Construction site digging can be dangerous and risky, with many unseen hazards. A complete set of as-built utility drawings will not ensure lines, tunnels and other underground facilities are in the locations and at the depths shown on the drawings. Utility companies are aware of construction damage to lines and the risks of injury. Most locator services in the United States are centralized by the “811-Before You Dig” system to alleviate damage and risk during construction. In most jurisdictions, calling “811” before an excavation is the law.
Before the Dig
The most beneficial construction excavation activity, before mobilization and commencement of work, is walking the site. If there is an existing building on site, examine the foundation and exterior walls for any protruding wires, cables or pipes. Diligence is required in the observance of street and traffic lights, utility hole covers, hydrants, pavement patches, unbalanced concrete and disturbed soils as all can be indicators of subsurface utility lines and facilities. Soil discoloration can be indicative of an abandoned septic and other types of buried tanks.
The 811 System
The most important excavation construction service is the responsibility for the 811 call and arranging for the “mark out.” Each utility provider will come to mark the locations of buried lines or facilities, in their identifying color, within the excavation area designated by the contractor. The utility companies will also note if there are no lines or facilities within the area. If all utility providers respond to the mark out within 2-10 days, then, the clearance for the excavation is given. All designated utility providers must respond to the mark out within ten days and, if not, then it is the responsibility of the excavating contractor to reschedule through the 811 system.
Nothing is Linear
It cannot be assumed utility lines run straight. The mark outs set by the utility providers give a wide berth to both sides of a line. If excavation activities are near a mark out, or in an area of crossing lines, it is good practice to take the time and hand dig the area to expose the lines.
The excavation contractor is, most often, a subcontractor under the general contractor. During the process of awarding the excavation contracts, a reputable general contractor will inquire of experience, pre-qualifications and the safety records of the excavation contractor, and will rely heavily on the relationships between the excavator and the utility providers, departments of transportation and any other providers having subsurface lines and facilities at the site.
A successful, uneventful excavation depends upon the initial interactions of the excavation contractor and the utility service providers during the markup, and a respectful relationship will be a significant factor in awarding contracts.