APWA Recommendations
The American Public Works Association (APWA) is probably best known from it's recommendations on locate color standards. Actually, the APWA didn't come up with this color code- but rather adopted and publicized the Uniform Color Code from the American National Standards Institute (ANSI) standard Z53.1 Safety Colors. Color-coded surface marks (paint or a similar coating) should be used to indicate the locations, route and direction change of buried lines. Flags, colored stakes, whiskers or tape may also be used depending on terrain and the physical work site. To increase visibility, color-coded vertical markers (temporary stakes or flags) should supplement surface marks.
The APWA also encourages public agencies, utilities, contractors and all groups involved in ground excavation to incorporate its
standard system of subsurface facilities to prevent accidental damage, service interruption or injury. The APWA recommended
marking guidelines for underground utilities are:1. Utility lines will be indicated by markings using current APWA color codes. Markings should be 18"-24" in length and 2" in width.
2.The owner of the facility should be indicated by initials or by name in letters 6" high at the beginning and end of the locate. On long locates the facility owner should be indicated every 100'.
3. When known, the total number of lines within the ground will be indicated. The number of lines indicated should be based on the physical lines that you could place your hands on. Multiple lines twisted together to form a single facility, as in the case of electric lines, would be considered one cable for locate purposes.
4. If a facility is known to be present but the total number of lines for a facility cannot be determined, a corridor marker may be used. The corridor marker should indicate the approximate width of the facility. A marking resembling the letter "H" lying on its side will indicate the corridor marker.
5. When known, the size of the line being located will be indicated. Line size will indicate the outside diameter of the pipe or structure. A mark resembling the letter "H" lying on its side, bisected by a line extending along its length will indicate the oversized utility marking. The committee discussions centered on indicating sizes of single physical structures such as gas lines, sewer lines, water lines, and storm drains.
6. Duct structures, whether a single duct or multiple ducts, will be indicated by duct symbol indicating the approximate width of the duct structure. The duct marker will be indicated by a marking resembling a diamond bracketed by two parallel lines. The committee did not state whether indicating size should extend to indicating size of duct structure (telecommunications, electric) or indicating pair count for telephone lines.
7. When known, the pressure of a gas facility will be indicated. Gas pressure will be indicated as either low pressure, intermediate high pressure, or high pressure. The committee did not determine whether gas pressure would be indicated in instances of high pressure only or for all pressures. The committee did not determine whether the type of pipe should be indicated (plastic, steel, cast iron, etc.).
8. When known, termination points, dead ends, and stub outs should be indicated. The committee reviewed National Utility Locating Contractors Association (NULCA's) recommendations, which resembles the letter "T" with drop downs.
9. When there is a strong likelihood that marks may be destroyed, offsets should be used. Offsets are indicated on a permanent surface and are placed parallel to the running line of the facility. the offset should indicate the distance from the offset to the facility and should identify the facility owner and, if necessary, size of the facility.