My outdoor sand ring was professionally built 11 years ago, using the USDF booklet for guidance.
Now, quite a few little rocks are showing up. I can only assume that I am dragging it too deep and bringing up rocks. My coach said that it is normal for some gravel to work its way to the surface over time. Is this right? She thinks the sand is still deep enough. The ring is used lightly since I am the sole rider.
How can I get rid of these little rocks and how can I prevent the problem from happening again?
First it was excavated to make it level. It was built with big rocks on the bottom, followed by smaller gravel. which I believe contained some stone dust. I do not remember the exact size of the rocks/gravel, but I do know that we followed the USDF Guide to Dressage Arena construction. The whole thing was compacted. There was no membrane used. Then sand was put on top.
We are in SW Ohio which does get freezing/thawing winters. It has been a very workable arena for me and the base seems to be good and solid.
The rocks that are coming up are small (most are 1" or less). Perhaps this is to be expected??? I just don't know.
I built my sand ring to similar specs about 13 years ago and some of the small flat "road base" gravel has floated to the surface. However, since the small rocks are only 1 inch or so, are flattened (road base is made to compact together and tends to have flatter rocks) and has not been a problem in the footing, I just ride with it. All 4 horses are barefoot, no-one has gotten a stone bruise or abscess in decades. I do drag the ring to keep it level and this will tend to turn up any larger stones. I hand walk around the arena after riding and usually find one or two bigger stones- 2 inches or so- that I toss to the side. I don't think you need to worry.
Remove vegetation and topsoil from arena and surrounding area. (Allow at least an 8’ apron around the entire area for swales). Grade base to 2% crown, or 2% cross-slope across the short side. The shoulder and the lay of the land will determine the best grading decision.
Incorporate swales and ditches around the arena to keep migrating surface water away from the arena.
Compact to better than 95% modified Proctor. Depending on the size of the arena, at least three (3) density tests should be made.
Install arena fence (posts only). To ensure proper finish height, allow an extra 6 inches for base and sand.
Roll out geotextile material 12 to 18 inches, overlapping at all seams. Extend the material 18 inches outside fence line. Slit geotex material with scissors or razor knife to fit around posts.
Completely cover geo tex and spread 6 inches of [U]3/8" minus Uniformly Dense[/U]-Graded Aggregate Base with a Sand Equivalency between 30 and 50.
On-site water should be added, if necessary, prior to compacting crushed stone base to 95% modified Proctor using 15-ton vibratory roller. Depending on size of the arena, at least three (3) density tests should be made. Be sure to compact between fence posts and apron outside fence line. Allow crushed stone screenings base to "cure" for 3 to 4 days.
If desired, install 2" x 6" pressure-treated baseboard. Set boards 2" above top of aggregate base to allow water to pass under and still contain the cushion.
Finish building the fence. (Leave enough rails out of one section to allow the sand truck access to dump.)
Spread the manufactured, medium/coarse angular, washed sand (Not greater than 10% passing #100 screen) over the entire arena. Your call as to how many inches (2 or 3)
The largest stone, if it ever came through the surface would be 3/8" or less. You would hardly know or feel it. The larger the base gravel is, the greater the risk of noticable stones appearing. This happens due to dragging and frost/thawing. It is my feeling that you will from time to time see the gravel you installed in your ring. There are rock rakes etc but I am not sure if they would help...