[TowerTalk] tower replacement wisdom

[Dick Green WC1M]

I don't know about the zoning ordinance in your town, but our town's zoning ordinance and State law allow a grandfathered structure to be completely replaced, but the location and dimensions cannot be changed. If either location or dimensions are changed, even a little, a variance is required. And the requirements for obtaining a variance are quite strict under the town ordinance and State law. It's very unlikely that an application to move the anchors would meet the variance requirements in my town, especially since you can't demonstrate that it's impossible to rebuild in place. It isn't impossible -- it just costs you more downtime. Inconvenience and cost don't justify a variance in my town. And even if it were impossible, it's unlikely you would meet the other variance requirements in my town, like the spirit of the current ordinance has to be met (not the case with your oversized tower) and there has to be something unique about your property that's different from all other properties in the area such that there's no point in enforcing the ordinance or you can't make any use of the property at all without a variance (that's the "hardship" criterion, which trips up most variance applications.) Again, your ordinance may be different, but I believe a lot of ordinances have similar criteria regarding variances.

If you're lucky, your local zoning ordinance provides more flexibility for slight alterations to the location or dimensions when replacing a specially permitted structure. If not, then if limiting downtime means that much you could try to fight the variance requirement under PRB-1. There are lawyers who specialize in such litigation (e.g., K1VR.) Could be costly and could take a long time. I don't know for sure, but the presence of commercial antennas on your tower could throw a wrench in that strategy.

I would get a professional assessment of what to do. Perhaps you could safely move a set of guys to a temporary anchor (a large, heavy truck?) and dig up the anchor to inspect the condition or the rod and/or assess whether it would be possible to install a new anchor rod by drilling into the slab or some other means. If not, I would think you could remove the existing slab. I imagine there are machines that could lift it out, but it's probably more cost effective to break it into smaller pieces with a jack hammer and cut the rebar apart. That will disturb the ground, so you'll have to assess whether the hole needs to be made larger to compensate. If I was doing this, I'd get the opinions of a professional tower engineer. This approach would allow you to inspect and possibly replace the anchors one at a time, which would save downtime. But it requires some sort of *safe* temporary guy anchor and I don't know if that's possible. Again, professional advice is mandatory.

While it's conceivable you could inspect and/or replace each of the guy anchors without downtime, I don't see any way you can replace the tower and its slab without more downtime than if you were allowed to move the tower. But you may not need to remove the slab. Seeing that it's a pier-pin base, perhaps you could build up the slab by drilling holes in it to secure a small rebar cage with epoxy, then pour enough concrete on top to raise the level of the slab. However, I'd have a structural engineer check that idea. Even if it's safe, it might be easier and quicker to pull out the base and repour it.

73, Dick WC1M

-----Original Message-----
From: john at kk9a.com <john at kk9a.com> 
Sent: Friday, July 19, 2019 7:14 AM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] tower replacement wisdom

If you need more tower strength and still maintain the 18" face, Rohn 45GSR may be a good option. Without seeing it, I imagine that the tower pier pin concrete base is probably OK.  The guy anchors so most of the work so they should at least examined and new ones could be added while the existing tower is in place. With a crane and a lot of prep work you could swap in a new tower in a day. How visible is this location? I question if it is still a grandfathered structure if it is completely replaced.

John KK9A



[TowerTalk] tower replacement wisdom
Matthew Kaufman matthew at matthew.at


Hoping to gather some community wisdom before embarking on a tower replacement.

I have a 2.5 acre property on a slope with what I believe to be a Rohn 55 tower that was installed as a commercial paging transmitter tower in 1971 at 150 feet, then extended sometime in the 1980s to 170 feet when they switched from VHF to UHF and then 900 MHz paging. (The top (5th) guy level was quite clearly added using an existing hole on the anchor and a strandvise instead of the big grips that were used for the other guys.)

The tower has withstood at least one lightning strike, the 1989 Loma Prieta earthquake, and numerous storms,... but the guys are getting very rusted, the tower is rusting (despite a coating of zinc-rich paint a couple years ago), and the guy anchors are in unknown condition (though visually "ok").
I'm not sure how long a tower should last, but it can't possibly be "forever".

Two of the guy anchor locations are just above the tower elevation, the third is some tens of feet lower. Each guy anchor has a metal rod that extends 3+ feet unprotected through dirt and then into a concrete block .
The tower has a pier pin base on concrete which is below ground level, so is in a bit of a well with retaining blocks around it (had been buried under the earth when I acquired the property and tower).

I have the following limitations:
1. I want to have minimal downtime - the tower has a couple of heavily-used ham repeaters, a commercial repeater, and a wireless ISP on it.
2. The county would never issue a permit for a tower like this today... the property has a use permit for the tower, specified as "18 inch face" and a drawing of its approximate location on the property. So I need to somehow permit this work as "replacement in kind". A new tower would be limited to
53 feet in this zoning district, with a possible variance available to 78 feet... the trees are taller than that.
3. I have no construction drawings for the guy anchors or the tower base, and have no way of nondestructively testing the strength of the guy anchor rods.
4. I'd like to ensure that the tower can support the existing and future microwave dish loads, and reduce the twist both for those and the fire detection cameras I have up top... so maybe should go to star guying?

So... I need to choose a tower that is roughly 18" face width (possibly just Rohn 55 again), and install it at (if I trust the foundation) or near the existing tower location, with presumably new guy anchors that must be near but not at the existing anchor locations (to minimize downtime), and do as much of the removal and installation as possible with a crane (or helicopter?). I also need to not break the bank, as this is really a hobby tower for me, where the commercial customers are mostly to pay the utilities and property taxes.

Thoughts? Alternatives?

Matthew Kaufman, KA6SQG