ASA Girls Slow Pitch -1st baseman Obstruction

Question
Recently in a teenage girl's game, A batter hit a nice shot to right feild, which the outfielder had to chase down.  After the runner passed 1st base, the 1st baseman began moving towards the outfield and ran in her path, which knocked her off balance as she passed, she continued on pass second and was told by 3rd bse coach to go back to 2nd cause by then the throw was back to the pitcher.  She clearly would of made it to 3rd and possibly home.  Umpire made note of the situation and told her to go to 3rd.  The defending coach came out and argued that it happened at 1st and no extra base should be given.  He then reversed his call.  I argued that if this is actually correct, I would make the 1st baseman block everytime an outfield hit occurred.HAHA. What should be the proper call?

Answer
Thanks for the question!

The rule you speak of is called "Obstruction".  Interference is on the offense, obstruction is on the defense.

Obstruction - Obstruction is the act of a defensive team member: A. Who hinders or impedes a batter from striking at or hitting a pitched ball. B. A fielder, who impedes the progress of a runner or batter-runner who is legally running the bases unless the fielder is:
1. in possession of the ball.
2. in the act of fielding a batted ball.
Note: Contact is not necessary to impede the progress of the runner.

The umpire mechanic for this is to signal a delayed dead ball signal. Time is called and the umpires awards the runner the base(s) or run to which they are entitled.

An umpire should award base(s), in his/her judgment, that the runner would have achieved had the obstruction not occurred.  There's no formula to this, it is simply the judgment of the umpire as to whether or not the runner would have made it to a particular base or not.

I hope this answers your question, if not please reply!