DEPARTMENT OF LABOR AND ECONOMIC OPPORTUNITY  
DIRECTOR'S OFFICE  
CONSTRUCTION SAFETY AND HEALTH STANDARD  
(By authority conferred on the director of the department of labor and economic  
opportunity by sections 19 and 21 of the Michigan occupational safety and health act,  
1974 PA 154, MCL 408.1019 and 408.1021, and Executive Reorganization Order Nos.  
1996-2, 2003-1, 2008-4, 2011-4, and 2019-3, MCL 445.2001, 445.2011, 445.2025,  
445.2030, and 125.1998)  
PART 9. EXCAVATION, TRENCHING, AND SHORING  
R 408.40901 Scope and referenced standards.  
Rule 901. (1) This part pertains to the digging of excavations and trenches which an  
employee is required to enter and the supporting systems used on construction  
operations.  
(2) The following Michigan occupational safety and health (MIOSHA) standards are  
referenced in these rules:  
(a) Construction Safety and Health Standard Part 21. “Guarding of Walking and  
Working Areas,” R 408.42101 to R 408.42160.  
(b) Construction Safety Standard Part 45. “Fall Protection,” R 408.44501 to R  
408.44502.  
(3) Up to 5 copies of the standards listed in subrule (2) of this rule may be obtained  
at no charge from the Department of Labor and Economic Opportunity, MIOSHA,  
Standards and FOIA Section, 530 West Allegan Street, P.O. Box 30645, Lansing,  
Michigan, 48909-8145 or via the internet at the following website:  
www.michigan.gov/mioshastandards. For quantities greater than 5, the cost, as of the  
time of adoption of these rules, is 4 cents per page.  
History: 1979 AC; 2023 MR 24, Eff. Jan. 3, 2024.  
R 408.40925 Definitions A to Q.  
Rule 925. (1) "Angle of repose" means the maximum permissible slope as  
determined by table 1.  
(2) “Benching” means a method of protecting employees from cave-ins by  
excavating the sides of an excavation to form 1 or a series of horizontal levels or steps,  
usually with vertical or near-vertical surfaces between levels.  
(3) "Braces" or "struts" means the horizontal cross members of a shoring system  
that bear against the uprights or stringers.  
(4) “Cave-in” means the separation of a mass of soil or rock material from the side  
of an excavation, or the loss of soil from under a trench shield or support system, and its  
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sudden movement into the excavation, either by falling or sliding, in sufficient quantity  
so that it could entrap, bury, or otherwise injure and immobilize a person.  
(5) “Competent person” means an individual who is capable of identifying existing  
and predictable hazards in the surroundings or working conditions which are unsanitary,  
hazardous, or dangerous to employees, and who has authorization to take prompt  
corrective measures to eliminate them.  
(6) "Excavation" means any man-made cut, cavity, trench, or depression in the  
earth's surface, including its sides, walls, or faces, formed by earth removal.  
(7) "Hazardous atmosphere" means an atmosphere which by reason of being any  
of the following, may cause death, illness, or injury:  
(a) Explosive.  
(b) Flammable.  
(c) Poisonous.  
(d) Corrosive.  
(e) Oxidizing.  
(f) Irritating.  
(g) Oxygen deficient.  
(h) Toxic.  
(i) Otherwise harmful.  
(8) "Kickout" means the accidental release or failure of a stringer or brace.  
(9) “Protective system” means a method of protecting employees from cave-ins,  
from material that could fall or roll from an excavation face or into an excavation, or  
from the collapse of adjacent structures. Protective systems include support systems,  
sloping and benching systems, shield systems, and other systems that provide the  
necessary protection.  
(10) "Qualified person" means an individual who, by possession of a recognized  
degree or certificate of professional standing, or who, by extensive knowledge, training,  
and experience, has successfully demonstrated the ability to solve or resolve problems  
relating to the subject matter and work.  
(11) “Ramp” means an inclined walking or working surface that is used to gain  
access to 1 point from another and is constructed from earth or from structural materials  
such as steel or wood.  
(12) “Registered professional engineer” means a person who is registered as a  
professional engineer in the state where the work is to be performed. However, a  
professional engineer, registered in any state is deemed to be a registered professional  
engineer within the meaning of this standard when approving designs for manufactured  
protective systems or tabulated data to be used in interstate commerce.  
History: 1979 AC; 1988 AACS; 1993 AACS; 2023 MR 24, Eff. Jan. 3, 2024.  
R 408.40926 Definitions; S.  
Rule 926. (1) “Sheeting” means the members of a shoring system that retain the  
earth in position and in turn are supported by other members of the shoring system.  
(2) "Sheet piling" means a continuous row of timber or steel piles driven in close  
contact to provide a tight wall to resist lateral pressure of water, adjacent earth, or other  
materials.  
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(3) “Shield” or “shield system” means a structure that is able to withstand the forces  
imposed on it by a cave-in and thereby protect employees within the structure. Shields  
can be permanent structures or can be designed to be portable and moved along as work  
progresses. Additionally, shields can be either premanufactured or job-built in accordance  
with R 408.40932, R 408.40942, R 408.40943, R 408.40945, and R 408.40953. Shields  
used in trenches are usually referred to as trench boxes or trench shields.  
(4) “Shoring” or “shoring system” means a structure such as a metal hydraulic,  
mechanical, or timber shoring system that supports the sides of an excavation and which  
is designed to prevent cave-ins.  
(5) "Sides" sometimes called faces or walls, mean the vertical or inclined earth  
surfaces formed as a result of excavation work.  
(6) "Slope" means the acute angle formed by the side of a trench or excavation  
and the horizontal plane.  
(7) "Soil" means any of the following:  
(a) "Clay" means a very fine textured soil that derives its resistance to  
displacement from cohesion and may be:  
(i) "Soft clay" means a clay-type soil that has an unconfined strength of less than  
1.0 ton per square foot.  
(ii) "Medium clay" or "plastic" means a clay-type soil that has a minimum  
unconfined strength of 1.0 ton per square foot.  
(iii) "Firm soil" means a clay-type soil that is resistant to forces causing rupture or  
displacement. A firm clay has a minimum unconfined strength of 1.5 tons per square  
foot.  
(iv) "Stiff clay" means a clay-type soil that is very resistant to forces causing  
rupture or displacement. A stiff clay has a minimum unconfined strength of 2.5 tons per  
square foot.  
(b) "Fill" means a manmade soil condition that may be constructed of any type of  
soil or combination thereof.  
(c) "Granular soil" means a coarse grained soil that does not possess cohesion  
but derives its strength from internal friction.  
(d) "Organic soil" means a soil that contains significant amounts of peat, muck, or  
marl.  
(e) "Running soil" means any type of soil that has insufficient strength to stand  
unsupported. Running soil tends to run or slough into the excavation as the excavation is  
being dug.  
(8) "Stringers" mean the horizontal members of a trench shoring system whose sides  
bear against the uprights or earth.  
(9) “Structural ramp” means a ramp built of steel or wood, usually used for vehicle  
access. Ramps made of soil or rock are not considered structural ramps.  
(10) “Support system” means a structure such as underpinning, bracing, or shoring,  
which provides support to an adjacent structure, underground installation, or the sides of  
an excavation.  
History: 1979 AC; 2023 MR 24, Eff. Jan. 3, 2024.  
R 408.40927 Definitions; T, U.  
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Rule 927. (1) “Tabulated data” means tables and charts approved by a registered  
professional engineer and used to design and construct a protective system.  
(2) "Toe of slope" means the point at which the side of an excavation intersects the  
lowest level of the excavation.  
(3) "Trench" means an excavation having a depth greater than its width measured  
at the bottom.  
(4) "Trench jack" means a screw or hydraulic jack used as a brace in a trench  
shoring system.  
(5) "Trench shield," sometimes called a trench box, means a trench shoring  
system composed of steel plates and bracing, welded or bolted together, which can be  
moved along as work progresses.  
(6) "Uprights" mean the vertical members of a trench shoring system.  
History: 1979 AC; 2023 MR 24, Eff. Jan. 3, 2024.  
R 408.40931 Locating utility lines.  
Rule 931. (1) An employer shall not excavate in  
a
street, highway, public  
place, a private easement of a public utility, or near the location of a public utility  
facility owned, maintained, or installed on a  
customer's premises, without having first ascertained the location of  
underground facilities of a public utility in the proposed area of excavation.  
all  
(2) Upon receiving the information from the public utility, an employer shall  
exercise reasonable care when working in close proximity to the underground  
facilities of any public utility. If the facilities are to be exposed, or are likely to be  
exposed, only hand digging shall be employed in such circumstances and such support,  
as may be reasonably necessary for protection of the facilities, shall be provided  
in and near the construction area.  
(3) When any contact with, or damage to, any pipe, cable, or its protective  
coating, or any other underground facility of a public utility  
occurs, the public utility shall be notified immediately by the employer responsible  
for operations causing the damage. If an energized electrical cable is severed, an  
energized conductor is exposed, or dangerous fluids or gases are escaping from a broken  
line, the employer shall evacuate the employees from the immediate area while  
awaiting the arrival of the public utility personnel.  
History: 1979 AC.  
R 408.40932 Excavation; consideration of soil types; water; slide hazards.  
Rule 932. (1) If different textured soils are encountered in the side of an excavation,  
each soil type of the excavation shall be cut to the proper angle of repose, except that the  
slope shall not steepen between the toe of the slope and the ground level where soft clay  
or running soil is encountered in the lower cut.  
(2) An employee shall not work in an excavation in which there is accumulated  
water or in which water is accumulating unless precautions have been taken to protect  
employees against the hazards posed by water accumulation. The precautions  
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necessary to protect employees adequately vary with each situation, but may include  
special supportor shield systems to protect from cave-ins, water removal to control the  
level of accumulating water, or the use of a safety harness and lifeline.  
(3) If water is controlled or prevented from accumulating by the use of water  
removalequipment, the water removal equipment and operation shall be monitored by a  
competent person or a monitoring system to ensure that the equipment is properly  
operated.  
(4) An ongoing inspection of an excavation or trench shall be made by a competent  
person. After every rainstorm or other hazard-producing occurrence, an inspection shall  
be made by a competent person for evidence of possible slides or cave-ins. Where these  
conditions are found, all work shall cease until additional precautions, such as additional  
shoring or reducing the slope, have been accomplished.  
(5) When installed forms, walls, or similar structures create a trench between the  
form, wall, or structure and the side of the excavation, an employer shall comply with the  
provisions of R 408.40941 to R 408.40944.  
History: 1979 AC; 1993 AACS; 2013 AACS; 2023 MR 24, Eff. Jan. 3, 2024.  
R 408.40933 Excavation; obstructions; retaining materials; egress; guarding;  
heavy equipment.  
Rule 933. (1) A tree, boulder, rock fragment, or other obstruction whose movement  
could cause injury to an employee shall be removed or supported.  
(2) An excavation that an employee is required to enter shall have excavated and  
other material stored and retained not less than 2 feet from the excavation edge.  
(3) When mobile equipment is utilized or permitted adjacent to an excavation where  
the operator’s vision is restricted, stop logs or barricades shall be utilized or a signal  
person shall be used.  
(4) An excavation 48 or more inches in depth and occupied by an employee shall be  
provided with either a ladder extending not less than 3 feet above the top as a means of  
access or with a ramp meeting the requirements of subrule (5) of this rule. Lateral travel  
along the wall of a trench to a ladder or other means of egress shall not exceed 25 feet.  
(5) An earth ramp may be used in place of a ladder if it meets all of the following  
requirements:  
(a) The ramp material shall be stable.  
(b) The sides of the excavation above the ramp shall be maintained to the angle of  
repose or sheeted or shored along the means of egress.  
(c) The degree of angle of the ramp shall not be more than 45 degrees.  
(d) Vertical height between the floor of the trench and the toe of the ramp  
shall not exceed 30 inches.  
(6) Structural ramps that are used solely by employees as a means of access or  
egress from excavations shall be designed by a competent person. Structural ramps used  
for access or egress of equipment shall be designed by a competent person qualified in  
structural design and shall be constructed in accordance with the design.  
(7) Ramps and runways constructed of 2 or more structural members shall have the  
structural members connected together to prevent displacement.  
(8) Structural members used for ramps and runways shall be of uniform thickness.  
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(9) Cleats or other appropriate means used to connect runway structural members  
shall be attached to the bottom of the runway or shall be attached in a manner to prevent  
tripping.  
(10) Structural ramps used in lieu of steps shall be provided with cleats or other  
surface treatments on the top surface to prevent slipping.  
History: 1979 AC; 2013 AACS; 2023 MR 24, Eff. Jan. 3, 2024.  
R 408.40934 Hazardous atmospheres; testing and controls.  
Rule 934. To prevent exposure to harmful levels of  
atmospheric  
contaminants and to assure acceptable atmospheric conditions, all of the following  
requirements shall apply:  
(a) Where an oxygen deficiency (an atmosphere that contains less than 19.5%  
oxygen) or a hazardous atmosphere exists, such as in excavations in  
areas where hazardous substances are stored nearby, the atmosphere in  
the  
excavation shall be tested before employees enter excavations that are more than 4  
feet (1.22 m) deep.  
(b) Precautions shall be taken to prevent employee exposure to atmospheres  
that contain less than 19.5% oxygen and any other hazardous atmosphere. These  
precautions include providing  
proper  
respiratory protection or ventilation in  
accordance with the requirements of this part.  
(c) Precautions shall be taken, such as providing ventilation, to prevent  
employee exposure to an atmosphere that contains a concentration of a flammable gas in  
excess of 20% of the lower flammable limit of the gas.  
(d) When controls are used that are intended to reduce the level of atmospheric  
contaminants to acceptable levels, testing shall be conducted as often as necessary to  
ensure that the atmosphere remains safe.  
History: 1993 AACS.  
R 408.40941 Excavation; angle of repose.  
Rule 941. (1) The side of an excavation more than 5 feet deep shall be sloped as  
prescribed in table 1, unless supported as prescribed in this part.  
(2) An excavation less than 5 feet in depth shall also be effectively protected  
when examination of the ground indicates hazardous earth movement may be expected.  
TABLE 1  
MAXIMUM ALLOWABLE ANGLE OF REPOSE FOR THE SIDE OF AN  
EXCAVATION IN EXCESS OF 5' DEPTH  
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History: 1979 AC; 2013 AACS; 2023 MR 24, Eff. Jan. 3, 2024.  
R 408.40942 Supporting systems; angle of repose; tie backs; sheeting;  
additional bracing.  
Rule 942. (1) The angle of repose and the design of the supporting system for a  
side of an excavation shall be based on the evaluation of all of the following factors:  
(a) Depth of cut and type of soil.  
(b) Possible variation in the water content of the material while the excavation is  
open.  
(c) Anticipated changes in the material due to exposure to air, sun, water, or  
freezing temperatures.  
(d) Load imposed by structures, equipment, overlying material, or stored material.  
(e) Vibration from traffic, equipment, or blasting.  
(2) A support system shall be designed by a qualified person. The design of the  
support system shall be maintained at the jobsite. Changes from the design of the  
support system shall be approved by a qualified person.  
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(3) Tie rods and other forms of tie backs used to restrain the top of sheeting shall  
be anchored a minimum of 10 feet. The measurement to the anchor point shall start at  
the intersection of an angle of repose with the surface of the soil retained. The tie back  
and anchor shall be capable of restraining any pressure exerted on the system.  
(4) When sheeting or sheet piling is used, pressures due to existing ground water  
conditions shall be considered in the design. Sheet piling shall be driven to the  
predetermined depth set forth in the required design. Changes from the design shall be  
approved by the designer of the support system.  
(5) Materials used for a supporting system shall be in good serviceable condition.  
When timbers are used, they shall be sound and free of large or loose knots.  
(6) A supporting system shall include additional bracing approved by the designer  
of the support system when the sides of excavations are cut adjacent to a previous  
known excavation or a known fill, particularly when the separation between the  
previous excavation and the new excavation is less than the depth of the excavation.  
(7) Sheeting shall be braced or anchored at the bottom and along the vertical plane  
to prevent lateral movement.  
(8) Protective systems for use in excavations more than 20 feet in depth must be  
designed by a registered professional engineer.  
History: 1979 AC; 2023 MR 24, Eff. Jan. 3, 2024.  
R 408.40943 Additional requirements for trench support systems.  
Rule 943. (1) Members of support systems shall be securely connected together to  
prevent sliding, falling, kickouts, or other predictable failure.  
(2) The backfilling and the removal of a support system for a trench shall progress  
together from the bottom of the trench. In unstable or running soil, the jacks and  
braces shall be removed from above the trench after employees have cleared the trench.  
(3) The excavation of material to a level that is not more than 2 feet, .61 m, below  
the bottom of the members of a support system shall be permitted, but only if the  
system is designed to resist the forces calculated for the full depth of the trench and  
if there are no indications, while the trench is open, of a possible loss of soil from  
behind or below the bottom of the support system.  
(4) The installation of a support system shall be closely coordinated with the  
excavation of trenches.  
(5) Support systems shall be installed and removed in a manner that protects  
employees from cave-ins, structural collapses, or from being struck by members of the  
support system.  
(6) Individual members of support systems shall not be subjected to loads exceeding  
those which those members were designed to withstand.  
(7) Before temporary removal of individual members begins, additional precautions  
shall be taken to ensure the safety of employees, such as installing other structural  
members to carry the loads imposed on the support system.  
History: 1979 AC; 1993 AACS; 2023 MR 24, Eff. Jan. 3, 2024.  
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R 408.40944 Benching and sloping.  
Rule 944. (1) The angle of repose shall be flattened when an excavation has water  
conditions, silty materials, loose boulders, or areas where erosion, deep frost action,  
or slide planes appear.  
(2) When benching the side of an excavation, the vertical rise shall not be more than  
5 feet and the step back shall extend at least to the angle of repose as required by table  
1.  
(3) When benching a side of a trench, the height of the lower bench shall not be  
more than the lesser of 5 feet or width of the trench measured at the bottom.  
(4) An employee shall not be permitted to work on sloped or benched  
excavations at levels above another employee, except when an employee at the lower  
level is protected from the hazard of falling, rolling, or sliding material or  
equipment.  
History: 1979 AC; 1993 AACS.  
R 408.40945 Trenching boxes and shields.  
Rule 945. (1) Portable trench boxes or sliding trench shields may be used for the  
protection of personnel in place of a shoring system or sloping. Where such trench  
boxes or shields are used, they shall be designed, constructed, and maintained in a  
manner that provides protection equal to or greater than the sheeting or shoring required  
for the trench.  
(2) The use of benching in conjunction with a portable trench box is permitted  
when the toe of the trench box is not more than 2 feet above the trench bottom, but only  
if the trench box is designed to resist the forces calculated for the full depth of the  
trench and if there are no indications, while the trench is open, of a possible cave-in  
below the bottom of the trench box.  
(3) An employee shall not be allowed in shields when shields are being installed,  
removed, or moved vertically.  
(4) Shield systems shall not be subjected to loads exceeding those which the system  
was designed to withstand.  
(5) Shields shall be installed in a manner to restrict lateral or other hazardous  
movement of the shield in the event of the application of sudden lateral loads.  
(6) Employees shall be protected from the hazard of cave-ins when entering or  
exiting the areas protected by shields.  
History: 1979 AC; 1993 AACS; 2023 MR 24, Eff. Jan. 3, 2024.  
R 408.40946 Rescinded.  
History: 1979 AC; 1982 AACS; 1988 AACS; 2013 AACS.  
R 408.40951 Walkways, sidewalks, roadways.  
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Rule 951. (1) Sidewalks, pavements, and appurtenant structure shall not be  
undermined unless a support system or another method of protection is provided to  
protect employees from the possible collapse of such structures.  
(2) If an employee or equipment is required or permitted to cross a trench or ditch, a  
walkway, runway, ramp, or bridge shall be provided and shall have a designed capacity  
of not less than 3 times the imposed load. A guardrail prescribed by the provisions of  
Construction Safety and Health Standard Part 21. Guarding of Walking and Working  
Areas, R 408.421 to R 408.42160 and Construction Safety Standard Part 45. Fall  
Protection, R 408.42101 and R 408.44501, shall be provided.  
History: 1979 AC; 1993 AACS; 1996 AACS; 2013 AACS; 2023 MR 24, Eff. Jan. 3, 2024.  
R 408.40952 Rescinded.  
History: 1979 AC; 2013 AACS.  
R 408.40953 Adjacent structures; protection; design; inspection of shoring,  
bracing, and underpinning.  
Rule 953. (1) A structure that is adjacent to an excavation or trench below the  
level of the base or footing of any foundation or retaining wall shall be protected against  
settlement, lateral movement, undermining, or washout.  
(2) Before the excavation begins, the design of the protection used shall be set  
forth by a qualified person who is knowledgeable in the subject area.  
(3) The shoring, bracing, and underpinning shall be inspected daily or more often, as  
conditions warrant, by a competent person.  
(4) Where the stability of adjoining buildings, walls, or other structures is  
endangered by excavation operations, support systems such as shoring, bracing, or  
underpinning shall be provided to ensure the stability of such structures for the protection  
of employees.  
(5) 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 1 of the following applies:  
(a) A support system, such as underpinning, is provided to ensure the safety of  
employees and the stability of the structure.  
(b) The excavation is in stable rock.  
(c) A registered professional engineer has approved the determination that the  
structure is sufficiently removed from the excavation so as to be unaffected by the  
excavation activity.  
(d) A registered professional engineer has approved the determination that such  
excavation work will not pose a hazard to employees.  
History: 1979 AC; 1993 AACS; 2023 MR 24, Eff. Jan. 3, 2024.  
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;