Hi to anyone and everyone. I've spent months on end researching arena construction. Still really confused. Here's what I have so far. 100 by 200 compacted excavated soil base with a foot of natural large excavated stone from our property crowed with 2" slope and rolled with huge vibrating roller. Now I am stuck and just wondered if anyone can offer any feedback. The stone seems great and tight in most spots but some seem lose in some. Like the fines didn't mix in some spots and its just big rock. I know it's recommended to use a crusher stone but that was not it the budget as it alone would have costs me 20k. I real afraid of screwing this up now as I have 5k plus into already. So my questions are: should I let it sit over winter? I'm in northwest pa and we have cold long winters. Should I bring in the roller again? I also had some free fill hauled in from the asphalt plant next door to fill in the holes dug to get the base rock out. Wondering if I could spread and compact that? I feel like you need a degree in geology to do this right and I'm about to run away from it screaming. Any ideas are appreciated.
What size are the rocks in your arena base? For an arena base you generally need something like 3/4" minus crushed stone. That means, no rocks larger than 3/4". Because, if you have rocks larger than that size they aren't going to pack, instead they are going to chronically rise up to the top and mix in with your footing no matter how well you initially pack them (and rocks rising up into footing is obviously problematic). This is why typical road base or DGA (crushed stone with some larger size rocks) does not work as an arena base (except in special arena installations that involve mats between the base and the footing.
If there are indeed larger sized rocks in your arena base, it may be possible to use a layer of geotextile fabric over the base (and under the footing) to prevent it from rising up into the footing, perhaps there is someone else out there who has used this technique in this type of scenario and could comment on it. I suppose you could also consider putting a layer of clay or 3/4"minus crushed stone over what you already have, but I do think that the larger rocks from the lower part of the base would still come up eventually and cause problems.
To get good packing of your base it is also necessary to have enough "fines" or dust-like particles in your mixture. Freezing and thawing cycles also do wonders for settling and packing of arena bases.
Yes they are big stones. Baseball to football sized. Lots of fines in some spots and not enough in others. I will look into the fabric option that may be doable. Clay isn't even available around here. The contractor does a lot with grading and bases but has never done an arena. I couldn't find anyone who has experience local. Always had turf but after a nasty fall that ended up with my horse on my ankle and a and break riding on what I thought was dry I wanted something else. My original plan was to just grade and roll the excavated native soil but the contractor sortve ran with the rock idea. I really hope it all works out.