City of Goodyear Turns to Design-Build
Brad Tackett — Dec 01, 2009
The City of Goodyear, Ariz., located southwest of Phoenix, was founded by Paul Litchfield of Goodyear Tire and Rubber Company in 1917 and incorporated as a city in 1946. The city has annexed approximately 188 square miles with a planning area just under 246 square miles and a current population of 62,550.
Similar to all municipalities in the Phoenix metropolitan area, the City of Goodyear grew at an astonishing rate of 16 percent each year from 2000 to 2006 as people flocked to Arizona. The impact of this fast-paced growth rate was that the City had to play “catch-up” with its water and wastewater infrastructure to keep pace with demands. When the City was obligated to construct multiple water and sewer pipelines in order to meet land developer agreements, it turned to Hunter Contracting Co. and Carollo Engineers P.C. to design and build various water and wastewater pipelines throughout the city. The project met developer and city needs and demonstrated that the design-build process can deliver cost-effective, innovative and high-quality results for a fast-paced construction schedule.
In late 2005, Hunter Contracting Co. and Carollo Engineers were retained, using the qualifications-based selection (QBS) process, to design and build various water and wastewater pipelines throughout the City of Goodyear. The City indicated the pipeline sizes and locations that were to be designed and constructed, including an interconnect to a neighboring potable water supplier as well as an existing well emergency pipeline connection. The overall design-build contract entailed coordination with many stakeholders and agencies, including the City of Goodyear Engineering and Development Services Department, the Arizona Department of Transportation (ADOT), Roosevelt Irrigation District (RID), Litchfield Park Service Company (LPSCo), Maricopa County Flood Control District (MCFCD), other design consultants, and private land developers.
The water infrastructure projects consisted of five separate construction packages totaling approximately two miles of 16-inch ductile iron pipe (DIP), 800 linear feet (lf) of 36-inch DIP, 475 lf of 12-inch DIP, 720 lf of 36-inch high density polyethylene pipe (HDPE), 710 lf of 16-inch HDPE, and 710 lf of 12-inch HDPE. A 700-lf precast concrete utility tunnel was also utilized.
The sewer infrastructure projects consisted of four construction packages utilizing the jack-and-bore trenchless construction method, as well as open trench construction, and totaled approximately 915 lf (boring), and approximately 9,300 lf of 12-inch and 15-inch PVC sewer pipe (open trench). There were a total of nine separate submittal packages in order to expedite the jurisdiction review and approval process.
Benefits of Design-Build
The design-build delivery method entails a single contracting entity to provide both design and construction services. Several benefits of this delivery method include: single point of responsibility for design and construction, team collaboration, construction package selection flexibility, expedited delivery schedule as some items can be pre-purchased, and guaranteed pricing earlier in the project. The City of Goodyear primarily decided to utilize this delivery method in order to take advantage of the expedited delivery schedule and single point of responsibility. The design-build process and team collaboration were key components for this successful project. During a fast-paced project, it is crucial to have all of the decision-makers, such as the City, design engineer and contractor, in the same room and on the same page collaborating on all major decisions. Two of the individual construction packages illustrate the benefits of the design-build process for the City of Goodyear included the LPSCo Waterline Extension to Canyon Trails Pump Station and the 16-inch Waterline Extension Along McDowell Road.
LPSCo Waterline Extension to Canyon Trails Pump Station
This submittal package consisted of three water mains extending approximately a half-mile to an existing booster pump station and reservoir site. The pipe sizes were 36-inch, 16-inch and 12-inch. The challenge with this project was the coordination with ADOT and its proposed widening and half interchange for Interstate 10 that the water mains were crossing. ADOT was in the feasibility stage of the widening process and its design consultant only had design concept drawings that illustrated the proposed right-of-way (ROW) width and the half interchange. ADOT has a requirement similar to all transportation agencies that all pressurized pipelines crossing its ROW be contained in a steel sleeve in order to prevent washout of the roadway in the event of a main break.
Prior to the City or the design-build team knowing of the proposed ADOT widening, the City elected to utilize a utility tunnel concept to cross the ADOT ROW. The utility tunnel consisted of an 8-foot wide by 8-foot tall by 350-foot long (width of the existing ADOT ROW) precast concrete utility tunnel. The tunnel was precast in multiple sections 4-foot in height in a C-channel configuration (top and bottom). The idea of this tunnel was to provide the City access to the pipelines crossing the ROW while providing space for additional pipelines in the future. To keep on schedule, the precast tunnel was pre-purchased from the manufacturer.The utility tunnel concept soon changed when the final design report from the ADOT consultant was provided to the City’s design-build team. The once 350-foot ROW is now a proposed 700-foot ROW. Since the utility tunnel sections were already made and purchased, the team devised an alternative solution that made use of the City’s capital investment without the purchase of additional utility tunnel sections. This solution utilized each individual 4-foot by 8-foot section of the utility vault by placing the sections upside down on a cast-in-place concrete slab with the three individual pipelines supported by preformed concrete cradles. The resulting utility tunnel extended the entire 700-foot width for ADOT’s proposed ROW. The City also selected high-density polyethylene (HDPE) butt-welded pipe within the ADOT ROW to eliminate potential joint failures. ADOT reviewed and approved this innovative approach of providing a secondary encasement within their ROW. The HDPE pipe transitioned to ductile iron pipe outside of the utility tunnel.
16-inch Waterline Extension Along McDowell Road
The land along this mile-long stretch of McDowell Road was being developed as commercial and retail centers with a large shopping mall planned for the future. The City agreed to construct the necessary water and sewer infrastructure in order for these large retail centers to open on schedule. Additionally, to accommodate the commercial development, McDowell Road was being widened (by others) from a two-lane road to a six-lane road with a median along with a new bridge over Bullard Wash. Bullard Wash was being re-channelized and a new community park was being designed and constructed in this area. The proposed 16-inch water main was to be designed within the improved roadway with stub outs for future development.
The water main design and the roadway improvements design were at different completion levels, with the water main ahead of the roadway. The water main design had to be closely coordinated with the roadway earth work due to the extreme cuts and fills anticipated for the new bridge approach and the proposed building pad elevations. Once the roadway elevations were provided, the next challenge was the new bridge and obtaining easements from the MCFCD. Where the water main alignment approaches the bridge, the team decided to divert the main around the bridge and through the wash in lieu of hanging the main on the bridge. This diversion also had to be closely coordinated with the re-channelization of the wash and the future park improvements project. Another challenging aspect of this relatively short pipeline was the coordination between the water main stub outs and the irrigation water provider and users. The undeveloped land surrounding the new shopping centers is primarily being utilized as agricultural farm land and currently being irrigated by open canals. In order for the water stub outs and the majority of the fire hydrants to be constructed, the canal had to be cut and repaired during non-irrigation times.
Conclusion
With a responsive design-build team, a city can rely on the open communication and coordination that it takes to complete a successful project on a fast-paced schedule. If a standard design-bid-build project delivery method was utilized for the above two project examples, the selected contractor would have had numerous change orders and schedule slippage. But since for this project, the City of Goodyear, Hunter Contracting and Carollo Engineers were able to coordinate the design and multiple agency approvals, the project was successful and delivered on schedule.
Overall, the design-build delivery method has provided the City of Goodyear with a single point of responsibility for critical infrastructure expansion and development with cost and schedule certainty.
Brad Tackett, P.E., is a project engineer for Carollo Engineers’ Phoenix office.
