The bioretention gardens developed by the University of Michigan hold the promise of being a cost effective solution to both Detroit’s issues with blight and Toledo’s problems with water quality.
While Detroit’s struggles with blight are well-known, Toledo residents periodically face the challenge of dealing with water contaminated with toxins created by blue green algae blooms in Lake Erie. Engineers, environmental scientists, and landscape architects at University of Michigan’s Water Center at the Graham Sustainability Institute recently receive grant funds totaling $3 million to determine the cause of the Lake Erie algae blooms. In addition, the funding will also support testing the effectiveness of a green infrastructure initiative in the west side Detroit neighborhood of Cody Rouge to manage both storm water and combined sewer overflows by using bioretention gardens. How are the issues of blight and water quality connected? What does the University of Michigan team hope to accomplish with their green infrastructure initiative?
During the summer of 2014, Toledo residents who wanted a glass of water discovered that instead of receiving clean clear water from their taps, a greenish murky soup flowed from their faucets. Tests of Toledo’s water supply found microcystin toxin contamination. Some of the health dangers posed by microcystin ingestion include:
- Nervous system damage leading to seizures
- Liver damage causing inflammation and internal bleeding as well as liver failure
- Skin damage including blisters and rashes
- Respiratory system damage and pneumonia
- Kidney damage
- Potential tumor growth
The source of cyanotoxins is cyanobacteria, commonly called blue green algae, which often blooms when a body of water contains a high-level phosphorus. Traditionally, when water tests indicate the presence of phosphorous, they assume it comes from runoff from agriculture areas where farmers use fertilizers containing this element. In the case of Lake Erie’s algae blooms, initiatives to reduce phosphorus levels focus on addressing agrarian runoff into the Maumee River, which flows into Lake Erie. Unfortunately, these efforts have not successfully reduced the annual blooms of blue green algae.
The reason the efforts to eliminate phosphorus contamination have not succeeded is that they overlook another source of phosphorus pollution – the Detroit River, which contributes 80 percent of the water contained in Lake Erie. According to a 2014 report published by the International Joint Commission, approximately 40 to 50 percent of the phosphorus present in the Lake Erie Basin comes from Detroit River. With the focus on agricultural runoff, environmental scientists overlooked urban runoff and combined sewer overflows as contributing to the phosphorus load.
A portion of the grant funds received by University of Michigan will be used to monitor the level of phosphorus entering Lake Erie at the mouth of the Detroit River. In addition, the research team will also develop computer models to simulate the hydrology and the water quality in the Detroit River. These models will allow scientists to pinpoint the source of phosphorus and the amount that flows into the Lake Erie basin. Given limited infrastructure funding, how can public officials improve the processes used to treat storm and water without the need for raising a significant amount of capital?
Bioretention Gardens: A Cost Effective Green Solution for Addressing Blight and Storm Water Issues
The second grant-funded project underway by University of Michigan engineers and research scientists is building bioretention gardens on sites where the City of Detroit has demolished homes. As discussed in the video below, the soil in the Detroit area consists of clay, which is not very permeable to water, thus rainwater floods into the storm water system. This excess water combines with wastewater in the City’s sewer system and then overloads the water treatment plan, which then discharges contaminated water into the Detroit River.
Like many Detroit neighborhoods, Cody Rouge, located in the west side of the city, suffered from both the depopulation of the area as employment opportunities in the automotive industry disappeared and the effects of the housing crisis that left 22 percent of the home neighborhood vacant. As the City took possession the uninhibited boarded up homes, officials started to undertake the task of demolishing the homes.
Often vacant lots in Detroit become dumping grounds for trash, meaning just demolishing abandoned homes is not enough to address blight in urban areas. Engineers from the University of Michigan devised a possible solution to both the City’s challenges with blight and storm water management – build bioretention gardens on the sites of demolished homes.
The Design and Function of Bioretention Gardens
As explained in the video, when the City demolishes a home, often the basement remains. Instead of just filling this hole with soil, the University of Michigan engineers proposed filling it with gravel and gardening soil. Prior to laying the gravel, the construction crew fits the basin with a drainage pipe that connects with the storm water system. Once completed, the next step involves planting vegetation to create a garden.
The concept underlying this design is that the plants absorb some of the water through their roots. In addition, the roots, along with the soil and gravel act as natural filtration systems. Since rainwater is better able to permeate the garden soil, the bioretention gardens reduce the amount of surface runoff and the vegetation uses any phosphorus present in the water since it is a nutrient. By using these natural processes, this green infrastructure decreases the quantity of water that enters the storm water system as well as the amount of phosphorus the water contains.
The University of Michigan Water Center partners in the Cody Rouge bioretention gardens project include the Detroit Water and Sewage Department, the Detroit Land Bank Authority, the Cody Rouge Action Alliance, and the Warrendale Neighborhood Association. The University of Michigan researchers will use their grant funds to determine the efficacy of the bioretention gardens in reducing the amount of storm water flowing into the sewer system and lowering he phosphorus level. In addition, the team plans to use funds to educate residents of the neighborhoods about the purpose of the gardens and to determine the how well people accept this form of green infrastructure. Furthermore, the engineers and environmental scientists also intend to develop additional green infrastructure especially for the Cody Rouge neighborhood.
The Benefits of Using Bioretention Gardens and Other Forms of Green Infrastructure
It is no secret that local and state governments struggle to find money in their budgets constructing new infrastructure as well as improving and maintaining existing systems. Bioretention gardens not only cost less capital to install than new storm water management systems, they are also less expensive to maintain. Since less water enters water treatment facilities, the systems are under less stress, which reduces the cost of repairs. In addition, since the plant materials absorb phosphorus from the storm water, municipal water authorities may need to spend less money on filtration systems. For residents who live in neighborhoods where the bioretention gardens are installed, they enjoy the eradication of blight and the natural beauty of flowers, plant, and shrubs in the new green space. In addition, property values are likely to increase with the removal of blight, which benefits both local governments and homeowners. In the case of the Cody Rouge green infrastructure project, the residents of Toledo, who live 60 miles away from the bioretention gardens, benefit from the reduced risk of water cutoffs due to myocystin toxins in their tap water.
What are your thoughts about using bioretention gardens? Do you think they can be scaled up for more widespread usage?