Seattle Mariners at T-Mobile Park

T-Mobile Park Facts & Ground Rules

The Name

In January 2019, the home of the Seattle Mariners became known as T-Mobile Park, thanks to a 25-year naming rights agreement with Bellevue-based T-Mobile. The partnership is helping lay the foundation for the next chapter in Seattle Mariners baseball and the ballpark experience as the Mariners invest $600 million in maintenance, operations and upgrades over the next 25 years. T-Mobile is a locally-based, international brand with a strong commitment to community and excellent customer service. The Mariners are proud to partner with T-Mobile and look forward to working together over the years to achieve our shared goals.

The Roof

The ballpark's one-of-a-kind retractable roof is designed to cover but not enclose the ballpark, thus preserving an open-air environment. The structure covers nearly 9 acres, weighs 22 million pounds, and contains enough steel to build a skyscraper 55 stories tall. The three movable panels glide on 128 steel wheels powered by 96 ten horsepower electric motors. A push of a button closes or opens the roof in an average of 10-20 minutes (depending on wind and other weather conditions). The roof is self-grounded (in the event of lightning strikes) and is designed to withstand 6-7 ft. of snow and sustained winds of up to 70 mph.

Ball Hitting Roof Trusses

Batted ball strikes roof truss over fair territory: In Play.

  • If caught by fielder, batter is out and runners advance at own risk.

Batted ball strikes roof truss over foul territory: Dead Ball.

Movement of Roof

Please refer to Commissioner's Bulletin regarding opening and closing of retractable roofs.

Scoreboard System

T-Mobile Park features one of the most comprehensive scoreboard systems in Major League Baseball, including 11 electronic displays and an old-fashioned hand-operated scoreboard in left field. A new high definition video display system was installed for the 2013 season, replacing the main scoreboard in centerfield. Measuring 56.7 'x 201.5' (11,425 square feet), the new HD LED screen is the largest in Major League Baseball and one of the largest in professional sports. The out-of-town scoreboard in left field displays current inning scores of games in progress from around the Major Leagues. Two, first-of-their-kind play-by-play boards along the first and third base lines display running summaries of plays to help fans follow the action. Four auxiliary boards display player at-bat information, pitch speed and additional game-in-progress information.

Playing Field

T-Mobile Park's playing surface is a custom designed state-of-the-art field. It features a specially designed drainage system and a custom blend of four kinds of Kentucky bluegrass and two kinds of perennial rye grass to provide the optimal playing surface for the athletes, the retractable roof, and the Northwest climate. The drainage system includes layers of drainage pipe, pea gravel, sand, and grass. A spider web of one-inch plastic hose circulates hot water under the grass to bring it out of dormancy in time for Opening Day, and also compensate for shade and low levels of direct sunlight.

Outfield Area
Netting in right field corner in foul territory is above and beyond the wall. A batted ball that bounds into the netting is a dead ball whether or not it rebounds onto the playing field: Two Bases.

A ball must enter the dugout to be considered a dead ball.

Photographers' Areas
The ball is "in play" if it hits any of the railings defining the photographer wells and bounces back onto the playing field.

Universal Ground Rules

The Commissioner's Office has issued the following Universal Ground Rules for use in all Major League ballparks this season. Ground Rules pertaining to individual parks are posted separately in those parks.

  • Ball on the top step (lip) of the dugout is in play.
  • No equipment is permitted to be left on the top step (lip) of the dugout. If a ball hits equipment left on the top step it is dead.
  • A player is not permitted to step or go into a dugout to make a catch.
  • A player is permitted to reach into a dugout to make a catch. If a player makes a catch outside the dugout and the player's momentum carries him into the dugout, then the catch is allowed and the ballis dead. See Rule5.09(a)(1) Comment.
  • A batted ball in flight can be caught between or under railings and around screens.
  • A catch may be made on the field tarp.
  • Batted or thrown ball lodging in the rotating signage behind home plate or along first base or third base stands is out of play.
  • Batted or thrown ball resting on the rotating signage behind home plate or along first base or third base stands is in play.
  • The facings of railings surrounding the dugout and photographers areas are in play.
  • Any cameras or microphones permanently attached on railings or along outfield walls are treated as part of the railings or outfield walls and are in play.
  • Any recessed railings or poles that are in the dugout and photographers areas are out of play and should be marked with red to mark them out of play.
  • Robotic cameras or audio equipment attached to the facing of the backstop screen are considered part of the screen.
  • A batted ball striking the backstop camera or audio equipment is considered a dead ball.
  • A thrown ball striking the backstop camera or audio equipment is considered in play.
  • A ball striking the guy wires that support the backstop is a dead ball.
  • A ball lodging behind or under canvas on field tarp is out of play.
  • A ball striking the field tarp and rebounding onto the playing field is in play.
  • No chairs can be brought out of the dugout or bullpen and onto the playing field.
  • All yellow lines are in play.