The Excavation Process

DOE-HDBK-1092-2004

11.7 THE EXCAVATION PROCESS

Once the planning is complete, the excavation process is ready to begin. Work control

procedures are in place, all hazards have been identified, hazards elimination/mitigation is

established and personal protection requirements have been determined and are understood by

all involved excavation personnel.

11.7.1 EXCAVATIONS IN CONCRETE WALLS AND SLABS

Excavations in concrete walls and slabs should be included in facility procedures. Drilling holes,

coring, chipping, or cutting holes in these areas is included. Most facilities require excavation

permits be issued for penetrations to a depth of 3 inches or greater in most concrete walls or

slabs. Some facilities, due to their design, will vary this depth reference.

The concern is encountering structural rebar or, worse yet, energized electrical power cables.

DOE sites have recorded many incidents of this type. The opportunity for this type of incident

seems to be higher when dealing with older facilities/buildings. Configuration management for

these commodities can be just as bad in newer buildings. Embedded commodities are often

omitted from as-built drawing requirements. Most installation drawings are diagrammatic, or

field routed commodity driven. This policy can provide significant problems in the years

following installation. It might be suggested to design and build future buildings, where electrical

conduits are only allowed to penetrate through, but not allowed to be encapsulated in the

concrete structure. Where this is impossible to accomplish, a red powder like dye should be

spread above the encapsulated conduit at the time of the concrete pour to warn future workers

of the hidden dangers below. A inside marker program combined with accurate as-built

drawings of embedded power cable conduits is investing in their electrical safety program.

One significant enhancement in the concrete excavation safety program has been the increased

use of electronic drill-stops. Used across the DOE Complex and in commercial/industrial

facilities, this safety instrument will interrupt power and stop the drilling process at first

encounter with a grounded metal object. Information on several of these types instruments can

be found at www.lorien.com and www.drillco.com.

The use of insulated rubber gloves is recommended for all workers drilling or cutting into

concrete walls and slabs, as an additional safety measure. Very few facilities have

configuration management of embedded power cables that would preclude their use.

11.7.2 MACHINE OR HAND DIGGING

Machine digging in earth requires careful consideration and a carefully defined "No-Dig Zone"

must be utilized. The identified depth of utilities is not accurate in many cases. Machine

operators, in general, do not appreciate the value of maintaining the integrity of energized power

cables. They rarely understand the purpose of the power feeds, so digging them up is not very

important to them. They are usually in a hurry to dig the trench and go to another job. A strong

safety program, with specific procedures, can make the difference between a successful

excavation and an incident or accident.

A significant number of facilities require identified utilities to be positively located by hand

digging to uncover them. That provides additional assurance of their location and depth of

burial. Many times, both dimensions are significantly different from those marked by locating

equipment. Special tools and personal protective equipment are often used to accomplish this.

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