A Powerful Job
March 08, 2022
By: Scott Laird
In December 2019, the Salt River Project (SRP), an Arizona utility agency headquartered in Phoenix, selected NDA member Independence Excavating Inc. of Cleveland, Ohio, as the demolition contractor for the Navajo Generating Station decommissioning project. The overall plant demolition and decommissioning program was managed by engineering services company Tetra Tech and included follow-on contracts for landfill and civil restoration. The ultimate decommissioning program was to demolish the plant, restore the property from environmental impacts and return the land to the Navajo Nation, including over-seeding the area with native plants.
The Navajo Generating Station (NGS) was constructed in the early 1970s and was a 2,250-megawatt coal-fired power plant located in the Navajo Nation near Page, Arizona. The NGS, which was owned jointly by SRP, the United States Bureau of Reclamation, NV Energy, Tucson Electric Power, Arizona Public Service, and the Los Angeles Department of Water and Power, supplied electrical power to Arizona, California and Nevada and provided power for pumping the Colorado River to central and southern Arizona. Also of note, prior to demolition, the 775-foot stacks were the third highest manmade structure in the state of Arizona. The plant ceased operation in the fall of 2019, and SRP, on behalf of the plant owners, began the decommissioning process.
At one time, the plant employed approximately 1,200 people, including the nearby dedicated coal mine and railroad, which supplied up to 24,000 tons of coal per day. The majority of those dedicated employees were from the Navajo Nation. Additionally, the project workforce goals included a hiring priority for Navajos.
Independence Excavating was chosen as the demolition contractor due to its qualifications and price, which included value to SRP, safety record and statistics, performance ability for this scope, as well as past performance on similar projects. The award included a shared savings program regarding the salvage of recyclable materials, which resulted in further savings to the SRP and the owners.
The Strategy
The overall strategy and implementation was a field-based safety program coupled with a sequenced and strategic site flow to produce a project with ground-up safety and planning coordination in an aggressive but well planned out schedule for completion. The safety program integrally included the daily task analysis as well as the high-hazard task planning with the field crews as a key component. As with the project schedule, constant evaluation of operations and adjustments as necessary were implemented to optimize opportunities for gain, while keeping abreast of daily field issues and progress.
Planning for the project started with mobilization of workforce and equipment in February 2020. The work commenced in March 2020 and will be completed in March 2022. Shortly after starting, the project was paused due to the COVID-19 pandemic, as infection rates on the Navajo Nation Reservation were some of the highest in the country. Following a four-month shutdown, Independence, SRP and Tetra Tech developed a program of worker safety and monitoring for COVID-19, which was followed for the duration of the project with minimal impact to worker safety and exposure or progression of work. Demolition resumed in August 2020 at an expedited pace with explosive felling events in October 2020, December 2020, January 2021, March 2021 and June 2021. Between these events was an efficient and monumental task of cleanup, processing and shipping of material to recycling facilities. The job shipped 10,000-11,000 tons of just scrap steel per month regularly during the peak hauling. The substantial completion of the structural and building demolition was completed in September 2021. Remaining phases of underground removal and remediation will carry the project to March 2022, which is on the original schedule, making up the COVID-19 impacts, and all without any impact to the safety performance of the men and women in the field.
The overall strategy of the job was to work through the site from east to west and to ensure the regular generation of material for processing and shipping. The logistical challenges of the site location required us to ensure the maximum utilization of every available haul truck to continuously haul, many times to mills and recycling facilities over 10 hours away.
Another part of the strategy was to time and coordinate the explosive felling activities throughout the process and overall direction through the site. A total of seven blast events were successfully executed on the job in the sequence per the overall schedule. Those events included 775-foot-tall stacks, 60,000 tons of three boilers in one shot, and turbine pedestals on 40 foot elevated slabs 9 feet thick and supported by 14 legs that were 10 feet by 14 feet of reinforced concrete. The blast events were well coordinated and monitored for vibrations to ensure no damage to the surrounding infrastructure that would remain or the active electrical switchyard located just 800 feet away.
Project Milestones
The following is a generic walkthrough on a monthly and milestone basis:
January 2020: Purchase order execution and mobilization planning.
February 2020: Mobilization.
March 2020: Commencement of environmental preparations, including asbestos abatement (contracted with SRP directly), de-energizing the plant, and fluid and hazardous material removal.
March 28, 2020: SRP, Tetra Tech and Independence Demolition agreed to shut down the project due to rising infection rates in the Navajo community and concern for our workers.
March through June 2020: Job was idle.
July 2020: Remobilization planning and coordination to restart the project. This included generating COVID-19 monitoring and protection programs that were employed through the remainder of the project. They were successful, as infection impact was minimal and no further shutdowns were required.
August 2020: Remobilization and resumed environmental preparations and demolition of ancillary and support units in preparation for the main unit demolition.
Oct. 29, 2020: First explosive felling of three 220-foot-tall stacks in one shot. The stacks were between the 775-foot stacks and the precipitators, and they were felled to the north and clear of any damage to the adjacent units still to be prepped. Cleanup of the debris and preparation of the 775-foot stacks commenced immediately.
Dec. 18, 2020: Explosive felling of the three 775-foot stacks and one electrostatic precipitator. These four items were felled in one time-delayed shot and were felled also to the north as planned and engineered. The event was practically a community event to remove the iconic landmarks of the area, with cars lining public highways for miles. Cleanup of the stacks commenced immediately as well as preparations of the remaining two precipitators for the next felling.
Jan. 19, 2021: The north two electrostatic precipitators, each 208 feet tall, were explosively felled to the east. Each of these units was a double-stack flue-gas treatment unit and approximately 8,000 tons each. Cleanup of the precipitators commenced immediately in order to have the area completely clear for the boiler felling event just six weeks away.
March 3, 2021: The three boilers were explosively felled on one shot. The units fell to the east as planned and engineered by Special Inspection and Design. The units were strategically gutted and removed of nonstructural components prior to the shot in order to execute the design. Additionally, the coal silos that were on the back side of the boilers were designed to be felled with the boilers, while not impacting the adjacent turbine bay building, with structural columns of each building just 4 inches apart. The design was executed flawlessly, as the turbine building remained unharmed for the precutting and preparation of the turbine precutting and pedestal demolition.
June 2021: The turbine pedestals were shot in three events, one per week. The magnitude of concrete required explosives to demolish the structures, reducing worker exposure and significant machine hours. The turbines themselves were precut to enhance breakup as they fell. The surrounding building of the turbine bay was retained as blast protection during the shots in order to prevent impact or flying debris to the active switchyard servicing much of Arizona, located just 800 feet to the west. Each of these shots were a success.
July 2021 through September 2021: The crews worked tirelessly on cleanup and remaining demolition of the main unit. By September 2021, the main unit of power generation was substantially completed with only processing, cleanup and remaining underground work to be completed.
July 2021 through February 2022: The underground circulating water pipe was remediated, removed, and a drainage system for collection of perched groundwater was installed. The circulating water pipe had a PCB and asbestos coating for corrosion protection, so it required special handling, worker protection and monitoring while removal operations were conducted. This was another team effort among Tetra Tech, SRP, the abatement contractor and Independence to execute this safely and productively. Salvage material was scheduled to also be hauled out through February 2022.
March 31, 2022: Final cleanup, grading and demobilization scheduled.
Challenges and Successes
The project itself was a significant challenge, especially to perform and execute it so effectively. The biggest challenges included the following:
Safety
The safety challenge was on multiple fronts, including the magnitude of the project, the complexity of the project, the coordination of multiple trades in high-risk activities and complying with various evolving COVID-19 protocols. We had two full-time, regular safety personnel on-site at all times, and at times employed more than that for specialized tasks. The monumental task of organizing and documenting the programs, protections and monitoring was more than a full-time job. The coordination with the field operations on every day-to-day task and activity was a significant success; however, more than that success, the day-to-day coordination with each and every crew member to plan work, monitor conditions and ensure that every co-worker was watching out for each other is an accomplishment like very few projects. Our safety team led the project successfully, but the entire crew championed the success of our safety record on this project.
Schedule
The challenge of the schedule was, in short, the objective to demolish, process and ship 120,000 tons in 23 months. Added to that challenge was the COVID-19 pandemic in the first months of the project. Our team planned and executed the work to ultimately recover the schedule and, above all, accomplish this without any detriment or compromise to keeping our crews safe.
Logistics and Production
With Page, Arizona, being located in the northeast part of the state, it did not lend itself to easy access to rail or recycling facilities. Add to that the sheer magnitude of the plant, and it took a well-managed and coordinated plan to execute this project on schedule. The men and women of the workforce worked tirelessly to efficiently demolish, process and identify the most effective homes for each and every component and material of the demolition.
COVID-19
Similar to every project in 2020, the job was affected by the pandemic and required the partnering efforts of the owner, construction manager and contractor to work through the program and monitoring to ultimately keep our workforce safe to execute the project at a high level.
Community Involvement
From the Navajo hiring preference and success of that hiring effort to the community outreach, Independence made continual efforts to make our mark for the better on the surrounding community. Efforts included COVID-19 care packages from Cleveland to the Navajo Nation’s LeChee community and local medical centers, domestic water tank retention systems for residents who did not have access to potable water, and support of area youth organizations such as 4H and local sports. Independence considered the community involvement and support a major success of the project.
Executing at High Levels
We consider this project an absolute success! Our team rose to meet, overcome and make success stories of each of the challenges presented to us. The efforts of the project team, which included the partnering effort of our owner, SRP; the construction manager, Tetra Tech; and Independence; as well as those on the field level such as operators, laborers, drivers, subcontractors and demolition professionals, executing high risk and intricate work safely, efficiently and effectively. This project is a model of taking challenges and difficult situations, assessing the paths forward and executing at high levels across the project from owner level to each and every laborer, operator and site individual.
The largest success on this project was the safety record with no corporate lost-time injuries and no recordable incidents. Two incidents with subcontractors were evaluated and remedied as a team, and any identified hazards or near misses were identified, discussed and reviewed with the entire team in an all-encompassing effort to ensure every individual on the project was safe, productive and successful.