The Seattle Mariners have announced that they'll move in the fences at Safeco Field, and the biggest change will be the left field power alley all the way to center field being brought in as much as 17 feet, according to The Seattle Times baseball reporter Larry Stone.
The decision has already been approved by MLB:
To those asking: This is a done deal. Changes have been endorsed by Public Facilities District Board and approved by MLB.— Larry Stone (@StoneLarry) October 2, 2012
Josh Liebeskind of MLB.com says the dimensions down the lines will be unchanged.
The hand-operated scoreboard will be moved and no longer in play, making the wall only eight feet instead of 16. That means the wall will be uniform in height, both Liebeskind and Stone report.
Finally, the fence from straightaway center field to right center will move four feet inward. So too will the left field corner to the midway spot between the bullpen walls, according to Stone.