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Table of Contents
Section Title Page Number
1. Executive Summary……………………………………………………………………………………………….. 3
2. Introduction…………………………………………………………………………………………………..……... 4
3. Design Layout………………………………………………………………………………………………….…….. 6
3.1. Commercial Area…………………………………………………………………………………....... 6
3.2. Open Space……………………………………………………………………………………….…….... 6
3.3. Residential Area……..…………………………………………………………………….…...……... 6
3.4. Constraints……………………………………………………………………………………………...... 7
3.5. Alternative Options………………………………………………………………………….…….….. 7
4. Water Distribution System……………………………………………………………………………………... 9
4.1. System Design………………………………………………………………………………….………... 9
4.2. Demands and Requirements…………………………………………………………..……….… 9
4.3. Pump Specifications……………………………………………………………………………..…... 11
4.4. Cost Analysis………………………………………………………………………………………........ 11
5. Stormwater Management System…………………………………………………………………………. 12
5.1. System Design…………………………………………………………………………………….….... 12
5.2. A 25-Year Storm…………………………………………………………………………………..…... 12
5.3. Low Impact Design………………………………………………………………………………….... 13
5.4. SWMM Analysis with LID Implementation……………………………………………..…. 15
6. Appendix……………………………………………………………………………………….………………….…... 16
6.1. Tables and Figures……………………………………………………………………………….….... 16
6.2. Sample Calculations………………………………………………………..………………...……... 27
6.3. References……………………………………………………………………………………...…..……. 28
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Section 1: Executive Summary
The city of Tustin, California would like to develop a three hundred thirty acre plot of land with a
layout that includes residential, commercial, and recreational areas, as well as open space. The location
of this development was originally the Tustin Marine Corps Air Station. The community is located
between the busy streets of Jamboree Road and Edinger Avenue near the Tustin Legacy shopping
district.
The three hundred thirty acre plot of land is divided into approximately eighty acres of
commercial space, one hundred fifty acres of residential space, and one hundred five acres of
recreational space and open land. The commercial area contains two large stores, fifty medium
businesses, and thirty restaurants. The residential area is divided into one hundred ninety low end
housing units, eighty high end housing units, and one hundred thirty-five apartment units. The open
land section of the community consists of hiking trails, a nature preserve, a rainfall collection reservoir, a
water storage tower, and a fifteen-acre community park.
The water distribution system for the community is able to deliver sufficient water supply while
reducing the daily peak demands and minimizing cost. In order to do this, a rainfall reservoir will be
implemented to store rainwater runoff, and a pump will aid in increasing water flow and pressure. The
overall estimated cost of installing the pump system is $1,498,249.85 with a charge of $98.24 per day for
electricity to run the pump.
The stormwater management system is designed to handle a 25-year storm, or a storm with a
four percent chance of happening. The community is divided into seven different rainfall
subcatchments. A one-foot diameter conduit collects the water from each subcatchment and runs to
one main junction that leads to the outfall along Peters Canyon Wash. Low Impact Design methods
were implemented in order to reduce the total runoff of the system at a total cost of $18,128,670.00.
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Section 2: Introduction
The area of interest for the team design project is located at the Tustin Marine Corps Air Station
within the city of Tustin, California. This area, shown in Figure 2.1 in the appendix, is approximately half
a square mile, or three hundred thirty acres. The objective of the design project is to develop a new
community and minimize the daily peak water demand, installation, operation costs, stormwater runoff,
and environmental impact while maximizing long-term sustainability of the area’s water resources. The
community must include at least four hundred mixed-income units to house an estimated 1,250 people.
Development plans for recreational and commercial zones are also required. At least thirty percent of
the land must be undeveloped; street layouts must also be included in design plans. The surrounding
area of the site, as well as site elevation, and soil composition must be taken into account when
planning the community. A detailed description of the community layout can be found in section three
of the report.
Water supply for the community comes from a main on Edinger Avenue, which runs along the
eastern edge of the community. Only one water supply connection to the community is permitted from
the main. The pressure in the main must stay within the range of eighty to one hundred pounds per
square inch at all times. The water distribution system must be able to deliver the minimum amount of
water needed for daily domestic and firefighting activity. Adding a pump to the system in order to meet
demands is permitted, but the pump must be modeled after a prototype supplied by the manufacturer.
Cost estimates for the water distribution system were provided by the pump manufacturer,
Construction Company, and Southern California Edison Electricity Company. The water distribution
system as well as cost analysis for the system are discussed in detail in section four of this report.
Rainfall in the community must lead to one outfall along Peters Canyon Wash, which is located
near the south-east corner of the community. A stormwater collection and retention system for the
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community must be designed under the conditions of a 25-year storm event. All data provided for a 25-
year storm was taken from the 1986 Orange County Hydrology Manual. Only gravity is used to move the
water in the system through the conduits. Not only is the design team responsible for creating a system
that ensures no increase in site runoff, but also the design team must decrease the amount of site
runoff by implementing low impact designs. These low-impact designs will be implemented to help
reduce the environmental impact of the entire system. Since no cost estimates for the stormwater
system are provided, it is up to the city of Tustin to determine the total cost of the conduit installation. A
detailed description of the stormwater collection, retention system, and low impact designs can be
found in section five of this report.
Throughout the design process, the team strived to come up with new and creative ideas. With
several goals to keep in mind throughout the process, the team found that simplicity was the most
effective method in accomplishing these goals. The remainder of this report goes into detail explaining
exactly how all of the design team’s ideas were implemented to comply with the research done in the
project.
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Section 3: Design Layout
See Figure 3.1 in the Appendix for the AutoCAD drawing of the community layout.
3.1 Commercial Area
The eighty acre commercial zone, which takes up twenty-four percent of the total land, is
located strategically in the south-west portion of the community in order to expand the already existing
commercial area known as the The District at Tustin Legacy. Developing the commercial area in this
section of the community allows for the area to stay consistent. It allows for residents to not have to be
surrounded by noisy commercial businesses. The area is divided into two large retail stores, fifty
medium level businesses, and thirty restaurants for patrons to enjoy. This area also provides ample
parking space to accommodate the large amount of cars entering the shopping center on a daily basis.
3.2 Open Space
The open space zones offer outdoor activities for the patrons of the community to enjoy. The
open space is composed of one hundred five acres of land covering thirty-one percent of the parcel. The
area is positioned along the south-east border of the community to act as a noise barrier from Jamboree
Road. This area is different from the rest of the zones in the fact that it is not going to be developed.
Hiking trails will be created and natural vegetation will be allowed to grow. The community water
storage tower as well as the rainfall reservoir basin will also be on this parcel. Another section of open
area in the community is the fifteen acre park located near the apartment complex. The park will
provide residents with recreational facilities such as sports fields, a community center, playgrounds, and
barbeque areas. Greenery will be planted on the border of the park to preserve its natural state and to
block noise pollution from outside traffic.
3.3 Residential Area
The high density housing area is located on the north-east part of the community. This portion
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of housing consists of one hundred thirty-five apartment units, which are built closest to Jamboree
Road. Short one way streets are developed in the apartment complex to easily allow residents to reach
the park.
Medium density housing is located in the northern section of the design layout. This area
consists of one hundred ninety houses. Residents are provided with more privacy in comparison to the
high density housing units. The area contains two-way streets with twelve-foot roadways and six-foot
sidewalks. Larger roads are implemented in this housing area to assure safe play for children. Residents
in this community have easy access to Tustin Ranch Road.
Low density housing is located in the northernmost corner of the community. This area is
strategically placed farthest away from Jamboree road so that residents have a quiet living experience.
The eighty houses in this area are the largest of all the residential areas. Since the low density housing
area is the most desirable, it will contain the most expensive housing units.
3.4 Constraints
It was required that open spaces, including recreational areas, must cover at least thirty percent
of the parcel. Also, the community needed to have at least four hundred housing units and house at
least 1,250 people. Other factors that were considered during development were: the existing roads,
soil type, elevation of the land, and the history of the land, to determine if any environmental permits
are needed.
3.5 Alternative Options
To prove the feasibility of the proposed plan for the Tustin Marine Corps Air Station the design
team evaluated several alternatives. In regards to the design layout, another idea that was considered
was having a large central park at the epicenter of the zone modeled after Aldrich Park. The housing
units would then be developed along the border of the park. This would help unify the residents within
the area. Another alternative idea was having a hospital and a police and fire station in the area to
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provide extra protection for residents. The final alternative considered was having a multi-story parking
lot near the commercial zone in order to minimize the amount of lot space needed for parking.
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Section 4: Water Distribution System
4.1 System Design
The community water distribution system was modeled using EPANET 2.0 based on the
AutoCAD layout of the proposed design. A picture of the model, Figure 4.1, can be found in the
appendix. The distribution system pipes were designed to run underneath the streets surrounding each
of the five different community zones with a connection at each zone corner. There are also pipes and
connections running underneath the streets through each zone. The system is made entirely of closed
loops since the pipes are made of flexible material PEX (discussed in Section 4.4). A fire hydrant is
placed every five-hundred feet throughout the system in order to assure maximum safety in the event
of a fire (Lamm). The system was designed using minimal amount of pipes needed to help keep costs
relatively low.
4.2 Demand and Requirements
Each of the five different community zones have different water demands. For each different
zone, the total amount of water used per day was divided between the number of connections
surrounding the zone to ensure that the water demand was constant throughout. These values were
converted to gallons per minute and used as the base demand to input into each node in EPANET. All
water demand values can be found in Table 4.2 in the appendix.
One of the design team’s main goals in creating the water distribution system was to reduce the
daily peak demand of the community while making sure that the system was still able to deliver
sufficient water supply. The commercial zone, which consists of two large stores, fifty medium size
businesses, and thirty restaurants, is the zone with the highest demand of 86,200 gallons per day
(Hickey). Even though the commercial zone is an expansion of the Tustin Legacy shopping district, its
water supply comes completely from the new water distribution system. The toughest task was to
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determine how to get enough water to the zone without increasing total cost. This is why the rainfall
collection reservoir is conveniently located just east of the commercial zone. During peak hours, extra
water gets delivered to the zone from the reservoir so that the pump speed never has to increase and
water pressure in the other communities does not decrease.
Recreational water demand was found by researching parks approximately the same size as the
one in the community design. It was found that parks around fifteen acres in size use about 56,580
gallons of water per day (Leal, Mendoza). The pump for the distribution system was conveniently placed
near the community park which requires the second-most amount of water per day. This helps ensure
that this part of the community constantly receives adequate water supply. Water used in the sprinkler
system to keep the nature trail preserved is taken from the reservoir basin. This means that this demand
was not included in the total system water demand. The water demand of the residential zones were
derived from the fact that the average person uses about one-hundred gallons of water per day in
domestic activities (“Indoor Water Use”). The average number of people per household for each type of
housing was then used to calculate the total amount of water used per day.
Firefighting water demand was also taken into account when designing the system. The
minimum amount of flow needed to fight fires at one instance is 500 gallons per minute for two hours.
The maximum flow needed is 12,000 gallons per minute for four hours. This means that there needs to
be between 60,000 and 2,880,000 gallons ready at all times (Hickey). This is why the system storage tank
can hold 3,000,000 gallons of water. It was demanded that the pressure in the connection to the Edinger
Avenue water main be between eighty and one hundred pounds per square inch at all times. The tank
dimensions were adjusted accordingly with the volume so that this level of pressure is always
maintained.
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4.3 Pump Specifications
Since there was a very minimal elevation change throughout the community, a pump was
needed in order to maintain high flow rates throughout all the pipes in the system. The type of pump
used is a dynamic centrifugal pump because relatively low pressure is needed at the water main
connection, and a high, steady flow rate is needed throughout the entire system. The pump head curve
is scaled based on a small model provided by the manufacturer. The real pump has an impeller diameter
of thirty inches and runs at a constant rate of 1200 revolutions per minute. A graph of the pump head
curve, Figure 4.3, can be found in the appendix.
4.4 Cost Analysis
Another main goal of the design team was to keep costs as low as possible. All water distribution
system costs can be viewed in Table 4.4 in the appendix. Since piping installation cost increases greatly
with increasing diameter, cost is reduced by keeping the diameter of the piping system small. The
diameter used is eight inches for all pipes in the system. The piping material used was Cross-linked
Polyethylene (PEX) and cost efficiency is one of its many benefits. Using this material saves money over
a long period of time because very low maintenance is required. PEX does not experience any corrosion
and has an estimated lifespan of 50 years (Heavens). PEX also allows for high node pressures since it is
flexible. It can make over ninety degree turns so fewer connections are needed (Heavens).
Also, the particular pump specification used will save money in the long run. Pump purchase and
installation cost is a one-time fee, but electricity is charged per day. While having a large impeller size
will increase the purchase and installation cost of the pump, it will allow for a lower pump speed, which
is more energy efficient and cost effective over a long period of time.
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Section 5: Storm Water Collection and Retention System
5.1 System Design
The stormwater management system was modeled using EPA SWMM 5.0, shown in Figure 5.1 in
the appendix. The community was divided into seven regions called subcatchments. Each one
represents an area with a different percentage of imperviousness. The greater the imperviousness, the
less the land is able to store water. Percent imperviousness was found by dividing the area of
impervious objects on a parcel of land by the total area of that parcel. This is why the commercial zone is
divided into three smaller subcatchments instead of one large one. Different sections vary greatly in
imperviousness from forty to eighty percent. If the commercial zone had been left as one subcatchment,
the runoff depth into the conduit would exceed the diameter of the pipe and result in flooding.
In the design, the conduits are circular with a one-foot diameter and are made of smooth
concrete. This material was chosen because it is highly cost effective compared to other alternatives
such as plastic and steel. Smooth concrete is a more durable and sustainable, as it continues to function
with a long life span, thus reducing the costs for repair and replacement. (“Why Concrete Pipe?”) A total
of eight conduits make up the stormwater management system, resulting in a total length of 8,800.62
feet of piping. Rainfall flows from a subcatchment to a conduit and each conduit connects at a junction
that leads to the main system outflow. The system is driven by gravity since the elevation throughout
the land ranges from around forty to fifty feet with a minimal change in slope.
5.2 A 25-Year Storm
A 25-year storm is a flood event that has the probability of a four percent chance of occurring in
a given year. The data for a 25-year storm was compiled using the 1986 Orange County Hydrology
Manual. The compiled data was used to simulate a three hour storm event in SWMM. Only three hours
of rainfall data were needed since the total area of the community is relatively small. Table 5.2 and
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Figure 5.2 in the appendix show the specific rainfall data that was inputted into SWMM.
5.3 Low Impact Design
Low Impact Design (LID) is a land development practice that sustainably manages stormwater
runoff as close to the source as possible (“Low Impact Development”). This minimizes the overall impact
on the environment and reduces the cost of stormwater collection and treatment. The LIDs that were
implemented were chosen based upon the type of land usage within the area. The five types of LIDs that
were utilized in the subcatchments were bioretention cells, vegetative swales, cisterns, green roofs, and
a detention pond.
Bioretention cells, similar to rain gardens, are depressed areas with vegetation at the surface
(“Stormwater Management Best Practices"). Infiltration occurs at the underdrain providing groundwater
recharge, removal of pollutants, and capture of runoff into the soil. Bioretention cells also act as an
effective stormwater management method in parking lots and urban regions where green vegetative
land is minimal. Within the SWMM model, bioretention cells were placed in the parking lots of the
commercial area, reducing the direct volume capacity on the storm drain system, and lowered the peak
discharge rate. In comparison to the cost and benefit from implementing stormwater conveyance
systems, the cost for residential rain gardens average from $3 to $4 per square foot and $10 to $40 per
square foot for commercial areas. This results in relatively low expenses for installation and an adequate
amount of cost savings in the long run (“Bioretention”).
Vegetative swales are shallow trapezoidal shaped channels with vegetation covering the
surface. They are designed to absorb pollutant particles, facilitate infiltration, and slow stormwater
runoff (“Stormwater Management Best Practices"). Swales are a versatile type of LID and well suited for
residential, industrial, and commercial regions. The cost of vegetative swales are generally inexpensive
and range from $3 to $10 per square foot depending on the complexity of the system (“Bioswales”).
Substantial savings are gained with the use of vegetative swales as opposed to traditional stormwater
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piping systems. With proper maintenance, swales can be aesthetically pleasing and are an
environmentally sound alternative to conventional storm sewers. Vegetative swales were implemented
into the SWMM model on the land bordering the edges alongside the roads, in the vast open space as
prairie grass, and as dense grass in the park area.
A detention pond is an excavated area that provides both retention and treatment of
contaminated stormwater runoff (“Storm Water Technology Fact Sheet”). The physical, biological, and
chemical processes of a detention pond work together to remove pollutants. A wet detention basin was
implemented into the model and designed to be three feet high with a circular area of about two acres,
in order to remain a permanently wet pond. The typical construction costs for a detention pond of one
acre-foot is about $41,600 (“Detention Basin Retrofits and Maintenance”).
A cistern is a storage tank that collects runoff on a rainy day. Unlike rain barrels, which are
normally located outside of each residential unit and smaller in capacity, cistern tanks are larger in
volume and can be installed underground, minimizing above ground land usage. Cisterns are great for
the environment because of their ability to conserve and retain water, which reduces runoff into
stormwater drains and the need for water from a far-off source. This type of LID also reuses the
collected rainwater for the purposes of toilet flushing and gardening. The estimated cost for a small
cistern system ranges between $200 and $600 depending on the material and volume (“Rain Barrel and
Cistern”).
A green roof is a layer of vegetation that grows on top of a roof (“Stormwater Management Best
Practices"). The benefits of green roofs includes reducing energy usage, lowering air pollution and
greenhouse gas emissions, slowing stormwater runoff and filtering pollutants from rainfall, and
providing aesthetics and habitat for species. The cost for vegetative roofs average around $10 per
square foot for extensive roofing and $25 per square foot for intensive roofing with a low annual
maintenance cost of $0.75-$1.50 per square foot. Although the cost for green roofs are higher than
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other materials, the benefits gained eventually offset the installation cost after a period of time (“Green
Roofs”).
5.4 SWMM Analysis with LID Implementation
Based on Figures 5.4.1-5.4.4, it can be observed that with the implementation of low impact
designs, the runoff discharge is decreased significantly. During peak hours, the water depth through
conduit seven is greatly reduced, decreasing from 0.9 to 0.45 feet. Figure 5.4.4 also displays that there is
no flooding at each node throughout the entire system after using LIDs.
The reduction in runoff from the application of low impact designs lowers the cost for
stormwater runoff collection and allows for the number of conduits to remain at the minimum number
of eight for the entire system. By combining all LID materials, the total cost comes to an amount of
$18,128,670. A table displaying the cost for each LID can be found in the appendix under Table 5.4.
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Section 6: Appendix
6.1 Tables and Figures
Figure 2.1: Google Earth image of land to be developed provided by the city of Tustin
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Figure 3.1: community design layout modeled using AutoCAD 2013
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Figure 4.1: water distribution system design modeled using EPANET 2.0
Table 4.2: data calculated for community water demand
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Figure 4.3: water distribution system pump head curve
Table 4.4: water distribution system cost analysis
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Figure 5.1: stormwater management system design modeled using EPA SWMM 5.0
Figure 5.2: bar graph of 25-year storm, 3 hour rainfall intensity
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Table 5.2: 25 year storm intensity data for a 3 hour storm
Table 5.4: low impact design cost analysis
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Figure 5.4.1: node water depth before LID implementation
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Figure 5.4.2: node water depth after LID implementation
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Figure 5.4.3: link water depth before LID implementation
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Figure 5.4.4: link water depth after LID implementation
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5.4.5: no flooding detected throughout entire system with LIDs
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6.2 Sample Calculations
Pipe installation cost Using Pipe #3: 733 ft. in length
C ($/ft.) = 1.3 * [D (in.) ^ 1.5] = 1.3*(8^1.5) = $29.42/foot total cost to install pipe #3 = $29.42/foot * 733 ft. = $21,561.67
Tank storage cost Dimensions: 60 ft. in diameter, 140 ft. tall Volume = [(π/4) * D^2] * H = [(π/4) * (60^2)] * 140 = 395,840.67 ft3
Cost = 52 * (V ^ 0.7) = 52 * (395,840.67^0.7) = $430,792.00
Pump scaling
Q2 = Q1 * [(n2/n1) * (D2/D1)^3] = 45 * [(1200/1760) * (30/5.45)^2] = 929.67 GPM
H2 = H1 * [(n2/n1)^2 * (D2/D1)^2] = 23* [(1200/1760)^2 * (30/5.45)^2] = 323.98 ft. Pump installation cost Impeller: 30 in. Cost = $1500 * D = 1500 * 30 = $45,000.00
Total pump cost = $3,500 + 45,000 = $48,500.00
Energy cost Power = (γ * H * Q)/746 = (62.4 * 929.67 * 323.98)/746 = 25.19 KW
Peak Cost = Power * $0.20 = 25.19 * 0.20 = $5.04/hour (8am - 10pm) Off Peak = Power * $0.11 = 25.19 * 0.11 = $2.77/hour (10pm - 8am) 24 hour energy cost = (5.04 * 14) + (2.77 * 10) = $98.24
Impervious Area (%) (Red, Low Residential Area) Total Area: 3545942 ft2
Road Area: 664662 ft2
Open Land: 1143749 ft2
House Area: 1737531ft2
%Impervious = (Road Area + Open Land + House Area) / Total Area = (664662 ft2 + 1143749 ft2 + 1143749 ft2) / 3545942 ft2 = 0.38 = 38%
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6.3 References
“Bioretention.” Urban Design Tools. lid-stormwater.net. n.p. Web. 15 Mar. 2014. <http://www.lid-stormwater.net/bio_costs.htm>
“Bioswales.” Upper Des Plaines River. n.d. Web. 15 Mar. 2014
<http://www.upperdesplainesriver.org/bioswales.htm>
“Detention Basin Retrofits and Maintenance.” Rutgers Cooperative Extension Water Resources Program. 29 Oct. 2010. Web. 15 Mar. 2014. <http://www.richlandtownship.org/stormwater/RutgersPowerPoint.pdf>
"Green Roofs | Heat Island Effect | US EPA." EPA. Environmental Protection Agency, n.d. Web. 15 Mar. 2014. <http://www.epa.gov/heatisland/mitigation/greenroofs.htm>
Heavens, Alan J. "No cool solution to removing heated tiles." The Philadelphia Inquirer. (2006). Web.
<http://articles.chicagotribune.com/2006-08-11/business/0608110020_1_tile-heating-paint>
Heavens, Alan J. "Shortages Persist In Building Materials: Even as Demand for New Homes Falls, Cost of
Cement and Copper Skyrockets." The Philadelphia Inquirer. (2006). Web.
<http://www.washingtonpost.com/wp-dyn/content/article/2006/07/28/AR2006072800771_pf.html>
Hickey, Harry E., Ph.D. Water Supply Systems and Evaluation Methods. Volume II: Water Supply
Evaluation Methods. U.S. Fire Administration. (2008). Web.
<http://www.usfa.fema.gov/downloads/pdf/publications/Water_Supply_Systems_Volume_II.pdf>
“Indoor Water Use in the United States.” Water Sense: An EPA Partnership Program. U.S. Environmental Protection agency. (2008). Web. <http://www.epa.gov/WaterSense/pubs/indoor.html>
Lamm, Willis. “‘Standard’ Hydrant Spacing.” Designing Water and Hydrant Systems. (2000). Web.
<http://www.firehydrant.org/info/design05.html>
Leal, Jose. Mendoza, Cindy. “Outdoor Water Conservation: Compliance and Costs.” Water Use and
Conservation. California Parks and Recreation: Official Magazine of the California Park and Recreation
Society. Volume 68, Number 2. Spring 2012. Web.
<http://www.migcom.com/files/managed/Document/65/Outdoor_Water_Conservation_CPRS_2012.pd
f>
“Low Impact Development.” EPA. Environmental Protection Agency, n.d. Web. 15 Mar. 2014.
<http://water.epa.gov/polwaste/green/>
"Rain Barrel and Cisterns." Urban Design Tool. lid-stormwater.net. n.p. Web. 15 Mar. 2014. <http://www.lid-stormwater.net/raincist_cost.htm>
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"Stormwater Management Best Practices." EPA. Environmental Protection Agency, n.d. Web. 15 Mar. 2014. <http://www.epa.gov/oaintrnt/stormwater/best_practices.htm#cisterns>
“Storm Water Technology Fact Sheet.” EPA. Environmental Protection Agency, Sept. 1999, Web. 15 Mar. 2014. <http://water.epa.gov/scitech/wastetech/upload/2002_06_28_mtb_wetdtnpn.pdf>
“Why Concrete Pipe?” American Concrete Pipe Association, n.d. Web. 15 Mar. 2014. <http://www.concrete-pipe.org/pages/why.html>
Williamson and Schmid. Orange County Hydrology Manual. Orange County Public Works. (1986). Web. 15 Mar. 2014. <http://ocflood.com/civicax/filebank/blobdload.aspx?BlobID=8336>