Alternate base material scenarios

In our area most plans show a detail of GABC at a given thickness for base for pavement. We have a source of coquina that most engineers will allow as an alternate at 1.5x the depth of the GABC. How is the best way to model both of these scenarios for each project?

Hey Brian,

I am unfamiliar with the GABC acronym, what does it stand for? Could you share a example detail pdf?

As far as calculations are concerned I would like a little additional information about your specific example, otherwise my answer would be assigning a site improvement to the pavement area for the planned material, and an additional improvement for the alternative.

Pages from Brian Takeoff 28394.0000 - Old Cypress Preserve Phase 1 2021-01-14.pdf (27.5 MB)


The GABC is a type of Marine Limestone Base Material. It is shown for use in varying depths on this project depending upon where it is used. We would prefer to use coquina (because we own our own source). Most engineers allow this at 1.5x the noted GABC depth. Doing so increases the amount of base material needed and also increases the amount of cut in the new road. Would it be easier to run one scenario and then save the project as a new file and then run the other scenario or have two site improvements in the same pavement area and create two different sub grade surfaces to run calculations on?

I will create a video for you and post it later today.

Thanks for your help.

You can quite easily change the Site Improvement associated with Layer in the Takeoff Process. So I would create two Site Improvements - GABC with Depth of the design and a second for Coquine at 1.5x the design depth. Then you can associate GABC with the Layer in the Categorize Layers process and run your Takeoff reports after building surfaces, then you can change the material associated with the layer to Coquine and rebuild the surfaces and re run the takeoff reports. That will then give you comparative numbers for the two alternative bids etc.

Does this make sense?



All of those explanations make sense. Thanks for taking the time to show multiple ways of skinning the cat.