Page 222 - Water Engineering Hydraulics, Distribution and Treatment

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Chapter 6
Water Distribution Systems: Components, Design, and Operation
Figure 6.18 Area of incident.

(9.45 m) long. One end was about 5 ft (1.52 m) wide and the the other section a 90-degree angle section or “L” joint. The
other end, where the incident occurred, was approximately straight piece weighed about 10 lb (4.54 kg) and the “L” joint
12 ft (3.66 m) wide. The trench depth was 6 ft (1.83 m) at weighed between 30 and 40 lb (14 and 18 kg).
the edges going down to 7 ft (2.13 m) where the pipe was The victim and apprentice plumber were in the trench
located. About 6–8 in. (150–200 mm) of water was on the trying to assemble the 3 ft (0.91 m) section to the 90-degree
bottom of the trench (see Fig. 6.18). There was no shoring, “L” joint but there was not enough room to work and there
shielding, or sloping of the trench walls. was still a large amount (6–8 in. or 150–200 mm) of water
An employee (hereinafter referred to as “operator”) of in the hole. They decided it would be easier to work on
the shopping center operated the backhoe to dig the trench. connecting the two pieces outside the trench and then return
He had been with the firm for approximately 13 years and the assembled unit to the trench to connect to the other pipe
was in charge of the safety of personnel, property, and the lines. To get the pipes out, they decided to place them in the
public for the mall. He had training on operating backhoes bucket and have them raised out of the trench.
prior to employment with the firm and had operated the same The bucket of the backhoe was positioned about 4 ft
model of backhoe on jobs at the shopping center with the (1.4 m) down in the trench close to the pipe line. The victim
plumbing contractor. However, operating a backhoe was not was facing east about 1 ft directly to the left and in the line
part of his regular duties. The operator had requested this of contact with the bucket. The apprentice plumber was also
particular model of backhoe be used, instead of the backhoe to the left of the bucket but out of its reach and was facing
the plumbing company owned. According to the operator, west looking at the victim.
the victim asked him to operate the backhoe because he was The “L” pipe had just been placed in the bucket by
more familiar with that particular model. the victim and apprentice plumber when, unexpectedly, the
The backhoe was a farm tractor type, all-purpose
backhoe/loader with rubber tires and a 75 HP (56 kW),
diesel, four-cylinder engine. It had a general purpose 18 in.
(457 mm) bucket weighing 255 lb (116 kg) with foot con-
trols to swing it left (left throttle) and right (right throttle).
Hand levers raised, lowered, and extended the two-part 430
lb (195 kg) boom with the bucket attached at the end (see
Fig. 6.19) to a maximum of 25.5 ft (7.77 m). It had outrig-
gers for stabilization, which were in position on the day of
the incident. The backhoe was positioned about 4 ft (1.22 m)
from the edge of the trench on the asphalt parking lot behind
the curb. The boom with attached bucket was extended and
angled over and down into the trench. The operator, if sitting
in the seat of the backhoe, could not see activity down in the
trench.
To repair the leak, the victim and apprentice plumber had
to remove two sections of the old pipe and install new pipe.
The pipe sections were cast iron and were 10 in. (250 mm)
in diameter with the straight section 3 ft (0.91 m) long and Figure 6.19 Bucket and boom of backhoe.