NESC question (maybe?): Clearance for crossing utility lines

[charlie b]

My civil engineering colleague needs to know what the minimum clearance requirements are for a telecommunications ductbank crossing (i.e., above or below, at 90 degrees) a utility (in this case, water or sewer) line. This may be a matter for the local utility. But let me ask three questions:

1. Does anyone know if there is a specific requirement?
2. If so, and if the requirement comes from the NESC, then can you cite a reference article?
3. If the requirement comes from somewhere else, can you cite a reference from that source?

 

[mgookin]

There's a listing of TIA standards at http://en.wikipedia.org/wiki/Telecommunications_Industry_Association but I don't see anything that jumps out and says "this is it".

 

[mivey]

Not exactly specified for water/sewer although 12" parallel and 6" crossing is given in California. I would not use those distances without consulting with the other facility owner as there are too many potential problems.

320B
1. General
...as large as necessary to permit maintenance...without damage to the paralleling structures. A conduit that crosses over...separation sufficient to limit the likelihood of damage to either structure. These separations should be determined by the parties involved.

2. Supply and communications
3" concrete, 4" brick/masonry, 12" tamped earth, less is allowable by party agreement

3. Sewers, sanitary and storm
a. ...parallel to and directly over a sanitary or storm sewer, it may be done provided both parties are in agreement as to the method.
b. ...crosses a sewer, it shall be designed to have suitable support on each side of the sewer to limit the likelihood of transferring any direct load onto the sewer.

4. Water lines
...as is practical...to protect it from being undermined if the main breaks. Conduit that crosses over....to have suitable support on each side as required to limit the likelihood of transferring any direct loads onto the main.

5. Gas and other lines that transport flammable material
...not less than 12"...sufficient separation...to permit the use of pipe maintenance equipment.

6. Steam lines
...limit the likelihood of detrimental heat transfer...

Similar requirements in California GO128

41 Communications duct systems

41.4 Clearances and Depths
The clearance between duct systems of communication lines for public use and other underground structures independently installed shall be as great as practicable. The distance between the top covering of these lines and the surface under which they are constructed shall be sufficient to protect the system from injury by traffic.

A. From Foreign Substructures (Except Supply Systems)

(1) Independently Installed: Ducts carrying communication cables and conductors for public use, when independently installed, shall be separated where practicable from gas, water, oil, or other pipe systems, by a clearance of at least 12 inches when paralleling and by at least 6 inches when crossing.

(2) Concurrently Installed: Ducts carrying communication cables and conductors for public use, when concurrently installed with gas, water, oil, or other foreign substructures may be installed with less separation than required by Rule 41.4-A1 by mutual agreement of the parties involved