SEATTLE -- Safeco Field, long known as one of the toughest hitting parks in the Major Leagues, will get a facelift in the coming months as the Mariners announced Tuesday they will be moving in portions of the outfield wall for the 2013 season.

The biggest change involves the left-field power alley, which has been tough on right-handed hitters since the park opened in 1999.

The fence will be moved in from 4 to 17 feet at different points in left field and 4 feet from straight center to the right-center gap. Additionally, the 16-foot-high hand-operated scoreboard down the left-field line will be moved back and no longer be part of the fence, so the outfield wall will be 8-feet high all the way around the park.

Jeff Kingston, the Mariners assistant general manager who was part of a committee that studied the situation, said the changes won't turn Safeco into a hitter's paradise but will even the playing field to a degree.

"We still think it's going to be on the pitching side of the spectrum," Kingston said. "Our approach all along was to make it more fair and be closer to the middle. We still want it to be a pitchers' park and build around pitching and defense, but we wanted to give hitters a chance to where if they really square it up and hit it 390 or 400-plus feet that they'll be rewarded."

Kingston said their studies of the previous several seasons indicated the new configuration would have led to 30-40 more home runs a season, for both clubs. He acknowledged that doubles and triples could actually go down, because of less outfield space, but more well-struck balls should carry over the fence instead of dying at the track.

"Ultimately, that's what gets to hitters," Kingston said. "If they square a ball up and don't get rewarded, they start to change their swing and it wears on them mentally. Having come from San Diego, which is probably the most extreme pitching park, I saw it first-hand for years, especially with young hitters. It really wears on them mentally."

Distances directly down the lines will remain the same, so the changes primarily affect the power alleys in left-center and right-center.

"Our goal is to create an atmosphere here that won't punish pitching, but will create a fair ballpark," general manager Jack Zduriencik said. "We think this park will play fair. There are considerations playing here in the Puget Sound, where the air can be very heavy and very cool in the spring and sometimes all the way into June. We thought by making some alterations it would create an atmosphere that might be an awful lot of fun going forward."

The Mariners rank last in the American League in scoring (3.0 per game), home runs (0.68 per game) and batting average (.218) at home this season through 79 games. On the road, they are sixth in scoring (4.5), tied for sixth in home runs (1.15) and ninth in batting average (.247).

The same trend holds true for opposing hitters who have averaged a league-low 3.3 runs and .229 batting average at Safeco and the second-to-lowest home run production at 0.87 per game this season, compared to 4.8 runs, 1.31 home runs and a .266 batting average against Seattle's pitching in their own parks.

Safeco has been a pitchers' park from its inception. Only twice (in 2005 and '08) in the 13 full seasons since the park opened have the Mariners hit for a higher average at home than on the road and three times (2004, '07 and '11) they've had more home runs at home than in road games.

Zduriencik said he's been told by free agents in the past that the park's dimensions were a negative factor. And there's no question that Mariners hitters have struggled mentally with the tough environment, particularly in the colder months.

"Our hitters have to be here 81 games a year," Zduriencik said. "That was a major consideration. Other ballclubs come in here for three days and, boom, they're gone. It doesn't affect them. But when you're here for 81 days there are factors here that are extreme and we were trying to level the playing field."

Safeco will be the second Major League park in two years to move in its fences. The Mets brought in their Citi Field fences between 10-16 feet in various parts last offseason. Detroit shortened the configuration of Comerica Park in 2003.

The Mariners spent the past several months studying the ballpark and seeking input from former players as well as past and current coaches and front-office personnel. Members of the Washington State Major League Baseball Stadium Public Facilities District Board have reviewed and endorsed the changes and Major League Baseball also has been informed of the modification plans.

Some seating modifications in the left-field area behind the current hand-operated scoreboard will be announced at a later date. Otherwise, the space between the current wall and the new fence will mostly be taken up by the bullpens or a slightly wider "moat" between the stands and the fence as currently exists from center field to the right-field foul pole.

Here are the specific adjustments planned:

• The distance down the left-field foul line remains the same at 331 feet.

• Instead of jutting out quickly to 341 feet, the left-field wall will jut out to 337 feet.

• The hand-operated scoreboard will be moved, and as a result, the height of the outfield wall will be 8 feet from foul pole to foul pole.

• From the left-field corner to the left-field power alley, the wall will be moved in 4 feet.

• The distance at the left-field power alley will decrease from 390 feet to 378 feet.

• From left center to straightaway center, the distance the wall will be moved in will vary from 4 feet to a maximum of 17 feet. At straightaway center field, the distance will decrease from 405 feet to 401 feet.

• From straightaway center to the right-center power alley, the wall will move in 4 feet. The distance at the power alley will decrease from 385 feet to 381 feet.

• From the right-field power alley to the right-field line, the dimensions remain the same.