When You Need to Make It Flow Uphill

Editor’s note: This article appeared in the June 2014 issue of Water Efficiency.

When deploying sustainable water networks, we can observe the watersheds they’ll inhabit to seize opportunities to serve both people, and the planet. In the 21st century, we’re getting used to scientific facts running circles around science fiction, yet water will always behave the same. Whether we use sophisticated electronic pumping systems, or simple devices like Archimedes’ Screw, it doesn’t lie, always flows downhill, dissolves a legendary portfolio of chemicals, and remains essential to every living thing on earth.

Observing the watershed in the planning and implementation can yield simpler, smarter infrastructure that’s a better “fit”—delivering more to customers with less effort, energy, wear, and with more savings that can be passed on to end users and ever-shrinking public budgets. Therefore, following the rules of watersheds can also be of great social benefit as well. With the complex ordinary water needs of human beings, and global ecological challenges that are already affecting us, smarter infrastructure that works with and contributes back to its watershed can help head off future “water wars” and lay the groundwork for an abundant, sustainable, even inspiring water future.

So, how exactly do we build infrastructure that fits its watershed like a glove for the benefit of all? Every watershed on earth is shaped by variables including local land contour, climate, geology, the presence and function of water bodies as “organs” to the watershed’s “organism,” and ecological and biological feedback loops. While all watersheds have these variables in common, the variables themselves can vary wildly and make watershed-centric solutions look very different from place to place. Add to that the wildcard of human habitation and existing infrastructure, and watershed-sensitive design can look even more divergent from setting to setting. Infrastructure destructively laid could portend a new wave of ecological ruin if downtowns and suburbs are left to deal with 40-foot trenches, miles of knocked out trees, armies of trucks, exhausted treasuries, and catastrophic inconvenience for millions. For better or worse, the already-laid work of human hands now impacts nearly every habitable watershed on earth.

While a layman with deep ecological leanings and moderate water knowledge might innocently argue for letting gravity rather than electricity do all the work of moving water, the reality is not nearly so simple. Sometimes the best solution on our well-settled planet is indeed to let gravity do the work and sometimes it is to make water flow uphill, travel in circuits, or move through complex switching stations. It’s important to consider our whole portfolio of tools—earthy, high-tech, and sometimes between—and to knit them together in complex modular configurations as unique as the watersheds where we’re employing them.

The Deep Tunnel Project
The strategies put in place by the Milwaukee Metropolitan Sanitation District (MMSD), which just completed its Deep Tunnel Pump Station Upgrade Project in 2013, typify this approach. MMSD is a regional governmental agency serving 1.1 million customers in southeast Wisconsin. The service area comprises about 380 square miles over six watersheds, includes 28 municipalities, and 300 miles of interceptor sewers. Each municipality in the region maintains a collection system and sends its wastewater to the MMSD system, about 5% of which is a combined sewage and stormwater system, and about 95% of which is a separated system. The water flows through an almost exclusively gravity-fed infrastructure to end up at one of two reclamation facilities—the Jones Island facility serving the combined area, or the South Shore facility mostly serving the separated areas. Each plant can process about 330 million gallons per day (MGD) and dry-weather flow into either is about 50-60 MGD.

work squeezed into a deep-winter 42-day service outage each year from 2011 to 2013 when flows would be lowest. Project leads described the choreography itself as an innovation.

Rick Niederstadt, MMSD’s Construction Support Manager and the resident engineer on the project says, “We brought the pumps up from 330 feet below grade, got them completely overhauled, lowered back down, reinstalled, tested, and running again within a 42-day window. The timing and execution of the project itself was innovative, and I believe the people who did the overhauls would say the same.”

Pump station upgrades included increasing power from 4,000-5,500 horsepower, adding cone valves and replacing the existing outdated speed control system with new variable frequency drives to control the flows and improvements to the HVAC systems on the building where the system is housed. The changes increase not only the power but also the precision with which the water can be moved.

“Before the upgrade,” says Mike Martin, Technical Services Director at MMSD, “with the pump station 330 feet underground, once you pumped up and stopped, you ended up with a 330-foot column of water that wanted to come back down and run the pump backwards. That’s not good on a pump. Previously there was only a constriction in the pipe to limit the flow. During the upgrade we installed some new cone valves to stop that as well as the variable frequency drives to control the flow. Now the water just sits there.”

“With that high of a head of water, check valves are problematic, adds Niederstadt. “The new installation has mechanical and electrical devices—cone valves and variable frequency drives that are doing the same thing to eliminate backspin while not restricting the discharge flow.”

The upgrade also included a new ability to closely monitor pump vibrations. With 42-inch diameter suction and discharge pumps moving millions of gallons at 5,500 horsepower, there’s not a lot of room for error. The previous pumps frequently tripped out on vibrations, so now systems have been installed to closely monitor all vibrations.

Considering the complexity of the project, the project leads are happy that it’s been performing as planned, meeting expectations and further reducing overflows to Lake Michigan. “We were able to increase pumping capacity, reduce overflows, and reduce vibration during operation—our upgrades have given us all kinds of information to monitor and track now over time. That will allow us to see problems before they become big problems,” says Martin. “With any project of this magnitude and criticality, you expect something that’s a challenge. This project went exceedingly well. We haven’t had those major challenges.”

The lead engineers expect the pumps to last at least 20-25 years and are not yet sure if they will require the same maintenance schedule as the old ones which needed moderate servicing about every three years. The oldest pump is now approaching its three-year mark and all of the pumps continue to be inspected and monitored. The project engineers are also confident that most maintenance can be done in place.

“There was no need for the first 20 years to remove a pump from below grade,” says Martin, “and we expect the same.”

There have been a few minor surprises resulting from the increased pump efficiency and capacity. Future plans call for pushing more flow through the South Shore facility, but MMSD is finding some previously undiscovered bottlenecks along the force main and leakage from head tanks that weren’t happening before because the old pumps never reached the current capacity. Engineering teams are going to work on the new issues.

As part of its wider watershed approach, MMSD is also working to reduce the flows that reach the Tunnel at all. While Tunnel

inflows contain the region’s human sewage they’re mostly water from storm drains and leakage. To ultimately eliminate overflows to Lake Michigan altogether, the District is spearheading green infrastructure programs. They’ve been running a popular greenways program for about 10 years, buying and preserving thousands of acres of river-adjacent upstream wetlands, riparian areas, and vacant farms. There’s a popular rain barrel program for homeowners, the District does native plantings, encourages downspout disconnection in the combined sewer areas, and encourages home-scale rain gardens. MMSD supports green street infrastructure such as bioswales and has funded pervious parking lots, green roofs, and leaky lateral repair projects. Since the initiatives are relatively new, it’s impossible to quantify the impact on Tunnel flows, but these will certainly help.

Improved Performance in Carter, MT
Innovative design can be just as critical for people-and-planet supporting infrastructures in rural areas and the issues just as complex. When a small Montana community with a tiny budget had to realize “big water system” efficiencies or lose its Missouri River lifeline, Grundfos, the Denmark-based global pump and pumping systems provider tapped its Engineered Systems (GES) group to help by integrating project engineering, intelligent controls, and vertical turbine and booster pumps as a comprehensive service offering.

Carter, MT, population 200, relies entirely on the nearby Missouri River for domestic and irrigation water. The town’s system, operated by the Carter-Chouteau County Water and Sewer District (CCCWSD), was built in 1976 and boasts 48 miles of distribution piping, four boosting stations, and a clean water transfer station. Despite upgrades in 2006 and 2007, EPA ordered the community to install filtration by March 2013, or risk disconnection. CCCWSD allocated $504,000 to complete the Carter Water Treatment Systems Improvement Project; construction began in December 2011 and completed in June 2012.

Maintaining system pressure was the top design challenge. Carter’s system draws water from the Missouri, filters it for potability, and pumps it several miles upstream to Carter’s distribution pumps. Elevation differences as well as seasonal variations in particle concentrations, manganese content, and temperature added to the challenge, and high-sediment loads in the river even threatened equipment. The design team was concerned that a system with compliant filtration wouldn’t maintain the pressure to reach the next pump house on its itinerary and the tiny budget and tight deadline demanded an accelerated, dead-of-winter construction schedule.

Several design innovations ultimately enabled Great West Engineering, the Montana-based firm which designed and oversaw the project, to bring the town’s system into EPA compliance under budget and ahead of schedule, bringing residents safer, cleaner water with less energy consumption and maintenance.

The first part of the solution developed with GES help was a cartridge filter system that eliminated the need for a $500,000 treatment facility while being easy and cheap to maintain. The second part, compensating for pressure drag resulting from filter fouling, was replacement of the one-pump river station with a Grundfos dual vertical turbine pump system with a custom control panel, a system that would provide the needed pressure while respecting the pressure limits of the filter housings. The filtered water now moved to the very remote distribution pump house via two vertical multi-stage centrifugal booster pumps through a Grundfos BoosterpaQ Hydro MPC. The design solution also eliminated the need for a traditional and costly wet well.The Grundfos control panel offers a standard remote monitoring feature that lets operators see pump status (on or off line), power consumption for each pump, and pressure differentials from one side of a filter unit to the other. Operators can easily see when a filter needs cleaning or replacement.”

On the downstream side, the vertical multistage booster pumps increased the pressures from 60 to 100 psi, up to 176 psi,” claims Matthew Mudd, P.E., project engineer with Great West Engineering.Another enhancement was the replacement of outdated and manually controlled chemical injection equipment with flow-paced pumps that allow fine-tuning of chemical injections. Now a flow meter tells the chlorine pump how much to allocate based on a particular flow volume. This upgrade improved monitoring and mixing and reduced the District’s chemical costs.

“We could have built the system using older style equipment, but the GES digital system with a combination of flow sensors and pressure sensors made it easier to engineer a smarter, more sophisticated system,” says Darin Arganbright, Director with the Carter Water District. “We’re now able to review actual system data and know our real-time performance,” he says, and according to Mudd, the project demonstrates that other small rural systems with limited technical expertise can also easily operate cartridge filtration equipment and enjoy efficiencies common to larger operations.

Pressure Sewer System Restores Lake Ariel
Water system engineers today are learning also that innovation is now making it possible to surgically insert water infrastructure so that the laying of pipe has little impact on the environment or on project budgets. Lake Ariel is a 3,800-home gated community in the Pocono Mountains of northeastern Pennsylvania that receives its water services from the Roamingwood Sewer and Water Authority. The community includes the lake, a small ski resort, a golf course, and hiking and bicycle trails, all built on a rock foundation. The area is home to a vast diversity of wildlife including deer and bears.In February 2010, Crane pumps & Systems was invited to a meeting hosted by the Roamingwood Sewer and Water Authority and their engineering consultant Cardno BCM to discuss a failing gravity-based sewer system with 26 duplex pumping stations.

“We were asked to come up with a plan and proposal for how we could minimize their problems,” says Nick Spondike, Large Project Manager for Crane Pumps & Systems. “Then the project was bid publicly. We were the second lowest bid, but because of what our design team was able to do, we were chosen.”

“The existing pumping stations were in terrible condition,” says Spondike. “There were several different brands, their electrical consumption was outrageous and they required continuous maintenance.”

While some of the stations were 18 years old, several were less than five. All were failing, running six to eight times per hour instead of the planned six to eight times per day, the newer stations compensating for the older ones. The stations were manifolded together and the result of failure was raw sewage in streets, yards and lake, creating an environmental disaster for the state. Each duplex station had carried an initial $150,000 to $200,000 investment and now required replacement.

With a proposal for a new pressure sewer system, “we were able to come up with a design to eliminate all 26 of the stations,” says Spondike. The Authority projected $80,000 in savings every year just in electrical costs.As a pioneer in the industry, small pressure sewer is an area of special expertise for Spondike. In a pressure sewer system, a Barnes EcoTRAN packaged system outfitted with a small grinder pump, such as the Barnes Omnigrind plus, is installed at each home site and might be thought of as a small appliance akin to an air conditioner or furnace. Hidden under a tank cover disguised as a landscape garden rock, the home’s pump grinds up biosolids to pass through much smaller pipes and drive sufficient head pressure to push wastewater to treatment even with elevation changes like the 210-foot seen at Lake Ariel.

One might at first think gravity-based systems are a more passive and hence eco-friendly choice than pressure sewers, but a closer look might tip the scales. Laying a traditional gravity-based system requires installing large pipes at exact grade and moving a lot of material. “When you install a gravity system,” Spondike explains, “the smallest pipe you use is eight-inch diameter and the biggest for a subdivision like Lake Ariel can be 24 or 30 inches.”

Work crews have to, exactingly, dig deep, wide trenches to lay the pipe and that can be incredibly disruptive to habitat. For communities built on rock in an ecologically sensitive zone, this groundwork is especially difficult, energy intensive, destructive, and expensive.

Additionally, when laying a gravity-based system, manholes must be placed at every pipe-turn. These become entry points for runoff, organic debris and garbage. That means more maintenance and treatment plants are left to process larger flow volumes that are more complex and less predictable. Treatment is energy intensive, more expensive, and requires additional treatment of inflowing groundwater.

Pressure sewer systems also involve much smaller pipe that can be installed by directionally boring. The Crane team used 1 1/2-inch flexible pipe as laterals from the individual homes out to the street and used 2, 3, and 4-inch pipe throughout the project. Directional boring involves steering a small drill underground using a kind of joystick. The drill can turn corners, weave snaking multi-mile underground routes with virtually no environmental impact, and with pressurized lines there’s no commitment to grade. This was a tremendous plus for the Roamingwood stakeholders.

“We eliminated the need for 40-foot wide cuts through the neighborhood and knocking down every tree,” says Spondike. “We can navigate that pipe to miss that 100-year-old tree; we can go downhill a little bit or uphill a little bit; we can direct that pipe to go anywhere we want.”

With pressure sewers, the only entry points into the system from home site to treatment facility are the homes themselves. With no secondary leakage, treatment gets simpler, demands less energy and money, and it’s easier to predict and use what’s coming out the other end. The design team also used modeling to show stakeholders at planning meetings exactly how their system was going to look and work with much greater accuracy than traditional designs could allow. Starting with an aerial photograph, the team laid the new sewers into a model of the project area.

“[At meetings] we could turn pumps on and off to show everybody what’s going to happen when you live at the end of this street,” explains Spondike. “What’s going to happen when six pumps come on, and what’s going to happen when 20 pumps come on? What’s going to come out of the treatment plant; how fast is it moving; and what’s it going to smell like?”

Pressure sewer systems can tie into any kind of grey or green treatment process that a gravity system can, from huge treatment facilities to naturalized treatment wetlands. Crane has collaborated with treatment designers for years and has great familiarity with integration into treatment systems gray and green.Perhaps the greatest lessons we can take from the exploration of these diverse solutions and water-planning scenarios is that one size does not always fit all. With old wisdom indexed online, futuristic water technology, and creative minds at our disposal, maybe the most powerful tool of all is openness, with which we can clearly see—or adapt or invent as the case may be—the right tool for the task. It is often said that change is the only lasting thing, and the adage is no less true of water infrastructure. Let us remain nimble as population change, climate change, legislative change, financial change, and cultural change swirl, altering the very assumptions within which our pipes are laid.