cool topic, i'm comin in way late here, and i think the key is that you are drilling a water well which will probably have pretty strict regs about what compostion of muds are allowed....it SEEMS that water well muds should be safe, but as you've been advised, check the mud compositions w/ the drillers and/or mud suppliers, pull a nearby well log if you can to help determine what kind of rock you may be drilling into, and while they are drilling yer well, test the mud (put some fatheads in a baby pool w/ the water, rock cuttings, and mud..... see if they survive.....might have to wait on the fish til the turbidity goes down as that could kill fish too).
