I have never understood why some contractors use aluminum hydraulic shoring regularly and others do not. Those who do use it have found that it is not only the quickest and simplest way to safely shore a trench, but also one that saves time and money while still meeting OSHA requirements. I can only think that those who say they don’t like the shoring after using it once or twice have simply not taken the time to learn how to get the most out of it.

A trench box may seem to be a lot easier to use since all you have to do is assemble it, place it in the trench and then drag it along as the trench progresses. However, problems can and do arise with that scenario — namely, when there are crossing utilities in the way, the work area is restricted (e.g., an alley between buildings), digging must take place inside a building, utilities in the trench walls have to be supported so that they do not shift or the equipment on hand isn’t big enough to handle a heavy trench shield. When face to face with those situations, some contractors might be tempted to let employees work in an unprotected area of the trench. That is never the proper response. Ask anyone who has experienced a trench fatality or been issued a hefty (tens of thousands of dollars) OSHA penalty and they will tell you it is not worth it.

Aluminum hydraulic shoring — which is designed to prevent cave-ins in all but the most unstable soil conditions — may very well be the answer to many situations that contractors frequently encounter.

Readily available from many manufacturers and rental operations, it is suitable for many applications such as spot bracing for repairs, laying house utility service connections and for production trenching. It can also be used in conjunction with trench shields to protect areas between trench shields and where shields cannot be installed.
There are two types of aluminum hydraulic shoring system — vertical shores and horizontal waler systems.

Vertical Shores

Vertical shores, which are the most common, are constructed of two side rails that are connected together by one or two, sometimes three or four aluminum hydraulic cylinders and are placed in the trench vertically. Vertical shores with one cylinder are referred to as single shores and they are especially useful for spot-bracing, in excavations with limited room to work or to brace trench walls above and below crossing utilities. Double and triple shores have two or three cylinders, respectively. End shores are also available when needed to close off the ends of a trench. When used in production trenches the shores can be leapfrogged as the trench progresses. Typically, vertical shores are used in trenches up to 12-ft wide, and may be stacked for varying depths (20 to 25 ft depending on manufacturer).

In stable soils, such as Type A and B soils, vertical shoring may be used directly against the trench face as long as loose material (local raveling) is not falling from the face. In Type C soils and when local raveling is prevalent, 3/4-in., 14-ply arctic white birch plywood (known as finform or McFinn Form) or 1 1/8-in. plywood is placed between the shore rail and the trench wall.

The average vertical shore is generally installed or removed by one or two people, and best of all, it can be installed and removed from the top of the trench without anyone having to enter the trench — thereby eliminating worker exposure to a cave-in during setup and take-down.

Before installation the Competent Person or worker should refer to the manufacturer’s specifications known as tabulated data to determine the maximum spacing of the vertical shores. The spacing will vary based on the soil type and the depth of the trench. The horizontal spacing between shores will generally be between 4 and 8 ft. Never exceed the allowable spacing.

The installation process is quick and easy. You connect the hydraulic hose from the pump bucket to the quick-connect coupling on the shore. Tilt the shore up and slide it into the trench. Then pump up the hydraulic pressure in the shore so that the gauge points to the green zone (750 to 1,500 psi).

The shore is now installed. Use the release tool to disconnect the hose coupling from the fitting and move on to install the next shore.

The removal process is just as quick and easy as the installation: Grab the handle on top of the shore rail on the opposite side of the trench with the shoring tool (T-handle hook) and use the removal tool (same as the release tool) to release the pressure in the shore until it slides down onto the hook on the removal tool. Use the tools to collapse and lift the shore from the trench. Walk backwards while pulling the shore out of the trench.

Horizontal Waler Systems

Horizontal waler systems are placed horizontally in the trench to support a variety of sheeting materials such as finform, fiberglass or steel. While they are ideal for less stable soil conditions, they can be used in any type of soil condition within the boundary of the manufacturer’s specifications (tabulated data). When installed, the system forms a box similar to a trench box.

NUCA-approved Safety Instructor Greg Strudwick (right foreground) demonstrates how to safely install aluminum hydraulic shoring.

Most horizontal waler systems are made up of two rails of various sizes and two cylinders. These systems are designed to allow maximum protection, coupled with the versatility and flexibility needed to work around crossing utility lines, for repairs and production work. Some systems are equipped with the cylinders inside or protected by steel, which is designed to allow end-loading in three- or four-sided applications. When there is a crossing utility, skip shoring can be set up to permit the utility to pass through the protected area.

Generally the waler system is installed and removed with the help of an excavator or backhoe. A loader backhoe can handle most waler systems and in many cases even a mini excavator could handle the load. Smaller waler systems can be installed by a couple of workers.

Similar to the vertical shoring system, the Competent Person should refer to the manufacturer’s tabulated data to determine the vertical spacing between the walers as they are placed down in the trench. In most cases the vertical spacing requirement is 4 ft or less.

The installation process is a bit more involved. A four-point harness is attached to the four lifting rings on the walers and is attached to the excavator or backhoe. Finform, wood or other approved sheeting is inserted into the trench and rested against both trench walls. The waler is lifted with the equipment and placed inside the trench. (Always shore from the top down.) Then the hydraulic system is pumped up until the gauge on the pump is in the green zone. The next waler is installed in a similar way except it will have to be collapsed to fit inside the upper waler before being lowered into place. The release tool is used to disconnect the coupling from the shore and the next waler is set in place. After all walers are in place and the trench is safe to enter, the harness is removed.

Note: Some manufacturers suggest placing one waler system on top of another, connecting the harness to the bottom waler and then lifting them together and lowering them into place. When the top waler is in place pressurize it and then drop the lower waler(s) into place and pressurize it, thereby following the safety procedure of shoring from the top down. Always follow the manufacturer’s recommendations.

The removal process: Attach the harness to the waler that is to be removed and attach it to the equipment. Use the release tool to reach down and release the pressure from the cylinders by pressing on the end of the quick-connect male coupling. Fluid will flow out of the coupling and the waler will be suspended. Lift the waler out of the trench. All shoring should be removed from the bottom up, which means it will be necessary to collapse the waler so that it can be brought up through the upper walers. After all walers have been removed, the sheeting can be removed and the trench filled in.

Note: Some manufacturers suggest attaching the harness to the bottom waler and bringing it up to the upper waler(s). Attach the harness to the equipment, release the pressure in the lower waler and lift it until it makes contact with the next waler. Release the pressure and remove the walers together. Always follow manufacturer’s recommendations.

Hand Pumps

Aluminum hydraulic shoring systems include a hand pump consisting of a 5-gal or plastic pump can. There are two types of hydraulic shoring fluid that may be used — standard (summer) grade, which is typically a 1-quart container of concentrated fluid that is added to 5 gal of clean water or anti-freeze (winter) grade, which is used when temperatures are expected to go below freezing (32 degrees Fahrenheit). Mixtures vary based on the temperature and manufacturer; therefore the competent person should refer to the instructions on the container.

Only hydraulic shoring fluid should be used because it is biodegradable and will not damage the seals in the shoring. There is a way to recover the fluid if desired; check with the manufacturer. Never substitute hydraulic oil or diesel fuel for hydraulic shoring fluid because they will not work and may damage the shoring cylinder seals.

Competent Person

Several times I have mentioned the role of the Competent Person (CP). Every excavation or trenching jobsite must have a CP onsite during the installation and removal of shoring equipment to direct the processes and control or eliminate the hazards. That means the CP must be knowledgeable about the potential hazards and how to use whatever type of shoring or shield system is in use. He or she must also be capable of reading and understanding the manufacturer’s tabulated data, which must be available at the jobsite.

Although OSHA has included charts in the Excavation Standard — Subpart P the CP should not rely on these charts because they actually apply to one manufacturer’s system. Always obtain a copy of the tables and charts (tabulated data) from the equipment manufacturer or rental company that supplies the shoring. It will provide more detailed information about the specific shoring system that you are using.

While in my opinion there is no one type of protective system (shoring, shielding or sloping) that will work in all situations, there is one (or more) that will work in a specific situation. It is the employer’s responsibility to see that the best system for the job is used in order to ensure the safety of those expected to work in the trench. What aluminum hydraulic shoring offers contractors and municipalities is another viable option for providing each and every worker who must enter into a trench pit or small excavation with a safe place to work. As long as these systems are installed properly and workers remain inside the protective system (shoring), the worker will be safe from a cave-in.

George Kennedy is NUCA Vice President of Safety.