Boom

[gridlore]

A hand grenade was found Monday on 19th Avenue near a Shell station at Santiago.

That;s about two blocks from where we used to live, but that's not why I'm posting this. This is (from the story):

Police diverted traffic from several directions and evacuated people from the immediate area before detonating the grenade about 2 p.m., Tully said.

A hand grenade has a lethal radius of about 4 meters. Beyond that, the shrapnel density drops off quickly. (figure the surface area of sphere.. the intact notched-wire fragmentation portion of the device is about 5cm across before it explodes.) Add in the fact that the shrapnel is not very aerodynamic, and you can be a few dozen feet from a grenade and escape harm. The biggest danger is concussion, and that isn't that bad. (about 5kg of C-4) There isn't a hand grenade on Earth that will lift a man off his feet, even if he's standing on it.

Which makes the evacuation bit a little funny. Were they going door to door making people leave homes? How far down did the traffic diversion begin? I think maybe they over-reacted just a little too much.

Comments

[isomeme.livejournal.com]

There are times when overreacting is prudent. First, herding people at least several hundred feet away from the danger space reduces the chance of (e.g.) a fast bicyclist or unnoticed child zipping right in at the last second and catching a fragment. Second, people get panicky when things go boom in a residential neighborhood, so it's good policy to do it without a lot of spectators.

What it really comes down to is CYA, though. You and I both know the weird tricks ballistics can play. If a wire fragment ends up flying 100 feet and putting out somebody's eye -- certainly not beyond the bounds of possibility -- do you want to be the SFPD field commander who decided to let the crowd stay that close to the grenade?