"You two hear?" Hall demanded.

"Loud and clear," Alec replied.

"All right," Hall ordered, "let's get with it. This is a general order. All vehicles and personnel not directly involved, pull back a full mile."

Men and equipment began moving away.

"O.K., Number One crane, lift 'em."

The crane operator on the near bank eased his gears into motion and the six-ton tractor lifted into the air with Alec and Troy aboard.

When it was five feet above the ground, the crane on the opposite sh.o.r.e began hauling the draw line and the vehicle swung out over the water.

"Now listen closely," Hall ordered the pair in the swinging vehicle, "from this point, you are in control. Stop your slide over the hold by just yelling "Stop." Number one crane is your up and down operator and also will pull you towards this bank. If you need to go forward or backwards when you get inside the hole, just say which way and both crane carriers will move in the direction you want. Got it?"

"Affirmative," Alec replied.

A second later he yelled "Stop." The pull halted and the heavy vehicle swayed just a foot above the churn in the waters. Alec waited a minute until the tractor quite swinging and then ordered, "Let's go down."

Number One crane began paying out cable and the tractor and men slipped beneath the surface of the turbulent waters.

Surging, silt-laden water rushed upwards past the sides of the heavy cab and swirled around Troy and Alec. Both were clamped into the seat by a steel mesh belt and the waters tore and whipped at them. Despite the six-ton ma.s.s of the tractor, both men could feel it quiver against the thrust of the waters rushing and breaking against its undersurfaces. Although both had turned on their powerful suit lights, the lamps made only a dim glow in the surging waters. When the tractor had dropped some thirty feet, it was Troy who yelled "Hold it!"

The downward motion stopped.

"Let's get back against the wall," Troy yelled over the roar of the torrent. "Those pumps are pretty well to the center of the bore and I don't want to come down on top of one of them, even the bad one. Move back!"

On sh.o.r.e, both cranes began inching up stream.

In the thundering bore, the tractor b.u.mped against the wall of the hole. "Hold it," Troy shouted. The carriers stopped. "Take 'er down."

Again the ma.s.sive vehicle descended into the depths. The roaring became louder with every foot and the constantly dinning noise rattled the earphones of the crane and carrier operators. Hall stood on the bank, his eyes glued to the thread of cable vanishing beneath the waters.

The tractor was b.u.mping against the wall with more violence and the engineers could feel it tip and sway as the turbulence increased from below.

"I think we're too close to Number Two pump," Alec yelled. "Let's get a little more offsh.o.r.e." On the far bank, Number Two crane began hauling the pulley towards him.

The undersurface bobbing lessened. "That's good, Number Two," Alec shouted. The downward motion continued.

As suddenly as it began, the turbulence almost ceased and the sound diminished in the black, watery hole. The big nuclear pumps stood thirty feet high with their great jets at the top. The tractor had descended blow the level of the jet thrust. At the same instant, there was a forward motion and the tractor began to sweep toward the downstream wall of the bore.

"Drop us, fast," Alec commanded. "We're being sucked."

Number One crane operator slammed his release b.u.t.ton and the tractor fell with a jarring crash to the floor of the catch basin. On the floor, its ma.s.s held it in place against the drag of the three huge pumps and the natural flow of the water.

The water was clearer and their lights penetrated a few feet into the black-green h.e.l.l around them.

"You see it?" Alec asked his partner.

"Not a thing," Troy replied, "but we can't be more than a few feet from it. It's got to be somewhere in front of us and I think a little to my side. The suction drag doesn't seem quite so heavy over here."

"Number One," Alec instructed, "give us a fast one-foot lift and drop it immediately. The current will move us."

The operator took up the slack in the cable and then gave a short burst of upwards pull and slammed the release. The tractor lifted and was carried forward about five feet before it slammed down again and stopped.

"There it is," Troy yelled, aiming his light to the right front of the tractor. The beam picked out the ma.s.sive casing of Number Four pump.

"Let's get in close." On instructions from the submerged engineers both cranes lifted and hauled briefly. The tract slammed into the bulk of the disabled pump. Troy and Alec played their lights over the plate.

"This is the bottom plate," Alec said. "It's tipped all right. Got to ease around to one side."

Again the cranes dragged and lifted and the ma.s.sive tractor sc.r.a.ped along the bottom plate of the overturned pump. Suddenly the vehicle whipped forward. "Drop it," Troy yelled, and the carrier smashed to the basin floor.

They were alongside the main outlet tube, now tilted downwards on an angle towards the floor of the basin. Below them and under the curvature of the tube was the pile housing. The explosive had to be placed at the point where the pile housing, the pump base and the outlet tub met.

Currents of water still swirled around them and tugged at the two men.

But it had much less force than during the downward descent. Alec unclamped the seat belt, then slammed his magnetic clamp suit boots against the outer plates of the carrier. His suit buoyancy dragged him into an awkward crouching position and he swayed and fought against both the upwards lift and the current swirl.

"Let's go," he said.

A hundred and seventeen feet above them, Hall and the crane operators could hear the hollow clang of the magneboots as the two engineers inched their way back alongside the tractor to a spot where the tractor hull touched the pump housing. Alec cut one foot loose from the vertical side of the tractor and slammed it against the pump base and then quickly shifted the other foot and began forcing his way down under the curve of the tube. Troy followed.

In the shelter of the base and tube, the current no longer pulled at them and it was only the suit buoyancy to battle. It took them three minutes to struggle their way to the juncture point. Alec wedged himself in with his back against the housing above him and carefully began unwinding the explosive belt he was wearing.

With his feet clamped on the vertical wall of the pump housing and knees locked in a skier's stance, Troy handed over the first of the magnetic clamps. Alec took it and carefully clamped the end of the plastic explosive belt against the pile housing. They worked slowly but steadily until the entire band of explosive was in place along a five-foot arc of the housing.

During the entire operation, neither man spoke and on sh.o.r.e, the listeners could hear only the heavy breathing of the pair and an occasional m.u.f.fled sound of a clamp going into place.

When the plastic was locked down, Troy carefully unclipped a timer fused from his belt and handed it across. He spoke for the first time since they left the tractor. "It's set for seven minutes." In the wavering light of the murky waters, he saw Alec glance up at him and then gingerly insert the fuse into the explosive.

"Get moving," Alec ordered. Troy started inching his way back along the pump housing wall. Alec waited until Troy moved into the gloom and almost out of sight, then flipped the water-tight switch that activated the fuse.

The device was armed. In seven minutes, if the pile didn't go critical before then, the charge would detonate--whether they were back on the surface or not.

He shoved himself free of the pile housing and followed Troy back along the wall of the base. At the hull of the tractor, he made the foot-at-a-time crossover and again fought suit and current to get back to the cab. The seconds ticked off into the first minute and into the second. Ahead, Troy had reached the aperture of the cab door and reached in to grasp the end of the steel safety belt. He hauled himself into the seat and looked back for Alec.

The other engineer had just reached the cab. He swung a leg over the sill and at that moment, a surge of current whipped his suit. He twisted, grabbed for a handhold and missed and shot up towards the surface. In that same instant, Troy shot up out of the seat, holding the end of the belt in one hand and grabbing for Alec's ankle with the other. He caught it and clutched. "Up, fast," he screamed.

The tractor snapped up under them and threw both men against the seat.

Alec seized a control handle and hauled himself into the seat as the vehicle surged upwards. Under full power, it was whipping towards the surface and now, the water pressure was holding them down. The timer pa.s.sed the four-minute mark when the six-ton carrier burst out of the water in a geyser of spray. The cable whipped and almost threw them from the cab. Then there was a spine-snapping side jerk as the Number One crane operator began smoking the cable pulling them to the sh.o.r.e.

Thirty seconds later the tractor slammed to the ground. Hall and the crane carrier driver were waiting. They reached in and jerked the two engineers from the seat and half carried them to the rear of the ma.s.sive crane carrier. The operator had already leaped from his cab and was lying p.r.o.ne, face down on the ground.

Troy and Alec, together with Hall and the driver, stretched out alongside each other in the dubious shelter of the carrier and waited.

The seconds ticked off. A minute later, a small geyser of water shot up a few feet from the surface of the water and seconds later they heard a slight rumble. Then there was only the sound of their breathing and the rush of water in the river.

Hall jumped up first while the others were still scrambling to their feet. He raced to the radio after a hasty look at the river.