Meagan Thompson, Associated Press
Brian Olmstead, general manager of the Twin Falls Canal Co.,<BR> provides a tour of the tunnels that helped drain saturated farmland.

TWIN FALLS, Idaho (AP) — Deep in the Rock Creek Canyon, south and east of Twin Falls, a long-forgotten remnant of southern Idaho history is concealed by a dense patch of poplar and sage.

Like its history, the entrance to the 90-year-old tunnel through the solid rock canyon wall is obscure.

Fewer than a half-dozen people have known about the existence of the Klaar Tunnel — and none of them even know how it got its name.

But nearly a half-mile past sunlight, a low, persistent rumbling proves to be a torrent of water pouring from a crack in the rock.

"They must have known that this (water pocket) was here and then blasted their way toward it," said Brian Olmstead, Twin Falls Canal Co. general manager. "I'm sure that after they found it they just decided to call it good."

The Klaar is just one of 49 tunnels that form a 21.6-mile system blasted through the basalt rock under Twin Falls in a desperate effort to drain saturated farmland.

Ninety years later, few people know they exist and fewer still have even seen their entrances. But as the city grows and spreads out with new neighborhoods, builders, city officials and the company that dug them are rediscovering what lies beneath Twin Falls' streets and homes.

The tunnels are the legacy of more than 350 men who worked for the Twin Falls Canal Co. in a 25-year battle to control water in the south-central Idaho desert.

At least 20 men died in that battle. The only monument marking their sacrifice is a typewritten list adorned with dime-store gold stars buried in canal company records.

After the completion of the Milner Dam in 1905, Snake River water was diverted to irrigate farmland around the Twin Falls town site.

The desert bloomed, but canal company founders soon learned that the water could not drain quickly because of basalt rock under the soil. It wasn't long before farmers were losing boots while trying to walk through the mud in their fields.

"They tried everything to bring down the water table after Milner (dam) was built," said Olmstead. "They dug tile drainages and drilled wells, but what they found was that by digging tunnels 30 to 40 feet below the surface, they could drain some of that water from the top and bottom."

The idea was simple: Cut tunnels, then drill vertically from the surface to create drains that would empty directly into the Rock Creek Canyon.

The task, however, would prove anything but simple.

In 1926, a crew of about 75 men drilled a small hole into the canyon wall with a mining drill shipped in from Montana. They packed the hole with 50 pounds of dynamite.

"The blast shook the town; water came out. It was the beginning of the Fish Hatchery (Tunnel)," wrote E.C. Green in a 1927 edition of the Irrigators Handbook.

That tunnel, which starts behind what is now the College of Southern Idaho Fish Hatchery, started one of the most ambitious construction projects in Twin Falls history.

Green, who would become superintendent of drainage for the then-Twin Falls Land and Water Co. one year later, helped bore six of the 49 tunnels.

He would also be the first to question the financial cost of the effort, though the toll on the workers received little attention in his writings.

Most of the tunnelers were killed when explosives detonated prematurely. The company paid Depression-era workers as little as $5 per foot, spending about $300,000 between 1926 and 1951. The total cost was more than half its total operating budget during that time.

"It almost bankrupted the company," Olmstead said. "I think they began to wonder what they had got themselves into."

Company officials knew of no other community or private business that had ever attempted to drain hundreds of square miles in the same way.

In 1951 they declared it a success and stopped digging.

In the years that followed, local newspapers reported that homeless men and women used the tunnels as refuge during winter months — the temperature deep in the rock remains at a near-constant 54 degrees.

By some accounts, bootleggers used them for distilleries, which were short-lived as law enforcement quickly caught on to the underground business.

Today the tunnels are almost exactly as they were made — preserved by nature and kept from human contact. None are marked, and those accessible to the public have been sealed with concrete except for a small hole with steel bars.

The Times-News was given a tour of the Klaar and another tunnel by Olmstead. The locations are kept secret to prevent trespassing on private property and the potential for tragedy because many tunnels lack breathable air.

Olmstead asked that locations of tunnel entrances not be published to prevent trespassing.

Most are about 6 feet in height and 4 feet wide. In the Klaar tunnel, about 18 inches of water covers the floor. The ceilings are covered with mineral deposits from water trickling down hundreds of holes drilled decades earlier.

Rusted steel spikes are still wedged in cracks in the tunnel walls, left by engineers to mark 100-foot intervals.

Those engineers, laid off from failed Montana gold mines, kept the tunnels perfectly straight, though in the Klaar — and some other tunnels — they turned abruptly to reach flowing water.

More than 2,000 feet inside the Klaar, where the air is thin, the shaft dead-ends at the rumbling waterfall.

"They must have hit a good point here and decided to call it quits," Olmstead said.

Local lore has it that some tunnelers were killed here when they came close to the water pocket and the pressure blew the rock face at them.

The now-capped Orchalara Tunnel, which extends from a point near St. Luke's Magic Valley Hospital and parallels Filer Avenue, is believed to be the longest tunnel at almost 2 miles.

In the years that followed, the tunnels were mostly forgotten.

After the canal company declared victory in 1951, the massive project and the tunnels themselves faded from memory.

Houses, streets and business sprang up over them, with builders often unaware of their presence.

Only recently have city and canal company officials begun to pay much attention to underground Twin Falls.

Rapid growth between 2000 and 2006 accelerated conversion of once-drained farmland to subdivisions on the south side of the Rock Creek Canyon.

As they prepared building sites, developers intentionally or unknowingly plugged the vertical drain shafts. The result was a decrease in waterflow and an increase in contaminants draining into the tunnels.

Builders are now required to consult with the city and canal company about where tunnels might run. The canal company is also trying to find anyone who might have maps, photos or other information about the dig.

"The drainage tunnels are really a big part of Twin Falls history that has been forgotten..., and I think it's something that we need to preserve," Olmstead said.