project within the prescribed budget, was the ability to reconfigure the existing basins to increase basin capacity without having to build additional basins. This innovative solution of reconfiguration made it possible to optimize plant operations and ultimately reduce chemical usage, thus saving the City of Olathe over $125,000 a year.