I build a raise pond..it would be PERFECT for someone in a wheel chair probably.. its about 2 feet above the ground..
This is what i did
Build a square 2 foot tall holding wall out of field stone (for a natural look $600) then I filled it will fill dirt free from craigslist. we used mortar (cement) to hold it together better.
then i dug out the pond (free cause we did it) and then lined it with carpet remnants (free from a tag sale) and used the pond felt liner that the actual liner came with. Then put the liner in (about $150 i think) and then filled with water.
Not too bad.. the cost of rocks was expensive, but you could literally use anything.. Railroad ties would be AWESOME.. they are super heavy duty and make great holding walls.. you could also use landscape logs, bricks, or even cinder blocks and some cement.
here is a picture.
and heres a link start to finish of the building of the pond"
http://s31.photobucket.com/albums/c391/lindsayanng/pond/