Fifteen Days Undergound

 

Eric Korte and Dave Vlasin
District Water Quality staff, investigate the Beltline

By Sage Passi

Notes from the Underground

The mission that Dave, Eric and the Barr team have undertaken this past month puts a whole new spin on Notes from the Underground, the title for Dostoevsky’s existential novel I read in high school. When I heard that our water quality monitoring staff would be spending 15 days underground walking the Beltline and the Battle Creek tunnels I had to investigate.

When Barr engineer Nathan Campeau came to our office last month on a Wednesday evening to set up for his Board presentation on the “Beltline and Battle Creek ” missions, he asked me if we had any old pictures of the Beltline. That request was just the impetus I needed to dig deeper to explore some more mysterious “tales from the underground”.



Sam Rediner, (left) and Nathan Campeau, Barr Engineering (right)
conduct an inspection in the Beltline tunnel.

I’d covered this beat before in a previous Ripple Effect blog article and had already become fascinated with the history of this extensive tunnel system built in the 1920’s that carries the flow of water from Phalen and Beaver Lakes to the river. Images of the earliest days of the Beltline’s predecessor tunnel with its “Platteville Limestone rubble-masonry walls, granite floor and gargoyles, with curiously wrought iron spouts that vomit water in the tunnel,” from an old 1894 Engineering News article description had lodged in my memory. 
 
Today the Beltline has over 33,000 feet of tunnels with five major branches. It’s almost five miles long. It contains circular and horseshoe sections that range in diameter from four feet to 12 feet. The velocity of the stormwater traveling through this pipe system can be quite intense. The design discharge for the beltline is 2,000 cubic feet per second.




The Beltline and the Battle Creek stormwater tunnel systems
 under inspection in 2015 are marked in red.

 

Old photos unearth intrigue about Beltline

I was not disappointed with my discoveries from that night’s research. The old photos I uncovered from our Laserfiche files added to my intrigue about the Beltline. I haven't seen a horse on a construction site in a long, long time.
 

The Beltline Sewer was constructed in the late 1920's with the help of teams of horses.

 

Phalen Creek tunnel construction in the late twenties



Cold, wet and in the dark

So, what has this team been doing?

Walking underground in a stormwater tunnel system, the team is performing detailed inspections of the Beltline Mainline, beginning at the Mississippi River and working their way upstream toward Phalen Lake. The task has to be done every five years. When they are done with their mission, they will have investigated a total of over 38,000 feet in both the Phalen and Battle Creek tunnel systems. The information they gather will be used to make recommendations for repairs for these sewer systems.

Writing observations in the inspection log.
Water from the pipe may be brown due to iron-enhanced bacteria.

That’s seven miles. Inch by inch. In the dark. In the cold. Underground. It’s quite a heroic effort, in my humble opinion.

When Dave and Eric finally came up for air, so to speak, after walking the Beltline for many days during February, I knew I had to document their story twenty-first-century-style.



Barr staff take notes during the inspection.at the
entrance to the Beltline near the Mississippi River,

Here’s what Dave had to say.

“We entered at the Mississippi River’s edge. The first two days we had rescue services on site at both our entrance and egress locations. The pipe was slippery and at times there was standing water up to our knees and thighs. We needed more intensive safety precautions for those first days of inspection because that section of the Beltline was the most dangerous. If something happened up stream we could be washed away into the river... "



The Beltline drains to the Mississippi River.
This was the entry point for the tunnel inspections.

“Was it scary?”

I realized as soon as I said it that my question was rather understated. Downright lame as a matter of fact, but I get claustrophobic just trying to pull a sweater over my head.

“It could have been,” responded Dave.

“The whole inspection can be very, very dangerous. The likelihood of something happening is very slim. But you’re underground. It’s a confined space. You just never know if something can happen. A tanker spill could occur up above ground, travel to the sewer and get in the water… A bunch of things could happen. But the likelihood of any individual thing happening is very, very small."


Rescue Services were on hand when the team entered the Beltline at the river's edge.



Dave models tunnel safety gear.
The yellow tool is an air monitor.

Not for the timid

"So what other kind of precautions and safety measures do you need?" I asked.

My imagination is working overtime now. Dave continued with his explanation.

"When we enter, we use confined space equipment. We have a tripod, wenches and fall protection gear, harnesses, hard hats, insulated chest waders and boots. We also have an air monitor, a PFD (personal floatation device) and flash lights. We also bring supplied air just in case something would happen due to engulfment."

Just that word, “engulfment” makes my imagination run wild. Dave seemed pretty calm about it all. I can tell he is the right person for the job. He continued with his story.

 

A good support team is crucial

 Surface attendants monitor the team while
 they are underground to insure their safety.

“We have two separate surface attendants. We have one downstream and one upstream at the egress (exit).

When we enter, as we work our way back up the pipe system, attendants leapfrog back and forth while we continue up the pipe so we always have one person ahead of us and one person behind us.

When they do the leap frog in the middle of the day we break for lunch. We spend the whole day in the pipe."




Daily safety meetings are held to prepare the team for issues
that may come up during each inspection.



 

If you hear three horn blasts ... get out!

"We have a safety meeting each day to run through the potential hazards. Everybody is involved… surface attendants included. We use traffic cones around the manholes. We try to have a vehicle parked near the manhole and have a surface attendant within a few feet of the manholes. Every half hour we check in using a two way radio. If for some reason the two way radios don’t work we switch to using air horns. Then we use a series of air horns – we use one horn blast to communicate that we are ok and the surface attendants confirm that they have heard us by waiting until the sound waves from our signal fade and they repeat this horn blast so we know that they have heard us. In case of an emergency we switch to a three horn blast."

Moral of the story: If you hear three horn blasts you head the other direction and get out!!!

Graffiti, bats and waterfalls ... oh my!

I inquired, "What are you finding in the tunnels?"

Dave answered,

“Small cracks that your fingernail can’t get into, exposed reinforcement bar, old blocked pipes that are capped, surface aggregate that’s coming through, surface damage, possible failures, sags, pipe deformations, sediment deposits, graffiti, roots, vermin, raccoon scats, one live raccoon. A pair of beady eyes at the end of a tunnel.

We have a coding system for a variety of conditions we observe and record using NASSCO’s Pipeline assessment and certification program. Everything gets recorded."

Graffiti in the Beltline



A waterfall caused by a seep draining
into the Beltline tunnel.

“Did you see bats?”

Dave shook his head. “No bats.” No small favor. 

 

“Can you tell me anything else about the experience?” I’m digging around for anything else here…..

“Initially it’s very interesting to do the inspections, especially the first few days. Come that third day in a row, it can be a grind. You are fifty feet below ground, there’s no daylight. Sections were really cold.

One of the nice things about being fifty feet below ground is that the tunnel buffers the wind. Near Lake Phalen, though, with the big trash racks exposed you’ve got the big wind coming through,"  Dave continued.
 
"The afternoon chili lunches help a lot.”

The end mission:
Get done before the spring rains start

In the coming few days, Dave Eric, Nathan and Sam will be heading into the “Mechanic” stretch of the Beltline pipeline and then finish off with the Battle Creek Tunnel inspections. That’s still another three to five days to go.

They have to get done before the spring rains fall and the lakes start thawing. This year is an awfully early spring. Let’s hope their mission gets accomplished.