By: Stephanie Johnston
Name: Airport Water Reclamation Facility
Owner: City of Chandler, Ariz., Municipal Utilities
AEC firm: McCarthy Building Companies Inc.
Cost: $75 million
Project delivery method: Construction management-at-risk (CM@R)
Completed: November 2009
Runway extensions aren't just about pavement. When the project's going to double the number of people using terminal facilities, they're also about wastewater treatment capacity. Put the service area in a desert area where treated effluent recharges drinking water aquifers or irrigates land, and they're also about integrating planned capacity increases systemwide.
And let's not forget concerns about odor.
Three thousand people live within half a mile of the proposed 850-foot extension to bring total runway length to 5,700 feet. Summers are very hot and very windy. Though studies didn't find any adverse land use, noise, or environmental impacts, having already experienced blowing dust, residents were wary.
Municipal Utilities, which manages and operates the airport's treatment plant, balanced all these factors when expanding liquid processing capacity from 10 to 15 mgd and 15 mgd of equivalent solids.
To meet projected peak demands without lowering pressure systemwide, the department's master plan is designed to allow operators to shift flows between the airport and two other reclamation facilities. Making all the necessary connections without disrupting operations at any three required more than 100 maintenance of operations (MOPO) tie-ins and some last-minute changes in plans.
The liquids treatment train was brought online six months before the solids train to send Class A+ treated effluent to the airport's new recharge basin complex. With the existing plant already operating near capacity, flows increased considerably. That's when everyone realized it would have to be re-rated to 12 mgd before the final push to 15 mgd, and began expediting construction of several facilities. It worked.
And what fun is a project that doesn't have a last-minute weekend crisis?
One Saturday morning, a 20-year-old force main failed, releasing raw influent into a drainage ditch alongside a road and causing sinkholes. But in the end, the project was on budget and saved $3 million with no downtime.
“There were two change orders resulting in a net credit to the city, an accomplishment unheard of in a three-year construction schedule,” says Utility Operations Manager Kim Neill.
As for public relations, the department began working with residents a year before the project broke ground. As a result, all basins and channels are covered and treatment facilities have odor control systems. With zero dust violations, the project even earned a berth on the county's air quality honor roll.