Going Big on Infrastructure

In the quest to eliminate overflows, KC Water invests billions in wastewater system improvements.

Going Big on Infrastructure

The primary goal of the Smart Sewer Program is to treat 77% of combined sewer overflows by 2035 and 85% by 2040. The utility has already spent about a billion dollars in the first 12 years of the project, and 51 more projects worth about $225 million in contracts will begin this year.

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KC Water is in the midst of orchestrating a roughly $2.3 billion, 30-year makeover of the sewer infrastructure in Kansas City, Missouri — a massive project that includes a new biosolids processing facility that will be the first of its kind in the Midwest.

The project, called the Smart Sewer Program, is aimed at significantly reducing chronic sewer overflows, primarily from the city’s 1,060 miles of combined sanitary and storm sewer lines, some of which date back to the 1880s. Prior to 2010, the year the program kicked into gear, annual overflows from the combined sewers — primarily located in the oldest parts of the city’s downtown district — typically totaled 6.4 billion gallons at 90 outfalls into local waterways.

When completed in 2040, the program will address mandates specified in a consent decree issued by the United States Environmental Protection Agency in 2010. The primary goal for the system as defined in the decree: Capture or treat 77% of combined sewer overflows by 2035 and 85% by 2040.

The decree has been modified three times since 2010 — most recently in 2021 — to make the project more affordable for utility customers. The modifications also reflect the adoption of newer and better technologies and practices that have emerged since 2010, says Matt Bond, deputy director of the utility, which manages both water and sewer operations in the city.

“We’ve already spent about a billion dollars in the first 12 years of the Smart Sewer project,” Bond says. “Renegotiating the consent decree allowed us to address the undue burden on ratepayers — we had to make the project more affordable.”

The project is already the biggest investment in infrastructure ever made by the city, notes Brian Hess, head of the utility’s Smart Sewer Division. “We’re using a combination of different technologies and means to address the combined sewer overflows. Each of the city’s seven major combined sewer basins is different, so we’re trying to capture a certain percentage of stormwater in each one to minimize systemwide overflows and protect public health and the environment.”

The program essentially consists of nearly 100 different projects of all sizes that embrace a variety of tactics and methods to reduce overflows, ranging from traditional “gray” capacity, storage and treatment improvements; pipe lining; manhole rehab work; and nature-based green infrastructure solutions. It also employs flow sensors that control gates inside pipes that can redirect sewage flow at multiple locations, Hess says.

Through 2021, about 234 miles of sewers have been rehabbed and 40 of the 98 projects have been completed through 2021. In 2022, 51 more projects worth about $225 million in contracts will begin.

New treatment facility

A primary component of the project is a $131 million rebuild of the solids-processing components at the Blue River Wastewater Treatment Plant, which is the largest of the city’s six wastewater treatment plants and handles almost all of the city’s wastewater solids. The new facility will be known as the Blue River Biosolids Facility.

When it goes online in mid-2024, the facility will be the first one in the Midwest and one of only a handful nationwide to use a process known as thermal hydrolysis to treat wastewater solids. It will be capable of treating 94 dry tons of solids per day.

Built in the 1960s and upgraded in 1987, the old facility incinerated about half of the solid waste it took in; the ashes then were landfilled. The other half of the waste was treated with anaerobic digesters, then land-applied at a city-owned site, Bond explains.

But repeated problems with the aging incinerators, which would have cost about $60 million to fix, coupled with increasingly stringent air-emissions requirements and unreliable landfilling options, prompted utility officials to seek a more cost-effective and eco-friendly solution.

“We needed a more stable and reliable long-term solution,” Bond says.

To ensure the project is as sustainable as possible, planners followed Envision guidelines developed by the Zofnass Program for Sustainable Infrastructure at the Harvard University Graduate School of Design and the Institute for Sustainable Infrastructure. (The latter is a not-for-profit education and research organization founded by the American Public Works Association, the American Council of Engineering Cos. and the American Society of Civil Engineers.)

“Envision is like the LEED (Leadership in Energy and Environmental Design) guidelines for buildings, but designed for sewer and water infrastructure,” Bond says. “All of our projects use Envision as a framework for creating sustainable projects.”

Innovative process

Thermal hydrolysis uses a two-step process that essentially pressure cooks solids at a temperature of 329 degrees and makes them more amenable to anaerobic digestion.

The process produces two usable byproducts: biogas and a nitrogen-rich fertilizer. Both byproducts could be sold to create additional revenue for the utility, Bond points out.

Moreover, the utility will save money through reduced landfilling costs and other efficiency gains, as well as reduce greenhouse gas emissions from the facility produced by the incineration process.

“We’ll no longer have to purchase large amounts of natural gas (for the incinerators) and will be able to harvest energy from the thermal hydrolysis process,” he says. “We’re looking at using the biogas to co-generate electricity or deliver that clean gas to a natural gas pipeline.

“We do believe there’s a market for the fertilizer, too. But the main goal is to reliably take care of biosolids 24/7. After we establish an operational track record, we can decide if it’s worth creating a market for these Class A biosolids.”

The project requires complete demolition of the existing treatment building down to its foundation. When the old facility is offline, the existing anaerobic digestors will continue to treat some of the waste while the rest is treated on site through temporary dewatering and a lime stabilization process. That waste then will be land-applied at permitted sites.

The demolition now is complete and the project is about one-third finished.

“When completed, it will allow us to sustainably and reliably handle our biosolids essentially for perpetuity,” Bond says.

Green infrastructure

Wherever possible, the utility is embracing upstream green infrastructure to minimize sewer overflows. Examples of green infrastructure include bioswales, rain gardens, permeable pavers, bioretention cells and detention basins.

When completed, the Smart Sewer Program will integrate green infrastructure with structural solutions to manage stormwater coming from 480 “green” acres. (A green acre is 1 acre of an impervious surface — everything from rooftops to parking lots to streets — that drains to a green infrastructure site.)

Nearly two dozen green-infrastructure sites that manage stormwater from 302 green acres have already been completed.

These alternative measures are significantly more cost-effective and less disruptive than excavating streets to separate sewers in the oldest, most-developed part of the city. And in many cases, they enhance and beautify neighborhoods by adding green spaces and recreational amenities, Hess points out.

“Green infrastructure is a great tool for hitting those points where you’re trying to save money but still accomplish the goals in the consent decree,” he says.

Natural components

A good example of green infrastructure is located in the historic West Bottoms neighborhood in the city’s central industrial district. This project combined traditional “gray” solutions with cost-effective and eco-friendly stormwater-infiltration techniques.

“This project captures stormwater and then redirects it or allows it to infiltrate the ground,” Hess explains. “It keep stormwater from the combined sewer system so its capacity isn’t overwhelmed.”

This project employed a variety of solutions to collect and manage stormwater, including retention basins; a roughly 5-acre bioswale landscaped with native plants, shrubs and trees; two underground cisterns (18,050 gallons total capacity) that capture stormwater from an interstate highway overpass; a dry-well infiltration system; and a plaza made from permeable paving bricks laid on a deep course of gravel that stores excess rainwater until it drains into the ground or escapes via under-drain pipes, says Srini Vallabhaneni, smart sewer officer of the utility’s Smart Sewer and Stormwater Divisions.

Completed in 2020, this $8.5 million project — which won a national award for best environmental project from the American Public Works Association in 2021 — is designed to reduce combined sewer overflows in the area by more than 20%, Hess says.

In addition, the project helped create new public spaces, including pedestrian walkways and a covered outdoor space for festivals and other events. Another popular component is a boardwalk through the swale and enhanced pedestrian and bike paths and rest areas. By making the space more attractive, city officials hope to spur more development in the area.

Overall, the project’s native plants included 338 trees, 1,104 shrubs, 316 grasses, 7,063 wildflowers and three acres of native seedings, Vallabhaneni says.

Alternative methods

At another problem site located south of downtown, the utility used diversion structures and consolidated sewers to handle overflows. Initial plans here called for installing 9,400 feet of 30- and 36-inch-diameter sewer line to carry combined sewer flows to an interceptor line that connects to the Blue River Wastewater Treatment Plant.

The goal: Stop an annual average of 3.2 million gallons of combined sewer overflows into a local stream that eventually flows into the Missouri River.

But such a project would’ve been extremely disruptive. So the utility instead decided to build the more sustainable, $10.6 million Trolley Trail Storage Basin, an open, 3 million-gallon earthen detention structure located in a largely unused portion of South Oak Park.

Completed in June 2021, this basin — about the size of a football field — now captures combined sewer overflows during heavy rainfalls, then gradually releases the stored overflow back into the combined sewer system within 24 hours after a storm ends, Hess says.

In addition, the utility worked with KC Parks to enhance and expand an existing walking trail around the nearly 20-acre park. This included widening and resurfacing the walking trail, building two pedestrian bridges and creating a new section of trail that connects to the existing trail.

To determine when to release the stored flows, utility officials rely on three sensors in the Trolley Trail basin that monitor sewer flow levels and close gate structures accordingly: one upstream, one downstream and one at the storage basin.

During heavy rains, the sensors automatically instruct the gates to adjust and direct overflow sewage to the basin. When the flow level in the combined sewers subsides sufficiently, another gate opens to initiate a controlled release from the basin back into the sewer system, Hess says.

Sensors are installed at around 250 locations systemwide.

Overflow reductions

While the completion of the Smart Sewer project is still 18 years away, it’s already having an impact. Typical annual combined sewer overflows have now decreased to 4.48 billion gallons from 6.38, nearly a 30% decrease, Vallabhaneni says.

“Our Smart Sewer Program remains firmly committed to fulfilling best-practice outcomes and consent-decree mandates through adaptive management, learning as we go and adjusting investments for best results,” he says. “Projects of all sizes and scope are in place or continue to take shape.

“More than 10 years into the initiative, Smart Sewer outcomes are right for public health and safety while safeguarding wastewater sewer system infrastructure for future generations.” 


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