Raw earthwork acct. for topsoil, pvmt. base, etc. 1

[Brooklyn28]

Wondering others opinions on surefire, accurate methods to quickly calculate project earthworks to account for topsoil stipping, pavement base, etc.

I'm working on site projects where we initially get "raw" earthwork volumes from Eaglepoint using the existing tin based on existing ground, and the proposed tin based on the proposed finish grades. Stripping topsoil and volumes for pavement base are not accounted for in the these tins. Since it is somewhat of a pain to create new tins to account for topsoil depths, pavement base, etc. (especially early on in the project), we are often just adding/subtracting volumes based on pavement area*base depth, disturbed area* topsoil depth, etc. There is always discussion, however, if the volumes should be added to the raw cut or subtracted from raw fill, and if this result is accurate.

 

[Dozerman56]

It's entirely a function of how much of the site is in cut and how much is in fill

 

[DRC1]

Unless te job is entirely cut or fill (and then answer is obvious), there really is no easy way to do it. You have an existing surface. You will need to strip say 6" for topsoil and maybe a foot for pavement. Since the costs for handling the materials is different, you want to keep these volumes seperate. Then you figure your cuts and fills from your striped profiles. As you cut, you want to segegate good material from unuasble material. Those of us who did large earthwork jobs with paper pencil and calculator see anything on the computer nowadays as the easy way.

 

[655321]

I add the volume of topsoil stripping in areas that will receive fill to the excavation quantity. This volume would otherwise not be included between the "existing TIN" and "proposed TIN" calcs, but it is additional material that gets excavated. The volume of the topsoil stripping in cut areas is already in between the TINs.

As far as adjusting for pavement, assuming your final surface represents the top of the pavement, you would add the volume of the pavement in cut areas (this excavation is not represented between the TINs)to your excavation quantity, and deduct the volume in fill areas from the raw fill quantity.

Most of time I also separate the volume of stripping. This way the contract price can include not only stripping the material, but also stockpiling and re-spreading it.

Hope this helps

 

[SteveWarfle]

Brooklyn28:

the other posters are right, it's a matter of whether it's all in Cut or Fill. I wrote an article for the Society of Professional Estimators that is in PDF format on our website. It's here:

http://www.insitesoftware.com/newsletter/Earthwork 101.pdf

It explains some of the effects of things like topsoil respread, pavement sections, etc. on earthwork take-offs, and what happens in cut or fill areas when adjustments are made (or not made!) to the quantities.

As for a method, our software allows you to easily take a CAD file, import in the existing and proposed surfaces, identify topsoil stripping or demolition areas, and then identify the structural (paving, building pads) etc. and non-structural areas (topsoil respread) and soil borings, and it gives you the demolition and stripping volumes, the cut broken down by strata (borings required) and breaks the fill out by structural and non-structural requirement.

Take Care,
Steve

Steve Warfle
Product Manager,
InSite Software Inc

http://WWW.INSITESOFTWARE.COM

 

[LHA]

Steve:

Very informative paper. I downloaded a copy, and ordered your demo CD.

Engineering is the practice of the art of science - Steve

 

[civilman72]

Here's how I have done it for quite a few years and have not seen any major flaws.

Example:
Raw Cut = 10,000 cu. yds.
Raw Fill = 5,000 cu. yds.

These numbers represent the cut and fill numbers you get from finished grade to existing grade (from LDD or Eagle Point).

The overall percent of each is important for future calculations:
Cut = 66%
Fill = 33%

Then, you add or subtract the other materials (i.e. topsoil striping, roadbase, pavement, etc.) from these raw numbers using this percentage.

For instance, lets say we have 3,000 cu. yds of topsoil removal. We all can figure that topsoil removal decreases cut and increases fill. So you would take 66% of 3,000, which is 2,000 and subtract it from the overall cut, and you would take 33% of 3,000, which is 1,000, and add it to the fill.

You can do this for all other materials. For roadbase and pavement, say you have 4,500 cu. yds. You would add 3,000 (4,500 x .66) to the cut and subtract 1,500 (4,500 x .33) from the fill.

So, taking into consideration your topsoil removal and your pavement section, your actual cut/fill (or excavation/embankment) numbers would be as follows:

Excavation = 15,000 - 2,000 + 3,000 = 16,000
Embankment = 10,000 + 1,000 - 1,500 = 9,500
(There are other materials that usually need to be considered, but this is only a brief example).

Although I've used this method with good success, I would appreciate any feedback from others.

Hope this helps...