Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at

April 1, 1994

                   Federal-State Operations

FROM:               H. BERRIEN ZETTLER, Deputy Director 
                   Directorate of Compliance Programs

SUBJECT:            Washington Inspection Procedures for Enforcing
                   Excavation Standards

The Washington directive, WRD 91-2B, addressing inspection procedures for enforcing the State's excavation standards has been reviewed as requested in your March 3 memorandum. Please be advised that our review revealed that the State's directive is essentially the same as OSHA's inspection procedures for enforcing the excavation standards (CPL 2.87). We concur with the Region's determination that the inspection procedures are at least as effective as the Federal.

If we can be of any further assistance, please contact Mr. Roy Gurnham or Mr. Dale Cavanaugh of my staff at (202) 219-8136.

March 3, 1994

                   Compliance Programs

FROM:               ZOLTAN BAGDY, Acting Director 
                   Federal-State Operations

SUBJECT:            Washington Inspection Procedures for Enforcing
                   Excavation Standards (Response to OSHA Instruction CPL 2.87)

Attached for your review is Washington's directive, WRD 91-2B, on inspection procedures for enforcing the State's excavation standards. Washington's excavation standards are different from the Federal. The Region finds the inspection procedures to be at least as effective as the Federal. Please let us know if you concur with the Region. If you find any section to be less effective than the Federal, please provide a reason why.

If there are any questions, please contact Carol Sanford on 219-7115.



WISHA Regional Directive

WRD 91-2B

SUBJECT: Inspection Procedures for Enforcing the Excavation Standards - Chapter 296-155 WAC, Part N.

I. Purpose: This WRD cancels WRD 91-2A issued February 12, 1991, and is reissued to reflect the amended Washington Administrative Code (WAC). This directive establishes inspection procedures and provides guidelines to ensure uniform enforcement of the excavation standards.

II. Background: The Occupational Safety and Health Administration after 15 years of experience involving the adopted federal standards for covered employees in the construction industry (36 CFR 25232 December 30, 1971) issued revised rules for Subpart P to 29 CFR 1926 (54 CFR 45894 October 31, 1989). OSHA Instruction CPL 2.87 was used as a guide in preparing this directive.

The final rule resolves many issues raised in earlier attempts to regulate this activity within the construction industry. Many of these issues involved previous decisions under the existing standard.

A. It is the intent of Chapter 296-155 WAC, Part N, to establish one set of requirements which are applicable to all excavations, including trenches.

B. Where compliance requirements are intended to be applicable only to trenches, the final rule makes it clear that these requirements apply only to those excavations which are also trenches.

III. Application:

A. Inspection Guidelines (compliance procedures):

1. Excavation Protection Programs: This standard provides requirements which allow employers flexibility in developing programs that provide effective protection for employees working in excavations. In addition to the standard itself, the preamble provides further guidance and rationale for changes in the existing standard.

2. Program Compliance: During all inspections at construction sites, where excavation standards are or will be applicable, compliance personnel shall ensure that compliance with Chapter 296-155 WAC, Part N, Excavations, is in accordance with the Operations Manual Chapter V.F.3.c. and h.

a. This review shall include any documentation by employers of the methodology and background information used to determine whether shoring systems are required and the type of systems used.

b. The compliance safety and health officer (CSHO) shall evaluate the employer's compliance with the specific requirements of the standard.

3. CSHO Responsibilities: The following procedural guidance provides a general framework that is designed to assist the CSHO with all inspections:

a. Ask the employer for the basis on which the employee excavation protection program related to the standard was developed.

b. Interview a representative cross-section of affected employees to verify the employer's program. This shall include an evaluation of the training of affected employees and the effectiveness of the employer's enforcement of its program. (See WAC 296-155-100 and 110).

c. Evaluate compliance with requirements for periodic inspection of excavations. (See WAC 296-155-655(11)(a))

d. Identify all persons (competent person, registered professional engineer, etc.) responsible for excavation activities and/or operations.

e. Evaluate compliance with training requirements identified by periodic inspections or changes in equipment and/or procedures. This shall include an evaluation of the effectiveness of the employer's inspection procedures and training program. for assessment and correction of situations resulting in near misses and/or injuries or circumstances indicating that modifications are necessary. (See WAC 296-155-100 and 110).

4. Specific Excavation Requirements:

a. Scope and Application: This subpart applies to all open excavations made in the earth's surface. Excavations are defined to include trenches. All trenches are excavations; all excavations are not trenches. (See WAC 296-155-650(1)).

NOTE: If installed form work or other similar obstructions reduce the depth-to- width dimensions for a particular excavation, it may become a trench as defined later in the specific requirements of this instruction.

b. Definitions: The definitions contained in the excavation standard shall be relied upon to interpret and apply the standard properly. In some cases, terms within a definition are themselves defined within the same section.

(1) Accented Engineering Practices: CSHOs shall verify with the employer which aspects of the employee protection system have been designed or approved by a registered professional engineer. The name of such individual, or if a firm, the firm's name, the name of the engineer of record who approved the work for the firm, and the registration number shall be recorded.

(a) Field offices may review any work which must be certified as to the status of such certification with the Department of Licensing professional engineering section.

(b) Verification shall also be made for all other aspects of the on-site excavation conditions which the employer indicates are under the direct supervision of a registered professional engineer.

i. All inquiries relating to the adequacy of the engineering design shall be referred to the regional office.

ii. In appropriate cases, the regional office may refer deficient or inadequate engineering designs of protective systems to the Department of Licensing.

(c) Any equipment, shoring devices, shields or other special aspects of an employer's excavation program in which the compliance investigation reveals the use of a Registered Professional Engineer shall be so noted on WISHA 1-B during the on- site investigation. If such devices, shields or other special aspects of the employer's program do not comply with the requirements of the standard, appropriate citations shall be issued.

(2) Competent Person: CSHOs shall pay particular attention to the investigation and documentation of data to establish that any person serving in this capacity possesses the capability of identifying existing and potential hazards for workers.

(a) To be a "competent person" under this standard, a person must have had training in and be knowledgeable of soils analysis, the use of protective systems, and the requirements of this standard.

(b) The competent person having such training and knowledge must be capable of identifying existing and predictable hazards in excavation work and have the authority to take prompt measures to abate these hazards. Thus, a backhoe operator who would otherwise meet the requirements of the definition is not a competent person if the person lacks the authority to take prompt corrective measures to eliminate existing or potential hazards.

(3) Hazardous Atmospheres: The CSHO shall check for hazardous or oxygen deficient atmospheres. For example, these include irritating atmospheres which could be encountered in areas close to a landfill where it is not uncommon to encounter hydrogen sulfide(H(2)S).

(4) Registered Professional Engineer: The CSHO shall determine that the Registered Professional Engineer of record is in fact working within a discipline applicable to the excavation work; i.e., it would be inappropriate for an electrical engineer to approve shoring design for an excavation. See also the definition for acceptable engineering practices in this instruction.

(5) Tabulated Data: The CSHO shall examine and ensure that all tabulated data for protective systems are approved by a Registered Professional Engineer.

NOTE: The use of tabulated data appearing in the appendices to this standard is excluded from this requirement.

c. General Requirements:

(1) Surface Encumbrances: The standard requires that all surface encumbrances that are located so as to create a hazard to employees shall have been removed or supported, as necessary, to safeguard employees. The requirement applies to all employers at the construction work site. (See WAC 296-155-655(1)).

(2) Underground Installations: The location of utility installations, such as sewer, telephone, fuel, electric, and water lines, or any other underground installations that reasonably may be expected to be encountered during excavation work, shall have been determined prior to opening an excavation. (See WAC 296-155-655(2)).

(a) The employer is required, while the excavation is open, to ensure that underground installations are protected, supported, or removed to safeguard employees from hazards. (See WAC 296-155-655(2)(d)).

(b) CSHO shall ascertain whether the employer has contacted the appropriate utility companies to establish the location of underground installations that may be encountered. (See WAC 296-155-655(2)(b)).

(c) When excavation operations approach the estimated location of underground installations, the exact location of the underground installation shall be determined by means that are safe to employees. (See WAC 296-155-655(2)).

(d) The CSHO shall determine that underground installations have been protected, supported, or removed as necessary to protect employees. (See WAC 296-155-655(2)).

(e) The sloped end of a trench, e.g., an earth ramp, may be considered a safe means of egress only if employees are able to walk the ramp in an upright manner when entering or exiting the trench.

i. The CSHO shall consider such factors as the degree of the slope, depth of the excavation, soil and environmental conditions, and the presence of any obstructions in determining whether or not the earth ramp can be used for safe egress.

ii. An employer may not use knotted rope lines to assist employees using sloped areas access to trenches.

iii. WISHA does not consider lifting equipment as "an other safe means of egress." For example, employees riding in a backhoe bucket to either enter or exit trench excavations, is not "other safe means of egress" for purposes of the standard. (See WAC 296-155-655(3)(b)).

(f) The prohibition against employees being under loads handled by lifting or digging equipment includes both excavated materials and slung loads (pipe, etc). (See WAC 296-155-655(5)).

(g) The CSHO shall ensure that an adequate warning system has been provided for mobile equipment operating adjacent to or without a clear view of the edge of excavations.

NOTE: This requirement does not apply to equipment used to push spoil back into the excavation for backfilling. (See WAC 296-155-655(6)).

(3) Hazardous Atmospheres: In addition to the requirements set forth in Parts B-1 and C-1 of Chapter 296-155 WAC, to prevent exposure to armful levels of atmospheric contaminants and to ensure acceptable atmospheric conditions, the following additional requirements apply: (See WAC 296-155-655(7)).

(a) Air quality tests shall be taken before employees enter excavations more than 4 feet in depth when a hazardous atmosphere exists or could be expected to exist.

(b) Tests shall be conducted as often as necessary to ensure the quality and quantity of the atmosphere. This includes checks for flammable gases and oxygen (O(2)) deficiency.

(c) Where hazardous atmospheres exist or may reasonably be expected to exist, emergency rescue equipment must be on the work site and readily accessible to employees. (See WAC 296-155-655(7)(b)(i))

(d) Daily inspections must be conducted by a competent person. Evidence of the lack of such inspections may include indication of failure of protective systems or employees exposed to hazardous atmospheres. (See WAC 296-155-655(11)).


d. Requirements for Protective Systems:

(1) When the employer has elected to protect employees by sloping, WAC 296-155-657(2)(a) requires that the slope be not steeper than 1.5H:1V "unless the employer uses one of the other options...."

(a) In a contested case proceeding once WISHA shows that no support system was used and that the sides of the excavation were steeper than 1.5H:1V the employer has the burden of showing its compliance with one of the other sloping options.

(b) The CSHO, however, shall, document all relevant facts to evaluate the hazard to obtain information which may be necessary for rebuttal of the employer's case.

(2) If the CSHO observes that a protective system appears inadequate or in danger of failure, the employer's representative or competent person shall be notified immediately in order to remove any employees in the excavation until such danger of failure has been abated. (See WAC 296-155-657(1)(b))

(3) In evaluating the design of sloping and benching systems, the CSHO shall refer to the decision chart found in Figure N- 28 of Appendix F, Selection of Protective System. (See WAC 296-155-657(2)(a) through (d)).

(4) In evaluating the design of support systems, shield systems and their protective systems, the CSHO shall refer to the decision chart found in Figure N- 29 of Appendix F, Selection of Protection Systems. (See WAC-296-155-657(2)(a) through (d)).

(5) The CSHO shall examine appropriate structural members of any protective system for damage or defects. (See WAC 296-155-657(4)(a)).

(6) Observation by CSHOs of excavations beneath the protective system requires confirmation that the support system was designed to resist forces calculated for the full depth of the trench. (See WAC 296-155-657(5)(b)(i) and (7)(b))


e. Appendices in the Standard:

(1) The following compliance guideline applies whenever CSHOs encounter excavation operations where employers have elected to provide protective systems using the appendices in this standard. CSHOs shall provide documentation, including soil tests where applicable, to support or reject the employer's decisions on protective systems.

(2) When the employer elects to use sloping option 2 or support option 1, the soils classification procedures are mandatory. Employer guesses or other shortcuts taken in classifying soils do not meet the intent of the standard.

(a) Thus, citations shall be issued where one or more provisions of Appendix A have been violated even if the degree of sloping turns out to be appropriate.

(b) Example: A backhoe operator slopes an excavation at what turns out to be an appropriate slope, but the operator is not a competent person within the meaning of the standard, and his determination was not based on both one visual and one manual test. WAC 296-155-657(1) will be cited, but the gravity of the violation will be reduced. (See WAC 296-155-657(1)(a)).


f. Appendix A to Part N - Soil Classification:

This appendix describes a method of classifying soil and rock deposits based on site and environmental conditions and on the structure and compaction of earth deposits. Appendix A contains further definition directly related to soil classification.

(1) The classification of soil and rock deposits shall be made based on the results of at least one visual and one manual test.

(a) Such analysis shall be conducted by a competent person using the tests described in subsection (4) of this appendix.

(b) The specific soil tests referenced in this appendix are given as examples for an employer to use in making a soil classification. However, other recognized methods of soil classification and testing, such or those adopted by the American Society for Testing Materials (ASTM), are acceptable for purposes of compliance with the standard

(c) The competent person conducting the soil classification may not base a classification by "feeling" the strength or composition of the soil through the use of heavy equipment.

i. This method is not an acceptable "other recognized method" of soil classification and testing" contemplated by Appendix A Subsection (3)(b).

ii. WISHA believes this is too indirect a method to classify properly the qualitative as well as the quantitative, properties of soil.

iii. For example, an employer may not classify the soil as Type A solely because its backhoe experienced difficulty digging the excavation.

(2) Each soil and rock deposit shall have been classified by a competent person as either stable rock, Type A, Type B, or Type C in accordance with the definitions set forth in subsection (2) of Appendix A.

(3) In a layered system, the system shall have been 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.

(4) If, after classifying soils and rock deposits, the properties, factors, or conditions affecting its classification change in any manner, such as after a rainstorm, such changes shall have been evaluated by the competent person on site. The soil and rock deposits shall have been reclassified as necessary to reflect any changed circumstances.


g. Appendix B to Part N - Sloping and Benching:

Under item (3)(c)(ii) of this appendix, whenever surcharge loads from stored material or equipment, operating equipment, or traffic are to be present, the competent person's determination of the degree to which the actual slope must be reduced below the maximum allowable slope shall have been based on the requirements set forth in (3)(c)(ii). The requirement to slope back in accordance with (3)(c)(ii) shall be triggered in situations where the surcharge loads cause signs of distress.


h. Appendix C to Part N - Tables:

The compliance officer should note that Tables N-2, N-3, and N-4 are actual size measurements based on mixed oak or equivalent with a bending strength not less than 850 psi. On the other hand, Tables N-5, N-6, and N-7 are nominal (S4S-Surface 4 Sides) measurements based on Douglas Fir or equivalent with a bending strength not less than 1500 psi.

i. Appendix D to Part N - Aluminum Hydraulic Shoring for Trenches:

This appendix contains criteria that can be used when aluminum hydraulic shoring is to be used as a method of protection in trenches not exceeding 20 feet in depth in the absence of manufacturer's tabulated data. The appendix is provided for those situations where manufacturers' data, permitted under WAC 296-155-657(3)(b), has been lost or is otherwise not available. When referenced, Appendix D must be used in conjunction with Appendix A, Soil Classification.

B. Training: Field inspection procedures must be modified to reflect the more technical nature of soils classification and protection system requirements of the new standard. To classify soils properly, visual and manual tests must now be performed. It is imperative that CSHOs be trained in the techniques used in these tests. The training program will consist of detailed instructions on the new standard and the compliance directive.

IV. Action: The information contained in the application section of this directive shall be used when evaluating compliance with Part N of Chapter 296-155 WAC. Technical inquiries may be made to the Standards and Information Section at (206) 956-5527.

V. Effective Date: This WISHA Regional Directive is, effective on December 8, 1992, and will remain in effect until cancelled.

J.N. Kirchoff, Assistant Director
Division of Industrial Safety and Health
Department of Labor and Industries
Post Office Box 44620
Olympia, Washington 98594-4620

Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.