Yet another arena thread... Sorry. Rock shelf? Updated with another question

[BroncoMo]

TL, DR; any issue with situating an outdoor arena on a rock shelf used as the base?

I have finally accepted the fact that an indoor arena is just not in the tea leafs for me; at least not in the near future. The big red hunter I keep at home isn’t getting any younger and I don’t want to keep putting the pounding on his joints from riding on native pasture land.

I live in the western plains and, while my knowledge of soil type is lacking, my many hours of research has concluded that I have sandy loam on top of sandstone and lime stone. The best location on my property for an outdoor is on high ground, with a very slight slope on a short side and long side. One corner will need a little building up, depending on how long I make it.

Weather is mostly arid. Cold and windy winters, snow hangs around for a while and usually evaporates. Heavy rains happen only a couple times a year. I can work on some drainage as necessary but I certainly don’t have PNW type precipitation.

Purpose is for mostly flatting and starting youngsters. I don’t like jumping without eyes on the ground for instant feedback, but I won’t rule out jumping on my own in the future.

5 figures isn’t in the budget for an arena (yes I realize most people come here looking for DIY ideas). I realize that the area will need to be scraped down and laser leveled. I do have quite a need for fill dirt, so I’m excited to scrape off the top soil. I am fairly handy with doing things on my own, have a skid steer, access to other rental equipment, and have some contacts in the construction industry in case I need some advice.

The area I am looking at has a rock shelf under it. I’m not sure if it runs the entire length, but the sloping end, rock is visible. I have tried to set a few fence posts abeam the “arena area” and about 80 feet away; I hit this rock shelf with each post hole I dug. So I am fairly certain that the rock shelf runs the length of the arena area, at some type of depth not too far down.

Has anyone built an arena on a rock shelf used as the base? Considering most places talk about compacting the base to make it rock hard. Well, a rock shelf would already possess this characteristic. I realize that bumps and swales will need to be filled and compacted. Which brings up another question…

I have access to a quarry for road base and fill material. I took a dump trailer load of this “sand” and put it in one of my dry lots for rolling spot. After about 2 weeks, it was packed hard as road base. At which point it dawned on me, that was the material they use to fill washout spots on our dirt roads. It looks like sand, but compacts hard. Does anyone see an issue with using this type of material to build up a sub-base of sorts, albeit minimal, enough to level the area?

[lorilu]

A rock shelf sounds really stable, especially if you put in a good base to level it out (and fill in the missing areas). I have veins of “grey gumbo clay” under my arena that swells when it gets wet. It created havoc when I put in the arena - MANY easy fixes and hard were tried and failed. LOTS of $$ wasted. FINALLY, I bit the bullet and put in a fairly deep crushed concrete base over it… and two years later all is well.
So, I’d recommend a good solid draining base such as crushed concrete (or whatever is commonly used around you) with the footing/riding surface on top.

[BroncoMo]

I figured I should bump up this thread with another question instead of starting yet another thread. Does sandy loam compact if done so with a roller? As in, has anyone scraped off the top soil and compacted the native soil to create a base?

Also…

Considering the original question about using the rock shelf as a base, since I don’t know how far down the shelf is on the “deep end”, it’s possible it may require scraping down 15 inches or so to find it. How problematic would it be to do so without adding that height back in to the arena with rock and such? I know that if you cut in to a hill side that you need drainage between the hill and the arena edge. But what about the arena being slightly below grade? Depending on the angle of the rock shelf and how much build up is needed to add slope, I can still add drains.

It just seems silly to have a solid base down under the top soil a little ways that could be used, but then having to add back in all the height that was taken away via removing soil to expose the base itself.

I was hoping that as I typed this, I would magically answer the questions myself. But no such luck. Thoughts? Again, this would be a private arena with one horse at a time, maybe a couple rides per day, a few days a week. Minimal precipitation as I live in a high plains desert.

[wsmoak]

The Under Foot booklet from USDF is the gold standard. For an arena for casual use at home, (as in, you’re not aiming for high level dressage or reining where you want the footing to be perfect) you can get away with a lot less.

My advice is to find the best clearing and grading guy in your area, even if he does not “do” horse arenas, he will understand how the local soils work and how water moves on and through them.

I had an area cleared and not even laser leveled, just eyeballed by a skilled equipment operator and ended up with this:

171229_4331 by Wendy, on Flickr

It’s got a low corner on the left, it gets some puddles in hard rain, but for me at home, it’s been fine. I made sure that if I ever wanted to go for the ‘real’ arena I wasn’t going to lose anything… and no, this is the beginning in either case. If I wanted to compact and level it, we’d just add the border, bring in more crushed granite and keep going. I never did.

[alfonsina]

Wendy, is yours simply a layer of crushed granite? Nothing underneath? And what’s your basic soil type?

I like it!

[wsmoak]

@alfonsina

Wendy, is yours simply a layer of crushed granite? Nothing underneath? And what’s your basic soil type?

Yep, all he did was scrape off the tiny amount of topsoil and get down to the sandy clay underneath. (Middle west Georgia, it’s a mix of red clay and mostly sand, we’re near a creek.) Then bring in… 10-12 dump trucks of crushed granite (called M-10 here). I lost track. And drive his bulldozer around and around and around.

This is not a properly done arena. It does not have a compacted base, so it’s not perfectly level, and it will get worse over time with the weather. But it’s good enough for now. I drag it with a chain harrow (tines up, not digging in). Without the edges, I lose footing to the low area, but it will settle and compact over there and eventually build up.

Whether this works just depends on your natural soil, which is why I advise talking to a grading contractor who has been working in your area a long time. They will know what you can get away with, and what you can’t.

[lorilu]

Here in Florida many of us have sand. Deep, sugar sand. Doesnt really compact. I knw a few arenas built on sugar sand with a deep compacted crushed concrete base. They are stable and have been for years. The base is the MOST important part of the arena construction. (Believe me. I tried to “spot fix” mine a few times before doing it right. Wasted a LOT of money and effort)

[BroncoMo]

Thank you for this. I’ve seen pictures of your arena in the various threads I’ve seen in my research and I love it. It certainly gives me hope that I can do this without being backed by a trust fund.

How does the crushed granite feel to ride on? I am concerned about having some cush to the footing to save my horses joints as the one has some pretty significant arthritic changes and I don’t want to expedite the inevitable. But at the same time soft tissue injuries scare me. Does your footing seem cushy enough with appropriate/frequent dragging?

This gives me confidence that I can possibly remove the organic material, level it, compact it (I’m not above spending a weekend on a rental roller), and bring in footing; whether it be a compact-able material or sand.

I’m going to need some type of edge timber and wind screens to keep footing from blowing away. So there’s likely substantial cost there. If I can get the natural lay of the land and soil to work for me, all the better.

[wsmoak]

If you are going to compact the base and put in the border, then I would advise doing it right otherwise you will have to do it over.

My ‘reasonably flat space’ is basically the first pass at the preparation for a real arena. That’s the only reason I was comfortable doing this, I don’t lose anything if I decide to keep going forward.

If you sort-of compact, don’t get it level (graded appropriately) put in the edges and bring in footing and it’s not what you want, you have to UN-do the work to fix it. At a minimum you have to scrape up the footing and put it somewhere while you fix the base.

Crushed granite is fine to ride on if you keep it dragged so it doesn’t compact too much. BUT it is very dusty as it keeps breaking down (so you eventually need to add more,) and it is abrasive. If you have barefoot horses it may wear their feet too much.