[Don_Mahaffey]

We'll be moving some dirt at my course soon. My course is built on a lava butte in Central Oregon and we'll either use a large dozer with a ripper or a track hoe with a hammer to break up the rock. Some similar work was done in the past here and we've had to deal with rock that have floated up or areas that have settled, or some of both. My question is, once the shaping is done and it's time to spread the top soil, what's the minimum depth of top soil you can use to cap rock? I know the basic answer would be as thick as possible based on how much soil you can generate, but any rules of thumb out there in terms of top soil thickness?

[Dick Kirkpatrick]

Don:
You have kind of answered your own question: as much cover as possible.
The best scenario for this kind of project is if you can use the broken up rock (even if you have to crush it) for another project on the course.
If I were doing the job, I would have two feet of sub-soil followed by 6-8" of topsoil.
If you are sodding, less topsoil can be used.
The real secret to success with this type of project is to get the rock excavation deep enough to allow the shaping you want to be realized.

[Brian Phillips]

Don,

All I seem to do on all our projects is rock blasting!! There is a lot of rock in Norway.

I agree with Dick.  Go as low as you can with the blasting then cover with as much as you can with a subsoil like clay to soften the humps and hollows.  This will also block up all the holes and that you have between your blasted rock.  I would also think about using a geotextile terram cloth to also help with stopping the clay or soil filtering through the rock.  The last thing you want is sinkage in a brand new fairway.

You can agree different prices with the blasting team depending on the size of rock you get after blasting.  The more bore holes the smaller the final rock.  

One big thing you will have to think about.  For every cubic metre you blast the haulage or size of blasted rock will become 1.5 to 1.7 m3 after blasting.  So 100 m3 will be 150 to 170 m3 to transport or play with afterwards.

We have gone as low as 30cm coverage with clay in some places and then capped with 20 cm topsoil.

Hope this helps.  E-mail me if you want info.

Brian

[PjW]

Don,

Having worked on Bend Golf and Crosswater both with lava rock, what has been stated previously is the only way to go.  Rip, blast or hoe-ram to a sub-grade, crush what rock you have placed over the bedrock and cap with a topsoil material.  I would not put down any less than twelve inches of topsoil as the heat during the day will penetrate the soil and warm up the rock underneath causing dry areas, unless you have a well designed and maintained irrigation system.  If you have a crusher available the rock can be crushed to a 3 inch minus and placed over the rock, graded and topsoil placed.  You can always see about buying cinder as an alternative intermediate layer between the rock and the topsoil.  

Good Luck

Phil Wycoff

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