Safety Meeting Topics TRENCHING COMPETENT PERSON Copyright by

Safety Meeting Topics TRENCHING – COMPETENT PERSON Copyright by the Institute for Safety in Powerline Construction 3504 Parliament Ct. Alexandria, LA 71303 All rights reserved. This material or any part thereof may not be reproduced in any form without the written permission of the Institute for Safety in Powerline Construction

WHAT IS A COMPETENT PERSON? • • IDENTIFIES TRENCH HAZARDS IS AUTHORIZED TO TAKE PROMPT CORRECTIVE MEASURES TO ELIMINATE HAZARDS • • • IS RESPONSIBLE FOR DAILY TRENCHING INSPECTION • WORKS WITH THE PROFESSIONAL ENGINEER P ( E), COORDINATES THE EMERGENCY RESPONSE PLAN IS KNOWLEDGEABLE ABOUT SOILS, PROTECTIVE SYSTEMS, AND OSHA RULES WHO DESIGNS PROTECTIVE SYSTEMS

SESSION OBJECTIVES AS A “COMPETENT PERSON, ” YOU WILL BE ABLE TO: • • RECOGNIZE TRENCHING HAZARDS UNDERSTAND PROTECTIVE SYSTEMS FOR TRENCHES • UNDERSTAND HAZARDS AND PREVENTIVE MEASURES FOR ACTIVITIES ASSOCIATED WITH EXCAVATION

TRENCHING FATALITIES AND INJURIES • OVER 30 WORKERS DIE, 1, 000 INJURED PER YEAR • COMMON CAUSES: • NO PROTECTIVE SYSTEM • FAILURE TO INSPECT • UNSAFE SPOIL PLACEMENT • UNSAFE ENTRY AND EXIT

WHAT IS AN EXCAVATION? WHAT IS A TRENCH? • EXCAVATION—ANY HOLE OR TRENCH MADE BY REMOVING EARTH • TRENCH—A NARROW EXCAVATION THAT IS DEEPER THAN IT IS WIDE, NO GREATER THAN 15 FEET WIDE AT BOTTOM • TRENCH WALLS WILL EVENTUALLY FAIL

WHAT IS A CAVE-IN? • SOIL OR ROCK FALLS INTO AN EXCAVATION • OCCURS WHEN SOIL GRAVITATES DOWNWARD • OCCURS WHEN BOTTOM THIRD OF A TRENCH WALL FAILS Image Credit: OSHA

CONSEQUENCES OF A CAVE-IN • • • SOIL IS DENSE AND HEAVY CAVE-INS CAN ENTRAP, BURY, INJURE, OR IMMOBILIZE SUFFOCATION—SOIL PREVENTS • THE WORKER BECOMES CHEST EXPANSION IMMOBILIZED

SOIL CLASSIFICATION • • SOIL IS CLASSIFIED INTO DIFFERENT TYPES EACH TYPE REQUIRES A CERTAIN PROTECTIVE SYSTEM • COMPETENT PERSON DETERMINES SOIL TYPE

SOIL STABILITY AFFECTED BY: • • • GRAIN SIZE—SMALL IS BETTER WATER SATURATION COHESIVENESS—HOW WELL SOIL STICKS TOGETHER • UNCONFINED COMPRESSIVE STRENGTH (UCS)— HOW EASILY THE SOIL WILL SHEAR

SOIL TYPES—TYPE A IS: • • THE MOST STABLE SOIL TYPE COHESIVE SOIL WITH UCS OF 1. 5 TONS PER SQUARE FOOT (TSF) OR MORE • COHESIVE SOIL THAT IS PREDOMINANTLY CLAY • NOT FISSURED OR SUBJECT TO VIBRATIONS • NOT PREVIOUSLY EXCAVATED OR DISTURBED

SOIL TYPES—TYPE B IS: • • • COHESIVE SOIL WITH UCS >0. 5 BUT <1. 5 TSF GRANULAR, COHESIONLESS SOIL PREVIOUSLY DISTURBED SOILS EXCEPT THOSE WHICH WOULD OTHERWISE BE CLASSIFIED AS TYPE C SOIL • • AN “A” SOIL THAT IS FISSURED OR SUBJECT TO VIBRATION DRY ROCK THAT IS NOT STABLE

SOIL TYPES—TYPE C IS: • COHESIVE SOIL WITH UCS LESS THAN 0. 5 TSF • GRANULAR SOIL, INCLUDING GRAVELS • SANDY SOIL WHERE SAND IS DOMINANT • SUBMERGED SOIL OR SEEPING WATER • A DOWNGRADE OFTYPE B

SOIL TESTS • PLASTICITY TEST • DRY STRENGTH TEST • THUMB PENETRATION TEST • POCKET PENETROMETER

SIGNS OF SOIL DISTRESS • FISSURES OR CRACKS IN • WALL OF TRENCH • • SOIL BULGES OR HEAVES EXCAVATION’S EDGE • MATERIAL RAVELS OR TRENCH WALL SLUMPS OR FALLS SINKS TRICKLES INTO EXCAVATION Image Credit: OSHA

SOIL DISTRESS—CONDITIONS • • NEARBY VIBRATING MACHINERY NEARBY MOVING, HEAVY LOADS SEEPING WATER OR RAIN HOT, DRY WEATHER

TRENCHING HAZARDS DO YOU UNDERSTAND SPECIFIC TRENCHING HAZARDS? • • ABOUT CAVE-INS? ABOUT HAZARDS RELATED TO SOIL TYPES?

TRENCH PROTECTIVE SYSTEMS • • • SLOPING AND BENCHING SHORING SHIELDING Image Credit: OSHA

SLOPING AND BENCHING • SLOPING—ANGLING OF WALLS • BENCHING—SERIES OF STEPS • SOIL TYPE DETERMINES ANGLE OF SLOPE/BENCH • TYPE A (SLOPE RATIO. 75: 1) • TYPE B (RATIO 1: 1) • TYPE C (BENCHING NOT PERMITTED) (RATIO 1. 5: 1) AT AN INCLINE TO ANGLE WALLS Image Credit: OSHA

SHORING • USES SUPPORT WALLS TO PREVENT A CAVE-IN • USUALLY BUILT IN PLACE AND DESIGNED BY AN ENGINEER • COMPONENTS: • UPRIGHTS OR SHEETING • • WALES CROSS BRACES Image Credit: OSHA

SHIELDING • WITHSTANDS FORCES OF A CAVE-IN AND PROTECTS EMPLOYEES WITHIN • PERMANENT OR PORTABLE • TRENCH BOXES

SHIELDING—TRENCH BOXES • OFTEN DESIGNED TO STACK • NOT FOR HEIGHT EXTENSION • USED WITH SLOPING AND BENCHING • NO ONE PERMITTED INSIDE WHEN MOVING

WHAT’S WRONG HERE? • • IDENTIFY THE HAZARDS IDENTIFY MISSING PROTECTIVE SYSTEMS AND MEASURES Osha. gov

TRENCH PROTECTIVE SYSTEMS DO YOU UNDERSTAND TRENCHING HAZARDS? • • THE TYPES OF SOIL? THE TYPES OF PROTECTIVE SYSTEMS?

HAZARDOUS ATMOSPHERES AT EXCAVATIONS NEAR SEWERS, LANDFILLS, AND OTHER POTENTIALLY HAZARDOUS ATMOSPHERES: • TEST ATMOSPHERE WHEN DEEPER THAN 4 FEET • • VENTILATE OR USE APPROPRIATE PPE MAINTAIN RESCUE AND EMERGENCY EQUIPMENT ON-SITE

FALLING SOIL OR EQUIPMENT • LOOSE ROCK/SOIL THAT MAY FALL FROM AN EXCAVATION FACE • USE SCALING TO • USE SHORING OR REMOVE LOOSE SOIL SHIELDS • FALLING MATERIAL OR EQUIPMENT • KEEP • USE RETAINING MATERIAL/EQUIPMENT 2 FEET FROM EDGE DEVICES

ADJACENT STRUCTURES • EXCAVATIONS MIGHT ENDANGER STABILITY OF BUILDINGS, WALLS, OTHER STRUCTURES • SIDEWALKS AND PAVEMENTS MUST NOT BE UNDERMINED UNLESS SUPPORTED TO PREVENT COLLAPSE ONTO EXCAVATION WORKERS • USE SHORING, BRACING, OR UNDERPINNING TO ENSURE STABILITY OF NEARBY STRUCTURES

WATER ACCUMULATION • DROWNING HAZARD • TAKE PRECAUTIONS • USE SPECIAL SHORING OR SHIELDING SYSTEM • USE A WATER REMOVAL SYSTEM • USE A SAFETY HARNESS AND LIFELINE Image Credit: OSHA

ENTRY AND EXIT TRENCHES 4 FEET DEEP OR MORE MUST HAVE: • ENTRY AND EXIT WITHIN 25 FEET OF WORKER • ENTRIES AND EXITS INCLUDE: • • • LADDERS STAIRWAYS SLOPED RAMPS

OTHER TRENCHING ISSUES • STAND AWAY FROM LIFTING/ DIGGING EQUIPMENT • USE WARNING SYSTEMS OR BARRICADES • USE HARD HATS

OTHER TRENCHING ISSUES (CONT. ) • MARK ALL UNDERGROUND UTILITIES USING THE UNIFORM COLOR CODE • • USE FALL PROTECTION SYSTEMS NO WORK ABOVE OTHER WORKERS • MONITOR EXCAVATION WORK

TRENCH INSPECTIONS • INSPECT BEFORE WORK STARTS, THROUGHOUT SHIFT, AND AFTER RAINSTORM • INSPECT FOR: • EVIDENCE OF POSSIBLE CAVE-INS • INDICATIONS OF FAILURE OF PROTECTIVE SYSTEMS • POTENTIAL HAZARDOUS ATMOSPHERE • REMOVE WORKERS IF A HAZARDOUS CONDITION EXISTS

TRENCH INSPECTIONS OSHA Regulations Snap-Shot 1926. 651 as of November 2006: (k) Inspections. (1) Daily inspections of excavation, the adjacent areas, and protective systems shall be made by a competent person for evidence of a situation that could result in possible cave-ins, indications of failure of protective systems, hazardous atmospheres, or other hazardous conditions. An inspection shall be conducted by the competent person prior to the start of work and as needed throughout the shift. Inspections shall also be made after every rainstorm or other hazard increasing occurrence. These inspections are only required when employee exposure can be reasonably anticipated. (2) Where the competent person finds evidence of a situation that could result in a possible cave-in, indications of failure of protective systems, hazardous atmospheres, or other hazardous conditions, exposed employees shall be removed from the hazardous area until the necessary precautions have been taken to ensure their safety.

KEY POINTS TO REMEMBER • BE AWARE OF ALL THE HAZARDS ASSOCIATED WITH WORKING AROUND TRENCHES • CAVE-INS OCCUR SUDDENLY AND CAN ENTRAP, BURY, OR INJURE • • ALWAYS USE PROTECTION SYSTEMS REGULAR INSPECTIONS CAN HELP KEEP EVERYONE SAFE