Weather Delays When Should They Be Granted? If Weather Data is Normally Distributed, When Is the Weather Abnormal? Marty Cuerdon Senior Consultant 1
Weather Delays Normally Excusable but not Compensable (Contractor gets time but no money.) Exceptions (when weather delays = $): Liquidated Damages Owner delay pushed work into inclement weather. 2
Weather Delays Contractor has the burden of proving three conditions 1. The weather condition was adverse, i.e., it impacted construction operations. 2. The weather was unusual, i.e., it could not have been foreseen by the contractor. 3. The completion date was impacted by the delay, i.e., critical path activities were delayed. 3
Weather Delays Two Types of Weather Delays Generally Recognized 1. Direct impact Scheduled activity not performed because of an adverse weather event, i.e., workers sent home. 2. Indirect impact Scheduled activity duration extended due to the effects of an adverse weather event, i.e., lowered worker productivity during the weather event and/or lingering effect of the event. 4
Weather Delays Applicable Weather Events Temperatures (High, Low, Threshold Frequencies) Precipitation (Amounts, Effects, Frequencies) Snowfall (Amount, Duration, Impact on Operations) High Wind (Dust, Impact on Crane Operations, Painting) 5
Weather Delays Contractually Shared Risk Contractor assumes the risk of delays due to normal weather conditions. Owner and Contractor each assume the cost of their individual extended overhead costs due to delays from abnormal weather conditions. 6
Weather Delay Contract Language: AIA 201 (1997 ed.) 4.3.7.2 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 impact on the construction schedule. 7
Weather Delay Contract Language: Federal Acquisition Regulation (48 CFR 52.249-10(b)) (b) The Contractor s right to proceed shall not be terminated nor the Contractor charged with damages under this clause, if (1) The delay in completing the work arises from unforeseeable causes beyond the control and without the fault or negligence of the Contractor. Examples of such causes include (i) acts of God or of the public enemy, (v) floods, [or] (x) unusually severe weather. 8
Weather Delay Contract Language: USACoE Regulation 415-1-15 Definitions.... b. Unusually severe weather weather that is more severe than the adverse weather anticipated for the season or location involved. 9
Weather Delays Undefined Threshold In the absence of specific contractual guidelines, however, it may be difficult to determine in advance the point at which adverse weather satisfies the threshold requirement for becoming an excusable delay. Under typical contract language, there is no bright-line rule, and an excusable delay is generally one triggered by events that are not self-defining, such as unusually severe, adverse, or abnormal weather conditions. (Bret Gunnell, Adverse Weather and the Construction Process, Construction Briefings No. 98-6) 10
New Weather Delay Methodology? Analytical Challenges 1. Contractually define a bright line boundary between normal weather and abnormal weather. 2. Calibrate the results of the methodology to adjust to the amount of risk the parties have negotiated. 11
New Weather Delay Methodology Probability statistics can be used to calculate adverse weather recurrence intervals in the same way the 100 Year Flood is calculated. Contractual Weather Delay language could be modified to define the specific recurrence interval. (10 Years, 20 Years, etc.) 12
50% 45% Standard Normal Probability Distributions 100% 90% Instant Probability 40% 35% 30% 25% 20% 15% 10% 80% 70% 60% 50% 40% 30% 20% Cumulative Probability 5% 10% 0% -5-4.5-4 -3.5-3 -2.5-2 -1.5-1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0% No. of Standard Deviations From the Mean 13
40% Standard Normal Probability Distribution 35% 30% 50% Area = +/- 0.674 Std Dev Probability 25% 20% 75% Area = +/- 1.150 Std Dev 15% 10% 5% 90% Area = +/- 1.645 Std Dev 95% Area = +/- 1.960 Std Dev 99% Area = +/- 2.576 Std Dev 0% -4-3 -2-1 0 1 2 3 4 Number of Standard Deviations From Mean Value 14
September October November December -20-10 0 10 20 30 40 50 60 70 80 90 100 125 100 75 50 25 0 175 No. of Occurances 150 Month August July June May April March Histogram of Daily Mean Temperature Mean Temp February Denver, Colorado Source: Stapleton NWS 1948-2001 January 15
August Daily Mean Temperatures, Denver Colorado 1948-2001 Source: NWS Stapleton Airport 175 150 Descriptive Statistics Number of Occurences 125 100 75 No. of Observations = 1673 Average Mean Temp = 71.91 Modal Mean Temp = 73 Medial Mean Temp = 72 Standard Deviation = 4.67 Skew of Distribution = -0.53 Correlation to Normal = 98.71% Confidence Intervals Standard Normal Curve 50 50% - 68.8-75.1 75% - 66.5-77.3 90% - 64.2-79.6 95% - 62.8-81.1 99% - 59.9-83.9 25 0-20 -10 0 10 20 30 40 50 60 70 80 90 Daily Mean Temperatures (Degrees F) 16
Number of Occurrences 9 8 7 6 5 4 3 2 1 0 August Monthly Precipitation Denver, Colorado Source: NWS Stapleton Airport 1948-2001 0 1 2 3 4 5 6 7 8 9 10 Monthly Precipitation (Inches) Descriptive Statistics No. of Observations = 54 Avg Monthly Precipitation = 1.60 Median Monthly Precipitation = 1.23 Standard Deviation = 1.273 Skew of Distribution = 2.16 Correlation to Normal = 82.70% 17
Weather Delay Recurrence Interval Mathematical Formula Recurrence Interval = 1 / (1-Cumulative Probability) Example 100 Year Recurrence Interval = 1 / (1 0.99) Formula with Excel Spreadsheet Probability Function Recurrence Interval = 1/(1 - NORMINV(probability,mean,standard_dev,TRUE)) (10 Year Probability = 0.90, 20 Year = 0.95, 50 Year = 0.98, 100 Year = 0.99) 18
Daily Maximum Temperatures Daily Mean Temperatures Daily Minimum Temperatures Monthly Sum of Cooling Degree Days (Base=65F) Monthly Sum of Heating Degree Days (Base=65F) Monthly Sum of Precipitation Monthly Sum of Snowfall Stapleton Airport, Denver, Colorado, Weather Data (1948-2001) Monthly Data Summaries Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Highest Daily Max 74 76 84 90 95 104 103 100 97 89 79 75 Highest Monthly Mean Max 55 60 61 70 79 90 92 91 83 77 65 55 Lowest Monthly Mean Max 29 33 40 52 60 73 82 81 68 50 40 28 Avg Daily Max 43.5 46.9 52.3 61.3 70.8 81.6 87.9 85.9 77.5 66.4 52.4 45.2 Std Dev 5.42 5.50 4.78 4.36 3.84 4.02 2.38 2.28 3.52 4.29 5.08 4.68 Max Daily Mean 40 44 47 56 63 74 77 75 68 60 49 41 Min Daily Mean 16 22 29 41 50 61 69 68 56 39 30 17 Avg Daily Mean 30.1 33.7 39.1 47.8 57.5 67.2 73.4 71.7 62.9 51.6 38.9 31.9 Std Dev 5.02 4.56 3.83 3.51 2.82 3.16 1.95 1.77 2.92 3.12 3.92 4.13 Lowest Daily Min -25-25 -10-2 22 30 43 41 17 3-8 -21 Highest Monthly Mean Min 26 28 33 43 49 58 63 61 54 43 32 27 Lowest Monthly Mean Min 4 12 18 28 39 48 55 53 42 28 19 7 Avg Daily Min 16.7 20.6 25.9 34.4 44.1 52.9 58.9 57.4 48.2 36.9 25.4 18.6 Std Dev 4.87 4.00 3.39 3.01 2.37 2.64 2.01 1.90 2.70 2.50 3.05 3.87 Max - - 1 19 60 263 376 327 133 15 - - Min - - - - - 9 135 123 18 - - - Avg - - 0 1 18 130 273 221 67 2 - - Std Dev - - 0.14 3.17 15.17 59.58 57.22 49.43 31.04 3.59 - - Max 1,502 1,190 1,108 712 457 164 42 35 273 801 1,051 1,466 Min 758 589 548 260 104 - - - 19 159 482 731 Avg 1,075 876 796 509 244 57 5 7 123 410 775 1,013 Std Dev 155.55 130.33 118.61 103.80 76.69 40.03 8.09 8.74 64.66 95.19 117.59 126.63 Max 1.44 1.66 4.56 5.35 7.31 4.69 6.99 5.85 4.67 4.17 2.67 2.84 Min 0.01 0.01 0.18 0.03 0.06 0.09 0.50 0.06 0.01 0.05 0.01 0.03 Avg 0.54 0.60 1.26 1.82 2.49 1.71 2.03 1.59 1.16 0.98 0.87 0.56 Std Dev 0.370 0.401 0.843 1.062 1.586 1.149 1.487 1.268 0.963 0.904 0.555 0.520 Max 24.3 18.3 30.5 25.5 13.7 0.8-1.3 17.2 31.2 29.6 30.8 Min 0.3 0.3 2.1 - - - - - - - - 0.6 Avg 8.0 7.4 12.7 8.9 1.6 0.0-0.0 1.7 4.1 9.2 7.6 Std Dev 5.75 5.00 7.06 6.14 3.36 0.13-0.18 3.47 5.61 6.79 6.36 19
No. of Days with Temperatures >100 Degrees No. of Days with Temperatures > 90 Degrees No. of Days with Maximum Temperatures < 32 Degrees No. of Days with Minimum Temperatures < 32 Degrees No. of Days with Minimum Temperatures < 0 Degrees No. of Days with Precipitation > 0.01 Inches No. of Days with Precipitation > 0.10 Inches No. of Days with Precipitation > 0.50 Inches No. of Days with Precipitation > 1.00 Inches Stapleton Airport, Denver, Colorado, Weather Data (1948-2001) Monthly Frequency Summaries Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Max - - - - - 3.0 5.0 - - - - - Min - - - - - - - - - - - - Avg - - - - - 0.1 0.2 - - - - - Std Dev - - - - - 0.45 0.79 - - - - - Max - - - - 3.0 13.0 26.0 20.0 7.0 - - - Min - - - - - - 1.0 - - - - - Avg - - - - 0.3 5.9 12.7 7.5 1.9 - - - Std Dev - - - - 0.79 3.73 5.28 4.52 1.93 - - - Max 19 12 9 4 - - - - 1 2 10 14 Min - - - - - - - - - - - - Avg 5.8 3.9 2.4 0.3 - - - - 0.0 0.3 2.2 4.3 Std Dev 4.05 2.95 2.11 0.75 - - - - 0.14 0.59 1.89 2.95 Max 31 29 30 20 5 1-3 11 20 29 31 Min 20 19 12 2 - - - - - 1 12 22 Avg 28.9 25.3 22.8 10.2 0.9 0.0-0.1 0.8 7.3 22.8 28.7 Std Dev 2.18 2.53 4.33 4.64 1.22 0.14-0.49 1.94 4.70 4.19 2.54 Max 11 8 4 1 - - - - - - 4 11 Min - - - - - - - - - - - - Avg 2.9 1.4 0.5 0.0 - - - - - - 0.3 1.8 Std Dev 3.16 2.02 0.97 0.14 - - - - - - 0.80 2.40 Max 10 13 15 14 16 16 15 13 12 12 14 11 Min - - 2 1 1 1 3 2-1 - 1 Avg 4.6 4.8 7.2 7.4 9.1 7.4 7.9 7.4 5.4 4.3 4.9 4.6 Std Dev 2.06 2.47 3.06 2.94 3.27 3.14 3.03 2.48 2.93 2.42 2.55 2.24 Max 5 5 7 10 11 10 11 8 9 8 6 6 Min - - 1 - - - 1 - - - - - Avg 1.4 1.8 3.5 4.2 4.9 3.8 3.9 3.4 2.7 2.5 2.5 1.7 Std Dev 1.21 1.37 1.71 2.00 2.53 2.09 2.10 2.16 2.10 1.85 1.55 1.41 Max 1 1 3 3 5 3 6 7 4 4 3 2 Min - - - - - - - - - - - - Avg 0.1 0.1 0.4 0.9 1.4 0.8 1.1 0.8 0.5 0.5 0.3 0.1 Std Dev 0.29 0.26 0.68 0.87 1.25 0.91 1.23 1.18 0.84 0.88 0.64 0.35 Max - 1 2 2 2 1 4 2 1 1-1 Min - - - - - - - - - - - - Avg - 0.0 0.1 0.2 0.5 0.2 0.5 0.3 0.1 0.1-0.0 Std Dev - 0.14 0.37 0.45 0.64 0.42 0.84 0.56 0.36 0.29-0.19 20
Weather Delays Recurrence Interval Methodology Example: Denver s electric utility company wanted an excusable delay for installing an underground service connection because the high number of 90+ Degree days in the Summer of 2001. The weather caused high electric power demand, strained the electrical distribution system, created lots of outages and diverted their distribution crews from completing their underground service connection. 21
Historical Monthly 90 Degree Days vs 2001 Denver Colorado 1948-2001 30 53 Year High 25 Monthly Days Exceeding 90 Degrees F 20 15 10 53 Yr Low 2001 +/- One Standard Deviation 53 Yr Avg 5 0 Jan Feb Mar Apr 1948-2000 Historical Data: No. of Days with temperatures > 90 Degrees May Jun Jul Aug Sep June July August 3 Month Total Max 13 26 20 47 Min - 1-3 Avg 5.8 12.6 7.5 25.9 St. Dev 3.7 5.3 4.5 9.2 2001 Actual Data: No. of Days with temperatures > 90 Degrees 12 18 12 42 Calculated Recurrence Interval (Years) 21.9 6.6 6.3 25.3 5 6 5 5 16 No. of Excusable Days Based 10 6 - - 16 On Recurrence Interval (Year) 20 6 - - 16 Threshold of: 25 - - - 16 30 - - - - Oct Nov Dec 22
Weather Delays 2 nd Recurrence Interval Methodology Example: Should contractors be granted excusable delays for Denver s historical March 2003 Blizzard? 23
Colorado's Worst Blizzard in 90 years! Up to 7 Feet of Snow!! March 17-19, 2003 (DENVER) - Governor Bill Owens announced today that President Bush has approved Owens' request for federal assistance to help financially-strapped cities and counties defray large portions of the costs of snow removal during the state's March blizzard. 24
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Denver's March 2003 Monthly SummaryDenver's March 2003 Monthly Summary (How to read this form) *****FOR UNOFFICIAL USE ONLY***** **THIS DATA AVAILABLE ON THE INTERNET: http://www.crh.noaa.gov/den** **The National Climatic Data Center (NCDC: http://www.ncdc.noaa.gov) is the official source of climate data** Preliminary Local Climatological Data (WS Form: F-6) Station: DENVER INTERNATIONAL AIRPORT Month: MARCH Year: 2003 39.52N = Latitude 104.40W = Longitude Gnd Elev. 5431 ft Std Time: MST Temperature in Fahrenheit :Precip : Snow :Wind :Fastest 2-Min: Sunshine : Sky :Peak Wind Columns -1- -2- -3- -4- -5- -6a-6b- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- Day Max Min Avg Dep. HDD CDD Water Snow Depth Avg. Speed Dir Mins. %PSBL SR-SS Weather Speed Dir 1 36 21 29-7 36 0 T M M 11.9 22 20 181 27% 1,8 26 20 2 46 13 30-6 35 0 T M M 8.1 16 270 489 72% 1 21 300 3 52 28 40 3 25 0 0.00 M M 12.0 30 300 462 68% 36 280 4 33 8 21-16 44 0 0.05 M M 9.7 18 50 0 0% 1,2 21 50 5 41 7 24-13 41 0 T M M 10.8 31 280 467 68% 1,2 36 270 6 56 26 41 4 24 0 0.00 M M 12.9 38 280 302 44% 44 280 7 61 23 42 5 23 0 0.00 M M 8.1 20 310 427 62% 26 140 8 63 28 46 8 19 0 0.00 M M 14.8 33 280 420 60% 39 270 9 62 29 46 8 19 0 0.00 M M 11.9 30 280 387 55% 35 280 10 64 32 48 10 17 0 0.00 M M 8.2 15 50 293 42% 22 110 11 66 37 52 14 13 0 0.00 M M 13.8 32 270 378 54% 37 270 12 68 39 54 15 11 0 0.00 M M 11.7 25 280 377 53% 8 33 260 13 74 31 53 14 12 0 0.00 M M 9.6 17 230 446 63% 8 22 220 14 75 44 60 21 5 0 0.00 M M 10.7 21 210 181 25% 8 23 290 15 67 42 55 16 10 0 0.00 M M 10.2 22 290 568 80% 8 24 210 16 64 37 51 11 14 0 0.00 M M 8.4 23 190 648 91% 26 180 17 50 34 42 2 23 0 0.53 M M 14.7 26 360 126 18% 8,3,1 33 340 18 39 28 34-6 31 0 1.53 M M 23.4 37 360 0 0% 1,2 41 360 19 33 27 30-10 35 0 0.74 M M 16.3 32 350 0 0% 1 38 350 20 36 26 31-10 34 0 0.00 M M 6.1 12 70 450 62% 13 60 21 41 30 36-5 29 0 0.03 M M 7.4 16 210 600 82% 1,2 17 210 22 42 30 36-5 29 0 0.00 M M 13.8 18 200 581 79% 20 200 23 54 32 43 2 22 0 0.00 M M 12.8 21 200 680 93% 24 220 24 40 31 36-5 29 0 0.09 M M 6.9 15 340 187 25% 1,2 17 340 25 41 28 35-7 30 0 0.00 M M 9.3 18 210 701 95% 1 21 210 26 60 32 46 4 19 0 0.08 M M 12.4 32 350 692 93% 1 39 340 27 41 23 32-10 33 0 T M M 17.9 36 20 637 86% 1 41 20 28 37 20 29-14 36 0 T M M 12.7 26 10 532 71% 1 32 20 29 37 20 29-14 36 0 0.00 M M 9.6 22 10 482 64% 31 360 30 58 26 42-1 23 0 0.00 M M 9.9 20 210 691 92% 21 210 31 69 38 54 11 11 0 0.00 M M 12.1 20 210 711 94% 22 210 Sum 1606 870 768 0 3.05 35.2 22 358.1 13096 Avg 51.8 28.1 11.6 Fast Dir 22205 59% Max Dir. 38 280 44 280 NOTE: SNOWFALL AND SUNSHINE DATA MEASURED BY COOP OBSERVERS AT THE FORMER STAPLETON INTERNATIONAL AIRPORT. [Temperature Data] [Precipitation data] Symbols used in column 16 Average Monthly: 40.0 Total for Month: 3.05 Departure from Normal: +0.4 Departure from Normal: +1.77 1 = Fog Highest: 75 on 14 Greatest in 24 hrs: 1.53 on 17 2 = Fog reducing visibility Lowest: 7 on 5 to 1/4 mile or less SNOWFALL, ICE PELLETS, HAIL 3 = Thunder Records: 03/2003 5th wettest March Total for month: 35.2 inches 4 = Ice Pellets 03/2003 now snowiest March - 35.2" Greatest snowfall in 24 hrs:22.9 on 18-19 5 = Hail 13-Tied record high 74 last set 1989 Greatest snow depth: 22 on 19 6 = Glaze or Rime 18-Record 24 hr precip 1.53 old 0.80 7 = Blowing dust or sand reducing 19-Record 24 hr precip 0.74 old 0.31 visibility to 1/2 mile or less [No. days with] [ WEATHER -No. days with] 8 = Smoke or haze 9 = Blowing snow Max 32 or below: 0 0.01 inch or more precip: 7 X = Tornado Max 90 or above: 0 0.10 inch or more precip: 3 Min 32 or below: 24 0.50 inch or more precip: 3 Min 0 or below: 0 1.00 inch or more precip: 1 [Heating Degree Days (Base 65) ] [Cooling Degree Days (Base 65) ] [ Pressure Data ] Total this month: 768 Total this Month: 0 Highest Sea-Level 30.47 on 29 Departure from Normal: -20 Departure from Normal: 0 Lowest Sea-Level 29.23 on 17 Seasonal Total: 5225 Seasonal Total: 0 Departure from Normal: -52 Departure from Normal: 0 26
14 March Monthly Precipitation Denver, Colorado Source: NWS Stapleton Airport 1948-2001 12 Descriptive Statistics Number of Occurrences 10 8 6 March 2003 Monthly Total Precipitation = 3.05" Includes "100 Year Blizzard" No. of Observations = 54 Avg Monthly Precipitation = 1.26 Median Monthly Precipitation = 1.16 Standard Deviation = 0.843 Skew of Distribution = 3.24 Correlation to Normal = 83.66% 4 2 0 0 1 2 3 4 5 6 7 8 9 10 Monthly Precipitation (Inches) 27
16 March Monthly Snowfall Denver, Colorado Source: NWS Stapleton Airport 1948-2001 14 Descriptive Statistics Number of Occurrences 12 10 8 6 No. of Observations = 54 Avg Monthly Snowfall = 12.7 Median Monthly Snowfall = 12.05 Standard Deviation = 7.1 Skew of Distribution = 0.60 Correlation to Normal = 96.43% New Record March 2003 Monthly Total Snowfall 35.2 Inches 4 2 0 0 5 10 15 20 25 30 35 40 Monthly Snowfall (Inches) 28
Weather Delays Denver March 2003: Memorable or Biblical Month? March Monthly Totals Monthly Monthly Precipitation Snow Total Totals Max 4.56 30.5 Min 0.18 2.1 Avg 1.3 12.7 Std Dev 0.8 7.1 March 2003 Actual Totals 3.05 35.2 Recurrence Interval (Years) 59.4 1,358.3 1948-2000 Historical March Monthly Data From Stapleton Airport 29
Weather Delays Limitations to Recurrence Interval Methodology 1. The national weather service does not provide standard deviation data which is a critical element in calculating recurrence probabilities. Standard deviations must be calculated from detailed historical weather data. 2. A weather station with insufficient historical data and/or is located too remote from the construction jobsite may give misleading results. 30
Weather Delay Contract Language: Suggested Addition Existing AIA 201 (1997 ed.) Language 4.3.7.2 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 impact on the construction schedule. Suggestion Additional Language Reasonably anticipated weather conditions are defined as those conditions that have a probable statistical recurrence interval of less than or equal to years, as determined from a minimum of 20 years of daily weather data from the national weather bureau station located at. 31
Weather Delays Internet Weather Data Source Sites Denver-Boulder Weather Data: http://www.crh.noaa.gov/den/cli/climo.html National Climatic Data Center: Worlds Largest Archive of Weather Data http://lwf.ncdc.noaa.gov/oa/ncdc.html High Plains Regional Climate Center: (ND, SD, NE, KS, WY, CO) http://www.hprcc.unl.edu/ Midwest Regional Climate Center: (MN, IL, IA, WI, MO, KY, OH, IN, MI) http://mcc.sws.uiuc.edu/ Northeast Regional Climate Center: (ME, NH, VT, MA, RI, CT, NY, PA, MD, NJ, WV, DE) http://www.nrcc.cornell.edu/ Southeast Regional Climate Center: (AL, FL, GA, NC, SC, VA, PR, and VI) http://www.sercc.com Southern Regional Climate Center: (TN, MS, LA, TX, AR, OK) http://www.srcc.lsu.edu/ Western Regional Climate Center: (MT, WY, CO, NM, ID, UT, NV, AZ, WS, OR, CA, AL, HA) http://www.wrcc.dri.edu/ Am. Association of State Climatologists: http://lwf.ncdc.noaa.gov/oa/climate/stateclimatologists.html Weather Delay Research Website: http://www.guaranteedweather.com/guaranteedweather/industries/construction/index.html Commercial Weather Collection Service: http://www.aws.com/aws_2001/default.asp Weather Channel: Good source of current weather forecasts but does not have historical weather data. http://www.weather.com/ Accuweather: http://wwwa.accuweather.com 32