Can't give a full review right niw, but I'll do what I can.
Long story short, this is basically a feral version of SCP-542 with a controlling parasite on it.
Some specific things I noticed…
SCP-3247 is to be placed in quarantine in a room that's at least 8 meters high, 15 meters wide and 12 meters long,
Why those exact measurements? What's wrong with a Standard Humanoid Containmrnt Cell?
and contains walls that are at least 15 meters thick.
A better use of materials would be to put the cell in it's own wing, 15 meters away from the rest of the facility. Otherwise, that's about a 45 foot-thick wall. Castle walls aren't that thick!
SCP-3247 diet consist of only human muscle and organs.
… why? Meat is meat (generally speaking), and unless it needs those for grafting puposes, pig, cow, or any other domesticated animal used as food should work. And if it only eats peopke, where the hell are we getting its food source? Not like I can go down to the mourge and say "one bucket of assorted human organs and muscle, please.'
Any trespasser that enter the area will be arrested or escorted out.
The Foundation has no authority to arrest people. Unathorized access to a SCP would typically result in disciplinary action (Foundation personnel) or interrogation and possible execution (anyone else). Either way, it wouldn't be required to mention in the Special Containment Procedures.
I'd also like you to (re)read this guide on how to write containment procedures- yours are pretty complex and I'm fairly certain it can be simplified, considering what your SCP is.
Big issue is that you've made a generic monster. Modern SCPs typically aren't just reports on objects, but stories in the form of reports on objects. A plague is boring - the story of a community trying to survive one is interesting. A sprite is boring - the story of some poor shmuck who keeps getting pranked by the sprite is interesting. Cthulhu is boring - the story of him trying to take a vacation at Pismo Beach without causing a mass panic is interesting.
If you're having trouble trying to understand what I'm talking about, read more Series II and III articles, and focus not on what the object is, but what happens over the course of the article.
You have your monster, what story are you trying to tell here?