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JWDD004-17 JWDD004-Halpin-v6 August 4, 2005 12:4
Chapter 17
Safety
Safety in Trenches
The Need
Even though heavy construction equipment such as a crane or backhoe
excavators is used to perform the task of pipe laying in the trench, workers are
required to be inside the trench to guide the excavation, pipe laying, and final
alignment. Work place safety has become a major concern in the construction
industry over the past few decades, and trench cave-ins have caused serious
and often fatal injuries to workers in the United States. It has become of
crucial importance to implement the use of new technologies to prevent
accidents in trench excavation and pipe installation.
Diverse approaches such as shoring, shielding, and sloping have been
Pipe manipulator mounted on
the excavator.
applied to protect workers from cave-ins in trenching and pipe laying
operations. However, even when support systems are used, the danger of
cave-ins still exist due to the nature of the soil and unexpected circumstances.
The Construction Automation and Robotics Laboratory (CARL) at North
Overview of pipe manipulator.
Carolina State University has developed an alternative which involves
advanced new technology: the prototype robotic excavation and pipe
installation system called Pipeman.
Layout of the robotic trenching and pipe installation system
(Huang & Bernold, 1993).
The Technology
The basic Pipeman concept consists of a 3-D spatial positioning system (SPS), which is
interfaced with an excavator to provide the location of the excavator and a beam laser. A
pipe manipulator prototype is attached to the bucket of the excavator, which is capable of
handling pipes of various sizes. A beam laser is also used to help the operator align pipes.
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17.1 Need for Safe Practice 291
Integration of SPS with a CAD system will update the excavator position in real-time and
provide an as-built drawing of pipe laying.
The main components of the concept are the man-machine interface, actuation system,
laser beam and feedback system. The man-machine interface is used to keep the operator
in a safe area and allow him to guide the Pipeman intelligently, while Pipeman works in a
hazardous environment.
17.1 NEED FOR SAFE PRACTICE
A disabling injury or fatal accident on the job site has negative impact on operations at
many levels. Accidents cost money and affect worker morale. Because of the type of work
involved in construction, many dangers exist both for the workers and for the public. For
this reason, the subject of safety offers one area of noncontroversial mutual interest between
management and the work force. The necessity of safe operations and of protecting and
conserving lives by preventing accidents is understood by all.
Although the fatality rate in construction has been reduced within recent years, the
improvement in safety record achieved by the construction industry still lags seriously
behind that achieved in other hazardous industries. The annual number of fatalities in the
construction industry in 2003 exceeded the number of combat deaths during the first 18
months of armed conflict in Iraq (period 2003Ð2004). Construction is a dangerous business.
It is the contractorÕs responsibility to see that everything possible is done to provide
a safe working environment for the work force and the public in general. The factors that
motivate safe practices at the job site are generally identified as follows:
1. Humanitarian concerns
2. Economic costs and benefits
3. Legal and regulatory considerations
Society has taken the position that because of the high health and accident potential intrinsic
to the construction industry, the contractor must accept the liabilities associated with this
hazardous environment and make an appropriate commitment to safe practice and accident
prevention.
17.2 HUMANITARIAN CONCERNS
It is normally accepted that day-to-day living has intrinsic risks that may result in members
of the society being subjected to mental and physical hardship. One of the functions of
society is to minimize pain and suffering. Particularly at the level of the work site, society
has defined the principle that the employer is responsible for providing a safe environment
for the work force. This is based on humanitarian concern. If, for instance, a worker loses
a leg because of a job-related accident and is confined to a wheelchair, the worker is, in
a sense, a casualty of the workplace. Through his desire to be a participating member of
society and support members of his family, the worker is injured. Society has traditionally
shouldered the responsibility for this limitation on a workerÕs abilities. Over the past 120
years, the principle of employer liability for death and injury resulting from accidents or
health hazards occurring at the workplace has been firmly established in common law. The
courts have further charged the employer with the following five responsibilities1:
1. To provide a reasonably safe workplace
1 Lee E. Knack, in Handbook of Construction Management and Organization, Bonny and Frein (eds.), Van
Nostrand Reinhold, New York, 1973, Chapter 25.
292 Chapter 17 Safety
2. To provide reasonably safe appliances, tools, and equipment
3. To use reasonable care in selecting employees
4. To enforce reasonable safety rules
5. To provide reasonable instructions regarding the dangers of employment
Mandatory requirements for the employer to make formal provision for injuries and deaths
on the job resulted in the enactment of workmenÕs compensation laws in all fifty states
during the first half of the twentieth century.
In 1884, Germany enacted the first workmenÕs compensation act, followed by Austria
in 1887 and England in 1897. The U.S. federal government passed the first American compensation
act in 1908 covering government employees. Following several legal battles, the
Supreme Court, in 1917, declared that states could enact and enforce compulsory WorkmenÕs
Compensation Laws under their power to provide for the public health, safety, and
welfare.
17.3 ECONOMIC COSTS AND BENEFITS
Safety costs can be broken into three categories as follows:
1. Direct cost of previous accidents
a. Insurance premiums and ratings
b. Mandatory accident prevention methods
c. Records, safety personnel
2. Direct cost of each accident occurrence
a. Delay to project
b. Uninsured damages
3. Indirect cost
a. Investigation
b. Loss of skilled workers
c. Loss of equipment
d. Lost production
Direct costs from previous accidents come primarily in the form of insurance premiums,
which have a significant effect on a contractorÕs operating expense. WorkmenÕs
compensation and liability insurance premiums can be calculated using either manual or
merit rating systems. Manual rating is based on the past losses of the industry as a whole.
The premium rate for compensation is normally set by the individual state Compensation
Rating Bureaus. Many states are guided by or actually have their rates set by the National
Council on Compensation Insurance (NCCI). The premium rates are based on factors such
as classification of operations, rates of pay, the frequency and severity of accidents in a
particular classification, increases in the cost of cases, and the attitudes of various industrial
compensation commissions. The rates as set and approved by each state insurance
commissioner are known as the manual (standard) rates. These manual rates are published
periodically in the Engineering News Record (ENR) Quarterly Cost Roundup issues. A
listing of some of the rates as reported in the R. S. Means Building Construction Cost Data
is given in Figure 17.1.
The merit rating system bases premiums on a particular companyÕs safety record.
High-risk (high-accident-rated) companies are therefore penalized with higher premiums
than those paid by companies with lowaccident rates. In thisway, a good safety program can
result in substantial financial savings to a company. Higher returns on jobs can be realized,
and the ability to bid lower and win more jobs is greatly enhanced.
Figure 17.1 Compensation insurance base rates for construction workers (selected states and crafts).
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294 Chapter 17 Safety
Once the premiums reach a value of $1000, the contractor is eligible for a merit system
rating. That is, the cost of the premium will be individually calculated with the safety record
of the company being the critical consideration. Under the merit system, there are two basic
methods utilized to incorporate the safety record into the final cost of the premium. These
are referred to as the experience rating and retrospective rating methods.
Most insurance carriers use the experience rating method, which is based on the companyÕs
record for the past 3 years not including the most recent preceding year. In this
system, an experience modification rate is multiplied by the manual rate to establish the
premium for a given firm. Data on losses, the actual project being insured, and other variables
are considered in deriving the experience modification rate (EMR). If the company
has an experience modification rate of 75%, it will pay only 75% of the manual premium.
Good experience ratings (EMRs) can lead to significant savings. Clough and Sears (Wiley,
1994) illustrate this with the following example:
Assume that a building contractor does an annual volume of $10 million worth of work.
Considering a typical amount of subcontracting and the cost of materials, this general
contractorÕs annual payroll will be of the order of magnitude of $2.5 million. If his present
workmenÕs compensation rate averages about 8%, his annual premium cost will be about
$200,000. Now assume that an effective accident prevention program results in an experience
modification rate (EMR) of 0.7. This will result in a reduction of the annual premium cost to
about $140,000 for this contractor. Annual savings on the order of $60,000 are thereby
realized on the cost of this one insurance coverage alone.
Retrospective rating is somewhat like self-insurance. It is basically the same as experience
rating except for one point. It utilizes the loss record of the contractor for the previous
year or other defined retrospective period to compute the premium. This can raise or lower
the premium cost based on performance during the retrospective period. The starting point
or basis for this method is again the manual premium. A percentage (usually 20%) of the
standard premium resulting from applying the experience modification factor to the manual
rate is used to obtain the basic premium. The retrospective rate is then calculated as
Retrospective rate = (Tax multiplier) ¡Ñ {Basic premium + [(Incurred loss)
¡Ñ (Loss conversion factor)]}
The incurred loss is the amount paid out to settle claims over the retrospective period. The
loss conversion factor is a percentage loading used to weight the incurred losses to cover
general claims investigation and adjustment expenses. The tax multiplier covers premium
taxes that must be paid to the state. If the data for a given company are as follows:
Manual premium $25,000
Experience modification rate 0.75
(25% credit)
then
Standard premium = 0.75($25,000) = $18,750
Basic premium @ 20% of standard = 0.20($18,750) = $3750
Loss conversion factor = 1.135 (derived from experience)
Tax multiplier = 1.03 (based on state tax)
Incurred losses = $10,000
Then
Retrospective premium = 1.03[3750 + (1.135 ¡Ñ $10,000)]
= $15,553
17.4 Uninsured Accident Costs 295
This is a nice savings over the standard premium of $18,750 and provides the contractor
with a clear incentive to minimize the incurred losses. By so doing, the contractor can expect
a large premium rebate at the end of the year.
17.4 UNINSURED ACCIDENT COSTS
In addition to the cost of insurance premiums, additional direct costs for things such as the
salary of the safety engineer and his staff as well as costs associated with the implementation
of a good safety program can be identified. The precise amount of the costs associated with
other safety cost categories is more difficult to assess, and these costs can be thought of
as additional uninsured costs resulting from accidents. Typical uninsured costs associated
with an accident are shown in Table 17.1.
Although varying slightly from source to source, hidden losses of this variety have been
estimated to be as much as nine times the amount spent on comprehensive insurance. In
addition to the costs noted in Table 17.1, another cost is that of paying an injured employee
to show up for work even if he cannot perform at his best. This is common practice for
minor injuries. This is done to avoid recording a lost time accident, which might impact
the insurance premium. While it is very common to return injured workers to work, it is
Table 17.1 Uninsured Costs
Injuries Associated Costs
1. First-aid expenses
2. Transportation costs
3. Cost of investigations
4. Cost of processing reports
1. Difference between actual losses and amount recovered
2. Rental of equipment to replace damaged equipment
3. Surplus workers for replacement of injured workmen
4. Wages or other benefits paid to disabled workers
5. Overhead costs while production is stopped
6. Loss of bonus or payment of forfeiture of delays
Wage Losses Off the Job Accidents
1. Idle time of workers
whose work is interrupted
2. Man-hours spent in
cleaning up accident area
3. Time spent repairing
damaged equipment
4. Time lost by workers
receiving first aid
1. Cost of medical services
2. Time spent on injured workersÕ welfare
3. Loss of skill and experience
4. Training replacement worker
5. Decreased production of replacement
6. Benefits paid to injured worker or dependents
Production Losses Intangibles
1. Product spoiled by
accident
2. Loss of skill and
experience
3. Lowered production of
worker replacement
4. Idle machine time
1. Lowered employee morale
2. Increased labor conflict
3. Unfavorable public relations
Source: From Lee E. Knack, in Handbook of Construction Management and Organization, Bonny and Frein
(eds.), Van Nostrand Reinhold, New York, 1973, Chapter 25.
296 Chapter 17 Safety
important that they not be returned to work too soon to avoid their being reinjured or injured
more seriously.
The following situation illustrates the additional losses resulting from hidden costs. At
a large industrial construction site, the survey party chief was on the way to the office to
get a set of plans. The survey crew was to lay out four machine foundations that morning.
The wooden walkway beneath the party chief collapsed. Due to the confusion resulting
from the accident, work activity on the entire site was impacted. The party chief was in
the hospital for 5 weeks with a shattered pelvis. Another party chief who was unfamiliar
with the site was assigned to the surveying crew. As a result, the four machine foundations
were constructed 2 ft farther west than called for in the plans. After this was discovered,
six laborers worked for 20 hours removing the reinforced concrete. The survey crew of
four spent another 5 hours laying out the foundations. Four carpenters worked 20 more
hours preparing new forms. Five more hours were required for the ironworkers to place the
steel reinforcement. The total indirect cost was approximately $5000. Although this activity
was not on the critical path, if it had been, liquidated damages might have been charged
to the contractor. Still, the accident resulted in costs amounting to one weekÕs pay for the
employees affected and the cost of material that had to be replaced.
17.5 FEDERAL LEGISLATION AND REGULATION
The federal government implemented a formal program of mandatory safety practices in
1969 with the passage of the Construction Safety Act as an amendment to the Contract
Work Hours Standard Act. This legislation requires contractorsworking on federally funded
projects to meet certain requirements to protect the worker against health and accident hazards.
In addition, certain reporting and training provisions were established. This program
of required procedures has been referred to as a physical approach to achieving safety. That
is, regulations are prescribed that are designed to minimize the possibility of an unsafe
condition arising. A typical physical measure of this type is the requirement to install guard
rails around all open floors of a multistory building during construction. Guard rails are
needed anytime there is change in elevation of 6 feet and the worker is not protected by a
personnel fall arrest system, warning line, or warning attendant (used to watch workers and
warn them if theyÕre too close to falling).
Furthermore, physical measures are implemented to minimize injury in the event of
an accident. An example of this is the requirement to wear a safety belt when working
with high steel, and the installati...
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