Wyoming Workers` Safety 1510 E Pershing Blvd. Cheyenne WY

EXCAVATION WORKSHEET
A = width at bottom
B = depth
C = width at top
Wyoming Workers’ Safety
1510 E Pershing Blvd.
Cheyenne WY 82002
307-777-7786
C=A+B
C = A + 1.5B 3/4 : 1
(Type A Soil)
C = A + 2.0B 1 : 1
(Type B Soil)
OSHA and the Competent Person
C = A + 3.0B 1 1/2 : 1 (Type C Soil)
Excavation Length
Visual Test
__________
Type of material:
coarse fine
Safe Means of Egress
Observe excavated soil:
clumps breakup
Excavated Material Distance ____
Observe side and surface area: crack/fissures
spalling
Previously disturbed soil:
Identify Layered Systems
Yes
Evidence of Water:
Yes
Bottle Test Results
30 seconds ______% sand
30 minutes ______% silt
Soil Classification
No
Yes
No
___________
Manual Test
Plasticity
Dry Strength
Thumb Penetration
No
3 hours
_____% clay
Is the excavation more
than 5 feet in depth?
NO
YES
Is the excavation entirely
stable rock?
Excavation may be made
with vertical sides.
Excavation must be sloped
or shielded.
Go to Figure 2
Go to Figure 3
FIGURE 1 – PRELIMINARY DECISIONS
• Location and protection of underground installations
1926.651 (b)
• ONE CALL OF WYOMING 1-800-849-2476
• Recognize, test, and control hazardous atmospheres
1926.651 (g)
• Daily inspections of excavations, adjacent areas and
protective systems
1926.651 (k)
• Determine the impact of distress and/or surcharge loads
and adjust the protective system accordingly
Appendix B
• Excavate in accordance with OPTION 1-Slope 1 1/2H to 1V
or use OPTION 2 – classify soils and select a sloping system
using OSHA Appendix A and B.
The following figures are a graphic summary of the requirements contained in this chapter
for excavations 20 feet or less in depth. Protective systems for use in excavations more
than 20 feet in depth must be designed by a registered professional engineer in accordance
with 1926.652 (b) & (c).
Is there a potential for a
cave-in?
The on-site “COMPETENT PERSON,” as defined by OSHA 1926.650 (b), has
important responsibilities, including but not limited to:
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Minimum Standards
Type A Soil
Includes:
1.
Cohesive Soils
2.
Unconfined compressive strength exceeds 1.5
T/SF.
3.
Cemented granular or caliche may be included.
Excludes:
1.
Fissured or subject to vibration from heavy traffic
or similar effects,
2.
Sloped layered system dipping into excavation
areas on 4H:1V or greater.
3.
Other factors requiring a less stable
classification
such as excessive moisture or free running or
standing water.
4.
Previously disturbed soil.
5.
Cuts in excess of 20 feet.
Top width equals 1.5 x
depth plus bottom width.
If bottom width is 4 ft.,
then:
Depth
Width
8 ft.
16 ft.
10 ft.
19 ft.
12 ft.
22 ft.
14 ft.
25 ft
16 ft.
28 ft.
17 ft.
31 ft.
20 ft. max
34 ft.
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Definitions:
Sloping selected as the method of protection
Competent Person One who is capable of identifying existing and predictable
hazards, and who has authorization to take prompt corrective measures to
eliminate them. Competent Person status shall be determined by employer.
Will soil classification be made in accordance with 1926.652 (b)
YES
Excavation Any man-made cut, cavity, trench or depression in an earth
surface, formed by earth removal.
Excavation must comply with one of the
following options:
Protective System Includes support systems, sloping and benching systems,
shield system, and other systems that provide necessary protection.
Option 1:
1926.652 (b) (2) which requires
Appendices A and B to be followed
Registered Professional Engineer A person who is registered as a
professional engineer in the state where work is to be performed.
ADDITIONAL SAFETY CONSIDERATIONS
Minimum Standards
Type A Soil
(Continued)
Maximum Cut 12 ft.
Slope to ½ H to 1V
Condition A
-
Condition B
Condition A & B -
Excavation must comply
with Sec. 1926.652 (b) (1)
which requires a slope of 1
1/2H:1V (34º).
Option 2:
1926.652 (b) (3) which requires other
tabulated data (see definition to be
followed.)
Stable Rock Natural solid mineral material that can be excavated with vertical
sides and will remain intact while exposed.
1. Ladders or ramps required within 25 ft. of workers in trench excavations over
4 ft. in depth.
2. No excavated soils stored within 2 ft. of the edge of the excavation.
3. No equipment/vehicles or materials within 2 ft of the edge of the excavation.
4. Do not allow employees underneath suspended loads.
5. Personal protective equipment (hardhats, safety glasses, safety toe boots,
etc.) must be used when a hazard exists.
NO
Option 3:
1926.652 (b) (4) which requires the
excavation to be designed by a registered
professional engineer.
FIGURE 2 – SLOPING OPTIONS
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TABLE 1.2
ALUMINUM HYDRAULIC SHORING
VERTICAL SHORES FOR SOIL TYPE B
Top width equals 1 x depth
plus bottom width. If
bottom width is 4 ft., then:
Hydraulic Cylinders
Depth
of
Trench
(feet)
Maximum
Horizontal
Spacing (feet)
Depth
Width
8 ft.
12 ft.
10 ft.
14 ft.
over 5
up to 10
8
12 ft. max
15 ft.
over 10
up to 15
6.5
(cuts in excess of 12 ft. require
sloping on 3/4H to 1V)
over 15
up to 20
5.5
over 20
4ft. maximum vertical height is allowable for Type A and B soils
Maximum 20 ft. cut.
3 ½ maximum vertical height is allowable for Type A.
Applies to cohesive soils only, not granular.
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Maximum
Vertical
Spacing
(feet)
Up to 8
8 to 12
4
2 inch
diameter
2 inch
diameter
note (2)
12 to 15
3 inch
diameter
NOTE (1)
Footnotes to tables and general notes on hydraulic shoring found in Appendix D, item (g).
Note (1): See Appendix D, Item (g) (1)
Note (2): See Appendix D, Item (g) (2)
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MINIMUM STANDARDS
TYPE B SOIL
Test For Granular Soils
Includes:
1. Cohesive soils with UCS of .5 T/SF min. to 1.5 T/SF max.
2. Type A soils subject to external vibration or loading.
3. Type A soils that are fissured.
4. Type A soils previously disturbed, but well compacted.
Excludes:
1. Cuts in excess of 20 ft.
Top width equals 2 x depth
2. Soils with free running or standing water.
plus bottom width. If bottom
width is 4 ft., then:
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 1H:1V.
Depth
Width
8 ft.
20 ft.
10 ft.
24 ft.
12 ft.
28 ft.
14 ft.
32 ft
16 ft.
36 ft.
17 ft.
40 ft.
20 ft. max
44 ft.
•
•
•
•
Granular soil cannot be molded when moist
and crumbles easily when dry.
Moist granular soils that contain some cohesive material will
exhibit signs of cohesion between particles.
Penetrometer does not work on granular soils.
Granular soil has no cohesive strength.
WARNING
•
Excessive moisture or drying will cause changes in apparent
angle of incline of granular soils and thus the time an excavation
is open is of critical
importance.
•
Granular soils are susceptible to shock and/or vibration failure.
•
Granular material that would exhibit cohesive properties when
moist will lose those properties when either saturated or dried.
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COHESIVE SOILS – CLAY AND CLAYSTONES
Unconfined Comprehensive Strengths (UCS)
MINIMUM STANDARDS
TYPE C SOIL
(continued)
Description of Clay
Blows Per Ft.
UCS T/SF
Soil Type
Very Soft
Under 2
Under .25
C
Soft
2 to 4
.25 to .50
C
Medium
4 to 8
.50 to 1.0
B
Stiff
8 to 15
1.0 to 2.0
B-A
Very Stiff
15 to 30
2.0 to 4.0
A
Hard
Over 30
Over 4.0
A
Test for Cohesive Soils
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 1/2H:1V.
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1. Cohesive soils do not crumble and are plastic and easily molded when moist.
2. Can easily be shaped into a ball and/or rolled into pencil-sized threads before crumbling.
3. Type A Soil –
UCS =1.5 or more T/SF
Type B Soil –
UCS =.5 to 1.5 T/SF
Type C Soil –
UCS = .5 or less T/SF
4. Refer to soils report for blow counts or UCS.
5. May use penetrometer or shear vane as a guide to UCS of cohesive soil.
EXCAVATION DEPTH OVER 20 FEET
Sloping or benching shall be designed by a registered professional engineer.
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TABLE D-1.1
ALUMINUM HYDRAULIC SHORING
VERTICAL SHORES FOR SOIL TYPE A
Depth
of
Trench
(feet)
Excavations 8 feet or less in depth which
have unsupported vertically sided lower
portions shall have a maximum vertical
side of 3 ½ feet.
Hydraulic Cylinders
Maximum
Horizontal
Spacing (feet)
over 5
up to 10
8
over 10
up to 15
8
over 15
up to 20
7
over 20
MINIMUM
STANDARDS
Type A Soil
Maximum
Vertical
Spacing
(feet)
Up to 8
4
2 inch
diameter
8 to 12
12 to 15
2 inch
diameter
note (2)
Excavations more than 8 feet but not more than
12 feet in depth which have unsupported
vertically sided lower portions shall have a
maximum allowable slope of 1:1 and a maximum
vertical side of 3 ½ feet.
3 inch
diameter
All excavations 20 feet or less 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.
NOTE (1)
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MINIMUM STANDARDS
TYPE C SOIL
GRANULAR SOILS – FINE TO COARSE SANDS
Unconfined Comprehensive Strength of soft cohesive soil is less tan .5T/SF and should be
treated similar to granular soils.
Relative Density of Sands According to
Results of Standard Penetration Tests
Includes:
1. Cohesive soil with UCS less than .5 T/SF
2. Granular soils including gravel , sand, and loamy sand.
3. Saturated or submerged soils.
4. Type A and B soils- Option 1 – 1926.652 (b)(1).
* Recommend specific written safety plan.
* May require trench box or shoring.
* Consult with Safety Manager Immediately
* Do not proceed until proper precautions are taken.
Max. Cut – 20 ft.
Slope 1 1/2H:1v
Top width equals
3 x depth plus bottom
width. If bottom width is
4 ft., then:
Depth
Width
8 ft.
28 ft.
Blows Per Ft.
Relative Density
Soil Type
0 to 4
Very Loose
C
10 ft.
34 ft.
4 to 10
Loose
C
12 ft.
40 ft.
10 to 30
Medium
C
14 ft.
46 ft
30 to 50
Dense
B
16 ft.
52 ft.
Over 50
Very Dense
B*
17 ft.
58 ft.
20 ft. max
64 ft.
* Very Dense sand may be Type A if solidly cemented.
All simple slope excavations 20 feet or less in depth shall
have a maximum allowable slope of 1 1/2H:1V.
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