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Bad weather calendar

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kaythrine Bigueras
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Hi eveyone its me again!

Im still working on our Master Schedule and this time they required me to put up a Bar Weather Calendar, the specs include MONTHLY ANTICIPATED ADVERSE WEATHER DELAY WORK DAYS, the thing is how will I apply it on the schedule?

I already have calendar set for the project in 5 day work week and i was told to tie in the bad weather calenday, how will I do it? do i need to edit my existing calendar and set up possible non-working days base on weather forecast available on the internet or is there a command in primavera where i can tie in two calendars for each activity?

I really need your advice on this guys.. thanks in advance!

Replies

Zoltan Palffy
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Yes ultimately at least 50% of the work hours on critical activities must have been impacted to claim as a weatehr day. Let's not forget about the additional days where there was NO rain but critical work could not take place because ground was still too wet to work it or the haul route was impassable or the location to dump the excavation was shut down due to the ground still being too wet.

Rafael Davila
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My experience has been that such specifications are usually incomplete as they fail to state what constitute an above normal rain day.

At home we are in a drought year ant the NOAA precipitation for 2015 is as follows.

DAYS >= .01        12              
DAYS >= .10         4               
DAYS >= .50         2             
DAYS >= 1.00        1             

Which is the criteria for a rain day?

The easy part is to figure out the average for DAYS > X during the last 20 years for each but figuring out the threshold [X] to use is arbitrary unless clearly specified.

The impact of a given threshold for different topographies is different and shall be selected accordingly.  A one inch rain event at home means most rain will go directly to sea and little to land but in Texas and California a one inch rain event can be significant, not to mention the issue on intensity [rainfall/unit time] also matter.

Seems like some specifiers are lazy and cannot determine the threshold and the average number of rain days above the threshold to be considered.  I suspect it might not only be laziness but lack of understanding, it is not the same .01 than 1.00.

At home experience shows the most common impact occurs at 0.25 a number not in the table. We average from 3 to 6 such rain days during the different months of the year.  Our specifiers, except on federal jobs, are not that lazy and figure it out for everyone what average number of rain days to consider on the schedule as a contractor's risk, anithing above will be a shared risk, EOT for the contractor but no extended cost. This type of specification we find it fair for most construction jobs. In rare occasions 100% risk allocation on the Contractor or 100% on the Client can be the way to go.

Ironically it is not rain amount what is used for the day be considered impacted by rain, the rule is usually that at least during 50% of the work hours critical activities were impacted.

Zoltan Palffy
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The MONTHLY ANTICIPATED ADVERSE WEATHER should be based on the NOAA National Oceanic and Amdinistration data or similar data for the projetc locaiton and will be the baseline of rmonthly weather time impact evaluations. So if your project was geographically located in Seattle as opposed to New York obiously the adverse number of weather days is greater on Seattle than New York so your Monthly Anticipated Adverse Weather would be based on the data form Seattle NOT New York

We are talikg about the mena or average here which is the  

Mean Number of Days with Minimum Temperature 32 Degrees F or less.

1. The mean number of days with a minimum temperature of 32 degrees F or lower indicates the frequency of occurrence of days with freezing temperatures.

2.  Mean number of Days with Maximum Temperature 90 Degrees F or More (70 Degrees F or More for Alaska Stations)

3. Mean number of Days with Precipitation 0.01 Inches is the  mean number of days per month with at least 0.01 inch of liquid or water equivelent of frozen precipitation. This is the smallest amount of precipitation numerically recorded. 

F. Snowfall (including ICE PELLETS and SLEET) - Average Total in Inches.

here is a link to NOAA this will give you the Mean Number of Days with Precipitation 0.01 inch or More

http://www1.ncdc.noaa.gov/pub/data/ccd-data/prge0112.txt

you can get additional data here if you are working in extremetly hot or cold geographical areas.

http://www1.ncdc.noaa.gov/pub/data/ccd-data/

basically create 2 calendars 

 

one for weather sensitive work that includes the above normal number of adverse weather days per month. The days that you choose to be non working days for any particular month will be totally ramdom. Assign weather sensitive work to this calendar.

The second calendar will not have weather seneitive days included in it and the non weather sensitiive  activiites should be assigned to the 2nd calendar.

V Kutty
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Hi Guys,

I have a situation where during installation we are affected by Wave and wind.

So % of days off due to high Wave maybe say 10% of the month and high wind 20% is it a cas of doing (31-31x.1.x.2) to get the number of Wokring days in the month?

Thanks,

Mike Testro
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Hi Kaythrine

It is more realistic to scatter your bad weather non work days in a random pattern over the months.

Once you have done your research as to the anticipated weather stoppages then take the monthly average number of days and stick them in the monthly calendar.

It has to be raining for more than half a day for a complete washout.

Don't forget that it rains on weekends too.

Best regards

Mike Testro

kaythrine Bigueras
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Hi Everone! Thank you for your inputs, we currently use 2 calendar 1 of it is the Bad weather calendar, we just placed the non working days on the every last week of the months, using the first calaneday for all works which will not affected by the weather and the other one for those works outside which will greatly be affected at any athmospheric disturbances. But I think this approach is somehow difficult since it gives ecxessive number of non working days. I am really hesitant to use it, it doesnt seem realistic at all. But the client requires it.

 

Thanks to all.

Rafael Davila
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There are several possible approaches for accounting for weather:

1- Set allowance assuming some periodic distribution (a predicted weather calendar).

This can be done setting specific days as non-working. But what happens if it does not rains even if expected rain is one day per week, are you going to plan with all Fridays as a holiday? What if on paper this delays the Early Start of a successor, it does not rains but because of this you planned for some delivery is going to be late and know you have to delay the activity because the rain assumption was poor planning? It did not rain, you should have known!

Instead of using specific days, this approach can be modified by setting your workweek available work hours to a fraction to mimic the expected reduction. With this method you will have to create exceptions for every month the reduction changes, otherwise a single reduction will be applied across the board for the whole year. Beware that the creation of exceptions can be tricky and even limited on a few software packages.

If using weather calendars, then in order to see unobstructed view of true Early Schedule you will need to replace the calendar(s) by keeping another version without the weather calendar(s). You shall keep a “most probable” version for a long-range prediction and an “optimistic” version for management of your job.

2- Include allowance as part of the activity duration. Seems not bad, but what if activity is delayed beyond rainy season? Yes here it is rainy season year-round, but we had in the 80’s two consecutive drought years!

3- Set weather allowance at the end of the job and as progress happens deduct available allowance. This option allows you to calculate true earliest dates, those that might occur if no rain happens. If you are not willing to keep two versions, use this method.

You need a view for the long range prediction and you need an unobstructed view with optimistic durations and no weather delays to manage your job, the unobstructed schedule shall provide necessary buffer to effectively manage your job. For the first version I prefer to use the simplest method, I use specific non-workdays, in addition is easier to explain to others, anyway it is for the purpose of long-range prediction. The second version is easy; just keep away all the noise.

Within Spider Project I can update either version and then at a single click of the mouse transfer updating data to the other, no esoteric procedure needed. Keep it simple, have both views and do not contaminate one with the other.

Best Regards,

Rafael

Mike Testro
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Hi Kay

Bill has the right approach with non-work day exceptions added to a separate set of calendars.

One thing that you have to consider is that your resource allocations track the correct calendar otherwise your rescheduling will be all over the place.

In Powerproject there is a button in resource modelling that allows "Calendar as Task" which removes the problem.

Otherwise you have to set your resource calendars individually and if you have a resource for say Brick & Block Gang you will have to create two gangs - 1 for external rain work and 2 for internal block work so that each can recieve the correct calendar.

You may need to allow for a cold weather calendar for frost sensitive work and a high wind calendar for the cranes.

I once used a hot weather calendar for a large glass atrium which could not be assembled when the temperature exceeded 25deg

Set your exceptions as Non-Working rather than Holidays and if your software allows you can have a different shading for each type of exception.

Best regards

Mike Testro

Bill D.
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Hi Kayth M.

What I will do to with that exercise is to create a new calendar incorporating all the possible weather related delays and named it Rain Calendar. The data maybe  based on experience/fair judgement, forcasted weather report or any viable information you can gather. Then I will assign this Named Calendar to the activities that are likely to be affected by this uncertainties. Now, during the schedule implementation and updation of the programme, you will keep track of this Named calendar, change the timing of assumed rain day to what has acutally happened. This will reflect the real life situation.

I believe this is one approach I would use to play with that situation. Other experts here on the planet may have a different way of sorting this out. Well just have to wait and see it coming.

 

Cheers,

 

Bill D.

Daniel Limson
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Hi Kay,

First of all you can not predict bad weather, so yo can only incorporate past events in your calendar.

Keep a log of bad weather conditions which affected your work and incorporate it to your existing 5 days work week calendar.

Best regards,

Daniel