Excavations, Trenching and Shoring

Prior to opening an excavation, effort shall be made to determine whether underground installation such as sewer, water, fuel and electrical lines are encountered and if so, where such underground installations are located. When the excavation approaches the estimated location of such installation, carefully probing or hand digging shall determine the exact location and when it is uncovered, the existing installation shall be properly supported. Utility companies shall be contacted and advised of proposed work prior to the start of actual excavation. In a means to maintain a filing and record-keeping documentation of excavation work in locating and marking of underground facilities, we are required to do the following information; county, township, city or town, street address, type of work, extent of work, start date, start time, your name, your title and return telephone number. ESCO Group’s Safety Director will call Iowa One Call and communicate all information back to you before we dig.

1. General Requirements

a) Local, state and federal ordinance shall be complied with in all general excavation requirements. 

b) Barriers and barricades shall be placed on both sides of the excavation to deter the passage of persons or vehicles.  Where walkways or crossing are provided to cross over excavations, guardrails shall be provided to guard against falls and the guardrails shall meet the OSHA requirements.

c) Excavated or other material shall not be stored nearer than four feet from the edge of any excavation and shall be so stored and retained as to prevent its falling or sliding back into the excavation.  No employee shall be permitted underneath loads handled by lifting or digging equipment to avoid being struck by any spillage or falling materials.

d) Sides of trenches in hard or compact soil, including embankments shall be shored or otherwise supported when the trench is more than four feet in depth and eight feet or more in length. In lieu of shoring, the sides of the trench above the four foot level may be sloped to preclude collapse, but shall not be steeper than a one foot rise to each 1/2 foot horizontal. 

e) Materials used for sheeting or sheet piling bracing, shoring or underpinning shall be in good serviceable condition and timbers used shall be sound and free from large or loose knots and shall be designed and installed so as to be effective to the bottom of the excavation. 

f) Adequate precautions shall be taken to prevent employee exposure to atmospheres containing less than 19.5 percent oxygen and other hazardous atmospheres.  These precautions include providing proper respiratory protection or ventilation.  When controls are used that are intended to reduce the level of atmospheric contaminants to acceptable levels, testing shall be conducted as often as necessary to ensure that the atmosphere remains safe.  In locations where oxygen deficiency condition is possible, use a mechanical blower to provide the necessary amount of fresh air. 

g) When employees are required to be in trenches four feet deep or more, ladders extending from the floor of the trench excavation to three feet or more above the top of the trench shall be provided and located to provide means of exit without more than 25 feet of lateral travel. 

h) Daily inspections of excavations shall be made by a competent person.  If any evidence of possible cave-ins or slides is apparent, do not permit employees to work in the trench.  “Competent person” means one who is capable of identifying existing and predictable hazards in the surroundings, or working conditions, which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them.

i) Before leaving the work area at quitting time, the supervisor in charge shall see that machinery and tools are properly stored at the trench site and not left in the “on” position. 

j) Employees shall not work in excavations where there is accumulated water, or in excavations in which water is accumulating, unless adequate precautions have been taken to protect employees against the hazards posed by water accumulation.

k) Each soil and rock deposit shall be classified by a competent person as Stable Rock, Type A, Type B, or Type C.  The classification of the deposits shall be made based on the results of at least one visual and at least one manual analysis.  (1) Visual tests.  Visual analysis is conducted to determine qualitative information regarding the excavation site in general, the soil adjacent to the excavation, the soil forming the sides of the open excavation, and the soil taken as samples from excavated material. (2) Manual tests.  Manual analysis of soil samples is conducted to determine quantitative as well as qualitative properties of soil and to provide more information in order to classify soil properly.  Plasticity:  Mold a moist or wet sample of soil into a ball and attempt to roll it into threads as thin as 1/8-inch diameter.  Cohesive material can be successfully rolled into threads without crumbling.  Thumb penetration:  The thumb penetration test can be used to estimate the unconfined compressive strength of cohesive soils.

l) Each employee in an excavation shall be protected from cave-ins by an adequate protective system or sloping, benching of the soil except when: Excavations are made entirely in stable rock; or Excavations are less than 5 feet (1.52 m) in depth and examination of the ground by a competent person provides no indication of a potential cave-in.  Protective systems shall have the capacity to resist without failure all loads that are intended or could reasonably be expected to be applied or transmitted to the system.

Maximum Allowable Slopes