IN THE SUMMER OF 2005, SALT RIVER PROJECT FACED A VEGETATION MANAGEMENT CHALLENGE on its electric high-voltage transmission lines that it had never dealt with before — a challenge that put the utility well outside the definition of normal line clearance.
For nearly a decade, Salt River Project (SRP; Phoenix, Arizona, U.S.) had maintained a successful management program keeping vegetation clear from its transmission and distribution rights-of-way, as well as keeping pace with the drought conditions that Arizona had been experiencing for more than seven years. With the drought came a major Bark Beetle infestation throughout the state, which was not only devastating to the beautiful landscape but was turning trees into excellent fire fodder, creating some of the most dangerous Arizona wildfire seasons in recent memory, particularly in the higher elevations.
But all that changed in the winter of 2005 when Mother Nature switched gears and Arizona experienced a record rainfall of 14 inches (360 mm) of precipitation, compared with the previous 15-year average of 6.9 inches (175 mm) of rainfall per year. While this additional rain was a welcome relief in the higher country, it created a real hazard in the lower desert regions when the higher-than-usual desert growth became a dry hotbed of fuel, particularly as summer temperatures soared over 100°F (38°C). This newly added fuel, coupled with the beetle-caused pine debris in the forests, led to the worst wildfire season in Arizona history. More than 720,000 acres, 10% of the state's total area, was scorched during the seven-month-long season with the largest single fire covering more than 240,000 acres.
For SRP, it all started on Memorial Day in 2005 when a call came into the utility's Power Dispatch Operations Center reporting a wildfire — one of the worst messages a utility with a vulnerable electric system could receive. A man-caused fire along Arizona's Gila River spread quickly through wild grass and Salt Cedars, pouring thick black smoke and carbon into the air. It didn't take long before this smoke, with conductive properties, moved through a major electric transmission system corridor consisting of two 500-kV circuits from Palo Verde Nuclear Generation Station, the largest nuclear power plant in North America, and one 345-kV circuit and three 230-kV circuits. In less than 90 minutes after receiving the fire alarm, one of the 500-kV circuits, the single 345-kV circuit and one 230-kV circuit had relayed (or tripped out) as a result of the flash-overs from the smoke and ash. The 500-kV and 345-kV circuits remained out of service for more than three and a half hours until smoke from fire-fighting efforts subsided, allowing the lines to be safely re-energized.
NORMAL LINE CLEARANCE
At this point, it is important to note the vegetation that started the fires was located outside normal line-clearance boundaries. SRP had maintained its lines as part of its mandate but, upon investigation, discovered there was no tall growth that could fall into the lines. It turned out that the vegetation responsible was, in fact, the dry hotbed of excessive new growth in outlying areas, which grew as a result of the abnormally wet winter months.
In response, SRP's upper management issued an immediate directive to the Line Maintenance department to conduct emergency reconnaissance of the extra-high-voltage system in the urban and desert areas, and report on potential fire fuels and risks. The focus was on all major transmission corridors, including river and wash crossings, ravines and other lower-lying areas in search of large amounts of vegetation, as well as other fire fuels generated by the high amounts of rainfall. Under normal conditions, these inspections would have been carried out mainly in the forested areas where the sheer numbers of trees are usually the problem. The search for large fuels also was conducted within SRP's rights-of-way that could contribute to wildfires and create large volumes of smoke.
Within two days of the Memorial Day event, airborne Line Maintenance personnel identified more than 40 suspect areas, which were recorded with GPS coordinates, circuit names, pole numbers and pictures, and then entered into a database for review and to be prioritized for future action.
SRP's Line Maintenance department review team is comprised of the Line Engineering, Line Clearing and Line Asset Management departments. Each area was prioritized in order of importance based on transmission circuits/corridors and for the potential of the fuel area to burn. This list was then converted into a severity report dictated by the remaining wildfire season, and 26 locations were targeted for additional clearance with some locations containing one or more spans.
Along with the severity report, a strategic plan for mitigation and cost estimates were presented to SRP management for approval. One-time permission was then granted to exceed budgets, and the team immediately went about getting all necessary paperwork in order to gain access to any land involved that wasn't owned by the utility and to ensure all government guidelines were met.
CLEANUP AFTER THE FIRE
Once the discussions, negotiations and notifications had been completed, it was wildfire season again, so all vegetation management and removal crews had to be used in the most expeditious manner. First of all, SRP's line-clearance contractors were assigned to those areas where their equipment could be navigated with relative ease (approximately 40% of the identified work) to complete trimming, cutting and chipping in the most cost-effective way.
For areas such as river bottoms, washes and other desert terrain, bulldozers and other heavy equipment were used to simply knock down and pulverize specific vegetation-cum-fuel that would produce heavy smoke. Because bulldozers were most effective in clearing large tracts, SRP turned to its Water Operations and Maintenance department, which had vast experience with this type of work and equipment. After deft negotiations, the line crews had two bulldozers and a couple of all-terrain 4×4 extend-a-hoes for cleaning up the remaining 60% of the earmarked areas of heavy fuels for wildfires.
This large-scale project, triggered by the Memorial Day fire, took just under three months to complete and not another transmission line was lost during the remaining fire season to wildfires or from smoke-related faults. SRP was able to accomplish a complete clear-cut of right-of-way in areas determined to be most at risk from fire. Although the cost to complete the entire job was higher than expected, SRP considers it money well spent and will continue to protect one of its most valuable man-made assets: its high-voltage electric system.
Floyd Hardin is the manager of Line Asset Management for Salt River Project. Hardin is responsible for managing line maintenance project acceptance and compliance, infrared inspection and the right-of-way function for SRP. Hardin, who has been with SRP for 21 years, is also SRP's field liaison for wild land fire management issues. firstname.lastname@example.org
Karen Powell is the manager of Line Maintenance Services for Salt River Project and is responsible for line clearing/vegetation management for transmission and distribution lines. Powell has been with SRP for 25 years, and is also a member of the International Society of Arboriculture, Western International Society of Arboriculture and the Utility Arborist Association. email@example.com