Engineering a Miracle - The Story of WEEDS

(published in The San Diego Reader, April 29, 2004)

Engineering a Miracle
by Joseph W. Mitchell
Copyright 2004, all rights reserved.

“I dreamed that we had a fountain on our roof,” she said. “We’d just push this button and out would come this spray of water, pssssssht, far up into the air and all over the house.”

We both laughed at the idea. We were acclimating to the Southern California weather after relocating from the cool dampness of northern Europe, and were experiencing the punishing heat of August to October. Ramona is a hot place, and for some reason our home’s little microclimate is a bit hotter still. We’ve seen 100o in February, and had highs in the 100’s for a week straight. Our local record is 117o. It was not surprising that my wife, Diane Conklin, would dream of cool fountains. Having one on the roof, well, that was a bit odd.

We knew that we were moving into fire country. Joe, the builder and the former resident of our house, was forthright about the fires that had raged through the area. He’d taken precautions, though. Our house was built on a large pad that he’d planned to be “large enough for a fire truck to turn around in”. He’d done some clearing. We were concerned about the rows of eucalyptus surrounding the house. I’d seen an Australian documentary in which people described how eucs would explode during a fire. Some of ours were within 30 feet of the house. “If you’re worried about that, cut ‘em down,” Joe the builder told us.

Our house overlooks thousands of acres of Coastal Range wildland. Staring at this everyday, particularly during the arid heat of late summer and autumn, Diane began to plan for fire. We were strangers to Southern California, and needed to know what we were up against. She called the California Department of Forestry (CDF), and Fire Captain Ron Serabia was kind enough to come out to our place to assess our fire risk. We are perched on a ridge between the oak-lined canyon of Mussey Grade Road and the deeper, rocky Kimball Valley. Looking across the valley to the wall facing us, Serabia told us that it held a 30 year load – 30 years since the last fire. Load to a fire professional means fuel, which in this region of California means life itself. That which grows here burns. Fire in the California backcountry is an inevitability. Thirty years of fuel meant that when something happened, it was going to be big. He recommended more clearing. Diane asked about whether we should cut down our eucalyptus. Serabia didn’t think so.

Over time, we cleared the land. We are sensitive to the need to clear with care so that the environment we chose to live in is not destroyed by our choice to be here. What is known in some circles as brush-clearing is known in others as habitat loss. We moved out into nature to enjoy it, not to destroy it. But here is the bitter fact about living in natural places: you must kill nature in order to live in it.

After some heated arguments about what to clear, we came to the following compromise: I would go around the borders of our land and mark what was to be kept. The rest would be cleared. Chamise is the most common chaparral plant in our area, and also the most flammable. For this reason it is also called greasewood. It had to go. We thinned the sumac, the scrub oak, and coastal sage Artemisia californica. We kept our stand of mountain mahogany, our ceanothus (the native lilac), and monkey-flower. We paid particular attention to eliminating fire-ladders: paths by which flames could climb from bush to tree limb to crown.

In February of 2002 fires ravaged the town of Fallbrook, north of San Diego. Forty-two homes were lost. A friend videotaped the news coverage. We repeatedly watched film shot from a news helicopter of houses burning on a ridge very much like ours. Some things were odd. There did not seem to be much of a difference between the homes that were lost and the homes that were saved. Not only that, we noticed that the houses burned while the trees next to them – including eucalyptus – did not. Only the houses burned. Diane drove to Fallbrook, and talked to some of the neighbors. She learned that some houses were saved because of the extraordinary efforts of firefighters and those who stayed behind to fight the fire themselves.

We also learned from another video, a tape released by the CDF dealing with home protection in wildfire-prone areas. In addition to clearing, which creates what in their lingo is known as “defensible space”, they recommended other measures, such as blocking vents during a fire, and boxing in eaves. Embers, it was claimed, would creep up into the eaves and start a fire. They also recommended tacking a sprinkler on the roof if there was time to do so.

We made a list of the tapes suggestions and laid out our plan. We would box in our eaves, put a door over our attic vent, and put a sprayer on the roof. We were going to get our fountain on the roof, after all. Diane arranged with Lars Mitchell (no relation), a local contractor, to mount one up there. Well, I thought, it wouldn’t cost all that much. But then, thinking about it, I realized it wouldn’t work.

San Diego county had recently been ravaged by two fires: the Viejas and the Fallbrook fires. In each, the fire had been driven by the Santa Ana winds, which had whipped the flames forward at up to 40 to 50 miles per hour. With winds like that, any spray from a sprinkler on the roof would simply be blown off of the roof and downwind. Likewise, any under-the-eaves conventional sprinkler system would simply have its water splashed up against the house over a much smaller area than it would in the absence of wind. I told Diane my belief that sprayers would not work in realistic conditions. “Fine,” she said, “then you figure out what to put up there!”

I consulted with Art Bale, a recently retired CDF fire captain in our neighborhood, and we had a couple of long and very productive talks about wildfires and how and when structures burn. He affirmed one key point, which if anything should be the main point of this article: most structures that burn in wildfires burn during high wind conditions. Some are caught in the rolling firestorms - whole areas that spontaneously combust. There is not much hope for any structure caught in one of those. However, many homes are burned by flying embers. The structure is showered with burning embers, and it only takes one to land in a combustible spot. Then, fanned by the wind, it starts its own fire within the house and the house is consumed.

We had cleared. We had defensible space. Our house, despite being a ridge home, was in fact sited quite well. Joe the builder had put the house and pad on top of a large granite outcrop, which would help to deflect away the hot air and flames rising from the floor of the valley below us. Yet our house was all wood, and it would only take one stray ember to burn it down. Embers have been seen to burn homes up to half a mile from the fire front under the proper wind conditions. Our chaparral is considerably closer than that.

Embers, though, are easy to put out, and they can only burn dry materials. I thought we were safe on direct flame and heat, so long as our trees did not burn. All we would have to do is find a way to protect the house from embers, and we’d have made a big move towards defending our home.

So how to wet down a house in a hard wind? The answer is simple: spray water into the wind and let it blow back on the structure. I ran it by Art the fire captain, and he thought it would work: Install water jets directed outwards under the eaves, and activate this spray as a fire approaches. The winds will blow the spray back onto the house on the side that the embers are arriving from. And what if there is no wind? Well, then it doesn’t work – but on the other hand if there is no wind, where are the embers going to come from?

I explained the concept to Lars the contractor, and had him build a small prototype, with a variety of sprinkler head spacings. Lars found a variety of irrigation nozzles to try. The ridge on which our home sits is one of the windiest places that I’ve encountered in San Diego, and it wasn’t long before nature provided a realistic situation for me to test the concept. Lars found some very nice adjustable 45 degree irrigation sprayers. I found that at around 1 gallon per minute per nozzle and a 45 degree spray, if the nozzles were around eight feet apart I’d get complete surface coverage in a 20 to 30 m.p.h. wind. Adjustability is important, since one wants to balance the spray from all of the nozzles as well as to adjust for the structure’s geometry. I investigated nozzles used in fire systems, but these require too high of a water flow rate. They are designed for fire suppression, whereas our system is only designed to extinguish incoming embers. Putting out a fire requires a lot of water. Putting out a match – even a lot of matches – does not.

Now the idea was that in a fire situation, we’d turn on our system, get in the car, drive away and let the house defend itself. But wait: where is the water going to come from? We already had a pressurized system and small storage tank to counter the inadequate water pressure we had from our city water line. We called Steve Grasilli of Ramona Pump and Supply, our plumbing contractor, and asked him for a 5000 gallon tank and a much more robust pump to handle the needs of our fire system. He installed a two horsepower Flint & Walling pump and the water tank.

Meanwhile, Lars and his colleague Andy set about installing our under-the-eaves sprinkler system and boxing in the eaves in one operation. The system consisted of two main lines of copper pipe going up the side of the house to the roof, then converting to 1” PVC piping under the eaves. Our roof structure is complex, and there were a couple of branch points in each line. The sprayers, as stated, were eight feet apart. After installation, Lars and Andy adjusted each sprinkler head individually to get an even spray around the house. Each sprinkler head protrudes from 1 to 3” out from beneath the eaves, so that the blow-back spray will cover the roof. When we first tested it I marveled that it actually worked, and in a strong breeze the house siding became thoroughly wet, as would the roof and under the now-blocked eaves. At full spray, the full system puts out something less than 30 gallons of water per minute. That would give our tank a lifetime of three to four hours before our water supply would be exhausted. I couldn’t help wondering, though, if the whole thing was a little stupid.

We had the system in place while the Pines Fire ravaged the back country near Julian in 2002. We were still very nervous. Our sprinkler system had an Achilles heel, and we knew it. In an emergency, the power company would typically cut the electricity so that live power lines would not be falling to the ground in a fire, making a dire situation slightly more dire. No electricity, no pump – and no pump, no sprayers. Our system would only work up to the point that the power was cut and after that the house would last only up to the point where the desiccating wind sucked up the last ounce of water from the most vulnerable spot. Hopefully, the fire would have passed through by that time, but that was trusting in hope a little too much for our tastes.

For this year’s fire season, we decided that we’d put in a backup generator to close this last chink in the armor. Pumps are needy at start up, and need to draw a peak current of up to five times what they need during continuous operation. Off-the-shelf generators were not quite sufficient for our heavy pump, so in order to be safe we went with a small home propane-fueled backup generator from Generac. We began the purchase in the summer. We decided that we’d permit it properly, and that process lasted for several weeks. Reinhard Brennheis of Rhino Power, our generator dealer and installer, had a family emergency that called him back to Austria for a few weeks. The dry heat of late summer and early autumn took their toll on the landscape, and When Reinhard finally returned, and got the permit approved by San Diego County, he began installation of the generator the week of October 21. It was an intensely hot week, and he suffered in the 100 degree temperatures. By Friday, October 24, it was finished, and the county inspector approved it on the first pass.

“I’ll give it a good test this weekend,” I told Reinhard, “and let you know how it goes.”

Over and over again we had tried to envision what it would be like. Perhaps the fire would start over the ridge, near the Barona Casino, rise above the hills and dip into Kimball Valley, to finally come roaring up the canyon wall. We live on what is known in fire-fighting parlance as a “chimney” - a funnel-shaped gouge that cuts into the canyon wall. At one side of the funnel live Joseph and Marcia. At its apex live Shawn and Holly, who rent the modular home there. On the other side, perched on our boulder, is our house. Our driveway skirts the edge of the funnel before intersecting Kimball Valley Road – our escape route. In a fire, the flames would shoot up the chimney, sealing off our escape if we dallied too long.

“Don’t expect CDF to help you,” warned Art, the former fire-captain. We didn’t. We’d butted heads with CDF on safety issues before. Diane is a local activist, and we’d highlighted the dangers of packing more density into our heavily forested, single escape route neighborhood. The CDF bureaucracy had been less than helpful.

We live near the end of a heavily wooded box canyon, a couple of miles from where the old stagecoach road dives into San Vicente reservoir. When, on occasion, we’d meet a fire official, and told him where we lived, we’d get an odd look. There would be a slight roll of the eyes, or shake of the head, or a softening of gaze. Nothing would be said, but the message was quite clear: Man, you don’t know what you are in for. But they were wrong. We did know. We’d seen it, in our nightmares, in our dark imaginings.

On Saturday I tested the system. After running for about five minutes or so, the Generac began to backfire slightly. I’d have to call Reinhard about this on Monday, I thought. Diane had been out, and arrived back at around 6:30 p.m. She called me out onto the driveway to look at a thin column of smoke out in the distance, to the northeast. Santa Ana winds were predicted to start soon. This was not good. “Where are the bombers?,” she asked.

The fire burned as so many had before. The potential for a Santa Ana, though, had us on edge. Nevertheless, it was far away. I went to sleep at 10 p.m.. Diane said she would join me shortly.

The phone rang at midnight when 911 returned Diane’s call. The winds had whipped up at 11 p.m., and the fire had begun to move. San Diego Country Estates, a development east of Ramona, was being evacuated. Almost 10,000 people live in the Country Estates. We drove out there to assess the situation, and as we approached the occasional car became a continuous line of traffic. The entire development was being evacuated. Never in our five years of residence had we seen a full-scale evacuation. We turned around before we became stuck in the traffic. I was getting nervous. The wind was blowing in from the northeast. After Country Estates, we’d be next.

We arrived back home to find Kimball valley filled with dark smoke. For me, this was the most frightening moment. Fire and flame I could deal with, so long as I could see how far off it was, judge its position and speed, estimate the risks. Hidden behind the dark veil of smoke, there was a hidden threat, a threat which could engulf us at a moment’s notice, or perhaps not for many hours. Fortunately the wind shifted a short time later, affording us a clear view of the approaching conflagration.

I began to pack the cars. Diane began to telephone, and to join me in packing as well. We had a little time. We could judge what things were worth keeping, and what could easily be replaced. We worked like clockwork, and even the dog was calm.

At Diane’s suggestion, we began operating the system intermittently, wetting the house while city water was still flowing. We took the furniture off the porch, removed the propane tank from the grill, put out ladders, disabled the propane tank line to the house and the garage door opener, shut the attic door and made sure all doors and windows were closed. To the east, the fire raced along the horizon, past Barona reservation, down to Muth Valley and beyond.

We thought that the firefighters would try to hold the line at Wildcat Canyon Road, and at Barona Casino, to the east of the ridge above Kimball Valley. If that line failed, there would be nothing to protect us. We saw the flames rise on the ridge behind Barona, and descend. After that there was only a red glow. Then, flames appeared on the ridge between us and Barona. The fire was coming.

On the far rim of Kimball Valley, the flames rose 100 feet into the air. I watched the fire devils spiral and dance on the ridge, a ridge not unlike our own. We both saw this, and knew that our preparations were paltry in comparison with this immense force of nature. Thirty miles of flame stretched before us, and marched towards us. It was terrible and beautiful at the same time. All of the gorgeous life surrounding us was being consumed, and in its final moment was burning with a brightness and poignancy that confounded us with wonder. Our house was doomed, that was obvious, and suddenly was a small matter indeed. All that we knew was being burned away. We finished packing, finished final phone calls. The fire was 1/3 down into our valley, and we thought it would be much faster coming up than going down. At 4 a.m. it was time for us to leave our world behind. We turned on the sprayers, left them hissing into the wind they had been designed for, and left.

Over an hour or so later, we sat in the local Denny’s. Diane teared up for a minute. “Joe,” she said, “it’s gone. It burned.” I hoped not, but knew that my hopes were probably futile. Still, we were both glad we had done all the things that we did. We’d taken every step we could to give our house a fighting chance. And, if by some odd chance a firefighter had been brave or foolhardy enough to try to save our home, he or she would have a better chance of survival at our house than at any other place in the vicinity. I wondered how our house had met its end. Probably the damned lattice work on the balcony, I thought... the sprayers hadn’t quite reached that far. Or, perhaps the eucalyptus had torched, had fallen on the house or onto the propane tank. I wondered how much time all of our preparations had bought it. In the hour before dawn, the house had fought a desperate and valiant battle, and had fallen.

We retreated to the home of some friends of ours. They live above the Ramona airport, and from here we could see that there were only two small bombers flying against what was rapidly becoming a historically large fire. We learned its name now – Cedar. One horizon was a sold wall of smoke from one side to the other, and now behind us, the Paradise fire had begun to burn Valley Center. In my mind I tried to model the motion of the fire fronts. Too large to handle without an army of firefighters, it would race forward along the winds, a flying wedge pushing itself to the west. It would then slowly expand upon all fronts as the winds shifted or stilled, and the wedge become a block. Firefighters could protect small areas, but for the most part the fire would spread at the natural progression rate for fire in bone-dry chaparral. The lines would grow until all the fuel was consumed. The fuel was San Diego County. I asked our friend, an engineer, if I was missing something, if I was just being paranoid. “What is there that will stop it?” I asked him. He just shook his head with a haunted look. “I don’t know.”

Rather than be chased from place to place, rather than live in constant fear of entrapment, I talked Diane into going to where there was no fuel. Skirting the edges of the fire, we traveled off to the desert.

The Borrego Valley Inn was a most accommodating find, even though the power to the town had been cut. It was a peaceful place to come to grips with our shock and loss. The desert air was cool and the sky clear and blue while the Santa Anas still blew. Two other couples staying at the Inn had put the pieces together the same way we had, and had fled to where the fires could not come. All of us believed we’d lost our homes.

A fire line represents many things, among them a news barrier. To get news out from where the fire has burned one has to cross a fire line, a dangerous prospect. Ramona disappeared from the news reports, was replaced by Scripps Ranch and Tierrasanta. Fire lines surrounded it on three sides, and only one road out remained open. In Borrego Springs, cell phone reception was spotty, and land lines non-existent. For two days we all tried to make contact with those who’d gone back into the fire zones. We wanted to know about our friends and neighbors. What was sad, to us, was not so much the loss of the house, since we’d done all we could and it could be replaced, but the loss of our beautiful green surroundings, our oak-canopied road, and our close-knit neighborhood.

Late on the second day, there was a frantic knock on our door. Gordon, our new friend and fellow refugee was out there with his wife’s cell phone. “Joe,” he said, “you’ve got a house. It’s still standing.” I choked up.

A friend of one of the guests had gone into our neighborhood to check on our house. He told us that it was standing. The generator was still running, and the 5000 gallon tank was empty. The roses around the house were still blooming. No other houses were standing nearby. It was “like the moon.” It would turn out that all of our little group in the Inn would go back to standing houses.

It was Thursday before the roads were safe enough to end-run the fire and get back to our homes. Our house was standing, as were our tall eucalyptus, some with wilted leaves, but many others fully green. Not so our neighborhood. Not one adjacent neighbor had their home standing, and the little Fernbrook neighborhood below us had been badly damaged. Many of our friends had lost their homes. None had lost their lives. People had managed to get out. There had been no fire trucks, no bombers, no help for us. Our neighborhood had been sacrificed. Many homes were spared through sheer bravery of the occupants and neighbors. A 70 year old friend of ours with a heart condition, working with his teenage son, had managed to save his house. I can scarcely imagine what would have happened had they been trapped on their hill. I didn’t know whether to hug him or to whup him upside the head.

Isn’t it better to have a home that can fight for itself? Bravery is one thing, common sense another. Most fire officials say to leave, that the house is not worth your life. Yet, it is human nature to try to save what is ours. Is it possible that our idea offers a compromise?


Now that it had been vindicated, it needed a name. After struggling a bit I came up with WEEDS: Wind-Enabled Ember Dousing System. Its not a very nice name, but it will have to do. Got chaparral? Get WEEDS!

As a physicist, I know that one uncontrolled event does not make a rule. It could have been one of our other protection measures that had been more responsible for saving us: our defensible space, our sealed eaves, our good siting, or just good luck. Driving around our neighborhood and town, one can see many “miracle” houses, not just ours. Talking to our neighbors, though, and seeing what got saved and what did not leads me to believe that our sprayer system was critical to saving our home. One family, for instance, having lived through fire before, was fanatical about clearing, would not so much plant a shrub or tree in the acres around their home. They were in a valley, not on a ridge as we are. Yet their home burned. Another neighbor fought the blaze around his home for as long as he could, and seemed to be winning. Then the fire roared up from a rock wall, perhaps 200 to 300 feet away and upwind, and suddenly his home was showered with “thousands of burning cigarettes and matches”. He had run out of water. His home soon burned.

No conventional sprayer system is designed to work in high wind conditions, and this is when most homes are lost in a wildland fire. WEEDS is designed for high wind conditions, to actually use the wind to protect the home by distributing the spray over the surfaces the embers are most likely to fall upon. Embers are small, and not hard to extinguish. The light spray and wetting provided by a WEEDS should be sufficient to do this. It is possible to build an ember-proof house. Unfortunately, we do not live in one. I think that our WEEDS system covered this final gap and saved our home.

We are grateful to Joe the builder, who sited the house so well, built it solidly, gave us ice plant and a large pad. Lars Mitchell helped turn the idea for WEEDS into a prototype and then into a working system. His and Andy’s fine carpentry finally protected our eaves and attic vent. Steve Grasilli the plumber provided the tank and Flint & Walling water pump, a pump which apparently ran dry for two days before being turned off, and which still works just fine. Reinhard Brennheis and Guardian/Generac sealed the final gap in our system and made it self-sufficient.

Still, good fortune played a roll. Our generator was not in place and working until the day before the fire. There are gaps in spray coverage that I know well: the lattice work on our porch which I should get around to fixing some day. Our upper attic vents, too, are too high to have closable doors. Our house could have burned, and for two days we had little hope that it hadn’t.

How many homes burned needlessly? Against a raging firestorm there is little that can be done. Such a force is currently beyond human control. Fire is capricious – we don’t know which way the winds will blow, or where the fire-devils will dance. Yet many homes burned not because they were in the direct path of a firestorm, and took direct flame, but because they were ignited by embers. These can – and should be – saved. To help, I am placing the WEEDS concept into the public domain. There have been too many tragedies, and too many have lost their homes and possessions. To compound this tragedy, we can now foresee the drive to remove all brush – all habitat – from the human domain, to scrape, pave and Round-Up from sea to desert. WEEDS may offer a compromise, a way that we can continue to live with a nature that burns.