“What are they building there, anyway?” is a question motorists might ask upon seeing cranes and other machinery looming behind construction fencing by Interstate 90 and Cleveland’s Memorial Shoreway. Even when this work is completed, and the equipment, dust, and safety-vested crews are gone, what remains of the work won’t yield an obvious answer, as it’s mostly taking place underground.
What they’re building are massive storage tunnels — colossal projects that involve tried-and-true excavation techniques, modern technology, and dedicated teams of top-tier engineers, specialists, and laborers.
Seven storage tunnels are being built to fulfill the Northeast Ohio Regional Sewer District’s Project Clean Lake goal of all but eliminating sewage overflows into the Cuyahoga River, area streams, and Lake Erie, by 2035.
During rainstorms that otherwise overload the capacity of our aging combined-sewer system, these new storage tunnels capture and hold millions of gallons of combined wastewater and stormwater and keep it from discharging to the environment.
A subterranean tour of the eastside Doan Valley Tunnel and a walkthrough of near-surface projects adjacent to the in-progress Westerly Storage Tunnel comprise a crash course in what’s involved in imagining, designing, and building these infrastructure marvels.
A question I am often asked is whether it is possible to go down into the tunnels. People are curious about these massive structures, and want to experience what it’s like to be inside of one.
For various reasons, among them safety and liability, it is rare for the general public to tour a tunnel project. For this article, I was given access to the Doan Valley Tunnel (DVT), an 18’-diameter, two-mile-long storage tunnel that will keep 365 millions of gallons of combined sewer overflow (CSO) from polluting local waterways each year.
The main construction staging site for this dig sits at the edge of MLK Boulevard, near University Circle. There, a 50’-diameter vertical shaft provides access to the mouth of the tunnel, 120 feet underground.
On the day of my visit, the overcast sky matches the gray mountains of shale that has been excavated and lifted from the hole, one railcar at a time, by a brightly-painted yellow crane that sits in contrast to its dull surroundings. Nearby, workers assemble short lengths of railroad tracks that will be lowered into the shaft to accommodate the train that moves in and out of the tunnel, all day and all night. The longer the tunnel gets, the more rail is needed. “Everything comes in and out via crane,” says Construction Supervisor Karrie Buxton.
Buxton has been with the District for seven years, having started out with a small design firm working on slope-stabilization projects before moving into construction management. “I did a lot of structural work for bridges, big spans, and deep foundation work,” she said. “It lent itself to tunneling, because it’s all soil and rock mechanics, just deeper in the ground.” Before joining the District, she gained municipal experience as Construction Manager for the City of Shaker Heights. “I wanted to get back into a civil environment, where you’re challenged and feel like you’re giving something back,” she said.
From the “crow’s nest,” a metal platform near the lip of the shaft, we watch the third-shift workers exit the ground to head home. Karrie explains the “lock-out tag-out” procedure, by which the crews keep track of who is in the tunnel. Each worker signs out a pair of numbered brass tags, keeping one on his or her person and the other on a pegboard mounted next to the tunnel shaft. That second tag is moved from the “In” column to “Out” every time the worker leaves the tunnel.
We prepare to descend the metal staircase leading to the tunnel. “When you’re 200 feet below, you still get a little excited,” Buxton says. “Even when you’ve done a lot of heavy industrial projects, once in a while you catch yourself and say, ‘Yeah, this is really cool’.”
The crane unloads another railcar, also referred to as a “muck box.” These carry the spoils that come straight from the cutter head excavating at the other end of the tunnel. Circular blades mounted on the cutter head spin and scrape away at the rock face. The cutter head spins and advances about five feet per hour.
Some tunnel projects use a conveyor-belt system to transport the freshly-dug rock, but the DVT operation relies on a locomotive running in and out of the tunnel. “Every five feet of mining fills up eight muck cars,” says Buxton. “We have two trains running 24/7, and we’re pulling out about 1,900 cubic yards of shale every day.”
Most of the ground material in Cleveland is called Chagrin shale. “It’s a weak rock, easy to get through and not very abrasive, compared to granite, which contains quartz and is very abrasive, and can wear down the equipment,” explains Mike Piepenburg, a project geologist with Mott MacDonald, the design firm for several recent Sewer District tunnel projects. “Although shale is easier on the machine, the parting surfaces are horizontal, making for different dynamics of how ground relaxes and behaves, and requiring a somewhat different approach to traditional excavation.” (One incidental advantage of mining through shale is its re-use possibilities, such as backfill for roadways.)
The crane hoists a muck car out of the shaft, empties the shale on the ground, and returns it underground. The “bottom lander,” a crew member down in the shaft, hooks up chains to the next car, and communicates by walkie talkie to the “top lander” and the crane operator to make sure the cars and other materials descend and ascend safely. There are nine cars to each trainload.
Along with the muck cars are specially-designed “segment cars,” onto which the crane lowers the segments that will be pieced together to form the rings that make up the tunnel lining. Each ring consists of six segments, made of steel fiber reinforced concrete, which are manufactured in Macedonia, Ohio. “We’re fortunate to have a manufacturer so close to our project locations,” said Buxton. On average, the work proceeds at a rate of 14 rings per day — about 70 feet.
While the muck cars unload, Karrie and I speak with Martino Scialpi, Senior Engineer for the DVT tunneling contractors McNally and Kiewit. Scialpi has been in the business for about 13 years, but his interest in tunneling dates back to his childhood in Italy. “Tunneling was my thing since I was a kid,” he said. “I really wanted to be in this industry, and I feel lucky, because that doesn’t always happen. I actually got to do what I wanted to.”
Scialpi studied mining engineering in college, and his first tunnel job was with an Italian contractor, in Ethiopia. He has worked on projects in Hong Kong, Austria, Turkey, Italy, Australia, China, and now Cleveland. “We’re making great progress here. It’s a fairly young group of people. I am so proud to be part of this.”
He points out a small, glass-faced box mounted on the wall of the shaft. It contains a statue of St. Barbara, the patron saint of miners. “It’s more of a European tradition, but it’s growing here, too,” said Scialpi. “Being from Italy, I had to bring a St. Barbara!”
The muck cars now empty, we climb aboard the locomotive, and begin our two-mile journey to where the tunnel boring machine, or “TBM,” is steadily scraping its way ahead. A ride that I anticipate taking five minutes turns into 10, then 15, then 20, the walls of the 9,000-plus feet of finished, concrete-lined tunnel a shadowy blur. The train engine gives off a lot of heat.
Running the length of the tunnel are several conduits: a ventilation system — a flexible “bag” that extends like an accordion bellows as the tunnel gets longer — as well as utility pipes carrying water, electricity, and the grout mixture that is used to cement the concrete segments into place as the TBM advances. The “A” and “B” components of this mixture are housed in tanks in an aboveground grouting station and, after being fed down the tunnel to the front of the TBM, are injected behind each segment, where they combine, activate, and set in under 15 seconds.
We finally arrive at the rear end of the TBM, which is steadily digging through shale and installing the final 600 feet of concrete segments to complete the DVT.
This tunnel is a “one-pass” excavation, which means that the ground is dug and concrete lining installed at the same time. Dating back more than 30 years, one-pass is the most significant tunneling innovation in recent history, and in many cases preferred over the older “two-pass” method, in which the hole is completely excavated before the tunnel lining is installed.
The excavation method is determined both by the ground material and the diameter of the tunnel being constructed. “It’s difficult to do single-pass in an eight-foot tunnel, since you don’t have a lot of room to carry the segments and things of that nature,” said Buxton. “Sometimes large is easier than going small.”
Until recently, single-pass had been used primarily in soft-ground tunnel; it hadn’t really been done that often in rock tunneling. “But if something works, and it’s cost effective, and a contractor increases their production because of it, it becomes commonplace,” said Rick Vincent, a design manager in the Sewer District’s Engineering & Construction department. “Some of those contractor evolutions happen relatively quickly.”
The Sewer District has been an innovator in the single-pass method, specifically in the design of the concrete segments that line the tunnel. “We have a good handle on single-pass now,” says Construction Manager Bob Auber, a 26-year District veteran currently managing several large tunnel projects on the east side of Cleveland, including the Euclid Creek Tunnel.
Buxton, Scialpi, and I dismount from the railcar and walk along the platform that runs alongside the TBM, making sure our ear protection and dust masks are in place. Buxton points out tiny red glowing dots overhead, which indicate the targeting system that helps the TBM operator guide the TBM with great precision. (Typically, the machine will arrive within three inches of its projected destination point.)
We walk up to a box that resembles a highway tollbooth. Inside is John Chesser, one of the TBM operators. He is standing in front of several computer screens displaying graphic interfaces by which he maneuvers and monitors the TBM.
Chesser has been in this business for two decades. Initially, his work involved a lot of traveling. “I decided I wanted to stay in town, and lo and behold, there is plenty of tunneling in Cleveland for me to do, so here I am,” he said. “It has been a pleasure being on this machine. It’s clean, there’s proper lighting, and after a while you can sometimes forget you’re underground.”
From the rear of the TBM, an overhead track system with a vacuum apparatus lifts one of the concrete segments from the locomotive and smoothly guides it into position. The rings are built from the bottom up, and a smaller keystone piece completes the ring. Once the ring is grouted into place, the TBM uses horizontal hydraulic jacks to push itself forward several feet, where it will proceed onto the next ring assembly.
Even though we’re steps away from the cutter head, there is very little noise, only a mild vibration and a high-pitched hum. A conveyor belt carries a gray slurry of excavated shale, or “muck,” away from the cutter head and into one of the train cars that sits at the rear of the TBM. A sprayer positioned above the car wets the shale to keep dust from filling the air.
Once the cars are full, the driver will bring the haul back to the shaft and the cars will be hauled up into daylight. In less than a week from today’s visit, the tunnel will be fully excavated and lined.
Rick Vincent has over 26 years of tunnel design experience. “I originally wanted to do bridges,” he says. “I was a structural engineer at a firm that had a tunneling discipline that I got drawn into and really liked. It’s always interesting work, because ground conditions are different everywhere, even within the same city.”
Vincent says that in tunneling, you really have to understand construction methods to do the design. He contrasts their complexity to the relatively straightforward bridge projects he worked on early in his career. “I literally took a homework assignment from college and designed a bridge, and they went out and built it,” he says. “There wasn’t any consideration of the contractor. It’s just a structure and it’s going to hold so much weight, it’s safe and it works, and there you go.”
“Designers can make anything work on paper, but we never have that perfect blank sheet out in the field.”
Ideally, the tunnel construction team is brought in during the design phase to identify constructability problems. “Designers can make anything work on paper, but we never have that perfect blank sheet out in the field,” Karrie Buxton says. “We have other utilities to think about, and the public impact to consider when you actually put the design into practice. We can bring aspects to a designer’s attention things that we have experienced in the field that a designer might not understand.”
“There are some givens — where we have to pick up the flows, where the sewers are, how much flow we have to divert and capture to control CSO,” says Vincent. “That all guides us to where the tunnel is going to be, and we look for the optimum alignment to do all of this with the shortest amount of tunnel.”
A design project manager at the Sewer District will outline the general parameters of the project, including tunnel capacity, as required by the EPA’s mandate to reduce CSO. Then, tunnel design firms bid on the job. The winning design engineering firm works with Sewer District engineers, working from flow-monitoring data to determine the best options for meeting that mandate and the needs of the end users — the wastewater treatment plant staff.
One factor unique to tunneling is what Vincent calls “the eggshell concept,” where the tunnel lining is designed to become one with the ground. “The lining isn’t there to hold back the ground, it’s there to work with the ground in a controlled way,” he explained. “You want the ground to collapse, or ‘relax,’ a little bit.”
Related to this is the judgement involved in being able to measure “stand-up time,” or how long the ground is able to stand on its own, without any support, after it is dug into. This is different for rock, soil, clay, or sand, and the time needed to install the lining is dependent upon how much load it is going to take.
Designers also consider groundwater pressure and many other factors that have some measure of uncertainty. “There’s a lot of data collection, analysis, and interpretations of ground conditions to predict how the ground is going to behave,” said Vincent. “Once you figure out those things, you and the contractors get to be creative with how to actually get that tunnel built.”
The length of the tunnel will influence how many “near-surface structures” will be built. “Where we pick up flows from the existing sewer systems dictates where we need a gate control, or a shaft, or a diversion structure that controls where we’ll channel that water from the surface down into the deep tunnel,” says Buxton.
I visit another construction site on Cleveland’s West Side, not far away from the Gordon Square Arts District. Street sweepers spray down the pavement to keep down dust from work being done on a string of structures linking an existing brick sewer to the new Westerly Storage Tunnel (WST), scheduled to be completed in 2021.
The 25’-diameter WST is the largest of the District’s storage tunnels thus far, but it is the near-surface structures, which redirect the flow from the existing sewer system into the storage tunnel during rain events, that present the biggest technical challenges. “We’re working in a 200-year-old urban environment with many underground utilities,” says Mike Piepenburg as we walk through construction near the West 45th Street onramp to the Shoreway. “We examine old records of what was built to prepare the contractor for what they will face. We also sit down with local water and power utilities to discuss what structures can be relocated.”
Sometimes, a utility can be moved, but more often, especially with older utilities, the designer will have to figure out a workaround. “On the Doan Valley Tunnel, rather late in the design phase, we moved the entire tunnel over one city block to avoid water mains,” says Sewer District Construction Program Manager Doug Gabriel. “Sometimes, what appears in records is different from what’s actually there.”
Piepenburg leads me to a rectangular excavation across which a 100-year-old 81” sewer juts, its brick casing exposed. Despite its age, the sewer is in remarkable condition. “The old masons really knew their trade,” he says, noting the three layers, or “courses,” of brick. The crews have cut out a segment of this brick sewer so that it can tie into the diversion structure they’re building.
During heavy rain events, this diversion structure picks up flow from the brick sewer and directs it into the new WST. After the cranes and machinery is taken from the site, access doors in the pavement and two gooseneck ventilation pipes are all the public will see of the work that has occurred here.
Piepenburg’s role is to make sure the design is implemented correctly, and handle any problems. He started his career as an engineering geologist, studying the ground material for open-cut and drill-and-blast tunneling projects in D.C. and Los Angeles. “That work naturally led to seeing how these things were built, learning construction and then inspection and construction management,” he says. He has supervised tunnel projects in New York, Atlanta, and Puerto Rico, but since 2011 primarily has worked on Sewer District projects. “It has been nice to be home in Cleveland for the last eight years.”
“I’ve always had an interest in construction. My dad was a contractor. In college, I worked for a mechanical contractor, doing piping and HVAC, working in a fabrication shop.”
“It’s a travel business, you go where the work is,” says Doug Gabriel, who currently oversees 35 Sewer District construction projects. “I’ve always had an interest in construction. My dad was a contractor. In college, I worked for a mechanical contractor, doing piping and HVAC, working in a fabrication shop. I spent a summer at Bethlehem Steel, then went to work for a national mechanical contractor in Southern California.” Gabriel’s work with the Kiewit company gave him additional experience in mechanical, electrical, and instrumentation projects at treatment plants, and ultimately brought him to Cleveland.
Gabriel said the transition from being a consultant to working as the “owner” of the project has been interesting. “I’ve always been a hands-on individual, and outspoken, and at the District I can do both,” he says. “I enjoy looking at projects and picking them apart, figuring out what the risks are, and then trying to mitigate those risks in our documents before we put them out to bid.”
At each step of the tunnel design phase — the 30%, 60%, and 90% stages — there are opportunities to guide it and make changes. “By the time you get to 90 percent, you pretty much know what you’re going to build, and you ask, ‘What do I need to put in here to make it buildable, and biddable’,” says Gabriel. He pointed to a foot-tall stack of documents, the bid documents for the Doan Valley Tunnel. “Six books for DVT,” he explains. “Reference info, geotechnical info — you give the contractors as much as you can to get a good quality bid.”
Once the tunnel is designed, it goes out to bid. Contractors review not only the drawings and specs, but also the Geotechnical Baseline Report (GBR), in which District engineers spell out the known ground conditions, based on data collected from ground borings.
Since tunneling is riskier than above-grade construction, the cost of any unforeseen ground conditions is covered by the District. Having all parties understand and agree upon the risk documents results in good bids from the contractors, who do not have to work those unknowns into their bid. “We try to flush out the ‘known unknowns,’ and we apply a budget to those so it doesn’t become something a contractor has to cover with his own money, so that everybody bids equally,” says Gabriel.
“There’s an art to writing these risk documents,” adds Vincent. “You can write a 100-page report that no contractor is ever going to read because it’s too long, or you can write a really short one and not say much, and they’ll add more contingency to their bid to cover those unknowns. I always like trying to figure out where that balance is.”
The best reports are written as realistically as possible, so there are fewer surprises for everybody. “You want a contractor to look at your documents and think they’re fair, that he can come in and get a fair shake,” says Gabriel. “We’ve been very fortunate in getting good high-quality contractors who don’t have to apply a lot of risk money to their bids.”
“No matter what you did during design, things can change quickly, and when those changes happen, you have to be able to jump on them. Geotechnical risk in these jobs is huge. We do a pretty good job of figuring it out, but when you open up the ground, it can be different. It can cost you millions.”
As one might guess, the challenges increase after construction begins. “Then it really gets fun,” says Gabriel. “No matter what you did during design, things can change quickly, and when those changes happen, you have to be able to jump on them. Geotechnical risk in these jobs is huge. We do a pretty good job of figuring it out, but when you open up the ground, it can be different. It can cost you millions.”
Karrie Buxton gives an example of this happening on the Doan Valley Tunnel project, which lies in a flood zone. “We had a flood and lost our consolidation tunnel, which delayed us,” she says. “But it’s nothing that you can’t overcome or work through, it just takes time. It’s all part of understanding the process of what you need to accomplish. There are going to be challenges, but nothing is going to be so big that you can’t find a solution, because you have yourself and a fantastic team with a tremendous amount of support that aid in making decisions. You always feel empowered to make the right call.”
“We’ve been able to work through all our issues pretty expeditiously and fairly,” says Gabriel. “We’ve had no litigation, and no unresolved claims.” Members of an impartial Dispute Review Board are chosen by the contractors and the Sewer District and meet on a quarterly basis to talk about the project and handle any conflicts.
Big tunnel projects like these directly impact Sewer District ratepayers, and need to be managed and delivered effectively and efficiently. “That’s why we set key performance indicators [KPIs] and report our progress each month to our Board of Trustees,” says Devona Marshall, Director of Engineering & Construction. The KPIs revolve around schedule, budget, and meeting the requirements of the District’s consent decree with the EPA.
“Our capital program has drastically increased with Project Clean Lake, both in the number of projects we have to deliver and the money that we have to spend,” Marshall says. To ensure sound financial planning, the District improved its design and construction standard operating procedures, and ultimately its project delivery. Marshall’s department has largely eliminated paper use, having established Sharepoint as its system for document control and workflow approvals. “We’ve made everything more efficient,” Marshall says.
“Our capital program has drastically increased with Project Clean Lake, both in the number of projects we have to deliver and the money that we have to spent. We’ve made everything more efficient.”
To date, the District has invested $1.42 billion on over 60 CSO-control projects that have reduced annual CSO by one billion gallons, and has realized $426 million in savings through value engineering and effective project management.
Keeping the public informed is an important part of the District’s tunnel projects. “You want to make sure that information gets out to not only the neighbors who are in direct proximity of the work, but also those who are just commuting through,” Buxton says. Doan Valley Tunnel construction runs throughout University Circle, a heavily commuter-based route. “It’s setting up construction signage, sending out traffic notices, and notifying the police and fire departments and nearby hospitals to make them aware that you’ll be blocking or restricting traffic flow.”
The number of people working on any one tunnel project is about 100, including a labor force of at least 75 working three shifts, plus the contractor’s engineers and managers, Sewer District support staff, and about five to eight supplemental inspectors observing the work.
Doug Gabriel points to his staff as the key to the Sewer District’s success on these tunnels, which consistently are completed ahead of schedule and under budget. “We probably have the best collection of construction staff of any agency in this country,” he says. “That brings in good contractors and good bids. And if we feel like our designers are not giving us what we need, we call them out on the carpet, too. We’ve been able to hire and train people who have a good attitude and an aptitude for learning, and really want to deliver a good product.”
Story and photos by Michael Uva, Senior Communications Specialist at the Northeast Ohio Regional Sewer District. This is the cover story of our 2019 Clean Water Works technical magazine. For print copies of the complete journal, contact us.