DSpace at VNU: Analysis of Adverse Weather for Excusable Delays

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Analysis of Adverse Weather for Excusable Delays Long D Nguyen1; Jax Kneppers2; Borja García de Soto, P.E., A.M.ASCE3; and William Ibbs, M.ASCE4 Abstract: Severe weather conditions can be disruptive to construction Contractors typically obtain time extensions for weather days beyond normal conditions However, contracting parties often dispute the extent of weather-related time extensions Typical industry contracts may overlook many important points that can provide an acceptable resolution This paper classifies seven factors causing discrepancies in analysis of adverse weather for time extensions; namely, the definition of normal weather, weather thresholds, type of work, lingering days, criteria for lost days, lost days equivalent due to lost productivity, and work days lost versus calendar days lost An analysis of an actual weather-caused delay claim illustrates the impacts of those factors on the outcomes of the analysis A contract should define anticipated weather delay days and their lingering days and provide threshold values for weather parameters to differentiate between predictable and unpredictable severe weather The contract should clearly define how a time extension is granted in calendar days as a result of work days lost, and also address how a time extension is granted due to inefficiency caused by unusually severe weather Future research may provide an appropriate mechanism for analyzing equivalent lost days to account for lost productivity DOI: 10.1061/͑ASCE͒CO.1943-7862.0000242 CE Database subject headings: Claims; Weather; Delay time; Contracts; Construction management Author keywords: Claims; Weather; Delay time; Contracts; Construction management Introduction Construction productivity is typically exposed to and contingent on weather conditions These conditions are local, seasonal, and sometimes unusual Inclement weather conditions may result in project delays, disruptions, and possibly disputes between the project parties Many trades ͑e.g., earthwork, concrete, structural frame, roof, landscape͒ are readily affected by unexpectedly severe weather while other trades ͑e.g., ceiling, carpet͒ may be not Hurricane Katrina and its aftermath not only delayed construction projects regionally but nationally and even globally due to the shortage of construction materials and construction equipment Thus, owners, general contractors, and trade contractors alike face risks associated with weather conditions The project parties respond to such risks by adopting strategies which include: contingency, purchasing insurance, sharing or shifting risk to other parties through the contract terms and conditions, to name a few Lecturer, Faculty of Civil Engineering, Ho Chi Minh City Univ of Technology, Ho Chi Minh City, Vietnam; formerly, Construction Consultant, Jax Kneppers Associates, Inc ͑JKA͒, 2125 Ygnacio Valley Rd., Suite 200, Walnut Creek, CA 94598 ͑corresponding author͒ E-mail: ndlong@hcmut.edu.vn President, Jax Kneppers Associates, Inc ͑JKA͒, 2125 Ygnacio Valley Rd., Suite 200, Walnut Creek, CA 94598 E-mail: a-jax@jaxkneppers com Construction Consultant, Jax Kneppers Associates, Inc ͑JKA͒, 2125 Ygnacio Valley Rd., Suite 200, Walnut Creek, CA 94598 E-mail: borja@jaxkneppers.com Professor of Construction Management, Dept of Civil and Environmental Engineering, Univ of California, Berkeley, CA 94720; and President, The Ibbs Consulting Group, Inc E-mail: DRCWIbbs@aol.com Note This manuscript was submitted on January 8, 2009; approved on May 26, 2010; published online on June 5, 2010 Discussion period open until May 1, 2011; separate discussions must be submitted for individual papers This paper is part of the Journal of Construction Engineering and Management, Vol 136, No 12, December 1, 2010 ©ASCE, ISSN 0733-9364/2010/12-1258–1267/$25.00 Project owners generally allocate the risks of weather-related delays through contract provisions such as “weather,” “default,” and “force majeure” clauses The common rule is to grant an extension of time to a contractor for a delay caused by abnormally adverse weather conditions ͑Kartam 1999͒ Such delay is normally excusable and noncompensable How “abnormal” is defined affects the amount of time extension, especially if an extremely severe weather day, for instance, is actually an excusable delay Weather was the second leading cause of the 24 claims investigated in Canada ͑Semple et al 1994͒ It was the most frequent reason for delay claims in 57 surveyed projects, presumably built in Canada ͑Yogeswaran et al 1998͒ This paper presents factors affecting the analysis of inclement weather delays in construction projects A disputed project is used as a case study Though the dispute involved several issues such as project delays, achievement of substantial completion, and construction defects, this paper concentrates on the different views and analyses of adverse weather delays for the same contract This paper also attempts to determine how these factors should be addressed in construction contracts to reduce different technical interpretations of abnormal weather conditions and, subsequently, different analyses and results A major contribution of this paper is that it expands the analysis of adverse weather for excusable delays Thus, this research helps improve the reliability of the analysis and hence makes extensions of time more agreeable between project parties Legal interpretations of weather delay related provisions are beyond the scope of this paper Related Work Extensive research has been conducted on many facets of the impacts of weather conditions on construction projects Weather is a crucial factor causing project delays and cost overruns ͑Baldwin et al 1971; Laufer and Cohenca 1990; El-Razek et al 2008͒ 1258 / JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / DECEMBER 2010 Downloaded 18 May 2012 to 130.220.71.20 Redistribution subject to ASCE license or copyright Visit http://www.ascelibrary.org Table Average Number of Adverse Rain Delays for Santa Rosa, California January 12 February March April May June July August September October November December 10 10 1 1 10 Other research has quantified the impacts of severe weather on productivity ͑Grimm and Wagner 1974; Thomas et al 1999; ElRayes and Moselhi 2001͒ Many studies have proposed better practices in dealing with weather risks to construction activities and trades, project schedules, or project costs, etc ͑Maunder et al 1971; Benjamin and Greenwald 1973; Smith and Hancher 1989; Moselhi et al 1997; Connors 2003; Xi et al 2005; Chan and Au 2008͒ Several studies have investigated how weather is specified in construction contracts ͑Hinze and Couey 1989͒ and is ruled on litigation cases ͑Finke 1990͒ However, few studies address the issue of differentiating unusually ͑unpredictably͒ inclement weather from usually ͑predictably͒ inclement weather, because this is a principle for classifying weather delays in typical construction contracts The differentiation is actually not easy though It has challenged the project practitioners and claims analysts, and is subject to speculation and manipulation Prerequisites for Time Extensions due to Weather When encountering unusually severe weather, a contractor is normally entitled to obtain additional time but not additional money Specifically, a severe weather condition is an excusable delay if it: ͑1͒ meets contract requirements; ͑2͒ is not foreseeable; and ͑3͒ impacts the critical path The first and the last principles seem straightforward The contractor has to notify the owner and/or other authorized parties per contract requirements if a delay occurs For instance, in Handex ͑2005͒, the Court states “we believe there was sufficient evidence of an ‘abnormal weather condition’ as described in Handex’s weather logs and data to give the issue to the jury However, ͓…͔ the contract clearly states that claims for more time due to ‘abnormal weather conditions’ would only be considered when brought ‘within the Contract Times’ ͓…͔ Their request, made 10 July 2001, was well outside of the contract time.” A thoughtful delay analysis would answer if a weather delay is critical for the third principle, which is another focus of previous research ͑Smith and Hancher 1989; Moselhi et al 1997; Moselhi and El-Rayes 2002͒ Schedule delay analysis has also been improved recently ͑Hegazy and Menesi 2008; Nguyen and Ibbs 2008͒ The second principle is more ambiguous and disputable as discussed below In the construction industry, “foreseeability is the standard applied to many excusable delays by courts interpreting and applying any clauses … Foreseeable delays that are often deemed nonexcusable for the contractor include delays due to normal weather conditions” ͑Bramble and Callahan 2000͒ Thus, a contractor cannot allege that all severe weather conditions are excusable delays Severe weather conditions in excess of the total expected or foreseeable for the duration of the project for a given location may be the basis for a contract time extension if the contractor can demonstrate that the unexpected adverse weather delayed activities on the critical path In the American Institute of Architects ͑AIA͒ Document A2012007 ͑American Institute of Architects 2007͒, “General Conditions of the Contract for Construction” ͑hereafter referred to as AIA A201͒, which is widely used in the U.S construction industry, subsection 15.1.5.2 says “If adverse weather conditions are the basis for a Claim for additional time, such Claim shall be documented by data substantiating that weather conditions were abnormal for the period of time, could not have been reasonably anticipated and had an adverse effect on the scheduled construction.” However, abnormal or “not … reasonably anticipated” is not defined This may create speculation and dispute among the project parties and schedule consultants involved in the claims and disputes Results derived by one party/schedule consultant cannot be reassembled by the other Consequently, an equitable settlement can be difficult to achieve Factors Affecting Weather Delay Analysis Various factors influence analysis of severe weather and its results This research systematizes these factors as discussed below Definition of Normal Weather Normally severe weather conditions should be incorporated in all construction contracts and the contract should differentiate between normally and abnormally severe weather conditions A clear definition of “normally anticipated weather” should exist to avoid any ambiguity ͑Hinze and Couey 1989͒ Some owners and contractors now provide the number of anticipated weather days in their contracts In other words, contracts specify the average ͑normal͒ number of adverse rain days for the project location Table presents such an example of the number of adverse rain days included in the project manual of a public contract in Santa Rosa, California The basis for deriving the monthly anticipated adverse weather delay is typically not provided though That is, contracts may specify the numbers of normal weather delay days but not describe where they come from Disputes may arise as to what constitutes an unusually severe weather when the basis for comparison is unclear Though presenting that the precipitation was greater than the 20-year average, a contractor’s claim failed because the precipitation, as shown by the owner’s expert, was lower than the past 5-year or 24-year average ͑McDevitt 1989, cited in Bramble and Callahan 2000͒ With regulation number ER 415-1-15, the U.S Army Corps of Engineers ͓U.S Army Corps of Engineers ͑USACE͒ 1989͔ provided the methodology for construction time extensions for weather-related delays for its contracts However, guidance for this methodology has changed over time and acknowledged in its construction bulletins ͓U.S Army Corps of Engineers ͑USACE͒ 1996, 2008͔ The time extension granted in calendar days, for instance, is determined differently U.S Army Corps of Engineers ͑USACE͒ ͑1996͒ determined the time extension as a product of the work day delay and “a ratio of seven calendar days per week to the number of scheduled work days per week” whereas U.S Army Corps of Engineers ͑USACE͒ ͑2008͒ instructed that it “should be based on the new calculated early finish date as a result of the added unusually severe weather frag-net.” Inconsistent application of ER 41-1-15 is also recognized by the unreasonable evaluation of what constitutes usually severe and unusually severe weather ͓U.S Army Corps of Engineers ͑USACE͒ 2008͔ JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / DECEMBER 2010 / 1259 Downloaded 18 May 2012 to 130.220.71.20 Redistribution subject to ASCE license or copyright Visit http://www.ascelibrary.org The definition of normally severe weather becomes more awkward when contracts not provide the number of anticipated weather delay days Contract documents have an unclear description of normal weather ͑Smith and Hancher 1989͒ In many contracts, wind, temperature, precipitation weather parameters and weather statistics such as the length of historical weather data, mean versus median of the data, etc., are unavailable to help establish the anticipated weather In addition, unusually severe weather days are different between weather analyses based on a month-by-month basis versus those based on the whole duration of the contract work For instance, the Interior Board of Contract Appeals once held that the delay caused by unusually inclement weather in one month can offset the unusually good weather in another month ͑Bramble and Callahan 2000͒ Unless contracts account for and provide specific definitions for these items, time extensions will be difficult to assess due to a multitude of ways to define normally severe weather coupled with the many possible answers regarding the foreseeability or unforeseeability of weather-related delays Weather Thresholds Inclusion of weather thresholds in construction contracts is important because they determine what qualifies as a weather delay day An example would be that “work must be completely stopped if temperatures are below −10° F ͑−23.3° C͒ or above 110° F ͑43.3° C͒.” This is because efficient construction operations are difficult to achieve with those temperatures ͑Koehn and Brown 1985͒ This factor is somewhat related to the definition of normally adverse weather Intensity of rainfall, type of construction operation, and on-site drying conditions are three key factors affecting weather-related delays and disruptions ͑El-Rayes and Moselhi 2001͒ Intensity of rainfall is associated with weather thresholds while the last two factors are associated with the next two dimensions, namely type of work and lingering days Different threshold values for a given weather condition result in different number of normally and abnormally severe weather days for the same actual conditions during the same timeframe The Boards of Contract Appeals ͑BCA͒ sometimes determine inconsistent threshold values The National Aeronautics and Space Administration ͑NASA͒ BCA once viewed the severe weather as at least a trace ͑less than 0.01 in or 0.254 mm͒ of rainfall while the Armed Services BCA ͑ASBCA͒ in a case rejected this threshold value and used a daily severity of 0.5 in of rainfall ͑Finke 1990͒ Threshold values also depend on trades and natural and social factors For reference only, effective on October 14, 1993 NASA discontinued its BCA and let its contract appeals be decided by ASBCA ͑Worthington and Goldsman 1998͒ Some contracts already determine threshold values for adverse weather The Tennessee Department of Finance and Administration ͓Tennessee Department of Finance and Administration ͑TennDFA͒ 2007͔, for example, establishes threshold values as 0.10 in ͑2.54 mm͒ for precipitation ͑rain, snow, or ice͒, temperatures not above that required for the work of the day, and sustained wind above 25 mi/h ͑40 km/h͒ for its capital projects No single threshold value for temperature exists because the characteristics of a particular work decide the range of temperature that the work can be performed For instance, the temperature threshold of asphalt pavement is lower than that of concrete pavement With prima facie thresholds, the contractor only needs to show that the actual conditions exceeded the thresholds ͑Xi et al 2005͒ However, a weather day should be decided based on the combination of the threshold values, type of work affected, and com- mon sense ͑McDonald 2000͒ Kenner et al ͑1998͒ recommended that if two parties not agree whether the weather conditions support working or nonworking, then the decision will be based on the comparisons of the threshold values and actual weather data of the day in question Type of Work Type of work may also define the weather impact Certain activities are particularly sensitive to weather conditions ͑Attanasi et al 1973͒ In addition, several factors ͑e.g., duration, exposure, material characteristics, equipment used, level of protection provided͒ for each activity influence the activity’s sensitivity to wind, temperature, and precipitation ͑Smith and Hancher 1989͒ A project’s weather sensitivity also depends on the phase of construction The initial site phase of building construction, for example, is usually more sensitive to weather than the dried-in phase ͑McDonald 2000͒ Consequently, the allocation of monthly anticipated adverse weather delay in contracts is not sufficient The scheduled activities and their sequence should be known before the number of monthly weather days has been determined because the weather impact is associated with the type of activities being performed ͑Xi et al 2005͒ Lingering Days The effect of weather impact on a project may not end when the severe weather concludes It may extend beyond actual severe weather periods due to site preparation, before/after snowy conditions, drying time for soils, and accumulated water on the site ͑Finke 1990͒ “Dry-out” or “mud” days are also used to describe lingering days McDonald ͑2000͒ categorized weather days as weather event day, mud day, and rework or impact day In at least one instance a contractor was entitled to a time extension due to unplanned work performed by the contractor and necessitated due to unusually severe weather conditions ͑Finke 1990͒ Even when specifying the number of monthly normally adverse weather days, a contract is still ambiguous if it does not determine how to deal with lingering days Contracts should provide a definition for lingering days and clearly spell out whether lingering days are included in the monthly normal weather days In Tennessee Department of Finance and Administration ͑TennDFA͒ ͑2007͒, adverse weather may include dry-out or mud days “at a rate no greater than make-up day for each day or consecutive days of beyond the standard baseline that total 1.0 inch or more, liquid measure….” El-Rayes and Moselhi ͑2001͒ investigated the lingering effects of rainfall for four highway construction activities, namely earthmoving, base courses, drainage layers, and paving Differentiating between lingering days caused by predictable and unpredictable severe weather conditions is also important This is because two options are available Dry-out days can be counted as delay days prior to the analysis of usually or unusually severe weather Alternatively, any dry-out day caused by usually severe weather can be considered usually severe Consequently, the monthly anticipated adverse weather days must be defined differently under these two options Tennessee Department of Finance and Administration ͑TennDFA͒ ͑2007͒ followed the second option by specifying that dry-out or mud” days are not counted as a weather delay day until the anticipated adverse weather delay is exceeded When a month-by-month analysis for adverse weather is used with the second option, the contract should define how to deal with lingering days that “roll over” into the next month 1260 / JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / DECEMBER 2010 Downloaded 18 May 2012 to 130.220.71.20 Redistribution subject to ASCE license or copyright Visit http://www.ascelibrary.org March 2008 April 2008 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 R R R R R R D R R 10 rain (R) days; "dry-out" (D) day R R D R R R D rain (R) days, "dry-out" (D) day "Roll-over" Fig Rain and lingering days in March 2008 Fig illustrates the issues with lingering effects The shaded dates are weekends and holidays The data shown come from contemporaneous project records in the aforementioned public contract in Santa Rosa, Calif ͑Table 1͒ The contractor was not able to work on any rain or dry-out days Month-by-month analysis is assumed to be acceptable The average number of adverse rain delays for March and April are 10 and days, respectively ͑Table 1͒ Determining the number of abnormally adverse weather days in March 2008 is not easily answered Whether the numbers ͑Table 1͒ include only anticipated rain days or a combination of anticipated rain and dry-out days is unclear If dry-out days are included, the answer is simple Any delay, regardless of rain or dry-out days, beyond 10 days is unusually severe That is, the contractor would experience four unusually severe weather delay days ͑dates 20, 21, 26, and 31͒ in March 2008 If dry-out days are not included, the answer is much more difficult to ascertain Table would be unhelpful if dry-out days are counted prior to differentiating unusually severe from usually severe Table would still be useful if only dry-out days caused by unusual rains are unusual as in Tennessee Department of Finance and Administration ͑TennDFA͒ ͑2007͒ The contractor would experience three unusually severe weather days ͑dates 21, 26, and 31͒ in this scenario However, the anticipated challenge is the dry-out day that rolls over into April 2008 ͑date 1͒ Unless clearly predefined in the contract, speculation is needed to determine whether a roll-over dry-out day is considered a normally or abnormally adverse weather Criteria for Lost Days Criteria for defining lost days due to weather events vary in contracts In fact, many contracts not define such criteria at all The percentage of absent workforce, the percentage of the day worked, or a combination of these two is often used to define a lost day ͑Hinze and Couey 1989͒ To qualify as actual severe weather delay days, U.S Army Corps of Engineers ͑USACE͒ ͑1989͒ required that critical activities cannot be performed for 50% or more of the contractor’s scheduled work days Hinze and Couey ͑1989͒ recommended that the percentage of the day that cannot be worked be used as the criterion for defining lost days caused by unusually severe weather Lost Days Equivalent due to Lost Productivity Adverse weather reduces labor productivity This is especially true for construction that is typically exposed to weather Working under adverse weather condition may make the performance less efficient though may not stop the work ͑Bramble and Callahan 2000͒ Inefficiency or decreased productivity due to adverse weather can contribute to schedule delay That is, adverse weather not only delays a project due to such direct lost days as weather event, dry-out, mud, “rework,” and “unplanned work” days, it also prolongs schedule activities due to lost productivity or inefficiency That, in turn, may delay the overall project schedule In many circumstances, a contractor is not entitled to compensation incurred by lost labor productivity caused by unusually severe weather That is, only lost time associated with unusually adverse weather can be recovered This paper uses the term “lost days equivalent” to describe the project delay due to productivity losses caused by unusually severe weather Contractors may recover such lost days if the prerequisites for time extension are met However, in most cases contractors fail to acknowledge lost days equivalent in their analyses and subsequent requests for time extensions A possible explanation for this oversight is that indirect weather impact is probably not realized at the time of occurrence but several months later ͑Hinze and Couey 1989͒ A time extension was granted in a General Services BCA’s decision due to reduced productivity despite the fact that the contractor worked during the periods of unusually severe weather ͑Finke 1990͒ McDonald ͑2000͒ recommended that productivity impacts caused by adverse weather must be incorporated into the schedule Work Days Lost versus Calendar Days Lost Project durations are typically expressed in calendar days Similarly, time extensions are typically requested and granted in calendar days On the other hand, adverse weather conditions are usually expressed in work days Lost days due to weather therefore have to be converted to calendar days In typical practice the number of lost days in calendar days equals the number of work days lost times a conversion factor, 7/5, if five work days per week are used as in U.S Army Corps of Engineers ͑USACE͒ ͑1996͒ This method may not be appropriate because the number of available work days is different from month to month in a calendar year In one case the U.S Court of Claims held that the number of winter days granted to the contractor was not equal to the number of excusable delay days encountered in the summer season ͑Bramble and Callahan 2000͒ As a result, the seasonal weighting of days may be used as a better mean for converting from work days to calendar days ͑Hinze and Couey 1989͒ As an example, a seasonal weighting approach is applied to the above case ͑Table 1, Fig 1͒ This example assumes that the number of monthly anticipated severe weather ͑Table 1͒ includes dry-out days and that all lost days due to weather during March 2008 ͑Fig 1͒ are critical If the probability of occurrence of an adverse rain day is the same for any day of the month, the number of anticipated rain days that occurred in weekdays during March would be approximately days ͑10 anticipated rain days multiplied by 21 work days and divided by 31 calendar days͒ Thus, there are 14 available work days in March 2008 ͑31 calendar days minus 10 weekend days minus anticipated rain days in weekdays͒ As a result, the four unusually severe weather days in JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / DECEMBER 2010 / 1261 Downloaded 18 May 2012 to 130.220.71.20 Redistribution subject to ASCE license or copyright Visit http://www.ascelibrary.org Case Study This research chooses case study over other research methods, such as surveys or analysis of archival information Case study methodology helps us understand insight into the impacts of the factors presented above on analysis of adverse weather for excusable delays in a real-life context Project Description The case study presented in this paper is two one-story tilt-up office buildings located in Livermore, California ͑hereafter refer to as Project ABC͒ The original contract price and project duration were approximately $5 million and 265 calendar days, respectively Eleven changer orders were issued but caused little change in the contract dollar amount The owner and the general contractor drafted the agreement themselves, using commonplace contract conditions The contract did not determine the number of normally adverse rain days or mud/dry-out days, nor did it include the weather threshold to be used AIA A201 ͑American Institute of Architects 1997͒ General Conditions were part of the contract Liquidated damages amounted to $5,000 per calendar day ͑$5,000/day͒ The contract specified that inclement weather conditions beyond normal were excluded Although there were some disputes between the parties as to what was included in the contract, they agreed that the contractor was eligible for time extensions due to unusually severe weather The contractor complied with contract notice requirements Work started in mid-October of 2005 and required substantial completion by mid-July2006 The buildings were not dried-in until mid-April of 2006 That is, the initial site phase was through the 2005/2006 winter which was the rainy season in Livermore, Calif Critical construction activities affected by adverse weather included, but were not limited to, slab on grade, casting and erecting tilt-up panels, erecting and welding steel columns, installation of wood roof structures, and roofing Due to the limited slab area, activities for casting and erecting tilt-up panels were divided into two stages in the as-planned schedule The geotechnical report revealed moderately expansive soils at this project site 20 Rain Days (Precipitation > 0.254 mm) March 2008 ͑dates 20, 21, 26, and 31 as explained in the section “Lingering Days”͒ in the above case would be approximately 8.9 ͑4 ϫ 31/ 14͒ calendar days using the seasonal weighting of days compared to only 5.6 ͑4 ϫ / 5͒ calendar days using the U.S Army Corps of Engineers ͑USACE͒ ͑1996͒ approach The above example demonstrates that the method used for converting from work days to calendar days plays an important role for weather risk allocation in contracts This is because the conversion results are inconsistent Nevertheless, many contracts not specify an appropriate conversion mechanism Disputes may arise if contracts not define a method for converting from work to calendar days when determining the number of delay days The U.S Army Corps of Engineers recently instructed its agencies to extend the performance period based on the result of the added abnormally adverse weather “frag-net” in the schedule ͓U.S Army Corps of Engineers ͑USACE͒ 2008͔ This is perhaps the most appropriate and accurate approach to avoid any confusion and inconsistency in the conversion, but also the most arduous 18 16 14 12 10 November December January Average 1971-2000 February March April Actual 2005-2006 Fig Average and actual rain days ͑precipitation Ն0.254 mm͒ in winter in Livermore, California Adverse Weather as a Part of Project Delay and Dispute The project suffered delays The owner established that substantial completion was achieved in mid-December of 2006, and assessed liquidated damages for more than months of delay The contractor disagreed and brought the case to arbitration Among other things, the contractor claimed that the delays were out of his control and caused by abnormally adverse weather conditions and owner-caused delays The owner counterclaimed for contractorcaused delays and construction defects Adverse weather during the period between November 2005 and April 2006 was among the major issues under the dispute Although the owner acknowledged that the contractor was due time extensions as a result of adverse weather conditions, an agreeable time extension for weather was never reached because the parties and their consultants proposed very different numbers The following section shows why such a situation occurred in this dispute Adverse Weather Analysis Unusually inclement weather was claimed as a cause of delays Adverse weather affected and ultimately delayed the project in the winter of 2005/2006 However, whether the delay was excusable requires proper analysis Most importantly, the type of analysis affected the number of days the contractor should be granted if inclement weather was beyond normal conditions Inconsistent answers to this question were a source of the dispute General analysis of the rains occurring in the 2005/2006 winter was needed to check if rains were abnormal The contract provided neither the monthly anticipated inclement weather days nor threshold values for precipitation Consequently, the baseline for comparison was difficult to establish Figs and illustrate the numbers of normal and actual rain days in Livermore for two precipitation thresholds: 0.254 mm ͑0.01 in.͒ and 2.54 mm ͑0.1 in.͒ Data sources were obtained from the National Oceanic and Atmospheric Administration ͑NOAA͒ ͑2008a,b͒ This analysis ignores the effect of the period chosen for establishing the monthly anticipated rain days The 30-year average, from 1971 to 2000, was selected for convenience because statistics were available from National Oceanic and Atmospheric Administration ͑NOAA͒ ͑2008a͒ Naturally, weather statistics through 2005, when the contract actually started, would be ideal, but were not available The contract did not endorse any timeframe for defining normally adverse rain days 1262 / JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / DECEMBER 2010 Downloaded 18 May 2012 to 130.220.71.20 Redistribution subject to ASCE license or copyright Visit http://www.ascelibrary.org Rain Days (Precipitation > 2.54 mm) 16 14 12 10 November December January Average 1971-2000 February March April Actual 2005-2006 Fig Average and actual rain days ͑precipitation Ն2.54 mm͒ in winter in Livermore, California Analysis shows that adverse weather in the winter of 2005/ 2006 was actually abnormal ͑Figs and 3͒ There were actually more actual rain days than could have been reasonably anticipated in December 2005 and March and April 2006 Different weather threshold values may draw different conclusions if a particular rain day in a particular month is abnormal For instance, adverse weather in January 2006 was abnormal with precipitation equal to or greater than 0.254 mm ͑Fig 2͒ while it was normal with precipitation equal to or greater than 2.54 mm ͑Fig 3͒ This confirms that threshold values define how unusual a severe weather condition is For Project ABC the winter of 2005/2006 was categorized as abnormal under both circumstances Cumulative precipitations also support that abnormality ͑Fig 4͒ The precipitations for December 2005 and March 2006 exceeded the average precipitation by 165 and 94%, respectively The actual total precipitation for 2005/2006 winter ͑November 2005 to April 2006͒ was 30% more than average During the course of the work the contractor properly notified the owner inclement weather and mud days had occurred The owner was notified of a total of 52 weather-related lost days The owner reviewed and responded to the contractor’s notices if they did not agree or required clarification Due to a lack of supporting information provided to the owner, a total of fifteen weatherrelated lost days were rejected by the owner The contractor accordingly revised the delay notices and removed twelve of the fifteen lost days rejected by the owner The contractor still maintained his view with respect to three lost days that the owner did 160 Precipitation (mm) 140 120 100 80 60 40 20 November December January Average 1971-2000 February March April Actual 2005-2006 Fig Average and actual precipitations in winter in Livermore, California not agree with That is, there were forty ͑52− 12͒ lost days ͑including three disputable lost days͒ timely notified and recorded at the end of the contract ͑Table 2͒ Fig illustrates the flowchart for analyzing adverse weather and Table summarizes the analysis Columns ͑2͒ and ͑3͒ are the lost days that the contractor notified to the owner Three alleged lost days January 13, February and 7, 2006 were not agreed to by the owner ͓noted as “dispute” in Column ͑12͔͒ An independent review of the contemporaneous project records was required to understand what happened on those days January 13 appeared to be an actual lost day because project photos taken on the same day show muddy site conditions that did not allow concrete trucks to access the site to deliver concrete for the tilt-up panels In contrast, February and were likely not lost days due to mud A subcontractor’s daily report shows that the concrete subcontractor could not mobilize in a timely fashion and deliver a crane for erecting tilt-up panels The contractor, not the weather, was responsible for these two lost days The critical activity ͑erect tilt-up panels͒ could not be performed because a crane was not available Analysis of concurrent delays was not necessary because weather was not a cause on these lost work days The independent review also revealed that December 26, 2005 ͑Monday͒ was not a lost day due to weather although heavy rain occurred that day Daily logs revealed that Christmas Day occurred on Sunday, December 25, 2005 and was moved to Monday, December 26, 2005 The contractor assigned that day as a holiday in the project schedule update The result is that only 37 lost days were actually caused by weather-related conditions and/or their lingering effects The key task was to determine which of those days were abnormal The remaining columns in Table have the following meanings Column ͑4͒ describes the type of lost day that the contractor documented in its notices The two types were “rain” and mud ͑or dry-out͒ Precipitation amounts ͓Column ͑5͔͒ were obtained from National Oceanic and Atmospheric Administration ͑NOAA͒ ͑2008b͒ Column ͑6͒ shows the equivalent precipitation in millimeters As previously mentioned, the contract did not provide any threshold for rains The lost days recorded mostly depended upon the actual conditions and contractor judgment Several rain days had low precipitation but caused lost time; for example, January 27 ͑0.25 mm͒, February ͑0.51 mm͒, and February ͑1.27 mm͒ of 2006 In contrast, the contractor still worked on layout, forms, and rebar of tilt panels on days with similar or higher precipitation during work hours; e.g., March 24 ͑0.76 mm͒ and March 28 ͑1.78 mm͒ of 2006 ͑not shown in Table because these days were not notified as lost days͒ One of the reasons was different construction activities were performed An arbitrary threshold for defining adverse weather for the entire project would not work in this case A better method would be to determine different thresholds for different activities Given the relationship between precipitation and lost days by rain in this case, Columns ͑7͒ and ͑8͒ count the chronological order for a particular rain day for a given month for the selected thresholds: 0.254 mm ͑0.01 in.͒ and 2.54 mm ͑0.1 in.͒, respectively For instance, the rain on December 21, 2005 was the ninth ͑fifth͒ rain day with a precipitation of 0.254 ͑2.54͒ mm or greater for that month Column ͑9͒ shows if an adverse weather day was abnormal This column is based on the comparison between the order of a certain rain day and the monthly anticipated ͑average͒ number of rain days presented in Figs and For example, using the threshold of 0.254 mm, the rain on December 21, 2005 was considered abnormal ͑“yes”͒ because it was the ninth rain day in December of 2005 while days of rain were anticipated JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / DECEMBER 2010 / 1263 Downloaded 18 May 2012 to 130.220.71.20 Redistribution subject to ASCE license or copyright Visit http://www.ascelibrary.org Table Analysis of Adverse Weather for Project ABC, Livermore, California Precipitation Number ͑1͒ Notified lost day ͑2͒ ͑3͒ Type of lost day ͑4͒ a in ͑5͒ mm ͑6͒ ith rain dayb Ն0.254 Ն2.54 mm ͑7͒ mm ͑8͒ Abnormal ͑9͒ Critical ͑10͒ Excusable ͑11͒ Remark ͑12͒ n/a ͑n/a͒ No ͑no͒ Friday November 4, 2005 Rain 0.08 2.03 1 No ͑no͒d Tuesday November 29, 2005 Rain 0.48 12.19 No ͑no͒ n/a ͑n/a͒ No ͑no͒ Thursday December 1, 2005 Rain 0.27 6.86 1 No ͑no͒ n/a ͑n/a͒ No ͑no͒ Friday December 2, 2005 Mud 0.20 5.08 2 No ͑no͒ n/a ͑n/a͒ No ͑no͒ Monday December 19, 2005 Mud 0.05 1.27 n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ Tuesday December 20, 2005 Mud 0.01 0.25 n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ Wednesday December 21, 2005 Rain 0.27 6.86 Yes ͑no͒ Yes ͑n/a͒ yes ͑no͒ Thursday December 22, 2005 Rain 0.38 9.65 10 Yes ͑yes͒ Yes ͑yes͒ Yes ͑yes͒ n/a Yes ͑yes͒ Yes ͑yes͒ Yes ͑yes͒ Friday December 23, 2005 Mud 0.00 0.00 n/ac 10 Monday December 26, 2005 Rain 0.37 9.40 12 n/a ͑n/a͒ n/a ͑n/a͒ n/a ͑n/a͒ Holiday 11 Wednesday December 28, 2005 Rain 0.23 5.84 13 Yes ͑yes͒ Yes ͑yes͒ Yes ͑yes͒ 12 Tuesday January 3, 2006 Rain 0.02 0.51 n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ 13 Wednesday January 4, 2006 Mud 0.00 0.00 n/a n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ 14 Thursday January 5, 2006 Mud 0.00 0.00 n/a n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ 15 Friday January 13, 2006 Mud 0.00 0.00 n/a n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ Dispute 16 Friday January 27, 2006 Rain 0.01 0.25 n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ Yes ͑n/a͒ yes ͑no͒ 17 Monday January 30, 2006 Rain 0.16 4.06 11 Yes ͑no͒ 18 Tuesday January 31, 2006 Mud 0.00 0.00 n/a n/a Yes ͑no͒ Yes ͑n/a͒ yes ͑no͒ 19 Wednesday February 1, 2006 Rain 0.02 0.51 n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ 20 Thursday February 2, 2006 Rain 0.05 1.27 n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ 21 Friday February 3, 2006 Mud 0.00 0.00 n/a n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ 22 Monday February 6, 2006 Mud 0.00 0.00 n/a n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ Dispute 23 Tuesday February 7, 2006 Mud 0.00 0.00 n/a n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ Dispute 24 Monday February 27, 2006 Rain 0.21 5.33 No ͑no͒ n/a ͑n/a͒ No ͑no͒ No ͑no͒ 25 Tuesday February 28, 2006 Rain 0.44 11.18 No ͑no͒ n/a ͑n/a͒ 26 Wednesday March 1, 2006 Mud 0.00 0.00 n/a n/a No ͑no͒ n/a ͑n/a͒ No ͑no͒ 27 Thursday March 2, 2006 Rain 0.19 4.83 1 No ͑no͒ n/a ͑n/a͒ No ͑no͒ 28 Friday March 3, 2006 Rain 0.24 6.10 2 No ͑no͒ n/a ͑n/a͒ No ͑no͒ 29 Monday March 6, 2006 Rain 0.54 13.72 3 No ͑no͒ n/a ͑n/a͒ No ͑no͒ 30 Tuesday March 7, 2006 Rain 0.12 3.05 4 No ͑no͒ n/a ͑n/a͒ No ͑no͒ 31 Tuesday March 14, 2006 Rain 0.31 7.87 No ͑yes͒ n/a ͑yes͒ No ͑yes͒ 32 Friday March 17, 2006 Rain 0.64 16.26 10 No ͑yes͒ n/a ͑yes͒ No ͑yes͒ 33 Wednesday March 29, 2006 Rain 0.30 7.62 17 14 Yes ͑yes͒ Yes ͑yes͒ Yes ͑yes͒ 34 Monday April 3, 2006 Rain 0.37 9.40 No ͑no͒ n/a ͑n/a͒ No ͑no͒ 35 Tuesday April 4, 2006 Rain 0.95 24.13 No ͑no͒ n/a ͑n/a͒ No ͑no͒ 36 Wednesday April 5, 2006 Rain 0.21 5.33 No ͑no͒ n/a ͑n/a͒ No ͑no͒ 37 Wednesday April 12, 2006 Rain 0.31 7.87 10 Yes ͑yes͒ Yes ͑yes͒ Yes ͑yes͒ 38 Thursday April 13, 2006 Mud 0.01 0.25 11 n/a Yes ͑yes͒ Yes ͑yes͒ Yes ͑yes͒ 39 Monday April 17, 2006 Rain 0.07 1.78 14 n/a Yes ͑no͒ Yes ͑n/a͒ Yes ͑no͒ 40 Tuesday April 18, 2006 Mud 0.00 0.00 n/a n/a Yes ͑no͒ Yes ͑n/a͒ Yes ͑no͒ Note: n / a = not applicable a Precipitation obtained from National Oceanic and Atmospheric Administration ͑NOAA͒ ͑2008b͒ b The order of a rain day in a particular month when rain is defined by precipitation c n/a in Columns ͑7͒ and ͑8͒, Columns ͑9͒ and ͑11͒, and Column ͑10͒ stands for “no rain” by definition, “not a lost day,” and “not check” if not abnormal, respectively d In Columns ͑9͒–͑11͒, x͑y͒ is the corresponding outcome per Column ͑7͒ ͓Column ͑8͔͒ for that month using the same threshold ͑Fig 2͒ However, that rain day would not be abnormal ͑“no”͒ if the threshold of 2.54 mm was used This case study also shows lingering days or mud days which the contractor could not perform their critical activities Since mud days not have precipitation, the analysis used above does not apply Instead, this analysis adopts the method proposed by Tennessee Department of Finance and Administration ͑TennDFA͒ ͑2007͒ as mentioned previously This approach states that mud days caused by “normal” rains are considered normal Using the threshold of 0.254 mm, the mud day of January 31, 2006 would be abnormal because the mud was caused by the abnormal rains 1264 / JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / DECEMBER 2010 Downloaded 18 May 2012 to 130.220.71.20 Redistribution subject to ASCE license or copyright Visit http://www.ascelibrary.org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ig Flowchart of adverse weather analysis on January 30, 2006 and earlier days Conversely, the same day would be normal with a threshold of 2.54 mm Column ͑10͒ shows whether the work impacted by the weather conditions was critical based on the delay analysis of contemporaneous project schedule updates Detailed analysis is beyond the scope of this paper Column ͑11͒ shows if a qualified lost day is excusable ͑yes͒ or inexcusable ͑no͒ A qualified lost day is excusable only if it was abnormal and critical In other words, yes must appear on both Columns ͑9͒ and ͑10͒ Time Extension The owner should grant a time extension in calendar days for unusually severe weather to the contractor in this contract For the precipitation threshold of 0.254 mm, the number of excusable work days lost due to abnormal weather conditions would be 11 That number would be eight work days if the threshold of 2.54 mm is used ͑Table 2͒ These work days lost due to abnormal weather need to be converted into calendar days As previously discussed, three alternatives for the conversion include the fixed conversion factor ͑7/5͒, the seasonal weighting of days, and the schedule fragnet for unusually severe weather While this last alternative is the most reasonable, it cannot be applied in this case because the project schedules were not assigned all anticipated nonworking days ͑U.S holidays, union holidays, anticipated weather days͒ Using the conversion factor of 7/5, the time extension would be approximately 15 calendar days for the precipitation threshold of 0.254 mm and 11 calendar days for the precipitation threshold of 2.54 mm ͓hereafter 15 ͑11͒ calendar days for the precipitation threshold of 0.254 ͑2.54͒ mm͔ Table presents the use of the seasonal weighting of days for the conversion The calculation of available work days is similar to the above example Under this alternative the extension of time would be 23 ͑14͒ calendar days for the precipitation threshold value of 0.254 ͑2.54͒ mm ͑Table 3͒ The number of excusable lost days ͑expressed in work days͒ for a particular month in Table equals to the number of yes in Column 11 of Table for the corresponding month In March 2006, for instance, the numbers of excusable lost days are one and three based on the threshold of 0.254 and 2.54 mm, respectively ͑Table 2͒ The difference in time extension for the two alternatives is eight ͑three͒ calendar days for the different weather thresholds The difference in liquidated damages assessed is $40,000 ͑$15,000͒, which can be a significant amount for a $5 million contract Discussion The case study draws many interesting points with reference to factors affecting the analysis of severe weather A consistent analysis of severe weather is impossible if the contract does not define what constitutes normally severe weather and determines weather thresholds for different work to be performed Such definitions are not always available, and as this case study shows, making different assumptions for such absent definitions results in different time extensions For instance, by adopting Tennessee Department of Finance and Administration ͑TennDFA͒ ͑2007͒ the above analysis presumes that mud days caused by normally severe weather are normal The analysis cannot be done properly without that presumption, because the anticipated severe weather delay days including mud days cannot be established However, Table Calendar Days Lost Using the Seasonal Weighting of Days Available work daysa Month Ն0.254 November 2005 December 2005 January 2006 February 2006 March 2006 April 2006 Winter 2005/2006 a Available work days, lost 15 15 13 13 16 16 Excusable lost daysa ͑work day͒ Ն2.54 Calendar days 18 17 16 15 19 18 30 31 31 28 31 30 Ն0.254 Ն2.54 0 0 11 days ͑work or calendar day͒ based on thresholds ͑0.254 mm or 2.54 mm͒ Excusable lost daysa ͑calendar day͒ Ն0.254 Ն2.54 8 23 — 14 JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / DECEMBER 2010 / 1265 Downloaded 18 May 2012 to 130.220.71.20 Redistribution subject to ASCE license or copyright Visit http://www.ascelibrary.org lingering days that roll over to a following month are still challengeable The mud day on March 1, 2006 was caused by consecutive rain days at the end of February The fact that whether that mud day would have been normal or abnormal if rains on February 27 and 28 had been abnormal is uncertain Fortunately, the above analysis does not encounter this dilemma because the rains at the end of February 2006 were normal ͑Table 2͒ Another conclusion is that contracts should specify monthly anticipated severe weather delay days Contractors should account for those days when planning their work and preparing their baseline schedules At best, these delay days should include anticipated lingering days based on construction activities scheduled in the periods of the anticipated severe weather conditions In the case that only normally adverse weather days provided, the contract should determine whether a lingering day rolling over to the following month is normal or abnormal given that adverse weather causing that lingering day is abnormal or not Different assumptions on the threshold values of precipitation change the results of the analysis With two thresholds used in this case study, the results are substantially different A particular rain day can be normal for a given threshold but abnormal if another threshold is used The results change considerably if the comparison for usually versus unusually severe weather were based on the whole project duration or the whole period allegedly affected by weather rather than a month-by-month basis That is, the winter of 2005/2006 in the case study In addition, a predetermined threshold for the entire project may not totally decide if a particular weather condition causes lost day With the monthly anticipated adverse weather days specified in contracts, thresholds should not be the primary factor deciding if a day is lost Any adverse weather day and its associated dry-out day͑s͒ ideally will be agreed to by the involved parties If not, the threshold together with the type of work scheduled, work quality required, the portion of work performed, site conditions, and so on will decide lost days In any circumstance, threshold values for different weather conditions ͑e.g., rain/snow, wind, temperature͒ should be defined in contracts, ideally for different work, activities or trades They are not only a source of reference for determining lost days, if the parties not agree as mentioned, but also are a baseline for counting actual adverse days in a particular month ͓Columns ͑7͒ and ͑8͒ in Table 2͔ Consequently, whether a lost day is abnormal is fairly determined Conversion from work days lost to calendar days lost is another issue to be addressed in contracts We believe the conversion method proposed by U.S Army Corps of Engineers ͑USACE͒ ͑2008͒ should be adopted That is, time extensions for unusually severe weather should be determined based on schedule impact analysis However, the seasonal weighting of days can be used with similar results The use of the 7/5 conversion factor that is widely employed in the industry may not be equitable Therefore, depending on project scale and the sophistication of the parties involved, contracts should specify a conversion option, either adopting U.S Army Corps of Engineers ͑USACE͒ ͑2008͒ or the seasonal weighting of days to avoid confusion and speculation The weather analysis in the case study does not cover such factors as the type of work, criteria for lost days, and lost days equivalent due to lost labor productivity In this case, the data were not available for further analysis However, these factors very often affect the schedule analysis of unusually severe weather Contemporaneous schedule updates show that many critical activities were significantly delayed during the 2005/2006 winter The delay was beyond the direct lost days due to severe weather In this particular case, factors such as site access, logistics, interrupted learning curve, remobilization of manpower and equipment, and weather change may have negatively impacted labor productivity That lost productivity could in turn significantly delay this project but the data to analyze such were not available Consequently, a truly reasonable time extension might be greater than the time extensions computed from the methods outlined in this paper Contracts should provide a mechanism for dealing with such lost days equivalent As to the reality of this particular case, the general contractor demanded that all of 40 weather delay days notified were excusable delays The owner on the other hand accepted only 21 calendar days without any justification The two parties never agreed each other on weather based time extensions, so they took this issue to binding arbitration In his decision the arbitrator only ruled on merit and damages without actually ruling on how many delay days were attributable to unforeseen weather conditions Finally, though the case study is a commercial building project, analysis of adverse weather presented in this paper can be used for other types of projects, for example, infrastructure projects Conclusions Acceptable time extensions for unusually severe weather can be difficult to establish This is a source of costly claims and disputes in construction This research has discussed some key factors that significantly affect the analysis of severe weather for time extensions They include the definition of normal weather, weather thresholds, the type of work, lingering days, criteria for lost days, lost days equivalent due to lost productivity, and the conversion from work days to calendar days lost This paper also presents an actual weather-caused delay claim to demonstrate the sensitivity and significance of those factors This case study demonstrates that the delay analysis results can be substantially different, depending on different interpretations of those factors in weather analysis In this actual case the contractor claimed 40 work days as excusable while the owner accepted only 21 calendar days The analysis provides 23 and 14 calendar days with precipitation thresholds of 0.254 and 2.54 mm, respectively The paper also illustrates that unequivocal contract terms can play a critical role in reducing such discrepancies Monthly anticipated weather delay days, along with their source, should be included in the contracts Also, a method to determine lingering days and the definition of anticipated lingering days should be clearly defined in contracts Threshold values for weather parameters should be specified in the contracts Depending on the project, weather thresholds should be provided for either the entire project or different work activities/trades Weather thresholds play a critical role when differentiating unusually severe weather from usually severe weather Contracts also need to define a method to convert a time extension from work days to calendar days Ideally, any time extension should depend on the contemporaneous time impact of the lost days caused by unusually severe weather In this case the project’s calendar must clearly and adequately define weekends, holidays and monthly anticipated weather delay days Otherwise, the contracts should provide, or at least describe, procedures to develop a seasonal weighting of days Finally, contracts should address the requisites to request a 1266 / JOURNAL OF CONSTRUCTION ENGINEERING AND MANAGEMENT © ASCE / DECEMBER 2010 Downloaded 18 May 2012 to 130.220.71.20 Redistribution subject to ASCE license or copyright Visit http://www.ascelibrary.org time extension caused by inefficiency due to unusually severe weather conditions Future research may provide a proper method for analyzing lost days equivalent as a result of lost productivity due to 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weather and determines weather thresholds for. .. regarding the foreseeability or unforeseeability of weather- related delays Weather Thresholds Inclusion of weather thresholds in construction contracts is important because they determine what qualifies... surveys or analysis of archival information Case study methodology helps us understand insight into the impacts of the factors presented above on analysis of adverse weather for excusable delays