Several fairways were flooded on Monday by torrential downpours that followed a dumping of more than three inches of rain on Friday. More rain is forecast for Tuesday, Wednesday and the scheduled opening round on Thursday.
US Golf Association chief Mike Davis told a news conference at the Ardmore, Pennsylvania, club that the biggest concern was the green and greenside bunker at the 11th hole, which is the lowest point on the course.
More than a dozen groundskeepers worked to repair the flooded bunker at the hole, which catches the overflow from a creek that runs along the right side of the green.
"It's where two creeks come together. But we've had two Major rain events and both of which the green has managed to stay above water, which is a good thing," said Matt Shaffer, the course superintendent.
"Certainly it's saturated. But the good thing down on 11 is that the water comes up fast, but it also recedes very quickly And it's silt, so it will dry really, really quickly. We just need a little bit of sunshine."
The 11th hole was closed off to any intrepid players looking for a soggy practice on Monday as the bunker was repaired.
"We left the base sand in and then we just took the silt off and then we put approximately three tons of new sand in and we plate tamped it. And we were ready to go," Shaffer added.
Contingency plans include using alternative holes on the club's West course, but Davis called it a 10,000 to one chance.
"I think in terms of a doomsday scenario, who knows, if it's 10 thousand to one that we would have that happen," Davis said.
"But we don't anticipate that happening to the point where we're not going to be able to get the US Open in or we're going to have to go to some holes on the West Course."
Davis said that despite being built on heavy soil, Merion was perhaps the best draining golf course he had seen.
"If you walk this course you know there's hardly any flat lies at Merion," he said. "Its surface drains beautifully."
The USGA executive director said that the chance of standing water forming on greens might be taken into account.
"Thursday isn't looking all that promising," he acknowledged. "So there would be an example on Thursday where we would say let's look at all 18-hole locations, make sure to the extent possible we've got those in higher locations so we don't get puddling right around the hole."
Davis said areas of casual water on fairways could be dealt with as long as a player can take relief and not go somewhere too far away.
"Just because they're wet or there is standing water that wouldn't preclude us from playing golf," Davis said.