Constructability And The Safe Design Principles Construction Essay

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Constructability & Safe Design Principles serves as a preliminary process to provide Parsons Engineers, and the Construction Management Engineers an easy methodology to identify constructability issues & hazards that are likely to arise in the erection process and provide reasonable design features to preclude potential peril in the design phase of the Arabian Canal Project Infrastructure. The process provides practical information to Parsons Design Engineers to assist them in identifying constructability issues & hazards of equipment and systems used in the construction of the Arabian Canal Project Infrastructure. It offers practical principles that can be applied to control additional constructability issues & hazards found on the building site, in structural components, and from materials, processes, and procedures employed during construction and maintenance. This process is for developing the skills of Parsons Engineers to control many kinds of constructability issues & hazards at the time of design or before work begins on site to achieve optimal constructability and safety throughout the construction process and the life cycle of the Arabian Canal Project Infrastructure.

International studies have concluded that approximately sixty (60%) percent of all fatal accidents in construction arise from faulty design or insufficient planning. While the exact percentage remains the subject of debate and discussion, a number of this magnitude challenges those who manage the process of design to save lives and money simply by application of improved engineering practices. Such perspective should be a revelation to Parsons Engineers who are accustomed to view the majority of accidents in the construction industry as attributable to the routine chaos of the construction site. To do so would focus more on prevention than ever before. The objective of this process is to develop and/or expand engineering principles of constructability & safer design for construction and the life cycle of the Arabian Canal Project Infrastructure. To accomplish this task we shall draw from four pioneering approaches to constructability & safer design. These approaches which form the cornerstone of modern system safety engineering principles are the following:

Eliminate the hazard if possible, or;

Provide guarding to prevent contact with the hazard, and;

Provide safety factors to minimize the hazard, and;

Provide redundancy to confine the hazard.

All four applications necessarily involve highly focused Parsons Engineers. Though these principles have been extended, there is still no methodology to simplify these principles and incorporate them into a simple methodology.

Start of the process develops methodology for identifying constructability issues & hazards then matching the issue or hazard with design features and/or safety appliances for the prevention of the hazard. This will highlight the role of the Parsons Engineer as a designer. When the Parsons Engineer places emphasis on constructability & hazard prevention by designing out the hazards inherent to construction processes, products, or facilities, the circumstances that produce construction interferences & injuries will be drastically reduced.

The second section provides the Parsons Engineer with a system for identifying hazards with an insight into the nature of hazards and guidance that categorizes the hazards into manageable groups. Specific identification of the different types of hazards in the design stage streamlines the hazard elimination process by providing guidelines to determine general control measures. This process will provide Parsons Engineers with easy principles of system safety adaptable to design and constructability that ensure for the elimination and control of hazards. Then it will provide a method to quantify the ability of design improvements to prevent injury, death, and damage in terms of reliability.

For instance, before a construction project even begins, the construction manager faces the potential constructability issues and hazards of faulty design by the architect, defective design of the equipment that must be used, and hazards within the construction site or property. To successfully control constructability issues and hazards during the project, these obstacles and hazards must be identified and addressed during design and planning stages. This process distills system safety methodology into five principles that focus on hazard identification, isolation, and control through constructability, innovative technology and applied science. A design matrix provides a check sheet to ensure potential loss exposures have been identified and controlled before the design has left the drafting room. Practical application of this method eliminates or controls potential constructability issues and hazards.

In a world of exponential increases in technology, Parsons Engineers have new and exciting options available to them. Parsons Engineers who can "think outside the box" will find many opportunities to re-engineer products using new materials and informational devices in a way that produces a constructible and safer product or process.

Constructability & Safety In-Design Compliance Procedure

Engineering Department Procedure "Constructability & Safety In-Design Compliance Program

Parsons' Constructability & Safety-in-Design (CSID) program is an ongoing implementation and confirmation effort relating to a project's safety requirements. Parsons CSID approach evaluates and resolves hazard analysis relating to the mitigation of personnel and public hazards in a facility's construction and operation, adherence to code requirements, and beneficial safe design practices.

The Parsons CSID process begins with implementing the "Constructability & Safety-In-Design Compliance Procedure" and supported by the Parsons "Constructability & Safety In Design Process Guide". The Parsons comprehensive "Constructability & Design for Safety Training Process" ensures the project staff fully understands the CSID processes and continually works to ensure complete implementation.

The CSID review committee will be tasked with completing the Constructability reviews. The Parsons Constructability review is a review of the plans and specifications to check for build ability and bid ability. When reviewing for build ability, Parsons checks for the completeness of the drawings. This includes a cross-check between the various disciplines (electrical, mechanical, architectural, structural, plumbing, civil, and landscaping, etc.) to coordinate pipeline sizes & locations, power capacities, road and bridge layout and sizing, and other major components that are essential to build the infrastructure. Additionally, there may be dimensional errors in calculating radius building plots that impact structural steel, site concrete, light bollards, and landscape. Critical dimensions are reviewed to prevent building delays, bidding errors and to ensure the complete project is capable of being under written for insurability. When checking for bid ability, Parsons Constructability Review Team performs an extensive review of details, notes, sections, elevations, site plans and specifications. As in any contract, the best contract is without ambiguity, error, conflict, and leaves little to interpretation. This review crosschecks the use of detail references and confirms consistent use of building finishes to specifications and other plan details. The work product of the review is a list of comments and a marked-up set of the plans and specifications to be reviewed by the project stake holders. The list of comments is created using the Parsons Constructability Assessment Register so the list can be modified and prioritized by other team members. (It also serves as a checklist to confirm the incorporation of the comments to the documents before going to bid.)

A standard procedure to mark-up the drawings with changes is established. For example, green pen will be used to highlight question areas, orange pen will be used if the question is answered as the review continues, blue pen will be used to make corrections, and yellow pen to verify the information was input into the Constructability Assessment Register. Using this standard mark-up policy, the constructability team can clearly show all stake holders the process of how each comment was generated. Additionally, the incorporation of a change is easier to compare the marked-up sheet to the existing design.

After the plans and specifications have been marked-up, each comment will be input into the Parsons Initial Hazard Evaluation Register. The process of inputting the information is not just a clerical process, but also a "final pass" of the plans and specifications. Often additional comments are generated or questions are answered. Once the comments are inputted, the Parsons Constructability Review Team will prepare a narrative explaining the format of the comments and the general outcome of the review. The constructability report (the narratives and comments) will be forwarded to the stakeholders and a meeting scheduled to review the comments.

The opportunities to create safer workplaces are most cost effective when captured in the earliest phases of the lifecycle of designed products or processes. The most effective risk control measure - eliminating the hazard - is often cheaper and more practical to achieve at the design or planning stage, rather than making changes later in the lifecycle when the hazards become real risks to clients, users, employees and businesses. The constructability review will ensure the completed project is insurable, reduce bidder's questions, increase the likelihood of competitive bids, reduce RFI's, and change orders and delays during the bid and construction process. It is much easier and less costly to make the changes to the plans and specifications prior to bid, rather than during construction.

A constructible safe design approach results in many benefits, including:

Prevention of injury and disease,

Improved use ability of products, systems and facilities,

Improved productivity reduced costs,

Better prediction and management of production and operational costs over the lifecycle of a product,

Compliance with legislation,

Innovation, in that constructible safe design demands new thinking

Reducing over all project

Increase construction practicality,

Eliminates errors and ensures project schedule completion in a timely manner

Provides the owner and all stakeholders to have the opportunity to ensure the design is fully acceptable to their standards and expectations

Address the life cycle environmental impacts and improves the over all preservation of resources

Reduces the life cycle expenses associated with operations and maintenance

The lifecycle of a product is a key concept of sustainable and constructible safe design that provides a framework for eliminating the hazards and improving the constructability at the design stage and/or controlling the risk as the infrastructure is: constructed, installed, commissioned, used or operated, maintained, repaired, modified, de-commissioned, demolished and/or dismantled, and disposed of or recycled.

The Parsons CSID is a tool to assist designers, engineers, constructors, clients and other key stakeholders to come together to reduce construction, maintenance, repair and demolition safety risks associated with design. Parsons CSID recognizes that a design involves key considerations such as operability, aesthetics and economics with the elements of safety. It also acknowledges that a design process may be determined by many different stakeholders and/or influences. The CSID methodology aims to involve these elements and influences. By proactively considering construction, maintenance, repair and demolition issues, the CSID framework should not only help reduce the number of construction industry incidents, but also assist in improving constructability and reducing the life cycle costs associated with building the infrastructure design project.

There is a balance of responsibilities between a designer, a constructor and other relevant stakeholders, such as clients or specialist consultants. It is important that all participants highlight unusual safety risks associated with a design and required construction.

As outlined in the Parsons CSID process all those involved should:

identify the hazards presented by potential design solutions and consider the risks these hazards will generate for construction workers and others who may be affected by the construction work (e.g. members of the public);

include health and safety considerations amongst the design options so that they can avoid the hazards, reduce their impact or introduce control measures to protect those at risk where it is re a s o n a b l y practicable;

forewarn the contractor of the residual hazards that have been identified within the design and will need to be managed during the construction work. Eliminating the hazard is the first risk control that should obviously be considered. If the hazard cannot be eliminated (for example eliminating risks associated with maintenance by using aluminum/stainless steel, which requires no regular painting), risk can be minimized by using a series of steps known as the hierarchy of risk control. Including:

substituting the system of work or plant with something safer (e.g. pre-assembled equipment at ground level rather than height);

modifying the system of work or plant to make it safer (e.g. ensure attachment points for lifting, window cleaning, safety lines, etc.);

isolating the hazard (e.g. introduce restricted areas);

introducing engineering controls (e.g. prevent falls from buildings during construction/maintenance by increasing wall/edge height).

Only when the above constructible and risk control options have been exhausted should consideration (and more importantly reliance) be given to personal protective equipment (e.g. safety harnesses) or adopting administrative controls such as hazard warning signs. Design is the process of considering options. In developing and understanding these options, there is also the ability to improve safety and reduce costs. For example, the costs associated with assembling large scale scaffolding may far exceed the costs associated with alternate design and/or construction materials. Similarly, an emphasis placed on achieving a design that would be safe and efficient to erect, rather than the traditional approach of minimizing steel tonnage, did result in lower project costs. Essentially, given the opportunity to consider the design in a formal and systematic way, a smarter design results - and a smarter design invariably leads to a safer design.

The following subjects are included in this program:

Personnel life safety

Safe facility startup

Safe facility shutdown

Intrinsically safe designs

Structural integrity (e.g., seismic, wind, safe loading, equipment support, etc.)

Considerations for operating a facility safely

Parsons defines project safety requirements as internal or external (Employer) specification, government code, manual, policy, standard, and safe practice that pertains to providing safe and healthful facilities for personnel.

The Standard Industry Codes and Standards (or publishers of basic codes and standards), which pertain to safe design practices, will be utilized by the Parsons Design team. The project design team will also include requirements of the Development project objectives and goals, the requirements of Dubai Municipality and its agencies, and other specific Employer requirements or best practices.

The Project Manager and Design Manager will be responsible for coordinating and confirming the special constructability and safety requirements for the design elements for the project work. The Project Manager and Design Manager together with the QA/QC manager will verify the appropriate reviews have been performed related to Constructability & Safety In Design. The Design Manager will be responsible for establishing the Employer requirements checklists, which include safety-related industry codes/and standards and local/city code requirements. The Design Manager will also direct and coordinate the work of engineers and designers assigned to the project accomplish the Constructability & Safety In Design objectives and requirements.


This procedure describes Engineering Department policy for application of the Constructability & Safety-In-Design (CSID) Compliance Program. Engineering/design practices and principles contained in this document are intended generally to be applied to all types of facilities during each project's planning and design phase.

Constructible & Safe design practices rely on the correct use of current basic code requirements, existing design standards, client requirements, and any other known safety considerations that assist in safeguarding against unsafe conditions and help manage unsafe materials and hazardous acts causing illness or bodily harm to workers. Enhances building information modeling and enables design success related to sustainability, security, design-build, risk management, hazard mitigation, insurability and performance-based design.

Promotes team building among client, designer and contractor, emphasizing the success of the project instead of the success of the individual, thereby minimizing the commoditization of engineering.

Provides ongoing feedback from clients, users, and contractors to the design team, eliminating scope surprises.

Reduces total project costs and engineering scope creep, improving profitability.

Involves construction expertise in the design phase, identifying field issues and avoiding obstacles, unnecessary construction costs, and lawsuits.

Improves the quality of construction documents, minimizing change orders and subsequent post-construction claims.

Improves the quality of the next design, incorporating feedback from the field.

Figure : Constructability Logic Diagram



As a noun safety shall be understood to mean the condition of being safe from (or causing) harm, injury, or loss.

As a verb safety shall be understood to mean protection against failure, breakage, or accident.

Constructability & Safety In-Design Program

Parsons CSID compliance program is an ongoing implementation and confirmation effort relating to a project's constructability & safety requirements. Also included are hazard analysis resolutions relating to the mitigation of personnel hazards in a facility's operation, adherence to code requirements, and safe design practices beneficial to personnel.

The following subjects are included in this program.

Personnel life safety

Safe facility startup

Safe facility shutdown

Intrinsically safe designs

Structural integrity (e.g., seismic, wind, safe loading, equipment support, etc.)

Considerations for operating a facility safely

Owner/operation procedure supplement

Operating sufficiency/redundancy

Economic design

Ease of maintenance

Environmental compliance

Construction safety

Failure analysis (except for life safety systems)

Supplier product/safety responsibilities

Safety and Personnel Hazards

Typical safety and personnel hazards in operating facilities include, but are not limited to:




Tripping and clearance deficiencies

Structural degradation and improperly supported elements

Electrical shock

Chemical burns and fumes


Excessive sound levels

Use of, and/or exposure to, toxic construction materials (e.g., urethane and asbestos)

Toxic materials handling

Potable water contamination (e.g., sanitary sewer/process sewer)

Radiation - nuclear

Magnetic fields

Use of microwaves

Inadequate lighting (eyestrain and darkness)

Ergonomic deficiencies (e.g., carpal tunnel syndrome and muscular strain)

Materials handling (e.g., overheads, conveyors)

Moving machinery parts (e.g. guards, over speed, vibration, emergency stop/lockout)

Hazardous spills

Moving objects (obstructed vision)

Inadequacy of alarms/communication systems

Unanticipated structural loading (e.g. large number of people on platforms)

Hazard Analysis

A hazard analysis is generally intended to identify and examine hazards during all phases of design, construction, and operations, as applicable to the requirements of each project. This analysis includes hazards and operability (HAZOP) studies, "what-if" evaluations, failure mode and effects analyses (FMEA), and event-tree and fault-tree analyses. Hazard analysis is not a function of the Engineering Department but is handled by others. On some projects, hazard analysis is performed by the client.

Constructability & Safety Systems

Typical Constructability & safety systems include, but are not limited to, the following three categories.

Monitoring Systems

Fire and smoke detection alarms

Toxic material sensors and alarms

Critical sampling systems

Constructability & Safety Device Systems (permanent and in-place)

Safe electrical voltages near personnel

Explosive protection

Protective material coverings

Adequate exiting and door hardware


Fall protection

Ladder clearances and cages

Stair handrails, platform handrails, and toe plates

Operability of valves

Machinery guards

Safety color coding


Emergency stop switches

Equipment-keyed lockout switches

Emergency Protection Systems (activated by an incident)

Eyewash and safety-shower stations

Emergency/exit lighting

Emergency communications

Emergency alarms

Fire sprinklers

Emergency exit facilitation devices (e.g., slides)

Electrical circuit protection (e.g., circuit breakers and fuses)

Constructability & Safety In-Design Process Guide

Constructability and Safe Design Concepts

Specific aims and goals in the beginning of this process address the theories and methodology of constructability, hazard identification and the development of design features to eliminate the obstacles and hazard and/or minimize the probability of constructability and injury or damage failure mode. Constructability and safety engineering should include the process of systematically controlling constructability issues and hazards through design considerations or with the use of safety appliances.

Principle One: Definition of a Hazard and Constructability

To begin to address constructability & safer design principles in construction and the life of the Arabian Canal Project Infrastructure, one must first understand the actual nature of constructability and hazards. A specific definition of constructability and hazards provides the Parsons Engineer with a basis to develop a methodology for planning and evaluating the construction and the life cycle of the Arabian Canal Project Infrastructure process for constructability and safety ensuring for design of constructible, safe systems and equipment. The undertaking of such construction design principles leads to safe operation of a completed facility.

What a hazard is in practical terms:

Definition: A hazard is an unsafe physical condition that is always in one of three modes- Dormant/Latent (unable to cause harm), Armed (can cause harm), Active (causing injury, death, and/or damage by releasing unwanted energy, substances, biological agents, and or defective computations from computer software.

In greater detail, a dormant/latent hazard is a design defect that is susceptible to a failure mode. Foreseeable misuse should also be considered (a kitchen chair may be used to stand on to reach upper cabinets and needs to be sturdy enough to prevent collapse.)

The armed hazard is created by a change of circumstances and is ready to cause harm (the chair may have a big knot on one leg). The active hazard is an armed hazard triggered into action (when the chair is stepped on the knot cannot support the additional load and the chair leg collapses, causing a fall.)

Definition: Constructability is "the optimum use of construction knowledge and experience in planning, design, and procurement and field operations to achieve the overall project objectives".

The basis of constructability concept is that experienced construction personnel need to be involved with the project from the earliest stages to ensure that the construction focus and their experience can properly influence the owners, planners, and designers, as well as material suppliers. This does not necessarily mean that the design or project objectives should be changed to meet constructability only from a cost standpoint. Constructability should be used as a design consideration, so that optimum results provide the best of both worlds.

Parsons approach to the Arabian Canal Project Infrastructure Design will emphasize constructability with various characteristics and be implemented as design progresses.

Parsons Design and construction managers are committed to the cost effectiveness of the whole project. They recognize the high cost influence of early project decisions.

Parsons managers use constructability as a major tool in meeting project objectives concerning quality, cost and schedules.

Parsons managers bring construction aboard early. This means using experienced personnel who have a full understanding of how a project is planned and built.

Parsons Designers are receptive to improving constructability. They think constructability, request construction input freely, and evaluate that input objectively.

Early constructability efforts result in a significant payback to the project. Industry research has cited cost reductions of between 6 and 23 percent, benefit/cost ratios of up to 10:1, and large schedule reductions. The intangible benefits are as important as the quantitative benefits and must be recognized accordingly. These include; more accurate schedules, increased productivity, improved sequence of construction, enhanced quality, decreased maintenance, and a safer job.

Parsons will provide input to the planning and design from the standpoint of project intent, constructability, safety, operation and maintenance. This will be accomplished through field reconnaissance with designers and reviews of design documents at various stages of development. Obtaining feedback from maintenance personnel at this point is very important, since they ultimately live with the finished product and are aware of previous construction deficiencies. The reviews will be scheduled during both the Conceptual Development and the Design phases.

Principle Two: Establish a Standard of Constructability and Safe Design

Constructability and Safety must be converted into a powerful design priority and overriding planning concern to be effective. It must rely primarily on the physical elimination of each construction obstacle and hazard, rather than upon human performance, which is variable and cannot be programmed, to avoid the obstacle or hazard. Through the evaluation and close scrutiny of each activity, task or phase of the construction process we are able to identify possible failure modes to identify hazardous conditions.

A well-known tenet of safety engineering states "Any hazard that has the potential for serious injury or death is always unreasonable and always unacceptable if reasonable design features and/or the use of safety appliances are available to prevent the hazard." The key to successful safety engineering is to identify and design out as many hazards as possible. When this tenet is applied as a design standard, it becomes a routine expectation to design out hazards, thus changing a dangerous facility, product or service into a safer one.

The identification of construction obstacles and hazards is the basic building block to ensure for a safe construction and operation during the life cycle of the Arabian Canal Project Infrastructure. Often the same construction obstacle or hazard that has been causing injury, damage, or down time surfaces uncontrolled on multiple occasions. Falling loads due to two blocking were recurring hazards on construction sites for many years. This trend stopped when anti-two blocking devices were installed by manufacturers on all new cranes and retrofitted onto most cranes in the field. By relying on our past experiences, "remembering backwards" is not all that difficult to begin to control construction obstacles and hazards.

Principle Three: Categorizing the Hazard

Hazard Source

The third step in hazard identification is to determine which of the following seven categories contains the source of the hazard:

Hazard Source

Natural Environment




Radiant Energy


Automated Systems

Artificial Intelligence

Now the hazard can be binned into a convenient box or boxes. Each of these boxes contains just a few examples that serve as a starting point for the Parsons Engineer to begin to focus on the nature of the hazard.

These topics are meant to be a starting point to develop additional listings for failure modes. It is important to note that hazard categories may overlap or fall into one or more groups. It is common to encounter a hazard that contains simultaneous natural, mechanical, and chemical properties. In these cases, specific hazards should be broken down into as many individual properties as possible.

Natural Environment

The first box is our natural environment. The laws of gravity cannot be repealed, nor can the weather be programmed or the ocean drained. The following are a few hazard source possibilities that the Parsons Engineer must contend with in the natural environment.

Natural Environment


Falls same level

Fall from elevation

Falling objects







Unstable surfaces






Change in Altitude



Visibility (fog, etc.)



Limitations on Human Performance

Structural/Mechanical Hazards

The second box delineates mechanical hazards. As engineers we must consider their mechanical advantage, but also their possible danger.

Structural/Mechanical Hazards


Lack of Traction

Unstable Surfaces













Pinch Point





Structural Failure


Whole Body


Reynaud's Phenomenon [white fingers]



Hydraulic Forces










Blind Zone

Electrical Hazards

The third box lists electrical hazards. For all its advantages, electricity is a power source that is silently conveyed and can cause harm.

Electrical Hazards

Voltage, Amperage




A/C Frequency

Direct Current

Spark/ Arcs


Chemical Hazards

The fourth box lists chemical hazards, a real Pandora's Box of toxic substances that has many potential dangers in a number of forms. To begin this analysis the following clues should be a helpful approach:

Chemical Hazards

Combustion- Fire


Toxic Substance


Fumes/ Vapors



Exothermic (hot)

Endothermic (cold)


Hydrogen Embitterment

Radiant Energy Hazards

The fifth box contains radiant energy hazards. This short list is a starting point:

Radiant energy hazards




Radio Frequency



Biological Hazards

The sixth box contains a list of biological hazards that threaten our health and can be life taking. These can be classified in seven compartments:

Biological hazards









Automated Systems Hazards

The seventh box contains automated systems hazards caused by faulty computer software. While the advantages of computers are infinite, they are capable of error.

Automated systems hazards

Program Error

Technical Malfunction

The seven categories of hazards as described above have been listed to spur the Parsons Engineer to fully understand the nature of hazards as being easily segregated into seven logical categories. Once the hazards are isolated it becomes easier to begin a systematic evaluation of possible controls.

Principle Four: The Safe Design Hierarchy to Physically Control Hazards

The following engineering hierarchy of controlling hazards has become the accepted sequence of evaluating with and controlling recognized hazards:

Elimination of the hazard;

Guarding to prevent the hazard from causing harm;

Including safety factors to minimize the hazard;

Using redundancy for a group of parallel safeguards requires them all to be breached before a harm-causing failure mode occurs;

Using reliability to mathematically calculate the qualitative numerical probability of eliminating or minimizing a harm-causing failure mode.

As projects become more complex and sophisticated, constructability and safety in design must be addressed with the same attention to technical detail as is applied to the engineering of these projects. The project critical path should be highlighted at those points where construction obstacles and hazards have been identified in order to highlight potential problem areas. For the construction obstacles and hazards to be eliminated, the entire engineering process needs to be examined in this fashion. Listing hazards in the critical path forces the Parsons Engineer to consider itemized alternatives. This fact leads to the need to apply a construction and safety in design approach. System safety relies heavily upon the additional provision for safety factors and redundancy in addition to hazard elimination and guarding. It is in this manner that foreseeable error is overcome.

To achieve zero-injury, damage, loss of completion scheduling the reliance upon behavior modification to ensure for error-free human performance becomes unrealistic. The age-old byline of human factors psychologists, "To err is human, to forgive design" has proved time and again to be a sound philosophy supporting the concept that the elimination of error-provocative circumstances is the basic reasons for system safety. "Safety factors" can be easily explained by the example of a bridge with a ten-ton load limit that is designed to sustain 30 tons, thus allowing for foreseeable misuse. Closer to the safety of construction equipment is an example of a questionable safety factor. Cranes are generally rated at a capability that is 85% of the tipping load at any radius. By industrial standards, this is a rather thin margin. In some cranes, rated capacity is only 85% of the structural design of the telescoping boom, which is far less than the tipping load. In such a circumstance, the consequences of an overload would not be a crane upset but a structural collapse of the boom.

"Redundancy" is more than one safeguard, each of which must fail before the system experiences actual failure mode. A good example is the fuel system on a military helicopter, which has several fuel tanks and a number of fuel lines. In the event of enemy bullets piercing the fuel tank, it is self-sealing to stop leaks. If a fuel line is broken, both ends have automatic shut-off, as fuel has several other routes through different lines to the engine. "Reliability" is no more than a numerical confidence rating, such as a failure mode that may fail one time in one thousand cycles. The big guess is WHEN it fails. If it fails on the first cycle, it is chancy that 999 successes will follow. Reliability is the judgment to quantify a system's ability to succeed, and is not a method of control. This function attempts to take guesswork out of the hazard prevention methods of an entire project.

Each of these four categories of engineering controls briefly addresses various design choices to achieve a safe design with an expectation of near zero harm-causing failure modes. The Parsons Engineer is encouraged to expand the listing in each of the four headings to accommodate a specific circumstance.

Construction Obstacle and Hazard Elimination

Designing out the construction obstacles and hazards by planning and accurate identification.

Substitution of safer machinery.

Relocation of dangerous facilities (such as power lines or other utilities) from the construction site. Some safety appliances, such as an overpressure relief valve on a pressure vessel or an air compressor, can entirely eliminate the hazard, as long as they work.

Provision of design criteria to suppliers of structural components to ensure for constructability and safe assembly at the construction site.

Conceptualize the project, understand its problems, and provide thoughtful feedback to the designers

Constructability and safety in design issues concerning scope and design will be recognized and addressed up front, so that a quality set of plans and specifications are produced.

The early active involvement of the Parsons Construction Representatives will also provide them insight into the design intent. This knowledge will be beneficial during the later construction stage when "minor" field changes are requested by the contractor.

The project team should meet to discuss constructability issues throughout the planning/design process.

During the development of the Project design phases a concerted effort will be made to identify specific constructability items and determine their impact on the conceptual design.

Guard the Hazard

This category includes safety appliances to overcome foreseeable Operator/user error. Examples of these include anti-two blocking devices and load measuring indicators, which are designed to intercede, safe space clearance devices, and insulated links for cranes.

Establish barricades around any danger zones to eliminate hazardous conflict between equipment and existing facilities.

Provide automatic interlocks that will disarm the hazard for service and maintenance functions.

Provide detection systems that audibly and visually warn of a changing circumstance and will intercede before the hazard becomes active and produces a harm-causing failure mode.

Safety Factors

Raise the structural strengths above the foreseeable misuse and wear limits to reduce failure mode occurrences.

Reduce exposure to toxic materials.

Ensure that the structural design is well above the rated capacity in the event of an unintended overload. (Bridge design should be able to withstand foreseeable excessive weight vehicles, even those with posted weight limits for autos, and the likely exposure to heavy trucks, cement, and ready mix.)

Ensure that toxic limits for toxic radiation, gas, vapors, and dust are well below health hazards.


A combination of safeguards is able to achieve an effective hazard control network.

Install design barriers in parallel so that each one must fail sequentially like a row of dominoes before the hazard can cause a harm-producing failure mode. As an example an insulated link of a crane's hoist will protect the individual guiding or touching the load (such as a steel beam), but will not protect the individual touching the crane's outrigger. A proximity warning device can audibly warn of an adjacent power line and alert the crane operator to stop boom movement and avoid touching the power line. The proximity alarm becomes a redundant safeguard. Additionally, workers should be trained avoid touching the load or crane upon hearing the alarm. The combination of the proximity alarm, insulated link, and designated spotter provide reasonable reliability of avoiding unintentional crane power line contact.

Ensure that each barrier in concert with the other barriers covers the entire spectrum of failure modes inherent to the specific equipment, structural and/or construction method used at the work site.


The concept that safety is everybody's business has made it nobody's specific responsibility and has far too often become the road to failure. Briefly, system safety engineering must be supported by reliability studies, and include the following concepts: a life-cycle concern unaffected by organizational structure, application of appropriate engineering disciplines, and a technical information-gathering function for decision-makers. Reliability provides an overview to gauge the efficacy of hazard elimination, guarding, safety factors and redundancy by making a quantitative assessment of the likelihood of a construction or operational phase failure mode.

To establish a measure of proof that the above four design options will in fact eliminate or minimize hazardous failure modes, the Parsons Engineer has the option of conducting a reliability analysis. Though considered to be tedious or abstract, reliability calculations are a necessary part of successful system safety. When completed, the reliability analysis provides an assessment of the accuracy and efficiency of the controls incorporated into the design.

This process is conducted at the end of the engineering hazard control hierarchy and provides probabilities of failure of each of the identified harm-producing failure modes.

It provides a quantitative analysis of how safe the life cycle of a project can be made.

It defines the actual peril that can arise from the specific hazard

It recognizes that machine-dependant safeguards, as warning labels, verbal instructions, and training processes are not failsafe because of behavior-induced error. An accurate reliability calculation can help define and isolate each specific error-producing factor. With safe design, training remains very important, as it ensures that the operator/user is aware of the hazard, the peril and how the design feature or appliance is provided for their safety. The previously mentioned methods of controlling hazards: elimination, guarding, safety factors, and redundancy are applied to establish a reliable, fail-safe system. The reliability of each hazard control chosen should be analyzed to establish a numerical quantitative rating of success or failure.

Principle Five: Control the Construction Obstacles and Hazard with the Appropriate Design Improvement or Appliance

Initially, the contractor's role starts when the project is advertised for bid. At that time a rudimentary construction plan is developed primarily to determine costs; however, the assessment of the hazards must be performed and figured into the costs. Once the successful bidder is selected, site-specific construction planning affords the opportunity to screen the use of construction equipment to ensure that it is safe for its intended use. This two-phase approach includes:

Safety in the construction sequence plan:

Outline specific phases of the project;

List for each all possible hazards and ways to prevent them.

Ensure that the systems and equipment is safe for its intended use by listing for each:

Anticipation hazards;

Ways design or use of appliances can be achieved to ensure a safe project.

A critical path and other master construction schedules provide a visible vehicle through which to highlight the presence of potential constructability and hazards which will arise and assure that everyone on the associated project receives notice and begins to consider the necessary constructability and safety measures to achieve productive and safe construction. One must examine closely the Hierarchy of Design in conjunction with the identified construction obstacles and hazards. The most efficient way to accomplish this is to marry the construction obstacles and hazard to the appropriate engineering control.