Rapid Tower Decommissioning

Hams with towers are growing old. Many young hams are content with simpler HF antennas that don't require a tower or a long term commitment. Lifestyles have changed over the decades. When a tower comes on the used market there is often little interest. Many are free for the taking, if you take them down. Few are willing.

What do you do when the ham passes away? Small towers can usually be taken down, and I've done that. They are then given away or sold by the estate. Home buyers prefer not to see a tower when shopping. Bigger towers are a greater challenge. The estate incurs the expense of professional removal, and that may be the only option. The cost can only be recovered if there's is a buyer once it is on the ground.

A friend (Dave VE3KG) has been helping the widow of a silent key (Ajmal Rahman ex-VA3ZQ, and formerly VE2ZQ and AP2ZQ) to dispose of his station. He had a dilemma: a 110' guyed tower that no one wanted. Without a buyer, it wasn't worth the trouble and expense to dismantle it. Due to the illness of the owner preceding his death, it was in a state of disrepair. 

I previously showed a picture of the tower on this blog, along with the antenna parts that had broken and fallen to the ground. At right is a full height picture taken this past summer.

I knew Ajmal a long time ago. When I dropped out of the hobby I did not stay in touch with many ham friends. The last time we spoke was at least 30 years ago. I visited his country home when his family was young and he was eager to build an effective HF station. The tower was raised soon after.

Following my inspection, I decided that the tower was safe to climb despite several issues. But to what purpose? There was little of value to salvage. A lightning strike several years previous had disabled the rotator and likely destroyed some or all of the cables. With fatigued elements having fallen to the ground, the antennas were little better than scrap. The house was being sold and the tower had to go. We decided it would have to be cut down.

That is easier said than done. There are many things that can go wrong in that seemingly simple operation. Risk of injuries to people and property should not burden the family. Despite the large size of the property there were several complications due to the property layout and guying. 

We considered options while waiting for a neighbour to drive over with his bush hog to clear the field around the tower. There was lots of time on our hands since he didn't show up until two months later. Luckily the house hadn't been sold in the interim.

The tower and property are annotated on this Google satellite view. The yellow dots are the approximate location of the guy anchors, the orange letters are hazards and the red arrows are the directions the tower is most likely to fall when the opposite anchor is severed. The gray circle is the approximate 120' fall radius (tower height plus mast and yagi measured on the ground from the pier pin base).

There are a few general concerns about felling a tower in this manner:

1. The fall radius is the minimum distance where debris will land. Tall towers can bounce. Their forward momentum can take them beyond the marked circle. Although that isn't likely for a tower of this size it must be taken into account.
2. Debris from the tower top can be dispersed well beyond the fall radius. Impact velocity and momentum are very high. Mast, antennas and other attachments can break off and take flight to damage property and injure unprotected people in the vicinity. Spectators must keep their distance.
   
3. Towers are most likely to fall in the direction opposite of the cut guy anchor. However they can fall in any direction in which the remaining guys are slack. That covers a lot of ground. Steps must be taken to ensure the tower falls where you want unless there are no hazards in the path of the tower or the two intact sets of guys.
   

We are now in a position to discuss the three fall directions and their hazards. 

The south anchor is inside the edge of the bush. Only a little vegetation had to be fought to access it. By dropping the tower to the north it would likely fall across the eastern edge of the lawn. That's undesirable but in this case was permitted. 

The problem is the northwest anchor and hazard C. I won't draw a diagram so you'll have to visualize  the scenario. C is a mature hardwood about 30' to 40' tall. When the tower topples forward the guys attached to the northwest anchor would wrap around the tree. That would severely injure or kill the tree. Worse, the tangling would cause the tower to veer left into the lawn and towards hazard E, the house. 

The first is very unwelcome and the second is unacceptable due to the risk of flying debris and lawn damage. I've seen the effects of a yagi striking a house when a 120' tower unexpectedly collapsed. It wasn't pretty.

The northwest anchor we just discussed has bushes growing all around but they were easily removed to reach the anchor. By cutting that anchor the tower would fall to the southeast. No matter how it falls there would be no risk of damage to anything of value. That sounds wonderful but for two things.

First, a tower falling into a forest typically will not reach the ground. A tower hanging overhead amid a tangle of broken tree limbs is not easily or safely removed. Neither is it easy to reach since the bush in front of the trees is dense and more than head height. I tried to get in there for a look and quickly decided it wasn't worth the trouble, both for the aforementioned problem and because of hazard D. That's the property line. We were told that it wasn't acceptable to fell the tower into the neighbour's patch of forest.

The northeast anchor was easily accessed once the bush hog levelled the field. The open field seemed an ideal landing area and the guys from the other anchors would easily cut through the light bushes on their west sides. Which brings us to hazards A and B.

Hazard A is utility pole supporting a transformer and hazard B is the distribution line and includes the telephone service cable. The fall radius comes almost exactly to the pole's guy anchor that stretches a short distance to the east (barely visible in the satellite photo). The distribution line at southwest corner of the property is 200' from the tower and well outside the fall radius. Potential debris set flying from the impact is at risk of hitting the anchor, pole or distribution line.

The red X marks the desired fall target.

"A ham's got to know his limitations"

It was at that point I recommended calling in the professionals. I was not comfortable taking on the job using a crew of hams who understood even less about the procedure than I did. I received good advice and an offer of tools from someone of my acquaintance in the commercial business in case I decided to take it on. 

He agreed with me that the best option was to cut the northeast anchor. When the anchor was cut, a rope tied to near the top of the tower has to be pulled hard within 2 seconds of separation to direct the tower to fall where we wanted. That's a precision operation. I considered the options and the procedure details and I decided it was outside of my comfort zone. Although I believed the chance of success would be very high, the cost of failure, low risk that it was, was too high to bear.

The firm I called on, Ontower, is very familiar to me and they are located a 30 minute drive from the site. The owner stopped by the site and agreed with the level of risk. A simple "cut and run" felling was out of the question. The recommended options were a crane to lay it down or bring a full crew to manage a precision fall to the target in the southwest area of the property. Cranes are expensive so we got the widow's approval to do the latter. Since the firm is fully insured, the risk of failure was covered.

Felling a tower

The appointed day was the Tuesday morning following the CQ WW SSB contest. It was a hectic weekend in which our team of 4 did pretty well. I'll have more to say about the contest in a future article. 

One of the multi-op team members, Dave VE3KG, was there with me. He knew Ajmal far better than I did and took the lead helping his widow dispose of the station. All the pictures and video in this article were taken by him. I was going to do it but after the first picture my phone battery went dead. I forgot to charge it.

The first job was to expose the guy anchors. All were galvanized angle stock, with two being ⅜" and the northeast anchor was about 3/16". One extended above grade, one was at grade and one was below grade. Use of angles is unconventional but perfectly fine if sized appropriately. What was very unusual was the use of shackles to tie the turnbuckles directly to the angle, spread onto the two faces of the steel. That's awkward. A header is preferred.

The picture gives you an idea of the anchor style since I don't have a picture of the northeast anchor that was cut. They dug deeper than I did during my inspection to expose over a foot of it. The gas powered cut off saw needed space to work. The safeties had to be cut since, for reasons unknown, they appeared to be tied into the (presumably) concrete anchor further down. 

All guys are often loosened before cutting the anchor. In this case they decided against it, using the tension of the other guys to start it falling in the approximately correct direction. The cut anchor and its guys recoil violently towards the tower when it is done this way. 

Click to view on YouTube

A rigger tied a rope about 80' up the tower. The other end extended to the southwest corner of the property. One of the two most experienced crew cut through the northeast anchor while the other maintained tension on the rope. The fall happens very quickly. 

Once the tower starts moving, the forward momentum becomes too high to direct the tower. There would have been less than 2 seconds to pull the tower while it was near vertical. That's why the person on the rope maintained tension throughout the cutting -- there was no time to communicate over the almost 100 meter distance at the moment the anchor was severed. The person on the rope can feel when the cut guys go slack and do what's necessary.

I'm sure many of you are expecting a video. We have one! Dave pulled out his phone and recorded the cutting and the fall. It's short and 95% of it is the cutting. The tower falls fast. We were of course told to stand well back. The falling tower hit the bullseye. It was a neat job. Professionals make it look easy. It isn't.

Salvage

With the tower on ground, our thoughts turned to salvage. The disposition of everything was not yet decided as I write this article. The crew separated all the sections while we inspected and disconnected the rotator and mast. The foreman brought the saw over to speed the work by cutting both steel and aluminum jammed into the ground. 

He then inspected every tower section and cut through one leg of the sections that were damaged. This is a smart way to discourage hams from the temptation to reuse them. An hour later they were done. They were on site for little more than 2 hours.

There are aluminum bars that can be reused, but the the guys are scrap other than, perhaps, the porcelain insulators. The short fibreglass rods that electrically decouple the tower from the EHS guys are old, likely damaged from the fall and partially delaminated. While tempting, they must not be reused.

The only prize I left with was a Tailtwister rotator. Although damaged by the fall it might be reparable. I can use it for parts if not. I'll open it up for inspection later this fall and if it looks interesting I'll write it up for the blog.