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Transcription

1 Introduction Pg 2 Learning online might be tricky if you're not sure how to navigate this site. To be sure you get the learning you need from this course, read the following Navigation pages carefully. Pg 3 Pg 4 Pg 5 Page-by-page navigation icons appear in the lower right-hand corner. You can move forward one page by selecting Next. Select Next now to move to the next page. A standard design frames every page of the course. You will find the Table of Contents in the drop-down menu along the top of the screen. Run your mouse over the list of lessons at the top of the screen and you will see these dropdown boxes. Your first time through the course, you can look at the contents in these dropdown boxes, but you will not be able to skip ahead. After you go through the course once, you can use the Table of Contents to skip around and review for the exam. Your progress through the course is tracked. If you must leave at any time, don't worry. You will be taken back to the same screen when you return. Audio On/Off allows you to disable audio for the course. If you are taking the course in an area where you cannot hear the audio, you can download a printable audio transcript by selecting Transcript. Pg 6 Pg 7 A Resources link appears when additional learning tools like printable documents or web links are provided. Select Resources now to visit J. J. Keller's web site. The site will open in a new browser window and will not interfere with your movement through this course. Simply close the new browser window to return to the course. Throughout the course, you will see special terms set in blue, bold text. Roll your mouse over these terms to read their definitions. The downloadable Glossary, available on the first and last page of the course, is a collection of these terms. Another resource you will encounter is a Fact Sheet (in Time to Review). The Fact Sheet will help you review main concepts covered on the exam. Allowing Pop-ups If you had trouble opening the J. J. Keller link, you may have a pop-up blocker. This course will not work correctly unless all browser-based and third-party pop-up blockers are disabled. To allow pop-ups in Internet Explorer, select Tools > Internet Options > Privacy, and uncheck Turn on Pop-up Blocker. To allow pop-ups in Mozilla Firefox select Tools > Options > Content, and uncheck Block Pop-up Windows. If you're uncomfortable making any of these changes yourself, ask your supervisor or technology expert for help. 1 Excavation

2 Pg 8 Pg 9 Text Size Web designers don't have much control over the size of the text font. To increase the size of the text in this course you must change the font display standard in your web browser: To increase text size using Internet Explorer, select Page or View > Text Size. To increase text size using Mozilla Firefox select View > Text Size. Or change the default display font by selecting Tools > Options > Content > Fonts and Colors. Many parts of this course will feature video. The video player controls are detailed in the image to the right. The timer counts down from the total video length. The video can be played in two different speeds. Select the faster speed for a better-quality video. Select the slower speed if traffic on your network is heavy. Now that you know how to navigate through the course select Next to get started! Pg 10 When you select Next, you will begin the pretest for this course. Your score will be reported to you, but will not be recorded. There are 10 questions in this pretest. No matter what your specific job is, if you are going to be working in or near an excavation, you should have a working knowledge of OSHA's excavation safety Pg 12 standard. Pg 13 In this course, we'll look at how to avoid becoming the victim of excavation accidents, and prevent others from being injured too. When you're finished with the course you should be able to: Know the difference between excavations and trenches Identify what needs to be done before an excavation begins Explain the role of a competent person at an excavation List the different soil classifications and their main properties Identify various protective support systems Know what to do in the event of an excavation cave-in Excavation Hazards Working in a trench is one of the most common and one of the most dangerous jobs in construction work. Every year, 40 to 60 workers die, and more than 1,000 are injured, in trenching and excavation accidents. Of all trenching Pg 2 fatalities, 79% occurred in trenches that were less than 15 feet deep. Trenches less than 10 feet deep were the site of 38% of all fatalities. The fact is, most people do not understand the power behind falling and crushing dirt. One cubic yard of soil weighs 5 times the world's weightlifting record of 521 pounds. Can you push back 500 pounds of soil with your arms or legs or, more importantly, could you breathe or even survive under the weight? 2 Excavation

3 Pg 3 Not likely. Select Play to watch a demonstration of how soil can collapse a worker's lungs. Video: A cubic foot of soil is not very much, but it weighs about 100 pounds. Just one cubic yard of soil weighs about 27-hundred pounds about as much as a midsized car. When three, four, or more cubic yards of soil press against the human body, there s enough pressure to prevent the lungs from expanding. Suffocation can take place in just a few minutes. Pg 4 Pg 5 Pg 6 Pg 8 Pg 9 The terms excavation and trenching are somewhat synonymous. The saying goes: all trenches are excavations but not all excavations are trenches. An excavation is any human-made cut, cavity, trench, or depression in the earth's surface formed by earth removal. This can include excavations for anything from a sewer line installation to multi-lane interstate highways. A trench is a narrow excavation made below the surface of the ground. Trenches are deeper than they are wide (as long as they are not wider than 15 feet). Excavation and trenching projects can be very small digs, or very large undertakings. For example, a trench may be only a few feet deep and may be dug in less than one hour by one person using a backhoe. A small excavation may simply be a hole scooped out by a bulldozer. At the other extreme, the construction of a stable 30-foot deep trench requires knowledge of engineering, geology, and soil mechanics. Cave-ins are probably the most feared trenching hazard. Cave-in accidents are much more likely to be fatal than other construction-related accidents. In a cave-in, workers are either asphyxiated or fatally injured by falling soil or rock. In addition to cave-ins, there are many other potentially fatal hazards related to excavation work. Workers can suffocate due to lack of oxygen in a confined space or die after breathing toxic fumes that come from chemicals, equipment exhaust, underground storage tanks, landfill areas, or hazardous waste materials. Water main breaks can drown workers. An excavation near utility lines can be as deadly as a mine field: electrocution or explosions can occur when workers come in contact with underground utilities. Pg 10 Additional hazards result from material or equipment falling into the excavation. Fatalities have been the result of "struck by" accidents (workers in the trench or at the surface can be struck by pipes or other materials) and falls. When excavation work causes structures that adjoin the trench or excavation to become unstable, these walls or structures can give way and fall on workers. 3 Excavation

4 Pg 11 Other concerns involve working near traffic and around heavy equipment used in excavation operations. Workers are not allowed under loads being handled by lifting or digging equipment. Stand away from vehicles that are being loaded or unloaded to avoid being struck by spillage or falling materials. Whenever mobile equipment is in operation next to an excavation, or when it must approach the edge of an excavation, the operator must be warned if there is not a clear and direct view of the excavation's edge. If possible, the grade should be away from the excavation to help prevent equipment from rolling toward the edge. Pg 13 You must be protected from cave-ins and other hazards by a protective system designed according to OSHA standards. OSHA's excavation rules apply to all open excavations made in the earth's surface, including trenches. There are two circumstances when a protective system is not required. The first is an excavation made in stable rock. The second is an excavation that is less than 5 feet deep. This site must be inspected by the competent person, who determines that there is no indication that a possible cave-in will occur. Pg 14 You can remember OSHA's requirements by remembering the 4-foot and 5-foot rules: The 4-foot rule If you are working in a trench that is at least 4 feet deep, you must have a way to get in and out of the trench (and you shouldn't have to walk more than 25 feet to reach the way out). The 5-foot rule Working in any excavation, you must be protected from cave-ins by an adequate protective system unless the excavation is entirely in stable rock, or less than 5 feet deep and the competent person inspects the excavation and determines there is no indication of a potential cave-in. Pg 15 When you select Next, you will begin the test for this lesson. There are 5 questions in this test. Your score will be reported to you, but will not be recorded. If you do not get at least 3 questions correct, you will be advised to review the lesson and take the lesson test again. You may take the lesson test as many times as you wish. Protective Systems Pg 2 Before you start to excavate, a competent person will need to: Contact utility companies and the property owner to ensure underground installations are found 4 Excavation

5 Pg 3 Make sure underground installations are protected, supported, or removed as necessary to safeguard employees Remove or secure any surface obstacles, such as trees, rocks, and sidewalks, that may create a hazard Classify the type of soil and rock deposits at the site. One visual and at least one manual analysis must be made. Because of the very real threat of electrocutions and explosions, the importance of notifying utility companies should not be understated. Select Play to learn more about the responsibility of the competent person at an excavation site. Video The OSHA excavation standard refers to someone called a competent person who s required to inspect the excavation and adjacent areas at least once a day. Of course, this doesn t mean that everyone else at the jobsite is NOT competent. It s simply the term for the person who is assigned these responsibilities. The competent person is trained to identify excavation hazards and authorized to stop work if necessary to eliminate those hazards. He or she may also be responsible for coordinating and directing emergency response procedures, if needed. At large operations, the competent person could be a full-time safety official who makes recommendations to improve on-the-job safety. At some job sites, a supervisor may be the competent person, as defined by OSHA. At each excavation site, the competent person must inspect for possible caveins, potential failures of protective systems and equipment, hazardous atmospheres, and other hazardous conditions. Pg 4 If a hazardous condition exists, it must be corrected before you continue work. For example, if there s a hazardous atmosphere, your company must attempt to ventilate the excavation or provide you with a respirator. Before you can work in an excavation, the soil type must be determined. Soil classification is used to determine the need for a protective system. The soil must be classified as: stable rock, type A, type B, or type C soil. Stable rock is the most stable, with type C soil being the least stable. It is not uncommon to find a combination of soil types at an excavation site. If you are unsure of the soil type, always assume it is type C. 5 Excavation

6 Pg 5 Visual tests include identifying the soil s particle size, observing how it clumps as it is excavated, looking for fissures in the side and surface of the excavation, looking for previously disturbed soil, identifying the degree of slope in the layers of layered soil systems, looking for evidence of seeping water, and identifying any sources of vibration in the area adjacent to the excavation. Manual tests include determining the soil s plasticity, dry strength, thumb penetration, other strength tests, and the drying test. Pg 6 Pg 7 Pg 9 The definitions of the different soil types are: Stable rock Natural solid mineral material that can be excavated with vertical sides and will remain intact while exposed. Type A soil Examples include clay, silty clay, sandy clay, clay loam, and sometimes silty clay loam and sandy clay loam. Type B soil Examples include angular gravel, silt, silt loam, sandy loam and sometimes silty clay loam and sandy clay loam. Type C soil Examples include granular soils like gravel, sand, loamy sand, submerged soil, and soil from which water is freely seeping, and submerged rock that is not stable. Designing a protective system involves more factors than just the soil type depth of cut, water content of soil, changes due to weather, and other operations nearby must also be considered. Let's review the types of soil. Select Play to hear them described on video. Video Stable rock is natural solid mineral matter that can be excavated with vertical sides and will remain intact while exposed. Type A soil has an unconfined compressive strength of one-and-a-half tons per square foot or greater. This means that Type A soil is generally cohesive and stable. Type B soil has an unconfined compressive strength greater than one-half ton per square foot but less than one-and-a-half tons per square foot. This means that Type B soil is granular and less cohesive than Type A. Granular soil breaks up easily and does not stay in clumps. Examples include silt, and sandy loam. Type C soil has an unconfined compressive strength of one-half ton or less. Examples of Type C soil include gravel, sand, submerged soil, and soil with seeping water. 6 Excavation

7 Pg 10 When protective systems are needed, employers are free to choose the most practical design approach for a particular circumstance. Of course the required performance criteria for the system must be met. Types of protective systems include: Proper sloping and/or benching of the sides of the excavation Supporting the sides of the excavation with timber shoring or aluminum hydraulic shoring Placing a shield between the sides of the excavation and your work area Pg 11 One type of protective system is to slope the excavation's sides to a safe angle. The angle varies based on many jobsite factors. Pg 12 Benching systems excavate the sides of an excavation to form a series of horizontal levels or steps, with vertical or near-vertical surfaces between levels. Select Play to learn about the angles required for various soil types when using sloping or benching as protective systems. Video Using the sloping method, the sides of the trench are angled away from the excavation to prevent a cave-in. The benching method uses a series of horizontal levels or steps to keep the walls of the excavation stable. The angle formed by the steps is determined by the soil type. The OSHA Excavation Standard lists the maximum allowable slopes for all soil classifications. Again, determining the correct soil type and slope is the responsibility of the competent person, but it s your life on the line, so you should know about these rules too. In a stable rock excavation that is less than 20 feet deep, the maximum allowable slope is 90 degrees, which is vertical. In Type A soil, the maximum allowable slope for excavations less than 20 feet deep is 53 degrees. This means that for every three-fourths of a foot horizontally, the vertical rise should be no more than one foot. The angle of slope should always be measured from the toe of the trench, which is the outermost edge of the excavation NOT from the center. In Type B soil, the maximum allowable slope for excavations less than 20 feet deep is 45 degrees, or one foot horizontally for every one foot vertical rise. 7 Excavation

8 For Type C soil, the maximum allowable slope for excavations less than 20 feet deep is 34 degrees or one-and-one-half feet horizontally for every one foot vertical rise. There are a number of exceptions or special cases to the general sloping and benching guidelines. For example, for excavations 20 feet deep or less with vertically-sided lower portions that are supported or shielded, the support or shield system must extend at least 18 inches above the top of the vertical side. We ll talk more about supports and shields in a moment. When an excavation contains layers of different types of soils, the usual sloping requirements need to be varied. The layered system must be classified according to its weakest layer. The OSHA Excavation Standard lists sloping requirements for layered soils. Pg 13 Although not commonly used today, another type of protective system is shoring. Shoring systems protect against cave-ins by supporting the sides of the excavation with timber, aluminum hydraulic, or mechanical systems. They are made of cross braces, wales and uprights. Pg 14 Another type of protective support system is a shield. A shield is a structure used in excavations to withstand cave-ins and which will protect workers inside of it. Shields can be permanent structures or portable units moved along as work progresses. Shields used in trenches are usually called trench boxes or a trench shield. OSHA permits the use of trench boxes or shields as long as the protection provided is equal to or greater than the protection that would be provided by the appropriate shoring system. Select Play to learn more. Video Before using a trench box, it should be inspected by the competent person for damage or defects. If it looks like there are any problems, you should report them to your supervisor or the competent person and the shield should not be used. Several types of shields are manufactured for specific size trenches. Make sure you re using the proper shield. Always follow the manufacturer s guidelines for installing a shield. Overloading the system could lead to a cave-in. No one should ever be inside a shield while it s being installed, removed, or moved vertically. Excavation is permitted below the bottom of the shield, but only to a depth of two feet, and only if the shield is designed to resist the forces calculated for the 8 Excavation

9 full depth of the trench. There must also be no indication that soil will become loose either from behind or below the bottom of the shield. Pg 16 OSHA also has requirements for how workers enter and exit (access and egress) excavations. Trenches that are at least 4 feet deep require a safe (fixed and secure) means of egress, such as stairways, ladders, or ramps. They must be designed by a competent person and spaced so that you don't have to walk more than 25 feet to the closest "means of egress," or way out of the trench. When ladders are used, they must be secured and extend at least 3 feet above the landing. Use metal ladders with extreme caution, especially when electric utilities are present. Pg 17 Remember the 4-foot rule? Here are some requirements and techniques for getting in and out of the trench depending on the method used: Structural ramps Structural ramps must be designed by a competent person. Ramps and runways consisting of two or more members must be securely connected to prevent displacement. Structural members must be of uniform thickness. Structural ramps used in place of steps must have cleats or a nonslip surface to prevent tripping. Pg 18 Ladders For trench applications, ladders must be used in the same manner as in any other application. Some of the issues are: Ladders must be inspected for damage or defects. Damaged or defective Ladders must not be used. Ladders must be stable at the bottom and secured at the top and extend the minimum three feet above the upper surface of the excavation. Metal ladders must be used with caution, particularly when electric utilities are present. You must not carry objects or loads while on the ladder that could cause you to lose your balance and fall. Pg 19 Earthen ramps You must be able to walk upright if an earthen ramp is used for access and egress. The ramp must be evaluated by a competent person. Pg 20 When you select Next, you will begin the test for this lesson. There are 5 questions in this test. If you do not get at least 3 questions correct, you will be advised to review the lesson and take the lesson test again. You have 3 chances to take the lesson test. Your highest score will be recorded. Safety Measures 9 Excavation

10 Pg 2 As always, the best way to stay safe is to eliminate hazards. But some hazards can t be easily eliminated. Make sure you are using the proper personal protective equipment (PPE). Hard hats are important for trench work when there are overhead hazards while working alongside the trench (digging equipment) or in the trench (falling objects). Pg 3 Pg 4 Ventilation equipment or respirators may be required if there is an atmospheric hazard or there is a possibility of an atmospheric hazard. Don't forget about eye and face protection, hand and foot protection, and hearing protection. Your employer is responsible for providing PPE. Make sure you know how to use it and that it fits properly. When you work in excavations or trenches, you should also be able to recognize a hazardous condition. A sudden change could mean disaster for you and your fellow workers. If anything goes wrong, you must have the ability to act instantly. This takes training, practice, and most of all, alertness. Pg 5 Pg 6 Here are some examples of the things that could cause an immediate change at an excavation site: A bulldozer or excavator coming too close to your trench could cause an overload resulting in stress cracks at or near the edge of the trench. A sudden downpour could fill the trench or cause rain-soaked soil to give way. Accidentally striking an underground utility line with a backhoe could result in an immediate electrocution. Be alert for other signs of trouble, such as: Tension cracks in walls, slopes, or ground near the excavation Ground settlement or sinking Changes in wall slope or bulging Spalling or crumbling soil inside the trench Excessive seepage and piping of fine soils Boiling of the trench bottom Creaking or popping sounds The bracing system bending and deforming Pg 7 Pg 9 If anything goes wrong, be ready to act instantly. Now that you've learned about staying safe at an excavation site, select Next to play a "spot the hazards" game that tests your knowledge. OSHA requires emergency rescue equipment when a hazardous atmosphere exists or could develop during excavation work. But your company should have emergency response procedures in place, and rescue equipment ready, in case any accident occurs. The procedures should include: Who will provide immediate jobsite rescue and aid? 10 Excavation

11 Who will notify the authorities and rescue personnel? What emergency response equipment will be available on the jobsite, where will it be kept, and who is trained to use it? Pg 10 If there is an accident at the excavation site, the time between when the accident happens and when rescue personnel arrive is critical. Any help that you can give the victim, without endangering yourself, should be done immediately. Avoid using heavy equipment in a rescue attempt of a trapped person. You must use extreme caution in this situation. Pg 11 Working in confined spaces requires extra training and equipment. Your employer must provide independent lifelines if you will be entering bell-bottom pier holes, deep confined spaces, or other similar hazards. And someone must be attending these lifelines at all times. Pg 12 When you select Next, you will begin the test for this lesson. There are 5 questions in this test. If you do not get at least 3 questions correct, you will be advised to review the lesson and take the lesson test again. You have 3 chances to take the lesson test. Your highest score will be recorded. Conclusion Pg 2 Working in a trench doesn t have to be a dangerous occupation. As long as everyone knows what the rules are and follows them every day excavation work can be done safely and efficiently. So don t assume that someone else is going to take care of following excavation rules. You need to do your part, too. Know what the rules are, what the hazards look like, and in some cases what they sound like. That way you can do your part to control or eliminate hazards and keep your jobsite safe. Pg 3 Now that you've covered everything in this course, it's time to review for the exam. To help you prepare for the exam, you can now move back and forth within the course. Use the drop-down menus at the top of the screen, or the Back and Next buttons at the bottom. The Fact sheet will also help you review main concepts covered on the exam. To download and print the Fact sheet, select Resources. Keep the original course window open. Once you've finished reviewing the Fact sheet, select Next to download the Review questions. 11 Excavation

12 Pg 4 The review questions will open in a separate window. Keep this original window open. That way when you don't know an answer, you can go back into the course and find it. Once you've finished the review questions, and have finished studying, continue on to take the exam. To begin the review questions, select Resources. Pg 5 Now it s time to take the final exam. This exam will include 20 questions. If you close the exam before finishing, your answers will not be saved for later. If you do not get at least 14 questions correct, you will be prompted to review the lessons and take the final exam again. You get 3 chances to take the final exam. Your highest score will be recorded. Pg 7 To begin the exam, select Next. Congratulations! You have completed this course. Your progress and test scores have been recorded. 12 Excavation