Steve Peel, check out a relatively new product called RainStore3, or another called DrainCore2 manufactured by Invisible Structures of Aurora, Colorado. Their web site address is:
invisiblestructures.com
I am designing a leach field system by stacking 3 layers of the RainStore3 product which will be covered by a layer of geotextile on the top, 2 sides, and the ends.
The products unique design places the “ring and grid” plastic entirely in compression rather than bending, or tension, resulting in H-25 loading, and high void storage volume of 94%. Both products are made from 100% recycled plastic.
I have no vested interest in this product other than utilizing it in my septic system, and drainage system designs. JWA