Feasibility of Using Wetlands and Permeable Pavement for
Storm Water Management
www.epa.gov
Team Leader
William Lake
Team members
Brandon Blanchard
Ross Dalrymple
Jeff Jones
Pablo Sanchez
Executive Summary
This report investigates the feasibility of implementing constructed wetlands and/or permeable
pavement for the management of storm water runoff and pollution in urban areas around the
Detroit metropolitan area. Storm water runoff is a major concern to the quality of local
waterways. The higher the percentage of storm water runoff, the more pollutants are put into the
local waterways and less water is absorbed into the ground water aquifers. The objective of this
report is to determine the best option in terms of money, society and the environment.
The three alternatives that were researched in this report are: constructed wetlands, permeable
pavement, and current water treatment plants. These alternatives were compared using
efficiency, cost, short and long-term maintenance, environmental impact, social benefits, and
governmental issues.
To compare these alternatives, a common site was researched and chosen at the Wal-Mart store
currently being constructed in Clinton Township. To determine the size of the wetland and
parking lot, equations used the calculated area of 25.25 acres. Average rainfall intensity was used
to calculate how much storm water needed to be managed.
All of the criteria were research for each alternative to decide which one would be the best
option to go with. To conclude this, all of the comparisons were taken into account. The wetland
the best option in terms of cost, maintenance, environmental impact, and social benefits. The
water treatment plant is the best option in terms of efficiency and governmental issues.
Introduction
This report investigates the feasibility of implementing constructed wetlands and/or permeable
pavement for the management of storm water runoff and pollution in urban areas around the
Detroit metropolitan area. Storm water runoff is a major concern to the quality of local
waterways. This is a concern in urban and rural areas. Although rural storm water runoff is a
problem, this report will focus on urban storm water runoff.
As more areas become urbanized, more runoff occurs. This is due to impervious pavement and
buildings that prevent storm water from being infiltrated into the ground. The storm water runoff
of natural ground cover is around 10 percent as opposed to the impervious surfaces that have
storm water runoff that is around 55 percent. This diminishes the ground water supply and causes
the local waterways to receive pollution that is picked up by the storm water runoff.
ga.water.usgs.gov
Figure 1 & 2 – Where Earth’s Water Is
Of the 3 percent of the fresh water in the world, 30.4 percent is readily available for people to
use (USGS, 2009). The Lakes, rivers, and streams account for less than one percent of the
world’s water. In 2002, states reported that about 45% of assessed stream miles, 47% of
assessed lake acres, and 32% of assessed bay and estuarine square miles were not clean enough
to support uses such as fishing and swimming (EPA, 2002). After the rain falls it collects on the
roadways and hard surfaces. The rainwater then flows down hill to the lowest surfaces most of
the time being rivers, streams, or ponds. Along the way the rainwater picks up pollutants such
as grease, oils, metals, and airborne particles. These pollutants are collected by storm water and
most of the time reaches our waterways untreated. Some of these pollutants include lead, zinc,
cadmium, polycyclic aromatic hydrocarbons, mineral oil hydrocarbon, and salts that all lead to
the degradation of water (Gobel, Dierkes, and Coldewey; 2006).
With the focus of this report being the Detroit Metropolitan area, the type of storm water
collection system utilized needs to be taken into account. In the Detroit Metropolitan area there is
a high cost of the storm water collection systems in part because the sewer system and storm
water system are a combined system. The piping system for storm water, compared to sewage, is
a much larger diameter, requiring much more material and maintenance that increases the cost.
The transporting of the effluent requires pumping stations that are energy intensive, and we
know of the increasing cost of energy (DWSD, 2009).
www.alertdetection.com
Figure 3 - Water
Treatment Plant
www.infolink.com.au
Figure 4 - Permeable
Pavement
www.ciria.com
Figure 5 - Constructed Wetland
The alternatives that were researched are local storm water wetlands, permeable pavement, and
water treatment plants. The wetlands and pervious pavement help manage storm water runoff by
holding the water for a long enough time that it can seep into the ground thus replenishing the
ground water supply. They also keep the runoff out of the storm water and sewer system. The
water treatment plant will have less water to treat. During major rainfall, the wetlands and
pervious pavement’s infiltration basins help to combat flooding by having the ability to hold
large quantities of water. During these major storms, water treatment plants can become
overtaxed from the high quantity of water that is receives. This can lead to sewer backups and
can lead to the water treatment plant having to bypass the treatment process because it cannot
handle the amount of water it receives. This excess untreated water is bypassed into local
waterways. The wetland and pervious pavement also help to keep pollutants out of the
waterways by filtering the before the pollutants reach the streams and rivers.
To compare costs for all 3 of these alternatives, we did some research to find a site that has a
large parking lot, has not been build yet, and is close to a river or lake. We discovered a WalMart that was under construction and is close to the Clinton River. It is located on Hall road near
Romeo Plank in Clinton Township.
Project Objectives
The Objective of this project is to better manage storm water runoff in urban areas. By managing
the storm water runoff, the cost of treatment can be lowered at the beginning of the runoff stage
instead of the water being put into the extensive sewer system to be treated at a water treatment
plant that can be miles away. This extra distance adds to the cost of treating the storm water.
Managing to storm water onsite also has the added benefit of replenishing the ground water
supply by holding the water long enough for the water to seep into the ground.
Project Users and their Perspectives
The primary audience for the final project will be the Wayne County Department of Public
Services because they oversee the entire infrastructure in Wayne County, which includes all
roads, buildings and land. With the water quality standards that are set by the Environmental
Protection Agency (EPA), something that can help improve the water quality for a cheaper cost
is beneficial to the community. Wayne County Department of Public Services will be the ones
who decide if the wetlands or permeable pavement system will be established. The secondary
audience for the final project will be the engineers and construction managers that will
implement the wetlands or permeable pavement system.
Criteria
The criteria followed in the evaluation is the storm water treated, cost analysis, environmental
impact, and social benefits.

Efficiency
The run-off rainwater is the main concern with the pollutants it carries into the local
water way. The efficiency of each option successfully removes the pollutants and toxics
that are found in the storm water.

Cost
The cost must be the most economical plan for the development project. Since this is a
construction project the initial cost will be high. There will be a cost analysis to
determine which option is the most feasible economically. The cost analysis uses a cost
per day value.

Short- term and Long-term Maintenance
The maintenance for each option is completely different. The maintenance for each
option comes at different cost and different times for each one. This is vital for choosing
the option that makes the most sense for not only short, but long term as well.

Environmental Impact and Efficiency
The environmental impact consists of the toxins and pollutants removed by each option,
affect on the groundwater aquifer, and impact on the local waterways. Each option has a
different efficiency and each will be evaluated separately.

Social benefits
The community benefits are the health benefits and tax relief. The health benefits are the
pollutants removed before the water goes into the waterway or the aquifer.

Governmental Issues
The governmental issues of whether the water being released has been eliminated of the
contaminant up to the EPA standards.
Method
Our evaluation methods come a multitude of experience from academic experience and
professional experience contributed to our initial research and impetus for writing. Some classes
within the group are chemistry, water chemistry (Dr. Mcelmurry), water supply and wastewater
treatment (Dr. Hiedke), Pavement management (Dr. Gates), and Environmental Engineering (Dr.
Hiedke). Some reports include a “design of a storm water runoff piping system” and one of a
“Alternative for Wastewater Treatment Plant Processes”. The Jobs included MDOT pavement
inspection and Hazardous waste control on construction sites.
Three options were looked into for the treatment of storm water. The first was a wetland option
for the processing of the storm water, the second was a Permeable pavement option and the last
was a standard option for the metropolitan area of southeast Michigan. The Group had used
several methods of obtaining facts for these alternatives and the standard; some included web
searches, journal reviews, and academic books. We needed a common site for comparison for
three selected options to relatively connect them by a given area. The area we choose to research
after some deliberation amongst member was a future site of a Wal-Mart superstore located at
Hall road and Romeo Plank in Clinton Township Michigan. We choose this site for the large
area the store will en-compass to ensure an efficient size for the three options. We also choose
this site because the parking lot was not constructed yet and it is located near the Clinton River.
The area was the first calculation required for the site. We had longitudinal and transverse
lengths taken from the scaled aerial view of Google Maps page for the proposed site. The area
was calculated at 25.25 acres.
http://charlesellison.com/work.html
The second general piece of information we needed to incorporate was the precipitation rates,
totals, and averages obtained from the weather network website.
Precipitation
J
F
M
A
M
J
J
A
S
O
N
D
Rain (mm)
24
28
54
75
76
97
85
86
87
57
66
53
Snow (cm)
30
28
18
5
0
0
0
0
0
1
9
31
Total (mm)
50
54
72
80
76
97
85
86
87
58
75
82
The total from this chart is will give us total for the year in millimeters of precipitation. From the
total precipitation we divide by the number of days to get the average amount of mm/d
(Millimeters per day) for the region. A few conversions need to be calculated for millimeters to
meters for daily precipitation and area of acres to meters squared. The average precipitation
multiplied by the area calculates the comparative flow value of 256 m3/d (meters cubed per day).
The flow per day will then be used for the cost analysis of the three options.
Wetland
The wetland required research on the Internet, in journals, and calculations from each as well as
the academic books. The Information we need for the wetland is the base cost. To get the cost of
construction, maintenance, and permits at approximately 35000 to 150000 dollars per acre of
wetland constructed (http://www.bnl.gov/erd/Peconic/Factsheet/Wetlands.pdf). We will use a
50000-dollar per acre (California, 2003) for this study due to the topography of the area. The
area of wetland is needed to calculate the cost and will be determined by calculating the max
flow for a 10yr storm to be able to drain into the wetland and be detained for the required time.
We choose a 10yr storm from usual storm water distribution systems design process since this
wetland will be replacing that system. The following equation is for Intensity of the Area 3 that
our construction site is located.
i
3330
t c  19
The time of concentration for the area is the next piece of information needed for the previous
equation. The time of concentration can be calculated by the following

1.8(1.1 C) 3.28 * D
3
S
C = Runoff coefficient for imperviousness
D = Overland Flow Distance (m)
S = Surface Slope (%)

tc 
With the intensity calculated the max flow is determined by the following equation for the
required 10yr storm.
Q  i(C * A)
A = Area of surface
The Hydraulic loading rate (HLR) needs to within an acceptable range of 4 to 10 m/d (meters per
day)(Wallace 200_). To achievean estimated area for the wetlands we will assume a HLR of 6
m/d. The resulting area is used to determine the cost per acre.
The removal efficiencies were determined by information given by the EPA Design manual for
Wetland construction. Within the document the removal efficiencies were determined by several
case examples that where monitored.
Permeable Pavement
The method for obtaining the information for pervious pavement came from a source of different
mediums. When looking at the pervious pavement it must be compared to the normal
impermeable pavement. The sources used where textbooks, scholar journals, and websites, and
course notes. From these sources of information we found the cross-sectional area, depth, the
efficiencies, and the costs.
Permeable pavement is something that is becoming used more wide spread throughout the US to
treat storm water. Pavements are usually composed of either Hot Mix Asphalt or Portland
Cement Concrete. There is a huge difference in cost between the two options. Concrete is a
stronger pavement that had a longer design life. It is also the more expensive pavement. The
material is more expensive, it takes more man hours, and takes longer to place. So therefore we
are considering Asphalt for this pavement.
Asphalt pavement is composed of three different parts. It is made of a sub-base, base, and the
asphalt layer. A typical cross-section of this is 10 inch sub-base, 6 inch base and a 4 inch asphalt
layer. These layers provide the smallest possible layers for the base and asphalt layers which are
the ones that are more costly. Asphalt pavement is designed to withstand a heavy truck load and
for a 20 year design life. From this you can determine the cost. From company websites you can
find the price for each type of aggregate. Aggregate is what is used in the sub-base and base. The
prices for asphalt were taken from course notes. Using this you can determine the cost of the
parking lot.
Asphalt layer
Sub-base
Base
$3/square yard/inch of depth
$1/square yard/inch of depth
$.5/square yard/inch of depth
Initial Cost = depth of layer*unit price*area
Permeable pavement is slightly different than that of the impermeable pavement. The dimensions
of each part are different, the size of each cross section is larger. There is a geotexitle woven
screen placed to stop the seepage of water into the aquifer. The base is much larger to retain the
storm water that seeps through the pavement. The pervious asphalt layer is smaller than that of
the regular asphalt layer. The asphalt layer is 3 inches, the sub-base layer is 2 inches, and the
base is (-) inches. The asphalt layer and sub-base layer are of typical dimension
(http://www.mnla.biz/industry-resources/landscape- 16/the-next-step- define-pervious). The base
is designed to hold the storm water. The design of the base is
(http://www.crmc.ri.gov/samp_mb/UNHSC_ PA_Spec_ July_07.pdf): Base thickness > rainfall
depth inches /void space
The rainfall is determined by the storm design. The void space is going to be .4 so that the base
has sufficient space for the water to seep through and also still has strength integrity. Once the all
the sizes are determined, the cost analysis is to be performed.
Asphalt layer
$3/square yard/in of depth
Sub-base
$1/square yard/in of depth
Base
$.5/square yard/in of depth
Geotextile fabric
$.1/square foot
Initial Cost = depth of layer*unit price*area
Fabric cost = .1 (area)
Treatment Plant
The Water Treatment Plant in the metropolitan area is ran by the DWSD and has all its costs and
average flow per day as well as efficiencies of the system. The cost for comparison units is for
cost per day in dollars. The cost comparison was calculated by the annual cost for the DWSD to
run the wastewater treatment plant and the average flow handled over one year duration (DWSD
2002).
Overview of Alternatives
Local Storm Water Wetland
Wetlands are regularly saturated surfaces between dry land and water. They are the source that
filters the water running into the streams, rivers, and oceans, cleaning it of the toxins and
pollutants that may contaminate our major waterways. Wetlands are a major part of our
ecosystem and can be found on every continent with the exception of Antarctica. Up until the
mid 1980's wetlands were being drained, demolished and were believed to be useless and viewed
as wild areas that needed to be controlled. The U.S. Army Corps of Engineers were turning the
wetlands into development areas. More then half the United States wetlands were destroyed.
http://geoscape.nrcan.gc.ca/h2o/bowen/images/wetlands_e.jpg
Figure 1 – How a Wetland Works
People began to realize the importance of the wetlands, not only to the ecosystem but also to the
water quality and the ability to protect from floods. Wetlands are like a giant sponge they hold all
the water in the plants and soil during floods, and release the water back when necessary.
Wetlands can store up to 60 days of floodwater. This is very useful during dry periods, the
wetlands are able to draw the water back to the ground and maintain the system. The wetlands
are also very useful in that they help slow down the velocity of the runoff water. This is
beneficial because it helps prevent soil erosion, and also help with the filtration of the water. The
sediment is able to drop out of the flowing water. If the runoff water was not slowed down it
would not have the time to filter out the pollutants and toxins in the water ways.
There are a number of ways that natural wetlands can be created other than human activity.
Some of with are floodwater from nearby lakes or rivers, saturation from rain and runoff, and
groundwater close to the surface that continually flows up. These all cause the several different
types of wetlands. There are four main categorizes of wetlands, marsh, swamp, bog, and fen.
Marsh's are wetlands that are most of the time filled with water. Characterized by the soft
vegetation that grows in the soggy soil conditions. Marsh's are mostly caused by high and low
tides. Swamps are heavily wooded areas with several feet of water. Bogs are small soggy areas
that mainly receive their water from precipitation only. The fen is very similar to the bog in that
it receives its water from the ground water seeping up. Neither bogs nor fens receive any of there
water from runoff or flooding. All these types of wetlands function the same but are caused by
different methods, all help with our ecosystem.
http://www.montgomerycountymd.gov/content/dep/assessment/graphics/wetland .gif
Figure 2- Percent wetlands compared to other land
Wetlands can also be man made and used to intercept storm water runoff from parking lots or
buildings before it gets let into lakes and oceans. These wetlands are constructed to hold
rainwater and remove any pollutants that may have been collected on the roadways. Storm water
wetlands typically don't have all the functions of natural wetlands. They are mainly designed
specifically for flood control and water quality purposes. These wetlands are limited to the
number of site constraints such as soil type, depth of groundwater, contributing drainage area,
and available land area. (Metropolitan council retrieved 2009)
As we look into constructing a wetland for our twenty-five acre lot we had to take into
consideration the amount of rainfall that may accrue in our area. The rainfall intensity for our
area was determined to be 39.92 mm/h. This helped us to calculate what size wetland we would
need to build in order to withstand the amount of water flow off the parking lot. The wetland was
determined to be 26.71 meters wide by 55 meter long by 1.38 meters deep. This size wetland
would be able to withstand the rainwater run off that would accumulate from our location. The
additional cost to construct wetlands of this size for our location was 18,150 dollars with
construction and permit fees. It treats an average of 66043 gallons per day. The resulting cost per
day for wetland is $2.466 dollars.
When constructing your own wetlands you have to consider the various advantages,
disadvantages and other alternatives. Some advantages that come with constructing your own
wetlands is that they are fairly inexpensive compared to treatment plants, and they are very easy
to maintain. These wetlands are a safe reliable way to treat the storm water and store large
amounts of floodwater. Some disadvantages of creating your own wetlands are that they take up
a very large area, some times larger then the actual treatment plant. Depending on how the
wetland is designed, the various slopes of the land, and the permeability of the soil the odder of
the waste may be exposed. The main disadvantage of creating your own wetland is that the
biological process is not well understood and may result in a defective wetland. This is why we
decided to look into other alternatives such as permeable pavements for the parking lot.
http://wetland.maabarot.org.il/AlexsanderWetlands.files/image006.gif
Figure 3- Pollutants removed through wetlands inlet to outlet percentage
Benefits of Constructed Wetlands

They are relatively inexpensive to construct and operate, and easy to maintain.

They provide effective, reliable and ecologically sound wastewater treatment.

They can tolerate both great and small volumes of water and varying contaminant levels.

Wetlands-treated wastewater is retained and can be reused for productive purposes—in fact
the treatment process itself can incorporate productive uses.

They can be aesthetically pleasing and provide habitat for wildlife and human enjoyment.
Disadvantages of Constructed Wetlands

Depending on design, they may require a larger land area than a conventional facility when
value of land can be high in areas where they are more appropriate.

Improperly designed and implemented (too thin a soil layer over the canals, running the
canals down too steep a slope, etc.), constructed wetlands can expose the odor of the waste
stream. Properly designed and built, however, constructed wetlands are odor-free.

The biological processes within a constructed wetland are not well understood and
therefore in theory are unpredictable. In practice they are simple and very stable when
properly designed and installed (sufficient capacity, adequate length of treatment canals,
protection from storm flooding and deep freezing, correct use of both anaerobic and
aerobic stages).

While nutrients are changed to harmless forms year-round by wetland bacteria, actual
nutrient removal is done by growing plants' roots and therefore takes place mainly during
wetland plants' growing seasons. This problem can be partially or completely solved, at
least on a small scale, by running the waste stream through a greenhouse where 'waste'
nutrients can be absorbed and productively used year-round.

In climates with cold winters, bacteria and plants living in the constructed wetland's soil die
back. Not only does this slow or stop nutrient removal during hard freezes, but also there
can be substantial nutrient releases as the organisms previously removing and storing
nutrients die and release their own nutrients back into the system. In large enough systems
(city-wide, for instance), this sudden nutrient release can impact local streams the same
way the original effluent would have (though for a shorter period of time, and during the
dormant season).
Permeable Pavement
According to a study done by the United States Environmental Protection Agency (USEPA),
parking lots have one of the highest pollutant yields among various land uses (Burton and Britt,
2002). Most of the accumulation of contaminants is due to the high vehicular traffic. Wear from
tires, brake and clutch linings, engine oil and lubricant drippings, combustion products and
corrosion, all contribute to the build up of sediment particles, metals, and oils and grease.
Degradation of road surfaces also generates derivatives from asphalt, and runoff from residential
driveways and parking areas can contain driveway sealants, oil, salt, and car care products. All
of these different elements and compounds can accumulate and degrade local water courses over
time (OMOE, 2001). Permeable surfaces are one of the most promising technologies being used
today to infiltrate runoff and reduce pollutant loads from parking areas. Permeable surfaces
allow runoff to infiltrate through voids in the pavement. With the runoff infiltrated into the soil
naturally, it eliminates the need for treatment and reduces the need for underground or site
consuming detention facilities. While considering our options for different permeable surfaces,
we came across three alternatives that each gave a similar performance as far as sediment
removal was concerned. The three options we considered were porous asphalt, permeable
pavement, and interlocking concrete pavers (ICP).
Porous asphalt and concrete work in a very similar manner in that all of the finer aggregates have
been removed. This allows for a matrix of pores throughout the surface to develop in order for
water to permeate through to the sub-pavement reservoir and infiltration bed. ICP consists of
impervious concrete blocks that allow water to infiltrate through inter-block voids or intra-block
spaces (Report).
As mentioned earlier, parking lots have one of the highest pollutant yields among several
different land uses due to increased vehicular traffic. The types of contaminants found in this
type of urban runoff include suspended solids, oil and grease, nutrients, bacteria, heavy metals,
pesticides and chloride from road salt (OMOE, 2003). Improvement in the quality of urban
runoff is possible with the use of permeable asphalt. By allowing water to pass through its pores,
permeable asphalt has the potential to remove or break down contaminants. This is done through
several different processes including adsorption, decomposition and other chemical and
biological reactions with the soil bed (Pitt et al, 1996).
While an improvement in the quality of urban runoff is a huge advantage to using permeable
pavers, one of the greatest risks to using permeable pavers is contaminating groundwater. The
chemicals that are most likely to contaminate groundwater include nitrate, pesticides, polycyclic
aromatic hydrocarbons, enteroviruses, and salts such as chloride (Pitt et al, 1996). As seen as the
last on that list, salts may pose a huge threat due to the fact that road salts are used as de-icing
agents quite extensively here in the Macomb and Wayne counties.
Studies have found that most of the heavy metals found in urban runoff are able to be removed
by way of infiltration through soil (Schueler, 1991, Nightingale, 1978). Nightingale (1978)
researched the buildup of zinc, lead, and copper in the soil of urban runoff retention basins. The
research concluded that in the upper six inches of the soil is where the metals accumulated.
About 6 to 12 inches below the surface of the basins, concentrations of these contaminants were
at normal background levels. A Washington study done by Brattebo and Booth (2003)
concluded that the use of permeable pavement significantly improved storm water concentrations
of copper, zinc, and motor oil. 88 and 100% of impervious runoff samples surpassed
Washington water standards for zinc and copper, respectively. On the other hand, only 6 and
17% of permeable pavement samples exceeded the standards. As we can see, several studies
have already shown the storm water treatment capabilities of permeable pavement. While
several studies indicated that storm water runoff was almost entirely eliminated by all three
surfaces, the deciding factor was cost.
Given the current state of the Michigan economy, we feel it is very necessary provide an
alternative with the least amount of capital needed. With that said, porous asphalt was the
cheapest option. James (2004) reported a cost of approximately $1.50 per square foot for
permeable asphalt and $1.25 per square foot for traditional impervious asphalt. According to
www.paversearch.com, porous concrete ranges in price anywhere from $2.00 up to $6.50 per
square foot and interlocking concrete pavers range in price from $5.00 to $10.00 per square foot.
As we can see, the cheapest option is permeable asphalt. Although it has a greater price per
square foot than it’s impervious counterpart, a more accurate cost comparison can be made if one
takes into account the added costs of storm water management systems. Traditional asphalt
requires water management systems while permeable asphalt provides these requirements
automatically. With that said, we think porous asphalt is the best option available.
Durability is an important aspect that must be considered when comparing permeable to
impervious pavement. Two permeable pavement sites lasted as long, or longer than impervious
asphalt, as reported in a research summary conducted by the Lake County Forest Preserves (Lake
County Forest Preserves, 2003). A comparison of maintenance is also necessary when
considering permeable or traditional pavement. As far as permeable pavement is considered, the
only maintenance that must be done is a cleaning of the surface. This ensures that the voids or
pores are not to be clogged thereby decreasing the infiltration system’s capabilities. This is
recommended to be done four times a year (James, 2004). On the other hand, impervious
pavement requires crack sealing, patching, and eventual replacement (Lake County Forest
Preserves, 2003). It is fair to mention that permeable asphalt can be patched just as well as
impervious asphalt can. It does not require complete replacement or anything of those means.
There are several environmental benefits associated with permeable pavement as well.
Permeable pavement can play an important role in preserving our environment by preserving the
most important natural resource of all, water. By reducing the amount of storm water runoff
carrying pollutants and contaminants entering our natural waterways, permeable pavers helps
protect the quality of our water supplies. The natural infiltration process associated with
permeable pavement allows for recharging of ground water, as well. Another environmental
benefit that results from the use of permeable pavement is the reduction in flooding of our rivers
and lakebeds. Because there is less storm water runoff, there is less water going into our lakes
and rivers. This also helps with the reduction of erosion of riverbanks and streambeds.
Below is a bulleted summary of the advantages, disadvantages, and maintenance associated with
permeable surfaces.
Advantages of Porous asphalt







Flood Control
Water Quality Treatment Recharges Groundwater for Underlying Aquifers
Reduces need for Storm water Infrastructure including Piping, Catch Basins, Retention
Ponds, Curbing, etc.
Reduces Salt and Sand Usage Due to Low to No Black Ice Development
Maintains Traction while Wet due to Decreased Pooling
Reduces Spray from Vehicles
Reduces Roadway Noise by an Average of Four dBs
(http://www.unh.edu/erg/cstev/pubs_specs_info/porous_ashpalt_fact_sheet.pdf)
Disadvantages of Porous asphalt




Proper Construction Stabilization and Erosion Control are Required to Prevent Clogging
Quality Control for Material Production and Installation are Essential for Success
Any Surface Treatment including Seal Coating Will Cause Failure
(http://www.unh.edu/erg/cstev/pubs_specs_info/porous_ashpalt_fact_sheet.pdf)
Not to be Used on Slopes Greater than 6% (http://www.stormh2o.com/may-june2003/pavement-porous-bmps.aspx)
Maintenance of Porous asphalt

Quarterly Vacuum cleaning is Suggested in Order to Reduce Clogging of Pores
(http://www.negrdc.org/Alcovy_Web/reports/Appendix_C.pdf)
Water Treatment Plant
The DWWTP (Detroit Wastewater Treatment Plant) has its advantages as well as disadvantages.
The ability to consistently clean and monitor the wastewater that is processed to governmental
standards is an advantage. The size of the treatment plant being the largest in the Americas has
its benefits by having a single process plant treating such an area increases the efficiencies and
resulting in a lower cost per capita. Some disadvantages might be the high amount of energy
used to transport and process the wastewater. Another disadvantage that is caused by the large
service area is when design year storm and greater occur the system will be over taxed and
release untreated wastewater into the waterways. The treatment facilities combat this issue with
the building of CSO basins from the Rouge River National Wet Weather Demonstration
Project. As the demand to handle larger flows of influent they require more CSO basins to
handle the overflow wastewater to prevent it from entering the rouge river.
The capability of the plant removal efficiency is listed in table 1.
Table I. Comparison of the Pollutant Loading and Mass Discharged from
DRO 049-F during October 1996 to September 2001 (tons/day)
Influent
Discharge
Percent Removal
TSS
TVSS
TS
FOG
CBOD5
COD
TP
TSP
NH4-N
387
295
1969
44
264
982
18877
5920
60870
35
42
1270
12
18
210
4583
1097
54449
91
86
36
73
93
79
76
81
11
ORG-N
TKN
Fe
Zn
(DWSD.org)
41583
97210
13876
1333
12615
64433
4
282
70
34
About 100
79
The treatment plant processed an average of 2.6 million m^3 per day. The cost for the year was
$187 million dollars for the treatment plant. The comparative number results in a 0.05266 per
1000 gallons treated. The cost per day resulted in $3.48 dollar value for the amount treated from
the studied area.
This is a government owned municipality (Nonprofit) that contracts out many of its needed
stages in the treatment of the waste, for example removal of the sludge from incineration, and the
construction of new facilities when demand is increased. Many to most of the contracts go to the
private sector; ever so often a government agency will receive a contract. Their revenues come
from Bonds and financial loans and Water bills paid. The consumer pays through their water bill;
the DWSD considers the amount contributed by each individual or corporate consumer to be
approximately 70% of the per capita demand.
The image below illustrates the chain of processes involved at a wastewater treatment plant.
http://www.umich.edu/~gs265/society/waterpollution.htm
All these processes are highly energy consuming. The pumps required to deliver the sewage to
the plant are one of the processes that is a large portion of the energy consumption as well as the
aeration tank and incineration of sludge.
Evaluation
The evaluation process will consist of cost, efficiency, short-term maintenance, long-term
maintenance, social benefits, and governmental issues. Cost comparisons are by a dollar per
gallon per day value amongst the three options this did include maintenance costs. The shortterm and long-term maintenance have been considered by cost in the previous section, but by
conveyance and hypothetical benefits have not. Efficiencies are determined by how accurately
the options meet the EPA standards. Social considerations are the odor and aesthetically pleasing
factors that affect the people on the personal level. The Governmental issues are deliberated by
bills and others structures setup for the options, incentives (tax breaks), and/or promotional
programs for a desired option.
The permeable pavement was not comparable by cost. Amongst the two options left the
engineered wetland at Hall road and Romeo Plank in Clinton Township Michigan has the lower
cost per gallon per day and the treatment plant at ___ would be next. The wetland costs are low
due to minimum to none maintenance needed, no energy requirements, and a low material cost
for construction (no need for pipes to transport storm water runoff to treatment plant). The
treatment low cost per gallon is due the Infrastructure already there and the size of the treatment
plant increases the efficiency to handle the storm water at a low cost even due to the large energy
requirement to process.
The Wetland has no short-term maintenance but does have a long-term maintenance at
approximately 20 years. This creates a lack of re-occurring cost and gives the owner relief in
planning and general operations. The treatment plant has many short term maintenance and long
term maintenance due to the many mechanical processes use to treat the waste water. This
requires personnel to manage the operations of maintenance in the short run. The long term
maintenance of the treatment plant can be very large when their load increasing over time due to
population growth and increases in commercial properties in their service area. These cost come
when they need to expand the facilities. The Permeable pavement has a frequent re-occurring
short term cost for every quarter of the year for vacuuming. The long term cost could be
approximated at anywhere from 20-40 years were the need to repave the parking lot due to the
life cycle of the pavement.
The EPA standards are frequently meet by the treatment plant which from study's reviewed are
equivalent to the wetland efficiencies. The chart from the research also shows a corresponding of
removal percentages. The permeable pavement was efficient with removal of solids and some
biological matter but they do not meet the requirements set by the EPA.
The wetlands make the parking lot area a more aesthetically pleasing to the majority’s viewpoint.
They also do not leave an odor if constructed properly as stated before. For those that believe
that global warming is an issue a wetland can be considered a carbon sink and storage and on the
environmental side restores natural habitats for wildlife. Permeable pavement can also be
aesthetically pleasing when using linked pavers with a possible designed color schemes or
shapes. On a safety and accessibility issue the pavement reduces black ice from becoming a
hazard. The treatment plants can be socially an eyesore and the odors if not controlled can
become a nuisance and possible health concern for any living or working with the area. The
treatment plant can be located away from most residential or commercial areas and being in one
location reduces the amount of people that are affected by these issues.
The treatment plant has an advantage due to regulations and programs supported from
government over the other two options. Wetlands have many design criteria and research
supported by government but no incentive programs for individual corporations to spend on
alternative methods to reduce the storm water runoff sent to the treatments. Permeable from what
we looked into also had no governmental incentives as well.
Conclusion
The conclusion of this is study is based on the criteria of cost, efficiency, short-term
maintenance, long-term maintenance, social benefits, and governmental issues. Each of the
options has it strengths and weakness. Each criterion will be discussed on its own to determine
the best option. Storm-water treatment alternatives are feasible. There needs to be new methods
of treating this water. Commercial developments should research different methods of treating
this water as the population keeps growing. Eventually the water treatment plant will not be able
to treat all this water. The benefits of different methods of treating this water vastly out weigh the
cons.
Cost is usually the most important criterion when considering any future developments. Among
the options the wetland has the lowest cost when considering cost per day. The cost of the
wetland has a high initial cost but there is almost no annual maintenance cost as the wetland
takes care of itself. This makes the wetland very cost effective. The cost of the wetland is 18,150
dollars with construction and permit fees. Based on cost the wetland is a good option.
All of the options have short and long-term maintenance that must be performed to keep each
functioning properly. The short-term maintenance is less costly than the long-term solutions. The
wetland is the best option when observing the maintenance aspect. It has almost no short-term
maintenance and the long-term maintenance will not be more than that of a total full
reconstruction, which is less than 20,000 dollars. The water treatment plant is the worst for
maintenance. The short-term maintenance is doing preventive maintenance to keep the plant
working efficiently. As the population in southeast Michigan is growing and expanding, there
would be a need for expanding the water plant. This will be long-term maintenance and would be
vastly expensive.
Efficiency of the options depends on the type and amount of the toxins taken out per gallon. The
best option based on efficiency is the water treatment plant. The water treatment plant treats the
most water and can eliminate the toxins properly. The water treatment is already properly suited
up to EPA standards.
The wetlands provide the best social benefits for the community and this development. The
wetland provides an environmentally friendly solution to treat the storm water runoff problem.
The wetland will create a carbon sink area that will reduce carbon released into the atmosphere.
The wetland will also allow water to seep through the soil and allow it to recharge the groundwater table. The water in the aquifer is the number one drinking water source. The wetland
returns the natural habitat to an area where the natural habitat has been destroyed by the
commercial construction.
Governmental issues favor the water treatment plant. The water treatment plant is already up to
the standards of the EPA. They are regularly checked to guarantee this. There are also programs
created for the plant to operate efficiently.
Recommendations
After considering all the options we feel it would be best to combined two of the elements
together. If you combined the permeable pavement with a small efficient wetland you will obtain
the best results. This combination may not be the least expensive but it will be beneficial to Walmart after considering that they are trying to convince everyone they are a greener company.
Cost is usually the most important criterion when considering any future developments. Among
the options the wetland has the lowest cost when considering cost per day. The cost of the
wetland has a high initial cost but there is almost no annual maintenance cost as the wetland
takes care of itself. The only down fall is that you may not have a large enough plot of land to
accommodate a large wetland and a large parking lot. Permeable pavement is the solution to that.
The permeable pavement acts just like the wetlands as in that it filters the water and replenishes
the water table after it rains. The surface is very durable and is able to with stand large
machinery. The downfall with the permeable pavement is that it does not meet the EPA standard
pollutant removal needed. This is why we recommend placing two or three small wetlands on
either end and sloping the sub floor beneath the pavement toward them. The two operating
together will achieve a unit that not only filters the water properly but also recharges the water
table. The combination of wetland and pavement will also help to eliminate some energy costs
that the traditional water company's use to pump the wastewater sewage mix to the treatment
plant.
All of the options have short and long-term maintenance that must be performed to keep each
functioning properly. The short-term maintenance is less costly than the long-term solutions. The
wetland is the best option when observing the maintenance aspect. It has almost no short-term
maintenance and the long-term maintenance will not be more than that of a total full
reconstruction. The water treatment plant is the worst for maintenance. The short-term
maintenance is doing preventive maintenance to keep the plant working efficiently. As the
population in southeast Michigan is growing and expanding, there would be a need for
expanding the water plant. This will be long-term maintenance and would be vastly expensive.
Efficiency of the options depends on the type and amount of the toxins taken out per gallon. The
best option based on efficiency is the water treatment plant. The water treatment plant treats the
most water and can eliminate the toxins properly. The water treatment is already properly suited
up to EPA standards.
The wetlands provide the best social benefits for the community and this development. The
wetland provides an environmentally friendly solution to treat the storm water runoff problem.
The wetland will create a carbon sink area that will reduce carbon released into the atmosphere.
The wetland will also allow water to seep through the soil and allow it to recharge the groundwater table. The water in the aquifer is the number one drinking water source. The wetland
returns the natural habitat to an area where the natural habitat has been destroyed by the
commercial construction. The DWSD should create a program or promote the building of
wetlands so that there are more benefits and incentives for company's like Wal-mart to spend a
few more thousand dollars to insure our environment and habit stays clean and healthy for more
to come. The government or DWSD could provide tax credits or even give money to help
establish greener ideas.
References
California Stormwater Quality Association. (January 2003). California Stormwater BMP
Handbook 9 of 9, New Development and Redevelopment.
http://www.cabmphandbooks.com/
Kadlec, R.H., & Wallace, S. (2008). Treatment wetlands (second edition)
Environmental Protection Agency. (September 1988). Constructed Wetlands and Aquatic Plant
Systems for Municipal Wastewater Treatment,
http://www.epa.gov/owow/wetlands/pdf/design.pdf
Detroit Water and Sewage Department. (September 2002).
http://www.dwsd.org/about/wastewater/volume2/Review_of_Detroit_Wastewater_Treat
ment_Plant.pdf
Percent of water in the world
http://ga.water.usgs.gov/edu/earthwherewater.html
Percent of polluted water
http://www.epa.gov/305b/2002report/factsheet2002305b.pdf
Treatment plant
http://www.dwsd.org/about/index.html