the two sports should never be done on the same field...
at our airfield we have simultaneous gliding and parachutejumps....however the jumping itself is done 3 miles north of the field, with shuttle bus bringing the jumpers back to the airfield afterwards...
gliders are closely monitored and from the first day it is made clear to all gliders NEVER EVER to head north of the field....monitoring of the gliders is done by somebody appointed as 'gliding supervisor' and he is in constant radiocontact on the gliding frequency....if someone goes too close to the pj-site he/she is warned on the radio....
that's how we do it, and have been accident-free for the last 25 years..........