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Trang 1Analysis 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
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共e.g., earthwork, concrete, structural
frame, roof, landscape兲 are readily affected by unexpectedly
se-vere weather while other trades共e.g., ceiling, carpet兲 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
re-spond to such risks by adopting strategies which include:
contin-gency, purchasing insurance, sharing or shifting risk to other
parties through the contract terms and conditions, to name a few
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 共Kartam 1999兲 Such delay is nor-mally excusable and noncompensable How “abnormal” is de-fined affects the amount of time extension, especially if an extremely severe weather day, for instance, is actually an excus-able delay Weather was the second leading cause of the 24 claims investigated in Canada 共Semple et al 1994兲 It was the most frequent reason for delay claims in 57 surveyed projects, presum-ably built in Canada共Yogeswaran et al 1998兲
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 con-tract 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, sub-sequently, different analyses and results
A major contribution of this paper is that it expands the analy-sis 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 共Bald-win et al 1971; Laufer and Cohenca 1990; El-Razek et al 2008兲
1
Lecturer, Faculty of Civil Engineering, Ho Chi Minh City Univ of
Technology, Ho Chi Minh City, Vietnam; formerly, Construction
Consult-ant, Jax Kneppers Associates, Inc 共JKA兲, 2125 Ygnacio Valley Rd., Suite
200, Walnut Creek, CA 94598 共corresponding author兲 E-mail:
ndlong@hcmut.edu.vn
2
President, Jax Kneppers Associates, Inc 共JKA兲, 2125 Ygnacio Valley
Rd., Suite 200, Walnut Creek, CA 94598 E-mail: a-jax@jaxkneppers.
com
3
Construction Consultant, Jax Kneppers Associates, Inc 共JKA兲, 2125
Ygnacio Valley Rd., Suite 200, Walnut Creek, CA 94598 E-mail:
borja@jaxkneppers.com
4
Professor of Construction Management, Dept of Civil and
Environ-mental Engineering, Univ of California, Berkeley, CA 94720; and
Presi-dent, 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
indi-vidual papers This paper is part of the Journal of Construction
Engi-neering and Management, Vol 136, No 12, December 1, 2010.
©ASCE, ISSN 0733-9364/2010/12-1258–1267/$25.00.
Trang 2Other research has quantified the impacts of severe weather on
productivity共Grimm and Wagner 1974; Thomas et al 1999;
El-Rayes and Moselhi 2001兲 Many studies have proposed better
practices in dealing with weather risks to construction activities
and trades, project schedules, or project costs, etc.共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
2008兲 Several studies have investigated how weather is specified
in construction contracts共Hinze and Couey 1989兲 and is ruled on
litigation cases 共Finke 1990兲 However, few studies address the
issue of differentiating unusually 共unpredictably兲 inclement
weather from usually 共predictably兲 inclement weather, because
this is a principle for classifying weather delays in typical
con-struction 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
nor-mally entitled to obtain additional time but not additional money
Specifically, a severe weather condition is an excusable delay if it:
共1兲 meets contract requirements; 共2兲 is not foreseeable; and 共3兲
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
oc-curs For instance, in Handex共2005兲, 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,关…兴 the contract clearly states that claims
for more time due to ‘abnormal weather conditions’ would only
be considered when brought ‘within the Contract Times’ 关…兴
Their request, made 10 July 2001, was well outside of the
con-tract time.” A thoughtful delay analysis would answer if a weather
delay is critical for the third principle, which is another focus of
previous research共Smith and Hancher 1989; Moselhi et al 1997;
Moselhi and El-Rayes 2002兲 Schedule delay analysis has also
been improved recently共Hegazy and Menesi 2008; Nguyen and
Ibbs 2008兲 The second principle is more ambiguous and
disput-able as discussed below
In the construction industry, “foreseeability is the standard
ap-plied to many excusable delays by courts interpreting and
apply-ing any clauses… Foreseeable delays that are often deemed
non-excusable for the contractor include delays due to normal weather
conditions”共Bramble and Callahan 2000兲 Thus, a contractor
can-not allege that all severe weather conditions are excusable delays
Severe weather conditions in excess of the total expected or
fore-seeable for the duration of the project for a given location may be
the basis for a contract time extension if the contractor can
dem-onstrate that the unexpected adverse weather delayed activities on
the critical path
In the American Institute of Architects共AIA兲 Document
A201-2007 共American Institute of Architects 2007兲, “General
Condi-tions of the Contract for Construction” 共hereafter referred to as
AIA A201兲, which is widely used in the U.S construction
indus-try, 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 construc-tion.” 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 re-sults 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 be-tween normally and abnormally severe weather conditions A clear definition of “normally anticipated weather” should exist to avoid any ambiguity共Hinze and Couey 1989兲 Some owners and contractors now provide the number of anticipated weather days
in their contracts In other words, contracts specify the average 共normal兲 number of adverse rain days for the project location Table 1 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 do 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 precipita-tion 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 共McDevitt
1989, cited in Bramble and Callahan 2000兲
With regulation number ER 415-1-15, the U.S Army Corps of Engineers关U.S Army Corps of Engineers 共USACE兲 1989兴 pro-vided 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关U.S Army Corps of Engineers 共USACE兲
1996, 2008兴 The time extension granted in calendar days, for instance, is determined differently U.S Army Corps of Engineers 共USACE兲 共1996兲 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 共USACE兲 共2008兲 instructed that it
“should be based on the new calculated early finish date as a result of the added unusually severe weather frag-net.” Inconsis-tent application of ER 41-1-15 is also recognized by the unrea-sonable evaluation of what constitutes usually severe and unusually severe weather 关U.S Army Corps of Engineers 共USACE兲 2008兴
Table 1 Average Number of Adverse Rain Delays for Santa Rosa, California
January February March April May June July August September October November December
Trang 3The definition of normally severe weather becomes more
awk-ward when contracts do not provide the number of anticipated
weather delay days Contract documents have an unclear
descrip-tion of normal weather共Smith and Hancher 1989兲 In many
con-tracts, 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 共Bramble and Callahan 2000兲 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
im-portant 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 共−23.3°C兲 or above
110° F 共43.3°C兲.” This is because efficient construction
opera-tions are difficult to achieve with those temperatures共Koehn and
Brown 1985兲 This factor is somewhat related to the definition of
normally adverse weather Intensity of rainfall, type of
construc-tion operaconstruc-tion, and on-site drying condiconstruc-tions are three key factors
affecting weather-related delays and disruptions 共El-Rayes and
Moselhi 2001兲 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共BCA兲 sometimes determine
in-consistent threshold values The National Aeronautics and Space
Administration共NASA兲 BCA once viewed the severe weather as
at least a trace共less than 0.01 in or 0.254 mm兲 of rainfall while
the Armed Services BCA共ASBCA兲 in a case rejected this
thresh-old value and used a daily severity of 0.5 in of rainfall 共Finke
1990兲 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
de-cided by ASBCA共Worthington and Goldsman 1998兲
Some contracts already determine threshold values for adverse
weather The Tennessee Department of Finance and
Administra-tion 关Tennessee Department of Finance and Administration
共TennDFA兲 2007兴, for example, establishes threshold values as
0.10 in.共2.54 mm兲 for precipitation 共rain, snow, or ice兲,
tempera-tures not above that required for the work of the day, and
sus-tained wind above 25 mi/h共40 km/h兲 for its capital projects No
single threshold value for temperature exists because the
charac-teristics of a particular work decide the range of temperature that
the work can be performed For instance, the temperature
thresh-old 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共Xi et al 2005兲
However, a weather day should be decided based on the
combi-nation of the threshold values, type of work affected, and
com-mon sense共McDonald 2000兲 Kenner et al 共1998兲 recommended that if two parties do 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 activi-ties are particularly sensitive to weather conditions共Attanasi et al 1973兲 In addition, several factors 共e.g., duration, exposure, ma-terial characteristics, equipment used, level of protection pro-vided兲 for each activity influence the activity’s sensitivity to wind, temperature, and precipitation 共Smith and Hancher 1989兲 A project’s weather sensitivity also depends on the phase of con-struction The initial site phase of building construction, for ex-ample, is usually more sensitive to weather than the dried-in phase共McDonald 2000兲 Consequently, the allocation of monthly anticipated adverse weather delay in contracts is not sufficient The scheduled activities and their sequence should be known be-fore the number of monthly weather days has been determined because the weather impact is associated with the type of activi-ties being performed共Xi et al 2005兲
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 con-ditions, drying time for soils, and accumulated water on the site 共Finke 1990兲 “Dry-out” or “mud” days are also used to describe lingering days McDonald 共2000兲 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共Finke 1990兲
Even when specifying the number of monthly normally ad-verse weather days, a contract is still ambiguous if it does not determine how to deal with lingering days Contracts should pro-vide 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 共TennDFA兲 共2007兲, adverse weather may include dry-out or mud days “at a rate no greater than 1 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 共2001兲 investigated the lingering effects of rainfall for four highway con-struction 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 Fi-nance and Administration共TennDFA兲 共2007兲 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
Trang 4Fig 1 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.共Table 1兲 The contractor was not
able to work on any rain or dry-out days Month-by-month
analy-sis is assumed to be acceptable The average number of adverse
rain delays for March and April are 10 and 6 days, respectively
共Table 1兲
Determining the number of abnormally adverse weather days
in March 2008 is not easily answered Whether the numbers
共Table 1兲 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共dates 20, 21, 26, and 31兲 in March 2008 If dry-out days are
not included, the answer is much more difficult to ascertain Table
1 would be unhelpful if dry-out days are counted prior to
differ-entiating unusually severe from usually severe Table 1 would still
be useful if only dry-out days caused by unusual rains are unusual
as in Tennessee Department of Finance and Administration
共TennDFA兲 共2007兲 The contractor would experience three
unusu-ally severe weather days 共dates 21, 26, and 31兲 in this scenario
However, the anticipated challenge is the dry-out day that rolls
over into April 2008 共date 1兲 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
con-tracts In fact, many contracts do 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 共Hinze and Couey 1989兲 To qualify as actual severe
weather delay days, U.S Army Corps of Engineers 共USACE兲
共1989兲 required that critical activities cannot be performed for
50% or more of the contractor’s scheduled work days Hinze and
Couey 共1989兲 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 共Bramble and Callahan
2000兲 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 inef-ficiency 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 se-vere weather Contractors may recover such lost days if the pre-requisites 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共Hinze and Couey 1989兲 A time extension was granted in a General Services BCA’s decision due to reduced productivity de-spite the fact that the contractor worked during the periods of unusually severe weather共Finke 1990兲 McDonald 共2000兲 recom-mended 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 Simi-larly, time extensions are typically requested and granted in cal-endar days On the other hand, adverse weather conditions are usually expressed in work days Lost days due to weather there-fore 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 共USACE兲 共1996兲 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 共Bramble and Callahan 2000兲 As a result, the seasonal weighting
of days may be used as a better mean for converting from work days to calendar days共Hinze and Couey 1989兲
As an example, a seasonal weighting approach is applied to the above case 共Table 1, Fig 1兲 This example assumes that the number of monthly anticipated severe weather共Table 1兲 includes dry-out days and that all lost days due to weather during March
2008 共Fig 1兲 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 7 days 共10 anticipated rain days multi-plied by 21 work days and divided by 31 calendar days兲 Thus, there are 14 available work days in March 2008共31 calendar days minus 10 weekend days minus 7 anticipated rain days in week-days兲 As a result, the four unusually severe weather days in
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 2 3 4
10 rain (R) days; 1 "dry-out" (D) day 3 rain (R) days, 1 "dry-out" (D) day 1 "Roll-over"
Fig 1 Rain and lingering days in March 2008
Trang 5March 2008共dates 20, 21, 26, and 31 as explained in the section
“Lingering Days”兲 in the above case would be approximately 8.9
共4⫻31/14兲 calendar days using the seasonal weighting of days
compared to only 5.6 共4⫻7/5兲 calendar days using the U.S
Army Corps of Engineers共USACE兲 共1996兲 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
do not specify an appropriate conversion mechanism Disputes
may arise if contracts do 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
关U.S Army Corps of Engineers 共USACE兲 2008兴 This is perhaps
the most appropriate and accurate approach to avoid any
confu-sion and inconsistency in the converconfu-sion, but also the most
ardu-ous
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
excus-able 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共hereafter refer
to as Project ABC兲 The original contract price and project
dura-tion were approximately $5 million and 265 calendar days,
re-spectively 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共American Institute of Architects 1997兲 General
Conditions were part of the contract Liquidated damages
amounted to $5,000 per calendar day共$5,000/day兲 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
se-vere weather The contractor complied with contract notice
re-quirements
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
erect-ing tilt-up panels, erecterect-ing and welderect-ing 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
Adverse Weather as a Part of Project Delay and Dispute
The project suffered delays The owner established that substan-tial completion was achieved in mid-December of 2006, and as-sessed liquidated damages for more than 5 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 contractor-caused 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 excus-able requires proper analysis Most importantly, the type of analy-sis 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 win-ter 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 2 and 3 illustrate the numbers of normal and actual rain days in Livermore for two precipitation thresholds: 0.254 mm 共0.01 in.兲 and 2.54 mm 共0.1
in.兲 Data sources were obtained from the National Oceanic and Atmospheric Administration共NOAA兲 共2008a,b兲 This analysis ig-nores 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共NOAA兲 共2008a兲 Naturally, weather statistics through 2005, when the con-tract actually started, would be ideal, but were not available The contract did not endorse any timeframe for defining normally ad-verse rain days
0 2 4 6 8 10 12 14 16 18
November December January February March April
Average 1971-2000 Actual 2005-2006
winter in Livermore, California
Trang 6Analysis shows that adverse weather in the winter of 2005/
2006 was actually abnormal共Figs 2 and 3兲 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共Fig 2兲 while it was normal with
pre-cipitation equal to or greater than 2.54 mm共Fig 3兲 This confirms
that threshold values define how unusual a severe weather
condi-tion is For Project ABC the winter of 2005/2006 was categorized
as abnormal under both circumstances Cumulative precipitations
also support that abnormality共Fig 4兲 The precipitations for
De-cember 2005 and March 2006 exceeded the average precipitation
by 165 and 94%, respectively The actual total precipitation for
2005/2006 winter共November 2005 to April 2006兲 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
weather-related lost days were rejected by the owner The contractor
ac-cordingly revised the delay notices and removed twelve of the
fifteen lost days rejected by the owner The contractor still
main-tained his view with respect to three lost days that the owner did
not agree with That is, there were forty共52−12兲 lost days 共in-cluding three disputable lost days兲 timely notified and recorded at the end of the contract共Table 2兲
Fig 5 illustrates the flowchart for analyzing adverse weather and Table 2 summarizes the analysis Columns共2兲 and 共3兲 are the lost days that the contractor notified to the owner Three alleged lost days January 13, February 6 and 7, 2006 were not agreed to
by the owner关noted as “dispute” in Column 共12兲兴 An indepen-dent 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 6 and 7 were likely not lost days due to mud A subcontractor’s daily report shows that the concrete sub-contractor 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共erect tilt-up panels兲 could not be performed because a crane was not available Analysis of concurrent delays was not necessary be-cause weather was not a be-cause on these lost work days The independent review also revealed that December 26, 2005 共Mon-day兲 was not a lost day due to weather although heavy rain oc-curred that day Daily logs revealed that Christmas Day ococ-curred
on Sunday, December 25, 2005 and was moved to Monday, De-cember 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 2 have the following mean-ings Column共4兲 describes the type of lost day that the contractor documented in its notices The two types were “rain” and mud共or dry-out兲 Precipitation amounts 关Column 共5兲兴 were obtained from National Oceanic and Atmospheric Administration 共NOAA兲 共2008b兲 Column 共6兲 shows the equivalent precipitation in milli-meters 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共0.25 mm兲, February 1 共0.51 mm兲, and February 2 共1.27 mm兲
of 2006 In contrast, the contractor still worked on layout, forms, and rebar of tilt panels on days with similar or higher precipita-tion during work hours; e.g., March 24共0.76 mm兲 and March 28 共1.78 mm兲 of 2006 共not shown in Table 2 because these 2 days were not notified as lost days兲 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 thresh-olds for different activities
Given the relationship between precipitation and lost days by rain in this case, Columns 共7兲 and 共8兲 count the chronological order for a particular rain day for a given month for the selected thresholds: 0.254 mm 共0.01 in.兲 and 2.54 mm 共0.1 in.兲, respec-tively For instance, the rain on December 21, 2005 was the ninth 共fifth兲 rain day with a precipitation of 0.254 共2.54兲 mm or greater for that month Column共9兲 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共average兲 number of rain days presented in Figs 2 and 3 For example, using the threshold of 0.254 mm, the rain on December 21, 2005 was considered abnormal 共“yes”兲 because it was the ninth rain day in December of 2005 while 8 days of rain were anticipated
0
2
4
6
8
10
12
14
November December January February March April
Average 1971-2000 Actual 2005-2006
winter in Livermore, California
0
20
40
60
80
100
120
140
160
November December January February March April
Average 1971-2000 Actual 2005-2006
Fig 4 Average and actual precipitations in winter in Livermore,
California
Trang 7for that month using the same threshold共Fig 2兲 However, that
rain day would not be abnormal共“no”兲 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 do not have precipitation, the analysis used above does
not apply Instead, this analysis adopts the method proposed by Tennessee Department of Finance and Administration共TennDFA兲 共2007兲 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
Table 2 Analysis of Adverse Weather for Project ABC, Livermore, California
Number
共1兲
Notified lost day Type oflost day
共4兲
Precipitation ith rain dayb
Abnormal 共9兲 Critical共10兲 Excusable共11兲 Remark共12兲
in.a 共5兲 mm共6兲
ⱖ0.254 ⱖ2.54 mm
共7兲 mm共8兲
1 Friday November 4, 2005 Rain 0.08 2.03 1 1 No 共no兲 d
n/a 共n/a兲 No 共no兲
2 Tuesday November 29, 2005 Rain 0.48 12.19 4 1 No 共no兲 n/a 共n/a兲 No 共no兲
3 Thursday December 1, 2005 Rain 0.27 6.86 1 1 No 共no兲 n/a 共n/a兲 No 共no兲
4 Friday December 2, 2005 Mud 0.20 5.08 2 2 No 共no兲 n/a 共n/a兲 No 共no兲
5 Monday December 19, 2005 Mud 0.05 1.27 7 n/a No 共no兲 n/a 共n/a兲 No 共no兲
6 Tuesday December 20, 2005 Mud 0.01 0.25 8 n/a No 共no兲 n/a 共n/a兲 No 共no兲
7 Wednesday December 21, 2005 Rain 0.27 6.86 9 5 Yes 共no兲 Yes 共n/a兲 yes 共no兲
8 Thursday December 22, 2005 Rain 0.38 9.65 10 6 Yes 共yes兲 Yes 共yes兲 Yes 共yes兲
9 Friday December 23, 2005 Mud 0.00 0.00 n/ac n/a Yes 共yes兲 Yes 共yes兲 Yes 共yes兲
10 Monday December 26, 2005 Rain 0.37 9.40 12 8 n/a 共n/a兲 n/a 共n/a兲 n/a 共n/a兲 Holiday
11 Wednesday December 28, 2005 Rain 0.23 5.84 13 9 Yes 共yes兲 Yes 共yes兲 Yes 共yes兲
12 Tuesday January 3, 2006 Rain 0.02 0.51 2 n/a No 共no兲 n/a 共n/a兲 No 共no兲
13 Wednesday January 4, 2006 Mud 0.00 0.00 n/a n/a No 共no兲 n/a 共n/a兲 No 共no兲
14 Thursday January 5, 2006 Mud 0.00 0.00 n/a n/a No 共no兲 n/a 共n/a兲 No 共no兲
15 Friday January 13, 2006 Mud 0.00 0.00 n/a n/a No 共no兲 n/a 共n/a兲 No 共no兲 Dispute
16 Friday January 27, 2006 Rain 0.01 0.25 8 n/a No 共no兲 n/a 共n/a兲 No 共no兲
17 Monday January 30, 2006 Rain 0.16 4.06 11 5 Yes 共no兲 Yes 共n/a兲 yes 共no兲
18 Tuesday January 31, 2006 Mud 0.00 0.00 n/a n/a Yes 共no兲 Yes 共n/a兲 yes 共no兲
19 Wednesday February 1, 2006 Rain 0.02 0.51 1 n/a No 共no兲 n/a 共n/a兲 No 共no兲
20 Thursday February 2, 2006 Rain 0.05 1.27 2 n/a No 共no兲 n/a 共n/a兲 No 共no兲
21 Friday February 3, 2006 Mud 0.00 0.00 n/a n/a No 共no兲 n/a 共n/a兲 No 共no兲
22 Monday February 6, 2006 Mud 0.00 0.00 n/a n/a No 共no兲 n/a 共n/a兲 No 共no兲 Dispute
23 Tuesday February 7, 2006 Mud 0.00 0.00 n/a n/a No 共no兲 n/a 共n/a兲 No 共no兲 Dispute
24 Monday February 27, 2006 Rain 0.21 5.33 8 4 No 共no兲 n/a 共n/a兲 No 共no兲
25 Tuesday February 28, 2006 Rain 0.44 11.18 9 5 No 共no兲 n/a 共n/a兲 No 共no兲
26 Wednesday March 1, 2006 Mud 0.00 0.00 n/a n/a No 共no兲 n/a 共n/a兲 No 共no兲
27 Thursday March 2, 2006 Rain 0.19 4.83 1 1 No 共no兲 n/a 共n/a兲 No 共no兲
28 Friday March 3, 2006 Rain 0.24 6.10 2 2 No 共no兲 n/a 共n/a兲 No 共no兲
29 Monday March 6, 2006 Rain 0.54 13.72 3 3 No 共no兲 n/a 共n/a兲 No 共no兲
30 Tuesday March 7, 2006 Rain 0.12 3.05 4 4 No 共no兲 n/a 共n/a兲 No 共no兲
31 Tuesday March 14, 2006 Rain 0.31 7.87 9 8 No 共yes兲 n/a 共yes兲 No 共yes兲
32 Friday March 17, 2006 Rain 0.64 16.26 10 9 No 共yes兲 n/a 共yes兲 No 共yes兲
33 Wednesday March 29, 2006 Rain 0.30 7.62 17 14 Yes 共yes兲 Yes 共yes兲 Yes 共yes兲
34 Monday April 3, 2006 Rain 0.37 9.40 3 1 No 共no兲 n/a 共n/a兲 No 共no兲
35 Tuesday April 4, 2006 Rain 0.95 24.13 4 2 No 共no兲 n/a 共n/a兲 No 共no兲
36 Wednesday April 5, 2006 Rain 0.21 5.33 5 3 No 共no兲 n/a 共n/a兲 No 共no兲
37 Wednesday April 12, 2006 Rain 0.31 7.87 10 5 Yes 共yes兲 Yes 共yes兲 Yes 共yes兲
38 Thursday April 13, 2006 Mud 0.01 0.25 11 n/a Yes 共yes兲 Yes 共yes兲 Yes 共yes兲
39 Monday April 17, 2006 Rain 0.07 1.78 14 n/a Yes 共no兲 Yes 共n/a兲 Yes 共no兲
40 Tuesday April 18, 2006 Mud 0.00 0.00 n/a n/a Yes 共no兲 Yes 共n/a兲 Yes 共no兲
Note: n /a=not applicable.
a
Precipitation obtained from National Oceanic and Atmospheric Administration 共NOAA兲 共2008b兲.
b
The order of a rain day in a particular month when rain is defined by precipitation.
c
n/a in Columns 共7兲 and 共8兲, Columns 共9兲 and 共11兲, and Column 共10兲 stands for “no rain” by definition, “not a lost day,” and “not check” if not abnormal, respectively.
d
In Columns共9兲–共11兲, x共y兲 is the corresponding outcome per Column 共7兲 关Column 共8兲兴.
Trang 8on January 30, 2006 and earlier days Conversely, the same day
would be normal with a threshold of 2.54 mm Column 共10兲
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共11兲 shows if a qualified lost day is excusable 共yes兲 or
inexcusable共no兲 A qualified lost day is excusable only if it was
abnormal and critical In other words, yes must appear on both
Columns共9兲 and 共10兲
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共Table 2兲
These work days lost due to abnormal weather need to be converted into calendar days As previously discussed, three al-ternatives for the conversion include the fixed conversion factor 共7/5兲, 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 共U.S holidays, union holidays, anticipated weather days兲 Using the conversion factor of 7/5, the time extension would be approxi-mately 15 calendar days for the precipitation threshold of 0.254
mm and 11 calendar days for the precipitation threshold of 2.54
mm关hereafter 15 共11兲 calendar days for the precipitation thresh-old of 0.254共2.54兲 mm兴
Table 3 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 共14兲 calendar days for the precipitation threshold value of 0.254共2.54兲 mm 共Table 3兲 The number of excusable lost days共expressed in work days兲 for a particular month in Table 3 equals to the number of yes in Column 11 of Table 2 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共Table 2兲 The difference in time extension for the two alternatives is eight 共three兲 calendar days for the different weather thresholds The difference in liquidated damages assessed is $40,000 共$15,000兲, which can be a signifi-cant 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 defi-nitions 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共TennDFA兲 共2007兲 the above analysis presumes that mud days caused by normally se-vere 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,
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F#-Fig 5 Flowchart of adverse weather analysis
Table 3 Calendar Days Lost Using the Seasonal Weighting of Days
Month
Available work daysa
Calendar days
Excusable lost daysa共work day兲 Excusable lost daysa共calendar day兲
a
Available work days, lost days 共work or calendar day兲 based on thresholds 共0.254 mm or 2.54 mm兲.
Trang 9lingering days that roll over to a following month are still
chal-lengeable The mud day on March 1, 2006 was caused by
con-secutive 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共Table 2兲
Another conclusion is that contracts should specify monthly
anticipated severe weather delay days Contractors should
ac-count for those days when planning their work and preparing their
baseline schedules At best, these delay days should include
an-ticipated 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
con-tract 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
predeter-mined 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 day共s兲 ideally will
be agreed to by the involved parties If not, the threshold together
with the type of work scheduled, work quality required, the
por-tion of work performed, site condipor-tions, and so on will decide lost
days
In any circumstance, threshold values for different weather
conditions共e.g., rain/snow, wind, temperature兲 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 do not agree as mentioned, but also are a baseline for
counting actual adverse days in a particular month关Columns 共7兲
and共8兲 in Table 2兴 Consequently, whether a lost day is abnormal
is fairly determined
Conversion from work days lost to calendar days lost is
an-other issue to be addressed in contracts We believe the
conver-sion method proposed by U.S Army Corps of Engineers
共USACE兲 共2008兲 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
There-fore, 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共USACE兲 共2008兲
or the seasonal weighting of days to avoid confusion and
specu-lation
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 signifi-cantly 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 excus-able delays The owner on the other hand accepted only 21 cal-endar 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 exten-sions 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, respec-tively
The paper also illustrates that unequivocal contract terms can play a critical role in reducing such discrepancies Monthly an-ticipated 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 param-eters should be specified in the contracts Depending on the project, weather thresholds should be provided for either the en-tire 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 contem-poraneous time impact of the lost days caused by unusually se-vere 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
Trang 10time 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 adverse weather Analysis presented in this paper does not
quantify the impacts of lost productivity caused by severe weather
on the allowable number of lost days
References
American Institute of Architects 共1997兲 “General conditions of the
con-tract for construction.” Document A201-1997, Washington, D.C.
American Institute of Architects 共2007兲 “General conditions of the
con-tract for construction.” Document A201-2007, Washington, D.C.
Attanasi, E D., Johnson, S R., LeDuc, S., and McQuigg, J D 共1973兲.
“Forecasting work conditions for road construction activities: An
ap-plication of alternative probability models.” Mon Weather Rev.,
101 共3兲, 223–230.
Baldwin, J R., Manthei, J M., Rothbart, H., and Harris, R B 共1971兲.
“Causes of delay in the construction industry.” J Constr Div., 97共2兲,
177–187.
Benjamin, N B H., and Greenwald, T W 共1973兲 “Simulating effects of
weather on construction.” J Constr Div., 99共1兲, 175–190.
Bramble, B B., and Callahan, M T.共2000兲 Construction delay claims,
3rd Ed., Aspen Law & Business, New York.
Chan, E H W., and Au, M C Y 共2008兲 “Relationship between
organi-zational sizes and contractors’ risk pricing behaviors for weather risk
under different project values and durations.” J Constr Eng
Man-age., 134共9兲, 673–680.
Connors, R B 共2003兲 “Weather derivatives allow construction to hedge
weather risk.” Coastal Eng., 45共3兲, 21–24.
El-Rayes, K., and Moselhi, O 共2001兲 “Impact of rainfall on the
produc-tivity of highway construction.” J Constr Eng Manage., 127共2兲,
125–131.
El-Razek, M E A., Bassioni, H A., and Mobarak, A M 共2008兲 “Causes
of delay in building construction projects in Egypt.” J Constr Eng.
Manage., 134共11兲, 831–841.
Finke, M R 共1990兲 “Weather-related delays on government contracts.”
Proc., AACE Int Transactions of the Annual Meetings, The
Associa-tion for the Advancement of Cost Engineering InternaAssocia-tional 共AACEI兲,
Morgantown, W.Va.
Grimm, C T., and Wagner, N K 共1974兲 “Weather effects on mason
productivity.” J Constr Div., 100共3兲, 319–335.
Handex of the Carolinas, Inc v County of Haywood, and Municipal
Engineering Services Company, P.A., No COA03-1658共Court of
Ap-peals of North Carolina 2005 兲.
Hegazy, T., and Menesi, W 共2008兲 “Delay analysis under multiple
base-line updates.” J Constr Eng Manage., 134共8兲, 575–662.
Hinze, J., and Couey, J.共1989兲 “Weather in construction contracts.” J.
Constr Eng Manage., 115共2兲, 270–283.
Kartam, S.共1999兲 “Generic methodology for analyzing delay claims.” J.
Constr Eng Manage., 125共6兲, 409–419.
Kenner, S., Johnson, R L., Miller, J R., Salmen, J A., and Matt, S A.
共1998兲 “Development of working day weather charts for
transporta-tion constructransporta-tion in South Dakota, study SD97-07.” Technical Rep.,
South Dakota Dept of Transportation, Pierre, S.D.
Koehn, E., and Brown, G.共1985兲 “Climatic effects on construction.” J.
Constr Eng Manage., 111共2兲, 129–137.
Laufer, A., and Cohenca, D 共1990兲 “Factors affecting construction
plan-ning outcomes.” J Constr Eng Manage., 116共1兲, 135–156 Maunder, W J., Johnson, S R., and McQuigg, J D 共1971兲 “Study of the
effect of weather on road construction: A simulation model.” Mon.
Weather Rev., 99共12兲, 939–945.
McDevitt & Street Co v Marriott Corp., 713 F Supp 906关U.S District Court Eastern District of Virginia 共E.D Va.兲 1989兴.
McDonald, D F. 共2000兲 “Weather delays and impacts.” Cost Eng.,
42 共5兲, 34–39.
Moselhi, O., and El-Rayes, K 共2002兲 “Analyzing weather-related
con-struction claims.” Coastal Eng., 44共8兲, 12–19.
Moselhi, O., Gong, D., and El-Rayes, K 共1997兲 “Estimating weather
impact on the duration of construction activities.” Can J Civ Eng.,
24 共3兲, 359–366.
National Oceanic and Atmospheric Administration 共NOAA兲 共2008a兲.
Climatography of the United States no 20 1971-2000: Livermore, CA station, Asheville, N.C., 具http://cdo.ncdc.noaa.gov/climatenormals/ clim20/ca/044997.pdf 典 共Nov 8, 2008兲.
National Oceanic and Atmospheric Administration 共NOAA兲 共2008b兲.
Record of river and climatological observations: Livermore, CA sta-tion, Asheville, N.C., 具http://www7.ncdc.noaa.gov/IPS/coop/ coop.html 典 共Nov 8, 2008兲.
Nguyen, L D., and Ibbs, W 共2008兲 “FLORA: New forensic schedule
analysis technique.” J Constr Eng Manage., 134共7兲, 483–491 Semple, C., Harman, F T., and Jergeas, G 共1994兲 “Construction claims
and disputes: Causes and cost/time overruns.” J Constr Eng
Man-age., 120共4兲, 785–795.
Smith, G R., and Hancher, D E 共1989兲 “Estimating precipitation
im-pacts for scheduling.” J Constr Eng Manage., 115共4兲, 552–566 Tennessee Department of Finance and Administration 共TennDFA兲.
共2007兲 “Section 01 26 20—Weather delays.” Designer’s manual,
Nashville, Tenn.
Thomas, H R., Riley, D R., and Sanvido, V E 共1999兲 “Loss of labor
productivity due to delivery methods and weather.” J Constr Eng.
Manage., 125共1兲, 39–46.
U.S Army Corps of Engineers 共USACE兲 共1989兲 “Construction time
extensions for weather.” Regulation No ER 415-1-15, Vicksburg,
Miss.
U.S Army Corps of Engineers 共USACE兲 共1996兲 “Developing and
ana-lyzing adverse weather data.” Construction Bulletin No 96-13,
Vicks-burg, Miss.
U.S Army Corps of Engineers 共USACE兲 共2008兲 “Developing, analyzing and implementing adverse weather policy for construction contracts.”
Engineering and Construction Bulletin No 2008-23, Vicksburg, Miss.
Worthington, M M., and Goldsman, L P.共1998兲 Contracting with the
federal government, 4th Ed., Wiley, New York.
Xi, Y., Balaji, R., and Molenaar, K. 共2005兲 Quantifying construction
delays due to weather, Federal Highway Administration, Central
Fed-eral Lands Highway Div., Lakewood, Colo.
Yogeswaran, K., Kumaraswamy, M M., and Miller, D R A 共1998兲.
“Claims for extensions of time in civil engineering projects.” Constr.
Manage Econom., 16共3兲, 283–293.