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The Kittsondale Tunnels are a pair of stormwater tunnels and related structures that drain portions of St. Paul, Minnesota, into the Upper Mississippi River. The system consists of two main tunnels, Kittsondale East and Kittsondale West, and a series of stair-like storm drains known as "flight sewers." Four of these flights are unique helical structures that resemble oversized spiral stairs. The largest flight takes 7 turns around an open shaft over 20 feet wide and 100 feet deep, resulting in a structure that’s been compared to the Leaning Tower of Pisa.

Completed between 1929–31, the tunnels were originally a combined sewer serving an area west of the Minnesota State Capitol known as The Midway. In 1938 the Twin Cities constructed a new metro-wide sanitary sewer system and the Kittsondale Tunnels became exclusively used to transport stormwater and surface runoff in the growing neighborhoods along its route.

During the past 25 years the tunnels have become a popular venue for urban explorers and street artists such as Deuce 7, with Kittsondale West known internationally as the Triple Helix Tunnel. The structures can be dangerous due to the presence of carbon monoxide, volatile organic compounds, and the risk of flash flooding. In 2010 a localized thunderstorm created a sudden high flow that resulted in the death of an explorer at Kittonsdale West.

Background
Norman Kittson (1814–1888) was a prominent citizen in the early history of Minnesota. In the 1840s he helped develop the Red River ox cart trade route which connected the Mississippi River head of navigation at St. Paul with Pembina, North Dakota. He then became a steamboat-line operator and railway entrepreneur. After retiring from from business, Kittson was a national figure in horse racing and owned a large farm named Kittsondale near what is today the intersection of Snelling and University Avenues in St. Paul's Midway area.

Midway was so named because of its location halfway between downtown St. Paul and Minneapolis at a key transportation point. After being platted in 1895 the area rapidly developed. At the same time, the Twin Cities were also gaining a national reputation among engineers for the ease by which extensive tunnels could be dug in the St. Peter Sandstone. Underground tunnel networks began serving as breweries, tourist attractions, industrial sites, mushroom farms, and as utility routes. To improve water infrastructure in the fast growing Midway area, two new mirror-image tunnels were planned.

Stuctures
Construction of the tunnels began in the late 1920s and completed in 1931. Though not connected to eachother and flowing in roughly opposite directions, the route of both tunnels start in the area that was once Kittsondale farm, after which they are named. The system was originally a combined sewer, but after construction of the Minneapolis-Saint Paul Metropolitan Sewage Treatment Plant in 1938 connections were modified so that the tunnels handled mostly stormwater.

Flight sewers
The Kittsondale Tunnels contain several structures in the form of staircases known as "flight sewers", which in the technology of the day were used to dissipate the hydraulic forces of large volumes of water over steep elevations. Flights are not uncommon in sewer systems, but Kittsondale is unique in that four are helical, taking the appearance of oversized spiral staircases.

Kittsondale East
Kittsondale East, completed in 1929, is over 3 miles long. It begins under the intersection of Snelling and Hamline Avenues, then travels generally south-east under Interstate 94 to Ayd Mill Road, where it follows a ravine which was once the course of Cascade Creek. The creek no longer exists and surface runoff from this watershed now flows entirely through Kittsondale East. The tunnel discharges at the Mississippi River bluff near West Seventh and Bay Streets, three-quarters of a mile upstream from where the creek originally joined the river. RAMSEY This tunnel has many formations made of flowstone, similar to that found in natural solutional caves.

Kittsondale East features a particularly notable spiral "flight sewer" directly beneath the former creek near the Canadian Pacific Railroad right-of-way where Jefferson Avenue crosses Interstate 35E. This structure handles a vertical drop into the Mississippi River gorge that was once a natural waterfall over 80 feet high. The spiral is constructed of concrete and "cast in monolith." It is 20 feet in diameter and over 100 feet in vertical dimension, with 7 turns of 24 steps each wrapping around a central open shaft. Additional flights leading to and from the spiral bring the total steps in the structure to 250. The result "suggests a subterranean Tower of Pisa". The spiral and outfall structures alone cost more than $500,000 to build in 1929.

Kittsondale West
West Kittsondale tunnel, completed in 1931, is just over 2 miles long and not associated with any known historical stream. It begins in the Union Park neighborhood one block north of University Avenue at Aldine Street, travels southwest under Interstate 94, and outfalls into the Mississippi River gorge just south of the Lake Street-Marshall Bridge. This tunnel has no flowstone.

Kittsondale West has three spirals in different locations, earning it the title Triple Helix Tunnel among urban explorers. The main structure resembles the Ayd Mill helix and is located under the intersection of University and Fairview Avenues. The other two are smaller diameter spirals made of red brick and are situated at points where various branches join the tunnel. Of interest to urban explorers, the stairs of the small and large spiral structures turn in opposite directions.

Urban exploration
In recent years that reputation has grown exponentially among urban explorers, attracting them from as far away as Alaska and Australia.

On the way out, as we approached the river again from whence we had set out, we encountered the familiar Kittsondale tunnel phantom, a mist of water from a shaft in the ceiling, which from a distance resembles a human being walking towards you, because of its constantly changing form.

Accidents
On Sunday,

An urban explorer died Sunday after being swept into the Mississippi River in St. Paul when a bluffside tunnel he and a companion were exploring filled with rainwater during a thunderstorm.

Ian William Talty, 30, of Woodbury, died despite a frantic rescue effort by a St. Paul police officer and several students from the nearby University of St. Thomas. Talty's companion swam to shore and survived.

The men, who were exploring and photographing the tunnel, became trapped by rushing water when a thunderstorm erupted just before 10 a.m. They were swept into the river south of the Lake Street-Marshall Avenue Bridge, on the St. Paul side of the river.

Breid "made his way to shore and started screaming for help," Zaccard said.

Three students from the University of St. Thomas crew club who were helping take down an old dock on the Minneapolis side of the river heard his cry for help, called 911, jumped into motorized aluminum boats and made their way across the river.

"They were done with their work when they heard the yells," said Doug Hennes, a St. Thomas spokesman. "They couldn't see the person ... but they ran down, got the boats out and away they went."

The three students -- Danielle Assie, Jim Portmann and Kyle Smisek -- were joined by an unidentified member of the Minneapolis Rowing Club, Hennes said.

Arriving about the same time was a St. Paul police officer, who commandeered one of the boats and went with a couple of the students to look for Talty, Zaccard said Sunday.

They found him about 500 yards south of the bridge.

"Jim and I were in one boat and a St. Paul police officer got in the launch [boat] with us," Assie told the St. Thomas Web-based publication Bulletin Today. "We went up and down the river a couple of times looking for anything ... the third time, Jim saw a backpack floating in the river."

It was Talty. The students and the St. Paul police officer pulled him into their boat.

By that time, dozens of police officers and fire and paramedic personnel had arrived, Zaccard said.

On shore, the police officer and the students administered CPR. Within seven minutes of the initial call, a police boat arrived to rush Talty to the rowing club for further CPR, Zaccard said.

Hennes said the students were shaken up afterward. "They're disappointed they didn't get there quicker," he said. "Who knows what might have happened if they had?"

Talty was taken to Hennepin County Medical Center in Minneapolis, where he was pronounced dead, according to the Hennepin County medical examiner's office.

An autopsy is planned before the official cause and manner of Talty's death are released and the case remains under investigation, the medical examiner said.

"They pulled him out of the water, and I was hoping for the best," Deputy Fire Chief Dave Galbraith said. "But ... he succumbed."

Questions remain

It was also unclear Sunday how high up the tunnel was from the river or how popular the immediate area is for urban exploring.

Zaccard and Galbraith said the tunnel is among several found along the river bluffs. It is not unusual for water to flow through the tunnels during a storm, they said.

"A lot of people like to go down there exploring," Galbraith said. "I guess that's what these guys were doing."

Over the years, St. Paul's bluffside caves have drawn many urban adventurers who explore and sometimes photograph tunnels, caves, rail tracks, large drains, deserted factories and other rarely seen areas.

Talty, apparently an avid urban adventurer, took photographs that are posted on at least two websites dedicated to urban exploring.

Zaccard said he did not know if the area was marked as "no trespassing" like several tunnels and caves on St. Paul's West Side where urban explorers have died in years past.

The tunnel that flooded Sunday has not been the site of any previous accidents, although authorities have repeatedly warned that any such formation poses potential dangers, he said.

"We've had several young people killed over the years from carbon monoxide fires in these tunnels and caves," he said. "Now we've had a drowning."