Reference

« NBS ^

Publij^

* cations -r AlllOl 75fifi71

NBSIR 79-1935

Proceedings, Federal Workshop

on Excavation Safety,

September 1 9 and 20, 1 978

j

Lawrence A. Salomone and Felix Y. Yokel

Geotechnical Engineering Group

Structures and Materials Division

Center for Building Technology

National Bureau of Standards

Washington, D.C. 20234

December 1979

Prepared for Occupational Safety and Health Administration

Department of Labor

QC Washington, D.C. 20210

IGO

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79-1935

1979

AlllOS 0M7TSD

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NBSIR 79-1935

PROCEEDINGS, FEDERAL WORKSHOP

ON EXCAVATION SAFETY,

SEPTEMBER 19 AND 20, 1978

Lawrence A. Salomone and Felix Y. Yokel

Geotechnical Engineering Group

Structures and Materials Division

Center for Building Technology

National Bureau of Standards

Washington, D.C. 20234

December 1979

Prepared for Occupational Safety and Health Administration

Department of Labor

Washington, D.C. 20210

U S. DEPARTMENT OF COMMERCE

Luther H. Hodges, Jr., Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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ABSTRACT

A two-day workshop was held at the Department of Labor in Washington,

D.C., on September 19-20, 1978 to obtain opinions from knowledgeable people

on tentative conclusions and recommendations of a NBS Study on excavation

safety. The workshop agenda included a series of presentations on Tuesday,

September 19, 1978 and a series of group discussions on Wednesday,

September 20, 1978. The topic areas covered in the group discussions were:

1) Soil Classification

2) Acceptable Measures to Protect Workers Against Death or Injury by

Caving of Banks in Trenches and Excavations

3) Role of the Professional Engineer and Engineering Guidelines

This report summarizes and synthesizes opinions expressed in these group

discussions and presents comments provided by correspondence after the

two-day workshop.

Key Words: Acceptable Work Practices, Excavation, Geotechnical Engineering

Safety; Shoring; Soil Classification; Trench; Workshop.
TABLE OF CONTENTS

PAGE

ABSTRACT ill

1. INTRODUCTION 1

2. SUMMARY OF COMMENTS FROM THE WORKING GROUPS 1

2.1 GENERAL 1 2.2 SOIL CLASSIFICATION GROUP SESSION 2 2.3 ACCEPTABLE MEASURES GROUP SESSION 2 2.4 ROLE OF THE PROFESSIONAL ENGINEER GROUP SESSION 4

2.5 ADDITIONAL COMMENTS 5

APPENDIX A: LIST OF PARTICIPANTS A-1

APPENDIX B: PRELIMINARY NBS REPORT ON EXCAVATION SAFETY B-1

APPENDIX C: AGENDA C-1

APPENDIX D: COMMENTS PROVIDED BY CORRESPONDENCE AFTER COMPLETION

OF THE TWO-DAY WORKSHOP D-1
SUMt^RY OF FINDINGS AND RECOMMENDATIONS DISCUSSED AT THE FEDERAL WORKSHOP

ON EXCAVATION SAFETY - SEPTEMBER 19-20, 1978

1.0

INTRODUCTION

A two-day workshop was held at the Department of Labor in Washington,

D.C., on September 19-20, 1978, for the purpose of obtaining opinions

from knowledgeable people on tentative conclusions and recommendations

of a National Bureau of Standards [NBS] study on excavation safety.

Sixty-one participants including contractors, labor union representatives, industry representatives, professional engineers, government officials and interested persons from the academic community attended (Appendix A). A preliminary NBS report on excavation safety (Appendix B) was provided to the workshop participants to elicit comments during the workshop.

The NBS study consisted of three parts: A field study of present practice

in excavation, trenching, and shoring and of the impact of the Occupational Safety and Health Administration (OSHA) regulations as preceived

by contractors, labor unions and State and Federal enforcement agencies;

a study to assess the technical provisions in the present OSHA regulations and of available options for improving the soil classification

system and the technical provisions for sloping and shoring of trenches;

and a study of timber presently used for shoring to reasonably assess

the load carrying capacity of timber shoring systems.

The workshop agenda included a series of presentations of the various

phases of the NBS study on Tuesday, September 19, 1978, and a series

of group discussions on Wednesday, September 20, 1978 (see Agenda,

Appendix C). The topic areas covered in the group discussions were:

(1) Soil Classification

(2) Acceptable Measures to Protect Workers Against Death or Injury by

Caving of Banks in Trenches and Excavations

(3) Role of the Professional Engineer and Engineering Guidelines

This report summarizes and synthesizes opinions expressed in the group

discussions and presents comments provided by correspondence after the

two-day workshop (Appendix D).

2.0 SUMMARY OF COMMENTS FROM THE WORKING GROUPS

2.1 GENERAL

On Wednesday, September 20, 1978, the cliree working groups met to discuss

their topic area and the results were presented at a general session

meeting.

1
A sunimary of 'he findings and recotmnendat ions of each group is presented

below. The reader should refer to the preliminary NBS report on excavation safety (Appendix B) for a better understanding of the significance

of these comments.

2.2 SOIL CLASSIFICATION GROUP SESSION

Jack Mickle - Chairman

David Hadden - Secretary

' The points and recommendations made during this session were (refer to

Appendix B):

(1) Shape of Lateral Earth Pressure Diagram . (Page B-17) The rectangular shape is satisfactory. However, the effect of mobile surcharges on the shape of this diagram should be looked into.

(2) Slopes and Adjustments (Figures 1 and 2) . (Pages B-16 and B-17)

The compound shape for Case III in Figure 1 of the preliminary NBS report

was dropped from further consideration.

A maximum of three foot unshored subditch in a compound trench was recommended.

Shored compound trenches should have the shoring extending sufficiently

above the straight sides to prevent roll in of objects or spoil.

(3) Concepts of Equivalent Weights . (Pages B-9 and B-10) The concept

of equivalent weights (20, 40, 60j and 80 pcf) was accepted.

(A) Alternate Soil Classification Systems . (Pages B-24 to B-26) The

matrix system of soil classification was recommended. However, footnotes

or other methods should be used to draw attention to factors that may

affect the soil category.

(5) F ield Identification Tests. (Pages B-21 to B-24) The field identification tests (visual examination, pocket penetrometer and drying test)

referred to in the preliminary NBS report were accepted as the best available methods.

2.3 ACCEPTABLE MEASURES GROUP SESSION

George Bradberry - Chairman

Roy Gurnham - Secretary

The following points and recommendations were discussed in the order

listed:

1- The report and any proposed regulation should be divided I'lt i two

distinct subsections, one for trenching and one for excavations.

2
2. The terms "trench" and "excavation" must be clearly defined.

(a) The proposed trench definition says in part that a trench is an excavation which is longer than it is wide (Page B-44 in

Appendix B). The following problems arise with this definition:

1. Road cuts and building excavations would be included in

the scope.

2. Trench areas widened to accomodate manholes - these should

not be considered excavations.

3. This definition implies that only square excavations are not trenches.

(b) Trenching is normally a fast-moving progressive operation, and

usually employed to install utility lines. Excavation is

stationary construction.

(c) Do the proposed "long-term" and "short-term" definitions

adequately define the problem area? Time must be considered in

the regulations because long-term stresses in a cut are different from short-term stresses.

(d) The trench definition should be such that empirical data may be

used when shoring is designed. Criteria should be drafted to

determine when shoring is required for a range of anticipated

soil conditions.

(e) The definition of a trench should not limit its depth to 20

feet.

(f) Trenches must be covered at night - this could help distinguish

them from excavations.

3. The concern is employee safety. If no one will ever go into a trench then no shoring is required. OSHA'S responsibility is, to protect

the construction worker, not buildings nor the general public, from harm.

4. Manufactured shoring devices should be required to have a load capacity information plate. Load capacity of trench boxes should be expressed

in terms of lateral pressure resistance.

5. Load capacities of timber members need to be specified.

6. The regulations should not concentrate on timber shoring. Ail types

of shoring should be addressed. The best approach may be by specifying

performance requirements of any shoring system. For those systems not

specifically addressed in the code, an allowance for laboratory testing

and certification should be made. An equitable certification program is

needed

.

3
7. Do not allow sloped trenches in clay. Require shoring at all times.

8. Do not use the 5' maximum depth on compound slopes. Use 36" or 42"

(Page B-16 in Appendix B).

9. In the draft report, Section 1, Table 1 (Minimum Timber Shoring

Requirements), change the numbers 4' and 5' in footnote 1(d) to 36" or 42" (Page B-12 in Appendix B).

10. Allow bottom 5 feet of shoring to be removed to permit compaction

of lower levels of backfill.

2.4 ROLE OF THE PROFESSIONAL ENGINEER GROUP SESSION

Louis J, Thompson - Chairman

Brenda McCall - Secretary

The following points and recommendations were made during this session:

1) Engineers do not want the responsibility as "engineer of record"

without using a factor of safety of 3 to 4.

2) Presently, most engineers do not take OSHA into consideration, in

their plans.

3) In California, engineers will be called in only for an area "out-ofnorm."

4) In New Mexico, most design engineers refuse to design trench shoring

because they do not want the responsibility. The contractors stated that

they could not comply with OSHA and stay in buisness. (However, professionals in the utility business take all the precautions necessary.)

5) Most fatalities occur between 8-10 foot depths, not depths greater

than 20 feet,

6) The role of the engineer should be according to "standards of

practice" in an area. The designer (engineer) of the shoring or sheeting

system should not be considered the "engineer of record." The contractor

should have the responsibility because the contractor can require or request changes. In addition, the system may not be put in or maintained

properly.

7) One engineer discussed the METRO system which has proven to be suc- cessful. The engineer explained that in this system they did the investigation, they showed criteria on the plans that the contractors had to use in the design of the shoring and they required the contractor to hire

a geotechnical engineer.

4
8) A definition for "engineer of record" is needed. Some of the

engineers stated that the engineer should not be held liable for anything above the state-of-the-art and that his whole effort is designing

rather than construction. Engineers when taken to court cannot be held

liable unless their designs are proven to be inadequate. There was a plea for cooperation between engineers and contractors.

9) The word "certify" raises the question of whether, for instance, a certified trench box will work under all conditions. It can be certified that it meets all legal requirements of design, but not as to how

it is actually used.

10) It is traditional that the contractor bears all responsibility.

This started back in the 1700' s when the master builder was his own designer, engineer, builder, etc.

11) It was felt that the major issues were whether or not to require

an "engineer of record" for trenches:

(a) over 12 feet deep in soft clay

(b) over 20 feet deep in any other laaterial

(c) over feet deep for a long-term Cover 48 hours) periods

12) It was felt that the main problem;, \;ere as follows:

(a) there are many different types of excavations and conditions

(b) differentiating between an excavation and a trench.

13) Regarding the use of engineers for designing shoring or sheeting

systems, it was felt that the rule should be: if the contractor is not

in compliance with OSHA standards (or special conditions exist), an engineer must be required for cuts over 12 feet in clay or 20 feet in

any other material. The contractor should be given the option to follow

OSHA standards or use an engineer. NBS explained that their report was drawn up only for shallow depths - not greater than 20 feet.

2.5 ADDITIONAL COMMENTS

Following the workshop on September 19, and 20, 1978, additional comments

on the preliminary NBS report were received. The additional comments

were provided by:

(1) James H. Kleinfelder, ASFE, OSHA Committee.

(2) Leonard Freed, Ohio Contractors Associations.

(3) Thomas D. Searles, American Lumber Standards Committee.

(4) William L. Galligan, U.S. Dept, of Agriculture, Forest Service.

(5) Robert 0. Middleton, Speed Shore Corporation.

(6) Robert G. Griffith, National Utility Contractors Association

(7) James E. Hollis, Associated Contractors of New Mexico.

(8) W. M. "Red" Cass, Big Red Safety & Production, Inc.

(9) John P. Gnaedinger, Soil Testing Services, Inc.

These correspondence are provided in Appendix D.

5
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Appendix A

List of Participant

NAME ORGANIZATION AND ADDRESS TELEPHONE NO

Jeff Brewer

Gilbert L. Esparza

Area Director

Richard Tucker

George Bradberry

James Bryson

Bill Galligan

J. P. Ashooh

Karl Shipley

Brenda McCall

Clark Warfield

W. B. Braswell

James Schnabel

Irby L. McLane

Don Shay

Jim B. Kim

Associated General Contractors

of America

Brewer Construction

Oklahoma

OSHA,

Washington, D.C.

University of Texas

Austin, Texas

Star Route Box 285

Herbert, LA. 71436

NBS

Gaithersburg, MD.

U.S. Forest Service

P.O. Box 5130

Madison, WI. 53705

Associated General Contractors

of America

1957 E Street, N.W.

Washington, D.C. 20006

Associated General Contractors

of America

1957 E Street, N.W.

Washington, D.C. 20006

OSHA/Construction Standards

Washington, D.C. 20210

NBS

Gaithersburg, MD.

A. D. Beiro

Schnabel Engineering Assoc.

HCCA of Northern Virginia

and NVCA Safety Committee

OSHA/National Office

Washington, D.C.

Bucknell University

Lewisburg, PA.

405-787-4962

202-523-5224

512-471-1733

318-248-3113

301-921-2474

608-257-2211

202-393-2040

202-393-2040

202-523-8161

301-921-3366

751-6660

652-8430

703-273-6000

A-1
NAME ORGANIZATION AND ADDRESS TELEPHONE NO

Dr. Jack L. Mickle Iowa State University

Consulting with Building

and Construction Trades Dept.

AFL-CIO

Ames, Iowa 50011

Frank Kontouich OSHA/Richmond Area

Richmond, Virginia

782-2864

925-2864

Bert Hale Associated General Contractors

of America

Houston, Texas

713-676-4799

Michael Peeler N.C./OSHA 919-733-4880

Felix Y. Yokel NBS/Gaithersburg, MD. 301-921-3457

Jimmie Hinze University of Missouri 314-882-3301

B. R. Ertell Associated General Contractors

America

Stimm Assoc. , Inc.

Box 593

Buffalo, N.Y. 14240

of 716-681-8300

L. J. Thompson Texas A & M University

College Station 7784

Texas

845-3735

G. Phil Case National Loss Control Service,

8316 Arlington Blvd.

Fairfax, Virginia 22031

Corp. 203-698-8570

Larry Knab NBS/Gaithersburg, MD. 301-921-3208

W. A. Simms OSHA, National Office

Washington, D.C. 20210

202-523-8124

A. E. Martin OSHA, National Office

Washington, D.C. 20210

202-323-8ib2

D. W. Hadden OSHA, National Office

Washington, D.C. 20210

202-523-8161

C. P. Deane Virginia Department of Labor 804-786-5873

Box 12064

Richmond, Virginia 23241
NAME

C. G* Wicker

Michael Rodgers

James H* Cavender

Edwin €• Beethovea

Peter J. Ellis

William D« Rust, Jr*

Walt Percy

Dick Henstess

James H. Kleinfelder

Leo Quinlivan

Robert 0. Middleton

David 0* Plank

F. M. Livingston

Safety Director

ORGANIZATION AND ADDRESS

Virginia Department of Labor

Box 12064

Richmond, Virginia 23241

Virginia Department of Labor

Box 12064

Richmond, Virginia 23241

NIOSH

Rockville, MD.

GSA

National Utility Contractors

Association, Inc*

815 15th Street, N*W*

Washington, D*C* 20005

GSA/Public Building Services

Washington, D*C*

Brown & Root

Houston, Texas

Speed-Shore Corp

Atlanta, Georgia

James H* Kleinfelder & Assoc*

Chairman, Excavation Committee, ASFE

2825 East Mytle Street

Stockton, Ca* 95205

Occupational Health and Safety

Department - State Program

200 East Eight Avenue

P*0* Box 2186

Cheyenne, Wyoming 82002

Speed Shore

Houston, Texas

Speed Shore

Houston, Texas

Turner Construction Co*

150 E* 42nd* Street

New York, N*Y* 10017

TELEPHONE NO.

804-786-5873

804-786-5873

301-923-7595

202-737-0037

202-566-0714

713-67^-3382

404-955-2060

209-948-1345

307-777-7786

713-943-0750

713-943-0750

212-573-0466
NAME ORGANIZATION AND ADDRESS TELEPHONE NO

Tom Ervin

J. F. Gordon

R. A. Hewett

Jeffre C. Pullen

Munshi Rahman

A. L. Schmuhl

Director, Safety

Health Division

H. W. Hemsley

C. H. Wang

Deryle C. Cuddy

Timothy U. Cuddy

J im Lapping

Jack L. Mickle

John K. Barto

Bob Bros. Construction Co.

P.O. Box 53266

New Orleans, LA. 70153

Walsh Construction

National Forest Products Ass'n

Washington, D.C.

OSHA/National Office

Office of Education and Training

Washington, D.C. 20210

OSHA/National Office

Office of Education and Training

Washington, D.C. 20210

Associated General Contractors

and of America

1957 E. Street, N.W.

Washington, D.C. 20006

OSHA/National Office

Office of Field Coordination

Washington, D.C. 20210

OSHA/National Office

Office of Safety Standards

Washington, D.C. 20210

Arlington County

Dept, of Inspections

Safety Inspection

Arlington County Bldg.

Inspection

Arlington, Virginia

Bldg. Trade Department

815 16th Street, N.W.

Washington, D.C. 20006

Building Trade Department

815 16th Street, N.W.

Washington, D.C. 20006

OSHA/National Office

Washington, D.C. 20210

504-821-2400

549-6220

202-797-5880

202-523-7057

202-523-7065

202-393-2040

202-523-7226

558-2343

558-2521

202-347-1461

202-347-1461

202-523-8136
NAME PRGANIZATION AND ADDRESS TELEPHONE NO

Ronald R* Brandon

Larry E. Evans

Ben Hill

Noel Borck

Robert S. Dugan, Jr.

John Collins

NBS/Gaithersburg, MD.

Bureau of National Affairs, Inc.

lUOE

National Contractors Assoc* , Inc*

1101 15th Street, N.W.

Washington, D.C.

S. C. State/OSHA Office

Kent Nowlin Construction

301-921-3366

452-4319

347-8560

202-466-8880

758-3086

505-881-2511

NOTE: List of Participants was provided by OSHA in the order that the

attendees registered.
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Appendix B

Preliminary NBS Report on

Excavation Safety

NOTE: THE MATERIAL CONTAINED IN APPENDIX B WAS CIRCULATED TO WORKSHOP

PARTICIPANTS FOR DISCUSSION PURPOSES. IT WAS NOT INTENDED FOR

SUBSEQUENT USE FOLLOWING THE WORKSHOP.
m
SUMMARY OF FINDINGS AND

RECOMMENDATIONS TO BE DISCUSSED

AT THE FEDERAL WORKSHOP ON

EXCAVATION SAFETY

1. Introduction

The OSHA Regulations for Excavation, Trenching and Shoring were

promulgated in April 1971. In June 1976 OSHA engaged the National

Bureau of Standards to study the compatibility of the technical provisions in these regulations with actual construction practice and

with the state of knowledge in geotechnical and structural engineering,

to review the experience accumulated since their promulgation, and

recommend potential modifications that could improve their effectiveness.

The NBS study consisted of three parts: A field study of present

practice in excavation, trenching and shoring and of the impact of the

OSHA regulations as perceived by contractors, labor unions and State

and Federal enforcement agencies; a technical study consisting of the

assessment of the technical provisions in the present regulations and

of available options for improving the soil classification method and

the technical provisions for sloping and shoring; and a study of timber

presently used for shoring in order to reasonably assess the load

carrying capacity of timber shoring systems.

Findings and preliminary recommendations of the NBS study are

briefly summarized herein.

B-1
2 . Scope

The material In this summary Is presented in four sections:

Section 1 contains recommended options for improving the technical

provisions. It contains a summary of recommended acceptable practice.

Guidelines for the determination of compliance with acceptable practice

by licensed engineers are given in the Appendix.

Section 2 contains reconnended options for a soil classification system.

Section 3 contains reconmended allowable stresses and specifications for

timber.

Section 4 contains a summary of the field survey.

The material is presented to elicit critical comments which can be

discussed in detail in the workshop.

B-2
SECTION 1. Options for Improving the Technical Provisions in the

Regulations for Trenching and Shoring. (Summary of

recommended acceptable practice)

B-3
1 . General Definition:

Protective measures are deemed acceptable if they meet the

minimum requirements stipulated by OSHA. Acceptability does

not necessarily Insure that the measures are adequate under

all circumstances.

2 . Sloped Excavations ;

Sloped short-term excavations are acceptable If they comply

either with Condition 1 £r with Condition 2.

Condition 1; The excavation Is designed by a licensed

engineer in accordance with proposed guidelines (see

Appendix)

.

Condition 2: The slopes are no steeper than the stable slope

under the prevailing condition^^ and do not exceed the following allowable maximum slopes:

2 / Option 1:— 3/4 horizontal in 1 vertical (intact

rock is exempt from any maximum sloping provision)

.

—^ If there is any indication of general or local instability slopes shall

be cut back by at least 1/4 hor: 1 vert.

2 / — Option 1 is predicated on a simple soil classification scheme and on

the premise that maximum allowable slopes, like maximum speed limits, are not necessarily safe in all conditions.
Option 2.

3/ Soil Category^ Max. Slope, hor:vert.*

I

II

III

IV

1 / 2:1

3/4:1

1:1

2:1

* If significant vibration is present and/or trench is to be left

open for more than 4 hours add 1/4 to horizontal portion of

I and II and 1/2 to horizontal portion of III and IV.

Compound slopes shall comply with Fig. 1.

3. Shored Excavations

The following excavations shall be shored: All excavations deeper

than 5 ft which do not comply with the provisions for sloped

excavations except that unshored excavations deeper than 5 ft

are acceptable in sound unfractured bedrock.

The following shoring systems are acceptable:

1. Shoring systems designed by a licensed engineer in accordance

with proposed guidelines (see Appendix)

2. Timber shoring complying with Tables 1 and 2 and with the

specifications for trenching timber (see Section 3).

3. Shoring systems "designed to resist" the working loads

specified under the simplified procedure in 3(b).

2/ See Section 2 for Soil Classification.

B-5
The tenn "designed to resist*' shall be interpreted as follows:

(1) All structural members are designed by a licensed

engineer to resist the stipulated working load in accordance

with proposed Guidelines (See Appendix)

.

or (2) Structural members are rated to resist allowable

working loads equal to or greater than those caused by

the vertical and lateral loads stipulated in 3(b).

or (3) Shoring systems or protective devices are rated for

use under pre-defined conditions.

3(a) Rating

Rating of Structural Components or Assemblies which

are Part of the Shoring System .

Pre-fabricated components or sub-assemblies forming part

of the shoring system may be rated by a licensed engineer

and subsequently used to resist working loads equal to or

smaller than those for which they are rated.

Rating shall be as follows: Struts shall be rated for

their allowable compressive load. If struts are extendable,

the rating shall reflect the effect of length on load

capacity. Wales supported at given length intervals

shall be rated for allowable lateral load per linear

B-6
length of wale. For strut-wale assemblies, the wale

shall be designed to resist moments and shears not less

than 80 percent of those resulting from a load per linear

foot equal to the sum of the tributary allowable strut

loads divided by the length of the wale.

Rating may be accomplished by engineering analysis or

testing In accordance with the Engineering Guidelines

(See Appendix) . Rating of struts shall Include consideration of the 240 lb vertical downward load (See 3(b)).

Rating shall be valid for the period of time stipulated

by the licensed engineer or for one year, whichever Is

less, and shall be renewed after Inspection and, where

necessary, re-testlng. The rating and Its effective date

shall be permanently marked on the member or assembly.

Hydraulic shores shall be tested at least once a year to

1.25 times their allowable working load, and the load

shall be maintained for 5 minutes without any pressure

drop.

Fating of Shoring Systems and Protective Devices

Repetltlvely-used shoring systems or protective devices

such as trench boxes shall be rated by a licensed engineer

for allowable working loads or for predetermined conditions

of use.

B-7
Rating for conditions of use shall include designation of

aariaiLSB allowable depth and maximum value (See 3(b)).

Rating for allowable working load shall include the

designation of the allowable horizontal load per unit

area. Thus a trench box that can be used in a 10 ft deep

trench in soft clay may be rated as follows:

10 ft (see 3(b) for symbols)

w 80 Ib/ft^

e

Alternatively this trench box could be rated for an

2 allowable lateral pressure of 960 Ib/ft .

Rating of trench boxes and other protective devices shall

also consider loads other than lateral loads attributable

to construction and installation methods.

Trench boxes used at the bottom of sloped excavations

shall be rated for the full equivalent height or the

depth from the bottom of the excavations to level ground

whichever is less, and shall protrude not less than 1 ft

above the sldeslope of the excavation.

Rating shall be certified by a licensed engineer in

accordance with proposed Guidelines (see Appendix) and

shall be valid for a period not to exceed 1 year. The

rating and its effective date shall be permanently marked

on the protective device.

B-8
3Cb) Working loads to be used in the sintpllfled design

procedure.

Hie following loads shall be resisted simultaneously:

(1) a gravity load of 240 lb distributed over any 1 ft

length of any crossbrace.

(2) the lateral pressure p , distributed uniformly over

e the entire surface area cf the supported bank from the

bottom of the excavation to the top of the supported

portion of the bank (see Fig. 2).

Calculation of p^ (see also Figs. 2-4).

(H^ + 2) or (H^ whichever (eq. 1)

is greater

(the second equation will only govern if very heavy

equipment is used) (see Fig. 3)

H H (1 + 0.04 S) where 3

•* angle of slope with horizontal

ein degrees (eq. 2)

or H = H [1 + 2:(h/v)] (See Fig. 2) (eq. 3) e

fl « H when level ground is retained by shoring

eH need not exceed height from bottom of trench to level ground

e surface.

w is determined as follows:

e

B-9
Option 1 .

3 Under the water table or In soft clay: use v •80 Ib/ft

e Special condition for soft clay : All short term excavations

deeper than 12 ft and all long term excavations deeper than

5 ft shall be designed by a licensed engineer.

For short term excavations In hard Intact (unflssured)

3 cohesive soils: use w • 20 Ib/ft . e

In all other soils use w

e - 40 Ib/ft^

Option 2:

Soil Category w

' e

I 20

II 40

III 60

IV 80

*If significant vibration Is present and/or trerxh left

open more than 4 hours Increase by 25Z,

Loads tributary to members of the shoring system .

The following portion of the lateral loads caused by p^

shall be assumed to act on members of the shoring system:

100 percent of the tributary load shall be assumed to act

on all struts » 80 percent of the tributary load shall be

assumed to act on wales (vertical members directly supported

B-10
by struts shall be designed as vales)

,

tributary load shall be assumed to act

Tributary loads shall be calculated In

Figure 4.

67 percent of the

on sheeting,

accordance with

B-11
7AJU 1

MiKiMim UQcmiMzsrrs poi tzkbq sborimc ot tfj>ches •

1

1 HlnlBuB Strut and Wale Site

Trench Depth

(ft)

Soil y

b

Borlsoatal Centcr-to-Cencer Strut Spacing

a 10 12 14

(ft)

16 20

Cantcr-to-Centar

Vertical Wale Spacing (ft)

Klolma

Sscctini Tbicxnai

(In)

b-10 Type I A s b b z b b z 6 a z a 8 z a 10 z 10 10 z 10 5 2

S-10 n b z 6 b z a 8 z a a z 10 10 z 10 10 z U 12 z U 5 3

10-15 Type I 6 z b b z a a z a a z 10 10 z 10 10 z 12 — 5 2

10-15 Type Zl 6 z a a z a a z 10 10 z 10 10 z 12 12 z 12 — 5 3

15-20 Type 1 b z a a z a a z 10 10 z 10 10 z 12 12 z 12 — 5 3

15-20 TpT>e 11 z a a z 10 10 z 10 10 z 12 12 z U — — 5 3

\! («) AXl lunbcr dlKoaloas »r« actual.

(b) Strut Bices arc for 4 ft trench width. For wider tranches, oae Table 1-A.

(c) For spacing greater than 10 ft. Insert Interaedlata struts before workers

enter trenen.

(d) If vertical distance froa the center of the lowest strut to the bottoa of

the trench escceds 2 1/2 ft. sheeting shall be flral* eabedded or wudslll

ahall be used. The vertical distance frow the center of the lowest strut

to the bottca of the trenca shall not exceed 4 ft, or 5 ft If cjasill Is

usee.

(c) For skip bracing or clearance between sheeting In excess of 2 ft. sec Table 2.

2J Type 1 Soil Conditions: bottoa of excavation above the groundwater table. Soft claps arc under Type II conditions.

Type II Conditions: bottoa of excsvscion below ths groundwater csble or excavstlons In soft clap.

Special Coodltloti for Soft Clap: All trenches deeper than 12 ft shall be

dcalgned bp e licensed profceeloaal

engineer with geotechnical expertlea.

B-12
TABLE 1-A

ADJUSIMEJ^ OF STRUT SIZE FOR TRENCH WIDTH

Trancb

Width

(ft)

Strut Sixes (Reed Down for Equivalent Size)

Az4 Az6 6x6 ^6x8 6x6 6x 10 10 x 10 10 x 12 12 x 12

4x6 6x6 6x6 6x6 6x8 8x 10 10 x 10 10 x 12 12 x 12

6x6 6x6 6x8 6x6 6x8 8x 10 10 x 10 10 x 12 12 x12

12 6 x 6 6 x 8 8 x 6 8 x 6 8 x 10 10 x 10 10 x 12 12 x 12 12 x 12

15 6 x 8 8 x 8 8 x 8 8 x 10 10 x 10 10 x 10 10 x 12 12 x 12

B-13
•s V

TABLE 2

MQIDmH KZQOnEKDfTS ?C» TDffiEB SKIT BKACQIC -

Treoce

(it) Sell Trpa MinijBia Strut Slsa Mlnixua Slxa of Dpright HlCiXlB Walt Sitt

i Borlaootal Ccotcr-to-C«nt«r

Strut SpaclBf

4 ft 6 ft B ft

Horiioutxl Contar-to-Caotar Spacing

of Dprighta

2 ft 3 ft 4 ft 4 ft 8 ft

i

I

5-10 ard, Coapact 4 X A 2x4 Booa Baqulrad

3-10 Bard, Caa^ct 4x4 2x8 Mooe Baqulrad

10-13

1

Bard, Cc^act •4x4 2.4 Nooe Baqulrad

10-13 Bard, Co^act 4x4 3x8 Moot Baqulrad

5-10 Llkaly to CracA 4x4 2x4 4x4

10-13 LlAaly to CracA 4x4 4x4 2x4 4 s 6

(a) All Itmbar dlBcaatiooa ara actual . (b) Strut altaa ara for A ft traficb vldch.

For wldar Crancbaa. aac Table I'-A. (c) Vertical ceotar-to—ceatar apaclng of atruta and walaa aball oot ucaad 4 ft.

B-14
"lABLE 2-A

ADJUSTMENT OF STRUT SIZE FOR TRENCH WIDTH

Trench

Width

(ft)

Minimum Strut Size

4 •4x4 4x6

6 4x6 6x6

9 6x6 6x6

12 6x6 6x8

15 6x8 8x8

B-15
V

h

CASE I Ordinary Slope

Ratio h/v to be greater than the minimum allowable

CASE I - Ordinary slope

CASE II - Compound slope. Only the configuration shown is acceptable.

CASE III - Compound slope. Any configuration is acceptable provided

that : (1) No vertical bank exceeds 5 feet.

(2) The vertical distance must be compensated by an equivalent area of excavated material.

(3) The cross sectional area of the excavation must at

least equal area abed.

Finure 1. Minimum Recomnended Provisions for Sloped Excavations.

B-16
TOP CF SUPPORTED

PORTION OF BANK

H - H(1 + 0.046)

eor H H[1 + 2:(h/v)]

e

J/ We = Equivalent lateral pressure coefficient (Ib/ft3) depending on soil conditions.

Figure 2. Acceptable lateral working loads

B-17
h

H « actual height of surcharge (if any)

» height increase allowance for heavy e'^uiptuenf

where

I length of wheelbase, of vehicle

X “ distance from center of vehicle to side of trench

W gross weight of vehicle, lb

Figure 3. Acceptable Lateral Working Loads l^Jhen Heavy

Equipment is Used.

B-18
¥

. <*2/2 1

Strut 1

4 <*2/2

’ Strut 2

<*3/2 1

<*3/2

*

* Strut 3

<*4

J

<JI

<* 2/2

<* 2/2

^ 3/2

Hn

M/z

^ 4/2

•

Strut \

Strut 2

it

Strut 3

*

i’ Strut 4

CASE 1 . Sheeting is fiot

embedded.

CASE 2. Embedded sheeting

Note: Use mud sil! or equivolent

support unless sheeting

is firmty embedded.

Figure ^ - Lateral Loads Tributary to Members of the

Shoring System.

B-19
SECTION 2 . Soil Classification System

B-20
1.

Introduction

For brevity, most of the detail is omitted in this synopsis. The

following information is presented mostly in the form of charts

and tables. These are mostly self-explanatory, but may require

interpretation. Additional information will be given at the

Workshop.

2. Soil Classifications

Two alternate classification systems are proposed. The first,

termed the Matrix Classification System is shown in Tables 1 and 2.

A simplified alternate system is given in Table 3. Both systenjui

are based upon the field identification tests discussed in 3.

3. Field Identification Tests

Three primary tests are considered necessary for routine identification

and classification of soils as trench work progresses. Visual

examination can determine extensive qualitative information

regarding soil type, presence of fractures and discontinuities,

influence and location of water, and surrounding geographical

influences. Penetration tests, even crude ones, provide quantitative estimates of soil strengths. Drying tests are necessary

to differentiate between granular (non-cohesive) and cohesive

materials and to identify fissured materials.

3.1 Visual Examination

A visual examination should be continuously conducted as

trenching progresses. The visual examination will Identify

B-21
changes in soil through color variations, moisture variations,

bedding planes, fractures or Joints, apparent texture and

approximate strength information. The presence of water in the

trench is quite important. In particular, sections of open

trench should be studied to observe surface cracking or

revelling, which will indicate fractures and fissures in

cohesive materials. Samples of an apparently cohesive soil

in a relatively dry state will likely break along fissures or

fracture lines into clumps.

3.2 Pocket Penetrometer Test

A crude approximation of the unconfined compression strength

of a soil can be obtained by use of a pocket penetrometer.

The pocket penetrometer should be utilized in place, preferably

in the sides of a freshly opened trench. Tests should be made

at locations no further apart than 10 feet horizontally along

the trench. At each location, at least 2 tests should be

made on each side of the trench. Tests should be at the

approximate one-third points on both sides.

In lieu of a pocket penetrometer it is recommended that the

"Thumb Imprint" test be utilized (ASTM D2488) . Soils in which

thumb penetration requires a major effort are considered stiff.

Conversely, soils which can be penetrated to the knuckle with

ease shall be considered soft. All other soils, where penetration is obtained with moderate force, shall be considered as

medium strength.

B-22
3.3 Drying Test

The basic purpose of the drying test is to differentiate between

granular, cohesive materials with fissures, and intact cohesive

materials. The test must be conducted on undisturbed samples,

perhaps taken with an ordinary shovel, since they will Identify

fractures, fissures and slicken-sides in cohesive soils as

well as the coarse-grained component of other materials.

The procedure for the drying test involves drying a sample of

soil approximately one-half to one inch thick and six inches in

diameter. The sample can be dried in an oven (ASTM D2216),

by placing on a hot engine exhaust manifold for about an hour,

or by baking in the sun for a few hours during hot weather.

If significant fissures exist, they will become apparent upon

drying as the sample will crack along the weak fissures or

joints. If the sample dries to a hardened state intact, it

should be broken by hand as described in the following paragraph.

After drying, the sam.ple is grasped between the thumb and

forefinger of one hand and lifted so that a length of at

least 5 inches is cantilevering beyond the forefinger. If

the sample can be lifted intact without breaking, the soil

has a significant clay content and should be classified as

a soft, medium or stiff clay based upon its penetration test

r results. If the sample breaks upon lifting, it is either a

fissured clay or a granular material. Distinction between

a fissured clay and a granular material can be made by

B-23
f

attempting to pulverize the resulting dried clumps of material.

A simple means would be to squeeze them together in one hand.

(Even stepping on them is all right) . If they pulverize into

very small fragments, the material is granular. If the clumps

do not pulverize easily, the material is a fissured clay.

4. Alternate Classification Systems

4.1 Matrix Classification System

Table 1 Soil Categories

Primary Soil

Classif icatlon

Water in Trench?

No Yes

Fissures &/or Joints? Fissures &/or Joints?

No Yes No ? Yes

Rock I II II

1 III

Granular Soils II II III III

Stiff Clay I II III III

Medium Clay II III III IV

Soft Soils IV IV IV IV

Notes

1. Inclined layered systems. Layered systems shall be considered inclined when angle of dip is 4:1 (approximately 15°)

or larger. Weak side is side where layers dip into the trench,

and will be classified as a Category IV material regardless of

type of soil and site conditions. The strong side, dipping

away from the trench face, shall be classified using Table 1.

B-24
2. Horizontally-bedded, layered soils (dip less than 4:1 or

approximately IS"), and slope factors shall be interpolated

directly, based on the proportional thickness of the layers

making up the trench bank, except in the case where an extensive

layer of weak material is overlain by stronger material. In

those cases where a layer of weak material two feet or more

thick is overlain by stronger material, the w and slope of

the overlaying stronger material shall be taken to the same

as those of the underlying extensive layer of weaker material.

3. Disturbed material. All fill materials shall be treated

as Granular Soils.

Table 2 Minimum Acceptable Stability Requirements

/— —

Soil Category

1

w

e

2

Max. Slope

Horlz: Vertical

I 20 1/2:1

II 40 3/4:1

III 60 1:1

IV 80 2:1

Notes:

1. If significant vibration is present, and/or trench is to

be left open for more than 4 hours. Increase w^ factor by 25%.

2. If significant vibration is present, and/or trench is to be

left open for more than 4 hours, add 1/4 to the horizontal

portion for I and II soils. Add 1/2 to the horizontal portion

for III and IV soils.

B-25
4.2 Table 3 Simplified Classification System

Max.

Category Type w^, Ib/ft^

Slope

HoriztVert

A Intact Hard Soils 20 3/4:1

B Medium Soils 40 3/4:1

C Soft Clay and

Submerged Soils 80 —

Notes:

1. Intact hard soils are hard clays, tills and cemented

gravels above the groundwater table which have no fissures

or inclined layers which dip into the trench.

2. Soft clays have an unconfined compressive strength of less

than 1,000 psf and can be identified by penetrometer tests,

Torvane tests or laboratory tests.

3. Medium soils are all soils which do not fall in category

A or C.

4. Fractured rock falls in category B if it is dry and in

category C if it is submerged. Note that unless rock

excavation is by pre-splitting or equivalent means rock

will be normally fractured.

B-26
SECTION 3 Findings, Conclusions, and Recommendations

of Trenching Lumber Study

B-27
1 . Sunnnary

In certain areas of the United States lumber is used extensively to

brace trenches against collapse. The life and safety of the men working

in these trenches depends on the adequacy of the lumber bracing used to

prevent the trench from collapsing. NBS conducted a field study of

trenching lumber and found that either ungraded hardwood or graded

softwood is used.^^For graded softwood, allowable stresses and other

properties are established. The hardwood, however. Is ungraded and

there are no guidelines for allowable stresses and other properties.

The NBS statistical analysis of the hardwood grades based on the field

study indicated that 80^ percent of the pieces are a No. 2 grade or

higher; 60 percent of the pieces are a No. 1 grade or higher. These

percentages do not reflect the effects of wane and decay, which are

additional problems. NBS therefore recommended that allowable stresses

and other properties be based on a No. 2 minimum grade. It Is also

possible to base allowable stresses etc., on a No. 1 minimum grade,

dependent on the level of quality control. In either case, quality

control is necessary and can be Implemented In two steps.

Step 1 . A specification, which is part of the OSHA regulation

stipulating minimum quality, such as limits on wane, decay, and defects

and exclusion of weak species, based on a traditional strength ratio and

consistent with the stress level chosen.

Step 2 . Introduction of a voluntary grading system by industry,

which would insure the Step 1. specification for trenching lumber.

B-28
2. Scope

The study was performed in three steps:

(1) identification and investigation of properties and characteristics

of trenching lumber

(2) a field investigation at selected trenching lumber distribtuion

sites in Washington, D.C., Houston, Texas, and Los Angeles,

California.

(3) development of recommendations concerning allowable stresses

and minimum requirements and conditions of use for trenching

lumber.

3. Findings, Conclusions, and Recommendations

3.1 Critical Properties and Characteristics

o most of the hardwood and softwood limber used is rough sawn

and green

o the hardwood is ungraded (mill run) and consists of a variety

of species, with a high frequency of oak.

o much of the hardwood wales and sheeting are left in place

(not reused)

o some softwood is used in Los Angeles, San Francisco, New York

City, and Chicago.

o the softwood used in the West Coast is stress graded Douglas Fir.

Southern Pine and Douglas Fir are sometimes used in New York and

and Chicago.

o for solid sheeting, wales cause the most difficulty for contractors from a structural standpoint, struts next, and sheeting

the least difficulty.

B-29
3.2 Field Investigation

(a) Lumber Grade Disregarding Wane, Damage, and Decay - The most

important grade taken was a basic strength grade, called G, in which the

effects of wane, damage and decay were disregarded.

Table 1 shows the major findings for the G grade.

(b) Upgrading - Wales were attempted to be upgraded by assigning a

G grade to a partial length since the maximum bending stress occurs

in a partial length of a full length wale. The percent of wales

that could be upgraded ranged from about 15% - 40%.

(c) Wane - The frequency, severity and economic impact of wane

were shown to be significant for hardwood wales. Wane did not appear to

be a problem for the softwood wales. 42% of the hardwood wales and

struts were reduced by an average of 2 grades. 8% of the softwood wales

and struts were reduced by an average of 1 grade.

(d) Decay - About 10% of the hardwood wales and struts were downgraded

from their G grade, due to decay; on the average, wales and struts

were reduced at least 1 grade due to decay.

(e) Trimming - About 28% of the members in D.C., 15% in Houston,

and 14% in Los Angeles could be upgraded by trimming.

B-30
(f) Damage - About 2% of the hardwood and 4% of the softwood

wales, struts, and sheeting were downgraded due to damage.

(g) Species - At least 50% of the hardwood wales, struts, and sheeting

were either red or white oak. The softwood in Los Angeles was

Douglas Fir.

Slope of Grain - About 95% of the hardwood wales, struts, and sheeting

had a slope of grain of 1:20 or less.

Moisture Content - Almost all the lumber sampled was green.

3.3 Allowable Properties

(a) Hardwood Allowable Properties - Because formally approved lumber

stresses do not exist for most hardwood species, applicable ASTM

standards (D 2555, D245) were followed in conformance with procedures recognized under the American Lumber Standard PS 20-70 to

develop allowable stresses and other properties (Table 2).

(b) Softwood Allowable Properties - A minimum grade of No. 2 is

recommended for softwood wales and struts. Allowable stresses for

species and grade combinations are given in the National Design

Specifications for Wood Construction, National Forest Products

Association, June 1977. The same wane limitations which apply to

hardwood (3.3(c)) are recommended for softwood.

B-31
(c) Tentative specification for area loss by wane

(a) Performance specification

(1) For the middle 1/3 of the length of the member the

moment of inertia in any direction and the cross-sectional

area shall not be reduced by more than 10 percent.

(2) For the rest of the length of the member the moment

of inertia shall not be reduced by more than 25 percent

and the cross sectional area shall not be reduced by more

than 10 percent.

(b) Prescriptive Specification

(1) For the middle third: The sum of any two adjacent

sides must be at least 3/A of the sum of their specified

nominal lengths with the following exception: if wane is

confined to one corner only, the sum of the two adjacent

sides must be at least 2/3 of their specified nominal

lengths

(2) For the rest of the length of the member: The sum

of any two adjacent sides must be at least 2/3 of the sum

of their specified nominal lengths with the following

exception: if wane is confined to one corner only, the

sum of the two adjacent sides must be at least 1/2 of

their specified nominal lengths.

B-32
3.4 Use Recommendations

Use recommendations covering duration of load, damage, bark, decay.

Insect attack, inspectabllity, exposure, and storage for various

aspects of trenching lumber applications were developed. The

development assumes a severe environment, possible reuse of structural

members, and the need for structural integrity related to safety of

both life and property, for finite periods of time.

B-33
Table

1.

Summary

of

Findings

for G

Grade

for

l.'ales,

Struts,

and

Sheeting

T

Im o o

4-» o CO c a£

0) co X u

4-1 OO « c

«t>4 01

V

u !.< o «0 u > inU

•o 0)

01

X

X oc 00 to c 00 X

0)u •k

u

X

4J OC o 0> in in o

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u c tn 1 C 01 00

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CO c ^ OC rH U o 3

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B-3/t
Table 2

Allowable Unit Stresses for Hardwood Trenching Lur.be:—

‘

Hardwood group^^

^clL 1 U

E

2 TO 1 IN., THICK, 2 TO Ik IN. WIDE

White oo

875 575 550 105 355 800,000

Mixed 850 550 500 • 80 355 800,000

Mixed hardwoods 725 375 65 165 800,000

Mixed hardwoods 600 UOO 350 50 115 800,000

5 IN. AND THICKER, 5 TO 20 IN . WIDE

White o

o 975 650 525 120 355 800,000

f-iixed

I^/

925 625 i*75 90 355 800,000

Mixed hardwoods 800 550 350 75 165 800,000

Mixed hardwoods 675 1^50 325 6o 115 800,000

!_/ Ref. Southern Pine Inspection Bureau Grading Rules, 1977

edition, for general grade description as follows:

Grade Paragraph Size

No. 2 313 2 to U in. thick, 2 to in. vide

No. 2 3k 3 2 to J4 in. thick, 5 to li* in. vide

No. 2 SR koe 5 in. and thicker, 5 to 20 in. vide

Assumes 10-yr. load duration basis. For new (first use) lumber,

adjustments for load duration may be made: for 1-yr. duration multiply by 1.1; for 1 wk., multiply by 1.25 for 2 days, multiply by 1.30.

Load duration adjustments for used trenching lumber are not recommended.

For hardwood trenching lumber, requirements are waived for manufacture,

compression wood, firm knots, skips, stain, and warp. Holes limited

as knots; wane limited as 3.3(c).

Hardwood species defined per ASTM D ll65.

V White oak: The following white oaks~bur, chestnut, live,

overcup, post, swamp chestnut, swamp white, white.

V Mixed oak: Red oak (black, cherry bark, laurel, northern red,

pin, scarlet, southern red, water, willow); white oak (footnote 3).

^ Mixed hardwoods I: Ash (black, blue, green, Oregon); beech;

birch (sweet, yellow); cherry; elm (American, rock, slippery);

hackberry; hickory (mockernut, pignut, shagbark, shellbark); locust

(black, honeylocust ) ; magnolia (cucumber, southern, sweetbay); maple

(bigleaf, black, red, silver, sugar); mixed oak (footnote M; pecan

(bitternut hickory, nutmeg hickory, pecan, water hickory); red alder;

sassafrass; sugarberry; sweetgum; sycamore; tanoak; tupelo (black,

water); yellow poplar. Excludes all cottonwood, all aspen, basswood,

and balsam poplar.

f'iixed hardwoods II: All hardwoods in Mixed hardwoods I (footnote 5) plus black and eastern cottonwood; quaking and bigtooth

aspen; basswood. Excludes balsam poplar.

B-35
SECTION 4 . Summary of Field Study

B-36
1. Scope

One hundred meetings were held with top management of contracting firms in

9 metropolitan areas. Most of the meetings included field visits.

Additional information was obtained from trade associations. The

Information sought was in three areas:

Technical aspects of excavation work and associated hazards

Assessment of OSHA standards and suggested changes

Company characteristics and management practices affecting safety

2, Summary of Information

Trench Configurations

Most trenches are less than 15 ft deep, but few, other than waterlines are

less than 5 ft deep. A typical trench may be no wider than 3 ft and

the length of open trench behind the backhoe is generally less than

50 ft. The soil type encountered is an important factor causing

variations in work methods.

Shoring Types

Types of shoring systems vary considerably between contractors, even in

similar soil conditions. Various types of shoring are used. Including

timber shoring (solid sheeting and skeleton), hydraulic shores, trench

boxes and trench shield. The majority of trenches are not shored by

traditional timber shoring. Provisions for the removal of wood shoring

when the trench is filled vary among local governments and range from

provisions to leave shoring in place to provisions requiring removal

of shores. Several contractors indicated that timber shoring may be

used repeatedly.

B-37
Slope Determination

A majority of contractors rely on their experience and judgment

Determination of Required Shoring

Most contractors rely on experience and accepted local empirical practice.

A few firms use eningeering design. In a few instances (California,

Wisconsin, N. Y. City) Contractors derive satisfactory guidance from

state or Municipal regulations.

Soil Investigation

Contractors generally use test pits and borings. Although the majority

of contractors have in house engineers, many occasionally hire geotechnical consultants for the soils exploration, using the in house

engineers to design the shoring systems.

Hazards

Running sand is generally identified as the worst soil conditions. Other

hazards identified were areas which were previously excavated (sometimes

this condition is not known in advance), intersecting trenches and

groundwater. Causes of cave in include poor or unexpected soil conditions, excessive groundwater, incorrect assessment of soil conditions.

Failure to shore properly or failure to shore were most frequently cited.

OSHA Provisions

The majority of contractors stated that Table P-1 of the OSHA provisions

was not helpful. With some exceptions contractors were also not satisfied with Table P-2.

B-38
OSHA Inspection

Most contractors had at least one site inspection. Most felt that OSHA

regulation had generally an adverse effect by increasing production cost.

Most contractors were critical of inspection, citing a lack of connnon

sense as the key obstacle to meaningful inspection.

Assistance from Other Agencies

Much safety assistance is received from insurance carriers. Routine

advice is provided by equipment suppliers (hydraulic shores, etc.) and

by trade associations (NUCA, AGC)

.

Industry Characteristics

Utility contractors tend to be small (less than $5 million annual

volume), and specialize in only trenchwork. Their operations are

generally confined to a 50-mile radius. Most companies have less than

50 employees and a home office staff of no more than 4.

Safety Programs

Most contractors hold weekly "toolbox meetings." The rank of the

presiding individual may range from company president to foreman.

Many contractors do not seem convinced that the meetings have merit,

however, there is some disagreement on this point.

Safety Training

Company safety officers generally visit the jobsite frequently. Normally

these officers have also line duties. Sometimes this function is

B-39
performed by company presidents or owners. Safety training to foremen

is frequently provided by OSHA classes and first aide seminars.

Company Practices

Injury frequency is affected by some management practices and policies.

Practices which have beneficial effects are: to provide foremen with

little production cost information; not to have a dogmatic approach to

worker conflicts (consider worker complaints even if foreman is implicated)

to help new foremen who have supervisor problems rather than demoting them;

to limit the authority of foremen to fire workers.

Company Size

Smaller companies tend to have smaller injury frequencies. Parameters

affecting safety are familiarity with work area; specialization in

trench work; management control of field operation; and personnel.

Shoring Methods

More injuries occur when workers have to handle materials and equipment

manually rather than by machines.

B-40
APPENDIX

ENGINEERING GUIDELINES FOR THE DESIGN OF SHORING

SYSTEMS AND OTHER MEANS TO PROTECT

WORKERS IN TRENCHES AND EXCAVATION

B-41
1. INTRODUCTION

When workers are required to enter any excavation deeper than 5 feet,

protective measures must be taken In compliance with the OSHA Regulations

for Excavations, Trenching and Shoring. OSHA recognizes that In the case

of shallow trenches, where there Is rapid progress of work, it is in

many instances unrealistic to require that a licensed engineer

be In responsible charge of the design of the shoring for all the

portions of the excavation. It Is also noted that even If an engineer

designs the shoring under these conditions on the basis of soil exploration data, he has no knowledge of the subsurface conditions between

borings. OSHA therefore stipulated protective measures which are deemed °

acceptable. These Include the following: a maximum permissible slope

in sloped excavations; empirical provisions for timber shoring; shoring

systems designed to resist pre-defined lateral pressures which OSHA deems

acceptable for a wide range of conditions; pre-fabrlcated shoring systems

and protective devices such as hydraulic shores or trench boxes which

are rated for maximum allowable loads they may be used to support or maximum depths to which they can be used under certain pre-determlned

subsurface conditions.

In the following Instances a licensed engineer must be In responsible

charge of the design of shoring systems or other protective measures.

(1) Whenever the depth of the trench or excavation exceeds 20 ft

In all soils, or 12 ft in soft clays.

(2) Whenever there Is a deviation from the protective measures

which are deemed acceptable by OSHA.

(3) For all excavations defined herein as long-term excavations.

Furthermore, a licensed engineer will have to certify the rating of prefabricated shoring systems or trench boxes.

B-42
In some exceptional cases, it will be possible to modify the OSHA

stipulations for acceptability on a regional basis, when a well documented

case can be made by a licensed engineer on the basis of readily

Identifiable regional conditions and substantial past experience.

These guidelines are for professional engineers who design shoring

systems or other means to protect workers in excavations. The guidelines

are not meant to be a standard from which a professional engineer cannot

deviate. Rather, they convey minimum design loads and safety margins

which OSHA considers appropriate and design limit states which should be

considered. It is recognized that the design of shoring systems, the

stability analysis of slopes, and the assessment of soil conditions are not an eract science which can be approached with a set of rigid rules,

but rather an art which requires judgment, experience and recognition of

unique local conditions. Thus these guidelines can neither be imposed

as mandatory rules, nor can a professional engineer forego his responsibility to determine in each instance whether the stated guidelines provide

adequate protection.

2. Scope

The guidelines contain recommended minimum requirements for the

protection of workers in excavations against death and injury. They do

not cover other important parameters which an engineer must consider,

such as protection of adjacent structures, utilities and improvements

against damaging settlements, or effects of ground water fluctuations on adjacent properties.

Three methods of protection are considered in the guidelines.

Sloping of the banks of excavations;

Shoring;

Shielding of the work space by protective devices.

Other methods could also be used such as soil stabilization by freezing or grouting.

B-43
The guidelines do not apply to excavations whose collapse does not

endanger workers.

3. Definitions

Allowable Stresses are stresses %diich should not be exceeded under

the most critical combination of design loads.

Design loads are loads or load combinations used for design.

Load Capacity of a structural component of a shoring system is the

failure load which is expected to be equaled or exceeded by 95 percent

of all such components. Thus if a number of components are tested

the load capacity is determined as S > S(l-1.65 v) where:

S average load capacity

V coefficient of variation

S * load capacity

Long term excavations are all excavations which are open for more

than 48 hours. (24 hours were suggested)

Safety margin is the ratio between load capacity and the effect of

the most critical combination of design loads. In the case of stability a safety margin is the ratio between driving forces and resisting forces.

For excavation slope stability the safety margin can be taken as the ratio

between critical height and actual height.

Shoring Systems are structural systems supporting the bank of an excavation. The components of shoring systems are defined in Figure 1.

Short term excavations are excavations which are open for less than

48 hours. (24 hours?)

Trenches are short term excavations in which the bottom length

exceeds the bottom width, the bottom width is less than 15 feet and the

depth Is less than 20 feet.

B-44
UPRIGHT (WHEN SPACED)

FIGURE 1 COMPONENTS OF THE SHORING SYSTEM

B-45
Ultimate loads are working loads multiplied by the following

factors

:

1.7 for long term excavations

1.3 for short term excavations

Working Loads are loads which should reasonable be anticipated

and which must be resisted with appropriate safety margins. All loads

defined in the guidelines are working loads, unless otherwise noted.

4 . Design Loads

All the design loads listed, but not necessarily only the listed loads

should be considered. Unless specifically stated othen/lse in the design

criteria, the most critical combination of design loads should be considered. The design loads defined herein are working loads.

4.1 Soil and Water Loads

Loads caused by soil and water pressures should be calculated in

accordance with accepted engineering practice and these guidelines.

4.1.1 Loads Caused by Water

Hydrostatic loads, hydrodynamic loads and seepage forces should be

considered where applicable. Special attention should be given to the

effects of potential groundwater fluctuations, saturation of previously

drained deposits, and water penetration into fissures. The following

conditions are recommended as the basis for determining critical loads:

For long-term excavations: conditions caused by the 5-year flood.

For short-term excavation: conditions caused by the 1-year flood or alternatively the most severe condition which will not cause Interruption of work and evacuation of workers from the excavation.

B-46
4.1.2 Soil Loads

Soil loads should be determined In accordance with the state of the

art in geotechnical engineering. Special attention should be given to

fissures, planes of weakness and previously excavated soils. The fol>

lowing conditions are recommended as a basis for determining critical

loads

.

For long-term excavations: Drained as well as undralned conditions

need to be considered If applicable. Apparent cohesion should

not be assumed to contribute to shear strength. Effects of

exposure, lateral expansion, desiccation cracks, freezing,

erosion, and change In confining pressures should be taken Into

account.

For short-term excavations: In most Instances only undrained

conditions need to be considered. Short term strength characteristics

could be considered, provided that an adequate assessment

is made of conditions that could lead to loss of strength.

Further information is provided in Appendix A.

4.2 Surcharge Loads

Surcharge loads should be determined on the basis of actual anticipated working conditions. Consideration should be given to: the amount

and location of accumulated spoil material; stored construction material;

construction equipment; vehicular and human traffic; and foundations

adjacent to the excavation.

2

In no case shall the surcharge load be assumed less than 200 Ib/ft

distributed over the entire area or the equivalent of an additional 2 ft

depth of material excavated on the site (using average unit weight of

soil deposits), whichever is more.

B-47
4 .

3

Operational Loads

All loads caused by the anticipated excavations work must be considered.

These include excavated or construction material supported by portions of

the shoring system and workers climbing on the shoring system. The

following minimum load should be used for design: A gravity load of

240 lb, distributed over any 1 ft long portion of any strut.

4.4 Dynamic Loads

Dynamic loads caused by pile driving, blasting, traffic and construction

equipment should be considered.

4.5 Restraint loads . Restraint loads caused by temperature, moisture,

shrinkage, swelling or other dimensional changes in structural members

of the shoring system should be considered when applicable. In general

it can be assumed that the empirically-based lateral loads that can be

calculated in accordance with these guidelines contain a reasonable

allowance for temperature effects on struts.

5. Design Criteria

5.1 Sloped Excavations

5.1.1 Design Limit States :

1. Slope stability failure (part or all of the embankment)

2. Sloughing

5.1.2 Design Criteria

5. 1.2.1 Long-term Excavations

Granular soils (no cohesion)

slope angle should not exceed angle of Internal friction.

B-48
Cohesive Soils

The safety margin against stability failure should be greater

than 1.5.

Suitable surface and subsurface drainage should be provided to prevent

stability failures or sloughing induced by seepage or erosion.

For deep excavations

6 ft vide benches should be provided at vertical intervals nor exceeding 30 ft.

Maximum unbraced height of vertical bank:

5 ft for all soils or fractured rock. No limitation for sound

unfractured rock.

3. 1.2. 2 Short-term Excavations

The safety margin against stability failure should exceed 1.5 except

that for dry cohe^ionless soils a slope angle equal to the angle of

repose may be maintained. Short term strength properties could be

utilized, provided that there are adequate safeguards against conditions

which could cause strength degradation.

Maximum unbraced vertical bank: For intact hard clays the unbraced

height could exceed 5 ft provided that there is substantial empirical

evidence that the risk is not excessive. For all other soils, including

fractured rock, the maximum unbraced height should not exceed 5 ft.

There are no limitations for sound rock.

5.2 Braced Excavations

5.2,1 Design Limit States

(1) Stability failure of the bank

(2) Base instability

(3) Partial caving or sloughing of the bank between spaced vertical

or horizontal supports.

B-49
(4) Failure of the soil supporting struts anchors or soldier piles.

(5) Failure of structural components of the shoring system.

5,2.2 Design Criteria

5. 2. 2.1 Stability of the Bank

A stability failure of the bank is the collapse of all or part of

the bank caused by sliding of a soil mass along a failure surface. The

failure surface may lie outside the support points of structural members of

the shoring system (supports of raker braces, soil anchors or the bottom

of soldier piles or cantilever sheeting) and thus render the shoring

ineffective, or it may be caused by the structural failure of members of

the shoring system.

The safety margin against any stability failure of the bank shall

exceed 1.5.

5. 2. 2. 2 Base Stability

Base Instability leads to heaving of the base of the excavation, which

In turn can cause dislocation and collapse of the shoring system. The

safety margin against base Instability should exceed 1.5, Potential effects

of uplift resulting from artesian pressure In confined aquifers should be

considered. Dewatering should be adequate to prevent piping (quick condition)

caused by seepage of groundwater into the base of the excavation. In deep

clay deposits, base Instability should be considered a problem whenever N.

JJ ^ exceed the following values: N, > 6 for trenches where •= > 3; N. > 5.14

D jjD D for very wide excavations; intermediate values for 0 < — < 3

where N,

^ » stability number for base failure

s

3

Y • unit weight of soil, Ib/ft

H “ depth of excavation, ft.

B width of excavation, ft.

2

r - iiittlrn Iliad iilK^ar strength holow excavation base, Ib/ft
5. 2. 2.

3

Soil Stability Between Spaced Supports

There is no generally accepted theoretical approach by which the

ability of a soil to arch between successive supports can be evaluated or correlated with strength properties of the soil. There is empirical

evidence that short-term supports can be spaced up to 8 ft on center in

hard clay, very stiff sandy clays or glacial tills and 4 to 6 ft on center in slightly fissured stiff clays. Guidance can be derived on a regional basis from empirical evidence.

5. 2. 2.

4

Soil Support for Struts, Anchors or Soldier Piles

A minimum safety margin of 3 is recommended against bearing failures

of members of the shoring systems such as raker braces.

A safety margin of not less than 1.5 should be used when passive earth

pressure is relied upon to support embedded portions of soldier piles and

sheeting or deadmen.

All soil anchors should be proof load tested to 1.33 times their

working load. If the load capacity of soil anchors is determined by

tests, it should be not less than 1.5 times the working load for anchor

inclinations of 1 vertical in 2 horizontals or less, and increase to 2.0

times their working load for inclinations of 1 horizontal in 2 verticals.

When anchor capacity is determined by analysis the margin of safety

should not be less than 3. Soil anchors subjected to the working load

should not show measurable creep when the load is sustained for 15

minutes

.

5. 2. 2.

5

Design of Structural Components of the Shoring System

5. 2. 2. 5.1 Applicable Standards

Structural members should be designed in accordance with the following

standards:

B-51
Steel; Specifications for th'* Design, Fabrication and Erection of Structural

Steel Construction, American Institute of Steel Construction,

New Yoi'c, N. Y., Feb. 1969.

Concrete: Building Code Requirements for Reinforced Concrete, (ACT 318-71),

American Concrete Institute, Detroit, Michigan, November 1971.

Aluminum: Specifications for Aluminum Structures, The Aluminum Association,

New York, N. Y., November 1967.

Wood: National Design Specifications for Wood Construction, National

Forest Products Association, June 1977, for softwood lumber

stresses.

Because formally approved lumber stresses do not exist for most

hardwood species, applicable ASTM Standards may be followed in

conformance with procedures recognized under the American

Lumber Standard, PS70/70. (For allowable stresses refer to Section 3

Table 2)

5. 2. 2. 5. 2 Allowable Stresses

Allowable stresses should be determined in accordance with the

applicable standard. In long-term excavations allowable stresses should

not be exceeded under any applicable combination of working loads. In

short-term excavations allowable stresses in structural members may be

exceeded by up to 33 percent, however, allowable stresses should not be

exceeded in connections between structural members.

5. 2. 2. 5.

3

Ultimate Strength Design

Ultimate strength, rather than working stress design may be used

whenever such a procedure is stipulated in the applicable standard.

Ultimate loads should be taken as 1.7 times the working load for longterm excavations and 1.3 times the working load for short-term excavations.

B-52
5. 2. 2. 5. 4 Determination of Load Capacity by Test

If the load capacity of a structural component of the shoring system

is determined by test, the following minimum requirements are recommended:

1. Strength variability should be considered in accordance with the

definition of load capacity.

2. Under no circumstances should the allowable working load of struts exceed

67 percent cf mean failure load in temporary excavations or 50 percent of

the failute load in permanent excavations.

3. For cross braces (struts) the test load should be applied with an eccentricity of not less than 1/3 the thickness of the strut with respect

to any one cf the principal axes (but not simultaneously with respect to

both axes) , or with the eccentricity producing an end moment equal to the

center-span moment caused by a concentrated load of 340 lb applied at

the center of the strut, whichever is greater.

4. For wood members the provision of ASTM D2915 should serve as a guideline.

B-53
^ .1

/>i»b

. yq

>

- .C

APPENDIX A -.Jdaa*

r A OJ

*.' 30d

J,10O

' »lfj

B-54
A.l List of Symbols

B - Width of excavation

2 c - Cohesion (imdrained shear strength) of material in bank in Ib/ft

- Undralned shear strength of material below bottom of excavation in

Ib/ft^.

d - 0.707 X bottom width of excavation or depth from bottom of excavation

tc firmer soil stratum, whichever is less, in feet.

H - Depth of Excavation, in feet,

k - Coefficient of active earth pressure, as defined by pertinent equations

listed.

Ak - Additional increment of k as defined by Henkel (1971). 3 3

m - Coefficient in lateral force equation as defined by Peck (1969)

.

N Stability number, based on shear strength and weight of material in

the bank.

vH

Stability number, based on shear strength of material below bottom

of excavation and weight of material in bank.

N - Blowcount in standard penetration test using traditional U. S. methods

rope and cathead) in blows per foot.

y - Unit weight of soil (in natural condition or as assumed for worst case)

in Ib/ft^.

3

y

- Unit weight of saturated soil, in Ib/ft . S3 k 3

Ysub “ Unit weight of submerged soil in Ib/ft .

3

y^ - Unit weight of water in Ib/ft .

^ - Angle of internal friction, in degrees.

B-55
T 1 rji^sWrock:

B-56
A. 2 Refer^^nces

The following references provide guidance which is considered adequate.

Lateral loads calculated in accordance with these references are considered

to be working loads.

(1) Peck, R. B., "Deep Exckavations and Tunneling in Soft Ground," Stateof-tke-Art Report, Proceedings 7th International Conference on Soil

Mechanic's and Foundation Engineering, State-of-the-Art Volume,

pp. 225-250, Mexico, Cit>> (1989).

(2) Peck, R. B. , Hanson, W. E. , Thumburn, T. H., Foundation Enginee r ing , Chapter 27, John Wiley and Sons, New York, N. Y., Jan. 1974.

(3) Goldberg, D. T., Jaworski, W. E., and Gordon, M. D., Lateral Support

Systems and Underpinning, Report No. FHWA--RD-75-129 , Vol. II, Federal

Highway Administration, Office of Research and Development,

Washington, D.C. April, 1976.

(A) Department of the Navy, "Soil Mechanics, Foundations and Earth Structures,

NAVFAC DM-7, Chapter 10, U.S. Naval Publications and Forms Center,

Philadelphia, Pa., September 1971.

(5) United States Steel Company, "Steel Sheet Piling Design Manual,"

U.S. Steel, Pittsburgh, PA., July, 1975.

The preceding references contain design approaches which are not

necessarily identical. However, all these approaches are widely used and

are considered to be adequately conservative.

A. 3 Summary of Information

Hereafter is a brief summary of information derived from the references

listed in A. 2. The suggested pressure envelopes are not intended as an

B-57
endorsement of one single approach to the problem, but rather as a suaaaary of commonly used approaches vhlch are considered adequately

conservative.

A. 3.1 Lateral Pressures

(1) Sands (Ref A. 2-1)

065 Kq y

k ** tan^ (A5 - 4>/2) a

(2) Soft to Medium Clays, when N > 6 (if pressures calculated under (3)

using 0.4 yH are larger, use (3)).

N = ^c

When cut is underlain by deep, soft,

normally consolidated clays: m = 0.4

All other cases: m = 1.0

Alternate approach after Henkel (1971)-^

— Henkel, D. J., The Calculation of Earth Pressure in Open Cuts in

Soft Clays, The Arup Journal, Vol. 6 No. 4, (1971).

B-58
(3) Stiff Clays, whenever N < 4. (if 4 < N < 6 use (2) or (3), whichever

gives larger pressures)

2 /

(4) Dense cohesive sands, very stiff sandy clays.—

Relatively Uniform Upper Third of Cut

Dominated by Cohesionless Sands

B-59
Table A.l Typical Values of Unit Weight

Soil Type

Moist U.W. Above Saturated U.W. Belov

W.T., y(lbf/ft^) W.T., y^^^dbf/ft^)

Poorly graded sand

Clean well graded sands i

t Silty or clayey sands

Silty or clayey sands & gravel

Soft to medium clay

Stiff to very stiff clay

Organic silt or clay

105-115 115-125

115-125 125-130

120-130 125-135

125-135 130-145

100-115 100-115

110-125 110-125

90-100 90-100

^sub ''^sat

y - 62.4 Ib/ft^ w

Table A. 2 Relationship between Properties of Cohesionless Soil and

Standard Penetration Test Results

Soil Type

SPT, N

blows/f t.

Relative

Density

D 1

X

<t> (after Peck) k

a

Very loose sand <4 0-15 29* >0.35

Loose sand 4-10 15-35 29“-30‘* 0.35-0.33

Medium dense sand 10-30 35-65 30“-36“ 0.33-0.26

Dense sand 30-50 65-85 36"-41- 0.26-0.21

Very dense sand >50 85-100 >41* <0.21

B-60
Table A. 3 Properties of Cohesive Soli and Standard Penetration Test

Results (Goldberg, et al., 1976)

^ Undralned Unconflned

Clay SPT,M Shear Str. Conrp. Str.

Consistency Identification blows/ft. Ibf/ft^ Ibf/ft^

Very sofi Easily penetrated several

inches by fist.\ Exudes

between fingers when

squeezed in hand.

<2 250 <500

Soft Easily penetrated several

Inches by thumb. Molded

by light finger pressure

2-4 250-500 500-1000

Medium Can be penetrated several

inches by thumb with moderate effort. Molded by

strong finger pressure

4-8 — 500-1000 1000-2000

Stiff Readily idented by thumb

but penetrated only with

great effort. Idented

by thumb

8-15 1000-2000 2000-4000

Very stiff - Readily indented by

thumbnail

15-30 2000-4000 --.4000-8000

Hard Indented with difficulty- - >30 >4000 -- >8000

The correlation between N values and soil properties for clays can

be regarded as no more than a crude approximation, but for sands It Is

often reliable enough to permit the use of N values in design. Unconfirmed

compression tests or triaxial teste are more reliable for clays. It

should also be noted that the value of H can be influenced by numerous

factors such as: the depth at which the test is made; the location of

the water table; presence of boulders In the deposits; irregularities

in performing' the teat; etc. In general,' N values used here are

representative of those obtained by the traditional U. S. (rope and

cathead) method. If other methods are used, a correction for delivered

energy is desirable.

B-61
Appendix C

AGENDA
WORKSHOP

OSHA/NBS TRENCHING AND EXCAVATION RESEARCH

Department of Labor Auditorium

Washington, D.C.

AGENDA

Tuesday, September 19, 1978

8:30 A.M, - Registration

9:15 A.M. - Welcome A. Martin

9:20 A.M. - Industry Remarks T. Seymour

9:35 A.M. - Purpose of Workshop J. Bryson

9:50 A.M. - Overview of Excavation Project F. Yokel

10:30 A.M. “ Coffee

10:50 A.M. - Tentative Recommendations F. Yokel

11:30 A.M. - Discussion

12:00 - Lunch

1:30 P.M. - Soil Classification System R, Tucker

2:00 P.M. - Discussion of Soil Classification Options

2:30 P.M. - Timber Study L. Knab and

W. Galligan

3:00 P.M. - Discussion of Timber Recommendations

3:30 P.M. - Field Study J. Hinze

4:00 P.M. - Discussion of Field Study

4:30 P.M. - Form Working Groups

Suggest three working groups:

1. Soil Classification

2. Acceptable Measures

3. Trenching Timber

4:45 P.M. - Adjourn

C-1
WORKSHOP

9:00 A.M.

11:00 A.M

12:00

OSHA/NBS TRENCHING AND EXCAVATION RESEARCH

Department of Labor Auditorium

Washington, D.C.

AGENDA

Wednesday, September 20, 1978

Working Groups meet

Report of Working Groups and Discussion

Adjourn

C-2
Appendix D

Comments Provided by

Correspondence after Completion of

the Two-day Workshop

ASSOCIATION OF SOIL AND FOUNDATION ENGINEERS

October 16, 1978

The National Bureau of Standards

Room 168, Building 226

Washington, D. C. 20324

Attention: Mr. Felix Yokel

Dear Felix

Enclosed is a copi> of your draft on the technical provisions

of trenching and excavations for OSHA with our committee's

comments. I have asterisked the upper right-hand corner of all

pages which contain our recommended rewording. Some of the

changes made in the rough draft are made without comment.

Comments and discussions on the main items are listed below.

Section One

Under the heading "Rating of Shoring Systems and Protective

Devices," we would recommend that you change the word "Certified

by Licensed Engineer" to "Based on a professional opinion of a Licensed Engineer." We recommend this wording change because of

the inherent legal exposure attached to the word "Certify."

Section Two

We recommend that the matrix soil classification system be

used rather than the more simplified soil classification system,

even though we recognize that training of contractors and foremen

will be required. In addition, the committee felt that the rock

classification system be reviewed.

Appendix

We recommend that the title of the Appendix be changed to

"Engineering Guidelines for the Design of Shoring Systems and

Other Means to Minimize Mass Soil and Rock Movements". The

purpose of this rewording is to inform everyone of exactly what

the Design Engineer will do. We do not see the Engineer or

Engineering Geologist being involved in anything except mass

soil and rock movement. The term "Other Protective Measures"

could refer to all trench or excavation safety. Along this

D-1

8811 COLESVILE ROAD / SUITE 226 / SILVER SPRING. MARYLAND 20910 / (301) 566-2733
The National Bureau

of Standards

October 16, 1978

PAGE TWO

same line, we believe a comment should be put into the introduction of this section stating that the contractor is responsible

for trench safety. I believe the construction industry is in

agreement with this.

Part 3 - Ultimate Loads

There was some question as to how the factors of 1.7 and

1.3 were derived. This did not seem to be a critical item,

however

.

Part 4.4 - Dynamic Loads

The wording was changed again because of legal ramifications.

Part 5. 1.2,1 - Long-Term Excavations

It was felt that the safety margin could be reduced to below

1.5 if the excavation was monitored by instrumentation or other

means. The thinking being that stability factors of 1.5 are

commonly used in earth dams and this stability factor can be

reduced to 1.3 under the case of rapid drawdown, and 1.1 in the

case of partial drawdown and seismic loads.

Under "Rock Excavations"

We have added the phrase "No limitations for sound rock as

determined by a competent Geotechnical Engineer or Engineering

Geologist." This wording was added because of the questions that

arose regarding your definition of sound unfractured rock.

Under Part 5. 2. 2. 4 - Soils Support for Struts, Anchors or Soldier

Piles

A minimum safety margin of 2 in lieu of the 3 shown is

recommended.

Appendix A - Under Part A. 2 - References

We thought it would be desirable to add Joe DeSalvo's paper

to the reference list if possible.

D-2
The National Bureau

of Standards

October 16, 1978

PAGE THREE

We trust that you find the work of our corrmittee beneficial

and I would appreciate being kept abreast of the progress of the

OSHA regulations, particularly if regional meetings throughout

the U. S. are going to be held as discussed in the workshop. If

we can be of any other assistance, please contact me.

Very truly yours

,

14 - Kleinfelder Chairman

A^FE OSHA Committee

JHK : j cb

Enclosure

cc w/Enclosure: Mr. John Bachner

Mr. James Schnabel

Mr. Gardner Reynolds

Mr. John Gnaedinger

Mr. William Zoino

D-3
1 . General Definition:

Protective measures are deemed acceptable if they meet the

minimum requirements stipulated by OSHA. Acceptability does

not necessarily Insure that the measures are adequate under

all circumstances.

2. Sloped Excavations :

Sloped short-term excavations are acceptable if they comply

either with Condition 1 0£ with Condition 2.

Condition 1: The excavation is designed by a licensed

engineer in accordance with proposed guidelines (see

Appendix)

.

Condition 2: The slopes are no steeper than the stable slope

under the prevailing condltlon^^ and do not exceed the following allowable maximum slopes:

2 / Option 1:— 3/A horlzontal-~ln-l-vertical (intact

rock 'is exempt from any maximum sloping provision).

1 /

y

If there is any indication of general or local instability slopes shall

be cut back by at least 1/A hor: 1 vert.

, ^ aJdiha^ol

Option 1 la predicated on a simple soil classification scheme and on the premise that maximum allowable slopes, like maximum speed limits,

are not necessarily safe In all conditions.

D-4
Ilatlrtg for conditions of use shall Include designation of

&t«ixiiBuis allowabxe depth and maxiausn value (See 3(b)).

Rating for allowable working load shall include the

designation of the allowable horizontal load per unit

area. Thus a trench box that can be used in a 10 ft deep

trench in soft clay oay be rated as follows:

" 10 ft (see 3(b) for symbols)

- 80 Ib/ft^

Alternatively this trench box could be rated for an

2 allowable lateral pressure of 960. Ib/ft .

Rating of trench boxes and other protective devices shall

also consider loads other than lateral loads attributable

to construction and installation methods.

Trench boxes used at the bottom of sloped excavations

shall be rated for the full equivalent height or the

depth from the bottom of the excavations to level ground

whichever is less, and shall protrude not less than 1 ft

above the sideslope of the excavation.

Rating shall be^^rtifled )by a licensed engineer in

accordance with proposed Guidelines (see Appendix) and

shall be valid for a period not to exceed 1 year. The

rating and its effective date shall be permanently marked

on the protective device.

D-5
APPENDIX

ENGINEERING GUIDELINES FOR THE DESIGN OF SHORING

SYSTEMS. AND OTHER MEANS TO -PROTECT - A9/^*S5

SOIL /^rVO

WORKERS IN TRENCHES -Airo EXCAVATION

NOT FOR PyeUCATION

OR FOR REFERENCE

D-6
1. INTRODUCTION

Vhen workers are required to enter any excavation deeper than 5 feet,

protective neasures must be taken in compliance vlth the OSHA Regulations

for Excavations, Trenching and Shoring. OSHA recognizes that in the case

of shallow trenches, where there is rapid progress of work, it is in

many instances unrealistic to require that a licensed engineer

be in responsible charge of the design of the shoring for all the

portions nf th«i excavation. It is also noted that even if an engineer

designs the shoring under these conditions on the basis of soil exploretion data, he has no knowledge of the subsurface conditions between

borings. OSHA therefore stipulated protective measures which are deemed

acceptable. These include the following: a maxiixmm permissible slope

in sloped excavations; empirical provisions for timber shoring; shoring

systems designed to resist pre-defined lateral pressures which OSRA deems

acceptable for a wide range of conditions; pre-fabrlcated shoring systems

and protective devices such as hydraulic shores or trench boxes which

are rated for maximum allowable loads they may be used to support or

maximum depths to which they can be used under certain pre-determlned

subsurface conditions.

In the following -Instances a licensed englneer^must be In responsible

charge of the design of shoring systems or <^hsr-protce t ive noa cure»w andiQr s/of?cS, *

(1) Whenever. the depth of the trench or excavation exceeds 20 ft

In all soils, or 12 ft in soft clays.

(2) Whenever there is a deviation from the protective measures

which are deemed acceptable by OSHA. —For all eKcave tlons daflnad herein ao long-t-erm-exeavat-lons-.

Furthermore, a licensed engineer will have to^^rtify the rating of prefabricated shoring systems or treno^ boxes.

D-7
In none exceptional c&sea. It will be possible to nodlfy the OSHA

stipulations for acceptability on a regional basis, when a veil documented^

case can be made oy a licensed engineer on the basis of readily

identifiable regional conditions and substantial past experience.

These guidelines are for professional engineers vho design shoring

systems or other means to protect workers in excavations. The guidelines

are not meant to be a standard from which a professional engineer cannot

deviate. Rather, they convey minlmuo design loads and safety marglns*<«—

which OSHA considers appropriate and design llx^t states which should be

considered. It Is recognized that the design of shoring systems, the

stability analysis of slopes, and the assessment of soli conditions are

not an exact science which can be approached with a set of rigid rules,

but rather an art which requires judgment, experience and recognition of

unique local conditions. Thus these guidelines can neither be Imposed

as mandatory rules, nor can a professional engineer forego his responsl*

blllty to determine in each Instance whether the stated guidelines provide

adequate piofui-tiwa. C7rC /e.

Vs

I s

2. Scope

The guidelines, contain i^coms^nded minimum requirements fee the tSOt/a trocJC

protf eti on nf wnrlroro in- excavationa -agains t -aeath' -and injury.' They do

not cover other lnq>ortant parameters which an engineer must 'consider.

such as protection of adjacent structures', utilities and Improvements

against damaging settlements, or effects of ground water fluctuations on . . adjacent properties, ^ ys/ <s/^r

Three methods of protection are considered in the guidelines. . ^Ay7/h/m/2/t^j ^o// a roc^/t /novemenTS

Sloping of the banks of excavations;

Shoring;

Shielding of the work space by protective devices.

Other methods could also be used such as soil stabilization by freezing or grouting.

D-8
A. 3 Operational Loads

All loads caused by the anticipated excavations vork must be considered.

These L^.nclude excavated or construction material supported by portions of

the shoring system and vorkers clliabing on the shoring system. The

follc:#lng minimum load should be used for design: A gravity load of

2A0 lb, distributed over any 1 ft long portion of any strut.

A . A Dynamic Loads

equlpme^lt should be considered.

A. 5 Restraint loads . Restraint loads caused by temperature, moisture,

shrinkage, swelling or other dimensional changes in structural members

of the shoring system should be considered when applicable. In general

It can be assumed that the empirically-based lateral loads that can becalculated in accordance with these guidelines contain a reasonable

allowance for temperature effects on struts.

5. Design Criteria

5.1 Sloped Excavations _

5.1.1 Design Limit States ;

1. Slope stability failure (part or all of the eiobankment)

2. Sloughing

5.1.2 Design Criteria

5. 1.2.1 Long-term Excavations

Granular soils (no cohesion)

U)

Dynamic loads ^awaed-by pl.le driving, blasting, traffic and construction

slope angle should not exceed angle of Internal friction.

D-9
9 Cohesive Soils

The safety margin against stability failure should be greater

Suitable surface and subsurface drainage should be provided to prevent

stability failures or slou^ing induced by seepage or erosion.

For deep excavations

6 ft vide benches should be provided at vertical Intervals not

exceeding 30 ft.

Maximum unbraced height of vertical bank:

5 ft for all soils or fractured rock. No limitation for sound

5. 1.2. 2 Short-term Excavations

The safety margin against stability failure should exceed 1.5 except

that for dry cohesionless soils a slope angle equal to the angle of

repose may be maintained. Short term strength properties could be

utilized, provided that there. are adequate safeguards against conditions

which could-cause- strength degradation..

Maximum unbraced vertical bank: For intact hard clays the unbraced

_

height could exceed 5 ft provided that there is substantial empirical

evidence that the risk is not excessive. For all other soils, including

fractured rock, the mAYlimnii unbraced beicht should not exceed 5 ft.

5.2 Braced Excavations

5.2.1 Design Limit States

(1) Stability failure of the bank

(2) Base Instability

(3) Partial caving or sloughing of the bank between spaced vertical

or horizontal supports.

D-10
/\ >>

5. 2. 2. 3 Soil Stability Between Spaced Supports

There is no generally accepted theoretical approach by which the

ability o£ a soil to arch between- swcccesi^e supports can be evaluated or correlated with strength properties of the soil. There is empirical

evidence that short-term supports can be spaced up to 8 ft on center In

hard clay, very stiff sandy clays or glacial tills and 4 to 6 ft on

center in slightly fissured stiff clays. Guidance can be derived on a

regional basis from empirical evidence.

5. 2. 2. A Soil Support for Struts , Anchors or Soldier Piles

A minimum safety margin of ^ts recommended against bearing failures

of members of the shoring systen^ such as raker braces.

-50//

A safety margin of not less than 1,5. should be used when passive earth

A

pressure is relied upon to support embedded portions of soldier piles and

sheeting or deadmen.

All soil anchors should be proof load tested to 1.33 times their

working load... If the load capacityof soil anchors- is determined by

tests, it should be not less than 1,5 times the working load -for anchor I

inclinations of 1 vertical in 2 horizontals, or less', and increase to 2,0

times their working load for Inclinations of 1 horizontal in' 2 verticals

i

When anchor capacity is determined by analysis the margin of safety

should not he less than 3. Soil anchors subjected to the working load

should not show measurable creep when the load is sustained for 15

minutes.

5. 2.2.5 Design of Structural Components of the Shoring System

5. 2. 2. 5.1 Applicable Standards

Structural members should he designed in accordance with the following

standards:

D-11
References

The following references provide guidance which is considered adequate.

Lateral loads calculated in accordance with these references are considered

to be working loads.

(1) Feck, R. B., "Deep Excavations and Tunneling in Soft Ground," Stateof-the-Art Report, Proceedings 7th International Conference on Soil

Mechanic's and Foundation Engineering, State-of-the-Art Volume,

pp. 225-250, Mexico, City (1969).

(2) Peck, R, B. , Hanson, W, E. , Thumbum, T. H. , Foundation Engineering , Chapter 27, John Wiley and Sons, New York, N. Y., Jan, 197A.

(3) Goldberg, D. T. , Jaworski, V. E. , and Gordon, H. D., Lateral Support

Systems and Underpinning, Report No. FHWA-RD-75-129 , Vol. II, Federal

Highway Administration, Office of Research and Development,

Washington, D.C. April, 1976.

(A) Department of the Navy, "Soil Mechanics, Foundations and Earth Structures,

NAVTAC-DM-7, Chapter 10, U.S. Naval Publications and Forms Center,

Philadelphia, Pa., September 1971.

(5) United States Steel Company, "Steel Sheet Piling Design Manual,"

U.S. Steel, Pittsburgh, PA., July, 1975.

(C) -Joe Lh, Safuo'^ ^

The preceding references contain design approaches which are not

necessarily identical. However, all these approaches are widely used and

are considered to be adequately conservative.

A. 3 Summary of Information

Hereafter is a brief summary of Information derived from the references

listed in A.2. The suggested pressure envelopes are not intended as an

D-12
OHia noNTRROTORS

i:dd^}cidtwrL

THE NEIL HOUSE MOTOR HOTEL

September 14, 1978

COLUMBUS. OHIO 43215 • 228-6831

LONG DISTANCE TELEPHONE 800.282-1388

Mr. J.O. Bryson, Chief of

Construction Safety Program

National Bureau of Standards

Washington, D.C. 20234

Dear Mr. Bryson:

' Due to conflicting commitments, I will be unable to attend your Trenching

and Excavation Workshop on September 19th. However, I would offer some comments addressing your summary of recommended acceptable practice.

1. The main thrust of the recommendations seems to be the use of a licensed engineer to design shoring systems and determine adequate slope angles. In theory, or when confronted with unusual

conditions, this approach can be the best course. However, in

the everyday wrold of the contractor there are not enough available engineers with the expertise to design such systems for all

of the anticipated work nor in the majority of cases is there a need for this approach. As has been recognized in the report,

the rapid progress of the work, the known conditions and soil types makes the engineering approach additionally impractical.

If an engineered shoring system were to become a requirement the

annual installation of laterals to the nearly two million private

dwellings would be economically impractical.

A major problem confronting the contractor is the lack of recognition of consulting engineering firms for the need of protecting

personnel during the installation of underground utilities. This

problem is evident in restrictive right-of-way locations and the

lack of provisions for payment of the additional materials needed.

2. Soil classifications and various shoring methods are the areas we experience the most problems of interpretation by OSHA inspectors.

More technical data is needed on hydraulic shores and their limitations.

3. My investigations of cave-in accidents have revealed the cause of

this type of accident was the complete lack of any protective measures, not failure of materials or devices used for protection.

JSSM

D-13

®
- 2 -

4. Recognizing the many fatalities resulting from trenching operations demand standards of performance to minimize exposure we

hope all factors will be considered before finalizing a regulation.

5. I urge that concensus recommendations be developed which will be

the minimum allowable performance standards.

Sincerely,

Leonard Freed

Manager of Safety

LF:jj

D-14
AMERICAN LUMBER STANDARDS COMMITTEE

J. L. KELLY, Chairman

J. RAJALA, Vi«e Ctiairman

G. H. BOWERS. JR., Vrsasurar

T. D. SEARLE&, Secretary-Manager

SUITE 204 20010 CENTURY BOULEVARD

GERMANTOWN, MARYLAND 20767 TELEPHONE: 801-972-1700

September 22, 1978

Mr. James O. Eryson, Chief

Construction Safety Program

National Bureau of Standards

Washington, D.C. 20234

Dear Mr. Bryson:

Thank you for the opportunity to comment on the proposed OSHA

Regulations for Excavation, Trenching, and Shoring. Our comments

will be limited to those proposals concerning lumber.

The American Lumber Standards Committee (ALSC) is appointed by the

Secretary of Commerce. It is composed of manufacturing , distribution,

and consumer-user representatives. Its purpose is to establish and

maintain the lumber standards for the United States. Canada and Japan

have adopted our standards . Grading rules conforming to the American

Softwood Lumber Standard are used for virtually all softwood lumber

produced in the United States and Canada. Those rules contain standard

grades that are recognized by manufacturers , distributors , consumers,

and purchasers of lumber throughout the United States. This standards

effort was started in the early 1920' s and is recognized throughout the

world as a system that has accomplished a wide degree of lumber standardization. These standards are adopted by reference in purchase

specifications and other requirements of FHA, DSA, GSA, and all major

building codes.

We are opposed to development of additional standards or grades which

are unnecessary and will cause confusion and possible misrepresentation

in the market place. The NBS has recommended that allowable stresses be

based on No. 2 as a minimum grade. However, the NBS analysis indicates

only 80% of the pieces are No. 2 grade or higher and that these percentages do not reflect pieces that have wane and decay. The American Softwood Lumber Standard requires all grades (No. 2 in this case) to be 95% on grade to be in conformance and excludes lumber that has excess wane and decay. For NBS to set such arbitrary quality limits could be con- strued as permitting only 80% of the pieces to be on grade which could

undermine the present standard and lead to competition to see who could

furnish the lowest quality. Further comment on the NBS reports indicates

D-15
Mr. James 0. Bryson

September 22, 2978

Page 2

quality control is necessary and can be implemented in two steps:

(1) A specification; and (2) A grading system. It is our recommendation that the standard grading rules in existence be used by reference

.

If this is done, the quality control becomes a part of the system in

that any purchaser has reasonable assurance that pieces containing an ALS-approved stamp are within the specification.

When standards are written, differences will occur in the interpretation

and application. Therefore , a system is needed to assure that the

standard is interpreted and applied uniformly . A major strength of the

ALS system is that it provides this assurance thru a program of actual

field inspections to see that the specifications are being applied

uniformly.

The importance of having equal specifications in the market is illustrated

in Paragraph 3.2. (c) Wane. . .where it is noted that 42% of the hardwood

wales were reduced an average of two grades and 8% of the softwood wales

were reduced an average of one grade. Wane did not appear to be a problem for softwood values. Whatever specification is finally adopted, if

indeed such a specification is necessary , must require equal quality

levels. Under the American Lumber Standard system, stress levels are assigned to all grades including No. 3 in softwood dimension lumber. Stress

levels are also assigned to Post & Timbers and Beams & Stringer sizes.

Use of the present system would be a simplification of the proposal

and would do away with the necessity of having another method of

assigning and applying both grades and stress levels.

The slope of grain under Paragraph 3.2. (g) indicates 95% of the hardwood

values had a slope of grain of 1:20 or less. Since slope of grain is an important indicator of strength and the steeper the slope the weaker

the piece, it would be imperative to know the slope of grain in individual pieces; i.e.

,

1 in 6, 1 in 8, or 1 in 10, before any conclusion

could be made regarding assignment of values. This is an example of

how interpretations are needed and play an important part in a standard

.

Slope of grain of 1:20 or less means that 95% of the piece had a slope

of grain of less than 1:20 and thus would not be inti tied to the values

for straight grained lumber. It appears a different meaning was intended

.

In summary, we recommend that any system devised incorporate by reference

the national standards, grades, and quality control now in existence and

that no additional standards , grades, or quality control programs for

softwood be included in the NBS recommendation to be forwarded to OSHA.

D-16
Mr. James O. Bryson

September 22, 1978

Page 3

Hardwood could be graded to existing specification; i.e., No. 2 grade,

and strength properties could be assigned based on the same methodology

already approved by NBS and the Forest Products Laboratory . The National

Hardwood Association, 332 S. Michigan Avenue, Chicago, 111. 60604

should be requested to furnish the necessary information.

Thank you for permitting us to comment on the NBS proposal. If ive can furnish you with any additional information, please advise. We will

appreciate your keeping us informed of further developments.

Sincerely

,

Thomas D. Searles

Secretary-Manager

TDS/SKW

cc: R. Hewitt, NFPA

Administrative & Finance Subcommittee

D-17
United States Department of Agriculture

FOREST SERVICE

Forest Products Laboratory, P.O. Box 5130

Madison, Wisconsin 53705

4040 (NBS)

October 11, 1978

Dr. Felix Yokel, Chief

Geotechnical Engineering Program

National Bureau of Standards

U.S. Department of Commerce

Washington, DC 20234

Dear Dr. Yokel:

I would like to pass on to you both reflections on the workshop

and further specific comments on the text as prepared for the

workshop

.

You are to be commended on the workshop. It was well formulated

and carried out in a professional way. I was pleased to be able

to participate and felt that I learned a great deal as a participant.

I tend to agree with the comments of the AGC and others—that

regional reviews are desirable. And I disagree with Mr. Tom Seymour

on timing. Of course, I appreciate there are monetary concerns. Nevertheless, if there is justification for any workshop before

completion of the technical documents, there is justification

for more balance than was present in D.C. We may have met our mutual administrative need as specified in our contract relationships, but I feel that if NBS needed this feedback we have to

recognize it has a heavy geographic bias. We (the technical input)

will have to be extremely careful in our response to this workshop

in recognition of these limitations.

I would also like to address, for the record, our notion of

certification. I'm not sure professional engineering requirements

are as untenable as some proposed. For example, no code people

were present to represent views which can be expected to go beyond

worker safety, of course, but also may have to be anticipated as a potential jurisdictional conflict. However, if a PE cannot be

required and if no contract or licensing procedures are available,

the alternative we discussed is to conduct certification workshops

in each State using the facilities of land grant engineering

extension and the cooperation of AGC, etc.

D-ib 6200-11 (1/69)
Dr. Felix Yokel 2

I do have one constructively critical comment concerning the

preoentations on soil and timber made by you and Dr. Tucker.

Basically* as engineers we can be firstly positive in our observations on successful traditional practice and secondarily

correctly negative about our inability to put the analytical

tools together to explain present practice. Note I did not say

to justify present practice.

In particular we need tc be careful about statements that imply soil or wood (both natural materials) do "not check out." The materials

don't "not check out." Our engineering data and capabilites

don't measure up ^o the task. This is a decidedly different statement. For example, I am absolutely convinced that if we had the

correct soil data, more wood variability information, and the correct

analytical models for composite structural performance, we could

explain the past performance of soil and timber in trenches. As

you and I discussed in 1973 or 1974, as a matter of fact,

deterministic design methods are almost totally incapable of

addressing this problem.

All the above was in your messages and those of Dr. Tucker,

but the emphasis appeared to be reverse in some cases. I'm convinced

that many in the audience didn't fully understand the serious nuances

of the comments that you made. I don't like to see too much emphasis

on ignorance to the wrong audience; your engineering guidelines are perhaps the correct place to be explicit on these matters.

Another matter that came up, but which was foggy because of the

somewhat adversary positions taken, was the need for alternative

routes for product acceptance. I believe this is essential,

particularly when proprietary products would be involved. These

products also may "not check out" because of inadequate data. A

very difficult subject is whether empirical methods of acceptance

can be used, perhaps based on tradition and on comparison with

other traditional systems. I have no good suggestions to make in

this regard except to echo the comment made at the workshop—that

perhaps provision needs to be made for something like the research

card approvals of ICBO.

I have a few specific comments on the text handed out, in addition

to those in my letter of September 14:

1. In section 1, 3(a), rating , the 3rd paragraph states that the

"rating shall be valid for the period of time stipulated by the

licensed engineer of for 1 year , whichever iis less ..." (underline

is mine). This statement will be at variance with our use recommendations of a maximum of 9 months of effective use for a site
Dr. Felix Yokel 3

index greater than 65. This is because of the intense decay

hazard in these areas. The easiest way to side step this dilemma

would be to change 1 year to 9 months. Maybe there are other

ways.

2. There seem to be discrepancies between tables la and 1

because la includes 4 by 4's, while the smallest size in table 1

is 4 by 6. Is there a column missing in table 1?

3. I suggest the Use Recommendations for Timber be made a specific part of the engineering guidelines (perhaps a section

5. 2. 2.5.3) by reference at least, so that the attention of the

engineer is drawn to the recommendations. Nowhere in the

documents as presented is there any recognition of the specific

concerns for storage, useful life, etc.

4. The wane limitations in section 3 are based on performance

criteria far more severe than those placed on strength ratios.

There are two concerns here: (a) Liberalization would more correctly

represent what the survey identified as current successful practice,

(b) At a minimum, we suggested adopting the SPIB wane for No. 2 SR

but it should be recognized that these limitations are not based on structural assessment of a cross section loss. The question boils

down to the fact that it would be easier to accept the southern pine

wane limitations for all of the grades and sizes (i.e.. No. 2 for

dimension sizes and No. 2 SR for the larger sizes) , but this still

might be restrictive on hardwoods. Is there any point in trying to

liberalize for hardwoods?

5. In the engineering guidelines for load capacity , there is a potentially serious, hazardous definition. The factor 1.65 applies

only to very large sample sizes, implying the samples are a very

accurate representation of the true population. Since no minimum

sample size is specified, we court disaster if an engineer decides

to test only a few specimens, assumes normality, and uses 1.65. As

noted in my earlier correspondence, the NBS monograph by Natrella

offers a better alternative of a factor that is sample size dependent, and it also requires the engineer to face the issue of the

confidence he must have in the result. Many engineers are not

acquainted with this issue. This is the place to draw the line and

give the engineer the Natrella reference, instead of 1.65. The

basic definition remains the same, but the factor is defensible.

Secondly, some materials will be found to have definitely skewed

distributions rather than normal. This can result in either highly

D-20
Dr. Felix Yokel 4

coaservative or highly liberal results. I suggest that this section

have a sentence warning that the engineer be alert to high degrees

of skewness and to seek help in analysis if such is found.

6. I addressed the strength ratio problem very briefly in my letter

of September 14. I believe that Dr. Knab and I should work out thp

appropriate ways of handling strength ratio in subsequent versions

of the document as well as in his analyses. We have had some tentative discussions already. The issue here merely is that the

commercial grade that we used as a reference point actually contains

a range of effective strength ratios because of the need to permit a variety of member sizes in the same category. I believe these are technical concerns that Dr. Knab and I can resolve.

Again, let me congratulate you on the way in which the workshop was

handled, and I hope something can be resolved for additional input

from other geographic sectors of the United States.

Sincerely,

WILLIAM L. GALLIGAN, Project Leader

Engineering Properties of Wood

cc: J. Bryson

L. Knab

A. Bendtsen

D-21
SI>IEIsl}

CORPORATION

Manufacturers of the Finest in Aluminum Hydraulic Shoring Systems

P. 0. BOX 12591 October 12, 1978 Houston, texas 77017

9040 SCRANTON STREET

HOUSTON. TEXAS 77075

PHONE: (713) 943-0750 JACK MANNING TWX: 910-881-5015

S«cr«Ury

DAVID 0. PLANK

PrMWant

ROBERT C. KELTIE

V'tca Presid«nt

Dr. Felix Yokel

National Bureau of Standards

Room B 168, Building 226

Washington, D.C. 20234

Dear Felix; 5 The seminar on shoring method and that cross section of persons *! was very interesting. |j In your closing statements you requested that each of us address

a letter to you outlining ciny ideas, suggestions or otherwise that we

may have.

My general comments are as follows:

1. I felt that the final recommendations on timber shoring ] were unsatisfactory. Admittedly, the structural strength ) of these pieces can vary with the individual unit and can-

| not be depended upon consistently. As consistency and ! safety go hand in hand, then timber specifications can ^ clearly not be used in a safety standard unless a design ^ overkill sufficient to eliminate chance, be instituted.

j Undoubtedly, this would change the specifications as now

published to a significant degree.

I 2. I was frankly amazed that no discussion or study was made ' as to the effect of pre loading the trench wall. While I

j heard some mild discussion in general assembly, (I was not ij in the specific method workshop) the whole subject seemed

generally ignored. I would like to see a recognized study | made of preloading effect, with the results published for j the general industry.

All in all I thought it an excellent meeting and most effective

in every way. If I can ever be of assistance in this or any other such

work please do not hesitate to let me know. As former operations manager

of Equipment Guidebook Company, a firm that publishes several explanatory

manuals on OSHA regulations, etc., I have had considerable experience

along this line.

regards

,

iddl^on
NATIONAL UTILITY CONTRACTORS ASSOCIATION

815 Fifteenth Street, N.W. • Washington, D.C. 20005 • Phone/Area Code 202 737-0037

1

Pfisidfnt

Prttidint-Elect Trusurer

StcrtUry

Kenneth Goodwtn

David Shevock

Leonard Genghmi

Loretta Simmons

Vici Presidents

I Region One Johi; P.iceJia Region T\^o Anthony Mdigues

Region Three Daniel Carapeiiocci Region Four Richard Bernsee Region Five Paul Carson

Region Six David Bndeweii Region Seven Frank Patterson Regon Eight John Felton Region Nine Jack Fure> Region Ten Gorman Pinkston

October 16, 1978

Executive Director John Pannullo

William Lee

Peter Inzero

Antonio Marinelii Peter Ellis Joseph D'Annunzio

Harold Schneider

Harry Peyton Anthony Shuttle

Jene Amadori Owen Anderson

Ernest Barrett Mike Blankenship Gordon Booz

Joseph Bongiovanni

Francis Carpenter Richard Collings Leonard Detnck John DiGtulio Angelo Feraco

Alabama

John David Baird C J McCormick Wayne Miicheh

Arizona Robert Bentley Ben June

Marvin Polio

California S M Roberson Tony Sands Tony Santos

Connecticut

Williarr- Brennan

Richard Furano Unwood Mather Delaware

Richard Appleby Joseph Corrado Eugene Julian

District of Columbia

Call Miiiei Steve O'Reilly George Taylor

f^fonoa. South John Chaney

Robert Hall Kenneth Jackson

ffortOa. Suncoast Mike Gayior Oavid Hall Renee Aon Wnghi

Georgia W B Cooper Tonimy GriMm John D Stephens

Illinois. Chicago

Paul Carson

Carlo SantuCCi

Illinois. Springfield Jack Sheiato Dean Stemhiiber Les Siorrer Indiana John Baas Joseph Hanifey Paul Sweeney

Louisiana C 0 Calongne

T orTi Heard

Louis Seiig Maryland Edward Harding Ray Hoover

Robert McCoiion. Massachusetts Leon AsaOoonan

Frank Federico Jack Ffin Wilhan- lopoo

Michigan John fartikeo a Dave Harper Dave Kiooie Minnesota

Larry Gordon

Stan Hemphill Tom Montgomery

Pitt Prtsidints Edward CruzJack Leach

Frederick Compagm

Oirectors-Ai-Large Wilhani Flynn D A Fosiei David Hall George Hall Ray Hoover Joseph Julian Frank Leone

JeMrev Lowe

Saniuel Luciano Andrew Mayts James Nonhrup

Sherman Olm W , R Owens

Frank Renda

George Sniaites Joseph Siruzziery. Sr Ed Tschigglrie

Larry Weatherholtz

Chapter Rapresentatives rvew Jersey Clyde Fear Roger Hansen

Robert Johnston

Michael Zicheiii New York. Central Thonias Lee

Michael Palenscar Duane Olir' New York. Eastern John OiGiul'O James Fraser Robert Lashwav New York. Niagara Chip Kub'oiec Dennis McCartney

Donald Siocxrr.an New York. Rochester

Paul Carim

Foster O'Fiore Michael Nicosia New York. So her A J Cerasaro Anthony Pasquale Anthony Sienio Ohio

Witliaai Burgeti

Victor OiGeronin.o John Jurgensen

Pennsylvania. Eastern A Ross Myers

George T npp

HarolO Tripp Pennsylvania. V^estern Joseph Biviano Eoianuei Pans John Kotch Rhode Island Joseph Briio. Sf Herimri CapaiOi

Afiyelu PdOlirio

Virginia. Northern

Robert Griltiih

Wiliiari Hofikt;

Jofir^ Pulosk'

Virginia. Richniond

Fred Bdf'ies

Alviri Collins Stanne Lyttle

Virginia, hdewater

Eniil Viola Lewl^ Will

Jelly Won.HI.

k

\Nashmgion

Hull Allrl Joiiri Dukf

hii K tgqe

kVeS/ Virginia Frank Hill Rict..irr| j,ickst;ii

f> w<- Iciyioi

V\nsc(jrisin. Madison

Del bornkarnp Caleb Cfiapel Hichard bngeliiart \Nisconsin. Milwaukee

Nornian bemsieiri Kennel ti Peterson Robert SUiraulnayjei

Ganaral Counsel Joseph Sio'ii

Dr. Felix Yokel

National Bureau of Standards

Bldg. 226, Room B-168

Washington, D. C. 20034

Dear Dr. Yokel:

Following the NBS workshops, we summarized several of the topics

discussed and solicited comments from our membership.

On that basis, the National Utility Contractors Association

would like to endorse the following changes in the OSHA standards

:

1) The standards should not require that the services of a registered professional engineer be obtained on trenches

conforming to certain physical criteria. The standards should

stipulate that specific standards be met but also permit the

option of obtaining engineering services if the contractor

so desires regardless of the configxiration.

2) Compound trenching should be permitted by the standards.

The primary trench (that portion with vertical walls) can be

no deeper than three feet before trench shoring must begin.

Case II as proposed should be considered adequate.

3) The standards for trenching and excavating should be kept

entirely separate.

4) A simple soil classification system which would distinguish

AT LEAST four different soil categories would be an asset to

a trenching contractor.

5) Trench boxes should not be required to ride on the bottom of

the trench. Ease of laying pipe is increased with adequate

safety provided if the trench box rides about two feet up

from the bottom of the trench.

6) If a trench has compound sloping with shoring being provided

in the primary trench, the shoring members are to extend a reasonable height above the vertical walls such that soil

material cannot roll or slide back into the trench.

7) Shoring in a shored trench should not be required to extend

to the bottom of the trench. The shoring should be kept within

two feet of the trench bottom.

8) Shoring should be encouraged to be included in contract

D-2'3

I
i Dr. Felix Yokel 2 October 16, 1978

documents as a bid item.

9) A means of exit should be provided in all trenches. This should not

necessarily be required to be a ladder. A sloped bank is often

quite adequate as a means of entremce and exit in a trench.

We do not agree than an engineering analysis should be required for

trench boxes. We feel that this recjuirement would impose undue

hardship on our members since many contractors build their own boxes.

We feel that there is no evidence that suggests that trenchboxes are not sound.

We would like to thank you for allowing us to participate in this

process cind hope our input will be of some value.

Ki nr‘PT-^1 v

.

Robert G. Griffith

Chairm2m,NUCA Safety Committee

cc ; Goodwin , Shevock

D-24
I ASSOCIATED CONTRACTORS

OF NEW MEXICO

P. O. BOX 1988 PHONE /505/ 982 2639

SANTA F£, NEW MEXICO 87501

JAMES E. HOLLIS, Managar

October 18, 1978

National Bureau of Standards

Room B 168, Building 226

Washington, D.C. 20234

Attention: Felix Y. Yokel

Dea r Mr. Yokel : Regarding the revision of Subpart P, of the 1926

Construction Standards, the Associated Contractors of New

Mexico wish to make the following comments:

1. The requirement of a designing engineer as proposed is unfair and impractical.

a. It does not provide the option of

recommended slopes based on soil

classification deeper than 20 feet or

left open for more than 48 hours.

b. It neglects consideration of the small

contractor who may not intend to leave

a trench open for 48 hours, but due to

circumstances beyond his control may

have to.

c. It does not consider such items as subdivisions where a 5 foot manhole is

allowed to remain open. Surely NBS and

OSHA would not intend to have an engineer

design 20 cuts for manholes in a 5,000

foot sewer system.

2. It does not define sound unfractured bedrock.

As stated, all trenches in rock would require

shoring or be slopped to be in compliance.

D-25
I ASSOCIATED CONTRACTORS OF NEW MEXICO

3. The language is not clear in reference to

trench boxes used at the bottom of slopped

excavations

.

We believe that one meeting in Washington is not

adequate to get public response to revisions of a very major

item in the standards. More meetings in other areas of the

country would seem mandatory to get the maximum input to the

final decisions. We urge you to consider these requests.

cc: A. L. Schmuhl, Director

Safety and Health Division

The Associated General

Contractors of America

APWA-Utility Committee

Safety Committee

Joe Kinnikin

Director of Safety, ACNM
BIG RED SAFETY & PRODUCTION, INC.

8025 Enterprise Drive

Newark, California 94560

(415) 796-3333

Main Office

(408) 269-1226

Decerober 1, 1978

Felix Y. Yokel

Chief, Geotechnical Engineering Progra]:i National Bureau of Standards

Washington, 0. C. 2C234

Dear Felix

x

Thank you very much for taking the time from your busy Holiday schedule to meet with us last Wednesday, the 22nd.

rtopo your Thanksgiving Day was as enjoyable as ours. Jean

and I are looking forward to your visit out here. We will send

you i*ull information on the Cal-Poly seminar as soon as it is

set.

To make good suggestions on your summary, I sent the comments

and recommendations thathUCA people sent to me, to the Under- ground Contractors Association members here in Northern California, with comments of mine for consideration. Since I have re- turned, I have a few that have been sent back to me. In general, they all OK what NUCA presented.

Enclosed are these 11 points and my comments, along with 6 points of my own.

I will be getting into your summary deeper for additional com- ments and will send them to you as I do.

I can see now that it is going to be most important that we hold a meeting on this here on the West Coast. Perhaps this

can be done in April v/hen NUCA is having its West Coast Conference in San Francisco. The dates are April 25 through 29, 1979 . I am trying to set the seminar at Cal-Poly for April 19 and

20, 1979 * This would be a good time for another summary meeting here in the Bay Area,—say April 23-24 . I can pull AGC and others involved into it.

I will be in touch with Dr. WAll at Cal-Poly this week and get more information tied down.

Thanks again.

W.M. "Red" Cass PE

WMC/nlb

En^inmmrmd Syafma for Trortehoa TREN^SHORE Rottfela • Cortaulfirtg • Educoflon • Sorvico and Saloa REDDIE‘SHORES

L-27
COMMENTS & RECOMMENDATIONS

I

1.

(NUCA) OSHA stanHards should require that trench boxes have an engineering analysis to show that

adequate protection is provided for workers in the trench. Each box should be permanently marked as to the

lateral earth pressures which can be supported. The marking should indicate the source certifying the trench

box strength. The fabricator should be responsible for the certification.

OK (Red’s Comments) Certification by a Registered Engineer.

2. [NUCA] Contractors should be required to document their safety training efforts such as safety meetings,

first-aid courses and emergency drills.

3. [NUCA] The standards should not require that the services of a registered professional engineer be obtained on trenches conforming to certain physical criteria. The standards should stipulate that specific standards be

met but also permit the option of obtaining engineering services if the contractor so desires regardless of the

configuration.

4. Compound trenching should be permitted by the standards. The primary trench (that portion with vertical

walls) can be no deeper than three feet before trench shoring must begin. Case II as proposed should be

considered adequate.

OK (Red’s Comments] We are, at present, working with three and one-half feet vertical

then sloping. This has been well engineered for AGC contractors here in the state.

5. The standards for trenching and excavation should be kept entirely separate.

6.

A simple soil classification system which would distinguish four different soil categories would be an asset to

a trenching contractor.

(Red’s Comments] For the past 10 years, we have been having field training personnel

here in Northern California use a Trench Wall Standing Time, rather than using highly

qualified soil categories. This has worked very well and has begun to get the attention

of Civil Engineers, both in the field and in universities.

7. Trench boxes should not be required to ride on the bottom of the trench. Ease of laying pipe is increased with

adequate safety provided if the trench box rides about two feet up from the bottom of the trench.

8. If a trench has compound sloping with shoring being provided in the primary trench, the shoring members are to extend above the vertical walls such that soil material cannot roll or slide back into the trench. This extension should be about 18 inches.

9.

Shoring in a shored trench should not be required to extend to the bottom of the trench. The shoring should

be kept within two feet of the trench bottom.

^ (Red’s Comments] Two feet from the bottom of the trench has been in our code

C/l\ LJ f I tor several years.

10. Shoring should be encouraged to be included in contract documents as a bid item.

OK O

(Red’s Comments] This has ecn law here in California since 1973 (AB150 Paragraph

6707). It has become over 90% effective. However, wc do believe that all bids, where

trenches arc five feet or more in depth, have the bid item for shoring. Not just government agencies.

D-28
Recommendation & Comments

Page 2

11. A means of exit should be provided in all trenches. This should not necessarily be required to be a ladder.

A sloped bank is often quite adequate as a means of entrance and exit in a trench.

OK

OK

OK

OK

OK

OK

(Red’s Comments in addition to the above] OSHA, on a national level, should set up

Bade Shoring Safety Training Schools, such as those I have developed for the American

Society of Safety Engineers of Sacramento, California. The school and bid item are a must for this modern age. The service of a registered Civil Engineer

should only be required when shoring system is other than shown on the codes.

We would like to sec that there be no

open trench overnight, weekends or holidays. In those areas where it is necessary to

leave the trench or excavation open, the area should be fenced eight feet or secured by

other means. We would like to see, when trench is being

dug on existing streets, that at least one block be completely closed to traffic except

emergency & mail. Our survey shows this would allow completion of projects 25%

quicker.

. We feel that all OSHA personnel should

be better trained for observing trench operations. The untrained person has caused

problems and hardships for the contractor in the past.

We should have a Safety Committee of

not more than 10 people from across the U. S. to carefully go over all considerations.

YOUR COMMENTS:

1

2 .

3.

4.

5.

6 .

7.

8 .

9.

10

11

D-29
SOIL TESTING SERVICES

1 1 1 PFINGSTEN ROAD NORTHBROOK, ILLINOIS 60062

January 2, 1979 phone Chicago 31 2-273-5440 Northbrook 31 2-272-6520

Mr. Felix Yokel

National Bureau of Standards

Center for Building Technology

Structures Section

Building 226, Room B-168

Washington, D. C. 20234

Dear Felix:

Several months ago, I received a copy of the "Summary of Findings and

Recommendations to be discussed at the Federal Workshop on Excavation

and Safety" document, prepared by the National Bureau of Standards.

Unfortunately, I was unable to attend the September 19 workshop and

apologize.

At the level at which these findings and recommendations are presented,

I have a number of comments that I will make subsequently in this letter.

These comments will deal with the Section 1 on Technical Provisions,

Section 2 on the Soil Classification System, Section 3 on Allowable

Stresses in Timber Shoring, and Section 4 on the Summary of the Field

Survey.

However, I would like to comment first on the entire question of job

safety and methods of improving job safety.

LEVELS OF RISK ACCEPTABLE TO SOCIETY IN U.S.A .

On the broadest possible level concerned with worker safety in the

construction industry, construction is a risky business and all risks

cannot be eliminated. In this regard, I might point out that in 31

years of professional practice, we have had no deaths due to our field

operations involving soil exploration, or caisson inspection, or any

other job related activities. However, we have had approximately a dozen employees die in 31 years, all due to automobile accidents in

personal vehicles not on company time.

Johr P QnMdmgAr, P E

C>y<l« N B«k*r, Jr . P E

Robert 0 Lukas. P E

Sefdar A 0«. Ph D . P E OougtssE KMts

Kannetb H Kastman. P E

CMICAQO. PEORIA. ROCKFORD. ILLINOIS • LAFAYETTE. INDIANA • WASHINGTON. D.C. CEDAR RAPIOrOAVENPORT. OES MOINES. IOWA • KANSAS CITY. WICHITA. KANSAS - LANSING. MARQUETTE. MICHIGAN - MINNEAPOLIS. VIRGINIA. MINNESOTA • RALEIGH. NORTH CAROLINA • BISMARCK. NORTH DAKOTA

FAIRFAX VIRGINIA • GREEN BAY. MILWAUKEE. OSHKOSH. SUPERIOR, WAUSAU.

WISCONMN • KARACHI. PAKISTAN • MADRID. SPAIN • JEDDAH. SAUDI ARABIA

Engineering Analysis/Reports

Construction Quality Control Foundation Borings and Testing Environmental Testing and

Evaluation
Mr. Felix Yokel

January 2, 1979

Page 2 -

I realize that the much greater risks involving automobile travel should

not in a sense have any influence on deliberations of job safety,

particularly job safety involving trench excavations, but this is

mentioned only because society does accept a certain level of risk

involving travel and there must be a comparable attitude toward excavation safety, particularly since EPA requi res every community to have a safe water supply and sewage treatment systems, installation of which

'requiros trenching.

THirX PARTY INVOLVEMENT

If tho risks involving excavations were to uninvolved third parties,

such as is the case with many automobile accidents, then perhaps society

should have a greater concern. However, the risks are in fact almost

always to the persons involved in the construction itself. In a majority

of the cases that I have been aware of, the injured workman was himself

at least partially and frequently solely responsible for his injury or death.

In spite of the negligence of the workers who are injured, the

system is so designed that it is the employers who in fact are held

responsible, whether they should have been or not, and are held financially

accountable, funded through insurance premiums. Designers, owners and

other contractors frequently are the victims of contingency fee lawyers'

lawsuits that are filed on a shot gun basis, and therefore include many

firms involved with a project which had nothing to do with the accident.

To try to improve job safety involving excavations without dealing with

the need to enforce the laws of barratry and maintenance against contingency

fee lawyers and shot gun suits, is not likely to be productive.

NO FAULT WORKMEN'S COMPENSATION

Workmen's compensation insurance was created more than 40 years ago, I believe, as a no fault concept to reimburse workers for the medical

care, lost income, and other costs involved with job injuries and death.

Certainly some states have miniscule compensation rates that need revision,

but it seems to me that on the establishment of adequate compensation

rates for injuries, that legislation should be passed in each state that

will in fact make workmen's compensation the sole remedy for job injury.

Since it has been estimated that as much as 83% of the cost of workmen's

compensation insurance goes to legal fees for the plaintiffs and the

multitude of defendants, and insurance administration, a no-fault concept

would substantially reduce workmen's compensation insurance rates, at

the same time permitting a greater portion of the present insurance

premiums to be used to increase compensation to the injured workman.

D-31
Mr. Felix Yokel

Janua'ry 2, 1979

Page 3

-

CONSTRAINTS AGAINST SAFETY

However, on a broader level, because every participant to the construction

process considers himself a sitting duck waiting for some contingency

fee lawyer to sue him for something that was not his responsibility, all

of the participants to the construction process are gun shy and are warned to stay away from matters involving job safety because that is

the responsibility of the general contractor on a project. It would be

highly desirable that all participants to a project, including the

geotechnical engineers, could in fact discuss matters of job safety

openly, without fear that the mere mention of job safety in a report

would give the contingency fee lawyer all he needed to win a decision

against the concerned party.

It is therefore my firm opinion that great improvements in job safety

could be accomplished through tort reform, workmen's compensation reform,

and cooperative job safety attitudes and procedures, to replace the

present adversarial system where most of the money goes to lawyers who

have no qualms whatsoever about citing a geotechnical engineer's comments

on job safety as evidence to bypass workmen's compensation remedies for

an accident.

For those states where workmen's compensation rates are inadequate,

supplemental accident insurance can be purchased, I understand from

knowledgeable people in the insurance industry. That would then permit,

on a project basis, raising the level of compensation to any injured

workman to a national standard. The standard should however vary from

place to place in the country because of differences in medical and

other costs.

IS GOVERNMENT REGULATION EFFECTIVE?

The entire concepi of OSHA should be subjected to scrutiny, as well as its attitudes and procedures.

I'm sure that you, I and the formulators of OSHA, all agree that job

safety is a very worthwhile goal, and that every effort should be made

to provide adequate compensation to injured workers. However, it is not

axiomatic that a government program is the best way to achieve job

safety. It is unquestionable that OSHA costs the taxpayers a lot of

money directly, and costs the consumers a lot of money through increased

cost of construction in order to comply with OSHA regulations. Nothing

is free and both the taxpayers and the consumers should be aware of the

cost increases resulting from OSHA regulations.

d-32
Mr. Felix Yokel

January 2, 1979

Page 4 •*

However, even worse, in spite of OSHA regulations being in effect for

eight years, it is my understanding that there have been just as many

construction job accidents with the regulations as there ever were without the regulations. I am sure you have better information than I do, but at least we know that there have not been substantial reductions

in accidents, judging by the continuous increase in workmen's compensation

rates, inflation notwithstanding.

On an attitudinal level, it seems to me that the basic premise of applying

negative sanctions to firms not complying with OSHA regulations is a win-1 ose attitude. What we need is a win-win attitude, showing everyone

that an improvement in job safety will also, besides being humanitarian

in its goals and results, results in lower costs and fewer delays.

To simply create safety regulations, and then fine contractors who

ignore the regulations, does not really bring any injured workman back

to his original condition, certainly not one killed in a construction

accident. It has long been known that punishment of any type, including

the death penalty, does not serve as an effective deterrent to crime.

By the same token, the threat of punishment to an employer does not

necessarily serve as an effective deterrent to accidents, largely

because the attitude among workers toward job safety is wrong.

The Department of Labor several years ago sponsored through the Laborers'

International Union, a job safety training program, support for which

was later dropped. This program v/as open to workers and contractors as well. However the number of people attending was a drop in the bucket.

Furthermore, the support for the program was dropped.

It is my opinion that a win-win approach to the problem would be to

create a required course in job safety, for all design and construction

engineers and architects as a part of their curriculum, all contractors

and subs, and for all workers as a condition of employment. I don't

think that millions of dollars necessarily has to be funded through the

unions to do this, but existing institutions dealing with civil engineering

and construction should offer the courses to undergraduates, to graduate

students and on a continuing education basis to workers, contractors and

subs.

Extension services of the schools should provide local training programs

on job safety as a condition prerequisite to working on a construction

project. Wallet cards showing completion of such courses should be on the person of every person working on a construction project.

It is not sufficient to require that apprenticeship programs incorporate

such safety training elements, because only 11% of the journeymen in the

construction industry actually went through apprenticeship. However,

the lessons learned in the safety training programs organized by Laborers'

Internation Union could well serve as a model for creating additional

programs.

D-33
Mr. Felix Yokel

January 2, 197^

Page 5

-

WORKER SELF-INTEREST

It is the worker in a trench or excavation who has the greatest opportunity to protect his own health and life. Where a worker does not wear

his hard hat or does not wear steel -toed shoes, or smokes in a tunnel or excavation where gas is always a risk, this should not result in negative

sanctions against his employer. Furthermore, other firms on the job who are not his employers should never be involved, whatever the demands of

the American Trial Lawyers Association. Is there no justice??

WIN-WIN JOB SAFETY COOPERATION

Providing that the tort reform and workmen's compensation reform previously mentioned are implemented, it is my personal feeling that geotechnical engineers, architects, structural engineers, and others involved

with the construction process should also have training in job safety.

The individual engineers should acquire certificates in job safety, as should the workers.

Assuming again that the above changes in tort procedures have been

implemented, then I think a new approach to job safety should be created

by requiring, at least on federal projects, that there be a safety team

in which every participant to the project must participate, though to

appropriate degrees. In other words, if a geotechnical engineer makes

soil borings and writes a report long before the construction starts,

and has no one on the job during construction, his involvement would be

minimal, while the general contractor would have a continuing involvement

and should in fact have one person designated as the job safety director.

For small jobs it would probably be the superintendent but on large jobs

it may be someone's special responsibility. However, instead of everyone

being fearful of reporting on unsafe conditions for fear of assuming

liability that is not his, this would result in a situation where everyone

would feel a concern for job safety and would not feel constrained to

suggest to the individual whose life was at risk, or to the safety

director, that certain things should be changed. However, to require

this responsibility of all parties to the process, without tort reform,

training processes, and workmen's compensation reform would compound the

problem.

CONCERN FOR SAFETY

With regard to the excavation standards, there is no question but that a geotechnical engineer can greatly improve job safety to the extent that

he is involved in the project, not only before construction, but during

construction. I am not at all comfortable with the efforts of design

professionals to limit their responsibility to permanent construction,

leaving temporary construction and bracing entirely up to the contractor

0-34
Mr. Felix Yokel

January 2, 1979

Page 6 -

Hoivever, I attribute this problem solely to the contingency fee lawyers

with their shot gun suits, not to the indifference of geotechnical

engineers or architects or structural engineers to the safety of the

workman .

LEARNING FROM EXPERIENCE

There would be a further benefit if workmen's compensation reform and

common employer concepts were adopted, in the way of permitting free and

open discussions of previous accidents and failures . Fear of litigation

prevents knowledgeable parties about construction accidents from permitting others to learn and benefit from knowledge of the causes of the

accident. Case histories and failures should be a common element,

perhaps even forming the structure of an information document that could

be circulated throughout the industry by OSHA or by an industry group.

The virtue of this system is that the information would be factual and

timely and everyone would recognize his own vested interests in avoiding

the problems that created the accident or injured the workman. Such

information cannot however be submitted now to the public eye because of

the fear of incrimination of the party or parties involved with the

accident.

OSHA EXCAVATION STANDARDS

With regard to the summary of findings and recommendations that you have

prepared, beyond the comments submitted to you by Jim Kleinfelder, I do

not have any additional serious criticisms.

I do know from direct knowledge involving three or four construction

accidents in recent months that the present standards are ambiguous.

Particularly with regard to the Soil Classification System, the new document is obviously a great improvement, though I do favor the matrix

classification system, rather than the simplified system.

RESEARCH

With regard to other techniques for improving construction safety, it is

my personal opinion that slurry methods could be used for installing

sewer, water, and other piping, to minimize the need for workers to

actually be in trenches. Such techniques need subsidy in terms of

developing them. To my knowledge, other then dozens of slurry walls and

slurry trenches constructed in this country in the past ten years, I am not aware of a pipeline or sewer being installed by a slurry method.

This I think bears research effort subsidized perhaps by OSHA.

D-35
Mr. Fel.ix Yokel

January 2, 1979

Page 7 -

In the discussions of job safety, little is said about the tremendous

pressures on contractors to cut every corner because of the fact that

they were selected for the work because they had the cheapest price, not

because they had the safest jobs. On a long-term basis, perhaps it

could be shown that only a safe job can be profitable, but on a shortterm basis, most contractors cut the corners and incur risks that are in

fact a state-of-the-art in the construction industry.

Furthermore the state-of-the-art in the construction industry is different

than the state-of-the-art in the geotechnical engineering profession.

As long as the general accounting office and other government agencies

insist on picking contractors for the cheapest price, and ignore whatever

extra cost the contractor might incur in order to improve job safety, one might almost blame the owners and government agencies who demand

competitive bidding for some of the cost cutting that results in less

than a reasonable amount of job safety. Furthermore, this problem is

compounded by the fact that even if a soil study is made for a pipeline

job, and frequently they are not made, the chances of variations in soil

conditions between boring locations are substantial. Yet it is very

infrequently that a soil engineer is present on the site.

I think it is therefore crucial that the backhoe operators and the

plumbers and laborers all be able to function as paraprofessional s in

their own self-interest, certainly sufficiently to be able to differentiate

sand from clay, to recognize seepage, to look for shrinkage cracks and

evidence of impending slides, and generally to be familiar with the

primary sources of risk in excavation and trench work.

I hope these ideas are useful to you. I'm sorry they didn't get to you

before your October 20 deadline, but at least now you have them.

Sincerely,

SOIL TESTING SERVICES, INC.

John P. Gnaedinger

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