Without warning, the earth began to shift beneath their feet and the trio staggered on the rolling surface. From deep within the ground came a brief but ominous rumble. Harbrace stumbled and would have fallen as the ground shook had not the two younger men caught him. The shock was over in less than a minute.
"My God," Harbrace breathed, "not again."
He spun and looked towards the river. A wash of waves from the flowing current lapped against the bank but from the center of the stream the waters continued to boil. All three men silently watched for a full minute. From the south where the tail of the convoy was still visible, a light survey car came racing back down the road towards the river.
It slid to a halt beside the bank and Hall, the senior hydro engineer, leaped out and came running towards the director and the two junior engineers.
"Is it still pumping?" he panted anxiously as he surveyed the waters.
The four men eyed the boil for another half minute. Now it was just a churning pool in the middle of the waters, no longer bubbling higher than the surface of the waters. "It's still pumping," Hall muttered, "but something's wrong."
He jumped for his car and grabbed the radio. "Swenson, Baker," he called, "hold it up. Get that pump-monitoring rig back here on the double. And get the rest of that gear turned around and headed back this way. We've got more trouble."
The other three men had walked to the survey car. "What do you think's wrong," Harbrace asked.
"I dunno," the hydro engineer said. "Maybe the shock triggered the pile dampers on one of the pumps. Maybe something else." He squinted at the barely churning waters over the bore hole. "Can't say until we get a monitor on those pumps. If it's just a malfunction in one of the units, I can dump another one down there. If it's something else, we'll have to see then. One thing's sure, they aren't all pumping."