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17 May 2017
The AZ Water Association (Arizona) has named the 91st Avenue
Wastewater Treatment Plant Digester 1 Rehabilitation in the City of
Phoenix as the wastewater treatment plant (WWTP) project of the
year, recognizing the proactive planning, collaborative process and
design innovations that resulted in an efficient implementation of
upgrades to this critical public infrastructure.
The need for upgrades to the plant to protect public health was
identified by the City of Phoenix through their asset management
program. GHD worked with PCL Construction, the general contractor,
to determine what rehabilitation work would be most effective, and
the City actively encouraged design innovations throughout the
rehabilitation process. It was determined that appropriate
rehabilitation activities would include the removal of the existing
steel dome, pipe and appurtenances, repair of concrete and steel
structures, and the design, fabrication, and construction of a new
steel dome and features. The project delivery method allowed PCL
Construction and GHD to collaborate from the very beginning of the
process, allowing them to identify and mitigate impacts and
challenges that could compromise the schedule or cost of the
project.
The GHD team conducted a condition assessment, topographic
survey, 3D-scanning, and mapping of the existing components in
order to develop a holistic approach and design construction
documents for the concrete repairs and steel dome removal, as well
as the replacement of one 56-year-old digester, which is a 1.2
million gallon, above ground concrete tank, that is 90 feet in
diameter and 30 feet tall with fixed steel cover.
Prior to construction, PCL implemented two mock-ups to ensure
realistic conditions were created, which enabled the team to
identify and correct any constructability issues before
construction began on Digester 1. The coordination between GHD and
PCL resulted in a lasting solution that will serve the City of
Phoenix for years to come.
“The successful management of such a large and complex project
requires multi-discipline approaches to develop, design, and
deliver the rehabilitation of such aging infrastructure,” said GHD
Project Manager Frederick Tack. “This is a significant project,
rehabilitating large public infrastructure, that has demonstrated
the value and benefit of effective life cycle planning and
budgeting to meet the wastewater treatment and water reuse needs of
the community.”
Originally built in the early 1960’s, the 91st Avenue WWTP is
the largest in Arizona with an ultimate permitted design flow of
230 MGD. It includes seven individual activated sludge treatment
systems operated in parallel, and also serves as a reclamation
plant that provides an average of 60 MGD to the Palo Verde Nuclear
Generating Station (PVNGS) for reuse. The project team was able to
prepare the design and construction documents within six months,
and PCL Construction completed the demolition, rehabilitation, and
dome replacement in just over 12 months. By November 2016, the work
was substantially completed and Digester 1 was turned back over to
the 91st Avenue Wastewater Treatment Plant for operation.
The AZ Water Association is a nonprofit educational organization
for water/wastewater professionals dedicated to preserving and
enhancing Arizona's water environment, and serves as the Arizona
section of the American Water Works Association (AWWA) and the
Arizona member association of the Water Environment Federation
(WEF). The 2017 awards were presented at its 90th annual conference
and exhibition in Phoenix, AZ, May 3-5 2017.
GHD is one of the world’s leading professional services
companies operating in the global markets of water, energy and
resources, environment, property and buildings, and transportation.
Privately owned by our people, we deliver engineering,
architecture, environmental and construction services to public and
private sector clients across five continents and the Pacific
region. Committed to creating lasting community benefit, we connect
the knowledge, skill and experience of our 8500 people with
innovative practices, technical capabilities and robust systems.
See http://www.ghd.com/.
PCL is a group of independent construction companies that
carries out work across the United States, Canada, the Caribbean,
and in Australia. These diverse operations in the civil
infrastructure, heavy industrial, and buildings markets are
supported by a strategic presence in 31 major centers. Together,
these companies have an annual construction volume of more than $7
billion, making PCL one of the largest contracting organizations in
North America. See http://www.pcl.com/.
