These two questions came in yesterday and I thought they were both great questions actually
Question 1 is how does TBC Takeoff handle Topsoil Strip and Replace balancing
Question 2 is how do I prioritize which materials get wasted if I have a strata model containing 2 or more strata layers
TBC looks at Topsoil as Stripping and then Replacement. If you create an Original ground surface and then define one or more topsoil stripping areas and apply e.g. a topsoil Strip of 8" of material and define the material as Earthen and then topsoil and set the Properties of Topsoil to Topsoil and Usable for Topsoil Replacement then TBC will compute an Original Ground surface and an Original ground with Topsoil Strip Surface. The strip quantity is the volume of material between these two surfaces. If you set the material property as usable for Topsoil Replacement then all of this topsoil is usable for replacement on the project.
Now take your design surface. You will define the landscaping areas and those areas will have a landscaping material site improvement applied e.g. Hydroseed on 6" Topsoil. The 6" topsoil will be your respread quantity. When you build your design surface and apply the landscape site improvement, the Finish Grade surface will be adjusted to create a surface FG with Topsoil Removed surface. The topsoil replacement quantity will be the difference in volume between these two surfaces. If your Hydroseed material has a thickness (eg you may use sod 1" thick rather than Hydroseed) then that will be eliminated from the topsoil replacement quantity.
So now you have a Topsoil Strip quantity and a Topsoil Replacement quantity and the difference between these two numbers is the balance of Topsoil for the project. If Cut > Fill then you have an excess of Topsoil that you either need to Waste or increase the depth of Topsoil Replacement to eliminate the waste and if Cut < Fill then you have a shortage of Topsoil and need to import Topsoil to cover the deficit or reduce the thickness of replacement to reduce the quantity needed etc.
In this case lets take a simple example where we have three strata materials on the project - we have Soil, Weathered Rock and Rock in the following Cut Quantities
Soil 50,000 CY
Weathered Rock 12,000 CY
Rock 18,000 CY
Total Cut = 80,000 CY
On the site we have a Fill Requirement of 65,000 so if we don’t take Shrink / Swell into account we have an excess of material of 15,000 to eliminate on site.
In this example lets say that out of the three materials I want to waste all 12,000 of the weathered rock and then 3,000 of Rock and then use the remaining 15,000 Rock and 50,000 Soil as my Fill.
Then I would compute the following and apply it in the MSI Manager for the Material Properties of Rock and Weathered Rock after I have done my initial calculation of the Takeoff quantities.
For Weathered Rock - I would set the properties of that in the MSI Manager to Material Nature - Ordinary Soils and then 0% usable for fill in the soil properties.
For Rock we have 18000 of material and we want to waste 3000 of that material which is 3/18 *100% of the available material = 16.66%. I would set the Soil Properties of that to Ordinary Soils and then 83.33% usable for fill so that the 3000 CY is wasted.
I would now re run my Takeoff Report with those adjustments.
Hope that this helps