By Emily Poynter Jenkins, PhD, PE, CFM
A 33-inch sanitary interceptor pipe lay exposed in the middle of the Unnamed Tributary to the Saline Branch. Rising water from a storm carries a large log towards the exposed pipe. The log rams into the pipe; the pipe bends but does not break – yet.
Had the pipe broken, thousands of gallons per minute of raw sewage would have spilled into the tributary; thousands of gallons per minute of stream and storm water would have entered the pipe, flooding the wastewater treatment plant and causing immediate sewage back-ups at the homes connected to the pipe.
This scenario is occurring all over the United States as aging pipe infrastructure crosses streams that were once small ditches, but are now large, flashy, urban streams. The pipe infrastructure is deteriorating due to having been installed 50 to 100 years ago, while the streams they cross have increased in size and strength. The combination of these two factors can be a hazard to public health and to the environment.
In 2017, the American Society of Civil Engineers (ASCE) gave a report card on US infrastructure. We, as a country, received a D for Drinking Water Infrastructure and a D+ for Wastewater Infrastructure, which means the infrastructure is in poor to fair condition and approaching the end of its service life. Condition and capacity are of serious concern with strong risk of failure.
So, the pipes carrying our drinking water and wastewater have a strong risk of failing and many of those pipes cross streams. Years ago, when most of the drinking water and wastewater pipes were installed, pipes crossed small ditches. However, as more areas were developed and more rainfall ran off into the ditches, they grew into large streams with serious erosive capabilities.
Broken pipes often cause adverse environmental impacts, in addition to harming and inconveniencing the community. Boil orders and sewage backups into basements can cause damage and frustrate homeowners. Emergency fixes to the pipe, the stream, and the water/wastewater plant can be expensive while also leaving the public with a negative impression.
Performing stream restorations at pipe crossings protects aging infrastructure and also provides communities with urban green space and has numerous ecological benefits. A stream restoration is the manipulation of the physical, chemical, and biological characteristics of a site with the goal of returning natural/historic functions to a former or degraded aquatic resource. Stream restorations stabilize streambeds and banks to prevent scouring of pipes and improve the basic functions and ecology of stream systems.
In addition, people are drawn to natural spaces, particularly when they are easily accessible in urban areas. Restoring sections of stream in urban settings can provide personal wellness opportunities to the community. What once was a liability can become an asset for the community and the environment.
Water is powerful. Water can cut into banks, undercut pipes, and erode pipe and bridge footings. I have seen a 33-inch sanitary interceptor that was once buried under a stream completely exposed with the stream flowing under it. Another stream cut into its bank until a large exposed vertical streambank was 20 feet away from a home.
A stream restoration not only redirects the flow of water away from the bank but also from infrastructure. We can direct the flow of water into the center of the stream using large boulders, logs, or tree root wads placed in the streambed. The boulders or logs are placed to create structures that force water to slow down near the bank, then speed up as it cascades over the boulder into a center pool in the middle of the stream.
We can also spread the water out onto the floodplain to slow down the water and decrease the force it has on the streambanks. When streamflow is confined to a narrow, deep channel, the flow increases and the water can erode banks and infrastructure easily. When the streamflow can spread out over a floodplain, the flow is slower and banks are more protected.
In Champaign, Illinois, an electrical box was located on the outside bend of the Copper Slough. The stream had eroded the bank away, leaving the electrical box only a few feet away from a vertical, unstable streambank. Farnsworth Group, a full-service architectural and engineering firm, protected the electrical box by restoring the stream. Boulder structures were used to direct water into the center of the stream, away from the bank with the electrical box. A small ledge, or bench, was graded into the bank to allow water to spread out and slow down during rain events. The bend in the stream channel was adjusted to be a longer, more gradual curve, adding stability in the stream. Native vegetation was planted on the banks to protect against bank erosion and to provide an ecological habitat for pollinators and small wildlife.
Because of this stream restoration, the electrical box is protected, the stream is stable, ecology in the area is flourishing, and the homeowners can reap the benefits associated with being near nature.
Increase Personal Wellness
While at graduate school in Maryland, I lived in a suburb of Washington D.C. My research afforded me an opportunity to get outside, but my day-to-day routine kept me in very urban environments. I found myself making time to hike and camp, referring to it as my “woods fix.” After my “woods fix,” I felt centered, calm, and rejuvenated.
Several years later I realized that it’s not just me who needs a “woods fix.” Researchers have found that being in nature or even viewing scenes of nature reduces anger, fear, and stress. Forest bathing, a common practice in Japan, consists of simply being in the forest and has become a healing and preventive healthcare practice in Japanese medicine.
Blue Space, a specific subset of “woods fix,” is the term given to the impact of water ¬– sea, river, lakes, and even urban water features – on health and wellbeing. The sight and sound of water can relax us by lowering cortisol (stress hormone) and raising serotonin (the “happy chemical” our nerve cells produce). Areas of water in or near nature are particularly beneficial to human health and we tend to seek them out when we can (think beach and lake vacations).
People enjoy being near nature – it improves their mood and wellbeing. Stream restorations at pipe crossing locations create an opportunity for Blue Space and nature accessibility for the community. If a stream corridor is owned by the City or Park District, a pipe crossing a stream can become a park amenity by adding a pedestrian bridge over the stream, creating a walking path near the stream, incorporating waterfalls or other water features, or building a playground or pavilion adjacent to the stream.
The City of Champaign, Illinois took advantage of the Boneyard Creek restoration project in a similar fashion. Though the main objective of the project is to provide flood storage, the restoration provides a multi-use trail along-side the channel and flood storage basin, called Second Street Basin. On any given day, you can walk past the Second Street Basin and see kids playing in the waterfall feature, runners jogging on the trails crisscrossing the Basin, and people bird-watching, picnicking or just napping on the benches along the creek.
Provide Ecological Benefits
Stream restorations are an ecologically friendly way of approaching stream instabilities to protect infrastructure. Many of the features that help create a stable stream and protect infrastructure, like access to a floodplain and boulder structures, also provide benefits to ecology. When streams flood onto their floodplains, food sources found on floodplains are washed into the channel. Organic matter like leaves, woody debris, and vegetation are introduced into the stream ecosystem. Aquatic invertebrates, like insect larvae, snails, and crawdads, consume the organic matter; fish consume invertebrates. To create and preserve a healthy circle of life in the stream, you need a constant supply of organic material, which is readily available on the floodplain.
Stream structures designed to protect the bed and banks of streams, as well as the infrastructure on the bed and banks, also provide ecological benefits to the stream system. Structures create diversity in channel flow. Slower water upstream of the structure and immediately behind (downstream) of a boulder are refuges for smaller fish. The fast-moving riffles over a structure provide dissolved oxygen to the water. Fast-moving water also washes away fine sediment particles from the gravel bottom of the channel, which is necessary for ideal fish spawning locations.
Vegetation along the banks of the stream provides shade to the stream, which regulates the temperature of the water. Vegetation also provides habitat to pollinators like bees, butterflies, and dragonflies. Did you know that dragonflies can eat 30 to over 100 mosquitos every day? Small mammals and birds live and eat in streamside vegetation. A restored stream system can host a diverse bevy of species.
For example, one week after the Copper Slough bank restoration project in Champaign was complete, a blue heron was fishing off the boulder structure in the stream. Fish were enjoying the depth of the scour pool beneath the structure, and dragonflies, songbirds, and butterflies were bountiful in the native vegetation lining both sides of the stream.
Birders regularly come to the Boneyard Creek Second Street Basin to watch the migratory birds take refuge in the restored in-stream basin. The Illinois Department of Natural Resources (IDNR) found a fish species called the Largescale Stoneroller in the Kickapoo Creek one year after the first phase of a stream restoration project was completed. The Largescale Stoneroller is classified as a species in greatest need of conservation by IDNR.
Increase Property Values
Not surprisingly, the biggest argument against stream restorations is the cost in comparison to a less-natural approach, like using riprap or concrete to stabilize infrastructure. Certainly, stream restorations are expensive, but they are also sustainable.
Stream restorations have long-lasting, positive effects. With a one-time restoration project, infrastructure is protected for the foreseeable future because the flow is manipulated away from sensitive areas. Conversely, riprap and concrete in the stream simply armor the sensitive areas. When water hits riprap or concrete, it is moving fast and creates turbulence near the bank. That turbulence can erode adjacent unprotected areas of the bank, causing increased erosion around and downstream of the hard-armored materials.
Additionally, research shows that property values increase near water features. Home lots adjacent to wet ponds in Champaign and Urbana, Illinois are worth an average of 21.9 percent more than non-adjacent lots in the same subdivision. A 2017 study by Nicholls and Crompton shows that “significant positive property price effects are associated with river, stream, and canal view and proximity.” Once a stream has been restored to protect infrastructure, adjacent property values will increase.
The most sustainable and multi-functional method to protect infrastructure at stream crossings is a restoration. Stream restorations create a stable stream that will provide long-lasting protection of the infrastructure. Restorations have the additional benefits of reestablishing the ecological function of a stream system and reconnecting people to nature, thereby improving their personal wellness. By changing our perspective, we can turn failing infrastructure into an opportunity to create an asset to the community and the environment while protecting the well-being of both.
And what about the 33-inch exposed sanitary interceptor pipe in the Unnamed Tributary to the Saline Branch? Farnsworth Group compared several options to protect the pipe and determined the most cost-effective solution was to restore the stream.
We adjusted the channel alignment to gently curve the stream away from the threatened manhole, constructed a small bench, or shelf, on the bank to give the stream space to flood, and constructed a series of structures with boulders to direct the flow of water into the center of the channel and away from the bank. We also slowed the water directly upstream of the pipe by creating a slow-moving pool, followed by a long, steep streambed where water cascades and tumbles over large rocks. The banks and floodplain are now planted with native vegetation.
The interceptor pipe is now carefully protected underneath the boulders of a stream structure. Deer, heron, turtles, and a plethora of fish have been spotted in the park setting, and raccoon tracks can be seen on the stream bank. The sound of running water muffles traffic noises nearby. I watch a dragonfly dart across the water and listen to the bees droning on the bank. The serenity of the stream relaxes and rejuvenates me as I head back to the office to start the next project.
Emily Poynter Jenkins, PhD, PE, CFM, is a project engineer for Farnsworth Group (www.f-w.com) who has been designing stable and sustainable stream restorations and bank stabilizations for more than 10 years. Examples shown in this article are designs of hers and the Farnsworth Group team. Her clients have included municipalities, utility companies, local developers/builders, and private property owners.