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Subchapter 4. Construction Safety Orders
Article 6. Excavations

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§1541.1. Requirements for Protective Systems, Appendix B

Sloping and Benching

(a) Scope and application. This appendix contains specifications for sloping and benching when used as methods of protecting employees working in excavations from cave-ins. The requirements of this appendix apply when the design of sloping and benching protective systems is to be performed in accordance with the requirements set forth in Section 1541.1(b).

(b) Definitions.

Actual slope means the slope to which an excavation face is excavated.

Distress means that the soil is in a condition where a cave-in is imminent or is likely to occur. Distress is evidenced by such phenomena as the development of fissures in the face of or adjacent to an open excavation; the subsidence of the edge of an excavation; the slumping of material from the face or the bulging or heaving of material from the bottom of an excavation; the spalling of material from the face of an excavation; and ravelling, i.e., small amounts of material such as pebbles or little clumps of material suddenly separating from the face of an excavation and trickling or rolling down into the excavation.

Maximum allowable slope means the steepest incline of an excavation face that is acceptable for the most favorable site conditions as protection against cave-ins, and is expressed as the ratio of horizontal distance to vertical rise (H:V),

Short term exposure means a period of time less than or equal to 24 hours that an excavation is open.

(c) Requirements.

(1) Soil classification. Soil and rock deposits shall be classified in accordance with Appendix A to Section 1541.1.

(2) Maximum allowable slope. The maximum allowable slope for a soil or rock deposit shall be determined from Table B-1 of this appendix.

(3) Actual slope.

(A) The actual slope shall not be steeper than the maximum allowable slope.

(B) The actual slope shall be less steep than the maximum allowable slope, when there are signs of distress. If that situation occurs, the slope shall be cut back to an actual slope which is at least 1/2 horizontal to one vertical (1/2H:1V) less steep than the maximum allowable slope.

(C) When surcharge loads from stored material or equipment, operating equipment, or traffic are present, a competent person shall determine the degree to which the actual slope must be reduced below the maximum allowable slope, and shall assure that such reduction is achieved. Surcharge loads from adjacent structures shall be evaluated in accordance with Section 1541(i).

(4) Configurations. Configurations of sloping and benching systems shall be in accordance with Figure B-1.

                        TABLE B-1
                 MAXIMUM ALLOWABLE SLOPES
______________________________________________________________

 SOIL OR ROCK TYPE  | MAXIMUM ALLOWABLE SLOPES (H:V)(1) FOR
                    | EXCAVATIONS LESS THAN 20 FEET DEEP(3)
____________________|___________________________________
STABLE ROCK         | VERTICAL (90 Deg.)
TYPE A (2)          | 3/4:1    (53 Deg.)
TYPE B              | 1:1      (45 Deg.)
TYPE C              | 1 1/2:1  (34 Deg.)
____________________|____________________________________
  NOTES:
  1. Numbers shown in parentheses next to maximum allowable
slopes are angles expressed in degrees from the horizontal. Angles have
been rounded off.
  2. A short-term maximum allowable slope of 1/2H:1V (63 degrees)
is allowed in excavations in Type A soil that are 12 feed (3.67 m) or less
in depth. Short-term maximum allowable slopes for excavations greater than
12 feet (3.67 m) in depth shall be 3/4H:1V (53 degrees).
  3. Sloping or benching for excavations greater than 20 feet
deep shall be designed by a registered professional engineer.

Figure B-1
Slope Configurations

(All slopes stated below are in the horizontal to vertical ratio)
B-1.1 Excavations made in Type A soil

1. All simple slope excavations 20 feet or less in depth shall gave a maximum allowable slope of 3/4:1.

Simple Slope-General

Exception: Simple slope excavations which are open 24 hours or less (short term) and which are 12 feet or less in depth shall have a maximum allowable slope of 1/2:1.

Simple Slope- Short Term

2.All benched excavations 20 feet or less in depth shall have a maximum allowable slope of 3/4 to 1 and maximum bench dimensions as follows:

Simple Bench
Multiple Bench

3. All excavations 8 feet or less in depth which have unsupported vertically sided lower portions shall have a maximum vertical side 3 1/2 feet.

Unsupported Vertically Sided Lower Portion-Maximum 8 Feet Depth

All excavations more than 8 feet but not more than 12 feet in depth with unsupported vertically sided lower portions shall have a maximum allowable slope of 1:1 and a maximum vertical side of 3 1/2 feet.

Unsupported Vertically Sided Lower Portion-Maximum 12 Feet in Depth

All excavations 20 feet or less in depth which have vertically sided lower portions that are supported or shielded shall have a maximum allowable slope of 3/4:1. The support or shield system must extend at least 18 inches above the top of the vertical side

Supported or Shielded Vertically Sided Lower Portion

B- 1.2 Excavations Made in Type B Soil

1. All simple slope excavations 20 feet or less in depth shall have a maximum allowable slope of 1:1.

Simple Slope

2. All benched excavations 20 feet or less in depth shall have a maximum allowable slope of 1:1 and maximum bench dimensionsas follows:

Single Bench
Multiple Bench

3. All excavations 20 feet or less in depth which have vertically sided lower portions shall be shielded or supported to a height at least 18 inches above the top of the vertical side. All such excavations shall have a maximum allowable slope of 1:1

Vertically Sided Lower Portion

B- 1.3 Excavations Made in Type C Soil

1. All simple slope excavations 20 feet or less in depth shall have a maximum allowable slope of 1 1/2:1

Simple Slope

2.All excavations 20 feet or less in depth which have vertically sided lower portions shall be shielded or supported to a height at least 18 inches above the top of the vertical side. All such excavations shall have a maximum allowable slope of 1 1/2:1.

Vertically Sided Lower Portion

3. All other sloped excavations shall be in accordance with the other options permitted in 1541.1(b)

B- 1.4 Excavations Made in Layered Soil

1. All excavations 20 feet or less in depth made in layered soils shall have a maximum allowable slope for each layer as set forth below:

B OVER A
C OVER A
C OVER B
A OVER B
A OVER C
B OVER C

2. All other sloped excavations shall be in accordance with the other options permitted in 1541.1(b).

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

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