4.2.6 Student Book © 2004 Propane Education & Research Council Page 1

4.2.6

Performing Trenching, Digging,

& Backfilling Operations

Proper soil excavation is an important step in preparing for the installation of a propane vapor distribution system.

In this module you will learn to identify:

(1) Necessary preparations for excavation

(2) Safety precautions for operating trenching/digging equipment

(3) Typical equipment and techniques used in trenching/digging operations

(4) Typical backfilling operations

4.2.6 Student Book © 2004 Propane Education & Research Council Page 1

Necessary Preparations for Excavation

Before excavating complete the following:

1. Decide where the components (DOT exchange cylinders, stationary cylinders, AG ASME tank, or UG ASME tank) of the distribution system are to go.

2. Check the layout and markings of the installation (stakes or spray markings).

Figure 1. Flagging Marks the Layout

4.2.6 Student Book © 2004 Propane Education & Research Council Page 2

Necessary Preparations for Excavation

Before excavating complete the following:

3. Call your state “One-Call” service unit and/or local utility companies (electrical, fuel, water, sewer, cable, etc.) for assistance in identifying locations of any utilities. (Figure 2).

4. Contact utility companies or owners within established or customary local times, advise them of the proposed work, and ask them to establish the location of the utility underground installations prior to beginning the excavation.

Figure 2. Identify Locations of

Underground Utilities

4.2.6 Student Book © 2004 Propane Education & Research Council Page 2

Necessary Preparations for Excavation

Before excavating complete the following:

5. Ask the [property] owner about any underground utilities. These might include septic tanks, drain fields, sprinkler systems, wiring to ornamental fixtures on the site, etc.

Note:

When utility companies or owners cannot respond to a request to locate underground utility installations within 24 hours (unless a longer period is required by state or local law), or cannot establish the exact location of these installations, the employer may proceed, provided the employer does so with caution, and provided detection equipment or other acceptable means to locate utility installations are used. (OSHA regulatory requirement)

4.2.6 Student Book © 2004 Propane Education & Research Council Pages 2 & 3

Safety Precautions for Operating Trenching/Digging Equipment

Basic safety rules include:

• Before beginning work, thoroughly inspect the equipment to be sure it is in good operating condition. Use the operator's manual to determine items to be checked.

• Keep the machine clean. Remove any excess oil and grease. Store tools and other necessary items in the tool box.

• Clean mud or grease from your shoes before attempting to mount or operate riding-type equipment. Be sure the foot pedals are clean and dry to reduce the possibility of your shoes slipping off the pedals. Also make sure to keep all hand-operated controls clean and free of grease.

• Clothing should be relatively close fitting. Loose jackets, shirt sleeves, rings, and other jewelry should be avoided because of the danger of catching them in moving parts or on controls.

4.2.6 Student Book © 2004 Propane Education & Research Council Page 3

Safety Precautions for Operating Trenching/Digging Equipment

Basic safety rules include:

• Always wear required protective items such as hard hats, safety glasses, reflective clothing, safety shoes, and ear protection, as needed and required by your company’s policies and procedures.

• Be sure that all safety devices provided are in place and in good operating condition. Be familiar with the use of all safety devices, including lights, seat belts, and back-up horn.

Figure 3. Rollover Protective Structure (ROPS)

4.2.6 Student Book © 2004 Propane Education & Research Council Page 3

Safety Precautions for Operating Trenching/Digging Equipment

Basic safety rules include:

• When operating the tractor/loader/backhoe, use the seat belt at all times. It will keep the operator in the seat, and able to maintain control of the TLB. If it turns over, the seat belt will keep the operator from being thrown from the TLB.

• Plan ahead, work safely and avoid accidental damage and injury. If an accident does occur, react quickly with the tools and skills at hand. Know how to use a first aid kit and a fire extinguisher, and how to get assistance.

• To prevent accidents, make sure the exact locations of obstructions or hazards are known and marked.

4.2.6 Student Book © 2004 Propane Education & Research Council Page 4

Typical Equipment & Techniques for Trenching/Digging Operations

Equipment Used in Trenching Operations

• Handlebar trencher (operator walks)

• Rubber-tired trencher (operator rides)

• Crawler trencher (operator rides)

• Trenching shovel (used by hand)

Figure 4. Consult the Manufacturer’s Manual for Your Equipment

The operator of any trenching equipment should follow all safety and operating procedures outlined in the manufacturer’s manual or handbook for that specific piece of equipment.

4.2.6 Student Book © 2004 Propane Education & Research Council Page 4

Typical Equipment & Techniques for Trenching/Digging Operations

Handlebar Trencher

Figure 5. Handlebar Trencher

The handlebar trencher is the most common of all trenching equipment used at residential and commercial sites. The operator walks behind the trencher guiding it with the handlebars.

4.2.6 Student Book © 2004 Propane Education & Research Council Page 5

Typical Equipment & Techniques for Trenching/Digging Operations

Rubber-Tired Trencher

Figure 6. Rubber-Tired Trencher

4.2.6 Student Book © 2004 Propane Education & Research Council Page 5

Typical Equipment & Techniques for Trenching/Digging Operations

Crawler Trencher

Figure 7. Crawler Trencher

4.2.6 Student Book © 2004 Propane Education & Research Council Page 6

Typical Equipment & Techniques for Trenching/Digging Operations

Trenching Shovel— On small, less complicated projects, a trenching shovel (Figure 8) may be used to dig the trench by hand.

Figure 8. Trenching Shovel

Note:

Trenching for propane vapor distribution lines will typically be 12” deep. Under some soil conditions and closeness of rock to surface, less depth will be necessary. Always follow company policy regarding depth of trenching.

4.2.6 Student Book © 2004 Propane Education & Research Council Page 6

Typical Equipment & Techniques for Trenching/Digging Operations

Equipment Used in Digging Operations — Tractor/Loader/Backhoe (TLB)

Figure 9. Tractor/Loader/Backhoe

4.2.6 Student Book © 2004 Propane Education & Research Council Page 7

Techniques for Trenching/Digging Operations

Locating Buried Utilities — It is the responsibility of the excavator to follow all state, local and company rules, plus regulations in locating utilities and buried facilities.

Observing Soil Conditions — Know the composition and stability of the soil where you are working. For sloping and shoring requirements, soils are categorized by OSHA in a decreasing order of stability.

Soil Classification (Type) Description

A Cohesive soil—clay, clayloam, silty clay, sandy clay

B Granular cohesionless soils—sandy and siltloam, silt, angular gravel

C Granular soils—gravel, sand solid from which water is freely seeping

Note: Stable rock and hard shale are not classified.

4.2.6 Student Book © 2004 Propane Education & Research Council Page 8

Techniques for Trenching/Digging Operations

Soil and Tool Placement — Soil removed from the excavation and tools not in use, which are above grade, shall be at least 2 feet from the edge of the excavation, unless retaining devices that are sufficient to prevent materials or equipment from falling or rolling into the excavation are used (e.g., extend shoring above trench).

Shoring — In order to reduce the risk of cave-ins, 29 CFR §1926 gives guidelines for shoring and bracing excavated holes or trenches. This is an essential safety precaution for employees getting in and out of trenches.

Sloping — Sloping an excavation is much more than just digging a hole in the ground. The purpose is to provide a safe working area for the workers in the trench. When a trench is to be sloped, the required ratio is 2 to 1 in both directions for every foot in depth.

4.2.6 Student Book © 2004 Propane Education & Research Council Page 9

Techniques for Trenching/Digging Operations

Digging Operations — Backhoes are sometimes used to dig the hole for an underground ASME tank. The operator must be knowledgeable in the techniques of backhoe operations, and know all safety precautions before operating the equipment.

Based on the measurements of the tank, an area should be marked that is 12 inches wider and 12 inches longer than the overall width and length of the tank.

The hole for the underground tank should be deep enough to allow for 2” to 4” of coarse sand to be leveled and tamped in the bottom as the tank’s foundation.

4.2.6 Student Book © 2004 Propane Education & Research Council Pages 9 & 10

Identifying Typical Backfilling Operations

After the underground ASME tank has been set and leveled in the hole and a corrosion protection system installed (if needed), the backfilling may be done.

Backfill must be free of rocks and abrasives, as they can damage the tank coating.

Figure 10 illustrates an underground ASME tank after backfill. Note how backfill is downgraded from the dome.

Figure 10. Typical Small Underground Tank Installation

4.2.6 Student Book © 2004 Propane Education & Research Council Pages 11 - 13

Time to See If You Got the Key Points of This Module…

• Complete the Review on pages 11 & 12.

• See if you are ready for the Certification Exam by checking off the performance criteria on page 13.