SEATTLE -- The fences at Safeco Field are coming in.

The Seattle Mariners announced plans Tuesday to move in the outfield fences at their ballpark for the 2013 season after years of debate on the impact that having one of the more spacious outfields in baseball was having on their offense.

The biggest change will come in the left-center field alley, where the fence will move in as much as 17 feet. The left-center power alley is currently 390 feet, but will be at 378 feet next season. From there, instead of a rounded fence, the wall will move straight out to its deepest point at 405 feet, four feet shorter than currently. The straighter line of the fence will lead to the 17-foot change.

Seattle general manager Jack Zduriencik said many factors were taken into account when determining whether changes to the field would be made, including Seattle's notoriously chilly April and May.

"Our goal was to create an environment that is fair for both hitters and pitchers," Zduriencik said in a statement. "Considering the current field dimensions as well as the climate in and around Safeco Field, we feel this will be accomplished with this new layout."

The left-field corner will also see a significant change with the removal of the hand-operated scoreboard that raised the fence to 16-feet. The fence height will now be a uniform 8-feet from one foul pole to the other and the hand-operated scoreboard will be relocated to a yet-to-be-determined location.

This is the first change to the dimensions of the ballpark since it opened in 1999. Hitters have long complained of the cavernous dimensions of the outfield and the numbers have shown Safeco Field to be one of the more unfriendly hitter parks in baseball. Pitchers love the vast outfield and fly ball pitchers -- like current Mariners starter Jason Vargas -- have thrived pitching in Seattle.

Since 2000, the first full season for Safeco Field, the Mariners have scored the fewest runs and have the lowest batting average at home of any team in the American League. They are fourth-worst in baseball in home runs in their home park, but have the second-best team ERA in the AL at home during that span.