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Confined Spaces in Construction and Other Related Provisions
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CHAPTER 140
VIRGINIA CONFINED SPACE STANDARD FOR THE CONSTRUCTION INDUSTRY

16VAC25-140-10. Definitions. (Repealed.)

Note: The following standard is unique for the enforcement of occupational safety and health within the Commonwealth of Virginia under the jurisdiction of the VOSH Program. There is no federal OSHA standard counterpart.

The following words and terms, when used in this chapter, shall have the following meanings, unless the context clearly indicates otherwise:

"Attendant" means an individual with no other duties assigned to remain immediately outside the entrance to the confined space and who may render assistance as needed to employees inside the space.

"Blind" or "blinding" or "blanking" means the absolute closure of a pipe, line or duct, to prevent passage of any material (e.g., by fastening a solid plate or "cap" across the pipe).

"Calibration" or "Recalibration" means a laboratory or bench-top re-setting of alarm points, spans and zeros, if applicable, according to manufacturer's specifications. "Calibration" or "recalibration" shall be conducted by a factory authorized service center, a factory trained technician, or a trained company technician.

"Confined space" means any space not intended for continuous employee occupancy, having a limited means of egress, and which is also subject to either the accumulation of an actual or potentially hazardous atmosphere as defined in this subsection or a potential for engulfment as defined in this subsection. Confined spaces generally include, but are not limited to, storage tanks, process vessels, bins, boilers, ventilation or exhaust ducts, sewers, manholes, underground utility vaults, acid tanks, digesters, ovens, kiers, pulpers, tunnels, and pipelines. Open top spaces more than 4 feet in depth such as pits, tubs, vaults and vessels may also be confined spaces if the three criteria above are met.

"Engulfment" means the surrounding and effective capture of a person by finely divided particulate matter or a liquid. There is a potential for engulfment when such particulate matter or liquid exists in a sufficient quantity or at a sufficient pressure to surround a person before normal exit can be effected.

"Entrant" means any employee who enters a confined space.

"Entry" means any action resulting in any part of the employee's face breaking the plane of any opening of the confined space, and includes any ensuing work activities inside the confined space.

"Entry permit" means the employer's written authorization for employee entry into a confined space under defined conditions for a stated purpose during a specified time.

"Field checked" means a method of checking an instrument for a proper response in the field. It is a check of the instrument's functionality and is a pass-fail or go/no-go check. When an adequate response is not obtained then the equipment should be removed from service and adjusted or repaired by a factory authorized service center, or a factory trained technician, or a trained company technician.

"Ground-fault circuit interrupter" means a device whose function is to interrupt the electric circuit to the load when a fault current to ground exceeds a predetermined value that is less than that required to operate the overcurrent protective device of the supply circuit.

"Hazardous atmosphere" means an atmosphere presenting a potential for death, disablement, injury, or acute illness from one or more of the following causes:

(i) A flammable gas, vapor, or mist in excess of 10% of its lower explosive limit (LEL);

(ii) An oxygen deficient atmosphere containing less than 19.5% oxygen by volume or an oxygen enriched atmosphere containing more than 23% oxygen by volume;

(iii) An atmospheric concentration of any substance listed in Subpart Z of 29 CFR Part 1910 standards above the listed numerical value of the permissible exposure limit (PEL); or

(iv) A condition immediately dangerous to life or health as defined in this subsection.

"Immediately dangerous to life or health (IDLH)" means any condition that poses an immediate threat to life, or which is likely to result in acute or immediately severe health effects. See Appendix A for concentrations at which several chemicals exhibit IDLH effects.

"Immediate severe health effects" means that an acute clinical sign of serious, exposure-related reaction is manifested within 72 hours of exposure.

"Lockout or tagging" means placing locks or tags on the energy isolating device in accordance with 16VAC25-140-30 B of this chapter. Tags shall indicate that the energy-isolated device shall not be operated until the removal of the tag.

"Qualified person" means a person who is trained to recognize the hazards of the confined space and how to evaluate those anticipated hazards and shall be capable of specifying necessary control measures to assure worker safety. The employer may designate an employee as employer representative for the purpose of assuring safe confined space entry procedures and practices at a specific site. The qualified person may also be the entrant when permissible according to 16VAC25-140-50 A of this chapter.

"Rescue team" means those persons whom the employer has designated prior to any confined space entry to perform rescues from confined spaces. A rescue team may consist of outside emergency personnel, provided the training requirements of 16VAC25-140-70 A 2 of this chapter have been met.

"Retrieval line" means a line or rope secured at one end to a worker's safety belt, chest or body harness, or wristlets with the other end secured to an anchor point or lifting device located outside the entry portal. The anchor point shall not be a motor vehicle. Retrieval lines must be of sufficient strength to remove an entrant when necessary.

"Zero mechanical state" means that the mechanical potential energy of all portions of the machine or equipment is set so that the opening of the pipes, tubes, hoses or actuation of any valve, lever, or button, will not produce a movement which could cause injury.

16VAC25-140-20. Scope and application. (Repealed.)

A. This section prescribes basic mandatory practices and procedures which employers must establish and use for employee entry into and work within confined spaces.

B. This section applies to all employers with employees covered by Virginia Standards for Construction Industry (29 CFR Part 1926) except for employers with employees covered by the telecommunication standards in 16VAC25-70-10 et seq. and 16VAC25-90-1910.268.

C. Natural Gas Companies governed by the Federal Pipeline Safety Act which have confined space entry procedures approved by and in accordance with guidelines established by the Virginia State Corporation Commission shall be exempt from the requirements of this chapter.

16VAC25-140-30. Preparation. (Repealed.)

Entry into a confined space shall not be made unless the qualified person has assured that the following procedures have first been completed.

A. All pumps or lines which may convey flammable, injurious, or incapacitating substances into a space shall be disconnected, blinded, double blocked and bled, or effectively isolated by other means to prevent the development of dangerous levels of air contamination or oxygen deficiency within the space. The closing of valves alone, or the closing of valves and locking or tagging them, is not considered effective protection. The disconnection or blind shall be so located or done in such a manner that inadvertent reconnection of the line or removal of the blind are effectively prevented.

1. This does not apply to public utility gas distribution systems.

2. This does not require blocking of all laterals to sewers or storm drains unless experience or knowledge of industrial use indicates materials resulting in dangerous air contamination may be dumped into an occupied sewer.

B. All fixed mechanical devices and equipment that are capable of causing injury shall be placed at zero mechanical state (ZMS). Electrical equipment, excluding lighting, shall be locked out in the open (off) position with a key-type padlock except in cases where locking is impossible; in such cases equipment shall be properly tagged in accordance with 16VAC25-90-1910.145(f). The key shall remain with the person working inside the confined space. Installations under the exclusive control of electric utilities and companies performing the same functions as electric utilities on their own property for the purpose of communication, or metering, or for the generation, control, transformation, transmission, and distribution of electric energy located in buildings used exclusively by utilities for such purposes or located outdoors on property owned or leased by the utility or such companies or on public highways, streets, roads, etc., or outdoors by established rights on private property, are exempt from the requirements of this paragraph.

C. All confined spaces shall be emptied, flushed, or otherwise purged of flammable, injurious, or incapacitating substances to the extent feasible. Initial cleaning shall be done from outside the confined space to the extent feasible.

D. Where the existence of a hazardous atmosphere is demonstrated by tests performed by the qualified person, the confined space shall be mechanically ventilated until the concentration of the hazardous substances is reduced to a safe level, and ventilation shall be continued as long as the recurrence of the hazards is possible or appropriate personal protective equipment, as defined in Subpart E of the Virginia Standards for Construction Industry (16VAC25-175-1926), shall be used by all employees during entry.

16VAC25-140-40. Atmospheric testing. (Repealed.)

A. The qualified person shall assure that each confined space into which an employee may be required to enter is tested immediately prior to entry by a qualified person using direct reading instruments with remote sampling capacity for the following conditions:

1. Oxygen level;

2. Potential flammable hazard; and

3. Toxic materials known or expected to be present.

The testing of the atmosphere for a particular toxic material is not necessary where the presence of that material is known by virtue of a previous test and appropriate personal protective equipment to protect against that material is utilized.

B. When an attendant has been assigned, as prescribed by 16VAC25-140-50 A, a qualified person shall perform atmospheric testing during occupancy at intervals dependent on the possibility of changing conditions, but in no case less frequently than hourly. Atmospheric test results must be recorded on the permit at least hourly in accordance with 16VAC25-140-60 B.

C. When a non-attendant entry is permitted, as allowed by 16VAC25-140-50 A, at least one entrant shall wear a continuous monitoring device equipped with an alarm and capable of evaluating oxygen concentrations and combustible gas concentrations in the confined space. When large confined spaces are entered, a sufficient number of monitoring devices shall be either worn or located in the work area to adequately monitor the atmosphere. The qualified person shall assess the need for mechanical ventilation in all confined spaces in accordance with the written permit system.

D. Each atmospheric testing instrument shall be calibrated according to the manufacturer's instructions or, if no manufacturer's specifications exist, at least yearly, and field checked immediately prior to its use. Instruments which are out of calibration or fail a field check cannot be used until they are properly calibrated.

16VAC25-140-50. Attendants and rescue teams. (Repealed.)

A. The qualified person shall evaluate each confined space that an employee may be required to enter by identifying and evaluating the hazards and potential hazards of that space. The qualified person then may allow an employee to make an unaccompanied, non-attendant entry into a confined space which has no potential for engulfment or IDLH atmosphere, and only low potential for hazardous atmosphere, provided the requirements of 16VAC25-140-40 C are met.

B. An attendant shall be stationed immediately outside every confined space which has been found to have an IDLH atmosphere, a hazardous atmosphere or a potential for engulfment. The attendant shall be trained as directed by 16VAC25-140-70 A 2, be within sight or call of the entrant, and have the means available to summon assistance.

C. Rescue teams shall be available where the confined space has been found to have an IDLH atmosphere, a hazardous atmosphere or a potential for engulfment.

16VAC25-140-60. Permit systems. (Repealed.)

A. The employer shall develop and implement a written entry permit system for all confined space entries which includes a written permit procedure that provides the following minimum information:

1. The minimum acceptable environmental conditions which are acceptable to the employer for entry and work in the confined space;

2. A record of atmospheric test results conducted prior to entry and at least hourly thereafter when an attendant is required;

3. The last calibration dates for the oxygen detector and combustible gas indicator being used;

4. The signature of the qualified person responsible for securing the permit and reviewing conditions prior to entry;

5. A written description of the location and type of work to be done;

6. Each permit shall be dated and carry an expiration time of not more than 12 hours; the permit may be extended for another 12-hour period pending recertification of acceptable conditions.

B. Entry permit forms shall be retained until the corresponding entry has been successfully completed.

16VAC25-140-70. Training. (Repealed.)

A. The employer shall inform his employees of the hazards of working in confined spaces by providing specific training to employees before they may be authorized to enter a confined space.

1. General. The employer shall assure that the qualified person and all employees who may be required to enter a confined space have received training covering the following subjects:

a. Hazard recognition;

b. Use of respiratory protection equipment if the use of such equipment will be required. Training requirements are specified in 16VAC25-90-1910.134;

c. Use of atmospheric testing devices for those employees required to perform atmospheric tests. Training shall cover field checks as specified by the manufacturer, normal use, and specific limitations of the equipment;

d. Lockout and tagging procedures;

e. Use of special equipment and tools;

f. Emergency and rescue methods and procedures.

2. Rescue teams. Rescue teams shall be trained to use the equipment they may need to perform rescue functions assigned to them.

a. At least annually rescue teams shall practice removing victims through openings and portals of the same size, configuration and accessibility as those of spaces from which an actual rescue could be required.

b. The attendant or at least one member of each rescue team shall hold current certification in basic first aid and CPR (Cardio-Pulmonary Resuscitation).

B. The employer shall maintain the records of the most recent training program conducted. These records shall include the dates of the training program, the instructors of the training program, and the employees to whom the training was given.

16VAC25-140-80. Special equipment and tools. (Repealed.)

A. No sources of ignition shall be introduced into a confined space until the implementation of the appropriate provision of this section has ensured that dangerous air contamination due to flammable or explosive substances does not exist.

B. All electrical cords, tools, and equipment shall be inspected for visually detectable defects before use in a confined space. In the absence of low voltage circuits and equipment or double insulated tools, equipment shall be of the heavy duty insulation type or ground-fault circuit interrupters shall be used. Temporary lighting shall conform with 16VAC25-175-1926.405(a)(2)(ii)(G).

C. No fan or other equipment used for removing flammable gases or vapors shall create an ignition hazard.

D. Cylinders of compressed gases shall never be taken into a confined space, and shall be turned off at the cylinder valve when not in use. When to be left unattended the torch and hose shall be removed from the confined space. Open end fuel gas and oxygen hoses shall be immediately removed from enclosed spaces when they are disconnected from the torch or other gas-consuming device.

Exempt from this rule are cylinders that are part of self-contained breathing apparatus or resuscitation equipment.

16VAC25-140-90. Tripods, safety harnesses, retrieval lines, and respiratory protection. (Repealed.)

A. Where the existence of an IDLH atmosphere, a hazardous atmosphere or potential for engulfment has been demonstrated by the qualified person, the following requirements shall also apply:

1. An appropriate retrieval device with retrieval line shall be used by any entrants, except where the retrieval lines themselves could cause a hazard because of structures, equipment, or becoming entangled with other lines inside the confined space. Where a retrieval line is used, the free end of the retrieval line shall be secured outside the entry opening either by another person holding the line or by securing it in some other manner.

2. When entry is made through a top opening, a hoisting device such as a tripod shall be provided for lifting employees out of the space.

B. When a person is required to enter a confined space which has either an IDLH atmosphere or a hazardous atmosphere there shall be either a positive-pressure self-contained breathing apparatus or a combination positive-pressure air-line respirator with an auxiliary self-contained air supply immediately outside the entrance to the confined space.

C. When a person must enter a confined space which contains either an IDLH atmosphere or a hazardous atmosphere without a retrieval line attached, then each entrant shall be supplied with and wear a MSHA/NIOSH approved positive pressure self-contained breathing apparatus.

APPENDIX A. (Repealed.)

Concentrations at which some common substances exhibit immediately dangerous to life or health (IDLH) effects.

Appendix A is a non-mandatory appendix. According to The National Institute for Occupational Safety and Health (NIOSH) the levels listed below represent a maximum concentration from which one could escape within 30 minutes without any escape-impairing symptoms or any irreversible health effects. These levels were published by NIOSH in September 1985 and are subject to frequent change. This list is not meant to be all inclusive but rather is meant to list some of the more frequently encountered chemicals in confined spaces.

Appendix A

CHEMICAL NAME

IDLH LEVELS*

Ammonia

500 ppm

Benzene

2,000 ppm

Butadiene

20,000 ppm

2 - Butanone

3,000 ppm

Carbon dioxide

50,000 ppm

Carbon monoxide

1,500 ppm

Carbon tetrachloride

300 ppm

Chlorine

25 ppm

Chlorobromomethane

5,000 ppm

Chloroform

1,000 ppm

Cresol

250 ppm

Cyclohexane

10,000 ppm

Dichlorodifluoromethane

50,000 ppm

Dichloromonofluoromethane

50,000 ppm

Ethyl acetate

10,000 ppm

Fluorotrichloromethane

10,000 ppm

Heptane

4,250 ppm

Hexane

5,000 ppm

2 - Hexanone

5,000 ppm

Hydrogen chloride

100 ppm

Hydrogen sulfide

300 ppm

Isopropyl alcohol

20,000 ppm

Liquefied petroleum gas

19,000 ppm

Methyl alcohol

25,000 ppm

Methyl cellosolve

2,000 ppm

Methyl cellosolve acetate

4,500 ppm

Methyl chloroform

1,000 ppm

Methylene chloride

5,000 ppm

Nitric oxide

100 ppm

Nitrogen dioxide

50 ppm

Octane

3,750 ppm

Ozone

10 ppm

Pentane

5,000 ppm

Petroleum distillates mixture

10,000 ppm

Phenol

100 ppm

Phosgene

2 ppm

Propane

20,000 ppm

Sodium hydroxide

200 mg/M3

Stoddard solvent

5,000 ppm

Styrene

5,000 ppm

Sulfur dioxide

100 ppm

1, 1, 2, 2, - Tetrachloro-1, 2 - difluroethane

15,000 ppm

Toluene

2,000 ppm

Toluene-2, 4-diisocyanate

10 ppm

Trifluoromonobromomethane

50,000 ppm

Turpentine

1,900 ppm

Xylene

10,000 ppm

*Reference NIOSH/OSHA Pocket Guide to Chemical Hazards DHEW (NIOSH) Publication No. 78-210

 

APPENDIX B. (Repealed.)

Amendments and deletions to VOSH standards for the construction industry to become effective January 1, 1988 and to coincide with the start-up date of the Virginia Confined Space Standard.

Safety Training and Education, 1926.21

1926.21(b)(6)(i)

Deleted

1926.21(b)(6)(ii)

Deleted

General Requirement for Storage, 1926.250

1926.250(b)(2)

Amended to apply this chapter to work on stored materials in silos, hoppers, tanks and similar storage areas

Gas Welding And Cutting, 1926.350

1926.350(b)(4)

Deleted

Fire Prevention, 1926.352

1926.352(g)

Deleted

Ventilation and Protection in Welding, Cutting, and Heating, 1926.353

1926.353(b)

Amended to apply this chapter to welding, cutting and heating in confined spaces

1926.353(b)(1)

Deleted

1926.353(b)(2)

Deleted

1926.353(c)

Amended to apply this chapter to welding, cutting, or heating of metals of toxic significance in confined spaces

1926.353(c)(1)

Deleted

1926.353(c)(1)(i)

Deleted

1926.353(c)(1)(ii)

Deleted

1926.353(c)(1)(iii)

Deleted

1926.353(c)(1)(iv)

Deleted

1926.353(c)(2)

Deleted

1926.353(c)(2)(i)

Deleted

1926.353(c)(2)(ii)

Deleted

1926.353(c)(2)(iii)

Deleted

1926.353(c)(2)(iv)

Deleted

Specific Excavation Requirements, 1926.651

1926.651(v)

Amended to apply this chapter to work in confined space excavations

Underground Lines, 1926.956

1926.956(a)(3)

Amended to apply this chapter to work in a manhole or unvented vault

1926.956(a)(3)(i)

Deleted

1926.956(a)(3)(ii)

Deleted

1926.956(a)(3)(iii)

Deleted

1926.956(b)(1)

Deleted

1926.956(b)(2)

Deleted

1926.956(b)(3)

Deleted

 

CHAPTER 150
UNDERGROUND CONSTRUCTION, CONSTRUCTION INDUSTRY

16VAC25-150-10. Underground construction; in general (29 CFR 1926.800). (Repealed.)

Note: The following standard is unique for the enforcement of occupational safety and health within the Commonwealth of Virginia under the jurisdiction of the VOSH Program. The existing federal OSHA standard does not apply; it does not carry the force of law and is not printed in this volume.

(a) Scope and application.

(1) This chapter applies to the construction of underground tunnels, shafts, chambers, and passageways. This chapter also applies to cut-and-cover excavations which are both physically connected to ongoing underground construction operations within the scope of this chapter, and covered in such a manner as to create conditions characteristic of underground construction. Except as otherwise provided, requirements of the Virginia Confined Space Standard for the Construction Industry, 16VAC25-140-10 et seq., that are more stringent than corresponding requirements in this chapter shall apply to underground construction areas which, while covered by this chapter, also meet the definition of "confined space" in 16VAC25-140-10.

(2) This chapter does not apply to the following:

(i) Excavation and trenching operations covered by Subpart P (16VAC25-175-1926.650 et seq.), such as foundation operations for above-ground structures that are not physically connected to underground construction operations, and surface excavation; nor

(ii) Underground electrical transmission and distribution lines, as addressed in Subpart V (16VAC25-175-1926.950 et seq.).

(b) Access and egress.

(1) The employer shall provide and maintain safe means of access and egress to all work stations.

(2) The employer shall provide access and egress in such a manner that employees are protected from being struck by excavators, haulage machines, trains and other mobile equipment.

(3) The employer shall control access to all openings to prevent unauthorized entry underground. Unused chutes, manways, or other openings shall be tightly covered, bulkheaded, or fenced off, and shall be posted with warning signs indicating "Keep Out" or similar language. Completed or unused sections of the underground facility shall be barricaded.

(c) Check-in/check-out. The employer shall maintain a check-in/check-out procedure that will ensure that above-ground personnel can determine an accurate count of the number of persons underground in the event of an emergency. However, this procedure is not required when the construction of underground facilities designed for human occupancy has been sufficiently completed so that the permanent environmental controls are effective, and when the remaining construction activity will not cause any environmental hazard or structural failure within the facilities.

(d) Safety instruction. All employees shall be instructed in the recognition and avoidance of hazards associated with underground construction activities including, where appropriate, the following subjects:

(1) Air monitoring;

(2) Ventilation;

(3) Illumination;

(4) Communications;

(5) Flood control;

(6) Mechanical equipment;

(7) Personal protective equipment;

(8) Explosives;

(9) Fire prevention and protection; and

(10) Emergency procedures, including evacuation plans and check-in/check-out systems.

(e) Notification.

(1) Oncoming shifts shall be informed of any hazardous occurrences or conditions that have affected or might affect employee safety, including liberation of gas, equipment failures, earth or rock slides, cave-ins, floodings, fires or explosions.

(2) The employer shall establish and maintain direct communications for coordination of activities with other employers whose operations at the jobsite affect or may affect the safety of employees underground.

(f) Communications.

(1) When natural unassisted voice communication is ineffective, a power-assisted means of voice communication shall be used to provide communication between the work face, the bottom of the shaft, and the surface.

(2) Two effective means of communication, at least one of which shall be voice communication, shall be provided in all shafts which are being developed or used either for personnel access or for hoisting. Additional requirements for hoist operator communication are contained in paragraph (t)(3)(xiv) of this chapter.

(3) Powered communication systems shall operate on an independent power supply, and shall be installed so that the use of or disruption of any one phone or signal location will not disrupt the operation of the system from any other location.

(4) Communication systems shall be tested upon initial entry of each shift to the underground, and as often as necessary at later times, to ensure that they are in working order.

(5) Any employee working alone underground in a hazardous location, who is both out of the range of natural unassisted voice communication and not under observation by other persons, shall be provided with an effective means of obtaining assistance in an emergency.

(g) Emergency provisions.

(1) Hoisting capability. When a shaft is used as a means of egress, the employer shall make advance arrangements for power-assisted hoisting capability to be readily available in an emergency, unless the regular hoisting means can continue to function in the event of an electrical power failure at the jobsite. Such hoisting means shall be designed so that the load hoist drum is powered in both directions of rotation and so that the brake is automatically applied upon power release or failure.

(2) Self-rescuers. The employer shall provide self-rescuers having current approval from the National Institute for Occupational Safety and Health and the Mine Safety and Health Administration to be immediately available to all employees at work stations in underground areas where employees might be trapped by smoke or gas. The selection, issuance, use, and care of respirators shall be in accordance with paragraphs (b) and (c) of 16VAC25-175-1926.103 (Subpart E).

(3) Designated person. At least one designated person shall be on duty above ground whenever any employee is working underground. This designated person shall be responsible for securing immediate aid and keeping an accurate count of employees underground in case of emergency. The designated person must not be so busy with other responsibilities that the counting function is encumbered.

(4) Emergency lighting. Each employee underground shall have an acceptable portable hand lamp or cap lamp in his or her work area for emergency use, unless natural light or an emergency lighting system provides adequate illumination for escape.

(5) Rescue teams.

(i) On jobsites where 25 or more employees work underground at one time, the employer shall provide (or make arrangements in advance with locally available rescue services to provide) at least two 5-person rescue teams, one on the jobsite or within one-half hour travel time from the entry point, and the other within 2 hours travel time.

(ii) On jobsites where less than 25 employees work underground at one time, the employer shall provide (or make arrangements in advance with locally available rescue services to provide) at least one 5-person rescue team to be either on the jobsite or within one-half hour travel time from the entry point.

(iii) Rescue team members shall be qualified in rescue procedures, the use and limitations of breathing apparatus, and the use of fire fighting equipment. Qualifications shall be reviewed not less than annually.

(iv) On jobsites where flammable or noxious gases are encountered or anticipated in hazardous quantities, rescue team members shall practice donning and using self-contained breathing apparatus monthly.

(v) The employer shall ensure that rescue teams are familiar with conditions at the jobsite.

(h) Hazardous classifications.

(1) Potentially gassy operations. Underground construction operations shall be classified as potentially gassy if either:

(i) Air monitoring discloses 10% or more of the lower explosive limit for methane or other flammable gases measured at 12 inches (304.8 mm) ±0.25 inch (6.35 mm) from the roof, face, floor or walls in any underground work area for more than a 24-hour period; or

(ii) The history of the geographical area or geological formation indicates that 10% or more of the lower explosive limit for methane or other flammable gases is likely to be encountered in such underground operations.

(2) Gassy operations. Underground construction operations shall be classified as gassy if:

(i) Air monitoring discloses 10% or more of the lower explosive limit for methane or other flammable gases measured at 12 inches (304.8 mm) ±0.25 inch (6.35 mm) from the roof, face, floor or walls in any underground work area for three consecutive days; or

(ii) There has been an ignition of methane or of other flammable gases emanating from the strata that indicates the presence of such gases; or

(iii) The underground construction operation is both connected to an underground work area which is currently classified as gassy and is also subject to a continuous course of air containing the flammable gas concentration.

(3) Declassification to potentially gassy operations. Underground construction gassy operations may be declassified to Potentially Gassy when air monitoring results remain under 10% of the lower explosive limit for methane or other flammable gases for three consecutive days.

(i) Gassy operations-additional requirements.

(1) Only acceptable equipment, maintained in suitable condition, shall be used in gassy operations.

(2) Mobile diesel-powered equipment used in gassy operations shall be either approved in accordance with the requirements of 30 CFR Part 36 (formerly Schedule 31) by MSHA, or shall be demonstrated by the employer to be fully equivalent to such MSHA-approved equipment, and shall be operated in accordance with that part.

(3) Each entrance to a gassy operation shall be prominently posted with signs notifying all entrants of the gassy classification.

(4) Smoking shall be prohibited in all gassy operations and the employer shall be responsible for collecting all personal sources of ignition, such as matches and lighters, from all persons entering a gassy operation.

(5) A fire watch as described in 16VAC25-175-1926.352(e) shall be maintained when hot work is performed.

(6) Once an operation has met the criteria in paragraph (h)(2) warranting classification as gassy, all operations in the affected area, except the following, shall be discontinued until the operation either is in compliance with all of the gassy operation requirements or has been declassified in accordance with paragraph (h)(3) of this section:

(i) Operations related to the control of the gas concentration;

(ii) Installation of new equipment, or conversion of existing equipment, to comply with this paragraph (i); and

(iii) Installation of above ground controls for reversing the air flow.

(j) Air quality and monitoring.

(1) General. Air quality limits and control requirements for construction are found in 16VAC25-175-1926.55, except as modified by this chapter.

(i) (a) The employer shall assign a competent person who shall perform all air monitoring required by this chapter.

(b) Where this paragraph requires monitoring of airborne contaminants "as often as necessary," the competent person shall make a reasonable determination as to which substances to monitor and how frequently to monitor, considering at least the following factors:

(1) Location of jobsite: Proximity to fuel tanks, sewers, gas lines, old landfills, coal deposits, and swamps;

(2) Geology: Geological studies of the jobsite, particularly involving the soil type and its permeability;

(3) History: Presence of air contaminants in nearby jobsites, changes in levels of substances monitored on the prior shift; and

(4) Work practices and jobsite conditions: The use of diesel engines, use of explosives, use of fuel gas, volume and flow of ventilation, visible atmospheric conditions, decompression of the atmosphere, welding, cutting and hot work, and employees physical reactions to working underground.

(ii) (a) The atmosphere in all underground work areas shall be tested as often as necessary to assure that the atmosphere as normal atmospheric pressure contains at least 19.5% oxygen and no more than 23% oxygen.

(b) Tests for oxygen content shall be made before tests for air contaminants.

(iii) (a) The atmosphere in all underground work areas shall be tested quantitatively for carbon monoxide, nitrogen dioxide, hydrogen sulfide, and other toxic gases, dusts, vapors, mists, and fumes as often as necessary to ensure that the permissible exposure limits prescribed in 16VAC25-175-1926.55 are not exceeded.

(b) The atmosphere in all underground work areas shall be tested quantitatively for methane and other flammable gases as often as necessary to determine:

(1) Whether action is to be taken under paragraphs (j)(1)(vii), (viii), and (ix), of this chapter; and

(2) Whether an operation is to be classified potentially gassy or gassy under paragraph (h) of this chapter.

(c) If diesel-engine or gasoline-engine driven ventilating fans or compressors are used, an initial test shall be made of the inlet air of the fan or compressor, with the engines operating, to ensure that the air supply is not contaminated by engine exhaust.

(d) Testing shall be performed as often as necessary to ensure that the ventilation requirements of paragraph (k) of this chapter are met.

(iv) When rapid excavation machines are used, a continuous flammable gas monitor shall be operated at the face with the sensor(s) placed as high and close to the front of the machine's cutter head as practicable.

(v) (a) Whenever air monitoring indicates the presence of 5 ppm or more of hydrogen sulfide, a test shall be conducted in the affected underground work area(s), at least at the beginning and midpoint of each shift, until the concentration of hydrogen sulfide has been less than 5 ppm for 3 consecutive days.

(b) Whenever hydrogen sulfide is detected in an amount exceeding 10 ppm, a continuous sampling and indicating hydrogen sulfide monitor shall be used to monitor the affected work area.

(c) Employees shall be informed when a concentration of 10 ppm hydrogen sulfide is exceeded.

(d) The continuous sampling and indicating hydrogen sulfide monitor shall be designed, installed, and maintained to provide a visual and aural alarm when the hydrogen sulfide concentration reaches 20 ppm to signal that additional measure, such as respirator use, increased ventilation, or evacuation, might be necessary to maintain hydrogen sulfide exposure below the permissible exposure limit.

(vi) When the competent person determines, on the basis of air monitoring results or other information, that air contaminants may be present in sufficient quantity to be dangerous to life, the employer shall:

(a) Prominently post a notice at all entrances to the underground jobsite to inform all entrants of the hazardous condition; and

(b) Ensure that the necessary precautions are taken.

(vii) Whenever 5.0% or more of the lower explosive limit for methane or other flammable gases is detected in any underground work area(s) or in the air return, steps shall be taken to increase ventilation air volume or otherwise control the gas concentration, unless the employer is operating in accordance with the potentially gassy or gassy operation requirements. Such additional ventilation controls may be discontinued when gas concentrations are reduced below 5.0% of the lower explosive limit, but shall be reinstituted whenever the 5.0% level is exceeded.

(viii) Whenever 10% or more of the lower explosive limit for methane or other flammable gases is detected in the vicinity of welding, cutting, or other hot work, such work shall be suspended until the concentration of such flammable gas is reduced to less than 10% of the lower explosive limit.

(ix) Whenever 20% or more of the lower explosive limit for methane or other flammable gases is detected in any underground work area(s) or in the air return:

(a) All employees, except those necessary to eliminate the hazard, shall be immediately withdrawn to a safe location above ground; and

(b) Electrical power, except for acceptable pumping and ventilation equipment, shall be cut off to the area endangered by the flammable gas until the concentration of such gas is reduced to less than 20% of the lower explosive limit.

(2) Additional monitoring for potentially gassy and gassy operations. Operations which met the criteria for potentially gassy and gassy operations set forth in paragraph (h) of this section shall be subject to the additional monitoring requirements of this paragraph.

(i) A test for oxygen content shall be conducted in the affected underground work areas and work areas immediately adjacent to such areas at least at the beginning and midpoint of each shift.

(ii) When using rapid excavation machines, continuous automatic flammable gas monitoring equipment shall be used to monitor the air at the heading, on the rib, and in the return air duct. The continuous monitor shall signal the heading, and shut down electric power in the affected underground work area, except for acceptable pumping and ventilation equipment, when 20% or more of the lower explosive limit for methane or other flammable gases is encountered.

(iii) A manual flammable gas monitor shall be used as needed, but at least at the beginning and midpoint of each shift, to ensure that the limits prescribed in paragraphs (h) and (j) are not exceeded. In addition, a manual electrical shut down control shall be provided near the heading.

(iv) Local gas tests shall be made prior to and continuously during any welding, cutting, or other hot work.

(v) In underground operations driven by drill-and-blast methods, the air in the affected area shall be tested for flammable gas prior to reentry after blasting, and continuously when employees are working underground.

(3) Record keeping. A record of all air quality tests shall be maintained above ground at the worksite and be made available to the Commissioner of the Department of Labor and Industry upon request. The record shall include the location, date, time, substance and amount monitored. Records of exposures to toxic substances shall be retained in accordance with 16VAC25-80-10 et seq. All other air quality test records shall be retained until completion of the project.

(k) Ventilation.

(1) (i) Fresh air shall be supplied to all underground work areas in sufficient quantities to prevent dangerous or harmful accumulation of dusts, fumes, mists, vapors or gases.

(ii) Mechanical ventilation shall be provided in all underground work areas except when the employer can demonstrate that natural ventilation provides the necessary air quality through sufficient air volume and air flow.

(2) A minimum of 200 cubic feet (5.7 m³) or fresh air per minute shall be supplied for each employee underground.

(3) The linear velocity of air flow in the tunnel bore, in shafts, and in all other underground work areas shall be at least 30 feet (9.15 m) per minute where blasting or rock drilling is conducted, or where other conditions likely to produce dust, fumes, mists, vapors, or gases in harmful or explosive quantities are present.

(4) The direction of mechanical air flow shall be reversible.

(5) Following blasting, ventilation systems shall exhaust smoke and fumes to the outside atmosphere before work is resumed in affected areas.

(6) Ventilation doors shall be designed and installed so that they remain closed when in use, regardless of the direction of the air flow.

(7) When ventilation has been reduced to the extent that hazardous levels of methane or flammable gas may have accumulated, a competent person shall test all affected areas after ventilation has been restored and shall determine whether the atmosphere is within flammable limits before any power, other than for acceptable equipment, is restored or work is resumed.

(8) Whenever the ventilation system has been shut down with all employees out of the underground area, only competent persons authorized to test for air contaminants shall be allowed underground until the ventilation has been restored and all affected areas have been tested for air contaminants and declared safe.

(9) When drilling rock or concrete, appropriate dust control measures shall be taken to maintain dust levels within limits set in 16VAC25-175-1926.55. Such measures may include, but are not limited to, wet drilling, the use of vacuum collectors, and water mix spray systems.

(10) (i) Internal combustion engines, except diesel-powered engines on mobile equipment, are prohibited underground.

(ii) Mobile diesel-powered equipment used underground in atmospheres other than gassy operations shall be either approved by MSHA in accordance with the provisions of 30 CFR Part 32 (formerly Schedule 24), or shall be demonstrated by the employer to be fully equivalent to such MSHA-approved equipment, and shall be operated in accordance with that Part. (Each brake horsepower of a diesel engine requires at least 100 cubic feet (28.32 m³) of air per minute for suitable operation in addition to the air requirements for personnel. Some engines may require a greater amount of air to ensure that the allowable levels of carbon monoxide, nitric oxide, and nitrogen dioxide are not exceeded.)

(11) Potentially gassy or gassy operations shall have ventilation systems installed which shall:

(i) Be constructed of fire-resistant materials; and

(ii) Have acceptable electrical systems, including fan motors.

(12) Gassy operations shall be provided with controls located above ground for reversing the air flow of ventilation systems.

(13) In potentially gassy or gassy operations, wherever mine-type ventilation systems using an offset main fan installed on the surface are used, they shall be equipped with explosion-doors or a weak-wall having an area at least equivalent to the cross-sectional area of the airway.

(l) Illumination.

(1) Illumination requirements applicable to underground construction operations are found in Table D-3 of 16VAC25-175-1926.56.

(2) Only acceptable portable lighting equipment shall be used within 50 feet (15.24 m) of any underground heading during explosives handling.

(m) Fire prevention and control. Fire prevention and protection requirements applicable to underground construction operations are found in Subpart F of this part (16VAC25-175-1926.150 et seq.), except as modified by the following additional standards.

(1) Open flames and fires are prohibited in all underground construction operations except as permitted for welding, cutting and other hot work operations in paragraph (n) of this chapter.

(2) (i) Smoking may be allowed only in areas free of fire and explosion hazards.

(ii) Readily visible signs prohibiting smoking and open flames shall be posted in areas having fire or explosion hazards.

(3) The employer may store underground no more than a 24-hour supply of diesel fuel for the underground equipment used at the worksite.

(4) The piping of diesel fuel from the surface to an underground location is permitted only if:

(i) Diesel fuel is contained at the surface in a tank whose maximum capacity is no more than the amount of fuel required to supply for a 24-hour period the equipment serviced by the underground fueling station; and

(ii) The surface tank is connected to the underground fueling station by an acceptable pipe or hose system that is controlled at the surface by a valve, and at the shaft bottom by a hose nozzle; and

(iii) The pipe is empty at all times except when transferring diesel fuel from the surface tank to a piece of equipment in use underground; and

(iv) Hoisting operations in the shaft are suspended during refueling operations if the supply piping in the shaft is not protected from damage.

(5) (i) Gasoline shall not be carried, stored, or used underground.

(ii) Acetylene, liquefied petroleum gas, and Methylacetylene Propadiene Stabilized gas may be used underground only for welding, cutting and other hot work, and only in accordance with Subpart J of this part (16VAC25-175-1926.350 et seq.), and paragraphs (j), (k), (m), and (n) of this chapter.

(6) Oil, grease, and diesel fuel stored underground shall be kept in tightly sealed containers in fire-resistant areas at least 300 feet (91.44 m) from underground explosive magazines, and at least 100 feet (30.48 m) from shaft stations and steeply inclined passageways. Storage areas shall be positioned or diked so that the contents of ruptured or overturned containers will not flow from the storage area.

(7) Flammable or combustible materials shall not be stored above ground within 100 feet (30.48 m) of any access opening to any underground operation. Where this is not feasible because of space limitations at the jobsite, such materials may be located within the 100-foot limit, provided that:

(i) They are located as far as practicable from the opening; and

(ii) Either a fire-resistant barrier of not less than one-hour rating is placed between the stored material and the opening, or additional precautions are taken which will protect the materials from ignition sources.

(8) Fire-resistant hydraulic fluids shall be used in hydraulically-actuated underground machinery and equipment unless such equipment is protected by a fire suppression system or by multi-purpose fire extinguisher(s) rated at of sufficient capacity for the type and size of hydraulic equipment involved, but rated at least 4A:40B:C.

(9) (i) Electrical installations in underground areas where oil, grease, or diesel fuel are stored shall be used only for lighting fixtures.

(ii) Lighting fixtures in storage areas, or within 25 feet (7.62 m) of underground areas where oil, grease, or diesel fuel are stored, shall be approved for Class I, Division 2 locations, in accordance with Subpart K of this part (16VAC25-175-1926.400 et seq.).

(10) Leaks and spills of flammable or combustible fluids shall be cleaned up immediately.

(11) A fire extinguisher of at least 4A:40B:C rating or other equivalent extinguishing means shall be provided at the head pulley and at the tail pulley of underground belt conveyors.

(12) Any structure located underground or within 100 feet (30.48 m) of an opening to the underground shall be constructed of material having a fire-resistance rating of at least one hour.

(n) Welding, cutting, and other hot work. In addition to the requirements of Subpart J of this part (16VAC25-175-1926.350 et seq.), the following requirements shall apply to underground welding, cutting, and other hot work.

(1) No more than the amount of fuel gas and oxygen cylinders necessary to perform welding, cutting, or other hot work during the next 24-hour period shall be permitted underground.

(2) Noncombustible barriers shall be installed below welding, cutting, or other hot work being done in or over a shaft or raise.

(o) Ground support.

(1) Portal areas. Portal openings and access areas shall be guarded by shoring, fencing, head walls, shotcreting or other equivalent protection to ensure safe access of employees and equipment. Adjacent areas shall be scaled or otherwise secured to prevent loose soil, rock, or fractured materials from endangering the portal and access area.

(2) Subsidence areas. The employer shall ensure ground stability in hazardous subsidence areas by shoring, by filling in, or by erecting barricades and posting warning signs to prevent entry.

(3) Underground areas.

(i) (a) A competent person shall inspect the roof, face, and walls of the work area at the start of each shift and as often as necessary to determine ground stability.

(b) Competent persons conducting such inspections shall be protected from loose ground by location, ground support or equivalent means.

(ii) Ground conditions along haulageways and travelways shall be inspected as frequently as necessary to ensure safe passage.

(iii) Loose ground that might be hazardous to employees shall be taken down, scaled or supported.

(iv) (a) Torque wrenches shall be used wherever bolts that depend on torsionally applied force are used for ground support.

(b) A competent person shall determine whether rock bolts meet the necessary torque, and shall determine the testing frequency in light of the bolt system, ground conditions and the distance from vibration sources.

(v) Suitable protection shall be provided for employees exposed to the hazard of loose ground while installing ground support systems.

(vi) Support sets shall be installed so that the bottoms have sufficient anchorage to prevent ground pressures from dislodging the support base of the sets. Lateral bracing (collar bracing, tie rods, or spreaders) shall be provided between immediately adjacent sets to ensure added stability.

(vii) Damaged or dislodged ground supports that create a hazardous condition shall be promptly repaired or replaced. When replacing supports, the new supports shall be installed before the damaged supports are removed.

(viii) A shield or other type of support shall be used to maintain a safe travelway for employees working in dead-end areas ahead of any support replacement operation.

(4) Shafts.

(i) Shafts and wells over 5 feet (1.53 m) in depth that employees must enter shall be supported by a steel casing, concrete pipe, timber, solid rock or other suitable material.

(ii) (a) The full depth of the shaft shall be supported by casing or bracing except where the shaft penetrates into solid rock having characteristics that will not change as a result of exposure. Where the shaft passes through earth into solid rock, or through solid rock into earth, and where there is potential for shear, the casing or bracing shall extend at least 5 feet (1.53 m) into the solid rock. When the shaft terminates in solid rock, the casing or bracing shall extend to the end of the shaft or 5 feet (1.53 m) into the solid rock, whichever is less.

(b) The casing or bracing shall extend 42 inches (1.07 m) plus or minus 3 inches (8 cm) above ground level, except that the minimum casing height may be reduced to 12 inches (0.3 m), provided that a standard railing is installed; that the ground adjacent to the top of the shaft is sloped away from the shaft collar to prevent entry of liquids; and that effective barriers are used to prevent mobile equipment operating near the shaft from jumping over the 12 inch (0.3 m) barrier.

(iii) After blasting operations in shafts, a competent person shall determine if the walls, ladders, timbers, blocking, or wedges have loosened. If so, necessary repairs shall be made before employees other than those assigned to make the repairs are allowed in or below the affected areas.

(p) Blasting. This paragraph applies in addition to the requirements for blasting and explosives operations, including handling of misfires, which are found in Subpart U of this part (16VAC25-175-1926.900 et seq.).

(1) Blasting wires shall be kept clear of electrical lines, pipes, rails, and other conductive material, excluding earth, to prevent explosives initiation or employee exposure to electric current.

(2) Following blasting, an employee shall not enter a work area until the air quality meets the requirements of paragraph (j) of this chapter.

(q) Drilling.

(1) A competent person shall inspect all drilling and associated equipment prior to each use. Equipment defects affecting safety shall be corrected before the equipment is used.

(2) The drilling area shall be inspected for hazards before the drilling operation is started.

(3) Employees shall not be allowed on a drill mast while the drill bit is in operation or the drill machine is being moved.

(4) When a drill machine is being moved from one drilling area to another, drill steel, tools, and other equipment shall be secured and the mast shall be placed in a safe position.

(5) Receptacles or racks shall be provided for storing drill steel located on jumbos.

(6) Employees working below jumbo decks shall be warned whenever drilling is about to begin.

(7) Drills on columns shall be anchored firmly before starting drilling, and shall be retightened as necessary thereafter.

(8) (i) The employer shall provide mechanical means on the top deck of a jumbo for lifting unwieldy or heavy material.

(ii) When jumbo decks are over 10 feet (3.05 m) in height, the employer shall install stairs wide enough for two persons.

(iii) Jumbo decks more than 10 feet (3.05 m) in height shall be equipped with guardrails on all open sides, excluding access openings of platforms, unless an adjacent surface provides equivalent fall protection.

(iv) (a) Only employees assisting the operator shall be allowed to ride on jumbos, unless the jumbo meets the requirements of paragraph (r)(6)(ii) of this chapter.

(b) Jumbos shall be chocked to prevent movement while employees are working on them.

(v) (a) Walking and working surfaces of jumbos shall be maintained to prevent the hazards of slipping, tripping and falling.

(b) Jumbo decks and stair treads shall be designed to be slip-resistant and secured to prevent accidental displacement.

(9) Scaling bars shall be available at scaling operations and shall be maintained in good condition at all times. Blunted or severely worn bars shall not be used.

(10) (i) Blasting holes shall not be drilled through blasted rock (muck) or water.

(ii) Employees in a shaft shall be protected either by location or by suitable barrier(s) if powered mechanical loading equipment is used to remove muck containing unfired explosives.

(11) A caution sign reading "Buried Line," or similar wording shall be posted where air lines are buried or otherwise hidden by water or debris.

(r) Haulage

(1) (i) A competent person shall inspect haulage equipment before each shift.

(ii) Equipment defects affecting safety and health shall be corrected before the equipment is used.

(2) Powered mobile haulage equipment shall have suitable means of stopping.

(3) (i) Power mobile haulage equipment, including trains, shall have audible warning devices to warn employees to stay clear. The operator shall sound the warning device before moving the equipment and whenever necessary during travel.

(ii) The operator shall assure that lights which are visible to employees at both ends of any mobile equipment, including a train, are turned on whenever the equipment is operating.

(4) In those cabs where glazing is used, the glass shall be safety glass, or its equivalent, and shall be maintained and cleaned so that vision is not obstructed.

(5) Anti-roll back devices or brakes shall be installed on inclined conveyor drive units to prevent conveyors from inadvertently running in reverse.

(6) (i) (a) Employees shall not be permitted to ride a power-driven chain, belt, or bucket conveyor unless the conveyor is specifically designed for the transportation of persons.

(b) Endless belt-type manlifts are prohibited in underground construction.

(c) General requirements also applicable to underground construction for use of conveyors in construction are found in 16VAC25-175-1926.555.

(ii) No employee shall ride haulage equipment unless it is equipped with seating for each passenger and protects passengers from being struck, crushed, or caught between other equipment or surfaces. Members of train crews may ride on a locomotive if it is equipped with handholds and nonslip steps or footboards. Requirements applicable to Underground Construction for motor vehicle transportation of employees are found in 16VAC25-175-1926.601.

(7) Powered mobile haulage equipment, including trains, shall not be left unattended unless the master switch or motor is turned off; operating controls are in neutral or park position; and the brakes are set, or equivalent precautions are taken to prevent rolling.

(8) Whenever rails serve as a return for a trolley circuit, both rails shall be bonded at every joint and crossbonded every 200 feet (60.96 m).

(9) When dumping cars by hand, the car dumps shall have tiedown chains, bumper blocks, or other locking or holding devices to prevent the cars from overturning.

(10) Rocker-bottom or bottom-dump cars shall be equipped with positive locking devices to prevent unintended dumping.

(11) Equipment to be hauled shall be loaded and secured to prevent sliding or dislodgement.

(12) (i) Mobile equipment, including rail-mounted equipment, shall be stopped for manual connecting or service work.

(ii) Employees shall not reach between moving cars during coupling operations.

(iii) Couplings shall not be aligned, shifted or cleaned on moving cars or locomotives.

(13) (i) Safety chains or other connections shall be used in addition to couplers to connect man cars or powder cars whenever the locomotive is uphill of the cars.

(ii) When the grade exceeds one percent and there is a potential for runaway cars, safety chains or other connections shall be used in addition to couplers to connect haulage cars or, as an alternative, the locomotive must be downhill of the train.

(iii) Such safety chains or other connections shall be capable of maintaining connection between cars in the event of either coupler disconnect, failure or breakage.

(14) Parked rail equipment shall be chocked, blocked, or have brakes set to prevent inadvertent movement.

(15) Berms, bumper blocks, safety hooks, or equivalent means shall be provided to prevent overtravel and overturning of haulage equipment at dumping locations.

(16) Bumper blocks or equivalent stopping devices shall be provided at all track dead ends.

(17) (i) Only small hand tools, lunch pails or similar small items may be transported with employees in mancars, or on top of a locomotive.

(ii) When small hand tools or other small items are carried on top of a locomotive, the top shall be designed or modified to retain them while traveling.

(18) (i) Where switching facilities are available, occupied personnel-cars shall be pulled, not pushed. If personnel-cars must be pushed and visibility of the track ahead is hampered, then a qualified person shall be stationed in the lead car to give signals to the locomotive operator.

(ii) Crew trips shall consist of personnel-loads only.

(s) Electrical safety. This paragraph applies in addition to the general requirements for electrical safety which are found in Subpart K of this part (16VAC25-175-1926.400 et seq.).

(1) Electric power lines shall be insulated or located away from water lines, telephone lines, air lines, or other conductive materials so that a damaged circuit will not energize the other systems.

(2) Lighting circuits shall be located so that movement of personnel or equipment will not damage the circuits or disrupt service.

(3) Oil-filled transformers shall not be used underground unless they are located in a fire-resistant enclosure suitably vented to the outside and surrounded by a dike to retain the contents of the transformers in the event of rupture.

(t) Hoisting unique to underground construction. Except as modified by this paragraph (t), employers must comply with the requirements of Subpart CC of 29 CFR 1926, except that the limitation in 16VAC25-175-1926.1431(a) does not apply to the routine access of employees to an underground worksite via a shaft; ensure that material hoists comply with 16VAC25-175-1926.552(a) and (b); and ensure that personnel hoists comply with the personnel-hoists requirements of 16VAC25-175-1926.552(a) and (c) and the elevator requirements of 16VAC25-175-1926.552(a) and (d).

(1) General requirements for cranes and hoists.

(i) Materials, tools, and supplies being raised or lowered, whether within a cage or otherwise, shall be secured or stacked in a manner to prevent the load from shifting, snagging, or falling into the shaft.

(ii) A warning light suitably located to warn employees at the shaft bottom and subsurface shaft entrances shall flash whenever a load is above the shaft bottom or subsurface entrances, or the load is being moved in the shaft. This paragraph does not apply to fully enclosed hoistways.

(iii) Whenever a hoistway is not fully enclosed and employees are at the shaft bottom, conveyances or equipment shall be stopped at least 15 feet (4.57 m) above the bottom of the shaft and held there until the signalman at the bottom of the shaft directs the operator to continue lowering the load, except that the load may be lowered without stopping if the load or conveyance is within full view of a bottom signalman who is in constant voice communication with the operator.

(iv) (A) Before maintenance, repairs, or other work is commenced in the shaft served by a cage, skip, or bucket, the operator and other employees in the area shall be informed and given suitable instructions.

(B) A sign warning that work is being done in the shaft shall be installed at the shaft collar, at the operator's station, and at each underground landing.

(v) Any connection between the hoisting rope and the cage or skip shall be compatible with the type of wire rope used for hoisting.

(vi) Spin-type connections, where used, shall be maintained in a clean condition and protected from foreign matter that could affect their operation.

(vii) Cage, skip, and load connections to the hoist rope shall be made so that the force of the hoist pull, vibration, misalignment, release of lift force, or impact will not disengage the connection. Moused or latched openthroat hooks do not meet this requirement.

(viii) When using wire rope wedge sockets, means shall be provided to prevent wedge escapement and to ensure that the wedge is properly seated.

(2) Additional requirements for cranes. Cranes shall be equipped with a limit switch to prevent overtravel at the boom tip. Limit switches are to be used only to limit travel of loads when operational controls malfunction and shall not be used as a substitute for other operational controls.

(3) Additional requirements for hoists.

(i) Hoists shall be designed so that the load hoist drum is powered in both directions of rotation and so that brakes are automatically applied upon power release or failure.

(ii) Control levers shall be of the "deadman type," which return automatically to their center (neutral) position upon release.

(iii) When a hoist is used for both personnel hoisting and material hoisting, load and speed ratings for personnel and for materials shall be assigned to the equipment.

(iv) Material hoisting may be performed at speeds higher than the rated speed for personnel hoisting if the hoist and components have been designed for such higher speeds and if shaft conditions permit.

(v) Employees shall not ride on top of any cage, skip, or bucket except when necessary to perform inspection or maintenance of the hoisting system, in which case they shall be protected by a body belt/harness system to prevent falling.

(vi) Personnel and materials (other than small tools and supplies secured in a manner that will not create a hazard to employees) shall not be hoisted together in the same conveyance. However, if the operator is protected from the shifting of materials, then the operator may ride with materials in cages or skips which are designed to be controlled by an operator within the cage or skip.

(vii) Line speed shall not exceed the design limitations of the systems.

(viii) Hoists shall be equipped with landing level indicators at the operator's station. Marking the hoist rope does not satisfy this requirement.

(ix) Whenever glazing is used in the hoist house, it shall be safety glass, or its equivalent, and be free of distortions and obstructions.

(x) A fire extinguisher that is rated at least 2A:10B:C (multi-purpose, dry chemical) shall be mounted in each hoist house.

(xi) Hoist controls shall be arranged so that the operator can perform all operating cycle functions and reach the emergency power cutoff without having to reach beyond the operator's normal operating position.

(xii) Hoists shall be equipped with limit switches to prevent overtravel at the top and bottom of the hoistway.

(xiii) Limit switches are to be used only to limit travel of loads when operational controls malfunction and shall not be used as a substitute for other operational controls.

(xiv) Hoist operators shall be provided with a closed-circuit voice communication system to each landing station, with speaker microphones so located that the operator can communicate with individual landing stations during hoist use.

(xv) When sinking shafts 75 feet (22.86 m) or less in depth, cages, skips, and buckets that may swing, bump, or snag against shaft sides or other structural protrusions shall be guided by fenders, rails or ropes, or a combination of those means.

(xvi) When sinking shafts more than 75 feet (22.86 m) in depth, all cages, skips, and buckets shall be rope or rail guided to within a rail length from the sinking operation.

(xvii) Cages, skips, and buckets in all completed shafts, or in all shafts being used as completed shafts, shall be rope or rail-guided for the full length of their travel.

(xviii) Wire rope used in load lines of material hoists shall be capable of supporting, without failure, at least five times the maximum intended load or the factor recommended by the rope manufacturer, whichever is greater. Refer to 16VAC25-175-1926.552(c)(14)(iii) for design factors for wire rope used in personnel hoists. The design factor shall be calculated by dividing the breaking strength of wire rope, as reported in the manufacturer's rating tables, by the total static load, including the weight of the wire rope in the shaft when fully extended.

(xix) A competent person shall visually check all hoisting machinery, equipment, anchorages, and hoisting rope at the beginning of each shift and during hoist use, as necessary.

(xx) Each safety device shall be checked by a competent person at least weekly during hoist use to ensure suitable operation and safe condition.

(xxi) In order to ensure suitable operation and safe condition of all functions and safety devices, each hoist assembly shall be inspected and load-tested to 100% of its rated capacity: at the time of installation; after any repairs or alterations affecting its structural integrity; after the operation of any safety device; and annually when in use. The employer shall prepare a certification record which includes the date each inspection and load-test was performed; the signature of the person who performed the inspection and test; and a serial number or other identifier for the hoist that was inspected and tested. The most recent certification record shall be maintained on file until completion of the project.

(xxii) Before hoisting personnel or material, the operator shall perform a test run of any cage or skip whenever it has been out of service for one complete shift and whenever the assembly or components have been repaired or adjusted.

(xxiii) Unsafe conditions shall be corrected before using the equipment.

(4) Additional requirements for personnel hoists.

(i) Hoist drum systems shall be equipped with at least two means of stopping the load, each of which shall be capable of stopping and holding 150% of the hoist's rated line pull. A broken-rope safety, safety catch, or arrestment device is not a permissible means of stopping under this paragraph (t).

(ii) The operator shall remain within sight and sound of the signals at the operator's station.

(iii) All sides of personnel cages shall be enclosed by 1-2 inch (12.70 mm) wire mesh (not less than No. 14 gauge or equivalent) to a height of not less than 6 feet (1.83 m). However, when the cage or skip is being used as a work platform, its sides may be reduced in height to 42 inches (1.07 m) when the conveyance is not in motion.

(iv) All personnel cages shall be provided with a positive locking door that does not open outward.

(v) All personnel cages shall be provided with a protective canopy. The canopy shall be made of steel plate, at least 3/16-inch (4.763 mm) in thickness, or material of equivalent strength and impact resistance. The canopy shall be sloped to the outside and so designed that a section may be readily pushed upward to afford emergency egress. The canopy shall cover the top in such a manner as to protect those inside from objects falling in the shaft.

(vi) Personnel platforms operating on guide rails or guide ropes shall be equipped with broken-rope safety devices, safety catches, or arrestment devices that will stop and hold 150% of the weight of the personnel platform and its maximum rated load.

(vii) During sinking operations in shafts where guides and safeties are not yet used, the travel speed of the personnel platform shall not exceed 200 feet (60.96 m) per minute. Governor controls set for 200 feet (60.96 m) per minute shall be installed in the control system and shall be used during personnel hoisting.

(viii) The personnel platform may travel over the controlled length of the hoistway at rated speeds up to 600 feet (182.88 m) per minute during sinking operations in shafts where guides and safeties are used.

(ix) The personnel platform may travel at rated speeds greater than 600 feet (182.88 m) per minute in completed shafts.

(u) Definitions. "Accept" - Any device, equipment, or appliance that is either approved by MSHA and maintained in permissible condition, or is listed or labeled for the class and location under Subpart K of this part.

"Rapid excavation machine" - Tunnel boring machines, shields, roadheaders, or any other similar excavation machine.

(Information collection requirements contained in paragraphs (j)(1), (j)(2), and (j)(3) were approved by the Office of Management and Budget under control number 1218-0067)

CHAPTER 170
VIRGINIA EXCAVATION STANDARD, CONSTRUCTION INDUSTRY (29 CFR 1926.650 - 1926.652)

16VAC25-170-10. Scope, application, and definitions applicable to this subpart (29 CFR 1926.650). (Repealed.)

Note: The following standard is unique for the enforcement of occupational safety and health within the Commonwealth of Virginia under the jurisdiction of the VOSH Program. The existing federal OSHA standard does not apply; it does not carry the force of law and is not printed in this volume.

(a) Scope and application. This section applies to all open excavations made in the earth's surface. Excavations are defined to include trenches.

(b) Definitions applicable to this subpart.

"Accepted engineering practices" means those requirements which are compatible with standards of practice required by a registered professional engineer.

"Aluminum hydraulic shoring" means a pre-engineered shoring system comprised of aluminum hydraulic cylinders (crossbraces) used in conjunction with vertical rails (uprights) or horizontal rails (walers). Such system is designed, specifically to support the sidewalls of an excavation and prevent cave-ins.

"Bell-bottom pier hole" means a type of shaft or footing excavation, the bottom of which is made larger than the cross section above to form a belled shape.

"Benching (Benching system)" means a method of protecting employees from cave-ins by excavating the sides of an excavation to form one or a series of horizontal levels or steps, usually with vertical or near-vertical surfaces between levels.

"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 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.

"Competent person" means one 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.

"Cross braces" mean the horizontal members of a shoring system installed perpendicular to the sides of the excavation, the ends of which bear against either uprights or wales.

"Excavation" means any man-made cut, cavity, trench, or depression in an earth surface, formed by earth removal.

"Faces" or "sides" means the vertical or inclined earth surfaces formed as a result of excavation work.

"Failure" means the breakage, displacement, or permanent deformation of a structural member or connection so as to reduce its structural integrity and its supportive capabilities.

"Hazardous atmosphere" means an atmosphere which by reason of being explosive, flammable, poisonous, corrosive, oxidizing, irritating, oxygen deficient, toxic, or otherwise harmful, may cause death, illness, or injury.

"Kickout" means the accidental release or failure of a cross brace.

"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.

"Ramp" means an inclined walking or working surface that is used to gain access to one point from another, and is constructed from earth or from structural materials such as steel or wood.

"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 chapter when approving designs for "manufactured protective systems" or "tabulated data" to be used in interstate commerce.

"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.

"Shield (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 structures. 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 16VAC25-170-30 (c)(3) or (c)(4). Shields used in trenches are usually referred to as "trench boxes" or "trench shields."

"Shoring (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.

"Sides." See "Faces."

"Sloping (Sloping system)" means a method of protecting employees from cave-ins by excavating to form sides of an excavation that are inclined away from the excavation so as to prevent cave-ins. The angle of incline required to prevent a cave-in varies with differences in such factors as the soil type, environmental conditions of exposure, and application of surcharge loads.

"Stable rock" means natural solid mineral material that can be excavated with vertical sides and will remain intact while exposed. Unstable rock is considered to be stable when the rock material on the side or sides of the excavation is secured against caving-in or movement by rock bolts or by another protective system that has been designed by a registered professional engineer.

"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.

"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.

"Tabulated data" means tables and charts approved by a registered professional engineer and used to design and construct a protective system.

"Trench (Trench excavation)" means a narrow excavation (in relation to its length) made below the surface of the ground. In general, the depth is greater than the width, but the width of a trench (measured at the bottom) is not greater than 15 feet (4.6 m). If forms or other structures are installed or constructed in an excavation so as to reduce the dimension measured from the forms or structure to the side of the excavation to 15 feet (4.6 m) or less (measured at the bottom of the excavation), the excavation is also considered to be a trench.

"Trench box." See "Shield."

"Trench shield." See "Shield."

"Uprights" means the vertical members of a trench shoring system placed in contact with the earth and usually positioned so that individual members do not contact each other. Uprights placed so that individual members are closely spaced, in contact with or interconnected to each other, are often called "sheeting."

"Wales" means horizontal members of a shoring system placed parallel to the excavation face whose sides bear against the vertical members of the shoring system or earth.

16VAC25-170-20. Specific excavation requirements (29 CFR 1926.651). (Repealed.)

(a) Surface encumbrances. All surface encumbrances that are located so as to create a hazard to employees shall be removed or supported, as necessary, to safeguard employees.

(b) Underground installations.

(1) The estimated location of utility installations, such as sewer, telephone, fuel, electric, water lines, or any other underground installations that reasonably may be expected to be encountered during excavation work, shall be determined prior to opening an excavation.

(2) Utility companies or owners shall be contacted within established or customary local response times, advised of the proposed work, and asked to establish the location of the utility underground installations prior to the start of actual excavation. When utility companies or owners cannot respond to a request to locate underground utility installations within 24 hours (unless a longer period is required by state or local law), or cannot establish the exact location of these installations, the employer may proceed, provided the employer does so with caution, and provided detection equipment or other acceptable means to locate utility installations are used.

(3) When excavation operations approach the estimated location of underground installations, the exact location of the installations shall be determined by safe and acceptable means.

(4) While the excavation is open, underground installations shall be protected, supported or removed as necessary to safeguard employees.

(c) Access and egress.

(1) Structural ramps.

(i) 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.

(ii) Ramps and runways constructed of two or more structural members shall have the structural members connected together to prevent displacement.

(iii) Structural members used for ramps and runways shall be of uniform thickness.

(iv) 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.

(v) Structural ramps used in lieu of steps shall be provided with cleats or other surface treatments on the top surface to prevent slipping.

(2) Means of egress from trench excavations. A stairway, ladder, ramp or other safe means of egress shall be located in trench excavations that are 4 feet (1.22 m) or more in depth so as to require no more than 25 feet (7.62 m) of lateral travel for employees.

(d) Exposure to vehicular traffic. Employees exposed to public vehicular traffic shall be provided with, and shall wear, warning vests or other suitable garments marked with or made of reflectorized or high-visibility material.

(e) Exposure to falling loads. No employee shall be permitted underneath loads handled by lifting or digging equipment. Employees shall be required to stand away from any vehicle being loaded or unloaded to avoid being struck by any spillage or falling materials. Operators may remain in the cabs of vehicles being loaded or unloaded when the vehicles are equipped, in accordance with 16VAC25-175-1926.601(b)(6), to provide adequate protection for the operator during loading and unloading operations.

(f) Warning system for mobile equipment. When mobile equipment is operated adjacent to an excavation, or when such equipment is required to approach the edge of an excavation, and the operator does not have a clear and direct view of the edge of the excavation, a warning system shall be utilized such as barricades, hand or mechanical signals, or stop logs. If possible, the grade should be away from the excavation.

(g) Hazardous atmospheres.

Except as otherwise provided, requirements of the Virginia Confined Space Standard for the Construction Industry, 16VAC25-140-10 et seq., that are more stringent than corresponding requirements in this section shall apply to excavations which, while covered by this section, also meet the definition of "confined space" in 16VAC25-140-10.

(1) Testing and Controls. In addition to the requirements set forth in subparts D and E of this part (16VAC25-175-1926.50-1926.107) to prevent exposure to harmful levels of atmospheric contaminants and to assure acceptable atmospheric conditions, the following requirements shall apply:

(i) Where oxygen deficiency (atmospheres containing less than 19.5% oxygen) or a hazardous atmosphere exists or could reasonably be expected to exist, such as in excavations in landfill areas or excavations in areas where hazardous substances are stored nearby, the atmospheres in the excavation shall be tested before employees enter excavations greater than 4 feet (1.22 m) in depth.

(ii) Adequate precautions shall be taken to prevent employee exposure to atmospheres containing less than 19.5% oxygen and other hazardous atmospheres. These precautions include providing proper respiratory protection or ventilation in accordance with subparts D and E of this part (16VAC25-175-1926.50-1926.107) respectively.

(iii) Adequate precaution shall be taken such as providing ventilation, to prevent employee exposure to an atmosphere containing a concentration of a flammable gas in excess of 20% of the lower flammable limit of the gas.

(iv) 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.

(2) Emergency rescue equipment.

(i) Emergency rescue equipment, such as breathing apparatus, a safety harness and line, or a basket stretcher, shall be readily available where hazardous atmospheric conditions exist or may reasonably expected to develop during work in an excavation. This equipment shall be attended when in use.

(ii) Employees entering bell-bottom pier holes, or other similar deep and confined footing excavations, shall wear a harness with a lifeline securely attached to it. The lifeline shall be separate from any line used to handle materials, and shall be individually attended at all times while the employee wearing the lifeline is in the excavation.

(h) Protection from hazards associated with water accumulation.

(1) Employees shall not work in excavations in which there is accumulated water, or in excavations in which water is accumulating unless adequate precautions have been taken to protect employees against the hazards posed by water accumulation. The precautions necessary to protect employees adequately vary with each situation, but could include special support or shield systems to protect from cave-ins, water removal to control the level of accumulating water, or use of a safety harness and lifeline.

(2) If water is controlled or prevented from accumulating by the use of water removal equipment, the water removal equipment and operations shall be monitored by a competent person to ensure proper operation.

(3) If excavation work interrupts the natural drainage of surface water (such as streams), diversion ditches, dikes, or other suitable means shall be used to prevent surface water from entering the excavation and to provide adequate drainage of the area adjacent to the excavation. Excavations subject to runoff from heavy rains will require an inspection by a competent person and compliance with paragraphs (h)(1) and (h)(2) of this section.

(i) Stability of adjacent structures.

(1) 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.

(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:

(i) A support system, such as underpinning, is provided to ensure the safety of employees and the stability of the structure; or

(ii) The excavation is in stable rock; or

(iii) 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; or

(iv) A registered professional engineer has approved the determination that such excavation work will not pose a hazard to employees.

(3) 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.

(j) Protection of employees from loose rock or soil.

(1) Adequate protection shall be provided to protect employees from loose rock or soil that could pose a hazard by falling or rolling from an excavation face. Such protection shall consist of scaling to remove loose material; installation of protective barricades at intervals as necessary on the face to stop and contain falling material; or other means that provide equivalent protection.

(2) Employees shall be protected from excavated or other materials or equipment that could pose a hazard by falling or rolling into excavations. Protection shall be provided by placing and keeping such materials or equipment at least 2 feet (.61 m) from the edge of excavations, or by the use of retaining devices that are sufficient to prevent materials or equipment from falling or rolling into excavations, or by a combination of both if necessary.

(k) Inspections.

(1) Daily inspections of excavations, the adjacent areas, and protective systems shall be made by a competent person for evidence of a situation that could result in possible cave-ins, indications of failure of protective systems, hazardous atmospheres, or other hazardous conditions. An inspection shall be conducted by the competent person prior to the start of work and as needed throughout the shift. Inspections shall also be made after every rainstorm or other hazard increasing occurrence. These inspections are only required when employee exposure can be reasonably anticipated.

(2) Where the competent person finds evidence of a situation that could result in a possible cave-in, indications of failure of protective systems, hazardous atmospheres, or other hazardous conditions, exposed employees shall be removed from the hazardous area until the necessary precautions have been taken to ensure their safety.

(l) Fall protection.

(1) Walkways shall be provided where employees or equipment are required or permitted to cross over excavations. Guardrails which comply with 16VAC25-175-1926.500 through 16VAC25-175-1926.503 shall be provided where walkways are 6 feet (1.8 m) or more above lower levels.

(2) Adequate barrier physical protection shall be provided at all remotely located excavations. All wells, pits, shafts, etc., shall be barricaded or covered. Upon completion of exploration and similar operations, temporary wells, pits, shafts, etc., shall be backfilled.

16VAC25-170-30. Requirements for protective systems (29 CFR 1926.652). (Repealed.)

(a) Protection of employees in excavations.

(1) Each employee in an excavation shall be protected from cave-ins by an adequate protective system designed in accordance with paragraph (b) or (c) of this section except when:

(i) Excavations are made entirely in stable rock; or

(ii) Excavations are less than 5 feet (1.52 m) in depth and examination of the ground by a competent person provides no indication of a potential cave-in.

(2) Protective systems shall have the capacity to resist without failure all loads that are intended or could reasonably be expected to be applied or transmitted to the system.

(b) Design of sloping and benching systems. The slopes and configurations of sloping and benching systems shall be selected and constructed by the employer or his designee and shall be in accordance with the requirements of paragraph (b)(1); or, in the alternative, paragraph (b)(2); or, in the alternative, paragraph (b)(3); or, in the alternative, paragraph (b)(4), as follows:

(1) Option (1) - Allowable configurations and slopes.

(i) Excavations shall be sloped at an angle not steeper than one and one-half horizontal to one vertical (34 degrees measured from the horizontal), unless the employer uses one of the other options listed below.

(ii) Slopes specified in paragraph (b)(1)(i) of this section, shall be excavated to form configurations that are in accordance with the slopes shown for Type C soil in Appendix B to this chapter.

(2) Option (2) - Determination of slopes and configurations using Appendices A and B. Maximum allowable slopes, and allowable configurations for sloping and benching systems, shall be determined in accordance with the conditions and requirements set forth in appendices A and B to this chapter.

(3) Option (3) - Designs using other tabulated data.

(i) Designs of sloping or benching systems shall be selected from and be in accordance with tabulated data, such as tables and charts.

(ii) The tabulated data shall be in written form and shall include all of the following:

(a) Identification of the parameters that affect the selection of a sloping or benching system drawn from such data;

(b) Identification of the limits of use of the data, to include the magnitude and configuration of slopes determined to be safe;

(c) Explanatory information as may be necessary to aid the user in making a correct selection of a protective system from the data.

(iii) At least one copy of the tabulated data which identifies the registered professional engineer who approved the data, shall be maintained at the jobsite during construction of the protective system. After that time the data may be stored off the jobsite, but a copy of the data shall be made available to the Commissioner upon request.

(4) Option (4) - Design by a registered professional engineer.

(i) Sloping and benching systems not utilizing Option (1) or Option (2) or Option (3) under paragraph (b) of this chapter shall be approved by a registered professional engineer.

(ii) Designs shall be in written form and shall include at least the following:

(a) The magnitude of the slopes that were determined to be safe for the particular project;

(b) The configurations that were determined to be safe for the particular project; and

(c) The identity of the registered professional engineer approving the design.

(iii) At least one copy of the design shall be maintained at the jobsite while the slope is being constructed. After that time the design need not be at the jobsite, but a copy shall be made available to the Commissioner upon request.

(c) Design of support systems, shield systems, and other protective systems. Designs of support systems, shield systems, and other protective systems shall be selected and constructed by the employer or his designee and shall be in accordance with the requirements of paragraph (c)(1); or, in the alternative, paragraph (c)(2); or, in the alternative, paragraph (c)(3); or, in the alternative, paragraph (c)(4) as follows:

(1) Option (1) - Designs using appendices A, C and D. Designs for timber shoring in trenches shall be determined in accordance with the conditions and requirements set forth in appendices A and C to this chapter. Designs for aluminum hydraulic shoring shall be in accordance with paragraph (c)(2) of this chapter, but if manufacturer's tabulated data cannot be utilized, designs shall be in accordance with appendix D.

(2) Option (2) - Designs Using Manufacturer's Tabulated Data.

(i) Design of support systems, shield systems, or other protective systems that are drawn from manufacturer's tabulated data shall be in accordance with all specifications, recommendations, and limitations issued or made by the manufacturer.

(ii) Deviation from the specifications, recommendations, and limitations issued or made by the manufacturer shall only be allowed after the manufacturer issues specific written approval.

(iii) Manufacturer's specifications, recommendations, and limitations, and manufacturer's approval to deviate from the specifications, recommendations, and limitations shall be in written form at the jobsite during construction of the protective system. After that time this data may be stored off the jobsite, but a copy shall be made available to the Commissioner upon request.

(3) Option (3) - Designs using other tabulated data.

(i) Designs of support systems, shield systems, or other protective systems shall be selected from and be in accordance with tabulated data, such as tables and charts.

(ii) The tabulated data shall be in written form and include all of the following:

(a) Identification of the parameters that affect the selection of a protective system drawn from such data;

(b) Identification of the limits of use of the data;

(c) Explanatory information as may be necessary to aid the user in making a correct selection of a protective system from the data.

(iii) At least one copy of the tabulated data, which identifies the registered professional engineer who approved the data, shall be maintained at the jobsite during construction of the protective system. After that time the data may be stored off the jobsite, but a copy of the data shall be made available to the Commissioner upon request.

(4) Option (4) - Design by a registered professional engineer.

(i) Support systems, shield systems, and other protective systems not utilizing Option 1, Option 2 or Option 3, above, shall be approved by a registered professional engineer.

(ii) Designs shall be in written form and shall include the following:

(a) A plan indicating the sizes, types, and configurations of the materials to be used in the protective system; and

(b) The identity of the registered professional engineer approving the design.

(iii) At least one copy of the design shall be maintained at the jobsite during construction of the protective system. After that time, the design may be stored off the jobsite, but a copy of the design shall be made available to the Commissioner upon request.

(d) Materials and Equipment.

(1) Materials and equipment used for protective systems shall be free from damage or defects that might impair their proper function.

(2) Manufactured materials and equipment used for protective systems shall be used and maintained in a manner that is consistent with the recommendations of the manufacturer, and in a manner that will prevent employee exposure to hazards.

(3) When material or equipment that is used for protective systems is damaged, a competent person shall examine the material or equipment and evaluate its suitability for continued use. If the competent person cannot assure the material or equipment is able to support the intended loads or is otherwise suitable for safe use, then such material or equipment shall be removed from service, and shall be evaluated and approved by a registered professional engineer before being returned to service.

(e) Installation and removal of support.

(1) General.

(i) Members of support systems shall be securely connected together to prevent sliding, falling, kickouts, or other predictable failure.

(ii) 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.

(iii) Individual members of support systems shall not be subjected to loads exceeding those which those members were designed to withstand.

(iv) 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.

(v) Removal shall begin at, and progress from, the bottom of the excavation. Members shall be released slowly so as to note any indication of possible failure of the remaining members of the structure or possible cave-in of the sides of the excavation.

(vi) Backfilling shall progress together with the removal of support systems from excavations.

(2) Additional requirements for support systems for trench excavations.

(i) Excavation of material to a level no greater 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 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.

(ii) Installation of a support system shall be closely coordinated with the excavation of trenches.

(f) Sloping and benching systems. Employees shall not be permitted to work on the faces of sloped or benched excavations at levels above other employees except when employees at the lower levels are adequately protected from the hazard of falling, rolling, or sliding material or equipment.

(g) Shield systems.

(1) General.

(i) Shield systems shall not be subjected to loads exceeding those which the system was designed to withstand.

(ii) 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.

(iii) Employees shall be protected from the hazard of cave-ins when entering or exiting the areas protected by shields.

(iv) Employees shall not be allowed in shields when shields are being installed, removed, or moved vertically.

(2) Additional requirement for shield systems used in trench excavations. Excavations of earth material to a level not greater than 2 feet (.61 m) below the bottom of a shield shall be permitted, but only if the shield is designed to resist the forces calculated for the full depth of the trench, and there are no indications while the trench is open of a possible loss of soil from behind or below the bottom of the shield.

Appendix A to Subpart P

Soil Classification

(a) Scope and application

(1) Scope. This appendix describes a method of classifying soil and rock deposits based on site and environmental conditions, and on the structure and composition of the earth deposits. The appendix contains definitions, sets forth requirements, and describes acceptable visual and manual tests for use in classifying soils.

(2) Application. This appendix applies when a sloping or benching system is designed in accordance with the requirements set forth in 16VAC25-170-30 (b)(2) as a method of protection for employees from cave-ins. This appendix also applies when timber shoring for excavations is designed as a method of protection from cave-ins in accordance with Appendix C to Subpart P, and when aluminum hydraulic shoring is designed in accordance with Appendix D. This Appendix also applies if other protective systems are designed and selected for use from data prepared in accordance with the requirements set forth in 16VAC25-170-30 (c), and the use of the data is predicated on the use of the soil classification system set forth in this appendix.

(b) Definitions. The definitions and examples given below are based on, in whole or in part, the following: American Society for Testing Materials (ASTM) Standards D653-85 and D2488; The Unified Soils Classification System, The U.S. Department of Agriculture (USDA) Textural Classification Scheme; and The National Bureau of Standards Report BSS-121.

"Cemented soil" means a soil in which the particles are held together by a chemical agent, such as calcium carbonate, such that a hand-size sample cannot be crushed into powder or individual soil particles by finger pressure.

"Cohesive soil" means clay (fine grained soil), or soil with a high clay content, which has cohesive strength. Cohesive soil does not crumble, can be excavated with vertical sideslopes, and is plastic when moist. Cohesive soil is hard to break up when dry, and exhibits significant cohesion when submerged. Cohesive soils include clayey silt, sandy clay, silty clay, clay and organic clay.

"Dry soil" means soil that does not exhibit visible signs of moisture content.

"Fissured" means a soil material that has a tendency to break along definite planes of fracture with little resistance, or a material that exhibits open cracks, such as tension cracks, in an exposed surface.

"Granular soil" means gravel, sand, or silt, (coarse grained soil) with little or no clay content. Granular soil has no cohesive strength. Some moist granular soils exhibit apparent cohesion. Granular soil cannot be molded when moist and crumbles easily when dry.

"Layered system" means two or more distinctly different soil or rock types arranged in layers. Micaceous seams or weakened planes in rock or shale are considered layered.

"Moist soil" means a condition in which a soil looks and feels damp. Moist cohesive soil can easily be shaped into a ball and rolled into small diameter threads before crumbling. Moist granular soil that contains some cohesive material will exhibit signs of cohesion between particles.

"Plastic" means a property of a soil which allows the soil to be deformed or molded without cracking or appreciable volume change.

"Saturated soil" means a soil in which the voids are filled with water. Saturation does not require flow. Saturation, or near saturation is necessary for the proper use of instruments such as a pocket penetrometer or sheer vane.

"Soil classification system" means, for the purpose of this subpart, a method of categorizing soil and rock deposits in a hierarchy of Stable Rock, Type A, Type B, and Type C, in decreasing order of stability. The categories are determined based on an analysis of the properties and performance characteristics of the deposits and the environmental conditions of exposure.

"Stable rock" means natural solid mineral matter that can be excavated with vertical sides and remain intact while exposed.

"Submerged soil" means soil which is underwater or is free seeping.

"Type A" means cohesive soils with an unconfined compressive strength of 1.5 ton per square foot (tsf) (144 kPa) or greater. Examples of cohesive soils are: clay, silty clay, sandy clay, clay loam and, in some cases, silty clay loan and sandy clay loan. Cemented soils such as caliche and hardpan are also considered Type A. However, no soil is Type A if:

(i) The soil is fissured; or

(ii) The soil is subject to vibration from heavy traffic, pile driving, or similar effects; or

(iii) The soil has been previously disturbed; or

(iv) The soil is part of a sloped, layered system where the layers dip into the excavation on a slope of four horizontal to one vertical (4H:1V) or greater; or

(v) The material is subject to other factors that would require it to be classified as a less stable material.

"Type B" means:

(i) Cohesive soil with an unconfined compressive strength greater than 0.5 tsf (48 kPa) but less than 1.5 tsf (144 kPa); or

(ii) Granular cohesionless soils including: angular gravel (similar to crushed rock), silt, silt loam, sandy loam and, in some cases, silty clay loam and sandy clay loam.

(iii) Previously disturbed soils except those which would otherwise be classed as Type C soil.

(iv) Soil that meets the unconfined compressive strength or cementation requirements for Type A, but is fissured or subject to vibration; or

(v) Dry rock that is not stable; or

(vi) Material that is part of a sloped, layered system where the layers dip into the excavation on a slope less steep than four horizontal to one vertical (4H:1V), but only if the material would otherwise be classified as Type B.

"Type C" means:

(i) Cohesive soil with an unconfined compressive strength of 0.5 tsf (48 kPa) or less; or

(ii) Granular soils including gravel, sand, and loamy sand; or

(iii) Submerged soil or soil from which water is freely seeping; or

(iv) Submerged rock that is not stable; or

(v) Material in a sloped, layered system where the layers dip into the excavation or a slope of four horizontal to one vertical (4H:1V) or steeper.

"Unconfined compressive strength" means the load per unit area at which a soil will fail in compression. It can be determined by laboratory testing, or estimated in the field using a pocket penetrometer, by thumb penetration tests, and other methods.

"Wet soil" means soil that contains significantly more moisture than moist soil, but in such a range of values that cohesive material will slump or begin to flow when vibrated. Granular material that would exhibit cohesive properties when moist will lose those cohesive properties when wet.

(c) Requirements.

(1) Classification of soil and rock deposits. Each soil and rock deposit shall be classified by a competent person as Stable Rock, Type A, Type B, or Type C in accordance with the definitions set forth in paragraph (b) of this appendix.

(2) Basis of classification. The classification of the deposits shall be made based on the results of at least one visual and at least one manual analysis. Such analyses shall be conducted by a competent person using tests described in paragraph (d) below, or in other recognized methods of soil classification and testing such as those adopted by the American Society for Testing Materials, or the U.S. Department of Agriculture textural classification system.

(3) Visual and manual analyses. The visual and manual analyses, such as those noted as being acceptable in paragraph (d) of this appendix, shall be designed and conducted to provide sufficient quantitative and qualitative information as may be necessary to identify properly the properties, factors, and conditions affecting the classification of the deposits.

(4) Layered systems. In a layered system, the system shall be classified in accordance with its weakest layer. However, each layer may be classified individually where a more stable layer lies under a less stable layer.

(5) Reclassification. If, after classifying a deposit, the properties, factors, or conditions affecting its classification change in any way, the changes shall be evaluated by a competent person. The deposit shall be reclassified as necessary to reflect the changed circumstances.

(d) Acceptable visual and manual tests.

(1) Visual tests. Visual analysis is conducted to determine qualitative information regarding the excavation site in general, the soil adjacent to the excavation, the soil forming the sides of the open excavation, and the soil taken as samples from excavated material.

(i) Observe samples of soil that are excavated and soil in the sides of the excavation. Estimate the range of particle sizes and the relative amounts of the particle sizes. Soil that is primarily composed of fine-grained material is cohesive material. Soil composed primarily of coarse-grained sand or gravel is granular material.

(ii) Observe soil as it is excavated. Soil that remains in clumps when excavated is cohesive. Soil that breaks up easily and does not stay in clumps is granular.

(iii) Observe the side of the opened excavation and the surface area adjacent to the excavation. Crack-like openings such as tension cracks could indicate fissured material. If chunks of soil spall off a vertical side, the soil could be fissured. Small spalls are evidence of moving ground and are indications of potentially hazardous situations.

(iv) Observe the area adjacent to the excavation and the excavation itself for evidence of existing utility and other underground structures, and to identify previously disturbed soil.

(v) Observe the opened side of the excavation to identify layered systems. Examine layered systems to identify if the layers slope toward the excavation. Estimate the degree of slope of the layers.

(vi) Observe the area adjacent to the excavation and the sides of the opened excavation for evidence of surface water, water seeping from the sides of the excavation, or the location of the level of the water table.

(vii) Observe the area adjacent to the excavation and the area within the excavation for sources of vibration that may affect the stability of the excavation face.

(2) Manual tests. Manual analysis of soil samples is conducted to determine quantitative as well as qualitative properties of soil and to provide more information in order to classify soil properly.

(i) Plasticity. Mold a moist or wet sample of soil into a ball and attempt to roll it into threads as thin as ⅛-inch in diameter. Cohesive material can be successfully rolled into threads without crumbling. For example, if at least a two inch (50 mm) length of ⅛-inch thread can be held on one end without tearing, the soil is cohesive.

(ii) Dry strength. If the soil is dry and crumbles on its own or with moderate pressure into individual grains or fine powder, it is granular (any combination of gravel, sand, or silt). If the soil is dry and falls into clumps which break up into smaller clumps, but the smaller clumps can only be broken up with difficulty, it may be clay in any combination with gravel, sand or silt. If the dry soil breaks into clumps which do not break up into small clumps and which can only be broken with difficulty, and there is no visual indication the soil is fissured, the soil may be considered unfissured.

(iii) Thumb penetration. The thumb penetration test can be used to estimate the unconfined compressive strength of the cohesive soils. (This test is based on the thumb penetration test described in American Society for Testing and Materials (ASTM) Standard designation D24SS - "Standard Recommended Practice for Description of Soils (Visual - Manual Procedure).") Type A soils with an unconfined compressive strength of 1.5 tsf can be readily indented by the thumb; however, they can be penetrated by the thumb only with very great effort. Type C soils with an unconfined compressive strength of 0.5 tsf can be easily penetrated several inches by the thumb, and can be molded by light finger pressure. This test should be conducted on an undisturbed soil sample, such as a large clump of soil, as soon as practicable after excavation to keep to a minimum the effects of exposure to drying influences. If the excavation is later exposed to wetting influences (rain, flooding), the classification of the soil must be changed accordingly.

(iv) Other strength tests. Estimates of unconfined compressive strength of soils can also be obtained by use of a pocket penetrometer or by using a hand-operated shearvane.

(v) Drying test. The basic purpose of the drying test is to differentiate between cohesive material with fissures, unfissured cohesive material, and granular material. The procedure for the drying test involves drying a sample of soil that is approximately one inch thick (2.54 cm) and six inches (15.24 cm) in diameter until it is thoroughly dry:

(A) If the sample develops cracks as it dries, significant fissures are indicated.

(B) Samples that dry without cracking are to be broken by hand. If considerable force is necessary to break a sample, the soil has significant cohesive material content. The soil can be classified as an unfissured cohesive material and the unconfined compressive strength should be determined.

(C) If a sample breaks easily by hand, it is either a fissured cohesive material or a granular material. To distinguish between the two, pulverize the dried clumps of the sample by hand or by stepping on them. If the clumps do not pulverize easily, the material is cohesive with fissures. If they pulverize easily into very small fragments, the material is granular.

Appendix B to Subpart P

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 16VAC25-170-30 (b)(2).

(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 Subpart P.

(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.

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

(ii) 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 ½ horizontal to one vertical (½H:1V) less steep than the maximum allowable slope.

(iii) 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 16VAC25-170-20 (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 DEEP3

STABLE ROCK

VERTICAL

(90°)

TYPE A2

3/4:1

(53°)

TYPE B

1:1

(45°)

TYPE C

1-1/2:1

(34°)

NOTES:
1Numbers shown in parentheses next to maximum allowable slopes are angles expressed in degrees from the horizontal. Angles have been rounded off.
2A short-term maximum allowable slope of 1/2 H:1V (63°) is allowed in excavations in Type A soil that are 12 feet (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 3/4 H:1V (53°).
3Sloping 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 excavation 20 feet or less in depth shall have a maximum allowable slope of ¾:1.

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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 ½:1.

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2. All benched excavations 20 feet or less in depth shall have a maximum allowable slope of ¾ to 1 and maximum bench dimensions as follows:

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3. All excavations 8 feet or less in depth which have unsupported vertically sided lower portions shall have a maximum vertical side of 3½ feet.

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All excavations more than 8 feet but not more than 12 feet in depth which unsupported vertically sided lower portions shall have a maximum allowable slope of 1:1 and a maximum vertical side of 3½ feet.

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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 ¾:1. The support or shield system must extend at least 18 inches above the top of the vertical side.

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4. All other simple slope, compound slope, and vertically sided lower portion excavations shall be in accordance with the other options permitted under 16VAC25-170-30 (b).

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.

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

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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.

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4. All other sloped excavations shall be in accordance with the other options permitted in 16VAC25-170-30 (b).

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 1½:1.

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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 1½:1.

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3. All other sloped excavations shall be in accordance with the other options permitted in 16VAC25-170-30 (b).

B-1.4 Excavations Made in Layered Soils

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.

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2. All other sloped excavations shall be in accordance with the other options permitted in 16VAC25-170-30 (b).

Appendix C

Timber shoring for trenches.

(a) Scope. This appendix contains information that can be used when timber shoring is provided as a method of protection from cave-ins in trenches that do not exceed 20 feet (6.1 m) in depth. This appendix must be used when design of timber shoring protective systems is to be performed in accordance with 16VAC25-170-30 (c)(1). Other timber shoring configurations; other systems of support such as hydraulic and pneumatic systems; and other protective systems such as sloping, benching, shielding, and freezing systems must be designed in accordance with the requirements set forth in 16VAC25-170-30 (b) and (c).

(b) Soil classification. In order to use the data presented in this appendix, the soil type or types in which the excavation is made must first be determined using the soil classification method set forth in Appendix A.

(c) Presentation of information. Information is presented in several forms as follows:

(1) Information is presented in tabular form in Tables C-1.1, C-1.2, and C-1.3, and Tables C-2.1, C-2.2 and C-2.3 following paragraph (g) of the appendix. Each table presents the minimum sizes of timber members to use in a shoring system, and each table contains data only for the particular soil type in which the excavation or portion of the excavation is made. The data are arranged to allow the user the flexibility to select from among several acceptable configurations of members based on varying the horizontal spacing of the cross braces. Stable rock is exempt from shoring requirements and therefore, no data are presented for this condition.

(2) Information concerning the basis of the tabular data and the limitations of the data is presented in paragraph (d) of this appendix, and on the tables themselves.

(3) Information explaining the use of the tabular data is presented in paragraph (e) of this appendix.

(4) Information illustrating the use of the tabular data is presented in paragraph (f) of this appendix.

(5) Miscellaneous notations regarding Tables C-1.1 through C-1.3 and Tables C-2.1 through C-2.3 are presented in paragraph (g) of this appendix.

(d) (1) Basis and limitations of the data dimensions of timber members.

(i) The sizes of the timber members listed in Tables C-1.1 through C-1.3 are taken from the National Bureau of Standards (NBS) report, "Recommended Technical Provisions for Construction Practice in Shoring and Sloping of Trenches and Excavations." In addition, where NBS did not recommend specific sizes of members, member sizes are based on an analysis of the sizes required for use by existing codes and on empirical practice.

(ii) The required dimensions of the members listed in Tables C-1.1 through C-1.3 refer to actual dimensions and not nominal dimensions of the timber. Employers wanting to use nominal size shoring are directed to Tables C-2.1 through C-2.3, or have this choice under 16VAC25-170-30 (c)(3), and are referred to The Corps of Engineers, The Bureau of Reclamation or data from other acceptable sources.

(2) (i) Limitation of application. It is not intended that the timber shoring specification apply to every situation that may be experienced in the field. These data were developed to apply to the situations that are most commonly experienced in current trenching practice. Shoring systems for use in situations that are not covered by the data in this appendix must be designed as specified in 16VAC25-170-30 (c).

(ii) When any of the following conditions are present, the members specified in the tables are not considered adequate. Either an alternate timber shoring system must be designed or another type of protective system designed in accordance with 16VAC25-170-30.

(A) When loads imposed by structures or by stored material adjacent to the trench weigh in excess of the load imposed by a two-foot soil surcharge. The term "adjacent" as used here means the area within a horizontal distance from the edge of the trench equal to the depth of the trench.

(B) When vertical loads imposed on cross braces exceed a 240-pound gravity load distributed on a one-foot section of the center of the cross brace.

(C) When surcharge loads are present from equipment weighing in excess of 20,000 pounds.

(D) When only the lower portion of a trench is shored and the remaining portion of the trench is sloped or benched unless: The sloped portion is sloped at an angle less steep than three horizontal to one vertical; or the members are selected from the tables for use at a depth which is determined from the top of the overall trench, and not from the toe of the sloped portion.

(e) Use of tables. The members of the shoring system that are to be selected using this information are the cross braces, the uprights, and the wales, where wales are required. Minimum sizes of members are specified for use in different types of soil. There are six tables of information, two for each soil type. The soil type must first be determined in accordance with the soil classification system described in Appendix A. Using the appropriate table, the selection of the size and spacing of the members is then made. The selection is based on the depth and width of the trench where the members are to be installed and, in most instances, the selection is also based on the horizontal spacing of the cross braces. Instances where a choice of horizontal spacing of cross bracing is available, the horizontal spacing of the cross braces must be chosen by the user before the size of any member can be determined. When the soil type, the width and depth of the trench, and the horizontal spacing of the cross braces are known, the size and vertical spacing of the cross braces, the size and vertical spacing of the wales, and the size and horizontal spacing of the uprights can be read from the appropriate table.

(f) Examples to illustrate the use of Tables C-1.1 through C-1.3.

(1) Example 1.

A trench dug in Type A soil is 13 feet deep and five feet wide.

From Table C-1.1, four acceptable arrangements of timber can be used.

Arrangement # 1

Space 4 X 4 cross braces at six feet horizontally and four feet vertically

Wales are not required.

Space 3 X 3 uprights at six feet horizontally. This arrangement is commonly called "skip shoring."

Arrangement # 2

Space 4 X 8 cross braces at eight feet horizontally and four feet vertically.

Space 8 X 8 wales at four feet vertically.

Space 2 X 6 uprights at four feet horizontally.

Arrangement # 3

Space 6 X 6 cross braces at 10 feet horizontally and four feet vertically.

Space 8 X 10 wales at four feet vertically.

Space 2 X 6 uprights at five feet horizontally.

Arrangement # 4

Space 6 X 6 cross braces at 12 feet horizontally and four feet vertically.

Space 10 X 10 wales at four feet vertically.

Space 3 X 8 uprights at six feet horizontally.

(2) Example 2.

A trench dug in Type B soil is 13 feet deep and five feet wide. From Table C-1.2 three acceptable arrangements of members are listed.

Arrangement # 1

Space 6 X 6 cross braces at six feet horizontally and five feet vertically.

Space 8 X 8 wales at five feet vertically.

Space 2 X 6 uprights at two feet horizontally.

Arrangement # 2

Space 6 X 8 cross braces at eight feet horizontally and five feet vertically.

Space 10 X 10 wales at five feet vertically.

Space 2 X 6 uprights at two feet horizontally.

Arrangement # 3

Space 8 X 8 cross braces at 10 feet horizontally and five feet vertically.

Space 10 X 12 wales at five feet vertically.

Space 2 X 6 uprights at two feet vertically.

(3) Example 3.

A trench dug in Type C soil is 13 feet deep and five feet wide.

From Table C-1.3 two acceptable arrangements of members can be used.

Arrangement # 1

Space 8 X 8 cross braces at six feet horizontally and five feet vertically.

Space 10 X 12 wales at five feet vertically.

Position 2 X 6 uprights as closely together as possible.

If water must be retained use special tongue and groove uprights to form tight sheeting.

Arrangement # 2.

Space 8 X 10 cross braces at eight feet horizontally and five feet vertically.

Space 12 X 12 wales at five feet vertically.

Position 2 X 6 uprights in a close sheeting configuration unless water pressure must be resisted. Tight sheeting must be used where water must be retained.

(4) Example 4.

A trench dug in Type C soil is 20 feet deep and 11 feet wide. The size and spacing of members for the section of trench that is over 15 feet in depth is determined using Table C-1.3. Only one arrangement of members is provided.

Space 8 X 10 cross braces at six feet horizontally and five feet vertically.

Space 12 X 12 wales at five feet vertically.

Use 3 X 6 tight sheeting.

Use of Tables C-2.1 through C-2.3 would follow the same procedures.

(g) Notes for all tables.

1. Member sizes at spacing other than indicated are to be determined as specified in 16VAC25-170-30 (c).

2. When conditions are saturated or submerged use tight sheeting. Tight sheeting refers to the use of specially-edged timber planks (e.g., tongue and groove) at least three inches thick, steel sheet piling, or similar construction that when driven or placed in position provide a tight wall to resist the lateral pressure of water and to prevent the loss of backfill material. Close sheeting refers to the placement of planks side-by-side allowing as little space as possible between them.

3. All spacing indicated is measured center to center.

4. Wales to be installed with greater dimension horizontal.

5. If the vertical distance from the center of the lowest cross brace to the bottom of the trench exceeds two and one-half feet, uprights shall be firmly embedded or a mudsill shall be used. Where uprights are embedded, the vertical distance from the center of the lowest cross brace to the bottom of the trench shall not exceed 36 inches. When mudsills are used, the vertical distance shall not exceed 42 inches. Mudsills are wales that are installed at the toe of the trench side.

6. Trench jacks may be used in lieu of or in combination with timber cross braces.

7. Placement of cross braces. When the vertical spacing of cross braces is four feet, place the top cross brace no more than two feet below the top of the trench. When the vertical spacing of cross braces is five feet, place the top cross brace no more than 2.5 feet below the top of the trench.

V0140014.JPG, SIZE-44 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140015.JPG, SIZE-44 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140016.JPG, SIZE-44 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140017.JPG, SIZE-44 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140018.JPG, SIZE-44 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140019.JPG, SIZE-44 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

Appendix D

Aluminum hydraulic shoring for trenches.

(a) Scope. This appendix contains information that can be used when aluminum hydraulic shoring is provided as a method of protection against cave-ins in trenches that do not exceed 20 feet (6.1 m) in depth. This appendix must be used when design of the aluminum hydraulic protective system cannot be performed in accordance with 16VAC25-170-30 (c)(2).

(b) Soil Classification. In order to use data presented in this appendix, the soil type or types in which the excavation is made must first be determined using the soil classification method set forth in Appendix A.

(c) Presentation of information. Information is presented in several forms as follows:

(1) Information is presented in tabular form in Tables D-1.1, D-1.2, D-1.3 and D-1.4. Each table presents the maximum vertical and horizontal spacings that may be used with various aluminum member sizes and various hydraulic cylinder sizes. Each table contains data only for the particular soil type in which the excavation or portion of the excavation is made. Tables D-1.1 and D-1.2 are for vertical shores in Types A and B soil. Tables D-1.3 and D-1.4 are for horizontal waler systems in Types B and C soil.

(2) Information concerning the basis of the tabular date and the limitations of the data is presented paragraph (d) of this appendix.

(3) Information explaining the use of the tabular data is presented in paragraph (e) of this appendix.

(4) Information illustrating the use of the tabular date is presented in paragraph (f) of this appendix.

(5) Miscellaneous notations (footnotes) regarding Table D-1.1 through D-1.4 are presented in paragraph (g) of this appendix.

(6) Figures, illustrating typical installations of hydraulic shoring, are included just prior to the tables. The illustrations page is entitled "Aluminum Hydraulic Shoring; Typical Installations."

(d) Basis and limitations of the data.

(1) Vertical shore rails and horizontal wales are those that meet the Section Modulus requirements in the D-1 tables. Aluminum material is 6061-T6 or material of equivalent strength and properties.

(2) (i) Hydraulic cylinders specifications. Two-inch cylinders shall be a minimum 2-inch inside diameter with a minimum safe working capacity of no less than 18,000 pounds axial compressive load at maximum extension. Maximum extension is to include full range of cylinder extensions as recommended by product manufacturer.

(ii) Three-inch cylinders shall be a minimum 3-inch inside diameter with a safe working capacity of not less than 30,000 pounds axial compressive load at extensions as recommended by product manufacturer.

(3) Limitation of application.

(i) It is not intended that the aluminum hydraulic specification apply to every situation that may be experienced in the field. These data were developed to apply to the situations that are most commonly experienced in current trenching practice. Shoring systems for use in situations that are not covered by the data in this appendix must be otherwise designed as specified in 16VAC25-170-30 (c).

(ii) When any of the following conditions are present, the members specified in the tables are not considered adequate. In this case, an alternative aluminum hydraulic shoring system or other type of protective system must be designed in accordance with 16VAC25-170-30.

(A) When vertical loads imposed on cross braces exceed a 100 pound gravity load distributed on a one foot section of the center of the hydraulic cylinder.

(B) When surcharge loads are present from equipment weighing in excess of 20,000 pounds.

(C) When only the lower portion or a trench is shored and the remaining portion of the trench is sloped or benched unless: the sloped portion is sloped at an angle less steep than three horizontal to one vertical; or the members are selected from the tables for use at a depth which is determined from the top of the overall trench, and not from the toe of the sloped portion.

(e) Use of Tables D-1.1, D-1.2, D-1.3 and D-1.4. The members of the shoring system that are to be selected using this information are the hydraulic cylinders, and either the vertical shores or the horizontal wales. When a water system is used the vertical timber sheeting to be used is also selected from these tables. The Tables D-1.1 and D-1.2 for vertical shores are used in Type A and B soils that do not require sheeting. Type B soils that may require sheeting, and Type C soils that always require sheeting are found in the horizontal wale Tables D-1.3 and D-1.4. The soil type must first be determined in accordance with the soil classification system described in Appendix A. Using the appropriate table, the selection of the size and spacing of the members is made. The selection is based on the depth and width of the trench where the members are to be installed. In these tables the vertical spacing is held constant at four feet on center. The tables show the maximum horizontal spacing of cylinders allowed for each size of wale in the waler system tables, and in the vertical shore tables, the hydraulic cylinder horizontal spacing is the same as the vertical shore spacing.

(f) Example to illustrate the use of the tables:

(1) Example 1:

A trench dug in Type A soil is 6 feet deep and 3 feet wide. From Table D-1.1: Find vertical shores and 2 inch diameter cylinders spaced 8 feet on center (o.c.) horizontally and 4 feet on center (o.c.) vertically. (See Figures 1 & 3 for typical installations.)

(2) Example 2:

A trench is dug in Type B soil that does not required sheeting, 13 feet deep and 5 feet wide. From Table D-1.2: Find vertical shores and 2 inch diameter cylinders spaced 6.5 feet o.c. horizontally and 4 feet o.c. vertically. (See Figures 1 & 3 for typical installations.)

(3) A trench is dug in Type B soil that does not require sheeting, but does experience some minor raveling of the trench face. The trench is 16 feet deep and 9 feet wide. From Table D-1.2: Find vertical shores and 2 inch diameter cylinder (with special oversleeves as designated by footnote #2) spaced 5.5 feet o.c. horizontally and 4 feet o.c. vertically, plywood (per footnote (g)(7) to the D-1 Table) should be used behind the shores. (See Figures 2 & 3 for typical installations.)

(4) Example 4: A trench is dug in previously disturbed Type B soil, with characteristics of a Type C soil, and will require sheeting. The trench is 18 feet deep and 12 feet wide. Eight foot horizontal spacing between cylinders is desired for working space. From Table D-1.3: Find horizontal wale with a section modulus of 14.0 spaced at 4 feet o.c. vertically and 3 inch diameter cylinder spaced at 9 feet maximum o.c. horizontally. 3 X 12 timber sheeting is required at close spacing vertically. (See Figure 4 for typical installation.)

(5) Example 5: A trench is dug in Type C soil, 9 feet deep and 4 feet wide. Horizontal cylinder spacing in excess of 6 feet is desired for working space. From Table D-1.4: Find horizontal wale with a section modulus of 7.0 and 2 inch diameter cylinders spaced at 6.5 feet o.c. horizontally. Or, find horizontal wale with a 14.0 section modulus and 3 inch diameter cylinder spaced at 10 feet o.c. horizontally. Both wales are spaced 4 feet o.c. vertically. 3 X 12 timber sheeting is required at close spacing vertically. (See Figure 4 for typical installation.)

(g) Footnotes and general notes, for Tables D-1.1, D-1.2, D-1.3, and D-1.4.

(1) For applications other than those listed in the tables, refer to 16VAC25-170-30 (c)(2) for use of manufacturer's tabulated data. For trench depths in excess of 20 feet, refer to 16VAC25-170-30 (c)(2) and (c)(3).

(2) Two-inch diameter cylinders, at this width, shall have structural steel tube (3.5 X 3.5 X 0.1875) oversleeves, or structural oversleeves of manufacturer's specification, extending the full, collapsed length.

(3) (i) Hydraulic cylinders capacities. Two-inch cylinders shall be a minimum 2-inch inside diameter with a safe working capacity of not less than 18,000 pounds axial compressive load at maximum extension. Maximum extension is to include full range of cylinder extensions as recommended by product manufacturer.

(ii) Three-inch cylinders shall be a minimum 3-inch inside diameter with a safe work capacity of not less than 30,000 pounds axial compressive load at maximum extension. Maximum extension is to include full range of cylinder extensions as recommended by product manufacturer.

(4) All spacing indicated is measured center to center.

(5) Vertical shoring rails shall have a minimum section modulus of 0.40 inch.

(6) When vertical shores are used, there must be a minimum of three shores spaced equally, horizontally, in a group.

(7) Plywood shall be 1.125 in. thick softwood or 0.75 inch, thick, 14 ply, arctic white birch (Finland form). Please note that plywood is not intended as a structural member, but only for prevention of local raveling (sloughing of the trench face) between shores.

(8) See appendix C for timber specifications.

(9) Wales are calculated for simple span conditions.

(10) See Appendix D, item (d), for basis and limitations of the data.

V0140020.JPG, SIZE-44 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140021.JPG, SIZE-44 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140022.JPG, SIZE-44 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140023.JPG, SIZE-44 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140024.JPG, SIZE-44 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

Appendix E - Alternatives to Timber Shoring

V0140025.JPG, SIZE-37 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140026.JPG, SIZE-36 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

Appendix F - Selection of Protective Systems

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 16VAC25-170-30 (b) and (c).

V0140027.JPG, SIZE-32 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140028.JPG, SIZE-37 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

V0140029.JPG, SIZE-40 PICAS, TYPE-DPI

For Requirements for protective systems (29 CFR 1926.652), see Virginia Administrative Code print product.

CHAPTER 175
FEDERAL IDENTICAL CONSTRUCTION INDUSTRY STANDARDS

 

Subpart AA – Confined Spaces in Construction -

16 VAC25-175-1926.1200 through 16VAC25-175-1926.1213, Confined Spaces in Construction, §§1926.1200 - 1926.1213;

Subpart C – General Safety and Health Provisions -

16VAC25-175-1926.21, Safety Training and Education, §1926.21;

Subpart V–Electric Power Transmission and Distribution -

16VAC25-175-1926.953, Enclosed Spaces, §1926.953;

16VAC25-175-1926.968, Definitions, §1926.968;

Subpart P – Excavations -

16VAC25-175-1926.650 through 16VAC25-175-1926.652, Excavations, §§1926.650 - 1926.652;

Subpart S – Underground Construction, Caissons, Cofferdams and Compressed Air -

16VAC25-175-1926.800, Underground Construction, §1926.800;