ENGR0011/0711 1020
Group R01
PITTSBURGH COMBINED SEWER OVERFLOW SOLUTIONS: ALCOSAN,
GREEN INFRASTRUCTURE, CODES OF ETHICS AND EDUCATION
Naomi Anderson (nea22@pitt.edu)
INTRODUCTION: THE PROBLEM WITH CSO
AND ALCOSAN’S PLAN
Pittsburgh, Pennsylvania is one of the rainiest cities in the
United States. While this climate stimulates a verdant
environment, it also creates a complicated situation with
sewage management. Like hundreds of other cities in the
country, Pittsburgh transports wastewater through a combined
sewer system. Developed in the 19th century, combined sewer
systems are sewers designed “to collect rainwater runoff,
domestic sewage, and industrial wastewater in the same pipe.”
[Combined Sewer Overflows] When the weather is dry, the
combined sewer system works efficiently to transport
wastewater from households to a sewage treatment plant,
“where it is treated and then discharged into a water body”
[Combined Sewer Overflows]. Unfortunately, combined sewer
systems were designed to release excess wastewater into
nearby water bodies during periods of heavy rain or snowmelt,
when the wastewater exceeds the storage capacity of the
treatment plants. This discharged water not only contains
storm water, but also contains untreated sewage, chemicals,
debris, and toxins. This is called combined sewage overflow
(CSO), and it poses serious threats to public health, aquatic
life, and water quality. An average Pittsburgh rainfall is a
quarter of an inch, and a CSO can occur with as little as one
tenth of an inch of rainfall—and there are over 150 rainy days
per year [1]. Clearly, CSO’s are a routine problem.
Pittsburgh’s sewer system is managed entirely by the
Allegheny County Sanitary Authority (Alcosan). In 2008,
Alcosan signed a “Consent Decree” with the Environmental
Protection Agency (EPA), the Pennsylvania Department of
Environmental Protection (DEP), and the Allegheny County
Health Department (ACHD). In this Consent Decree, Alcosan
promised to “achieve compliance with the Clean Water Act
during periods of wet weather” by meeting a series of
requirements for “for planning, design and construction,
operation and permitting” [Consent Decree]. Alcosan plans
on creating new sewage storage and transportation systems
using what many critics call “gray construction,” and has not
outlined any intention to incorporate “green infrastructure”
into their Wet Weather Plan [2]. If Alcosan incorporated green
infrastructure water management strategies, along with the
“Trickling Filter” water treatment system, its Wet Weather
Plan would be much more sustainable and cost-efficient. Two
years ago, I built water drainage systems on trails in one of
Vermont’s forests, and I learned how water management
helped preserve and sustain the forest. Ever since then, I was
extremely interested in sustainable water management from a
structural standpoint. It is important to me, as an engineer,
University of Pittsburgh, Swanson School of Engineering
that Alcosan incorporates green infrastructure and the trickling
filter water system into its WWP because as Pittsburgh’s
impact on its surrounding environment is growing, so is the
need for sustainable water management.
Ethics And Education
Additionally, this paper will address the relevance of the
National Society of Professional Engineers and American
Society of Civil Engineers’ codes of ethics, along with the
importance of a writing assignment like this for engineering
education.
TRADITIONAL STORM WATER
MANAGEMENT VS. GREEN
INFRASTRUCTURE
Traditional management of storm water involves transporting
runoff water to the water treatment facility as soon as possible.
Rainwater flows off of impervious surfaces such as roofs,
driveways, roads, and parking lots and enters gutters and
storm drains immediately, so flooding and pooling is avoided
[3]. Costly transportation, storage, and treatment centers are
built to offset the incredibly high amount of runoff water that
enters the sewage system, but there are no measures taken to
increase the pervious surface coverage [4].
Green
infrastructure addresses the source of the problem, rather than
working around it. Green infrastructure attempts to replicate
the natural hydrological processes that existed before the land
became developed and impervious materials replaced pervious
ones. When green infrastructure is employed, the amount of
impermeable surface is reduced, and more rainwater is
absorbed by the ground and used in earth-processes. This
significantly decreases the amount of runoff water that enters
the sewage system and needs to be treated [3]. If Alcosan
included green infrastructure as part of its Wet Weather Plan
(WWP), it would not have to spend as much money on
storage, conveyance and treatment, because there would be
less water entering the combined sewer system. There are
several viable green infrastructure options that could be
applied in Pittsburgh.
GREEN INFRASTRUCTURE:
BIORETENTION AND ITS BENEFITS
A large component of green infrastructure is rain gardens (also
known as bioretention cells). Bioretention is an urban storm
water “Best Management Practice” that not only reduces the
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amount of storm water runoff that enters the sewage system,
but filters pollutants on the spot. Bioretention cells are often
located in parking lot islands or within small areas of
residential land, and consist of
“shallow, landscaped
depressions” where surface runoff is directed [5].
Bioretention cells “generally consist of a porous media,
supporting a vegetative layer, with a topping layer of
hardwood mulch”. When water flows into the cell, it filters
through the porous media and is temporarily stored, which
reduces the site’s overall runoff rate and helps to maintain an
appropriate discharge rate. The porous media is composed of
natural soil and organic matter, which help remove pollutants
from the storm water runoff through “sedimentation, filtration,
sorption, ion exchange, and biological uptake.” [Davis]. In
addition to its use in storm water control, bioretention cells
can “also be used to reduce problems with on-site erosion and
high levels of flow energy” [LID Urban Design Tools].
Bioretention is an important way to increase the quality of
water, decrease the amount of storm water runoff, and should
definitely be included in Alcosan’s WWP.
GREEN INFRASTRUCTURE: PERMEABLE
PAVEMENT AND ITS BENEFITS
Another type of green infrastructure is permeable pavement.
Permeable pavement is asphalt or concrete that is mixed with
larger particles (and fewer fine particles) to create more air
space throughout the mixture and allow water to permeate
through the voids. Beneath the pavement is a “layer of fine
sediment that filters water”, and below that is “a bed of
uniform-grade stones that store the water as it infiltrates into
the ground” [Permeable Pavement].
As the water flows
through the pavement and infiltrates into the ground, many
harmful pollutants are captured “within the paver system and
the uppermost layers of underlying soil.” Permeably paved
areas are extremely effective at infiltrating storm water runoff
into the ground. For example, in the areas surrounding the
Charles River in Massachusetts, runoff was reduced by 100
percent during almost all of the storms. In general, permeably
paved pavements infiltrate seventy to eighty percent of annual
rainfall. [6] Permeable pavement is more expensive to install
and maintain than regular pavement, but it “can reduce the
overall project cost by eliminating the need for traditional
storm water infrastructure” (Permeable Pavement). Permeably
paved roads can be used in any “low traffic roadway”, which
constitutes approximately 69% of all of the roads in the United
States. Considering that roads generally need to be repaved
every 15 years, there are “plenty of opportunities for ‘green
street’ practices to be employed as they are paved or repaved”
(Garrison, Hobbs). Alcosan could easily employ this green
infrastructure strategy to its WWP, and it would save the city
of Pittsburgh millions of dollars in gray infrastructure.
GREEN INFRASTRUCTURE: GREEN ROOFS
AND VEGETATED SWALES AND THEIR
BENEFITS
“Green roofs” and vegetated swales are additional types of
green infrastructure that could be used in Alcosan’s WWP.
Green roofs are “elevated roof surfaces that are entirely
covered with a thin soil and vegetation layer” [Scholz-Barth].
Green roofs can help ease the excessive storm water runoff
problem because they “absorb and recycle” rainwater. On
average, extensive green roofs retain about seventy five
percent of the water that lands on them, stored in plants and
soil. The remaining water that is not retained is released
through a drainage outlet hours after the peak flow (when the
most water is flowing into the sewers). In addition to helping
ease storm water runoff, green roofs act as an efficient
insulating layer and slow temperature change within buildings
[4]. Vegetated swales are another effective way to limit the
amount of storm water runoff and generate water infiltration in
residential areas or large impermeable areas like parking lots.
They are “constructed, open-channel drainage ways used to
convey storm water runoff” [Vegetated Swales]. They are
often used as a sustainable alternative to traditional storm
sewers, and are able to store and infiltrate small water flows.
They are relatively cheap to build and maintain, and would
improve the sustainability of Alcosan’s Wet Weather Plan.
WHY I STILL CARE
Keeping all of the green infrastructure possibilities in mind, it
seems ridiculous to me that Alcosan would fail to incorporate
them into their WWP. The use of bioretention, permeable
pavements, green roofs, and vegetated swales are all
sustainable, engineered solutions to the issue of excess
combined sewage in Pittsburgh. We, as inhabitants of the
earth, cannot afford to choose unsustainable practices over
sustainable practices any longer. I feel strongly that Alcosan
should employ green infrastructure strategies instead of simply
building more storage containers because it is the more
sustainable choice.
I do recognize, however, that the
aforementioned green infrastructure isn’t the only strategy that
Alcosan must implement in order to completely solve the
problem—rather, it should implement the “trickling filter”
method of water treatment and storage in addition to the green
infrastructure, because it is the most sustainable gray
infrastructure option.
GOOD GRAY CONSTRUCTION:
TRICKLING FILTER WASTEWATER
MANAGEMENT SYSTEM AND ITS
BENEFITS
The “Trickling Filter” wastewater management system
combines secondary treatment of wastewater and storing of
overflow water. This system is a large cylindrical tank that
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has a platform that creates space between the bottom of the
tank and the surface of the platform. Biological media
(microbes that perform the water treatment) are spread out on
the surface of the platform, and the water interacts with the
media and moves to the next phase of treatment. However, in
the case of wastewater overflow, the space between the
bottom of the tank and the platform can serve as a storage
area. This way, additional storage areas need not be built.
Therefore, a great amount of resources, energy, and money is
saved with using this treatment system [7]. The alternative,
which is what Alcosan is proposing, is to build additional
storage units separate from their treatment units. Compared to
the trickling filter method, Alcosan’s plan is inefficient and
wasteful.
CONNECTION TO AMERICAN SOCIETY OF
CIVIL ENGINEERS CODE OF ETHICS
The American Society of Civil Engineers (ASCE) code of
ethics states “Engineers shall be scrupulously honest in their
control and spending of monies, and promote effective use of
resources through open, honest, and impartial service with
fidelity to the public, employers, associates, and clients.”
[Code of Ethics] This section of the code is particularly
applicable to the public interest of incorporation of green
infrastructure into Alcosan’s wet weather plan. When Alcosan
first released its WWP, the people of Pittsburgh disapproved
of the plan’s lack of green infrastructure and outrageous
cost—3.6 billion dollars. Since then, hundreds of concerned
citizens have been urging Alcosan to include green
infrastructure in its plan to not only help solve the sewage
problem, but to decrease the overall cost of the plan (more
inexpensive green infrastructure leads to less expensive gray
infrastructure) [8]. The responsibility to act in the interest of
the community of Pittsburgh not only lies in the hands of
Alcosan’s executives, but also in the hands of the civil
engineers working with Alcosan. Any engineer involved in
the planning of gray construction that knows anything about
the controversy surrounding the WWP—and this knowledge is
highly probable—is required, by the aforementioned section
of the ASCE code of ethics, to suggest implementation of
green infrastructure. If they fail to do so, they are not
promoting effective use of resources, being scrupulously
honest in their control of money, nor showing fidelity to the
public—therefore disobeying the code of ethics.
CONNECTION TO NATIONAL SOCIETY
OF PROFESSIONAL ENGINEERS CODE
OF ETHICS
The National Society of Professional Engineers (NSPE) code
of ethics mentions equally relevant regulations as the ASCE
does. A canon of the code states “Engineers shall at all times
strive to serve the public interest,” and more specifically,
“Engineers are encouraged to adhere to the principles of
sustainable development in order to protect the environment
for future generations.” [NSPE Code of Ethics for Engineers]
It is in the best interest of the public for Alcosan to utilize
green infrastructure in their plan because it would decrease the
overall cost to the people. Also, green infrastructure adheres
to principles of sustainable development. By only planning
gray infrastructure and excluding green infrastructure, the
engineers working with Alcosan are clearly violating both of
these parts of the code.
CODES OF ETHICS AND ME
As a future engineer, it is extremely important to me that my
colleagues and I practice ethical engineering by following all
codes of ethics. The rules stated by the codes of ethics of the
ASCE and the NSPE are specifically important to me because
they encapsulate several fundamental beliefs of mine. I believe
that every step engineers take should be in the direction of
improving the lives of our planet’s inhabitants, and that the
path these steps form should not have an impact on the lives of
future inhabitants. I find the part of ASCE’s code that
mentions honesty and fidelity to the public extremely
crucial—without this, efforts in engineering are not directed
towards the public; they are directed towards individuals’
wallets. The part of the NSPE’s code of ethics that refers to
the necessity of sustainable principles is important to me
because when I become an engineer, I want to make sure that
the practices I am carrying out have no impact on future
generations and can help society be more sustainable.
I realize that as much as the engineers working alongside
Alcosan can do to follow the various codes of ethics, most of
the responsibility to listen to the public’s opinion and create a
sustainable solution to the sewage problem lies in the hands of
Alcosan’s executives. For example, the engineer who invented
the “trickling filter” water treatment and storage system was
adhering to the codes of ethics by creating a cost effective,
sustainable solution that better respects the interests of the
people of Pittsburgh, and better respects the future of our
environment. It is up to Alcosan to implement this system.
ENGINEERING EDUCATION AND THIS
ASSIGNMENT
I see very much value in researching, forming a position
on, and writing about a current, controversial issue in
engineering. This assignment is a way for freshman engineers
to move beyond familiarity with entry-level courses, and
become invested in a specific field of engineering. It also
helps freshman students develop new skills in technical
writing, which will most likely be necessary in a future work
environment. Personally, writing this assignment showed me
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how interested I am in water management and sustainable
development. It is important that, early on, students are given
the opportunity to discover and explore what they are
interested in, especially in the field of sustainability. Many
agree that education in this area must be emphasized.
The 2002 and 2004 International Conferences on
Engineering Education in Sustainable Development
(a predominantly European event) emphasized that
Engineering education, especially higher education
for the training of decision-makers, researchers and
teachers, should be oriented towards sustainable
development and should foster environmentally
aware attitudes, skills and behavior patterns, as well
as a sense of ethical responsibility
[Desha,
Hargroves, Smith, Stasinopoulos].
specifically stated that engineers must serve the public interest
in addition to using sustainable practices.
In addition, universities with engineering programs should
continue to assign papers like these because they cause
students to become interested in specific fields of engineering
(like sustainability, for instance, which is a growing field that
needs more student interest), and help them feel connected to
what can otherwise seem like a broad, intimidating major.
REFERENCES
[1] "About the Wet Weather Issue." About the Wet
Weather Issue. 3 Rivers Wet Weather, n.d. (Online
Article).http://www.3riverswetweather.org/about-wetweather-issue
[2] Hopey, Don. "Alcosan Plan to Fix Overflowing Sewer
System Focuses on 'gray' Construction." Pittsburgh PostGazette. Pittsburgh Post-Gazette, 29 July 2012. (Online
Article).http://www.postgazette.com/stories/local/neighbo
rhoods-city/alcosan-plan-to-fix-overflowing-sewersystem-focuses-on-gray-construction-646696/
[3] Garrison, Noah, and Karen Hobbs. “Rooftops to
Rivers: Green Strategies for Controlling Stormwater and
Combined Sewer Overflows.” Issue brief. N.p.: National
Resources Defence Council, 2011. National Resource
Defence
Council.
(Online
Article).
http://www.nrdc.org/water/pollution/rooftopsii/
[4] Scholz-Barth, Katrin. "Green Roofs: Stormwater
Management From the Top Down." Environmental
Design & Construction (n.d.): n. pag. Edcmag.com. Jan.Feb.
2001.
(Online
Article).
http://www.greenroofs.com/pdfs/archives-katrin.pdf.
[5] “Bioretention (Rain Gardens)." EPA. United States
Environmental Projection Agency, 21 Aug. 2011. (Online
Article).http://cfpub.epa.gov/npdes/stormwater/menuofb
mps/index.cfm?action=factsheet_results
[6] "Permeable Pavement." Crwa.org. Charles River
Watershed Association, Sept. 2008. (Online Article).
http://www.crwa.org/projects/bmpfactsheets/crwa_perme
able_pavement.pdf
[7] Dunn, Scott. “Combination Trickling Filter And
Overflow Tank For Secondary Treatment of Wastewater
and Associated Method of Managing Wastewater
Overflow”. Patent 7,238,286 B2. 3 July 2007. Print.
[8] Barcousky, Len. "Alcosan Asked to Adopt 'green' Plan
to Cut Sewage Spills." Pittsburgh Post-Gazette. N.p., 19
Oct. 2012. (Online Article)
http://www.post-gazette.com/stories/local/region/alcosanasked-to-adopt-green-plan-to-cut-sewage-spills-658285/
Considering the amount of controversial issues in engineering
that involve the environment, many students are likely to
choose an essay topic that at least partially touches on
sustainability. Writing this essay has the potential to push
engineering students in the direction of sustainability—which
is critical to the future of engineering.
CONCLUSION: WHY GREEN
INFRASTRUCTURE IS IMPORTANT TO
PITTSBURGH, TO THE FUTURE, AND TO
ME
Ninety percent of Pittsburgh’s drinking water comes from its
three rivers, so water quality is an extremely important issue to
all of Pittsburgh’s residents. When untreated water overflows
into the rivers due to a poorly managed sewage system, the
public health of Pittsburgh’s citizens is threatened and the
ecosystems of the rivers are put in danger as well. Alcosan’s
plan to build more runoff storage containers would indeed
prevent overflow into the rivers, but it does not address the
heart of the problem—that we need to use green infrastructure
to increase the amount of permeable surfaces in the city to
prevent the overflow from occurring in the first place.
Obviously there must be some “gray construction” precautions
set forth as well. The trickling filter water management system
is the right strategy—it combines treatment and storage and
creates a more energy and cost-efficient system. As an
engineer who is concerned about the future of water on earth, I
see the green infrastructure strategies to be sustainable on
many levels. Alcosan should absolutely implement them in
their Wet Water Plan to ensure that the future of water quality
and management in Pittsburgh is sustainable.
ADDITIONAL SOURCES
If the engineers working alongside Alcosan recognize but do
not implement green infrastructure, they are disobeying two
codes of ethics—The ASCE and the NSPE—where it is
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"Combined Sewer Overflows." EPA. United States
Environmental Projection Agency, 16 Feb. 2012. Web.
http://cfpub.epa.gov/npdes/home.cfm?program_id=5
"Consent Decree." Consent Decree.
(Online
Article)
http://www.alcosan.org/WetWeatherIssues/ConsentDecre
e/tabid/63/Default.aspx.
"Code of Ethics." American Society of Civil
Engineers. American Society of Civil Engineers, (Online
Article).http://www.asce.org/Leadership-andManagement/Ethics/Code-of-Ethics/
Davis, Allen P. “Engineered Bioretention for
Treatment of Storm Water Runoff”. CICEET. The
NOAA/UNH Cooperative Institute for Coastal and
Estuarine Environmental Technology (CICEET), 30 Nov.
2003.(OnlineReport)
http://ciceet.unh.edu/briefs/boving_brief/davis_report.pdf
Desha, Cheryl J.K, Karlson Hargroves, Michael
H. Smith, and Peter Stasinopoulos. "The Importance Of
Sustainability In Engineering Education: A Toolkit Of
Information And Teaching Material." Natural Edge
Project. Centre for Environmental Systems Research,
Sept.
2007.
(Online
Journal
Entry).
http://www.naturaledgeproject.net/Documents/ICDPaperFinal.pdf
"LID Urban Design Tools - Bioretention." Lidstormwater.net. Urban Design Tools: Low Impact
Development, n.d. (Online Article). http://www.lidstormwater.net/bio_benefits.htm.
"NSPE Code of Ethics for Engineers." NSPE.
National Society of Professional Engineers, n.d. (Online
Article).http://www.nspe.org/Ethics/CodeofEthics/index.h
tml
"Permeable Pavement." Crwa.org. Charles River
Watershed Association, Sept. 2008. (Online Article).
http://www.crwa.org/projects/bmpfactsheets/crwa_perme
able_pavement.pdf
Garrison, Noah, and Karen Hobbs. Rooftops to
Rivers: Green Strategies for Controlling Stormwater and
Combined Sewer Overflows. Issue brief. N.p.: National
Resources Defence Council, 2011. National Resource
Defence Council. (Online Report)
Scholz-Barth, Katrin. "Green Roofs: Stormwater
Management From the Top Down." Environmental
Design & Construction (n.d.): n. pag. Edcmag.com. Jan.Feb.
2001.
(Online
Report)..
http://www.greenroofs.com/pdfs/archives-katrin.pdf
"Vegetated Swales." Managing Stormwater.
GreenWorks,
(Online
Article)
http://www.greenworks.tv/stormwater/vegetatedswales.ht
m.
topic and for her knowledge of the trickling filter water
management method.
ACKNOWLEDGMENTS
I would like to acknowledge Debra Zuckerman for the
support she provided me in the process of deciding on a
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