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Thread: Large fall zones for wireless towers: are they necessary?

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    Cyburbia Administrator Dan's avatar
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    Large fall zones for wireless towers: are they necessary?

    Many zoning codes establish large fall zones for wireless towers and monopoles; e.g. equal to the height to three times the height of the tower. However, I've seldom seen fall zone requirements for similar monopole structures such as high tension transmission line towers, signs, billboards, and the like. I've also only heard of a few cases where monopoles have collapsed.

    Large fall zones seem like a waste of land, especially when a community is trying to increase development density. Are huge fall zones really necessary for wireless towers? Are there alternatives?
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    Forums Administrator & Gallery Moderator NHPlanner's avatar
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    I agree that fall zones are not generally "needed" from a technology standpoint, but often they are politically the only effective way to get community buy-in to a regulatory framework (particularly when in or around residential areas).

    I imagine that this attitude/perception will change as time goes on...and I think we're starting to get to the point where some communities will be able to transition away from them.
    "Growth is inevitable and desirable, but destruction of community character is not. The question is not whether your part of the world is going to change. The question is how." -- Edward T. McMahon, The Conservation Fund

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    Cyburbian
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    Fall zones for transmission lines are normally covered in the width of the easement that it is placed within. Power companies that I have dwelt with ensure that the easement is sufficiently wide to be a clear zone also.

    I have worked with fall zones for oil derricks in residential areas in the past. I designed a relatively affluent neighborhood in Southern California that was built on an oil field and had several pumps still operating around the homes. A fall zone of 150 feet was established because derricks sometimes had to be re-erected to deepen the wells.

    Regarding the wireless tower industry, I believe that the overly large clear zones have more to do with the paranoia that people still have about electromagnetic transmissions being theoretically linked to brain cancer than the highly remote chance that a tower will fall. If a tower was to fall, my guess is the cataclysmic event that caused the tower to fall would create much more destruction of the immediate area than the tower itself. I believe that the wireless industry just agrees to the wider fall zones as a way of placating the paranoids regarding the supposed cancer issues.

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    Cyburbian
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    Quote Originally posted by smccutchan1 View post
    Regarding the wireless tower industry, I believe that the overly large clear zones have more to do with the paranoia that people still have about electromagnetic transmissions being theoretically linked to brain cancer than the highly remote chance that a tower will fall. If a tower was to fall, my guess is the cataclysmic event that caused the tower to fall would create much more destruction of the immediate area than the tower itself. I believe that the wireless industry just agrees to the wider fall zones as a way of placating the paranoids regarding the supposed cancer issues.
    I completely agree and even had this discussion at my last place of employment with the Board of Commissioners in an attempt to get them to remove such stipulations. That attempt failed.

    If it is constructed within the buildable area of a lot the setbacks should be no different than of a structure allowed in that zoning district, i.e. a single-family house in a low density zoning district. The argument often given for such large "fall areas" is it makes the "ugly" tower seem further away from other uses, or the fall area could be landscaped in a way that would soften the visual impact.

    I do believe that as technologies change the tower structure that we all know will be a relic of the past. We already have small 2x2 cubes that are being erected on the sides of buildings and existing utility structures that can transmit secured wireless networks and if I'm not mistaken it has the potential transmit, receive and pass cell signals as well.

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    Cyburbian Cardinal's avatar
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    I dealt with this issue perhaps 7-8 years ago. The type of tower really makes the difference. Most modern structures are designed to collapse within themselves rather than drop as a single pole, to its whole length. We had an engineer provide data to support smaller setback requirements. Unfortunately I never kept any of the information.
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    Cyburbian solarstar's avatar
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    We have the applicant provide us an engineered report stating what the fall zone should be. It's always much smaller than our code would usually allow, but at least is based on some engineering (and is generally about 1/4 of the tower height which would be more of a collapse area).

  7. #7
    Cyburbian
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    Our approach to fall zone regulation is quite irrational. Do we have a fall zone for trees? No, but every year where I live people's trees fall on their own or their neighbor's home and do substantial damage.

    One consideration should be what is on top of the structure. In the case of cell phone towers, the top isn't as dangerous as a wind turbine that might be still spinning perhaps, or an electric line that probably will still be live when it touches the ground.

    As others have said, I think the current practice comes down to political acceptability.

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