7.14 Utility Locating, Colorado 811 Damage Prevention, the APWA Color Code & New Construction Inspection

Before the shovel goes in the ground

WPI lists "perform underground locating, marking, and notification" and "inspect new construction" as distribution job tasks, and the Wastewater Collection outline lists "determine location of underground utilities." In Colorado this is statutory, not merely good practice.

Colorado 811 and the Underground Damage Prevention Safety Commission

Colorado's excavation notification law is codified at C.R.S. Title 9, Article 1.5. Its core requirements:

• Every excavator must notify Colorado 811 (the Utility Notification Center of Colorado) before excavating. This applies to homeowners and utilities alike; there is no exemption for a utility digging in its own street.
• Notice must be given at least two business days before excavation, not counting the day of notice, weekends, or legal holidays. A ticket has a defined life and must be renewed if work extends beyond it.
• Excavators must pre-mark the proposed excavation area in white paint, flags, or stakes so locators know where to look.
• Facility owners and operators must locate and mark their facilities within the notice period, or notify the excavator that they have no facilities in the area.
• Colorado requires facility owners to have their underground facilities mapped, and the 2018 legislation created the Underground Damage Prevention Safety Commission to enforce and adjudicate damage-prevention violations.
• Damage must be reported. Contact with a facility, even without an immediate leak or outage, must be reported to the owner and, for hazardous facilities, to emergency services.

The APWA uniform color code

Memorize this table; it appears on exams and it prevents fatalities.

Note the two that matter most to a water operator: blue for potable and purple for reclaimed. The purple convention is the same one used for reuse piping, valve boxes, and signage, and it exists so that no one ever mistakes a non-potable line for a drinking water line.

Tolerance zone and safe excavation

Locate marks are not survey-accurate. Colorado, like most states, defines a tolerance zone extending a specified horizontal distance on each side of the marked centerline — commonly 18 inches — within which mechanical excavation is prohibited. Inside the tolerance zone, excavation must be by hand digging or vacuum (hydro or air) excavation until the facility is exposed.

Additional field rules:

• Maintain the marks. If they are destroyed by weather or traffic, request a re-mark rather than guessing.
• Expose and verify the facility before crossing it with machinery.
• Support exposed lines rather than letting them span an open trench.
• Stop and call when you find an unmarked facility, and when marks and field conditions disagree.
• Abandoned lines are still a hazard, and unmarked private facilities beyond the meter are common. Private locating services exist for that reason.

Locating equipment

• Electromagnetic pipe and cable locators consist of a transmitter that induces or directly connects a signal onto a conductive line and a receiver that traces it. Direct connection is the most accurate method; inductive clamping is next; broadcast induction is least accurate and most prone to coupling onto adjacent utilities.
• Tracer wire is installed with non-conductive pipe — PVC, HDPE — precisely because those materials cannot be located electromagnetically. A broken or unterminated tracer wire makes a plastic main effectively invisible, so tracer wire continuity testing is part of new construction acceptance.
• Ground penetrating radar locates non-conductive lines and voids where soil conditions permit; it performs poorly in wet clay.
• Acoustic pipe locators and metal detectors for valve boxes and curb boxes.
• Sondes pushed or floated into a non-metallic line for point location.

Inspecting new construction

Accepting a developer's or contractor's work makes it the utility's permanent liability, so inspection is an operator function with real consequences. Items verified against the utility's standard specification:

1. Materials. Correct pipe class, fittings, valves, hydrants, and gaskets, with certifications, and confirmation that all wetted materials are lead free and certified to NSF/ANSI 61 and 372.
2. Trench and bedding. Depth below the frost line, correct bedding material and compaction, no rocks against the pipe, and proper haunching.
3. Separation from sewer. Water mains are kept a minimum 10 feet horizontally from sanitary sewers and, at crossings, at least 18 inches above with joints located as far as practical from the crossing.
4. Thrust restraint. Thrust blocks bearing against undisturbed soil, or restrained joints per the design, at all bends, tees, plugs, and hydrants.
5. Tracer wire installed continuously with plastic pipe and tested for continuity, and marker tape placed above the pipe.
6. Valves and hydrants set plumb, boxes centered and to grade, hydrant drainage pockets built with clean rock.
7. Pressure and leakage testing to the specification.
8. Disinfection under AWWA C651 with satisfactory bacteriological samples before the main is placed in service.
9. As-built documentation and GIS update at closeout.

An operator who signs off on construction without verifying separation from sewer, thrust restraint, disinfection results, and tracer wire continuity has accepted problems the utility will pay for over the next fifty years.