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 1
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
Page 2
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
Pages 2 & 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 3
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)
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.
Figure 4. Consult the Manufacturer’s
Manual for Your Equipment
4.2.6 Student Book  © 2004 Propane Education & Research Council
Page 4
Typical Equipment & Techniques for Trenching/Digging Operations
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.
Figure 5. Handlebar Trencher
4.2.6 Student Book  © 2004 Propane Education & Research Council
Page 4
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 5
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 6
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 7
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 8
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
Page
9
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 9 & 10
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.
4.2.6 Student Book  © 2004 Propane Education & Research Council
Pages 11 - 13