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Thread: Cell tower fall zone examples

  1. #1
    Cyburbian Greenescapist's avatar
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    Cell tower fall zone examples

    What have you seen that's a reasonable and typical setback/fall zone for a cell tower?

    A community I'm working for has the provision that a cell tower must have the setback established in the zoning district it will lie in plus needs a fall zone that is equivilent to the height of the tower.

    Developers have pointed out the towers are designed to collapse in sections and therefore do not need extremely large fall zones or setbacks. While, I understand his argument, I'm not sure any adjacent landowner would agree.

    What's a reasonable fall zone/setback?

  2. #2
    Cyburbian Streck's avatar
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    I agree with the set-back being the height of the tower plus 10%.

    Having engineers "certify" that the tower will fall within a smaller "fall zone" is very questionable - isn't he the same engineer that designed the tower that fell? Engineers calculate, but buildings still collapse for all kinds of reasons.

    And what is his liability and responsibility to the city and third party injury if his design does fail or his "fall zone" is just wrong?

    The setback land does not go to waste. Many owners lease the open area for farm crops or livestock production purposes.

  3. #3
    Cyburbian Plus
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    From my coummunity's Z.O. -

    Evidence demonstrating that no existing tower or structure can accommodate applicant’s proposed antenna, either because there are no existing towers or structures meeting the applicant’s engineering requirements within the geographic area that the antenna is intended to serve, or if there are towers or structures in the geographic area, evidence that such structures do not have sufficient height or structural strength to meet the applicant’s engineering requirements. This section shall not be interpreted to mandate, but rather only to encourage co-location.


    In addition to all other limitations and provisions contained in the zoning code, any tower permitted with SU 15 approval shall be set back from any residential dwelling, property line of an undeveloped residential district or recorded residential subdivision a distance of two feet for each foot of height of the tower or 300 feet, whichever is greater.
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  4. #4
    Forums Administrator & Gallery Moderator NHPlanner's avatar
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    From my model ordinance in my 1997 thesis, which is also the standard we use in the community I work for (suburban town of 25,000):

    Setbacks: The GREATER distance by application of the following:

    1. Tower Height + 10 feet from street rights-of way or site boundaries

    2. 2 times the tower height from abutting residential property lines
    "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

  5. #5
    Super Moderator luckless pedestrian's avatar
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    in my town:

    The center of the base of any wireless communications tower must be set back a minimum of 105% of the tower height, or the required minimum setback of the district in which it is located, whichever is greater.

  6. #6
    Cyburbian btrage's avatar
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    I've always found fall zone requirements for cell towers to be a little silly. How many of these things actually fall over?

    I can understand places that are subject to intense winds like hurricane areas, but other places I just don't get it. These towers (especially monopoles) are designed to withstand some pretty substantial wind speeds.

  7. #7
    Forums Administrator & Gallery Moderator NHPlanner's avatar
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    Quote Originally posted by btrage View post
    I've always found fall zone requirements for cell towers to be a little silly. How many of these things actually fall over?

    I can understand places that are subject to intense winds like hurricane areas, but other places I just don't get it. These towers (especially monopoles) are designed to withstand some pretty substantial wind speeds.
    I agree that the fallzones are generally overdone, but politically, sometimes they're what's needed to get an ordinance passed and prevent a TCA challenge.
    "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

  8. #8
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    Our ordinance requires a setback of 125% the tower height. We also receive letters certifying that it will collaspe on its self. However, I asked a consultant had any fallen and did the collasping technology work. He gave me an answer that there are no records of them falling.

  9. #9
    Cyburbian Plan-it's avatar
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    Currently we use the height of the tower when adjacent to residential and regular setbacks vs commercial/office/industrial.
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  10. #10
    Cyburbian
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    Last summer, the community I was working in had a cell tower catch on fire when undergoing an antenna addition and the darn thing melted and fell over. Luckily, we had a fall zone condition in our zoning ordinance and everyone was safe. It was close to a high school and fell relatively close to the high school - in fact, most of it fell into the football field.

    In my experience, fall zones are a good thing!

  11. #11
    Cyburbian Streck's avatar
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    Data on tower falls:

    http://www.crrel.usace.army.mil/libr...tmos_Icing.pdf

    Data shows number of falls and page six shows fall radius to height.

    Apparently a lot of towers fall during ice or storms.

    One 1,000 foot tower in our state fell during routine maintenance replacement of tower parts/braces killing two.

    A separate youtube video shows a component being hoisted up and falling during construction of the tower killing seven workers. Caution: Late in the video replay shows two of the workers free falling after being thrown off the component as it comes down:

    http://www.youtube.com/watch?v=eqygUApfnZg

  12. #12
    Cyburbian Veloise's avatar
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    Being in the biz, I have a gallery of collapsed tower pics, mostly Katrina damage. Er, special circumstances. (They are at work, and I am not. Anyone wanna see?)

    Some ordinances apparently obtained their boilerplate from the caber toss at the highland games. Generally, if conditions are causing cell towers to fall, there are more issues going on than encroaching on adjacent parcels.

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    Calculations on the Mechanical Safety Area at Transmitter towers

    HTML code:
    http://www.reach.net/~scherer/p/twrmath.htm

  14. #14
    Cyburbian transguy's avatar
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    Quote Originally posted by Veloise View post
    Being in the biz, I have a gallery of collapsed tower pics, mostly Katrina damage. Er, special circumstances. (They are at work, and I am not. Anyone wanna see?)
    I wanna see!
    Much work remains to be done before we can announce our total failure to make any progress.

  15. #15
    Cyburbian Veloise's avatar
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    Katrina anniversary tribute


















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    Quote Originally posted by Streck View post
    Data on tower falls:

    http://www.crrel.usace.army.mil/libr...tmos_Icing.pdf

    Data shows number of falls and page six shows fall radius to height.

    Apparently a lot of towers fall during ice or storms.
    Is there any more recent data? Tower technology has supposedly improved since then.

  17. #17
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    How about NO Fall Zone Regulation?

    Here in balmy Costa Rica we recently were forced to adopt a TLC that opened up cell phone competition, among other services. The 40 year old state telephone monopoly was broken with the entrance of Claro (Carlos Slim) and Movistar (Spanish). The previous government monopoly was not inclined to share towers and thus we will have to endure over 10,000 new towers in this tiny mountainous country of 50,000 sq km. The regulations for putting up a tower were written apparently by the Claro and Movistar people as our supreme court ruled that cell towers can be placed ANYWHERE according to the economic and technical needs of the service providers and municipalities can make no regulations as to location. Nobody here has heard much about any possible heath risks, they are only interested in a Good Connection! Of course it would be in the interest of the service providers to squash or drown out any information of that nature.... and they do! But some folks have noticed that when a tower goes up near their home, the value comes down... as much as 80% for sales purposes, but NOT for tax assessment. There are monopole towers and box type and the required setback from any tower to the adjoining property is...... 10 feet! And altho liability insurance is required during the construction of the tower to cover the WORKERS! there is no requirement to insure against damage to adjacent properties. And once the tower is finished, NO insurance of any kind is required. When I brought this up to the Mayors office and City Council, I was labeled as a Doom and Gloomer even while waving the picture of the cell tower blown over in Chile and how it plastered two houses. And as we just had a 7.6 earthquake, there is not yet news of any towers falling... but then for a few pieces of silver, that news would not appear anywhere... we are waiting to see but at least there is very little cell service in the area affected and the complaints are about poor reception and coverage and nothing about structural problems. Common sense would dictate that the tower be located where, if it fell, it wouldn't be smashing any houses and if that were even remotely possible, then the government should require liability insurance to cover the potential area of fall... but no, a few dollars in "gifts" would be much cheaper than an insurance premium on 15,000 towers, many only 10 feet from the nearest house.... to say nothing of the coverage for any health risks. Why just three months ago, the Association of Cell Tower Equipment Providers assured us that there is no known radiation risk from any cell tower... and further the tower operators are the only ones that have measuring instruments for the radiation and further, the regulation says that if/when a government agency acquires these measuring devices, they must give 24 hour notice to the tower operator before making measurements... apparently so they can have the time to turn down the radiation, I presume. Thats how it is in the 3rd world, the transnationals rule. Maybe someday I will post pictures of rooftop mounted antennas, all 15 of them pointing to our largest hospital... from across the street... apparently so that on-duty nurses employees and doctors have Good Reception!

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