Safety and load factors.

A. Selection of pipe class shall be predicated on the following criteria:(1) Safety factor: 1.5.(2) Load factor: 1.7.(3) Weight of soil: 120 pounds per cubic foot.(4) Wheel loading: 16,000 pounds.B. Utilizing the foregoing information, design shall be made as outlined in Chapter IX of the Water Pollution Control Federation Manual of Practice No. 9, latest edition, "Design and Construction of Sanitary and Storm Sewers," and the pipe shall have sufficient structural strength to support all loads to be placed on the pipe, with a safety factor as specified above.C. PVC pipe shall not be encased in concrete due to its different coefficient of linear thermal expansion.