With a current population of nearly 300,000, Gilbert, Arizona, experienced rapid growth from 1980 to 2000, doubling in size every five years. Town officials project that much of the town’s future growth will occur in south Gilbert, where the Ocotillo Bridge and Road Extension project is underway to support the expanding population.
Sundt Construction is serving as the construction manager at risk (CMAR) on the project, self-performing all major grading, utility, and bridge construction scopes of work.
Ocotillo Road, a five-lane roadway with a center turning lane, serves as a critical east-west arterial for south Gilbert. Extending the road has been a long-standing priority in Gilbert's Capital Improvement Plan for over 15 years.
In 2021, the town secured funding through the voter-approved 2022 General Obligation Bond for Transportation Infrastructure, which supported bringing this project through design and construction.
"With the rapid growth of south Gilbert and lots of open country in the area, the town has been looking to build the road out," said Ryan Blair, a Gilbert town employee who is serving as a Project Manager on the project.
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Currently, there is a gap in the road where two regional floodways and a regional basin exist. When the team completes the extension, it will enhance mobility and alleviate congestion on surrounding roadways.
Another expected benefit is safety improvements, which are crucial as new neighborhoods, schools, and commercial centers emerge. The extension will enable residents and visitors to move safely and efficiently throughout the area.
The project will also cut emergency response times in half. Today, emergency response teams have to travel an extra mile because of a gap in the road.
For residents west of the bridge site, current response times range from six to eight minutes. With the bridge in place, Gilbert Fire & Rescue aims to meet its target of arriving within four minutes for 90 percent of incidents.
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Project planners expect the average daily traffic on the 0.85-mile extension to reach 28,000 by 2040.
This greenfield project is not simply about moving large amounts of dirt. Instead, the project involves the construction of four major structures — three vehicular bridges and one box culvert. Three of the structures span a large irrigation canal and two regional floodways. And the fourth, Ocotillo Bridge, will span the 272-acre Gilbert Regional Park and serve as a gateway.
The Ocotillo Bridge is a 406-foot-long, nine-cell, cast-in-place post-tensioned box girder bridge. According to the Town of Gilbert’s website, the bridge's “aesthetic and functional design supports both current needs and future park phases, blending infrastructure with community identity."
In addition to the vehicular bridge spanning the park, the team is constructing two multimodal prefabricated steel arch bridges (one eastbound and one westbound) to span the park.
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"The steel arch structures are 12 feet offset from the roadway, creating a separation from pedestrians and the vehicular traffic," said Sundt Construction Vice President Jeff Hamilton, who served as the Preconstruction Manager on the project.
“There are four iconic pedestrian nodes with custom steel shade canopies that represent a Palo Verde theme established early in preliminary design,” Hamilton added. “The east- and westbound steel arch spans comprise two separate structures with varying heights, offset from one another. The highest span on each side reaches 44 feet, and the staggered design provides more aesthetics that will be accented with variable controlled LED lighting for everyday functional use and special events/holidays.”
The public can take some credit for the bridge's aesthetics. "We solicited feedback from the public and received 7,500 responses, which helped us with [the] design phase," Blair said.
The two other bridges are four-span, 350-foot-long, precast AASHTO concrete girder bridges, spanning the East Maricopa Floodway (EMF) and Queen Creek Wash.
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Before even starting construction, the Town of Gilbert staff knew the project was going to be complicated.
"We chose to deliver the project via CMAR because we felt having the contractor on board during design was critical," Blair said.
The town also hired a firm to provide project, program, and construction management for the CMAR project and to coordinate final design collaboration.
One challenge that arose involved converting the open channel to a concrete box culvert. The team installed the culvert during a dry-up (a planned action to isolate an area for maintenance, cleaning, etc.).
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The Roosevelt Water Conservation District (RWCD), which delivers water for agricultural lands and irrigation purposes, had originally planned to stop the water flow of the RWCD Canal a year later. However, the team was able to get them to advance their schedule.
The change meant the team could start early on the reconstruction of the main canal, converting it to a concrete box culvert for the future roadway alignment in the area. They only had to pump the nuisance water in the job site.
Getting to that point required coordination among multiple agencies, including the RWCD, Flood Control District of Maricopa County, Salt River Project (both Transmission and Distribution), City of Chandler Water, Town of Gilbert Water and Sewer, Cox Communications, Lumen, and the town's traffic signal information systems.
Another challenge was that there were high-voltage electrical transmission lines located within the new road alignment.
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"If we had to keep them in place, we would have had to build bridges in separate phases," Hamilton said. "Instead, we worked with SRP [a water and energy provider] to temporarily move the lines. This enabled us to construct higher-quality infrastructure in less time."
The design team incorporated the high-voltage electrical transmission lines into the superstructure of the regional park bridge — the first time SRP has done so.
“SRP's design consultant presented a concept that will cradle multiple fiberglass conduits to accommodate the heat generated by the high-voltage conductors, which will be organized with customized spacers within multiple cells of the cast-in-place post-tensioned concrete box girder bridge superstructure,” Hamilton said. “SRP also requires non-conductive concrete, and we've been able to source it from our local ready-mix supplier.”
To support the bridge near Gilbert Regional Park during construction, the team is using existing soil to build a temporary earthfill instead of forming the superstructure on falsework. This "soffit fill" method improves safety by keeping crews off elevated work and allows easier access around the bridge.
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"Our smart earthwork approach means the temporary fill will later be reused and placed in areas that need additional materials, saving the town time and money," Blair said.
"During design and preconstruction, we selected lightweight engineered fill that provides the needed strength while reducing load on existing pipelines — protecting the town's water infrastructure," Hamilton added.
There have been two major water events during the project. One involved a water main that was drained upstream of the project into the EMF. The amount of water exceeded the low flow channel that was cut through the work area, causing it to overflow onto the site. The most recent rain event led to a flow rate of 1,100 cubic feet per second in the EMF.
The team mobilized the crane and other support equipment from within the EMF channel and Queen Creek Wash prior to the events.
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As noted above, the town knew the project was going to be technical, which led them to choose the CMAR delivery method.
"We chose Sundt based on their statement of qualification and an interview," Blair said. "We've worked with Sundt previously, and they're currently doing another large project in Gilbert."
"We've worked with [the] town in the past and saw this project in the town's plan,” Hamilton added. “We knew it would be complex and felt our skills suited the town well, so we strategically pursued it."
The guaranteed maximum price for the construction is $122 million, and the project is on budget so far. The biggest challenge to keeping it on budget has been material escalation due to inflation. The town is providing 98 percent of the funding, with the remainder coming from the state.
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Begun in the summer of 2024, the project is scheduled to conclude in the summer of 2026. Hamilton expects to substantially complete the project on schedule, with some closeout occurring in the fall. The water events have caused some delays, but a schedule recovery plan is underway.
Another potential pitfall is the long lead time for the unique fiberglass conduit for the high-voltage power relocation within the bridge. Due to the rapid increase in data center and advanced facility construction within the Southwest region, securing fiberglass conduit is difficult.
When the Ocotillo Bridge and Road Extension project is complete, it will improve access in south Gilbert, support continued growth, and dramatically cut emergency response times.
- Owner: Town of Gilbert, Arizona
- General Contractor: Sundt Construction, Tempe, Arizona
- Designer: Kimley Horn, Raleigh, North Carolina
- Engineer: Wood Patel, Phoenix, Arizona
