The Mariners will move portions of the outfield wall at Safeco Field for the 2013 season. The changes, which will primarily affect the left field power alley, are the first to the field dimensions since the ballpark opened in 1999.
You probably already saw this but I will post it for others interested in the outfield walls at Safeco.
Outfield wall changes at Safeco.
LF Line 331 to 331
Left Center 390 to 378 Biggest change is the Lf power ally.
Deepest Point 409' to 405
Straightaway Center 405' to 401'
Right Center 385' to 381
RF Line 326' to 326'