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Planning for Decommissioning

Making the decision to decommission its 2.8-MW Childs and 1.4-MW Irving hydroelectric plants on Fossil Creek was only the first step for Arizona Public Service. After submitting a settlement agreement and a removal and restoration plan to the Federal Energy Regulatory Commission, the utility began the removal. Decommissioning is to be complete by June 2010.

By Phil S. Smithers

On June 18, 2005, generation ceased at Arizona’s first commercial hydroelectric plant – 2.8-MW Childs – as well as at the 1.4-MW Irving plant. The decision to decommission these two facilities was the result of years of collaboration between project owner Arizona Public Service (APS), environmental groups, all levels of government, academia, historical preservation groups, and others.

The Childs (completed in 1909) and Irving (completed in 1916) facilities were considered engineering and logistical marvels when constructed. The plants, which use water from Fossil Creek, provided electricity essential to the state’s growth, first powering the booming mining operations and later energizing the communities of Prescott and Phoenix.

In 1999, at the urging of many environmental groups, APS decided to restore full flow to Fossil Creek. Despite the $13 million cost of decommissioning and lost annual revenue from plant operations, APS agreed to close the Childs and Irving facilities. “Restoring Fossil Creek to its natural flow outweighed the business benefits the facilities provided,” said Jack Davis, APS president and chief executive officer. “Our decision was based on what was best for the residents of Arizona.”

The history of Childs and Irving

When construction of Childs began in 1907, Arizona was four years from statehood. Much of central Arizona was a wilderness of steep piney mountains, high desert plateaus, and deep rocky canyons – with few roads. Access to the nearest railroad required a two-day horseback ride over rugged terrain.

The site was chosen because of the abundance and dependability of the water in Fossil Creek. The creek’s source, Fossil Springs, flows at a constant rate of 43 cubic feet per second (cfs). Pioneers named the springs and creek for the fossil-like appearance of its rocks and vegetation, which were coated with calcium carbonate deposits from the water. Before the creek was diverted for hydro generation, it featured large travertine formations along the 14-mile course – ideal spawning grounds for native fish.

More than 450 mostly American Indian and Mexican laborers toiled for more than a year to build this technological wonder. They first had to build 40 miles of road to haul the tons of concrete and reinforcing steel to the site. They then constructed the Childs powerhouse on the Verde River, 10 miles away from a water diversion on Fossil Creek, and nearly 8 miles of concrete flume, steel pipe, tunnels, and penstocks to bring water to the plant.

The Childs development includes the Fossil Creek diversion dam, which diverted water into the forebay of the Childs flume, and a 4.5-mile-long conduit to take water to the regulating reservoir, known as Stehr Lake. From the lake, water continued through a 4,888-foot-long pressure tunnel and a 1,394-foot-long concrete pipe leading to the concrete surge tank. Water then entered a 4,635-foot-long penstock leading to the powerhouse, which contained three 3,000-horsepower water wheels and three 1,800-kW generators. From the powerhouse, water entered a short tailrace and was discharged into the Verde River. Other fixtures included a step-up substation, two 69-kilovolt transmission lines about 200 feet long that run from the substation to a switchyard; and appurtenant facilities (offices, operator housing, and maintenance shops).

The Childs plant began generating electricity in November 1909, mainly to supply the copper mines in Jerome and gold and silver mines and mining camps in the Bradshaw Mountains. By the end of 1914, World War I increased demand for minerals, and the mines needed more power. This spurred construction of the Irving plant, completed in 1916.

The Irving development included Fossil Springs Dam and nearly 20,000 feet of steel flume on wood trestle. A 600-foot-long penstock supplied water to a powerhouse containing a 2,100-horsepower turbine and a 1,600-kW generator. From the powerhouse, water entered a tailrace that discharged into a forebay leading to the Childs Flume. Other structures included a step-up substation, a 69-kilovolt transmission line about 6.6 miles long that runs from the substation to a switchyard, access roads, and appurtenant facilities.


Fossil Creek got its name from the unique travertine formations created through the deposition of calcium carbonate in the water. When removal of the Childs-Irving project is complete, a 14-mile stretch of the creek will again flow freely. (Photo by Nick Berezenko, courtesy of APS)
Click here to enlarge image

Through the 1920s and 1930s, the two plants also provided power to light the burgeoning communities of Prescott and Phoenix. For the rest of the century, the Childs and Irving generators continued to produce electricity, even as APS built more and larger gas, coal, and nuclear generating facilities. By the latter half of the century, the Childs and Irving plants were dwarfed by other APS facilities.

The Childs and Irving facilities were listed as an American Society of Mechanical Engineering Historic Landmark in 1976 and were added to the National Historic Register in 1991.

Deciding to decommission the projects

In the late 1980s, APS began to move forward with renewing its 50-year Federal Energy Regulatory Commission (FERC) license for the Childs-Irving project. Although these plants only provided a total output of 4.2 MW, they were still profitable and inexpensive to operate.

However, in 1998, as FERC was about to renew the license, APS reached the decision to decommission Childs and Irving. APS made this choice based on the urging of many environmental groups to restore full flow to Fossil Creek. After weighing the business benefits provided by the facilities against the benefit to the state to restore this natural resource, APS decided decommissioning the projects was in the best interest of the residents of Arizona.

In November 1999, after months of discussions with representatives of several environmental groups, an “agreement in principal” was reached for the Childs-Irving Hydroelectric Project. APS filed a surrender application with FERC in early 2001. For seven years, APS has worked with environmental organizations, historical preservation groups, biologists, engineers from Northern Arizona University, and federal, state, and local agencies to support the surrender of these facilities.

Holding discussions with stakeholders

In 1999, APS began holding meetings with more than 50 stakeholders to solicit input on the decommissioning process and concerns regarding plans for the facilities. Participants included representatives of environmental organizations, historical preservation groups, agencies such as the Fish and Wildlife Service (FWS) and Arizona Game and Fish, and residents who grew up on the banks of Fossil Creek. In addition, as the land owner, the U.S. Forest Service (USFS) was a key player in the discussions.

Through six meetings covering a range of topics – including FERC process, environmental and historical issues, and dam removal – APS developed a settlement agreement to provide a foundation for surrendering these facilities. The agreement was finalized in late 2000 and signed by APS, the Yavapai Apache Nation, American Rivers, Southwest Center for Biological Diversity, Northern Arizona Audubon Society, Nature Conservancy, and Arizona Riparian Council.

This settlement agreement called for APS to return full flows to Fossil Creek no later than December 31, 2004, assist in the transfer of water rights to USFS, and complete the removal of facilities by December 31, 2009. The original schedule for returning flows was delayed because APS did not receive permission to start construction activities until late March 2005. Generation ceased on June 18, 2005. The rest of the work is on schedule to be completed by the end of 2009.

Developing a removal and restoration plan

Another outcome of the stakeholder meetings was development of a removal and restoration plan. This document, which took about four months to develop, describes structures throughout the 14-mile reach and details which project facilities will remain and which will be removed.

To restore native fish in Fossil Creek, the U.S. Department of the Interior’s Bureau of Reclamation, FWS, USFS, and the Arizona Game and Fish Department conducted a native fish restoration project. As part of the project, non-native species were removed from the creek, and Reclamation personnel constructed a fish barrier that will keep non-native fish from entering the restored area. This work was completed in the fall of 2004.

Getting FERC approval

Once the settlement agreement was signed, APS set the FERC decommissioning process in motion. The utility drafted a surrender application, requesting that the plants be shut down and the facilities decommissioned and removed. Because much of the high-level planning scheduling had been completed during development of the settlement agreement, the application was built largely with the agreement as its base.

When they learned that APS intended to submit a surrender application for Childs and Irving, some organizations expressed interest in taking over the operating license for the facilities. Neither APS nor others wanted this to happen. The plants represented less than 1 percent of the power the utility produced, and the possibility of returning flow to a unique water system in Arizona outweighed the negligible production.


The 2.8-MW Childs power plant, built in 1909, will be left in place when the Childs-Irving project decommissioning is completed in 2010. (Photo by Nick Berezenko, courtesy of APS)
Click here to enlarge image

Before filing the surrender application, APS needed FERC to clarify what would happen to the facilities if FERC did not approve the application. It appeared APS would not be allowed to re-initiate its licensing application, and the utility never intended to give these facilities to another operator. In December 2001, FERC said it would allow APS to continue the licensing application if the surrender did not move forward.

APS submitted the surrender application to FERC in April 2002. In July 2002, FERC provided APS with an extensive list of issues needing clarification in preparation for development of the draft environmental assessment (DEA) and historic properties management plan (HPMP). This initiated a nearly three-year process by APS to finalize the surrender.

Beginning the work

While working through the surrender application process, APS staff were planning and engineering for removal of the facilities, many of which were built on rough and sensitive canyon walls. As such, removal presented an overwhelming set of engineering challenges.

To manage the work, APS broke the facilities down into 20 distinctive parts or “reaches.” Each “reach” was determined by its unique engineering attributes. For example, the nearly 4.25 miles of wood trestle-supported flume upstream from the Irving plant begins with Fossil Creek Dam and is interrupted in the middle by an inverted siphon through a deep canyon. The sections of flume before and after the siphon were designated as separate “reaches.”

After breaking the project down into manageable parts, APS created a describing document. This “area of potential effect” document became the primary source for description and detail on how the facilities would be removed.


Several miles of flumes snake through central Arizona, taking water from Fossil Springs to the powerhouses at the 2.8-MW Childs and 1.4-MW Irving facilities. The flumes and supports are being removed as part of the Childs-Irving decommissioning. (Photo by Nick Berezenko, courtesy of APS)
Click here to enlarge image

APS also developed a removal schedule to tie all reaches together over five years of planned deconstruction. This schedule was developed using Microsoft Project. The schedule had to coordinate the removal activities to allow for removal of some facilities for construction access to other areas. It also had to allow for limited access during nesting for sensitive species. In addition, USFS, the U.S. Fish and Wildlife Service, the Arizona Game and Fish Department, and APS developed species adaptive management techniques that will be applied during the course of the removal.

APS engineering developed construction – or deconstruction – drawings to support the area of potential effect document. APS performed a complete walk-through of facilities to determine accessibility and environmental effects. APS hired aerial mapping consultants Kenney Aerial Mapping of Phoenix to complete aerial photography of the entire project to aid in planning. In addition, APS hired Golden Rule Survey of Payson, Arix., to perform several specific surveys and mapping projects. To complete construction drawings, APS used Autodesk’s AutoCAD and Land Development Desktop. APS’ design group overlayed much of the layout of the facilities in vector format on externally referenced raster files and aerial photography that had been completed for the entire project.

Shutting down the generating facilities

APS returned Fossil Creek to its full flow in June 2005, revitalizing 14 miles of wetland ecosystem valuable for wildlife habitat and creek-side recreation. Once the plants were shut down and full streamflow was restored, APS employees began to remove the power plant structures. When deconstruction is complete, the Childs powerhouse, penstock, icehouse, siphon piping, and foundation will remain as historic remnants of the facilities. The sites are scheduled to be turned over to USFS by the end of 2009, and USFS is working on its forest management plan for the sites.

Lowering Fossil Springs Dam

One area of difficulty was the removal of two diversion structures in Fossil Creek. The smaller structure at Irving was 20 feet long and 5 feet tall and could be removed with relative ease. However, at 100 feet long and as much as 45 feet tall, Fossil Springs Dam provided a larger challenge. This dam retained several pools between it and Fossil Springs. This riparian area is home to several sensitive species and retains a century of sediment buildup. Care had to be taken to prevent effects to both during deconstruction.


Removing pipe bridges associated with the 2.8-MW Childs and 1.4-MW Irving hydroelectric facilities provides unique engineering challenges. Special equipment will be designed to remove and transport the pipes for disposal. (Photo by Nick Berezenko, courtesy of APS)
Click here to enlarge image

Through negotiations with USFS, APS put in place an adaptive management plan that features removal of 14 feet from the top of the dam by early 2008. This will allow for minimal effects on the surrounding area from deep deconstruction of the dam, while allowing the remaining concrete to blend into the current rock formation as travertine build-up occurs. Ultimately, to control sediment release, water will be diverted during deconstruction from one end of the dam to the opposite end through temporary trench and pipe. After deconstruction is complete, sediment will be allowed to move naturally through large storm events and spring runoff. Spoils from the dam will be disposed of at a nearby site to reduce truck traffic in this sensitive area. The disposal area then will be covered with native soil and revegetated.

Removal of the top 14 feet of Fossil Springs Dam is scheduled for completion in late 2007 to early 2008. By scheduling the dam removal in the latter stages of the deconstruction, stabilization and adaptation of Fossil Creek should be accomplished prior to reduction of the structure.

Removing appurtenant structures

The proposed decommissioning raised many additional engineering challenges, including the removal of nearly 4.25 miles of semi-circular steel flume supported on treated wood trestle. Much of this flume is on the edge of steep canyon walls, only allowing for manual removal. In most areas, this flume is not accessible by equipment and must be removed “upon itself” to material staging areas. Large quantities of wood and steel must then be removed down a narrow canyon road to large bins, then transported nearly 50 miles to a waste disposal facility.

In addition, there are ten pipe bridges throughout the project that need to be removed. These steel pipes are 60 inches in diameter and have mineral buildup in them that increases their weight by nearly three times. These bridges are located in nearly inaccessible areas that pose different engineering challenges. Bridge 10, the longest bridge, is nearly 1,000 feet long and has one span between support bents of 70 feet in length. Removal will include large amounts of support rigging and specially designed “carts” to transport equipment and remove pipe segments.

Lessons learned

In the process of decommissioning the Childs and Irving hydro facilities, APS has learned several valuable lessons:

– Open communication is key. Effective and open communication with numerous agencies during the planning and NEPA and NHPA processes was extremely important. Clear and succinct communication of plans and issues allowed APS staff to use cost-effective adaptive management plans and techniques. Most important were the relationships and trust developed with local, state, and federal agency personnel during the seven-year decommissioning and removal process.

– Take advantage of expert assistance. In developing studies and engineering analyses, APS relied on consultants familiar with the area and agency personnel. A master agreement with the Northern Arizona University engineering and biology departments also provided quality and time-sensitive research and engineering while helping to keep consulting fees in check.

– Protect the project’s historical significance. The historic value of Childs and Irving is not being ignored. APS is working with local historical groups and the surrounding communities to preserve historical structures, leaving the Childs powerhouse and icehouse building – two of the plant’s original structures – along with other notable historic elements. The utility also is working with area museums to catalog and store historic documents and artifacts. Some prominent artifacts, such as the original turbine-generator from Irving, may be displayed at a regional museum. APS is working with these museums to develop a traveling exhibit highlighting Arizona’s original hydro plants and their contribution to the state’s economic development.

Mr. Smithers may be reached at APS Facility Siting, P.O. Box 53933, MS 4030, Phoenix, AZ 85072; (1) 602-493-4202; E-mail: phil.smithers@aps.com.

Phil Smithers is project manager for Arizona Public Service’s Facility Siting Division. He is managing the Childs-Irving decommissioning.


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