A Stormwater Management Evaluation of the 2007 New
American Home Stormwater Treatment System and the
Stormwater Academy Green Roof
By:
Matt Kelly, Mike Hardin, and Marty Wanielista
FDEP Project number: WM 864 Task 4
September, 2007
©2007 University of Central Florida
Stormwater Management Academy
i
ABSTRACT
The construction, operation and treatment effectiveness of two green roof
stormwater treatment systems in Florida are documented in this report. The first green
roof system is for a residential home in Orlando which is the show case home for the
2007 National Home Builders Show and is called the New American Home (NAH). It is
constructed and integrated with other on-site stormwater management. It uses a cistern to
collect filtrate water from 660 square feet of green roof areas and 1260 square feet of
bioswale areas. In addition, the cistern also collects air conditioner condensate and water
from one laundry wash basin in the home. The stormwater system has been in full scale
operation for about four months (June – September 2007), while the green roof has been
operational for almost one year. Over 30,000 visitors viewed the home. The cistern
provides water for irrigation and is designed to hold about 7000 gallons of stormwater
and gray water. When cistern water reaches the overflow weir, a pump is used to drain
the water from the cistern to an irrigation area on property, thereby preventing any
overflow unless there is a pump failure. Early operation of the cistern required partially
filling it with potable water to provide water for irrigation of the green roof and bioswale
plants.
The second green roof is designed as a passive roof with a shallow (3 inch) media
depth. It covers 800 square feet of the stormwater management academy laboratory
building at the University of Central Florida. Water from a laboratory sink is also
diverted to the cistern. The green roof has been in operation for about 4 months. The
1000 gallon cistern design is equivalent to about 2 inches of runoff over the green roof
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area. The cistern has not overflowed during a two month period of monitoring and with
7.4 inches of rainfall.
Both green roof areas have native plants that have required minimal maintenance
(about twice per year after establishment of vegetation) and are doing exceptionally well
in terms of growth and appearance. Water irrigation from the cistern follows standard
irrigation time and volume practice for ground cover plants in the area or two times per
week and no watering if an equal or greater amount of water has fallen in the previous
one day period.
Water Quality data are also reported for the two systems. The data provides a
bench mark for future Low Impact Development stormwater treatment systems as well as
to assess the improvement in water quality relative to the source generation and cistern
storage. There is water quality improvement when comparing the cistern water with
source water. Also, the cistern water quality parameters are compared with surface water
classifications in the State. The hydrologic and water quality goals of these stormwater
systems are to reduce stormwater runoff volume and improve water quality. These goals
have been met.
The overall results further demonstrate that a residential home and a commercial
building can be constructed with a green roof and the filtrate from the green roof can be
integrated with household sink water, air conditioner condensate water, grade level lawn
overflows, and filtrate water from a bioswale. The combined water is then used for
irrigation of the vegetation on-site. The details in this report help in the design,
construction, and operation of similar stormwater treatment facilities.
iii
ACKNOWLEDGMENTS
This research was supported through an Urban Nonpoint Source Research Grant
from the Bureau of Watershed Management, Florida Department of Environmental
Protection. The financial and technical support of the Florida Department of
Environmental Protection is appreciated. The guidance of Eric Livingston throughout the
research was very valuable. In addition, the help of the Stormwater Management
Academy is noted.
Many students provided technical skills and time, and thus thanks are extended to
those who helped with the construction and monitoring of the two green roof stormwater
systems. Of note, is the work of Eric Stuart. We also wish to thank all of the staff of the
New American Home, and especially Mike Williams with Homes by Carmen
Dominguez, and Jim Schultz from Resource Recovery Inc for their kind attention and
help with the stormwater system construction process.
iv
TABLE OF CONTENTS
TABLE OF CONTENTS ............................................................................................................................. v
LIST OF FIGURES ..................................................................................................................................... vi
LIST OF TABLES ..................................................................................................................................... viii
Introduction .................................................................................................................................................. 1
Objectives ...................................................................................................................................................... 5
The New American Home (NAH) Stormwater Treatment System ...................................................... 7
Stormwater Academy Laboratory Green Roof Stormwater Treatment System ...............................21
Results ..........................................................................................................................................................33
The New American Home (NAH) Stormwater Treatment System .....................................................33
Stormwater Academy Laboratory Green Roof Stormwater Treatment System ...............................35
Conclusions and Recommendations ...........................................................................................................37
Conclusions ..............................................................................................................................................37
Recommendations....................................................................................................................................43
References ....................................................................................................................................................44
v
LIST OF FIGURES
Figure 1: Diagram of the Stormwater Management System at the New American Home 2007 .................... 7
Figure 2: Hydrotech Extensive Garden Roof Assembly (Picture Source from Hydrotech) ........................... 8
Figure 3: Concrete Roof Deck ........................................................................................................................ 9
Figure 4: Hydrotech Waterproof Layer .......................................................................................................... 9
Figure 5: Insulation Installation .....................................................................................................................10
Figure 6: Protection Layer .............................................................................................................................10
Figure 7: Green Roof Planter Boxes ..............................................................................................................11
Figure 8: Media Lifted to the Roof by Forklift ..............................................................................................12
Figure 9: Media Installation ..........................................................................................................................13
Figure 10: Growth Media, Separation Fabric, and Black and Gold TM Pollution Control Media ...................13
Figure 11: Coontie Palm and Muhly Grass with Drip Irrigation ...................................................................14
Figure 12: Solar Panels and Green Roof .......................................................................................................14
Figure 13: Downspouts from roof .................................................................................................................15
Figure 14: Unicell Filtration Box ..................................................................................................................15
Figure 15: Three Unicell Filter Boxes and Sump Pump ................................................................................16
Figure 16: Cistern Construction beneath the Garage .....................................................................................17
Figure 17: Grade Line Drainage Basin ..........................................................................................................18
Figure 18: Weir Cover in Flexipave Driveway .............................................................................................18
Figure 19: Third Floor Patio Showing Artificial Turf over Pollution Control Media ...................................19
Figure 20: Second Floor Planter Boxes with Bromeliads ..............................................................................20
Figure 21: Bioswale .......................................................................................................................................20
Figure 22: Traffideck™ Demonstration of Application Process ...................................................................21
Figure 23: Traffideck ™ Membrane ..............................................................................................................22
Figure 24: Drainage Layer Installation ..........................................................................................................22
Figure 25: Finished Drainage Layer ..............................................................................................................23
Figure 26: Drainage Layer around Drain.......................................................................................................23
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Figure 27: Drainage Layer around Roof Protrusions .....................................................................................24
Figure 28: Black & Gold Pollution Control Media Logistics ........................................................................24
Figure 29: Black & Gold™ Pollution Control Media Installation .................................................................25
Figure 30: Drain Detailing .............................................................................................................................25
Figure 31: Pollution Control Layer ...............................................................................................................26
Figure 32: Separation Fabric Installation ......................................................................................................26
Figure 33: Finished Separation Fabric and Growth Media Placement ..........................................................27
Figure 34: Irrigation System Installation .......................................................................................................28
Figure 35: Irrigation Supply System .............................................................................................................28
Figure 36: Growth Media Installation ...........................................................................................................29
Figure 37: Wind Blanket Installation ............................................................................................................29
Figure 38: Wind Blanket and Growth Media Installation .............................................................................30
Figure 39: Planting, Irrigation and Growth Media Finished ..........................................................................31
Figure 40: Finished Green Roof ....................................................................................................................31
Figure 41: Cistern, Irrigation System and Flow Meter ..................................................................................32
vii
LIST OF TABLES
Table 1: Average Values from Four Different Locations at the NAH ...........................................................33
Table 2: Average Values from Four Different Locations at the NAH ...........................................................34
Table 3: Average Values from the Stormwater Lab Cistern ..........................................................................36
Table 4: Average Values from the Stormwater Lab Cistern ..........................................................................36
Table 5: Water Quality Standards for Receiving Bodies ...............................................................................39
Table 6: Water Quality Standards for Receiving Bodies (Cont.) ..................................................................39
viii
Introduction
As impervious area cover in developed environments continue to increase,
solutions to reduce the increased stormwater runoff volume and pollutants must be found.
The use of green roofs as part of a stormwater treatment train help reduce stormwater
volume and pollutants while protecting and enhancing valuable water resources. The
design, construction, and operation of a green roof in Florida has been demonstrated by
Hardin (2006) and Hardin and Wanielista (2006).
In this report, documented are the construction and operation of a residential
green roof and a commercial green roof, both with cisterns. The cistern also includes the
integration of other on-site generated household waters, other stormwater sources, and
reuse of the water in the cistern for green roof and on-site property irrigation.
The 1996 Census Bureau projection for Florida in 2025 was estimated at 20.7
million people, a 36% increase between 2000 and 2025 (FAIR, 2006). The additional
development brought about by the population growth will have an effect on the water
environment, including greater flood risks, depletion of groundwater for drinking water,
and increased pollution to water bodies. With this in mind, it is important to note the
importance of effectively managing stormwater in the urban setting. Pollution of
stormwater can occur in several ways such as contact with corroded roof materials,
contact with polluted particulate matter on impervious ground surfaces, and contact with
fertilizers and pesticides from lawns and agricultural land (Hardin, 2006).
The source of surface water pollution is classified into two categories: point
source and nonpoint source. Point source pollution originates from single sources and is
regulated; one example includes the millions of gallons of wastewater discharged from
1
the pipes of industrial facilities and municipal sewage treatment plants into rivers,
streams, lakes, and the ocean. On the other hand, nonpoint source pollution comes from
many diffuse locations caused by rainfall or temporarily stored water moving over and
through the ground and is much more difficult to control and regulate. Examples of
nonpoint source pollution include excess fertilizer, herbicides, and insecticides from
agricultural lands and residential areas; sediment from improperly managed constructionsites, crop and forest lands, and eroding stream banks; bacteria and nutrients from
livestock, pet wastes, and faulty septic systems; as well as, atmospheric deposition and
hydromodification (EPA 2007). A majority of the stormwater runoff makes it to surface
waters and if not treated, it may have a negative effect on water quality.
Federal, state, and local government are combating the nonpoint source pollution
problem with stormwater control strategies that include structural best management
practices (BMP) nonstructural BMPs such as those collectively known as low impact
development (LID). Structural BMPs consist of design and construction of permanent
structures and may include bioretention areas, detention ponds, retention ponds, pervious
pavement, and filtration devices. Nonstructural BMPs focus on prevention and removal
of stormwater volumes and constituent loads through non structural methods. Nonstructural BMPs can involve practices and operations during and/or after construction
such as materials management practices that prevent either rainfall or stormwater from
collecting and transporting water quality pollutants, fertilization practices, street
sweeping, and catch basin cleaning (FHWA 2002). Low impact development is a more
site specific stormwater control system that aims at replicating and maintaining the predevelopment hydrologic regime by designing an equivalent hydrologic landscape with
2
micro-scale controls (EPA, 2000). Unlike BMPs which encompass larger areas or
development, LIDs focus on stormwater runoff from one individual site, for example, a
single family residence. A few examples of LIDs are green roofs, bioswales, cisterns,
and below grade infiltration systems.
The use of LIDs are capable of reducing the amount of stormwater leaving a
given site, reducing the amount of pollutants reaching nearby water bodies, and
mitigating the runoff flow into storm sewers. Green roofs have demonstrated the ability
to store a percentage of rain water in its medium depending on the depth of media, as
well as, cycle stormwater back to the atmosphere through evapotranspiration (Hardin
2006). Furthermore, with the incorporation of a cistern in conjunction with a green roof
the runoff volume was reduced by approximately 87% in the Orlando, Florida Region
(Hardin 2006).
The use of a cistern with a green roof allows the water to be captured and then
reused on the site for irrigation, toilet water flushing, or other nonpotable uses. The
cistern water is not limited to runoff from the roof; AC condensate and gray water from
sinks and showers can also be collected. Gray water is any water that has been used in
the home, except water from toilets. Thus gray water is dish washer, shower, sink, and
laundry water. Graywater comprises 50-80% of domestic wastewater in the U.S., and by
capturing it, there is a reduction in the flow to septic systems and treatment plants (Oasis
2005).
Recovery of AC condensate can be quite significant in Florida and is relatively
free of minerals and other solids. The amount of condensate captured depends on the
ambient temperature, humidity, load factor, equipment, and size of the unit. The
3
summers in Florida are ideal for high flows of condensate. The cities of San Antonio and
Austin, Texas developed equations to predict the amount of condensate. As an example,
a 53,000 square foot laboratory building, over a one year period of time, generated
321,227 gallons of condensate with a peak flow of 218 gallons/hr (Tanner 2005). That is
about 6 gallons per square foot of air conditioned space per year. For the New American
Home and the climate conditions typical of Florida and using the equations developed for
the laboratory, approximately 20,000 gallons of condensate may be collected.
Green roofs can also be used in conjunction with other sustainable technologies
such as photovoltaic panels. Studies have found that the efficiency of solar panels
increases as much as 10 – 15% when installed on a green roof compared to a
conventional roof (Köhler 2002). Green roofs improve photovoltaic panels by lowering
the ambient air to the ideal operating temperature of the panels (Wilson 2007). The
output efficiency of the photovoltaics decreases 0.5% for every degree Celsius over the
standard test temperature 25oC (77oF) (Stapleton 2005). The solar panels also provide
shade and wind protection for the plants on the green roof.
This report focuses on the construction and operation of two stormwater treatment
trains; at the New American Home 2007 and Building 4, the Stormwater Lab on the
campus of the University of Central Florida.
4
Objectives
The hydrologic objective for the design of the two stormwater treatment systems
is to minimize discharge from the cisterns. In addition, it is anticipated that the designs
will help improve water quality in the discharge. Another important objective is to
document green roof construction and operation so that others who desire to use these
innovative stormwater treatment systems can do so.
The New American Home 2007 stormwater management system (Figure 1) was
designed to retain 95% of the precipitation that falls on-site. By capturing the sites
rainfall and preventing it from leaving the site, less potentially polluted stormwater will
flow to nearby water bodies and the storm sewer. A 300 sq. ft. green roof was designed
to help mitigate the stormwater flow leaving the roof by evapotranspiration and storage in
the growth media and Black and GoldTM Pollution Control media. A one and a half inch
pollution control Black and GoldTM Pollution Control media was placed below the
growing media to help reduce nutrients leaving the roof and hold some nutrients for the
plants. Similarly, 360 sq. ft of planters with growing media, pollution control media, and
vegetation were placed along side the western and southern sides of the building to add
additional storage and attenuation for the stormwater off the building. The third floor
patio was designed with pollution control media below the pavers and artificial turf to
remove nutrients that may pass through the artificial turf and over the pavers. Bioswales
measuring approximately 1260 sq. ft. were designed to attenuate the stormwater flow
from the site and help recharge the surficial aquifer. Pollution control media was also
placed within the valleys of the swales to provide additional nutrient removal before
reaching the surficial aquifer. Five grade line drainage basins were installed around the
5
site to capture runoff that was not collected in the previously mentioned devices and
convey the stormwater to a weir beneath the driveway and then to the cistern. A 7000
gallon cistern was constructed beneath the garage to store the site’s runoff and then reuse
it to irrigate the green roof, planters, and surrounding landscape. The AC condensate line
from the AC units on the roof was directed to the gutter system of the roof and collected
along with the roof runoff. Grey water from the laundry room sink on the first floor was
also connected to the collection pipes to the cistern.
The Stormwater Management Academy built its second green roof stormwater
treatment system on the University of Central Florida main campus with an objective to
construct a pollution control shallow depth, light weight green roof that would be able to
sustain high winds. This green roof system was designed to not only reuse the
stormwater captured from the green roof, but also make use of gray water in the form of
laboratory sink water as a supplement to stormwater for irrigation. This novel approach
will reduce the potable water use, the amount of runoff from the site as well as reduce the
amount of water going to the waste water treatment plant and can be used as a model for
designing buildings with the H2O seal of approval.
6
The New American Home (NAH) Stormwater Treatment System
The NAH 2007 stormwater management system is made of seven major components:
Figure 1: Diagram of the Stormwater Management System at the New American Home 2007
Legend:
Green Roof (1), Third Floor Patio (2), and Planters (Adjacent to Patio)
Filtration System and Sump Pump (3)
Cistern (4)
Irrigation/Reuse System (5)
Bioswale (6)
Grade Line Drainage Basins (7)
Weir and Overflow to Storm Sewer (8)
7
The green roof was constructed on a flat concrete frame using Hydrotech’s
Extensive Garden Roof Assembly with a 1 ½” depth of Black and GoldTM pollution
control media, a 6” depth of growing media, and native vegetation consisting of
Muhly Grass and Coontie Palm. The growth media is composed of expanded clay,
vermiculite, peat moss, and saw dust. The Black and GoldTM pollution control media
consists of granular recycled tires, expanded clay, and saw dust. Figure 2 illustrates
the components of the roof.
Figure 2: Hydrotech Extensive Garden Roof Assembly (Picture Source from Hydrotech)
Note: A shingle layer was installed above the insulation on the NAH because the green roof didn’t
cover the entire roof. The Black and GoldTM Pollution Control media and an additional separation
fabric were included below the growing media.
The construction of the Hydrotech roof system is illustrated in the figures below.
Figure 3 shows the concrete roof deck the green roof installation is placed. The finished
installation of the waterproof membrane is seen in figure 4.
8
Figure 3: Concrete Roof Deck
Figure 4: Hydrotech Waterproof Layer
The waterproof layer is a rubber-asphalt material which is spread over the
concrete at a 350o F to 450o F at a thickness of approximately 90 mm with a polyester
fabric imbedded into the material when warm and then finished with a 125 mm layer of
the rubber-asphalt material over the fabric. The material takes approximately 48 hours to
cure. At which time the insulation is installed and is seen in Figure 5.
9
Figure 5: Insulation Installation
The insulation has an R-value of five per inch. The insulation was also used for a
slight slope on the roof, insulating the middle of the roof more heavily than the perimeter
of the roof. In the middle area of the roof the thickness of the insulation was near six
inches, resulting in an R-value of 30.
The final layer of the roof before the installation of the media and vegetation is a
second protection layer which is rolled out over the insulation to help protect the
components from construction foot traffic and weather. Figure 6 illustrates the
completed roof assembly up to the media and vegetation installation.
Figure 6: Protection Layer
10
The design of the New American Home 2007 green roof was not to overlay the
entire roof but to outline the perimeter of the building so that it could be seen from the
street. Figure 7 shows the concrete blocks used as planter boxes to contain the media and
vegetation. The blocks were attached to the roof with a heavy duty adhesive and were
spaced with a quarter inch space between them to aid drainage.
Figure 7: Green Roof Planter Boxes
After the planters were in place, the pollution control media and growing media
were lifted on to the roof by a forklift. Figure 8 shows the media in 2 cu. ft. bags being
lifted onto the roof.
11
Figure 8: Media Lifted to the Roof by Forklift
The pollution control media was spread into the planters at a depth of one and a
half inches. A separation fabric was laid over top of the Black and GoldTM Pollution
Control media to prevent the buoyant materials in the Black and GoldTM Pollution
Control media from floating to the top and mixing with the growing media. The growing
media was six inches deep. The installation of the media is seen in Figure 9, and Figure
10 shows the two media with the separation fabric between them.
12
Figure 9: Media Installation
Growth Media
Black and
GoldTM
Pollution
Control Media
Figure 10: Growth Media, Separation Fabric, and Black and GoldTM Pollution Control Media
Coontie palm and Muhly grass were planted and irrigated with flexible drip
irrigation tubing which is intertwined between the plants. In Figure 11 and 12 the
finished green roof is pictured. Figure 12 also illustrates solar panels that are used in
conjunction with the green roof.
13
Figure 11: Coontie Palm and Muhly Grass with Drip Irrigation
Figure 12: Solar Panels and Green Roof
The runoff from the roof including the AC condensate is conveyed to the basement
through four downspouts seen in Figure 13.
14
Figure 13: Downspouts from roof
The roof runoff travels through the downspouts into three 20 micron unicell filter
boxes. Figure 14 and 15 show the filter boxes. A sump pump on the right in Figure 15
pumps the filtered water to the cistern.
Unicell Filter
Sampling location
Figure 14: Unicell Filtration Box
15
Filter boxes
Sump Pump
Figure 15: Three Unicell Filter Boxes and Sump Pump
Figure 16 shows the 7000 gallon cistern which was poured in place below the
garage floor. The cistern is supplied with 3 switches, one that protects the pump by
adding additional water, one that opens a valve to add potable water when the water level
is lower than what is necessary for one irrigation cycle (1200 to 1500 gallons/week), and
one that activates the irrigation pump and irrigates the garage zone landscape when the
cistern reaches maximum capacity preventing overflow to the city sewer.
16
Figure 16: Cistern Construction beneath the Garage
The cistern also receives water from the grade line drainage basin system. The
basins are located in five different locations around the house. Two basins are along the
east side of the garage, two are located on the north side of the home, and one is located
on the south side of the home near the bioswale. The basins are 12” P.V.C located at a
depth of approximately 3 ft and installed at the same level as the cistern. The water
depths in the basins are at the same water depth as the cistern. The basins are also
installed with a filter basket which catches debris and prevents leaves and limbs from
entering the cistern. Figure 17 shows the ground level grate of the grade line drainage
basin system.
17
Figure 17: Grade Line Drainage Basin
The water from the drainage basins flows into a weir, which is below the
driveway. In case of overflow the water will travel over the weir and into the storm
sewer. The driveway is also made of porous material which allows water to infiltrate into
the ground rather than run off into the street. Figure 18 illustrates the location of the
weir.
Figure 18: Weir Cover in Flexipave Driveway
18
Figure 19 is a picture of the 3rd floor patio with Black and GoldTM pollution
control media below the artificial turf. The patio has a waterproof membrane over the
concrete floor with drains protruding into the planters on the outside of the patio. A
plastic drainage layer is placed above the waterproofing with a permeable moisture mat
above it. A one-inch layer of Black and GoldTM pollution control media is placed on the
mat and the artificial turf rolled out on top of it.
Figure 19: Third Floor Patio Showing Artificial Turf over Pollution Control Media
The planters along the perimeter of the building on the second floor and third
floor have a similar assembly as the green roof. The planters have a waterproofing layer
with a drainage layer and moisture mat. Above the moisture mat is a one-inch Black and
GoldTM Pollution Control media layer, separation fabric and a four inch growing media.
The plants in the planters consist of cacti, bromeliads, and Muhly grass. The plants are
also irrigated with drip irrigation. Figure 20 shows the second floor planters.
19
Figure 20: Second Floor Planter Boxes with Bromeliads
Figure 21 shows the bioswale which is shaped with rolling hills. The valleys are
planted with coontie palms and the crests are planted with Muhly grass. The valleys are
also filled with Black and GoldTM Pollution Control media.
Figure 21: Bioswale
20
Jim Schultz and Resource Recovery Inc. were responsible for supplying and
installing the filtration system, sump pump, cistern switches, grade line drainage basins,
and reuse plumbing for the site.
Stormwater Academy Laboratory Green Roof Stormwater Treatment System
The stormwater academy laboratory green roof was constructed over a concrete
roof with an area of 800 square feet. The water proof membrane used was Traffideck™
which is a spray applied membrane which incorporates the water proofing, protection,
and root barrier layers in one layer (see Figures 22 and 23). The membrane is fully dried
in four hours and can support heavy equipment.
Spray Applied
Membrane
Figure 22: Traffideck™ Demonstration of Application Process
21
Membrane
showing on wall
Primer and sand
over membrane
Figure 23: Traffideck ™ Membrane
The drainage layer selected was the Colbond Enkadrain & Retain™ due to it
being light weight, having a high recycled content, and its ability to hold water for plant
use while allowing excess water to freely drain off the roof (see Figures 24, 25, 26, and
27).
Roll product for
easy installation
Figure 24: Drainage Layer Installation
22
Use duct tape or liquid
nails to temporarily
secure drainage layer
sections to one another.
Figure 25: Finished Drainage Layer
Overflow Drain
Green Roof
Drain
Drainage
Layer
Figure 26: Drainage Layer around Drain
23
Edge detail
for drainage
layer
Stand Pipe detail for
drainage layer
Figure 27: Drainage Layer around Roof Protrusions
The Black & Gold™ pollution control layer was installed directly on top of the
drainage layer and is one inch thick (see figures 28, 29, 30 and 31). The drain area was
covered with a clear dome to protect the drain from debris and allow regular inspection of
the drain (see Figure 30).
Black &
Gold™
Pollution
Control Media
Figure 28: Black & Gold Pollution Control Media Logistics
24
Easy
Installation
Figure 29: Black & Gold™ Pollution Control Media Installation
Drain Protection
allowing for easy
inspection
Figure 30: Drain Detailing
25
Black & Gold™
Pollution Control
Media
Figure 31: Pollution Control Layer
The separation fabric was installed on top of the pollution control layer (see
Figure 32) which is composed of granular recycled tires, expanded clay, and saw dust.
This is done to prevent particle migration due to the buoyancy of the rubber tire and to
ensure good contact with the water.
Separation Fabric
Figure 32: Separation Fabric Installation
26
The bags of growth media placed on the separation fabric helps hold the fabric in
place until the growth media can be installed (see Figure 33). The growth media was
chosen based on the success of the Student Union green roof and consists of expanded
clay, vermiculite, and peat moss. The media is light in color to ensure the media does not
get too hot and has a high organic content to support healthy plant growth. The media is
also designed to be light weight and have a high water holding capacity while
maintaining air voids. This is important because if the media compacts easily there is a
risk of suffocating the plant roots when the roof is walked on for normal maintenance.
Growth Media
Placement
Separation
Fabric
Figure 33: Finished Separation Fabric and Growth Media Placement
The irrigation system selected for this roof was a surface drip irrigation system
(see Figures 34, 35, & 36). This is done to prevent the waste of irrigation water that
occurs via overspray that is typical when using spray heads. In addition, this irrigation
technique will encourage the plant roots to grow out as well as down. This is important
in applications where there is little root zone available. Rather than placing the drip
irrigation lines at the root ball where the water will migrate downward, placement of the
drip lines on the surface encourages the plant roots to grow out and cover the roof.
27
Irrigation Supply
Pipes
Figure 34: Irrigation System Installation
Irrigation Supply
Lines
Figure 35: Irrigation Supply System
The growth media was installed next. Due to the use of a wind or erosion control
blanket the media had to be installed in a particular manner (see Figures 36, 37, and 38).
It is desired to weave the wind blanket into the growth media for more stability. This was
achieved by installing the growth media in rows with high points and low points (see
Figure 36). The wind blanket was then rolled over the growth media with the rest of the
growth media placed on top of it (see Figures 37 & 38).
28
Growth Media
Installation
Separation
Fabric
Figure 36: Growth Media Installation
Wind Blanket
Growth Media
Figure 37: Wind Blanket Installation
29
Wind Blanket
Woven into the
Growth Media
Figure 38: Wind Blanket and Growth Media Installation
The final steps in the green roof installation were the planting and the drip
irrigation lines (see Figures 39 & 40). The drip irrigation lines (Netafim) were attached
to the irrigation supply pipes shown in Figure 35 and laid across the roof with a spacing
of one foot on center. The plants used were Dune Daisy and Coral Honeysuckle. These
plants have already proven to be hardy and able to withstand the harsh conditions of the
roof top environment on the Student Union green roof. Due to the shallow depth of the
growth media plants in four inch pots were used. The planting was done by cutting an X
in the wind blanket where the plant was to be placed, removing the media in that spot,
placing the plant in the resulting hole, and replacing the media and wind blanket.
30
Drip Irrigation
Lines
Dune Daisy
Native Plants
Wind Blanket
Figure 39: Planting, Irrigation and Growth Media Finished
Dune Daisy and
Coral
Honeysuckle
Native Plants
Figure 40: Finished Green Roof
31
Due to the shallow depth of the growth media, two inches, and pollution control
media, one inch, quantification of the effectiveness of the system to reduce stormwater
runoff was desired. To achieve this, a 2537 paddlewheel flow sensor was used to
monitor the volume of overflow that occurs from the system (see Figure 41). This sensor
is connected to a data logger which records data every 5 seconds and is downloaded no
later than 3 days after a storm event due to memory restraints.
1000
Gallon
Cistern and
Irrigation
System
Flow Meter
Cistern
Overflow
Figure 41: Cistern, Irrigation System and Flow Meter
32
Results
The New American Home (NAH) Stormwater Treatment System
The New American Home 2007 green roof was completed in November of 2006
and as the Show Home for the National Association of Home Builders at the International
Builders Show in February 2007. The stormwater management included water from the
green roof, a home sink, air conditioner, yard inlets, and a bioswale. The system was
monitored under full functionality for four months (June-September). There was no
overflow from the cistern. Water quality in the cistern, drainage basin, sump pump, and
before filtration was measured. Tables 1 and 2 show the average values for the complete
stormwater system. The filter sample was a composite from each filter box (See Figure
14 and 15 for a picture of the filter system). Water samples were taken at each location
on days without rain due to standing water in each location. However, when it was
raining, water was also sampled. There were no significant differences in the quality of
water during a rain event and when there was no rain event. This could be because of
the large volume of water in the cistern and the frequency of rainfall.
Table 1: Average Values from Four Different Locations at the NAH
Sample
Location
pH
Alkalinity
TSS
TDS
Total
Solids
Conductivity
Turbidity
BOD5
(mg/l)
(mg/l)
(mg/l)
(mg/l)
µS @ 25C
NTU
(mg/l)
Drainage
Basin
6.27
45
12
107
119
129
2.96
7.13
Before
Filter
6.81
45
24
134
158
140
1.72
11.68
Sump
Pump
6.88
45
7
135
142
137
2.30
9.02
Cistern
7.45
88
2
161
163
216
0.76
1.37
33
The pH and alkalinity in the cistern increased in comparison to its inputs (basins
and sump pump). The filter was effective at removing TSS. The higher TSS value in the
cistern was most likely due to the combination of inputs to the cistern, i.e. drainage basins
and sump pump. The TSS and turbidity in the cistern decreased in comparison the other
three locations. Furthermore, biological activity was most prominent in the filter boxes at
a BOD5 of 12 mg/L which came directly from the green roof, however, the cistern
sample dropped to a value of 1.37 mg/L.
Table 2: Average Values from Four Different Locations at the NAH
Fecal
Coliform
(cfu/100
ml)
(cfu/100
ml)
118
733
2
39
216
337
71
6144
39
91
896
121
329
46
76
60
37
NH3
NOx-N
Nitrite
TN
SRP
TP
(μg/l)
(μg/l)
(μg/l)
(μg/l)
(μg/l)
(μg/l)
Drainage
Basin
270
333
19
4706
24
Before
Filter
481
1161
71
5190
Sump
Pump
191
1437
113
Cistern
48
185
12
Sample
Location
E. Coli
The nutrients and bacteria concentrations were lower in the cistern compared to
the other locations. The filter boxes contained the highest level of ammonia at 481µg/L
(0.48 mg/L) while the cistern contained an average concentration of 48µg/L (0.05 mg/L).
Nitrate levels in the sump pump sample were at an average concentration of 1437µg/L
(1.44 mg/L) and the cistern sample concentration was at a level of 185µg/L (0.185 mg/L).
In the sump pump location, it should be noted that organic nitrogen was the primary
species in TN or approximately 67% of TN. Organic nitrogen was not measured for all
samples. The cistern concentration of organic nitrogen was about 30% of the TN.
34
Soluble reactive phosphorus (SRP) was the only constituent that had a higher
reading in the cistern than the other sample locations. The level in the cistern on average
was 7ug/L higher in the cistern (46µg/L) then the filter boxes and the sump pump
(39µg/L). These values are considered to be very low. Total phosphorus however was at
a concentration level of 76µg/L in the cistern compared to 216µg/L and 91µg/L in the
filter boxes and the sump pump.
Thus a reduction in total phosphorus was noted.
Fecal Coliform level was the lowest in the cistern at an average count of 60
cfu/100mL but was as high as 896 cfu/100mL in the sump pump sample. E Coli was the
lowest in the drainage basins with an average count of 2 cfu/100mL with the cistern
being the second lowest with a count of 37 cfu/100mL. The sump pump sample
contained the highest concentration of E Coli with an average count of 121 cfu/100mL.
The average concentration difference between the cistern and the other locations
may be attributed to the cisterns larger volume. The average volume of water in drainage
basins, filter boxes, and sump pump at the time of sampling were approximately 2
gallons, and the average volume of water in the cistern at the time of sampling was
approximately 3000 gallons. The cistern could hold as much as 7000 gallons.
Stormwater Academy Laboratory Green Roof Stormwater Treatment System
The Stormwater Lab green roof stormwater treatment system was completed in
mid July 2007. As of mid-September 2007 there has been no overflow from the 1000
gallon storage cistern. Shown in Tables 3 and 4 are the average water quality
concentrations in the cistern for the August 14th and August 21st, 2007 sampling dates.
There was no laboratory sink discharge to the cistern during this two month time period.
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Table 3: Average Values from the Stormwater Lab Cistern
Site pH
Alkalinity
(mg/l)
TSS
(mg/l)
TDS
(mg/l)
Total
Solids
(mg/l)
Conductivity
µS
Turbidity
NTU
BOD5
(mg/l)
7.90
180
5
352
357
516
1.18
2
The pH is slightly above neutral at 7.9 and the alkalinity is 180 mg/L. The TSS and
turbidity values are low and TS is 357 mg/L. The conductivity (516 µS) and turbidity
(1.18 NTUs) coincide with the TDS and TSS respectively. Little biological activity is
taking place in the cistern with a BOD5 concentration of 2 mg/L.
Table 4: Average Values from the Stormwater Lab Cistern
(μg/l)
Fecal
Coliform
(cfu/100
ml)
E. Coli
(cfu/100
ml)
53
257
0.5
NH3
NOx-N
Nitrite
TN
SRP
TP
(μg/l)
(μg/l)
(μg/l)
(μg/l)
(μg/l)
70
30
5
4633
37
The majority of nitrogen in the cistern is organic nitrogen (4533 µg/L). The
ammonia concentration (70 µg/L) is higher than the nitrate and nitrite concentration (30
µg/L). The soluble reactive phosphorus (37 µg/L) is more than half the total phosphorus
(53 µg/L). The fecal coliforms in the cistern are at a level of 257 cfu/100mL and the E.
Coli is much lower at 0.5 cfu/ 100mL).
The water quality concentrations of the stormwater lab cistern are higher than
those at the New American home presumably because of the filter arrangement at the
New American Home. However, cistern concentrations are still low relative to
stormwater concentrations for Solids, Turbidity, Nitrate, TP, SRP, Coliforms, and BOD5.
36
Conclusions and Recommendations
The New American Home and the Stormwater Laboratory green roof stormwater
treatment systems with their cisterns are in operation. Demonstrated are successful
construction and operation of integrated stormwater treatment systems with irrigation.
Conclusions
Water quantity data collected for the New American Home and for the
Stormwater Lab showed in the period of measurement that there was no discharge from
the cistern. The New American Home has a pump which will irrigate water on an
irrigation schedule but also is used to distribute irrigation water on property when the
cistern water nears the overflow weir from the cistern. The Stormwater Lab green roof to
date has received 7.4 inches of rainfall or 3690 gallons and has produced no overflow
(runoff). Both systems are expected to overflow at some time, but it has not been
recorded to date.
Water quality parameters of interest are pH, alkalinity, total suspended solids,
total dissolved solids, total solids, conductivity, turbidity, BOD5, ammonia,
nitrate+nitrite, nitrite, total nitrogen, soluble reactive phosphorus, total phosphorus, fecal
coliforms, and E-coli. These parameters are compared to surface water standards of
Class I potable waters and Class III recreational waters.
The New American Home had several sampling points, namely, two of the five
grade line yard drainage basins, each of the three filters, the sump pump reservoir, and
the cistern. The five grade line drainage basins collect stormwater from the ground level
and direct it to the cistern. The three filters receive water from the roof top which is
about 1500 square feet and includes 300 square feet of green roof, plus water from the
37
home sink and air conditioner condensate. The runoff is directed from the filters to the
sump pump reservoir before being routed to the cistern. This sampling strategy shows
how the water quality changes throughout the stormwater treatment system.
The pH and alkalinity for the New American Home meet the water quality
standards for Class I and III waters (see Tables 5 & 6). The pH for all the sampling
points is near neutral with the highest pH of 7.45 in the cistern. The alkalinity for the
cistern is the highest of the sampling points which could account for the more neutral pH.
The solids, conductivity, and turbidity data for the different sampling points meet
all the applicable water quality standards for Class I and III waters (see Tables 5 & 6).
The total suspended solids concentration was reduced from the filters to the sump pump
reservoirs. The samples from the cistern show the lowest total suspended solids
concentration while the total dissolved solids and total solids are higher relative to the
other sampling points. This reduction in total suspended solids is likely due to settling
taking place in the cistern. The conductivity and turbidity results support this assertion.
The BOD5 results also show the cistern having the lowest concentration. This is
important since the cistern is the point where runoff will occur if the system reaches
capacity. The water quality standards state that waters discharged cannot depress the
dissolved oxygen in the receiving body to less than 5 mg/L for Class I and III waters (see
Tables 5 & 6). The New American Home as a single residential unit with a stormwater
management system designed as measured produces a water quality that if discharged
will have little effect on any receiving water body therefore meeting the standards listed
in Tables 5 and 6.
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Table 5: Water Quality Standards for Receiving Bodies
Standards
Class I:
Potable
Water Supply
Site pH
Not less
than 6 or
greater
than 8.5
Alkalinity
TSS
TDS
(mg/l)
(mg/l)
(mg/l)
-
≤500 as a
monthly avg.;
≤1,000 max
Not less
than 20
Total
Solids
(mg/l)
Not less
than 6 or
Not less
greater
than 20
than 8.5
Source: FAC 62-302.530, Criteria for Surface Water Quality Classifications
Class III:
Recreation,
etc...
Conductivity
Turbidity
BOD5
µS @ 25C
NTU
(mg/l)
-
Not more than %50
above background
or 1275 whichever
is greater
≤ 29 above
natural
background
conditions
Nothing that
reduces DO
below 5
mg/L
-
Not more than %50
above background
or 1275 whichever
is greater
≤ 29 above
natural
background
conditions
Nothing that
reduces DO
below 5
mg/L
39
Table 6: Water Quality Standards for Receiving Bodies (Cont.)
NH3
NOx-N
Nitrite
TN
SRP
TP
Fecal
Coliform
E. Coli
(μg/l)
(μg/l)
(μg/l)
(μg/l)
(μg/l)
(μg/l)
(cfu/100 ml)
(cfu/100 ml)
Not exceed
200
Not exceed
200
Not exceed
200
Not exceed
200
Standards
Class I: Potable
≤20
≤10,000
Water Supply
Class III:
Recreation,
≤20
etc...
Source: FAC 62-302.530, Criteria for Surface Water Quality Classifications
<10 in marine
waters only
Also it is recognized that the potable standards for nutrients relate to health effects and nutrient levels less than the standards can cause
eutrophication problems in surface water bodies.
Ammonia and nitrate+nitrite are the only two nitrogen species examined that has
classification standards. Class I and III waters specify that ammonia must be below or
equal to 20 μg/L and for Class I waters, nitrate must be below or equal to 10 mg/L (see
Tables 5 & 6). The data in the results section shows that none of the New American
Home samples meet either of these standards for ammonia but all meet the nitrate+nitrite
standard for Class I waters. Since this water is being stored on-site and being reused for
irrigation the nitrogen species will be beneficial to the plants, which will utilize these
nutrients for growth. Also, with the significant volume reduction, the stormwater
systems will help reduce mass and thus be an important part of any plan to meet TMDL
standards.
The ammonia, nitrate+nitrite, and nitrite data presented in the results section of
this report give some evidence for nitrification occurring in the filter and sump pump
reservoir sampling locations. This is evident in the lower ammonia concentration and
higher nitrate+nitrite and nitrite concentrations. Total nitrogen concentrations are high
except for the cistern which is significantly lower than the other sampling locations. The
cistern had a significantly lower concentration for all the nitrogen species studied, this
could be due to the addition of potable water to the cistern to perform irrigation when
there was insufficient runoff volume after start up of the green roof in November of 2006.
Total phosphorus has a Class III discharge standard of less than or equal to 10
μg/L for discharge to marine waters (see Tables 5 & 6). Neither green roof system
discharges into a marine water body so this standard is irrelevant for this report. That
being said, none of the sample points meet this standard, however, since this water is
being stored on-site and reused for irrigation the nutrients will be beneficial to the plants.
40
Total phosphorus concentrations were significantly lowered from the filter sampling
point to the sump pump reservoirs. This is expected since the filters are removing the
particulates which are associated with total phosphorus. Soluble reactive phosphorus
(SRP) and total phosphorus concentrations were low, less than 1 mg/L for all sampling
points, showing the removal effectiveness of the Black & Gold™ pollution control
media.
Fecal coliforms and E. coli are important parameters due to health risks associated
with them. The standard for Class I and III waters is less than 200 cfu/100 mL (see
Tables 5 & 6). All sample points except the cistern fail to meet this standard. The
cistern, however, is well below this limit with a concentration of 60 and 37 cfu/100 mL
for fecal coliforms and E. coli respectively.
The Stormwater Lab green roof stormwater treatment system also had the
previously mentioned parameters analyzed. The pH and alkalinity for the Stormwater
Lab samples, which were taken directly from the cistern, also meet the standards for
Class I and III waters (see Tables 5 & 6). The cistern water has a pH close to neutral and
is well buffered.
The solids, conductivity, and turbidity data for the Stormwater Lab green roof
stormwater treatment system meet all the applicable water quality standards for Class I
and III waters (see Tables 5 & 6). The total solids are largely made up of dissolved solids
with suspended solids making up a small fraction of the total solids. This is also verified
with the conductivity and turbidity data as well. The lower suspended solids will
minimize maintenance requirements for the drip irrigation lines.
41
The BOD5 concentration in the cistern at the stormwater lab, like the New
American Home, is also low. This lower concentration most likely will not affect or
depress the dissolved oxygen in the receiving body and help maintain 5 mg/L for Class I
and III waters (see Tables 5 & 6). A stormwater management plan designed similar to
the stormwater lab green roof stormwater system reduces the volume of annual runoff by
about 80% and improves the discharge water quality.
Class I and III water standards mandate that ammonia must be below or equal to
20 μg/L and for Class I waters; nitrate must be below or equal to 10 mg/L (see Tables 5
& 6). The ammonia data show that for Class I and III; standard are not being met. The
nitrate+nitrite concentration is well below the standard for discharge to Class I waters.
Since this water is being stored on-site and being reused for irrigation most of the
nitrogen species mass will retained on-site and prevented from overland flow to nearby
surface waters. Despite the low ammonia and nitrate+nitrite concentrations, total
nitrogen is high. This is indicative of a high organic nitrogen concentration. However,
with the significant volume reduction the mass of organic nitrogen that leaves the site is
minimal.
Total phosphorus has a Class III standard of less than or equal to 10 μg/L for
discharge to marine waters (see Tables 5 & 6). The Stormwater Lab green roof cistern
does not discharge to marine waters so this standard is not relevant. That being said the
cistern discharge exceeds this standard, however, since this water is being stored on-site
and reused for irrigation the nutrients will be beneficial to the plants. Both SRP and total
phosphorus concentrations were low, less than 1 mg/L, showing the removal
effectiveness of the Black & Gold™ pollution control media used on the green roof.
42
Fecal coliforms and E. coli were also measured for the Stormwater Lab green roof
stormwater treatment system. It is believed that the rodent populations and birds in the
area may contribute to the coliform levels. The standard for Class I and III waters is less
than 200 cfu/100 mL (see Tables 5 & 6). The Class I and III standards are met for E. coli
but not fecal coliforms.
The stormwater management systems for both the New American Home and the
Stormwater Lab are reducing the amount of runoff and improving the water quality of the
runoff. The water quality parameters measured and presented in the results section of
this report indicate that the cistern water is acceptable for irrigation purposes.
Recommendations
The green roof stormwater management system designed for water quality
improvement and stormwater volume reduction has been demonstrated to achieve these
water quality improvements and volume reductions. The following are recommended:
1. The design, construction and operation of the two green roof stormwater
treatment systems should be considered for other on-site locations.
2. A cistern should be used as part of every green roof.
3. Green roof filtrate, household fixture water, and stormwater from other on-site
locations should be consider for cistern storage, and
4. The cistern storage should be used for irrigation and other beneficial non
potable uses.
43
References
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of Transportation. 2002. Website:
http://www.fhwa.dot.gov/environment/ultraurb/uubmp3p1.htm
2. Federation for American Immigration Reform (FAIR). “Florida: Census Data.”
Washington D.C. 2006. Website:
http://www.fairus.org/site/PageServer?pagename=research_researchd184
3. Florida Administration Code (FAC). “Criteria for Surface Water Classifications”
FAC 62.302-530. Florida 2006.
4. Hardin, Mike. “The Effectiveness of a Specifically Designed Green Roof
Stormwater Treatment System Irrigated with Recycled Stormwater Runoff to
Achieve Pollutant Removal and Stormwater Volume Reduction.” Orlando.
December 2006. Website:
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