A White Paper on Weather in the Construction Industry
Minimizing Risks Associated with Inclement Weather: A Critical Challenge for the Construction Industry
Accountability has become a watchword of the late 1990’s for the construction industry. Owners must contend with the rising costs of design, construction, and financing. Consequently, they are demanding that contractors complete building projects quickly and efficiently and avoid costly delays, changes, and rework whenever possible. Construction professionals today work under continuous pressure to get the job done on schedule and within budget and to avoid claims at the end of the project. The industry is increasingly looking for reliable technology tools that will help recognize problems sooner and get the work done on time without additional unnecessary liability.
This paper, researched and written by On-Site Technologies Inc., looks at the growing use of computer and Information Technology (IT) within the construction industry. It suggests that a software application that allows construction planners to accurately analyze and predict the likely effects of weather, would greatly reduce weather-related risks not addressed by popular scheduling software. The result would be more accurate critical path method (CPM) schedules that obviously would minimize cost and risk to a project.
The Impact of IT on the Construction Industry
Over the last quarter century, computer and information technology has dramatically improved the way we make effective decisions and accomplish business objectives. Even in the traditionally hands-on, labor-intensive construction industry, technology has altered how work gets done, with owners now requiring in specifications or through source-selection that jobs be computerized. The value of IT quickly became apparent in the 1980s with the development of CAD/CAM systems and modeling applications, and its use increased dramatically with the introduction of project planning and critical path method (CPM) scheduling software. Construction professionals are also beginning to use and customize tools that have heretofore been considered too expensive or too technical to an ordinary construction project.
Project scheduling software, which is recognized as an invaluable tool throughout the construction industry, continues to grow in popularity and usefulness, and specialized, add-on applications that enhance the performance are emerging rapidly. A quick review of the list of Partners at the Primavera Systems, Inc. website attests to that fact. (http://www.primavera.com)
What has been noticeably absent, however, is an application that enables project planners to anticipate and factor in the effects of weather on a construction project and then adjust CPM schedules accordingly. Given the vagaries of weather, how could one realistically expect to manually compensate for both predictable and inclement weather effects? Weather-sensitive activities go on and off the critical path depending on thousands of events that occur each month on a large construction project making this task nearly impossible.
Everybody Talks about the Weather, But...
The need to anticipate and capture the effects of inclement weather on construction projects is becoming widespread in both the public and the private sectors. This is due in no small part to advances in computer and information technology that have created vast data streams and information repositories that could not have been managed even as recently as a decade ago. In the public sector, the U.S. Army Corps of Engineers (CoE), which, in some sectors, is regarded as a forerunner for tight construction specifications, now includes for accurate planning of seasonal weather conditions requirements on a project. In fact, many experts consider the CoE Regulation No. 415-1-15 as a model for addressing weather-related delays. The U.S. Navy has also begun to specify that seasonal weather conditions be factored into requests for time extensions on construction projects. Increasingly, contractors working under the federal government Network Analysis System (NAS) specifications can expect to adjust schedules for normal inclement weather. Until recently, no methods existed that could do so accurately and reliably.
Figure-1 comes from an actual CoE project at Langley Air Force Base in Hampton, Virginia.
The language of the specification does not directly
address the requirements, for it fails to specify what
constitutes "anticipated adverse weather." A generally
accepted definition of adverse or "inclement" weather
is "atmospheric conditions at a definite time and place that
are unfavorable to construction activities." Dominant
parameters for adverse weather include rainfall, freezing
temperatures, high temperatures, snowfall accumulation, high
windspeed, or any combination of these parameters.
The CoE and most sophisticated owners recommend using National Oceanic and Atmospheric Association (NOAA) data to develop delay analysis. They consider the weather "adverse" on days during which 1) precipitation reaches or exceeds .10 inch, 2) where the temperature is 32 degrees Fahrenheit or colder. The CoE predicts an 80% likelihood that two or more adverse weather conditions would be concurrent (meaning rainfall and cold temperatures would occur at the same time 80% of the time).
Although the spec requires that the contractor adjust weather-dependent activity durations for inclement weather based on a calculated chart, the language is generic. A contractor, therefore, must take all temperature and precipitation information into consideration when developing a schedule and preparing updates. In addition to the subjectivity involved, the task is a time consuming, laborious job that must be done by hand.
Within the private sector, the Association of General Contractors (AGC) published a widely used manual, Construction Planning and Scheduling Manual (1994), which discusses factors that affect CPM scheduling. The factors include seasonal weather conditions, and the AGC recommends that firms "analyze local (weather) conditions and consider the potential cost impact on the availability of labor, equipment, and material" (p.32).
Lack of Specificity – A Fundamental Problem
An examination of lost construction days on a typical project suggests that all weather-sensitive activities are susceptible to the same adverse conditions for any given month. However, weather-sensitive construction events are sensitive to different combinations of weather and also to varying degrees of those combinations. For example, the construction event MASONRY is more sensitive to rainfall than the construction event CONCRETE FOUNDATIONS. A contractor can usually pour concrete in moderate rainfall with minimal or no protection. MASONRY installation, however, rarely tolerates even light rainfall.
The Current Approach to the Problem – and the Need for a New Solution
Typically, when construction schedulers or project managers begin developing a construction schedule, they list the activities that belong to the schedule creating a record set of all the activities required to build the job. Then they estimate the expected durations of the activities based upon the quantity of work within each activity and the resources available to accomplish that work. Without a tool to predict the likely effects of weather conditions on that activity, a scheduler must rely on personal experience and tacit knowledge of what has happened before on similar jobs in similar climates. This "guesstimate" approach is often highly inaccurate because of the uncertainty involved.
Consider the following Board of Contract Appeals’ denial of a large delay claim, in part, because the contractor failed to accurately document weather impacts in the NAS schedule, which would have changed the critical path. See J. A. Jones Construction Company, 97-1 BCA 28,918 (April 17, 1998).
In that case, the contractor’s expert found that Government changes caused a 41-day delay. Weather delays were not a factor in his assessment. The expert for the Government found that weather delays did play a role, but he concluded, "even if the changes did impact the schedule, significant concurrent delays, including weather delays, negated any impact on project completion because of the changes." Because the weather impacts, or lack thereof, were not incorporated contemporaneously into the NAS to reflect the true critical path when changes occurred, the dispute was reduced to a "battle of experts" in an after-the-fact analysis.
Could the contractor have anticipated the effects more accurately to help support the claim? According to the available NOAA data, the contractor should have expected to lose 23 days to adverse weather during November and December. Instead, the actual number was more than double the projection for those two months alone. During the year in question adverse weather conditions cost the contractor as much as 111 days, or approximately 30% of the calendar year.
Every construction project experiences similar delays due to inclement weather. In attempting to reconcile schedule delay problems, project owners frequently issue time extensions or adjust the critical path if the contractor can demonstrate that abnormal or unusually severe weather conditions impacted negatively on progress at the time of the impact. It is always incumbent on the contractor, when requesting a time extension for unusually severe weather, to prove entitlement in a timely manner. Historically, this typically was done by hand, using information obtained from the NOAA or the National Climatic Data Center (NCDC). The calculations are, however, over-inclusive and general, lacking an adequate level of detail that decision-makers can use to understand the degree to which weather conditions affected the constantly changing critical path.
For example, in the case of precipitation, thresholds can have different effects on weather-sensitive construction activities and the meaning of "adverse" changes depending on the activity. Concrete columns, for instance, can be poured in light rain, but earthwork would be shutdown. Furthermore, when weather conditions are analyzed, the activities that are on the critical path at the time of the analysis must be considered. In addition, contractors are required to base a time extension analysis on a comparison between actual and historical averages. It should also be a requirement that the target CPM include normal impact data from the same source as the unusually severe data. Without the speed and accuracy of computer calculations, contractors are, thus, forced to apply rules-of-thumb. Doing this analysis on a monthly basis accurately is difficult if not impossible.
Why Rules-of-Thumb Don’t Create Accurate Project Schedules
To help avoid or to solve problems of this kind, construction schedulers need a tool that lets them account for weather conditions accurately and effectively when they develop CPM schedules. Without such a tool, every construction schedule is at risk of being inaccurate even before the job begins. Relying on gut instinct or popular rules-of-thumb that suggests the loss of one month per year to adverse weather over the life of the construction project builds in unnecessary float and is impossible to prove as the critical path changes. In a recent test case of the "one month per year" rule, examiners running the tests identified weather-sensitive activities and put them into different construction-event categories. For example, masonry events, concrete events, and earthwork events are all distinct events each being sensitive to different weather combinations and each having a varying degree of weather impact. Calculations showed that the rule was off by 33%. Thus, it appears that the impact of weather on this project had been overestimated by at least one-third. It could have been just as easily underestimated by this same amount, which would have been an expensive mistake.
Most planners now rely on such critical path methodology (CPM) software applications as Primavera Project Planner® (P3®) and SureTrak Project Manager®, which are recognized as standards for the construction industry. These applications incorporate underlying Precedent Evaluation and Review Technique (PERT) algorithms and Critical Path Methodology (CPM) that were developed more than four decades ago to ensure that the tasks of thousands of engineers, scientists, and technologists working on National Aeronautics and Space Administration (NASA) programs were completed according to schedule. Migration to the construction industry was inevitable because of similar needs to coordinate radically different trades and tasks to create a finished construction project.
Building a CPM schedule requires that construction planners identify all the activities required to complete a project and calculate the expected durations of all activities. Perhaps the easiest part is identifying the tangible resources that are available to perform specific tasks. In the case of earthwork, if 10,000 cubic yards of soil must be removed from the site, the planner, knowing the resources available to perform this task and the rate of productivity, can easily calculate its duration. But planners and schedulers must also identify the weather-sensitivity of the construction activities. As noted previously, they typically have relied on instinct and experience to adjust expected durations.
At the top of many construction professionals’ "wish lists" is a software application that would let them assume no weather impacts in their planned schedule and make needed adjustments programmatically, using readily available data that have been maintained by the National Weather Service and the World Meteorological Organization. But neither P3 nor SureTrak provides a means of accounting for weather impacts. Furthermore, because durations are the primary elements in the underlying algorithms for which these applications are built, users must take great care to start with accurate numbers that account for the most sensitive of these activities, i.e., weather-sensitive activities.
The "wish list" tool would let the user classify various construction activities according to the weather-sensitive categories in which they belong and define relevant weather parameters for each of the categories. For example, with masonry, the user could define the precipitation thresholds that affect bricklaying. A similar definition could also be performed for such weather phenomena as temperature, windspeed, and snowfall accumulation. The tool could draw from the historical database of weather conditions provided by the NCDC and determine the average number of times those weather parameters are likely to affect a specific masonry event. Such capability would provide a level of accuracy that lets the scheduler make informed scheduling decisions rather than relying on a vague general estimate of total days lost construction time.
How does one reasonably factor the vagaries of Mother Nature into an already complex network of tasks so that a project can accurately and quickly predict the effect of weather events on a project as they occur? We believe that, given the right kind of software, schedulers can do just that. The importance of an application for calculating the effects of weather cannot be overstated. It can make a critical difference between success and failure on a large or small construction project.
Building on the construction industry experience of its founders, On-Site Technologies, a software firm dedicated to solving the problems faced by construction professionals, has recently introduced WeatherExpert™. This application lets users account for weather variables in ways that traditional methods do not. Because construction events are sensitive to different and varying degrees of weather impacts, the need for frequent schedule updates renders construction schedules dynamic. WeatherExpert’s process is as dynamic as the construction schedule. This new tool, which attracted considerable attention at the September 1998 Primavera User’s Conference in Orlando, Florida, gives schedulers and construction planners a much finer level of detail and control than they have ever had before in developing and maintaining accurate construction schedules.
WeatherExpert’s algorithm calculates a proportional modifier that lets users define and specify thresholds for a variety of weather effects. It eliminates the typical speculation about when construction events that are affected by weather can take place. WeatherExpert gives users the ability to address the individual activities that are affected by weather and assign each a threshold sensitivity to weather instead of a blanket, randomly defined weather calendar. Using data from the NCDC to track both potential and actual effects of weather conditions in almost 300 major cities across the United States, WeatherExpert lets users calculate the effects of lost working days for the particular project and adjust CPM schedules to minimize the effects of lost time and justify needed time extensions.
Effective as a stand-alone application, WeatherExpert interfaces readily with scheduling software like P3 and SureTrak and increases the power and effectiveness of existing applications by enabling schedulers to predict and evaluate the likely effects of inclement weather. Project planning software becomes much more powerful and effective thanks to the precise, location-specific information and an unprecedented degree of control that WeatherExpert provides.
Time is money, and weather affects time. The first software tool that addresses weather conditions in even the most tightly written construction specifications — On-Site Technologies’ WeatherExpert lets users plan for and minimize the adverse effects of those proverbial "rainy days."
Copyright © 1999 On-Site Technologies, Inc.
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