The entirety of our world has been and is still dependent upon one natural resource, water. As a part of civilization's development, water was and will always remain a key factor in how we live our lives. Water enables us to carry out every day processes such as washing, irrigation, and generating hydroelectric power supplies. Given this, one would assume society would want to keep the water we have as clean as possible, allowing us to have a constant supply of high quality water for use. Although the latter is true, the current systems our society has set in place are not yielding feasible results, thus providing us with a lack of quality and quantity and setting a higher water demand.
Today, our storm water management facilities are lacking in the production and consistency of clean water and are in need of assistance from the public. My proposal is to help these facilities by introducing green roofs into our current systems and neighborhoods to alleviate the stress and strain placed on their systems. Carrying out this plan will not only alleviate the stress on the systems currently in place, but also give us a chance to step away from urbanization and recall the prowess of nature's abilities and processes in more ways than one.
Before making any changes or implementations into our current situation, there is an absolute need to evaluate the current problem and the severity of it. As it stands, our society is plagued by contamination by infiltration. Contamination by infiltration means that for the amount of rainfall we receive, our water supply is contaminated by that amount as the rain water "runs off" of the impervious pavements such as sidewalks, roads, and buildings. This run off, also referred to as storm water runoff, flows right down into our storm drains and makes its journey to places such as ALCOSAN (Allegheny County Sanitary Authority) and PWSA (Pittsburgh Water and Sewer Authority) where it is then cleaned and purified. That system is very suitable when it comes to regulatory amounts of rainfall, but when the rainfall becomes too massive, these systems fail and the runoff overflows directly into our rivers. This is possible due to the combined sewer systems underneath our very feet. Combined sewer systems work as follows: as the amount of rainfall increases, more runoff overflows into that system and eventually overcomes the pipe capacity, pushing runoff into our rivers. The problem is that it not only pushes the run off into the rivers, but also any raw sewage that sits in those pipes.
As it stands, approximately eight hundred cities across the United States have these combined sewer systems which go through the same processes as previously explained [1]. Frequent overflows on these systems continuously damage the water quality by introducing excessive amounts of pollutants picked up from the streets and sidewalks, causing human health concerns as well as aquatic life concerns [2].
In the summer of 2012, one possible solution to this problem surfaced. The proposal was from ALCOSAN (Allegheny County Sanitary Authority), and it was titled the Wet Weather Plan (WWP). The WWP is a plan that maps out how ALCOSAN wants to mitigate combined sewer overflows and lays the blueprint of how this region will address federal regulations of sewer overflows [3]. This plan includes ideas to implement new sewer overflow control technologies that are categorized into four different criteria based on their abilities. These criteria are REMOVEflow, MOVEflow, HOLDflow, and TREATflow. Within each of these are possibilities of construction of new sewer lines, storage tanks, and facilities, costing the city and even us the residents more money [3]. Implementation of more sewer lines, storage tanks, and facilities may be just what we need, but at a high cost and a higher risk. There is a possibility that such facilities and sewer lines could break or shut down, leaving us again with a cost to fix them. The net total cost of this proposed plan is an estimated 2.8 billion dollars, and would result in a ten to twelve percent annual rate increase for all customers [3]. Although the WWP has good ideas, the reality is that the costs to implement this plan is just too gargantuan, which leaves society in need of another proposal.
An innovative solution has been spotted in various parts of the United States and is beginning to see some practical application in neighborhoods and urban business districts; that solution is green infrastructure.
There are a myriad of green infrastructures and technologies in existence, but the main focus of this paper will be the use, the practicality, and the benefits of the green roof. Before diving into the use, practicality, and benefits of this innovation, there is one element that must be explored. The concept behind all green infrastructure is the concept of resiliency. Mr. Richard Dolesh defines resiliency as, "A measure of how well natural systems function over a wide variety of conditions and challenges" [4]. Basically, the green technology implemented must be able to withstand and adapt to its sometimes unpredictable surroundings. Another thing to understand is that a city's or region’s ability to survive increases in climate change and costs directly depends upon the resiliency of the implemented systems [4]. Implementing resilient green infrastructure such as a green roof allows us, the residents of the region, to reap multiple benefits such as lower taxes and lower energy costs. Green infrastructure works because not only does it provide us with a new way of handling our storm water problems, but it also effectively produces economic, environmental, and social benefits, thus establishing a triple bottom line [4].
Taking this triple bottom line into consideration, the use of green roofs in what are typically grey infrastructure regions immensely benefits these regions. Economically, implementing green roofs creates a demand for and produces more jobs such as those previously mentioned and creates higher tax bases, which in turn boost the economy [4]. According to the General Services Administration, employment from the use of green roofs in the United States rose 80% from 2004 to 2005 [5]. Tangentially, a study found that green roof investment over a year had the potential to create 600 to 1800 jobs per year (See FIGURE 1).
| SCENARIO TYPE | JOBS CREATED PER YEAR (AVERAGE) | INVESTMENT (IN MILLIONS) |
| Pessimistic | 590 | $299.9 |
| Conservative | 1179 | $599.8 |
| Aggressive | 1769 | $899.6 |
Along with that, successful implementation makes communities more attractive to businesses, which increase the revenue of that community, paving more ways to economic growth [4]. Pertaining to the real estate side of the economic benefit, the implementation of green roofs is equally pertinent. For example, Oregon saved 300 million dollars' worth of grey infrastructure costs just by implementing green roofs [6]. In addition to that, Portland implemented a program in 2006 that gave citizens a chance to become responsible for their storm water runoff. By incentivizing green roofs, utility ratepayers receive discounts based on how safely they control, retain, and dispose of storm water runoff [7]. Another example comes from Toronto Canada, where "[their] Eco-Roof Incentive Program offers commercial, industrial, and institutional buildings $50 per square meter of green roof, with a maximum grant of $ 100,000, if vegetation covers at least fifty percent of the available surface area" [7]. Green practices such as the green roof reduce the amounts of storm water pollutants entering our current treatment facilities, thus directly impacting and cutting the amount spent on treating such waters [6]. Cutting costs such as the previous and time consumption through building grey infrastructure such as office buildings, we achieve that same resiliency that the green technologies have, thus maintaining our region for the upcoming generations.
In terms of underground water issues and storm water management, incorporating the green roof into established urban environments will effectively mitigate storm surges, restore natural rates of water infiltration and aquifer recharge. In fact, many authors indicate that storm water management is the most important environmental benefit of the green roof [8]. The studies of DeNardo et al and VanWoert et al prove this, as they show that green roofs could mitigate between 60% and 100% of storm water runoff, thus mitigating contamination by infiltration [9]. Following that, other research by Mickovski et al. shows that the runoff volume is dependent upon the type of vegetation used in the green roof construction (See FIGURE 2).
FIGURE 2 [10]
Experimental comparison of surface runoff volume in different green roofs for different rainfall duration
Looking deeper into this, we can extrapolate further data. From the research of Kosareo and Ries, "Compared to traditional roofs, intensive green roofs reduce runoff concentrations of lead by a factor of 3, zinc by a factor of 1.5, cadmium by a factor of 2.5, and copper by a factor of 3" [11]. Overall, the use of the green roof in society today would provide environmental benefits that could sustain the quality of our current water supply to a certain degree.
Besides the storm water runoff benefits, there are other environmental benefits that are of pertinent importance. For example, one benefit is enhanced air quality. According to Berardi et al, "Intensive green roofs have often been considered able to reduce air pollution. In fact, growing plants on rooftops partially substitutes the vegetation demolished during construction" [8]. Similarly, the studies of Currie and Bass prove this theory to be true. In Chicago and Detroit, they modeled the effectiveness of reducing air pollution by way of an urban forest effect model, and revealed that 109 green roofs would remove 7.87 metric tons of air pollution per year [12]. Some of the other benefits include: restoration of some of nature’s natural processes and improvements to ecosystem services, profound effects to the water cycle [6], moderation of weather and climates, and lower CSO (greenhouse gases) emissions [1].
However, there are some factors that one must consider when deciding to use the green roof. For example, studies show that concentrations of phosphate and nitrate can be high [13]. Berardi et al tells us, "Research done at Worcester Polytechnic Institute (MA, USA) has investigated the quality of water runoff. Comparisons of grab samples of storm water from a green and a non-green roof within the first few seasons following installation confirmed that phosphorus was leaching into the runoff of the green roof" [8]. However, after the first few years of installation, it is assumed that this doesn’t continue after the vegetation has been established.
Another important limitation to consider is the building structure. Because green roofs are highly efficient in lowering indoor temperatures, whether the building is insulated or not plays a big role. In insulated buildings, the contribution of a green roof would not do much for the cooling of the building; but in a non-insulated building, the green roof would contribute more insulation [8].
Implementing green infrastructure into communities has a vast effect on the future stability of that community, let alone the entire area surrounding that community. Without the use of green roofs, our society will soon become one without a high quality of water. As it currently stands, we do not have enough quality water to go around. Our urbanization of every system is slowly but surely becoming a problem, and if we, the public, don’t do something soon, we will have to face the consequences. As an aspiring civil/environmental engineer, I do not want to see the world as I know it go to ruin because of human neglect. If we as a society are to survive, then it is time for us to help out those companies such as ALCOSAN and PWSA, by giving their systems a break and becoming responsible for our water as well. We all live on this planet, therefore it shouldn’t have to come down to a group of people to take care of us. It is time for us to step up and take action against storm water runoff.
I'd like to first thank my mother and family for their continual support in all of my academic endeavors. I'd also like to thank my peers and all of the upperclassmen who motivate me to work hard every day, especially my group member Ashley Dacosta. Thanks to the Carnegie Museum of Natural History, specifically the Energy Net Program, for getting me interested in green architecture and the environment. And finally, thanks to Dr. Budny for creating this project, as it truly helped me explore an area I have been interested in for a while.