English: Ever wondered about how groundwater observation wells are drilled? This photo provides a behind-the-scenes look as USGS drilled a groundwater well in California last month. This photo looks down over a mud tank and shakers, which are part of drilling operations. The drillers pump clean mud from the tank down the hole as they drill; this mud plays an important role in lubricating the drill bit, carrying larger bits of rock (cuttings) back out of the hole, and more. When the mud is pumped back out of the hole, the shaker vibrates the mud to separate out cuttings so that the mud can continue to be circulated through the well.