“all simple slope excavations 20 feet or less in depth......shall have a maximum allowable slope...
TRANSCRIPT
“All simple slope excavations 20 feet or less in depth...
...shall have a maximum allowable slope of 1 : 1.”
( 45 degrees )
Type B may be simply sloped or benched.
“All simple slope excavations 20 feet or less in depth...
...shall have a maximum allowable slope of 1 : 1.”
( 45 degrees )
Type B may be simply sloped or benched.
The blue slope represents 1: 1 (45 degrees)
“All simple slope excavations 20 feet or less in depth...
...shall have a maximum allowable slope of 1 : 1.”
( 45 degrees )
Type B may be benched.
“All simple slope excavations 20 feet or less in depth...
...shall have a maximum allowable slope of 1 : 1.”
( 45 degrees )
Type B may be benched.
Will this work?
No benching in Type C soil.
If the soil was Type A, the degree of these benched slopes would be too steep.
“All simple slope excavations 20 feet or less in depth...
...shall have a maximum allowable slope of 3/4 : 1.”
( 53 degrees )
Type A may be simply sloped or benched.
“All simple slope excavations 20 feet or less in depth...
...shall have a maximum allowable slope of 3/4 : 1.”
( 53 degrees )
Type A may be simply sloped or benched.
The blue slope represents 1: 1 (45 degrees)
“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.”
( 63 degrees )
Type A (short term dig)
The blue slope represents 1: 1 (45 degrees)
Sloping & Benching Tips
The maximum allowable slopes apply when above a shield, too.
Sloping & Benching Tips
The top of the shield needs to be at least 18 inches above the soil.
Type C soil cannot be benched.
(even if incorrectly identified as Type B)
No sloping or benching when deeper than 20 feet.
Unless a Registered Professional Engineer designs the sloping or benching system.
The maximum allowable slopes are maximums.
Many factors can reduce the maximum allowable.
Sloping and Benching Tips
Sloping and Benching
Working in the Affected Zone
Use 45 degrees to determine the affected zone.
(Some say the Affected Zoneshould be even bigger)
Where is the Affected Zone?
Most cave-ins occur in the affected zone
(that’s where the hole is)
Cave-ins strike the Affected Zone.
Improper sloping or benching
Mass of spoil pile or equipment
Vibrations from traffic, equipment, etc.
How long the excavation is open
Rain
What are some causes of cave-ins?
Cave-ins happen in the Affected Zone...
Improper sloping or benching
Mass of spoil pile or equipment
Vibrations from traffic, equipment, etc.
How long the excavation is open
Rain
What are some causes of cave-ins?
These are the factors we can control.
Greenwood rescuers pull injured worker from trench
“The construction crew hadn’t built a trench box to prevent the sides of the trench from collapsing, so firefighters were forced to spend about an hour shoring up the sides of the ditch before they were able to give assistance. The man was rescued about 80 minutes after the accident...” These guys will not
enter an unprotected trench.
(It caved in)
Dealing with Spoil Piles
Keep any pile two feet from the excavation.
Ideally, keep them farther away.
Is the spoil pile near the hole in the ground?
If so, the maximum height should be two or three feet.
More liberty may be taken the farther the spoil pile is from the excavation.
Registered Professional Engineers (RPEs) will include the height of spoil piles in their tabulated data.
Dealing with Spoil Piles
“ When surcharge loads from stored material or equipment, operating equipment, or traffic are present...
Spoil, Equipment, and Slopes
“All simple slope excavations 20 feet or less in depth...
...shall have a maximum allowable slope of 1 ½ : 1.”
( 34 degrees )
Remember this?
The blue slope represents 1: 1 (45 degrees)
“ 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 slope. ”
Spoil, Equipment, and Slopes
Sloping the spoil pile may reducethe likelihood of cave-ins.
Walls are sloped. Spoil piles can be, too.
Dealing with Equipment
Is equipment being used near the excavation?
Probably, it’s a construction site.
But, there may be equipment not being used.
If machinery is not being used, move it away.
Are there dump trucks on site?
Are they loading or unloading materials?
If not, get them out of there ASAP.
Dealing with Equipment
Dealing with Equipment
Working in the Affected Zone
Shields and Shores
Here’s a shield.
1926.652(c)
An engineer designs it and you build it according to specs.
An engineer designs it and somebody else builds it for you.
and, then you use it according to specs.
If using shores or shields, they need to be used as recommended, advised, and specified by the manufacturer.
Have the user’s manual available.
aka “Tabulated Data”
Shield Design Options
Here’s another shield.
There’s no shield here.
The rules for working in or around shields.
Stay inside it! That’s what it’s there for.
Is there a ladder within 25 feet of any worker?that means a ladder inside the box.
No moving the shield when workers are inside it.
No digging beyond two feet under the box.
Has lateral movement been restricted?
A big chunk of soil moves a big box easily.
When the box is snug, it can’t go anywhere.
What if a shield is damaged?
It happens. In general, damaged units are not allowed.
If they’re found to be unsafe, then they’re not used.
If a shield or box is banged up...
The competent person takes a look at it.
If the CP says so, the box is back in action.
If the CP is unsure, an engineer is brought in to look at it.
The engineer will say what to do.
In the meantime, the box is not used.
Protect the protected workers, too.
Are there loose materials that could roll down into the protected area below?
Scrape away loose debris from sloped or benched walls. If it’s not there, it’s not a hazard.
Install protective barricades or nets along the face to stop or slow incoming debris.
Workers on slopes could become hazards to those below. Permit no work along the face without a system of protection (barricade, net) for those below.
Use Appendices A & C.
Not allowed when deeper than 20 feet.
Timber Shoring
Douglas fir or equivalent (with a bending strength not less than 1500 psi)
Depending on the application, you may use...
Mixed oak or equivalent (with a bending strength not less than 850 psi)
These materials can be expensive, one of the reasons timber shoring is not common.
Use Appendix D.
Not allowed when deeper than 20 feet.
Aluminum Hydraulic Shoring
MacGyver it yourself in accordance with Appendix D.
Buy a kit and use it exactly the way the manufacturer says.
Aluminum Hydraulic Shoring
If going this route, there are two options
Shields and Shores
Other Matters
1926.20(b)(4)
The employer shall permit only those employees qualified by training or experience to operate equipment and machinery.
Only qualified people operate equipment.
Get away from that!
Do an inspection before every shift.
Is that safety glass in the cab?
Wear the seat belt.
(Unless there’s no rollover protective structure)
Is there a warning or signaling system?If you can’t see the edge, use signals.Is there a reverse signal alarm?
General Safety Ideas for Equipment
Is the equipment unattended?
Set the parking brake (if equipped)
Use chocks or something to secure it.
If left overnight, make it visible with reflectors, flashing lights, or barricades.
Always lower the bucket to ground when not in use, even if temporarily.
Clear loose debris from dump trucks before you hit the highway and the DOT sees you.
General Safety Ideas for Equipment
or, visit http://www.call811.com
Mark the locations
Check local digging laws and requirements.
Call 811
Before you dig, you should...
Estimating the location of utilities (by marking) isn’t enough...
Before digging starts, an exact determination must be made.
No one else can use your marking lines, and vice versa.
Underground Utilities
APWA Uniform Color Code
1926.651(i)(2)
Excavation below the level of the base or footing of any foundation or retaining wall that could be reasonably expected to pose a hazard to employees shall not be permitted except when:
A support system, such as underpinning, is provided to ensure the safety of employees and the stability of the structure; or
The excavation is in stable rock; or
A registered professional engineer says the structure will not be affected by activity.
The RPE says activity will not pose a hazard to employees.
Undercutting and Underpinning
Don’t undercut without first supporting.
1926.651(i)(2)
Excavation below the level of the base or footing of any foundation or retaining wall that could be reasonably expected to pose a hazard to employees shall not be permitted except when:
A support system, such as underpinning, is provided to ensure the safety of employees and the stability of the structure; or
The excavation is in stable rock; or
A registered professional engineer says the structure will not be affected by activity.
The RPE says activity will not pose a hazard to employees.
Undercutting and Underpinning
A back-up plan in case the hydrant goes.
If there’s less than 19.5% oxygen in the air you’ll be breathing
or, if it’s reasonable to assume that’s the case...
... it’s time for testing.
Confined Spaces and Hazardous Atmospheres
You’re going to need protection.
PPE
Ventilation
Monitors
Rescue equipment (just in case)
If it’s hazardous in there...
Guardrails. Fences. Barricades.
Walkways or access ramps six feet or greater above next lowest level.
A pit or well six feet or greater in depth
If foliage or other visual barrier obstructs the excavation’s edges...
Then you need to barricade the area.
Fall protection while on the ground?
Other Matters
Quick Review
Mass of spoil pile or equipment
Vibrations from traffic, equipment, etc.
Improper sloping or benching
How long the excavation is open
Rain
Common causes of cave-ins
Can identify and is authorized to remedy hazards.
Is familiar with protective systems (shields, shores, and sloping configurations), soils analysis, and standard requirements.
Does lots of inspections.
Consults with RPEs in certain situations.
A competent person...
Do you have authority?
Stable Rock = stable rock
Type A: pristine clay More cohesive
Type B: angular gravel
Type C: anything less Less cohesive
Soil Types
There are many downgrading conditions.
Water, vibration, prior activity, weather, stability ...
Let the shield protect you.
Stay inside the trench box, not a few feet from it.
Proper exit should involve the ladder...
... which is inside the box,and no more than 25 feet away.
Don’t move a shield with workers inside.
Is lateral movement of the shield minimized?
Dig as little below a box as possible. Two feet is the maximum allowed by OSHA.
The maximum allowable sloping configurations are the maximums.
Any number of reasons could reduce them.
The configurations apply above shields, too.
Benching isn’t allowed in Type C soil.
Anything deeper than 20 feet must be designed by a Registered Professional Engineer (RPE).
Simple Slopes and Benches
Quick Review
Call 811 – Know what’s belowhttp://www.call811.com/
Safety and Health Topics: Trenching and Excavationhttp://www.osha.gov/SLTC/trenchingexcavation/construction.html
OSHA Construction eTool: Trenching and Excavationhttp://www.osha.gov/SLTC/etools/construction/trenching/mainpage.html
Trench Safety Version 4.0http://www.trenchsafety.org/
Excavation1926 Subpart P for construction
www.montanasafety.com
Maurizio DelcaroOccupational Health & Safety SpecialistThat’s it!
Questions, Comments?
Thanks for attending!
