Continuing Our Discussion on Trenching and Excavation— Water Accumulation in Trenches
Trenches are hazardous for a number of reasons. They are susceptible to cave-ins, oxygen depletion, hazardous atmospheres, water can accumulate, adjacent structures can become unstable and collapse, and existing utility lines can be struck. Previous columns discussed egress (April 2007), exposure to falling loads (June 2007), and hazardous atmospheres (October 2007). This month we discuss the OSHA excavation standards regarding water accumulation in trenches.
Protection from hazards associated with water accumulation is provided in 29 CFR 1926.651(h). Water accumulation is dealt with in 1926.651(h)(1) which states the following:
Employees shall not work in excavations in which there is accumulated water, or in excavations in which water is accumulating, unless adequate precautions have been taken to protect employees against the hazards posed by water accumulation. The precautions necessary to protect employees adequately vary with each situation, but could include special support or shield systems to protect from cave-ins, water removal to control the level of accumulating water, or use of a safety harness and lifeline.
Just how much water must be in the trench for this standard to apply? What steps must an employer follow to meet the requirements of the standard? The answers can be found in OSHA standard interpretations and many Occupational Safety and Health Review Commission cases.
When employers have questions regarding what can and cannot be done in specific situations, they can ask OSHA for interpretation of a specific standard. The National Utility Contractors Association asked, “Can workers enter a trench with water accumulation if the workers are protected from cave-in by shoring, shields, or sloping, and the water level is controlled?” OSHA answered yes to the question with the qualification that “the precautions necessary to comply with the standard vary with each situation, and the precautions you listed may not in all cases, provide the required employee protection.”
Two cases provide some instruction on the application of this standard. In Secretary of Labor v. North Texas Contracting, Inc., OSHRC Docket No. 05-0330 and Secretary of Labor v. J. B. Coxwell Contracting, Inc., OSHRC Docket No. 06-1228, we find similar facts. Both contractors allowed employees to work in trenches where water accumulated to less than six inches. The difference, however, was that one contractor attempted to remove the water while the other apparently “made no attempt” to remove the water.
The contractor in the North Texas Contracting decision argued that it was “impractical to use the pump on site to remove the water from the trench” because the contractor “did not know whether he could prime a pump in the amount of water accumulated in the bottom of the trench.” The Review Commission determined that by taking no action at all the contractor violated 1926.651(h)(1).
In the second case, J. B. Coxwell Contracting, a fire department officer allegedly observed employees working in a trench without any de-watering equipment in use. Water entered the trench when the contractor opened an existing storm drain, and the water level was high enough to cover the employees’ feet. Later that same day an OSHA compliance officer inspected the site and determined that the water depth was at a “no violation” accumulation. The compliance officer, however, based the citation on the fire department officer’s observations from earlier that day.
The contractor provided three measures to reduce water accumulation. These methods included installation of an underground sock drain, placing sand bags in active storm drains to prevent water from flowing into new sections, and installation of a three inch diaphragm pump to draw down the water table. These measures lowered the water from six inches in depth to a “no violation” accumulation in less than four hours.
The Review Commission held that OSHA failed to show that the dewatering systems were inadequate or that there was a hazard to employees posed by the water accumulation. The contractor’s quick action to employ de-watering measures apparently met the “adequate precaution” requirement in 1926.651(h)(1).
Additional precautions also need to be taken when “excavation work interrupts the natural drainage of surface water (such as streams).” The contractor, according to 1926.651(h)(3), must use “diversion ditches, dikes, or other suitable means […] to prevent surface water from entering the excavation and to provide adequate drainage of the area adjacent to the excavation.”
If dewatering equipment is used, 1926.651(h) (2) requires that “the water removal equipment and operations shall be monitored by a competent person to ensure proper operation.” In addition, 1926.651(h)(3) requires that excavations subject to runoff from heavy rains must be inspected by a competent person. The definition of a competent person is found on the OSHA website at http://www.osha.gov/SLTC/competentperson/index.html.
More information on trenching and excavation is provided on the OSHA website at http://www.osha.gov/SLTC/etools/construction/trenching/mainpage.html.