Excavation Work Control Measures

1. PURPOSE

This procedure defines the control mechanisms and precautions to be taken to ensure personnel safety and to prevent the damaging of underground services during digging or excavation activities.

2. SCOPE

2.1      This procedure applies to all Air Product facilities and to work being done or supervised by Company  personnel at customer sites.

3. DEFINITIONS

• Adjacent Structure Stability refers to the stability of the foundation(s) of adjacent structures whose location may create surcharges (forces or loads, which could be vertical or lateral), changes in soil conditions, or other disruptions that have the potential to extend into the failure zone of the excavation or trench.
• Company Representative can be either an employee of Company , a subsidiary of Company , an owner or a designee of a joint venture partner who will be assigned on a project basis. The representative will be defined in the project specific documentation.
• Benching (Benching System) means a method of protecting employees from cave-ins by excavating the sides of an excavation to form one or a series of horizontal levels or steps, usually with vertical or near-vertical surfaces between levels.
• Competent Person is an individual who has the necessary experience, knowledge and appropriate qualifications (if required), and is capable of identifying existing and predictable hazards or working conditions that are hazardous, unsanitary, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate or control these hazards and conditions.
• Excavation. An Excavation is any man-made cut, cavity, trench, ground penetration or depression in an earth surface that is formed by earth removal. A ground penetration includes the driving of stakes or rods (such as earthing or grounding rods) into the ground. A Trench is a narrow excavation (in relation to its length) made below the surface of the ground. In general, the depth of a trench is greater than its width, and the width (measured at the bottom) is not greater than 4.6 m (15 ft). If a form or other structure installed or constructed in an excavation reduces the distance between the form and the side of the excavation to 4.6 m (15 ft) or less (measured at the bottom of the excavation), the excavation is also considered to be a trench.
• Hazardous Atmosphere is an atmosphere that by reason of being explosive, flammable, poisonous, corrosive, oxidizing, irritating, oxygen-deficient, toxic, or otherwise harmful may cause death, illness, or injury to persons exposed to it.

• Hydro Excavation is a non-mechanical digging process which combines pressurized water and a high flow of moving air to simultaneously excavate and evacuate soils at a controlled rate. The soil and water slurry are then typically conveyed via a tube to a truck- mounted debris tank.
• Ingress and Egress mean “entry” and “exit,” respectively. In trenching and excavation operations, they refer to the provision of safe means for employees to enter or exit an excavation or trench.
• Protective System refers to a method of protecting employees from cave-ins, from material that could fall or roll from an excavation face or into an excavation, and from the collapse of adjacent structures. Protective systems include support systems, sloping and benching systems, shield systems, and other systems that provide the necessary protection.
• Registered Professional Engineer is a person who is registered as a professional engineer, or has qualifications that are recognized in the country, (or state), where the work is to be performed.
• Sheeting means the members of a shoring system that retain the earth in position and in turn are supported by other members of the shoring system.
• Shield (Shield System) means a structure that is able to withstand the forces imposed on it by a cave-in and thereby protect employees within the structure. Shields can be permanent structures or can be designed to be portable and moved along as work progresses. Additionally, shields can be either premanufactured or job-built in accordance with governmental regulations. Shields used in trenches are usually referred to as “trench boxes” or “trench shields.”
• Shoring (Shoring System) means a structure such as a metal hydraulic, mechanical or timber shoring system that supports the sides of an excavation and which is designed to prevent cave-ins.
• Sloping (Sloping System) means a method of protecting employees from cave-ins by excavating to form sides of an excavation that are inclined away from the excavation so as to prevent cave-ins. The angle of incline required to prevent a cave-in varies with differences in such factors as the soil type, environmental conditions of exposure, and application of surcharge loads (weight, sources of vibration, etc. and can include stockpiled materials, nearby traffic and excavation equipment).
• Support System refers to structures such as underpinning, bracing, and shoring that provide support to an adjacent structure or underground installation or to the sides of an excavation or trench.
• Underground Installations include, but are not limited to, utilities (sewer, telephone, fuel, electric, water, and other product lines), tunnels, shafts, vaults, foundations, and other under-ground fixtures or equipment that may be encountered during excavation or trenching work.

4. SUMMARY

• Prior to excavation work the site manager or their nominee must carry out a risk assessment.
• Local or national legislation may also require a method statement or safe system of work plan to be prepared.
• Local or national legislation may also require special permitting or approvals depending on the size and scope of the planned excavation.
• During excavation a competent person must supervise the excavation work, and the installation, alteration or removal of excavation support.
• A competent person must inspect excavations at regular intervals and a written inspection report must be made and retained.

• On existing Company facilities all excavation work must be carried out using a safety work permit and excavation permit. On construction sites an excavation permit is required.

• Following exposure of underground services for maintenance, modifications, etc., no work is to be undertaken until positive identification of the cable or pipework is made.
• All alterations made to underground piping, electrical or utility works require appropriate updates to existing drawings.

5. PROCEDURE

5.1      General Requirements

5.1.1   Excavation work on existing Company  facilities, exceeding 0.3 m (1 ft) in depth, must be carried out using a safety work permit and an excavation work permit (refer to Appendix A).

5.1.2   On construction sites, an excavation permit is required to identify and locate all underground obstructions, pipe or electrical conduits.

5.1.3   Safety work permits are also required for specific tasks, i.e., hot work and Lockout/Tagout, on an existing pressurized or energized system.

5.1.4   If the excavation has a depth equal to or greater than 1.22 m (4 ft) then atmospheric testing will be carried out and the requirements for a confined space entry permit or a non-permit required confined space entry will be considered. Where found to be necessary the respective standards 25-010533 and 25-010537 will be followed.

5.1.5   If the excavation work is to be carried out by a contractor, procedure 25-011502 shall be adhered to. Depending upon the magnitude of excavation work to be accomplished, consult the appropriate sections of 25-011702 and 4WCE-600700.

5.2      Before Excavation:

5.2.1   Prior to excavation work the site manager or his nominee must carry out a risk assessment that includes, but is not restricted to, the following:

• Clearly define the physical limits of the excavation area. At a minimum the scope and area of the excavation shall be defined on the excavation permits. Additionally, limits may be marked on plot plans or drawings. Consider marking the excavation area with traffic paint and/or flags to clearly delineate the approved limits of the excavation.
• Determine the soil type, i.e., sand, clay, stable rock etc. This should already be known at existing locations. This is important in determining what type of sloping, shoring or benching is required to be performed for the excavation or trench.
• Consider the type of surface and groundwater control measures that are appropriate for the excavation. In particular surface water running into the excavation and being pumped away in a contaminated condition.
• The nature and permeability of the ground and the extent of the area to be de-watered, taking into consideration the depth of the water table.
• Identification of underground services falling within 3 m (10 ft) of extremity of the proposed works by reviewing available drawings with drawing reference numbers recorded on the excavation permit.
• Looking around for obvious signs of underground services, e.g., valve covers or patching of the road surface.
• Using underground pipe or cable locators to trace any services and mark the ground accordingly. (It is strongly recommended that the contractor uses a metal detector to aid in the locating of underground services.)
• Ensuring that the person supervising excavation work has underground installation plans, with particular reference to electrical, fuel, gas and oil, fire main and make-up water systems. If these are not available then the local utility companies should be contacted in order to locate their services.

In the US and other regions, where mandated by regulation or available, the local “one call” system shall also be contacted to locate underground services. This may include making one call notifications even for on-site excavations, if so regulated by the local authority. It is imperative that the local facility know and understand their local requirements.

In the US, local requirements can be found at: http://www.call811.com/state-specific.aspx

• Making sure excavations do not affect the footings of scaffolds or the foundations of nearby structures. Walls may have very shallow foundations that can be undermined by even small trenches.
• Decide if the structure needs temporary support before digging starts. Survey of the foundations and advice of professional engineer may be needed. Excavations equal to or greater than 1.22 m (4 ft) deep may need temporary supports installed to prevent cave in.
• If excavation is deeper than 6 m (20 ft) then a professional engineer is required to design and provide calculations for support and shielding needed to render the excavation safe for use.
• Advising personnel of the requirements for isolation, Lockout/Tagout, etc., and any additional work permits if the excavation is to expose an underground service for repair.
• Determining the requirements to prevent:
• materials falling onto people working in the excavation;
• people and vehicles falling into the excavation;
• people being struck by moving equipment;
• Accidents to members of the public during normal working hours, or where children might get onto site out of hours.
• Deciding how access into the excavation is to be achieved for people, equipment and vehicles.
• Decide whether there is the need to implement procedure 25-010533 Permit-Required Confined Space Entry.
• Where and how stockpiling of excavated and backfilling materials will be carried out.
• Identifying where if any contaminated soil could exist and determining how it should be disposed of based upon local regulations.
• Deciding whether a fire watch or designated person is needed to solely monitor the excavation activities when working in or around potentially hazardous equipment.
• Ensuring the necessary equipment such as trench sheets, shoring, shields etc. are available.

Details of the Risk Assessment, including appropriate safety precautions, shall be included on the required Safety Work Permit and/or excavation permit.

5.3      During Excavation:

5.3.1   A competent person must supervise the excavation work, and the installation, alteration or removal of excavation support.

5.3.2   Hand tools (e.g., shovels, spades, narrow shovel tip type. Picks may only be used for breaking the surface) shall be used to confirm the exact location and depth of any underground services falling within 1 m (3 ft).

5.3.3   When exposed, all underground services must be identified as soon as possible. An adequate length should be cleared to check for identification marks, color, size, service, etc. Where lines cannot be clearly identified they must be checked for electrical current by portable detection equipment. If no current is detected, it cannot be assumed that it is not an electrical cable, it may be redundant or not in use at the time. If this is the case then further investigation is required with site or local utilities staff.

5.3.4   All personnel working in excavation must wear appropriate PPE. As a minimum, a hard hat, safety shoes (steel toed), safety glasses with rigid side shields and gloves.

5.3.5   All excavations 1.22 m (4 ft) or more deep must have rigid barricades to prevent personnel falling into them. If the trench is to be open at night, additional warning lamps, lights, etc., shall be installed.

5.3.6   Vehicles must be kept a distance of 3 m (10 ft) away from excavations except where specific provisions have been made to support such vehicles. Use brightly painted barriers where necessary.

5.3.7   Keep personnel separate from moving equipment such as excavators. Nobody is permitted in excavation while equipment is used next to the edge.

5.3.8   On completion of the excavation do not site petrol or diesel engine equipment, such as generators or compressors, in or near the edge of an excavation unless fumes can be ducted away or the area can be ventilated.

5.3.9   Ensure that trenches 1.22 m (4 ft) or more deep are adequately sloped or timbered (or other proprietary support systems) to prevent collapsing of the trench walls on to persons working inside. Personnel must never work ahead of the support or go into unsupported excavations (refer to 4WCE-600700).

5.3.10 Ensure excavated material or other material is not stored close to the sides of the excavation. The spoil or excavated material must be a minimum of 1.22 m (4 ft) back from the edge of

the excavation or trench. The soil may fall into the excavation and the extra loading will make the sides more prone to collapse (refer to 4WCE-600700).

5.3.11 In excavations 1.22 m (4 ft) or more in depth good ladder access or other safe ways of getting in and out of excavations shall be provided. Access and egress ladders are required in any excavation at a maximum of 7 m (25 ft) of lateral travel.

5.3.12 In trenches 1.22 m (4 ft) or more deep atmospheric monitoring must be performed to ensure there is not an oxygen deficient atmosphere (less than 19.5%), or hazardous atmosphere (10% LEL, 10% PEL) and remonitoring if the hazard has not been eliminated.

If these tests indicate an oxygen deficient, toxic or flammable atmosphere then there is also a requirement to consider the implementation of the procedures 25-010533 – Permit-Required Confined Space Entry or 25-010537 – Non-Permit-Required Confined Space Entry.

5.3.13 Every attempt should be made to eliminate standing water from trenches. Before removal you should take into consideration whether the water is contaminated by chemicals or contains a potential health hazard from vermin. If you de-water the excavation too much this can also make the sides of the excavation more prone to collapse.

5.3.14 Hydro excavation work shall only be performed by competent persons following industry guidelines and local regulatory requirements for safe work practices.

At a minimum, when performing hydro excavation activities:

• A JSA or Risk Assessment must be documented and reviewed with the operators and Safety Work Permit Issuer which addresses the scope of work, the potential risks, and safety precautions to be taken.

• Procedures must be established, reviewed and followed for the safe removal of obstructions in the vacuum tube should the process become blocked during the excavation.

• Only qualified personnel are permitted to operate hydro excavation equipment or assist the operator.
• Safe zones and barricading must be established (a 3.0 m or 10 ft. zone is minimum).
• Appropriate PPE for the operation will be identified during the risk assessment. All persons entering the barricaded area must adhere to the PPE requirements.
• A minimum of two persons must be engaged in the operation. One to operate the lance and the other at the boom or vacuum truck operation. The two persons must maintain communication with each other at all times during the excavation work.

• The equipment must have fail safe provisions at the point of excavation to shut down the lance in case of an emergency (such as “dead man” trigger or valve).
• The equipment must be operated in accordance with the manufacturer’s instructions.
• The equipment must be inspected and confirmed to be in operating condition, in accordance with the manufacturer’s instructions prior to each use.

5.4      Inspecting Excavations:

5.4.1   A competent person must inspect excavations (for a typical inspection checklist see Appendix B).

• At the start of each shift before work begins.
• After a change in weather conditions, e.g., heavy rain or after a thaw.
• After any event likely to have affected the strength or stability of the excavation.
• After an accidental fall of rock, earth or other material.

5.4.2   Inspections must be documented and retained with the completed excavation permit and Safety Work Permit (if applicable).

In the United Kingdom:  A written report must be made after inspection is needed in any seven day period and retained for the duration of the construction contract or three months whichever is the greater.

5.4.3   Work must be stopped if the inspection shows the excavation is unsafe.

5.5      Following Excavation:

5.5.1   Following exposure of underground services for maintenance, modifications, etc., no work is to be undertaken until positive identification of the cable or pipework is made. On existing Company  facilities all work must be carried out using a safety work permit.

5.5.2   De-energized pipes or cables must be checked for damage prior to reuse.

5.5.3   All modifications or additions to or alterations from existing drawings must be notified to site management and ‘As built’ documents and drawings etc duly updated.

5.5.4   Removal of all waste and spoil material shall be performed according to national or local regulations with specific attention being directed to special wastes and contaminated soils.

5.5.5   Preparing a risk assessment and method study for the backfilling of any open excavations.

6. RELATED INFORMATION

6.1      Company EHS&Q Documents

25-010530	Safety Work Permit
25-010532	Energy Isolation and Lockout/Tagout/Try
25-010533	Permit-Required Confined Space Entry
25-010537	Non-Permit-Required Confined Space Entry
25-011502	Contractor Management

 

6.2      Company  Engineering Documents

4WCE-600700               Construction Safety

6.3      Other Documents

OSHA Regulations         1926.651 Specific Excavation Requirements

HSE Information Sheet  Safety in excavations Construction Sheet No. 8

How to make Excavation Permit

Excavation Inspection Report