How the Mariners groundskeepers get T-Mobile Park ready for every game

On the schedule posted in Mariners groundskeeper Tim Wilson’s office, two phrases in red lettering jump out. The 8-by-11 page details a four-week shift schedule for members of Wilson’s day crew, most of which is highlighted in green to indicate Mariners home games — that is, except the red text.

The first part says “Crane on field.” That thought makes Wilson stressed. He loves the field, loves his job and loves the attention to detail that goes into maintaining a pristine playing surface like T-Mobile Park. He jokes with one of his assistants that he might go golfing that day instead because he doesn’t want to watch the events staff roll a crane onto his field.

The second phrase — “concert”— explains why the crane was there. T-Mobile Park hosted the Red Hot Chili Peppers on Aug. 3, meaning the crane was rolled in three days before set up the stage in the outfield and lay down flooring. Ten thousand people standing on the floor can damage the grass underneath, and covering the grass with portable flooring limits sun exposure and traps moisture, leading to potential disease. Spilled drinks that seep through the flooring gaps don’t help, either. 

“It seems like it’s picking up more and more every year,” said Kevin Dvorak, one of Wilson’s assistants, of the other on-field events. “As far as everything on the field, baseball is the easiest, most routine for us. And the most fun — that’s what we’re here to do.”

The job used to be baseball-centric when Wilson started on the Mariners groundskeeping staff in 1999, working under former head groundskeeper Bob Christofferson. But over the years, the ballpark turned into a multipurpose facility that hosts more and more weddings, graduations, concerts and Enchant Christmas activities, among other events.

Wilson and his staff’s behind-the-scenes roles are filled with intricacies and details, both to prepare for concerts and each of the Mariners’ 81 regular-season home games. Maintaining an MLB ballpark comes with a spotlight, Wilson said, and the workload isn’t light. They’ve already begun planning to host the 2023 All-Star Game, a “showcase” for the field. Yet despite busy schedules, the passion that Wilson and his crew share for groundskeeping, which they consider an “art,” is apparent throughout the season.

“Best field in the league, and I didn’t always say that, but what Tim and his crew have done is phenomenal,” Mariners manager Scott Servais said. “Really — the grass, the dirt — our players love it.”

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The morning after a concert is probably the most nerve-racking, Dvorak said. The crew gets the flooring system removed and the field cleared as fast as possible so they can assess the damage before the Mariners return home, oftentimes on a quick turnaround. By now, they’ve done it so many times they know what to expect. “We’re always happy when it’s not as bad as it could be,” Dvorak said. 

At times, they had to re-sod big chunks of center field where the stage is typically set up. If there were ever too much damage, they’d call their distributor in Moose Lake and buy the same type of turf: Kentucky bluegrass overseeded in perennial ryegrass. 

But for the most part, the crew turns to their “sod farm” nursery behind the center field wall, where they grow an extra patch of grass for re-sodding purposes. That grass is on the same fertilizer and fungicide treatment schedule and watering schedule as the field itself — that way if a small piece needs to be replaced, the consistency and coloration match.

The sod farm is useful for regular gamedays, too. If center fielder Julio Rodriguez digs his cleats into the same spot of grass repeatedly, it might lead to a “worn spot” that the crew re-sods to keep the field as lush and healthy-looking as possible. 

Those are the kinds of minor imperfections which only the crew notices. If there’s a small gap in between the mow lines, they call it a “mohawk.” If there’s a small curve in the straight lines of a mow-pattern, they call it a “banana.” Both are easy fixes, but they’re still a good laugh for everyone involved. 

“It doesn’t affect the playability of the game,” Wilson said of bananas. “But I’m still going to make fun of somebody for it, and they’ll make fun of me if I do the same thing.”

The crew values aesthetics, but playability and safety are far more important. For instance, Dvorak is talented and creative enough to mow the Mariners logo directly into the center field grass, but he wouldn’t do that because the ball would change directions when it bounced.

Playability ties into everything the crew does on a daily basis. And for the grass in the outfield and infield, that’s directly correlated to the plant’s health. 

The crew uses a Toro Reelmaster 3100-D in the outfield and hand-driven mowers in the infield to typically change the grass pattern every homestand. The mowers have steel drums that push the grass in one direction, forming the pattern that’s visible from the stands. But continuously pressing the grass in the same direction isn’t as healthy, so every couple of days, they allow the grass to stand up and breathe. 

To do that, the crew performs a “neutral mow” which erases the pattern and gives the grass a break when the team goes out of town. Then a few days before the Mariners return, they’ll discuss the newest pattern and implement it. 

“I do have allergies,” day crew member Carl Gaube said after completing a neutral mow, as he dumped out a bin of grass clippings. “But Zyrtec works wonders.”

Gaube and the crew cut the grass to ⅞-inch and maintain that. But in the summer especially, when the grass has plenty of sunlight, they also use spring tines to implement “verticutting,” which keeps the grass from getting too dense by removing thatch and organic build up, said Ryan Nagy, Wilson’s other assistant. Otherwise, the ball might “snake” by rolling side-to-side in a more unpredictable fashion, or might not roll fast enough, entirely. 

Wilson loves the summer heat because extra sunlight is better than none. Seattle’s climate is ideal for grass-growing, Dvorak said, but it becomes challenging during early spring and late fall. Right field and the first base sideline don’t get any sunlight for two months, so they have to wheel in “grow lights” for artificial sun, Nagy said. The field only gets watered once a week — otherwise too much moisture gets trapped, leading to disease.

In that summer heat, Dvorak arrives at 6 a.m. to water the field on one 85-degree day in late July, among other tasks. Of course, the grass needs more water when it’s hot, but so does the dirt.

The crew typically runs the irrigation system for the outfield grass but hand-waters the infield dirt to avoid inconsistencies. On a hot day, that means watering every few hours so the dirt has even moisture throughout. Dvorak demonstrates by digging a key, which simulates the stud of a baseball cleat, into the dirt and then pulling it out. If the level is right, there won’t be any disruption in the surface (not too hard so the key won’t go in, and not too soft where it leaves a divot). 

They use moisture meters to get more accurate readings as well, Nagy explains. He spreads Turface as a topping layer, meant to absorb moisture like a sponge, and an additional layer of shale product, meant to hold the moisture inside after it’s been absorbed. Wilson himself will go out to put the “finishing touches” of water minutes before the first pitch. 

“It’s a grind during the season,” Wilson said.

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It’s all an art. Before the season, they had laser-grading infield work done, which established a perfectly level surface. A.J. Montoya, a day crew member, works on the mound every day. He meticulously redoes the foul lines with a string and wheelbarrow of paint, which Wilson prefers over chalk.

Jay Herrick crafts the mound every day. He adds BlackStick Mound Clay, and his Twitter handle “@Sir_Tamps_a_lot” references the process of “tamping” where he packs and levels the mixture of engineered soil, sand and clay. 

“I’m an artist, so I like to get it all tuned up,” Herrick, a day crew member, said. “Aesthetically pleasing is what I go for.” (He is also, quite literally, an artist. Wilson said that he does a lot of painting on the side, too.)

Technology has made the groundskeeper job a bit easier. From his phone, Wilson can control the irrigation system, check moisture levels from six buried in-field sensors and access security cameras that show him the field. He’ll check a few times per day. 

Even though it helps improve work-life balance since the crew doesn’t always need to be in-person to monitor field conditions, the field is still frequently in the back of Wilson’s mind. That morning in late July, Dvorak texted Wilson about that day’s game plan at 4:45 a.m., and Wilson replied within 30 minutes. 

“There’s a lot that I take on, but there’s a lot that I love about coming to work each and every day,” Wilson said. “Sometimes you just can’t turn your brain off when you love what you do.”

Wilson and the day crew watch batting practice and infield grounder practice every day. They make sure there’s a smooth transition from infield grass to infield dirt to outfield grass: no sudden bounces. They also check the edges (where grass and dirt meet) to make sure the ball doesn’t unexpectedly change trajectory. It’s an area they’re continuously working to improve, Dvorak said.

Edges are one of Wilson’s pet peeves. The crew makes fun of him for it, but he wants them to be “perfect” so they edge twice per homestand. That’s because the sharpness helps the field look more pristine, something that isn’t the case with Wilson or Dvorak’s yards at home.

Back at T-Mobile Park, days after the Red Hot Chili Peppers, fans can still make out indentations where the stage was set up. Aesthetics are part of the job, but there’s only so much they can do. Besides, Wilson always goes back to playability. 

He builds relationships with the players by talking trash or just hanging out so they feel comfortable coming to him if there is anything they want changed.

“The feedback’s been great,” Wilson said. “The biggest thing for me is to keep consistent, so each day they go out, they know they’re getting a consistent playing field that’s going to play well for them. In the end, we’re all here for them, and I want them to know that.”