EXCAVATIONS, SHORING AND TRENCHES GUIDELINES

EXCAVATIONS, SHORING, AND TRENCHES

Prior to commencing any type of earthwork (i.e. excavations, shoring and/or trenches) the locations of any underground utilities/services should be determined.

Guidelines:

 Before commencing work ascertain the location of all existing underground facilities/services.

o Contact work jurisdictions’ “One Call / Call before you Dig” or BC One Call to

find out if there are any underground facilities in the proposed excavation area,

if so – who they are owned by? If the underground facility owner is a Member of

BC One Call, they will contact you directly to advise you of the exact location of the underground facility in the excavation area. If the owner is not a member of BC One Call, you will have to contact them directly to find out the locations of their underground facilities.

o DO NOT PROBE FOR GAS OR ELECTRICAL SERVICES WITH A POINTED TOOL OF ANY KIND.

 Always hand-expose all buried facilities before using mechanical excavation equipment.

(Hand-exposing means exposing a buried facility, whose location has been marked, using non-powered tools and equipment (i.e. shovel).

 If possible, blunt shovels should be used to expose the facility. Take caution using spade-shaped shovels.

 Diggers should never jump on or use their entire body weight on the shovel when digging.

 Use a prying (rather than striking) motion to loosen hand dirt.

 Dig at an angle if possible, to reduce damage to the facility.

 If digger has made a reasonable attempt to hand expose a buried facility, but cannot find it, the digger must immediately contact the facility owner directly for help. Once all the buried facilities have been hand exposed and are clearly visible, the excavator may use mechanical equipment (but not within the distance specified by the facility owner).

 Always support and protect exposed facilities, unsupported exposed facilities may sag and cause breaks or damage.

 If excavating parallel to a buried facility, note that shallow buried facilities (i.e. telephone, cable, electric) are not necessarily installed in a straight alignment. Find out from facility owner the best way to proceed with excavation.

 Before starting work, ensure plans/procedures for excavation to be undertaken are in conformity with requirements of the owner of the service, i.e. BC Hydro

Stake-outs of all nearby services must be completed prior to starting work.

 Supervisory Personnel must have proof that locates were completed.

 Clearly marked stakes must indicate the utility/service.

 In the case of any uncertainty as to the specific location of services, the work is not to commence until the service is exposed or located by other means.

 Never use a sharp device to detect underground utilities and services.

 Services/Utilities that are known to be close to the foundation elements may require some type of special protection. Contact the appropriate authority to agree on such measures.

 If unanticipated services are encountered, work shall cease at that location until the service has been identified and deemed safe.

 EXCAVATIONS, SHORING, AND TRENCHES – GENERAL INFORMATION

It is important to review the work jurisdictions’ OHS Regulations/Codes prior to starting any excavation work.

Trench Excavation

 Generally less than 12ft in width

 Examples of trenches include pipeline and manhole excavations

 Trenches must be designed by a professional engineer if greater than 20ft in depth.

Bulk

 Greater than 12ft in width

 Examples of bulk excavations include foundations and basements

 Bulk excavations must be designed by a professional engineer if greater than 20ft in depth

Possible Reasons for Soil Instability

 Increase in depth of cut

 Saturation or increase in water content (i.e. heavy rainfall). Check the weather

report on a regular basis for the duration of the excavation work.

 Hydrostatic or water pressure

 Weight of material and equipment

 Shock and vibration from equipment (i.e. pile driving)

 Frost action (cold weather)

When a Professional Engineer is required.

 Excavations greater than 4ft in depth with sides sloped greater than ¾ to 1

 Excavations greater than 20ft in depth

 Excavations adjacent to structures

 Excavations in soil subject to vibration or hydrostatic pressure

 Excavations alongside slopes greater than ¾ to 1

 Excavations shored in a manner differing from “stick-built” shoring, i.e. the use of shoring cages

 Excavations as determined by the work

Issues and Information to Consider for Excavations, Shoring and Trenches

 Always follow applicable work jurisdictions’ OHS Regulations for excavations,

trenching and shoring. Keep in mind that there may be additional government acts and regulations that may also need to be followed.

 Excavation work close to utilities must be undertaken in conformity with applicable government regulations and within the requirements of the owner of the service.

 NEVER ASSUME AN EXCAVATION OR TRENCH IS SAFE. Any open face will

eventually fail. Take all precautions necessary to protect workers working in or near the excavation, trench or shoring area.

 The positioning of mobile and heavy equipment – Parked equipment & vehicles must be parked at least 10ft away from the edge of the excavation or trench.

 Working near excavations, trench or shoring – A qualified person (the Supervisory Personnel) must determine the location for a crane or other heavy equipment when used adjacent to an excavation, slope or backfilled area.

 Guarding of excavations, trenches and shoring – Guardrails (if exceeding a depth of more than 10ft), caution tape, barriers, warning signage

 Obstructed vision – consider how well the excavator operator and workers working near or in the excavation can see each other! Take necessary precautions as required.

 Excavation crossings – will a walkway (with guardrails) over the excavation be

required?

 Harmful atmospheres – Does the excavation have the potential to have a

hazardous atmosphere? Could it be considered a confined space?

 Prevention of water accumulation – Will arrangements need to be made for

dewatering? If so, who will be responsible for providing it?

 Access/Egress – when workers have to enter excavations more than 4ft (1.22m)

deep, access/egress in the form of a ladder, must be extended to the bottom and

must be 3ft (0.9m) above ground level. It must also be provided within 25ft (7.5m) of the work area. Additional access/egress must be provided in the event that the

excavation exceeds 10ft (3m) in depth.

 In addition to the above, workers must not enter excavations/trenches more than 4ft (1.22m) in depth unless:

 The sides of the excavation are slopped to a safe angle as specified in the

work jurisdictions’ OHS Regulations OR in accordance with the written

instruction of a professional engineer;

 The sides of the excavation/trench have been supported by the use of sheet

piling, shoring/bracing or by a manufactured trench box meeting the

applicable work jurisdictions’ OHS standards;

 Assess and plan out stockpile locations prior to starting excavation work.

 Stockpiling excavated material – Factor “area of natural repose” (which way the soil slopes when laid flat on the ground). Excavated material must be stockpiled at least 4ft (1.22m) away from the edge of the excavation and 2ft (60cm) away from

trenches.

 Removal of excavated materials – will the excavated materials need to be removed once the excavation is complete? Will steps need to be taken to control erosion?

 Excavator operators and workers working around or in excavations should know designated signalman that can communicate with the operator at all times.

 When used, installation and removal of shoring must be done according to work

jurisdictions’ OHS Regulations. The work procedures for installation or removal of

shoring must ensure that workers are not exposed to undue risk. In general, shoring must be installed from the top down and removed in reverse order.

 Inspections – excavations, trenches, and shoring should be inspected on a

continuous basis, especially if there are changes in weather (i.e. rainfall) and at the start of each shift. Inspections should look out for:

 Any change in the size of the excavation;

 Any changes to the sides of the excavation;

 Any change in the water level, water egress;

 Seepage from the sides;

 Any movement of shoring backfilled materials (i.e. rip rap);

 Change in the excavation footing;

Issues and Information to Consider for Excavations, Shoring and Trenches – Continued

 Settlement of adjacent structures;

 Is trench support system being used according to plan? (Manufacturer’s

instructions should be kept on site with Supervisory Personnel).

Benching/Sloping

 Sloping must be no steeper than ¾ to 1 for trench & bulk excavation walls

 The above information/issues/pre-planning will also apply to excavations that are sloped/benched

 Sloping the sides of excavations may dine instead of shoring only where workers have protection equivalent to that provided by shoring. Materials such as rocks or tree stumps must be removed from slopes where there is a danger of them dislodging.

 Benching is combining sloping and shoring

 Once sloping/benching is completed, a support system must be installed and

inspected daily.