Cal,

Visqueen is clear plastic film. It comes in many different weights and can be purchased at most lumber yards. You would want the heaviest stuff to hold up . 
We normally would make the sides steep to shed any percip more easily.

Hay was/is good. I cut last the second week in Sept. and got 3/4 of the 1st cutting. The alfalfa is going into bloom again now, so as soon as I get a freeze, I'll cut and bale.

As for the 70 orchard.....I blew the dust off it just yesterday! Too many other irons in the fire!

Larry