RISK MANAGEMENT PROCEDURE

Transcription

1 RISK MANAGEMENT PROCEDURE SUBJECT: TRENCHING & SHORING SAFETY RULES R 6.0 EFFECTIVE: 06/13/01 REVIEWED: 1/15/18 I. PURPOSE The purpose of this procedure is to protect City employees who are required to work in excavations, by guarding/shielding them while they are working in an excavation, making repairs, or new construction. II. SCOPE These rules apply to all open site excavations including trenching made in the Earth s surface. Departments that conduct any type of excavation will adhere to this procedure. III. DEFINITIONS TYPE A SOIL - Cohesive soil with an unconfirmed compressive strength of 1.5 tons per square foot (tsf) or greater; or cemented granular soil as hardpan, till, or caliche, except for soils which are fissured, subject to vibration, has been previously disturbed, or the soil is part of a sloped, layered system where the layers dip into the excavation on a slope of 4 (horizontal) to 1 (vertical) or greater. Corpus Christi and Nueces County have NO type A SOIL. TYPE B SOIL - Cohesive soil with an unconfined compressive strength greater than 0.5 (tsf) but less than 1.5 (tsf); or granular soil that can stand on a slope of 3 (horizontal) to 1 (vertical) or greater without slumping; soil that meets the unconfined compressive strength or cementation requirements for TYPE A, but is fissured, subject to vibration or has previously been disturbed: dry rock that is not stable and material that is part of a sloped, layered system where the layers dip into the excavation on a slope less steep than 4 (horizontal) to 1 (vertical). For the most part Corpus Christi & Nueces County is comprised of type B SOIL which is mostly Victoria Clay and Sandy Loam. TYPE C SOIL Soft, cohesive, moist soil 60 (tsf) per foot of depth. Soil with an unconfined compressive strength of 0.5 (tsf) or less and not sub-merged or flowing water. Soil which can R 6.0 Trenching & Shoring Safety Rules Page 1 of 6

2 be excavated with near vertical walls and stand unsupported until trench shoring is installed. Sand. Flour Bluff and Padre Island are examples of where type C SOIL is present. Competent person An employee trained by an Accredited training Provider on the Excavation Safety Training for Competent Persons. The 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. IV. PROCEDURE Procedures, practices, and rules for working in an excavation, making repairs, or new construction are addressed in this procedure. If, after an investigation of the allegation, the City determines that an employee has violated these rules, disciplinary action up to, and including termination will be taken against the employee. Employees will be trained on an annual basis utilizing in-house expertise or an outside agency that specialize in this field. Training will be documented and filed in each respective department for future use. V. PROCEDURES See Shoring Standard Instruction for guideline procedures. Trenching and Shoring Standard Instructions A. REGULATIONS AND REQUIREMENTS 1. Never stand or move under loads handled by lifting or digging equipment. 2. DO NOT work beyond the protected area of the trench. 3. All material and soil must be stored no closer than 2 feet (.61 m) from the wall of the trench. 4. Means of egress from trench excavation: A stairway, ladder, ramp, or other safe means of egress shall be located in trench excavations that are 4 feet (1.22 m) or more in depth so as to require no more than 25 feet (7.62 m) of lateral travel for employees. 5. If an excavation is more than 5 feet (1.52 m) in depth and not in stable rock, then there is the potential for cave-in. The excavation must be sloped, shored, or shielded. If the excavation is less than 5 feet (1.52 m) in depth and soil conditions warrant, then they should be sloped, shored or shielded. 6. If soil conditions warrant, the entire depth of the trench must be fully shored. 7. Sloping or benching for excavations greater than 20 feet (6.09 m) deep shall be designed by a Registered Professional Engineer. R 6.0 Trenching & Shoring Safety Rules Page 2 of 6

3 8. Crews may work in excavations in which water has accumulated or is accumulating, provided: i. Supervisor trained in trenching safety is on site to oversee the project. ii. Excavations and shoring that have standing water or remain wet will be checked as often as deemed necessary by the Supervisor trained in trenching safety. iii. Water is controlled or prevented from accumulating by the use of water removal equipment, the water removal equipment and operations shall be monitored by a supervisor trained in trenching safety to ensure proper operation. 9. In the event of a cave-in, employees should not enter the excavation. B. DESIGN AND DECISION FOR PARTICULAR JOB 1. Close proximity to heavy traffic, railroads, airports, buildings and bodies of water all create added pressure on trench walls. Consult a Professional Engineer for these or any other special applications. 2. Shields (trench box) can be permanent structures or can be designed to be portable and moved along as work progresses. Additional, excavations of earth material to a level not greater than 2 feet (.61 m) below the bottom of a shield shall be permitted, but only if the shield is designed to resist the forces calculated for the full depth of the trench, and there are no indications while the trench is open of a possible loss of soil from behind or below the bottom of the shield. C. MATERIALS AND EQUIPMENT 1. Install proper barricades around work area/excavation to protect personnel from falling into the excavation and to warn vehicular traffic that the trench exists. 2. DO NOT enter trench without personal protective equipment. D. PROCEDURES AND EXECUTION OR IMPLEMENTATION 1. Before beginning excavation, locate all utilities and cables. 2. When installing shoring cylinders or screw jacks adjustments should be completed from the top cylinder downward into the trench. When removing shoring cylinders or screw jacks, release should be completed from the bottom cylinder upward to the top of the trench. 3. All trench excavations and shoring are to be checked daily by a competent person trained in trenching safety prior to the start of work. The employee trained in trenching safety should confirm that the system is functioning according to the specified design requirements and has not been damaged or altered detrimentally from the initial installation condition. R 6.0 Trenching & Shoring Safety Rules Page 3 of 6

4 E. SOIL CLASSIFICATION The maximum allowable slopes Horizontal: Vertical (H: V) for excavations less than 20 feet in depth can be figured from the table below: Notes: STABLE ARTICLE (90) ROCK TYPE A 3/4-1 (53) TYPE B 1-1 (45) TYPE C 1 ½ - 1 (34) 1. Numbers shown in parentheses next to maximum allowable slopes are angles expressed in degrees from horizontal, angles have been rounded off. 2. A short-term maximum allowable slope of ½ H:1V (63) is allowed in excavations in TYPE A soil that are twelve (12) feet (3.67 m) or less in depth. Short-term maximum allowable slopes for excavations greater than twelve (12) feet (3.67 m) in depth shall be 3/4 H:1V (53). 3. Sloping or benching for excavations greater than twenty (20) feet deep shall be designed by a Registered Professional Engineer. An employee trained in trenching safety (competent person) is the 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. VI. PROCEDURE UPDATE This procedure shall be reviewed on an annual basis by the Safety Advisory Board (S.A.B.). Revisions to the procedure shall be approved by the Safety & Risk Manager and by the City Attorney. VII. QUESTIONS REGARDING THIS PROCEDURE Questions regarding this Procedure shall be directed to the Safety & Risk Manager, or designee, who may be contacted at 361/ R 6.0 Trenching & Shoring Safety Rules Page 4 of 6

5 City of Corpus Christi Trenching and Shoring Guidelines Date: - - Time: : am/pm Soil Job Location: Job Type: Classification Q Stable Rock Q TYPE A **See reverse side Q TYPE B **See reverse side Q TYPE C **See reverse side Resources YES NO Protective systems & excavations Contact all utility/traffic owners Is excavation (5) feet deep or more YES No Pipeline(s) - refinery line markers Other Calls Previously disturbed ground Vibration Sources Other known obstructions Air monitoring/what % Weather conditions Is trench (25) feet long Ladders needed, how many Cross over walkways Water removal equipment, ie. Water pumps Comments: Sloping/benching, ratio Aluminum hydraulic shoring Timber Shoring Alternatives to timber shoring Portable trench boxes/shields Registered Professional Engineer-designed shoring Support system for working underneath sidewalks etc. Competent Person: D:/T&S/ rj -mt/.wpd **Note: See reverse side for additional information Date: Definitions: TYPE A SOIL - Corpus Christi & Nueces County have NO TYPE A SOIL. TYPE B SOIL - For the most part Corpus Christi & Nueces County is comprised of TYPE B SOIL which is mostly Victoria Clay and Sandy Loam. TYPE C SOIL - Sand: Flour Bluff and Padre Island are examples of where TYPE C SOIL is present. R 6.0 Trenching & Shoring Safety Rules Page 5 of 6

6 Trenching and Shoring Safety Rules ACKNOWLEDGMENT FORM I have received a copy of the City of Corpus Christi s procedure R 6.0 Trenching and Shoring Safety Rules, and I understand that compliance with these rules is a condition of employment with the City of Corpus Christi. I have carefully heard and/or read these rules and understand its content. I have been given an opportunity to ask questions about these rules and to receive explanations in English and Spanish. I agree to comply with these rules. I understand that failure to do so will result in my being in violation of these rules and will subject me to disciplinary action up to and including termination for the first offense. Employee s Name (Printed) Employee ID Number Employee s Signature Date Department Name Department Org. Number Form Reviewed by: Department Director, or Designee Date PLEASE RETURN TO: Human Resources Department, Records Section R 6.0 Trenching & Shoring Safety Rules Page 6 of 6