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Subchapter 4. Construction Safety Orders
Article 6. Excavations
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§1542. Shafts.

(a) General.

(1) All wells or shafts over 5 feet in depth into which employees are permitted to enter shall be retained with lagging, spiling, or casing.

EXCEPTION: Exploration shafts; see Section 1542 (d).

(2) The lagging, spiling or casing shall extend at least one foot above ground level and shall be provided the full depth of the shaft or at least five feet into solid rock if possible.

(3) All wells, pits, shafts, caissons, etc. shall be barricaded or securely covered.

(4) Upon completion of exploration and similar operations, temporary wells, pits, shafts, etc., shall be backfilled.

(b) Small Shafts in Hard Compact Soil.

Two-inch (nominal) cribbing may be used in square shafts not over 4 feet square in hard compact soil. Each member shall be cut 1/2 way through the width of the member and dovetailed into position so each member will act as a shore as well as lagging. Strips shall be nailed in each corner to prevent the boards from dropping down.

(c) Shafts in Other Than Hard Compact Soil.

(1) A system of lagging supported by braces and corner posts shall be used for square or rectangular shafts. Corner posts of 4-inch by 4-inch material are normally acceptable in shafts 4 feet square, or smaller, if they are braced in each direction with horizontal 4-inch by 4-inch members at intervals not exceeding 4 feet. Braces and corner posts in larger shafts shall be correspondingly larger as determined by a civil engineer.

(2) Round shafts shall be completely lagged with 2-inch material which is supported at intervals not greater than 4 feet by means of adjustable rings of metal or timber that are designed to resist the collapsing force, or cased in a manner that provides equivalent protection.

(d) Exploration Shafts. Only a geotechnical specialist shall be permitted to enter an exploration shaft without lagging, spiling or casing for the purpose of subsurface investigations under the following conditions:

(1) Initial Inspection. The type of materials and stability characteristics of the exploration shaft shall be personally observed and recorded by the geotechnical specialist during the drilling operation. Potentially unsafe exploration shafts shall not be entered.

(2) Surface Casing. The upper portion of the exploration shaft shall be equipped with a surface ring-collar to provide casing support of the material within the upper 4 feet of the exploration shaft. The ring-collar shall extend at least 1-foot above the ground surface.

(3) Gas Tests. Prior to entry into exploration shafts, tests and/or procedures shall be instituted to assure that the atmosphere within the shaft does not contain dangerous air contamination or oxygen deficiency. These tests and/or procedures shall be maintained while working within the shaft to assure that dangerous air contamination or oxygen deficiency will not occur. (See Section 5156 of the General Industry Safety Orders.)

(4) Unstable Local Conditions. The geotechnical specialist shall not descend below any portion of any exploration shaft where caving or groundwater seepage is noted or suspected.

(5) Ladder and Cable Descents. A ladder may be used to inspect exploration shafts 20 feet or less in depth. In deeper exploration shafts, properly maintained mechanical hoisting devices with a safety factor of at least 6 shall be provided and used. Such devices shall be under positive control of the operator being positive powered up and down with fail-safe brakes.

(6) Emergency Standby Employee. An emergency standby employee shall be positioned at the surface near the exploration shaft opening whenever a geotechnical specialist is inside the shaft.

(7) Communication. A two-way, electrically-operated communication system shall be in operation between the standby employee and the geotechnical specialist whenever boring inspections are being made in exploration shafts over 20 feet in depth or when ambient noise levels make communication difficult.

(8) Safety Equipment. The following safety equipment shall be used to protect the geotechnical specialist:

(A) An approved safety harness which will suspend a person upright and that is securely attached to the hoist cable.

(B) A 12-inch to 18-inch diameter steel coneshaped headguard/deflector that is attached to the hoist cable above the harness.

(C) A hoist cable having a minimum diameter of 5/16 inches.

(D) Approved head protection. (See Section 1515.)

(9) Electrical Devices. All electrical devices used within the exploration shaft by the geotechnical specialist shall be approved for hazardous locations.

(10) Surface Hazards. The storage and use of flammable or other dangerous materials shall be controlled at the surface to prevent them from entering the exploration shaft.

NOTE: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. Amendment of subsection (e) filed 5-21-75; effective thirtieth day thereafter (Register 75, No. 21).

2. Amendment filed 8-23-82; effective thirtieth day thereafter (Register 82, No. 35).

3. Amendment of subsection (a) and new subsection (e) filed 11-12-82; effective thirtieth day thereafter (Register 82, No. 46).

4. Repealer of subsection (a) NOTE, adoption of subsections (a)(3) and (a)(4), repealer of subsection (d) text and relettering filed 8-26-91; operative 9-25-91 (Register 92, No. 13).

5. Change without regulatory effect amending subsection (a)(1) filed 8-19-92; operative 8-19-92 (Register 92, No. 34).

6. Editorial correction of printing error restoring designation of subsection (d) (Register 92, No. 34).

7. Change without regulatory effect amending subsection (a)(1) Exception filed 2-22-93; operative 3-24-93 pursuant to title 1, section 100, California Code of Regulations (Register 93, No. 9).

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