On May 8, 2017, a discharge of cloud-to-ground lightning struck an oak tree in the Pinal Mountains. It was a dying tree with smooth grey deadwood in its canopy and offered little resistance to a bolt of super-heated lightning that delivered 50,000 degrees F. of fire- starting power.
The smoke was spotted by a resident in nearby Six Shooter Canyon and an engine crew was dispatched from the Globe Ranger Station to check it out. They found the tree burning at 6,700 feet on a steep, east-facing slope high above Pioneer Pass.
A few days later, a photo of the tree’s charred shell was posted on Tonto National Forest’s Facebook page. You could almost smell the smoke lingering at its base. It was the origin of the Pinal Fire.
This past winter, fire management officers, and other specialists at the Globe Ranger District and the five other districts on the Tonto National Forest, identified specific areas in the forest where the ecosystem would benefit from a naturally-caused wildfire. One of these planning areas was a north-facing swath of the Pinal Mountains that had not seen fire in over 60 years.
With the successfully managed outcome of getting positive fire treatments on last year’s Juniper Fire in the Sierra Anchas, and working with the latest fire research from the Rocky Mountain Research Station, they agreed on a forest-wide strategic plan to manage these areas should a wildfire every occur.
The plan included input from community leaders, elected officials, and stakeholders, as well as wildlife and recreation specialists.
When lightning struck on May 8 in the heart of the Pinals planning area, fire managers looked at the ambient conditions, availability of firefighting resources, the relatively early time of year, the wet winter, the fuels condition and state of the timber, and decided they had a high probability of success.
After being reviewed all the way up the U.S. Forest Service chain of command, the supervisor of the Tonto National Forest approved the use of the plan for the Pinal Fire, and it was quickly put into action.
Managed as a low intensity fire
By May 10, the ensuing fire was still under an acre in size. About .10” of rain had fallen the day of the lightning strike at the district’s remote automatic weather station (RAWS) and there were reports that about a third of an inch of rain fell in the fire area during the following two days, including a small accumulation of snow.
The previous winter had been good to the Pinals, with quite a bit of snow accumulation in the higher elevations. The gradual snow melt allowed moisture to percolate deep into the soil. This favored the larger ponderosa pines, firs, and other conifers that were more deeply rooted, and helped to increase their fuel moisture content so they become literally too wet to burn.
The fuel moisture in the interior chaparral vegetation that includes scrub oaks and manzanita (what firefighters call “brush,”) at lower elevations also had a relatively high moisture content and was unavailable to burn.
But grasses and leaf litter on the surface dry out more quickly, and because no significant rain had fallen since March, the low intensity fire slowly consumed layers of dead pine needles and oak leaves as it crept across the forest floor, effectively “cleaning up” decades of accumulation.
Fire Management Office Jack Marvin was aware that the size and complexity of the fire would steadily increase over time. As of May 11, he had 4 crews and 4 engines on the fire, a total of 104 personnel in all, but he knew he had to stay ahead of it. He completed a complexity analysis, and the result pointed to the need for a Type 3 Incident Management Team.
The National Incident Command System is broken down into five different levels. A Type 5 Incident Management Team is at the lowest level of expertise and complexity, and a Type 1 is the highest. These teams are coordinated and dispatched from each Geographical Area Coordination Center (there are ten within the U.S.). For Arizona, New Mexico, and west Texas, it’s the Southwest Coordination Center (SWCC) in Albuquerque.
Type 3 Incident Management Team arrives
Incident Commander Andy Mandell and his Type 3 team took control of the fire at 6 AM on May 12. The fire had grown, but was still under 5 acres. Andy’s team hit the ground running, and less than 36 hours later, four more engines had arrived, with an additional 50 firefighters and a Type 3 helicopter. By the end of the day on May 14, a total of 200 firefighters were on the Pinal Fire.
As the fire increased in size and began to move further into the higher elevations towards Pinal Peak and Signal Peak, a structure protection group from the Type 3 team began working on the high ridge of the mountain to protect the 13 summer cabins and 32 communication towers.
Dozers made road improvements, crews removed “ladder fuels” (various size small and intermediate size trees that can carry fire into the canopy of larger trees), burned old thinning piles, placed water hoses around cabins and distributed portable tanks that would be filled from water tenders if needed. A helispot was set up in an open area near Pinal Peak.
Smoke was increasingly visible from Globe, particularly when an isolated tree would torch, but the fire continued to burn with low intensity through the pine and conifer understory of leaf litter, grasses, and small shrubs according to plan.
With the homes and communication towers at the top of the mountain prepped and protected, firefighters actively began bringing the fire down off the slope towards the north. As it backed down the mountain, they added fire to keep it even, ultimately trying to burn through the understory plants of the remaining 2800 acres of conifers.
As Andy Mandell explained at a community meeting, “We want to make sure that the fire does what we want it to do, which is keep it a low intensity fire.”
Weather is hotter, winds are higher
Conditions were changing rapidly as summer conditions approached. They felt they still had a few more days to move the fire through the remaining timber areas and stop it at the brush before the brush was available to burn.
Firefighters keep track of the potential burnability of live vegetation by determining the percentage fuel moisture. They collect and weigh a freshly collecting sample and then weigh it again after it has been dried in a special oven. This process used to take 24 hours, but with new technology, it can now be done in twenty minutes flat.
But fuel moisture alone doesn’t tell the whole story. Ambient weather conditions, seasonality, green-up, and other factors can directly or indirectly affect a plant’s ability to burn. So firefighters take it one step further and plug all of this data into a software program that generates something called the ERC, the Energy Release Component.
As of May 21, the brush vegetation (manzanita and scrub oak are the plants typically sampled) had a relatively low ERC, which meant it was still unavailable to burn.
But that didn’t last for long.
The fire reaches a pivotal point
As wind and temperatures continued to rise on May 23, the fire made its first runs into the brush. Around 6 PM, a few pockets of half an acre to an acre were burning. An hour later, a sustained run of fire into the brush actively involved 75 -100 acres. Globe residents watched this unfold when they saw a thick plume of dark smoke suddenly rise up from the fire.
Technically speaking, brush is really interior chaparral, a vegetation type composed of numerous different evergreen species, but mostly dominated by mazanita, scrub oak, silktassel, and holly-leaf buckthorn. It is a true, fire-adapted plant community and benefits from being burned every 50 – 100 years. After a fire, it begins to recover almost as quickly as it burns.
In as little as two weeks, new shoots and leaves will emerge from the bases of the burned plants, even during the hottest and driest part of the year. The plants regrow so vigorously that within 10 years, it can look as if a fire never happened.
But when this brush vegetation is available to burn, the complexity of a fire changes. It can burn fiercely and unpredictably, and its change in status was a pivotal point in managing the Pinal fire.
A new team with more horsepower
After completing another complexity analysis, and considering fire duration, resources on the scene, anticipated fire behavior and expected weather, there was no question that a Type 1 Incident Management Team, the highest level of the National Incident Command System, needed to be brought in.
Jack Marvin and the Type 3 team managers wanted to hold the fire in check and keep it from growing by using water and fire retardant until the Type 1 Incident Management Team was in place, so they called in for aerial reinforcements.
By the next day, the sky was full of planes and helicopters. A huge, twin-prop Chinook helicopter was delivering water to the fire with a 2,000-gallon “Bambi bucket” that dangled from a 100-foot-long cable. An insect-like Sky Crane helicopter was busy hauling water back and forth inside a fixed tank that fit neatly inside a cut-out portion of its fuselage. Both were dipping their water from Blue Lake at the nearby Solitude Tailings.
I saw a fixed-wing air tanker drop bright pink retardant in the early afternoon and a half hour later, watched a much larger load dropped from a DC-10 jet aircraft.
This DC-10 is called a VLAT (Very Large Air Tanker) and is one of a fleet of three that have been converted into “slurry bombers.” Each of them have 11,600 gallon tanks fitted to their bellies with computer-controlled bomb bay doors. They can drop either multiple, partial loads or empty an entire tank of retardant in a 50-foot wide band, three-quarters of a mile long.
Ahead of any air tanker is a lead plane that guides it into the drop zone. Before any retardant is dropped, the two planes make at least one dry run over the area, called a “show me” run, and then circle around for the real deal. This time, when the lead plane goes in, it creates a line of smoke called a “pop smoke” that hangs in the air long enough to show the air tanker exactly where to drop its load. It’s dramatic to watch, with tankers flying as low as 200 feet above the tree tops.
Aerially applied fire retardant is not used to put a fire out, but rather to slow the growth of a fire by coating vegetation to make it more resistant to burning, thereby “buying time” for firefighters to work. Water can be used for the same purpose, but timing is more important because its effects don’t last as long as the retardant.
Circling high above all this aerial activity at about 10,000 feet is Air Attack. This plane is staffed by a pilot and an air tactical group supervisor who are the eyes and ears of the “The Stack,” the name given to the layers of air tankers, lead planes, and helicopters flying in the airspace below. It also helps crews on the ground with situational awareness about what’s happening above their heads.
When the Type 1 Incident Management Team officially took over on the morning of May 25, the fire was at 4100 acres. Bea Day, the new Incident Commander, confirmed that the fuel moisture of the brush had dropped precipitously in the past few days, making it available to burn. This meant they had lost the ability to use the brush to limit the spread of the low intensity fire that was burning in the timber area.
Firefighters make their stand at containment roads
They didn’t think they could hold the fire at mid-slope, so they chose the existing road system as defined in the fire planning area to make their stand. This was “the box,” as Jack Marvin called it, a 9,000-acre area contained by Forest Service roads 651, 55, and 112 roads on the west, north, and east, and a combination of hand and dozer containment lines and an old burn near the ridge on the south side.
They planned to “finesse the fire” (Bea Day’s words) off the slopes with low intensity down to these control roads without causing a crown fire that could roar through the brush with a large wall of flame and “slick off” the entire slope.
Carl Schwope, Operations Section Chief for the Type 1 team, described to a group of community members how severely and unpredictably this kind of vegetation can burn: “The brush (chaparral) fuel type is difficult because you can look up there and it looks like it’s doing nothing, just some smoldering, maybe a few smokes, then all of a sudden it catches the right wind current, stands up, and once it’s established, it’s going to burn until it loses the fuel or wind.”
It was because of the possibility of the fire making a serious run through the brush vegetation and jumping the control line roads to the north that a pre-evacuation order was issued for residents of Kellner and Ice House Canyons on May 24.
If the time came, residents would have, at most, 3 hours to evacuate. Sheriff’s deputies were ready to notify everyone door-to-door. Residents who signed up with Gila County Emergency Management’s Everbridge program would receive notice from that system.
As of May 25, there were 400 firefighters on the fire working day and night shifts, 24 hours a day, but it was too dangerous to put any of them on the fire front because of the rough terrain and volatile fuels.
There had been gusty winds all week, and on May 26, wind speeds were expected to be 30mph from the southwest during the day. There was some heavy fire that pushed down a main ridge west of Kellner Canyon and generated a lot of smoke, but it remained within the control line (the FS 651 road). Most of the fire activity was on the north side, the side closest to town.
Crews began working with residents in Ice House and Kellner canyons with structure triage and preparation to create defensible space in case the fire made it that far. They cut brush and removed burnable debris around houses and structures.
On May 27, the far south side of the fire near Signal Peak was looking good, with less and less smoke every day. They wanted to take advantage of the weather in the next few days and begin to bring the fire down to the containment roads, so they began doing “burnout” operations between the fire and the roads, with more smoke as a result.
Fighting fire with fire
By burning fuel on the inside of the containment lines, they gained more control of the spread and intensity of the fire by eliminating fuel to burn. In firefighter parlance, this fuel-free area is called a black line—if it’s black, it won’t burn.
Firefighters on the ground add fire to the landscape with drip torches, a contraption filled with a mixture of gasoline and diesel fuel.
But when there is a need to burn out an area that is either inaccessible or too dangerous for firefighters to enter, they use a helicopter and a special machine that dispenses little balls of fire.
They look like ping pong balls, but are specially coated inside with potassium permanganate, a chemical that, by itself, is not flammable. After they’re loaded into a hopper, the machine injects a few drops of ethylene glycol into each one just before it rolls the sphere down a chute and out of the helicopter. In 3 – 5 seconds the two chemicals react and the ping pong ball bursts into flames and burns for about 30 second, spreading fire like a Molotov cocktail wherever it lands.
Over the next few days, firefighter numbers increased to 641. Crews worked to burn out additional areas, often having to wait for the winds to shift direction so that the fire would move where they wanted it to.
Swirling erratic winds contributed to a spot fire on May 29 that jumped the FS 55 containment road on the north side, but with the support of helicopters and air tankers, firefighters held the fire to only 3 acres.
These same winds continued to hamper efforts throughout the day, but firefighters were still able to burn from both the east and the west sides of the fire and join in the middle on the north end. Burning out this area was important to shore up the containment on the side of the fire closest to homes and property in the canyons to the north—a major milestone.
While burnout operations were critically important to contain the fire, fire managers still tried to leave strategic buffers of live vegetation in drainages to minimize post-fire effects in the future.
The next day, on May 30, pre-evacuation notifications were lifted and the focus shifted from burning operations to holding and improving the established line.
With the fire 80% contained, Barry Johnson’s Type 3 Incident Command Team took over command of the fire on June 2 and brought containment up to 95%. It was handed back to the Globe Ranger District eleven days later.
But the effects of the fire are not over yet.
Mitigating post-fire effects
With the first monsoon rains on their way, the focus has steadily shifted from smoke and fire to the potential for flooding resulting from the fire’s disruption of the watershed.
The BAER team (Burned Area Emergency Response) has been steadily working throughout the month of June to clear drainages, improve road drainage to enhance down stream flow, and replace damaged or under-sized culverts under the forest roads.
They aerially mulched 1,125 burned acres with straw to decrease erosion and received funding to create “storm patrols” which will monitor roads after the monsoons start to keep the culverts clean and remove sediment and debris from the road system.
They will also start creating drainage improvements and erosion protection for the 13 miles of trails within the Pinal Fire area.
To mitigate storm damage further downstream in Russel Gulch, Ice House, Six Shooter, and Kellner canyons, Gila County has secured a grant to hire local contractors to help homeowners clear debris from their properties that might impede storm water flow. But first, each homeowner must sign an agreement to grant permission to allow these contractors to work on their property.
At this writing, the Pioneer Pass road (FS 112) and the Pinal Peak r (FS 651) are open but the Forest Service plans to close them for safety reasons when the monsoon rains start. The trail system in the burned area of the Pinals is scheduled to remain closed until October.
Kim Stone was a horticulturist, writer, and editor of several publications for the University of Arizona at Boyce Thompson Arboretum over the better part of three decades. He is now happily self-absorbed in freelance writing, travel, and content marketing.