What to do with dry grasslands

[MonsieurR]

There is a 2 hectare piece of land which remains undeveloped but soon (between 3 and 6 years from now) the owner will start developing it (warehousing).

This piece of land is essentially uneven dry grasslands, and each year the owner clears the organic topsoil as a fire management precaution. Soil beneath is very competent as a construction material.

The owner has been searching for a more definitive solution, and one contractor has proposed to spread this same organic topsoil for subgrading for a future pavement. In this way one saves time on earthworks for the future project. I fail to see the logic since the grass should grow back again the next year. Other option is to use this soil as an embankment, which makes some sense, but the cleared inert earth would start growing grass eventually, wouldn't it?

I still think the best thing would be to remove completely the topsoil just before the actual construction of the warehouse and keep cleaning and clearing the grass for now, but this solutions remains the most expensive (dumps are expensive).

What are your thoughts? is there any way of doing some definitive earthworks so as to save time without incurring in double costs later? Is there a use for organic topsoil on a project?

 

[oldestguy]

It depends on what is meant by "topsoil" as to possible "treatment". Take the case o0f north central Illinois, USA. There the black possibly somewhat organic soil is three feet thick. In Madison,WI on the east side in a low area, also the same. In each area building is done on this "soil" and no problems if you know the bearing capacity by designations also used in "non-organic soil". How bad is it and why is the question? An experienced geotech engineer isn't scared off by the dark color. Just because it amy be black doesn't meran it is no good. Exactly what is the percent organic matter on a weight basis? We usually use loss-on-ignition as the test. A few roots usually means nothing.

 

[BridgeSmith]

Around here, even half-decent topsoil is a valuable commodity to landscapers, farmers and others. Some places, you could likely get someone to clear it for you.

As to grass growing back after stripping the topsoil, it can take from a couple years to a decade or more, depending on the region. The downside is that many places, stripping the vegetation leads to major erosion problems, as there is nothing left to hold the remaining soil in place.

Maybe you can find someone cut it and bale it. Grass hay is very popular in some places.

 

[GeoEnvGuy]

I don't quite understand why the owner is clearing topsoil as a fire precaution. In closed landfills the grass is cut once or twice a year and it serves to protect against erosion. The perimeter firebreak sand/gravel road is scraped clear of vegetation when needed usually 3-5 years.

When the owner wants to develop the property and has lot grading or development plans it will show which areas would require competent fill for structures and those which only require landscaping or parking.

 

[MonsieurR]

Thanks everyone,

Around here topsoil is not really valuable such that they come to get it.
I lied, the owner does not clear all the soil, but removes only at the perimeter, for a firebreak indeed.
Grass takes 1 year to grow back.

I have come to the conclusion that the best is to keep doing that and when the owner actually develops something a more final solution is needed.

 

[GeoEnvGuy]

If the owner is clearing the perimeter every year that is because after scraping off the vegetation the mineral soils are still loose and can grow vegetation, now a four lane highway makes a great firebreak but that is probably not feasible. Options to consider for moderate improvement, compact the perimeter to make it harder for the vegetation to re-establish or cover it with geofabric and rocks. The only other alternative I have seen is in firefighting where they spray the trees with chemicals to make them not catch on fire and it lasts for a couple seasons, so they claim.

The first stage of site investigation is desktop and it informs the engineer of the anticipated subsurface conditions. By precluding the site investigation the design engineer cannot accept any responsibility for providing a safe and economical design.