ASCE Manual of Practice No. 118 For Belowground Pipeline Networks For Utility Cables

U-Tech: Underground Technology Cutting Edge Technical Information for Utility Construction and Rehabilitation
By Dr. Lawrence M. Slavin, Dr. Oleh Kinash, Dr. Mohammad Najafi | January 2010 Vol. 65 No. 1
Figure 2 Typical Underground Conduit Construction (Courtesy of Underground Devices, Inc.)

There are basically three modes of construction for “outside plant” facilities for communications and electric power supply lines. These include:

1. Aerial/overhead plant in which the cables are individually suspended between utility poles placed on the order of 100 - 300 feet apart;
2. Belowground plant consisting of an array of parallel conduit paths, typically four to 6-inch diameter pipe, spanning the distance between relatively large manholes, separated by distances on the order of 500 to 1,000 feet; and
3. Belowground plant installed by directly burying the cables within the soil, including cable along a road, highway or street, or service drops to the home.

All three modes have been commonly used in the industry, with an increasing amount of belowground facilities being placed relative to aerial plant in more recent decades, primarily driven by regulations. Due to the significantly different characteristics of the two belowground methods, mode two has been specifically designated as “underground (conduit) plant” to distinguish this method from mode three comprising individual “direct-buried” cables. Although the terminology suggests that there is a clear distinction between the mode two (underground conduit system) and mode three (direct-buried cables) methods of construction, in practice there have been variations in each category that tend to blur the differences.

In support of belowground installations, including the encouragement of innovative designs and methods for enhancing the deployment and utilization of such pipelines, the American Society of Civil Engineers (ASCE) has recently published the ASCE Manuals and Reports on Engineering Practice No. 118 for Belowground Pipeline Networks for Utility Cables -- commonly referred to as “MOP No. 118”, as shown in Figure 1. The effort was sponsored by the U.S. Department of Transportation and the FHWA Turner-Fairbank Highway Research Center.

mopFig1.jpg
Figure 1 ASCE Manual of Practice No. 118
(Reprinted with permission from ASCE)