I was watching the launch live, my heart sank....
The rule of thumb is; The larger the missile the larger the buffer zone.
For public viewing at Wallops the closest one can get is 7.5miles. I haven't found anything definitive yet, but I believe the Launch Control bunker was no closer than 1mile. IMHO, an educated guess to the diameter of the blast zone would be 1/2mile (0.8km) with debris falling as far away as 5miles (8.05km).
They certainly felt it at Launch Control, and to a lesser degree the Visitors Center 7.5miles (12.07km) away, the upper part of the line by the 175route marker is the approximate location of the Visitor's Center.
All personnel within the immediate launch area are accounted for and protected by specially hardened bunkers before liftoff.
For Cape Canaveral in Florida the closest the public can get is 10miles (16.09km), with Launch Control 5miles (8.05km), and I believe the VIP viewing area is 8miles (12.87 km) away.
The Antares launch was delayed Monday
because a sailboat had wandered into one of two of the restricted zones downrange shown in the third pix.