Support Towers for High Voltage Transmission Lines - Expert 1

[rmcmort]

My company is assisting with the proposed refinancing of an apartment project in Colorado under the FHA-insured multifamily permanent debt program, and the environmental review identified a transmission tower for high voltage electrical wires located in close proximity to one of the five residential buildings that make up the site. HUD multifamily guidelines prohibit any residential structure within the easement for high voltage electrical wires, and further prohibit any residential structure within the engineered fall zone of such a transmission tower. (HUD multifamily guidelines differ from HUD single family guidance.) The energy company has been fairly cooperative and has confirmed the height of the tower - a steel framed lattice-work construction - at 85-feet, and the environmental third party report provider believes one of the residential buildings is outside the easement for the power lines, but within the fall zone of the tower. However, the energy company has not been able to identify the manufacturer of the particular support tower, and also have not been able to confirm whether there is an egineered fall zone for this type of tower and what the fall zone is. I would like to identify an expert on transmission towers who may be able to inspect the tower and opine on its condition, strength, anticipated useful life, engineered fall zone, etc., as well as the safety of these kinds of towers generally. Any suggestions on how to identify such an expert would be greatly appreciated.

 

[stevenal]

The tower owner should be able to provide engineering design specifications, but "fall zone" is generally not part of the specs.
thread608-252993

 

[stevenal]

http://portal.hud.gov/hudportal/HUD?src=/program_offices/housing/sfh/ref/sfh1-18f

Chapter 1
Appraisal and Property Requirements
Page 1-18f

The appraiser must indicate whether the dwelling or related property improvements is located within the easement serving a high-voltage transmission line, radio/TV transmission tower, cell phone tower, microwave relay dish or tower, or satellite dish (radio, TV cable, etc).


1) If the dwelling or related property improvement is located within such an easement, the DE Underwriter must obtain a letter from the owner or operator of the tower indicating that the dwelling and its related property improvements are not located within the tower?s (engineered) fall distance in order to waive this requirement.

2) If the dwelling and related property improvements are located outside the easement, the property is considered eligible and no further action is necessary. The appraiser, however, is instructed to note and comment on the effect on marketability resulting from the proximity to such site hazards and nuisances.

Seems fall distance is only a consideration within the easement.

 

[rterickson]

Good information in the previous thread posted by stevenal.

A couple of points to consider:

It is rare (in the US anyway) that a transmission line owner would permit permanent structures to be located in their easement (right-of-way). Potential liability, difficulty of maintenace, etc. The owning entity should be able to tell you what the boundaries of their easement are.

This bit about "engineered fall zone" sounds reasonable from a plain language standpoint I suppose, but it's not a standard part of transmission line design. It could be something that sounded clever to somebody at HUD when drafting the regs, but it's doubtful that the owner of the tower could now produce it after the fact.

You could engage a structural engineer with transmission structure expertise: There are many firms with this specialization, Google "transmission line engineer" for some leads. You won't get a quick answer, and it won't be inexpensive.

 

[cranky108]

Or you can pay the utility to underground the line.

 

[jghrist]

I agree with others that there is no such thing as an "engineered fall zone" as part of usual transmission line design. You could reasonably conclude, without further analysis, that the fall zone is the same as the height of the tower. If the wind blew the tower down, it could fall sideways as far as its height. If this is not sufficient, you could hire a structural engineer to analyze the tower to see where the failure point would be for transverse wind above the design wind load.

 

[Yjoshi]

I agree with my colegues, this documentation is not usually generated. An underground line is extremelly expensive so what I sugest is to contact any tower manufacturer and ask them to run a proper simulation (they will need the drawings but if you dont have them they can always go on site and create them from scratch (we have done this a coupple of times)). I believe that the actual “fall zone” Will be less than the tower height, however, because the line would be energized there are a lot of other things to worry about.
Usually tower manufacturers work with a software that will actually show you the deformation of the tower under different conditions