Original General Order 128

Section IV

Requirements For Communication 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-A(1) by mutual agreement of the parties involved.

B.    From Supply Systems 

(1)    Independently Installed: Ducts carrying communication cables and conductors for public use, when independently installed, shall be separated where practicable from supply duct systems and buried cables or conductors by not less than 3 inches of concrete, 4 inches of brick masonry, or 12 inches of earth.

(2)    Concurrently Installed: Ducts carrying communication cables and conductors for public use, when concurrently installed with supply duct systems, and with mutual agreement of the parties involved, may be installed with less separation than required in Rule 41.4-B(1) provided that the ducts of both systems are composed of rigid material. 

Where the ducts of either system are not of rigid material, or the supply cables or conductors are buried, the separations of Rule 41.4-B(1) apply. In lieu of this requirement, the provisions of Rule 43.3-B(1) for random separation may be applied. 

C.    Depths

Ducts carrying communication cables and conductors for public use shall be constructed at a depth to provide not less than 18 inches of cover below the surface under which they are located, except as otherwise provided in these rules.

(1)    Railroads: The top of communication system duct structures shall be located at a depth of not less than 30 inches, in the case of street railroads, and not less than 42 inches, in the case of other railroads, below the base of the lowest rail. 

Where these depths are impractical or for other reasons, they may be reduced by mutual agreement between the parties concerned. In no case, however, shall the top of the duct protection extend higher than the bottom of the ballast section which is subject to working or cleaning. Where physical conditions will permit, and suitable materials are used and the parties agree, a maximum of two ducts may be installed beneath railroad tracks without any form of protection at a minimum depth of 18 inches below the base of the lowest rail unless the worked ballast section of the roadbed exceeds 18 inches, in which case the ducts shall be laid below the ballast section. 

(2)    Thoroughfares: Communication duct systems in thoroughfares may be installed with not less than 18 inches of cover. Where it is not practicable to obtain such cover it may be reduced provided the duct material itself, or additional top protection installed, has sufficient strength to protect the system from injury by traffic. 

(3)    Sidewalks and Parkway Areas: Communication duct systems located in sidewalk areas may be installed immediately under, or included in the sidewalk material as an integral part of the construction. Systems located in parkway areas shall be installed with not less than 12 inches of top cover unless adequate top protection in addition to the duct material itself is provided. 

(4)    Private Property: Communication duct systems on private property shall be installed to provide not less than 12 inches of top cover. 

(5)    Open Ditches, Bridges, Trestles, Viaducts and Similar Structures: Communication duct systems, when supported by bridges, trestles, viaducts, or similar structures, shall be enclosed in the structure or otherwise protected from mechanical damage if the duct material itself does not inherently provide such protection. The design and interval of supports shall be such as to sustain, with a suitable margin of safety, the maximum load to which the supports will be subjected. Where necessary, provision shall be made for expansion, contraction or other movement of the duct system, or the bridge or other supporting structure.

D.    Maintaining Clearances And Depths 

(1)    Any person or agency performing surface or subsurface construction in the vicinity of communication duct systems is enjoined to maintain the minimum clearances from, and the depths of, existing systems as required by these rules.

(2)    If minimum clearances and depths cannot be maintained, then the person or agency causing changes is enjoined to notify the owner of the duct system.

(3)    Under the provisions of this rule a previously installed system may be maintained with less than the top cover required by other applicable rules of this section provided the duct material itself or additional top protection installed has sufficient strength to protect the system from injury by traffic.