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Rainwater harvesting : a viable option for Vancouver’s City Works Yards Aceto, Mariah 2014-04-04

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University of British Columbia     Rainwater Harvesting: A Viable Option for Vancouver’s City Works Yards  Mariah Aceto April 04, 2014           Report prepared at the request of the City of Vancouver, in partial fulfillment of UBC Geog 419: Research in Environmental Geography, for Dr. David Brownstein. 2  Table of Contents  Content          Page Number Executive Summary          3 1.0 Introduction          4  1.1 What is Rainwater Harvesting?       4  1.2 Rainwater Harvesting Benefits       5 2.0 Methods           6 3.0 Literature Review          7   3.1 Catchment Surface        7  3.2 Cistern          8  3.3 Filtration/Purification        10  3.4 Other Sources of Water Loss       12 4.0 Interview/Site Tours         12  4.1 Sites with Rainwater Harvesting       12   4.1.1 Creekside Community Centre      12   4.1.2 VanDusen Visitor Centre      13   4.1.3 Conclusions from Sites with Rainwater Harvesting   14  4.2 Works Yards         14   4.2.1 Manitoba Works Yard       14   4.2.2 Evans Works Yard       16   4.2.3 Conclusions from the Works Yards     17  5.0 Feasibility          18  6.0 Recommendations        24  7.0 Conclusion         25  8.0 Works Cited         26  3  Executive Summary  In the Greenest City 2020 Action Plan, the City of Vancouver has set the goal of reducing the City’s per capita water consumption by 33% from its 2006 consumption rate.  This paper highlights an opportunity where the City itself can reduce water consumption. This paper looks at how the City can implement rainwater harvesting at its Work Yards, in particular the Manitoba and the Evans Works Yards. The findings of this research could then be applied to other works yards throughout Vancouver. The research was divided into three main parts, which included a literature review and site tours of the VanDusen Visitor Centre and the Creekside Community Centre which informed the best practices for rainwater harvesting. The second part included site tours of the Manitoba and Evans Works Yards to determine the opportunities for rainwater harvesting at these sites. The third and final part discusses how much water can be collected and the associated savings that accompany its collection. The research conducted has led to the following recommendations for the City of Vancouver’s Works Yards:  Implement water metering on the hoses used for non-potable operations  Use harvested rainwater  for outdoor non-potable purposes: vehicle washing, irrigation and street cleaning  Thorough design review to ensure all system components are cohesive, as well as talking to maintenance technicians during the design process  Hire dedicated individuals for post installation maintenance  External system with an above ground tank   4  1.0 Introduction  The City of Vancouver, through their Greenest City 2020 Action Plan, hopes to reduce per capita water consumption by 33% from the 2006 levels (City of Vancouver 53). By 2012 the city managed to reduce consumption per capita from 583 L/person/day in 2006 to 491 L/person/day which represented a reduction of 16% (City of Vancouver 34). This feat was accomplished through seasonal water utility rates and the enforcement of lawn sprinkling regulations (City of Vancouver 35). In order to keep up this success the City itself will have to look to its own facilities to reduce its water consumption along with it citizens. The research question addresses this exact concept. In particular the research looks at the opportunities for and the feasibility of rainwater harvesting (RWH) at city works yards. In particular research focused on the Manitoba and the Evans Works Yard. The methods used to address the research question consisted of a literature review and expert site tours of city facilities with existing RWH systems as well as tours of the works yards. 1.1 What is Rainwater Harvesting?  Rainwater harvesting has been practiced for centuries in various societies across the world (Krishna 1). There has been archeological evidence of rainwater harvesting that dates as far back as 4000 years ago (Krishna 1). The concept of rainwater harvesting is quite simple. A RWH system consists of collecting water from a roof also known as the catchment surface that has been piped to a storage tank (Oregon 1)(refer to Fig.1; Krishna 5). The collected water can then be used for both indoor and outdoor purposes.   5   Harvested rainwater has the potential to be used for potable and non-potable purposes. Potable water is water that is safe to drink and meets Health Canada’s Guidelines for Canadian Drinking Water Quality (Regional District of Nanaimo 15), while non-potable water is water that is not for consumption. Non-potable water uses include irrigation, outdoor cleaning, vehicle washing, filling pools and hot tubs and toilet flushing (Regional District of Nanaimo 10). Potable water uses include drinking water, household laundry, bathing, cooking and dishwashing (Regional District of Nanaimo 15). Although rainwater can technically be used for both potable and non-potable uses, it is much simpler to use this water for non-potable purposes because it does not require purifying water to water quality standards. Restricting rainwater for non-potable uses also lessens the chance of negative human health impacts which will be discussed in further detail. 1.2 Rainwater Harvesting Benefits  There are several benefits associated with collecting rainwater. This includes both economic and environmental benefits. The most obvious economic benefit is that rainwater is free (Krishna 1). Collecting rainwater allows for an on-site water source. This removes the need for constructing a complicated distribution system (Krishna 1) and thus reduces construction costs and reduces the amount of energy required to transport the water as well. Using rainwater also reduces equipment maintenance costs this is because rainwater is soft (Lawson et al 17; Krishna 1). Soft water is water devoid of minerals. Due to this low mineral content there is less Fig.1: A Basic Rainwater Harvesting System  6  scale build up on appliances which can extend their use (Krishna 1). Harvesting rainwater can also provide a secondary water source if City water becomes limited (Krishna 1).  Storm water management is a major benefit of rainwater harvesting for both economic and environmental reasons. The first impact being that rainwater collection reduces storm water runoff (Krishna 1) and reduces the water load on storm water infrastructure, which again reduces City maintenance costs. The City is currently transitioning their combined sewer system into a sewage and rainwater separated system by the year 2050 (City of Vancouver). This means that sewage as well as rainwater is sent to a treatment facility. Due to this at some treatment facilities heavy rainfall can overwhelm the system and lead to sewage overflow (Lawson et al 16).  Reducing rainwater runoff can lessen the chance of overflow and thus the contamination of local waterways (Lawson et al 16). As rainwater flows across a landscape it can carry pollutants such as bacteria, chemicals, metals, pesticides, trash and nitrogen and phosphorus from fertilizers into nearby aquatic ecosystems (Lawson et al 13; Krishna 1). These pollutants can then contaminate waterways and negatively impact native aquatic plants and animals (Lawson et al 13). By diverting rainwater to a harvesting system it could decrease the pollution that flows into the environment. The Virginia Rainwater Harvesting Manual states that categorizing rainwater as sewage “is unnecessary, wastes resources, and causes unnecessary pollution” (Lawson et al 16).  Finally there is a social benefit to rainwater harvesting. If the City were to implement rainwater harvesting at its facilities it could lead to a “trickle-down” effect and inspire other individuals, companies, and organisations to become more environmentally aware when making environmental, political and economic decisions (Lawson et al 17).  7  2.0 Methods  Research was conducted through literature review and primary research, which consisted of tours of various city facilities. Literature was used to draw recommendations on the materials that should be used and best practices to optimize the efficiency and harvesting potential of a rainwater harvesting system. Primary research consisted of site tours at the Creekside Community Centre and the VanDusen Visitor Centre. Rainwater harvesting is already occurring at these sites and provided a good overview of what has made these sites successful and what problems have had to be mitigated. Two other site tours were taken at the Manitoba Works Yard and the Evans Works Yard. These tours provided insight into the opportunities for rainwater harvesting at these sites as well as how much infrastructure was available for harvesting purposes. Literature Review Catchment Surface  The catchment surface of any RWH system can determine just how much water can be collected overall if there is in fact an unlimited amount of space for a storage tank. For every square metre of catchment area a litre of rainwater can be captured per millimetre of rainfall (Despins 4). An interesting fact to point out is that rain water harvesting systems can only successfully capture about 75% of the water that falls on a catchment surface (Oregon 4). This is largely due to evaporation and leaks throughout the system. The harvesting potential of a catchment surface can be greatly impacted by the material chosen for the roof. A general rule for the roofing material is “the smoother the better” (Krishna 6).  8   It is for this reason that metal is the most recommended material to use for a catchment surface. Metal roofs are smoother and have a higher runoff coefficient (Lawson et al 22). The most common type of metal used for rainwater harvest catchment is Galvalume which is 55% aluminum and 45% zinc alloy coated sheet steel (Krishna 6). The only instance when metal roofs are not an ideal choice is if they have copper or lead components because they can leech and lessen the quality of the water (Lawson et al 22). Due to the contamination potential of metal roofs with copper or lead components it is recommended that these roof types not be used for potable uses, fruit/vegetable gardening or for the filling of pools (Lawson et al 22). Green roofs, while great in other circumstances, are not an ideal selection for a rainwater harvest system if the primary goal is to capture as much water as possible, due to their absorptive nature. On average a soil base roof will allow for only a 10 to 20% collection of runoff and a gravel base green roof will result in 30% collection of runoff (Lawson et al 31).   A study of how roof type impacted water quantity and quality was conducted at a university campus in Barcelona. The researchers studied 4 different roof types which included clay tiles, metal sheet, polycarbonate plastic and a flat gravel roof. The runoff of each roof type was monitored over a two year period from 2008 to 2010 (Farreny et al 3245). The researchers collected and measured rainwater and then used statistical analysis to determine the amount of runoff generated by each roof type. It was found that metal and plastic roofs encouraged the most runoff while a flat gravel roof performed the worst since it was flat and porous which led to water retention. To be specific the sloping metal and plastic roofs presented a rainwater harvesting potential that was 50% greater than the flat gravel roof (Farenny et al 3253). At Evans work yard there are smaller metal roofs that could be used for this purpose. Ferreny et al do comment that roofs with a low runoff coefficient are still beneficial in the sense that they can 9  reduce the peak flow and minimize the potential for overflows in combined sewer systems (3253). 3.2 Cistern  The cistern in a rainwater harvesting system is possibly the most important part of a system when discussing whether the implementation of such a system is feasible. This is in fact because the storage tank is the largest cost of a harvesting system (Sisolak & Spataro 51, Krishna 10). As such great care must be taken when determining the size of a storage tank.  There are many factors that should be considered when determining the size of a cistern. These variables include the amount of precipitation received, the demand for the harvested water, the projected period of time without rain, and the size of the catchment surface. A storage receptacle should be large enough that there will not be a loss of water due to overflow during peak rainfall season and should also be large enough that it may support future demand (Oregon 6). If overflow is expected or should happen this water could be connected to a line that diverts the overflow to a rain garden or an area where infiltration can occur (Sisolak & Spataro 47).  In a case study from the UK, written by Ward, Memon, and Butler, the importance of choosing an appropriate tank size is exemplified. An office building was monitored for an eight month period from December 2008 to July 2009 (Ward et al 5129). The system was designed for a permanent occupancy of 300 people along with additional transient occupants (5130). In reality only 111 people occupy the building permanently and thus the system was designed too large (5129).  The actual tank used in the system was sized to a volume of 25m3 and had a capital cost of £15, 500 (5133). It was calculated that the payback period for this tank was 10.5 years (5133). 10  The hypothetical tank was sized to accommodate the actual permanent occupancy of the building at 111 people. The tank size needed to support this population was calculated to be 9m3 with a capital cost value of £9 000 (5133). The hypothetical tank was calculated to have a payback period of 6 years. As can be seen from this example the savings potential of the system was set back four years and an extra £6500 on the oversized cistern. Due to the lack of foresight the project lost some of its economic value.  This example clearly illustrates just how important it will be for the city to determine a suitable tank size. This can ultimately determine the feasibility of the project. If the tank size chosen is far too large the city will have to wait a significantly longer period of time to reap the economic benefits of the system.  3.3 Filtration/Purification  Water is “one of the most powerful solvents” (Abbasi & Abbasi 2098). Due to this water can take in portions of any substance it comes into contact with; this includes particulates, colloids and solutes (Abbasi & Abbasi 2098). Since the harvested rain water will most likely be used for non-potable uses, RWH systems typically do not need a form of disinfection prior to use (Regional District of Nanaimo 61). Despite this, water quality should still be of concern in a system used exclusively for non-potable purposes because there is a chance of exposure to micro-organisms in an aerosol form that can result from toilet flushing, irrigation and the use of high pressure hoses for cleaning (Oesterholt et al 171).  An important part of rainwater harvesting that should be implemented is first-flush diversion. First-flush is run-off at the start of a precipitation event. The first-flush can rinse the roof and allow for the collection of cleaner water as the rain continues (Lawson et al 28). It is 11  recommended that this initial run-off should be discarded to attain the cleanest water possible. A minimum of 38 L of rainwater should be diverted for every 93 m2 of catchment area (Mendez et al 2051). This initial run-off should be diverted away from the storage tank.     A simple first flush diversion system involves a horizontal pipe that fills with the initial run-off when it begins to rain. In the pipe there is a plastic ball as the ball rises with the water level it will stop flow to the diverter and allow the rest of the run-off to flow into the cistern (refer to Fig. 2; Oregon 9).  In another study water samples were collected and the physical, chemical and bacteriological characteristics for each sample collected was analyzed (May & Prado 147). The samples were gathered from an experimental harvest system. Through analysis it was discovered that when the samples were compared to water reuse guidelines outlined by the United States Environmental Protection Agency, the samples “did not meet all required standards” (May & Prado148). It should be noted that the harvested water was being used for toilet flushing since this water has the potential to come into contact with humans there is the possibility that there are higher standards equated to it than what might be expected the city yards where water may be used to clean equipment. Fig. 2: Simple First Flush Diverter 12   There are various water treatment options that the city could possibly use and some of them are chlorination and UV light (Krishna 25). For chlorination about a ¼ cup of pure chlorine has to be added per 3700 L of collected rain water in order to disinfect properly (Krishna 25). Chlorine is the easiest and cheapest method of purification (Harvey, 2014). Despite these benefits it is difficult to evaluate how much chlorine should be used in a storage tank since the levels are constantly fluctuating (Hansen, 2014). A UV lamp may be a better solution and according to research UV treatment is preferred because “it does not leave chemical residuals in the water” (Oregon 14). This process allows for the removal of microorganisms (Sisolak & Spataro 48), this includes bacteria, virus and cysts (Krishna 25). A downside of UV treatment is that the lamps do require energy (Sisolak & Spataro 48) and the bulbs will need to be replaced (Krishna 26) but it is considered “compact and efficient” (Sisolak & Spataro 48).  Aside from the human health benefits associated with filtration and purification, there are financial benefits as well. By implementing these types of measures contaminant buildup and bacterial growth can be reduced in the tank which would lead to a reduction in the frequency of tank cleaning (Regional District of Nanaimo 42). One source notes that purification techniques could reduce the frequency of annual cleaning to as little as once for every 15 years (Regional District of Nanaimo 42).  3.4 Other Sources of Water Loss  Aside from the roof material there are several other factors that could lead to an inefficient rainwater harvest system. Overhanging branches and the presence of wind can act as a barrier to prevent water from falling onto a catchment surface (Regional District of Nanaimo 22). The issue of overhanging branches will most likely not be an issue at the City’s work yards 13  because the areas they are located are significantly industrialized with little surrounding vegetation. Losses can also be a result of overflow and spills from improperly sized pipes, tanks and inefficient filters (Regional District of Nanaimo 22). These issues can be mitigated, as explained when discussing storage tanks careful consideration needs to be taken when choosing the appropriate size of a component. In order to do this the long term operation of the system should be considered in the design process. This should include anticipating changes in climate and possibly changes to the surrounding area as a result of development.  4.0 Interviews/Site Tours 4.1 Sites with Rainwater Harvesting 4.1.1 Creekside Community Centre   The first site tour as at Creekside Community Centre and was conducted was with Ian Harvey, the Manager of Building Operations for the City of Vancouver, and Alex Hansen, the Maintenance Technician for Creekside. This site tour provided a general idea of how an above-ground rainwater harvesting system functions.   At this site the catchment surface is a green roof as discussed above green roofs are not the best choice in terms of the quantity that is collected; however the harvested water at this site is primarily used for toilet flushing. There are three above ground tanks at this site. Each tank has two openings, one on the top and one on the side. By having two openings tank maintenance such as cleaning is made a great deal easier.   There have been a few issues at this site in terms of design. A significant issue at this site is how the system is connected to the City’s water supply. Alex Hansen was able to describe this process. If the water in the tanks were to drop below a third of the tanks capacity the system 14  becomes connected to the City supply (Hansen 2014). The city water must first flow into the harvesting tank and is then redistributed throughout the building (Hansen 2014). The water of course loses all energy when flowing into the harvesting tank and then requires energy to be pumped throughout the building. This is an inefficient use of energy and not economically practical.   A key point that Ian Harvey reiterated while at this site was the notion that “you can’t overthink the design” (Harvey 2014). This was in response to the issues that have occurred due to a lack of a “holistic vision” (Harvey 2014). This includes such things as the impractical connection to the City water supply. To mitigate these issues Ian suggested that a design review should take place. By doing this each person involved in the project can come together and ensure that all pieces of the system will work in harmony with one another and any potential system flaws can be identified and corrected prior to construction. This could in fact lower costs in the long run by addressing problems before they even occur. 4.1.2 VanDusen Visitor Centre  The second site tour was at the VanDusen visitor centre and was conducted with Ian Harvey and William Lee, the maintenance technician of VanDusen. The harvested water at this site is used for toilet flushing and is then sterilized and recycled to be used in irrigation. Unlike Creekside, there is a single below ground storage tank and the catchment surface is a basic asphalt mat. The connection to the City water supply is also much simpler than at Creekside. At VanDusen when the water runs low in the cistern a sensor within the tank and signals that a valve be turned on to connect the building directly to City water. This is much more energy efficient than how the Creekside Community Centre is connected to city water.  15  4.1.3 Conclusions from Sites with Rainwater Harvesting  A theme that Ian Harvey stressed at both the Creekside Community Centre and the VanDusen Visitor Centre is the importance of people. He commented that to reach the design intent of a harvesting system can possibly take years (Harvey 2014). This is due to presence of technical issues and the changing demands of the system, such as seasonal variation. This issue can be directly applied to the work yards as well despite the fact that the water will be used for outdoor purposes and does not depend on occupancy. Water demand at the yards will change throughout the year because all equipment is not used year round and will have peak times when it is in fact used. For example watering trucks will have a higher water demand in the spring and summer. Due to this period of working the kinks out of the system any project requires maintenance technicians such as Alex Hansen and William Lee who ensure that the system is functioning and that it will continue to function years into the future. It should also be noted that it is important to talk to maintenance technicians during the design process since they can provide valuable information on how any system can be improved through their own first hand experience. 4.2 Works Yards 4.2.1 Manitoba Works Yard   This site houses recycle, litter and garbage trucks as well as street sweepers and flushers. The central stores building, which has a surface area of 4000 m2, and the small equipment shelter, which has a surface area of  1071 m2, are available to be used as a catchment surface (refer to Map 1). The roofs are a basic roll on asphalt mat.  The Anonymous Interview Informant suggested that a harvesting tank could be placed near the Wash Rack (refer to Map 1); however 16  since the site does not meter its water use it is not clear whether these locations are large enough to house the size of tanks needed to meet the non-potable water needs at this site.   At this site there is a Wash Rack where the garbage trucks are rinsed out. City drinking water is currently being used for this purpose and this is a potential place in which harvested rainwater could be used. Water does not need to be purified to the drinking water standard if it is simply being used to rinse out garbage trucks and wash City service vehicles. The street sweepers and flushers are other operations that could potentially use harvested rainwater. The sweepers use approximately 200 to 300 gallons or 757 to 1135 litres of water per 8 hour shift (Anonymous Interview Informant, 2014). There are 2 sweepers on nights and 2 sweepers on during days, this occurs 5 days a week. During the Leaf Program the number of sweepers is increased to 12. The sweepers tend to focus on the downtown core and cleaning off the bridges Map 1: Manitoba Works Yard Possible Tank Location Wash Rack 17  that lead into the city. The street flushers are larger and can hold about 2000 gallons or 7570 litres of water. These machines are only typically used for clean up after emergencies such as car accidents. In the summers the flushers are used once a week to clean the downtown east side. They are also used to water new boulevard grass until it begins to establish. 4.2.2 Evans Works Yard  The site tour at Evans Works Yard was conducted with Ian Harvey as well. Evans is home to the Parks Board and Real Estate and Facilities Management. At Evans there are several low level galvanized metal roofs, which have a total surface area of 1444 m2, that could serve as catchment site (Harvey 2014) (refer to Map 2). These low level roofs also have external piping which could be easily connected to a cistern for collection. Service vehicles are washed here as well. This site includes grass cutting equipment rather than garbage trucks. At this location there are watering trucks used for various horticulture throughout the city. Again at this site, like Manitoba, potable water is used for non-potable purposes. Rainwater could be used for the washing of vehicles, such as the grass cutting equipment, at this site and also used to fill the watering trucks much like the sweepers and flushers. 18   4.2.3 Conclusions from the Works Yards   It was found from these tours that the city currently does not meter the water consumption at the yards. The main obstacle for installing a rainwater system at either site is space availability. As discussed, tanks can either be installed above ground or below ground. A below ground tank has the potential to be larger however the costs of installation will be greater because the ground will have to be excavated. Maintenance in a below ground tank is also an issue because the tank is not as easily accessible.  At the various site tours Ian Harvey noted that if harvested rainwater were to be used for in an aerosol form there would need to be some form of purification. The water sprayed from a hose, as is the case for washing vehicles, is considered to be an aerosol form of water and has the potential to be breathed in and has the possibility to be a health hazard. Chlorine is the most basic solution for purification, since it is relatively cheap and easy to administer (Harvey 2014) but according to Alex Hansen this can be difficult because the level of water within the tanks is Map 2: Evans Works Yard 19  constantly changing and it becomes difficult to know just how much chlorine should be added to the tank at any given tank. Another solution would be to install a UV lamp within the storage tank (Harvey, 2014).   According to this research it is clear that the lower level metal roofs found at Evans work yard are would make an ideal catchment surface. The roofs available for catchment at Manitoba are not ideal for harvesting the largest quantity of rainwater but as mentioned they can be beneficial in reducing the stress on Vancouver’s combined sewer system. This in turn could lead to additional savings for the city through reducing the volume through the sewer system which could reduce the maintenance requirements and costs for the sewer system. 5.0 Feasibility  Determining an overall cost for a rainwater harvesting system cannot be completed during this research. This is a result of the work yards not metering their current water consumption for the various non-potable operations that occur at these sites. There is simply no way to determine how large of a tank the system would need to accommodate the water used on site. Due to this it is also unclear if the available catchment surfaces will provide enough water to supply the tank sizes that would be needed to meet the City’s needs at the work yards.  Despite this it was possible to determine a rough estimate of how much water could be collected as well as the associated economic savings at Manitoba and Evans work yard. These values were calculated using a simple equation outlined in the Regional District of Nanaimo’s harvesting guidebook (refer to Fig. 3). Potential water savings were calculated first and this was then used to calculate the actual water savings. Potential water savings can be defined as the total amount of rainwater that lands on a roof surface. Potential water savings is the amount that could 20  be collected if 100 percent of the water that lands on a catchment surface could in fact be collected. This is however not possible, only about 75% (Oregon 4) of the rainwater that falls on a roof can be collected. The definition of actual water savings is the amount of rainwater that can actually be collected and takes into account roof texture.  Fig. 3: Regional District of Nanaimo Equations for Water Collection Potential Potential Water Collection  Actual Water Collection: The collection efficiency used was 75%   For the city of Vancouver the metered water rates are as follows $2.385 per unit1 for the period of October 1st t to May 31st and $2.988 for the period of June 1st to September 30th (City of Vancouver). VanMap was consulted to determine the area of possible catchment surfaces. The monthly precipitation data was gathered from the World Weather Information Service which has averaged temperatures for the time period of 1971-2000.  The anonymous interview informant at Manitoba suggested that the entire central stores roof and the roof of the small equipment shelter could be used as a catchment surface. These                                                           1 1 unit=2, 831.6 L 21  surfaces combined could potentially collect 4, 560, 857 L of rainwater annually which equates to an economic saving of $3992.97 (refer to table 1-2.2).    22     While at Evans Work Yard Ian Harvey suggested that the smaller low level metal roofs would make an ideal catchment surface this is of course backed up by the research that 23  comments that metal is the ideal choice for rainwater harvesting. The low level roofs could potentially harvest 1, 298, 733.60 L of rainwater per year and result in an economic savings of $1, 137.02 (refer to table 3-3.2).   Table 3.2: Estimated Economic Savings:   Actual Water Savings (L) Number of Units (1 unit=2831.6 L) Rate Per Unit ($) Savings Per Month ($) January 166348.8 58.75 2.385 140.11 February 133317.3 47.08 2.385 112.29 March 123786.9 43.72 2.385 104.26 April 90972 32.13 2.385 76.62 May 73535.7 25.97 2.385 61.94 June 59348.4 20.96 2.988 62.63 July 42886.8 15.15 2.988 45.26 August 42345.3 14.95 2.988 44.68 September 57940.5 20.46 2.988 61.14 October 121945.8 43.07 2.385 102.71 November 196023 69.23 2.385 165.11 December 190283.1 67.20 2.385 160.27        Annual Economic Savings=$1, 137.02 24   If Evans were to incorporate the main roof as well they could potentially harvest an additional 3, 601, 197 L annually and save $3152.80 (refer to table 4-4.2). As mentioned these are rough estimates and further in depth calculations could make these estimates more accurate.  Table 4.2: Estimated Economic Savings:   Actual Water Savings (L) Number of Units (1 unit=2831.6 L) Rate Per Unit ($) Savings Per Month ($) January 461260.8 162.90 2.385 388.51 February 369669.3 130.55 2.385 311.37 March 343242.9 121.22 2.385 289.11 April 252252 89.08 2.385 212.47 May 203903.7 72.01 2.385 171.74 June 164564.4 58.12 2.988 173.65 July 118918.8 42.00 2.988 125.49 August 117417.3 41.47 2.988 123.90 September 160660.5 56.74 2.988 169.53 October 338137.8 119.42 2.385 284.81 November 543543 191.96 2.385 457.82 December 527627.1 186.34 2.385 444.41        Annual Economic Savings=$3152.80 25   Based on the information gathered at Manitoba it was possible to calculate approximately how much water is used for street sweeping each year. The streets sweepers range in size from 757 to 1135 L and a total of four are used each day, five days a week. From this information it was found that the city currently uses somewhere between 787, 365.28 L to 1, 181, 047.92 L (refer to table 5) of City drinking water to clean the streets of Vancouver during the year. This substantial amount could be replaced with harvested rainwater. By switching to harvested rainwater the City could potentially save between $719.07 to $1078.61 each year (refer to table 5.2-5.3). Table 5: Estimated Water Use for Street Sweepers Sweeper Volume (gal) Gallons to Litres Litres L per Day L per Week L per Year 200 3.78541 757.082 3028.328 15141.64 787365.28 300 3.78541 1135.623 4542.492 22712.46 1181047.92  Table 5.2: Water Savings for One Year if All Sweepers held 757 L  Water Use per Month Number of units Rate per Unit Savings per Month ($) January 65613.77 23.17 2.39 55.27 February 65613.77 23.17 2.39 55.27 March 65613.77 23.17 2.39 55.27 April 65613.77 23.17 2.39 55.27 May 65613.77 23.17 2.39 55.27 June 65613.77 23.17 2.99 69.24 July 65613.77 23.17 2.99 69.24 August 65613.77 23.17 2.99 69.24 September 65613.77 23.17 2.99 69.24 October 65613.77 23.17 2.39 55.27 November 65613.77 23.17 2.39 55.27 December 65613.77 23.17 2.39 55.27             Annual Economic Savings=$ 719.07   26  Table 5.3: Water Savings for One Year if All Sweepers held 1135 L  Water Use per Month Number of units Rate per Unit Savings per Month ($) January 98420.66 34.76 2.385 82.90 February 98420.66 34.76 2.385 82.90 March 98420.66 34.76 2.385 82.90 April 98420.66 34.76 2.385 82.90 May 98420.66 34.76 2.385 82.90 June 98420.66 34.76 2.988 103.86 July 98420.66 34.76 2.988 103.86 August 98420.66 34.76 2.988 103.86 September 98420.66 34.76 2.988 103.86 October 98420.66 34.76 2.385 82.90 November 98420.66 34.76 2.385 82.90 December 98420.66 34.76 2.385 82.90             Annual Economic Savings=$ 1078.61 6.0 Recommendations  The most important recommendation is that the city should meter the water consumption of the work yards. Without a clear idea of how much water is used on site it is impossible to determine how large of a storage tank or if the demand is great enough at these sites to implement a RWH system. Another issue to point out is that the City hopes to reduce per capita water consumption by 33% in their Greenest City 2020 Action plan. If there is no knowledge of how much water is used initially then it is also not possible to know just how much or if consumption has in fact been cut down if at all. Water consumption at the yards should be monitored for at least a year. This period of time will show how demand changes throughout the seasons.   The city should also look to have a design review process prior to the construction of the system. By having a thorough design review process issues such as the flawed connection to City water at Creekside could be avoided. This could enhance the feasibility of the entire system by addressing design flaws before they become full scale problems. During the design process 27  maintenance technicians should be consulted as well to learn the degree of maintenance the system will require and to provide insight about how the system could be improved. This is clear from the abundance of information provided at the site tours of the Creekside Community Centre and the VanDusen Visitor Centre. The system should be primarily external. This is because the yards have pre-existing structures and trying to connect to internal plumbing will induce greater costs and complications. This includes the use of an above ground storage tank which will eliminate the costs associated with excavation. Once a design has been decided upon the city should hire individuals who will be committed to ensuring the system’s success post installation. Finally the city should use harvested rainwater for street cleaning, irrigation and vehicle washing. These recommendations could be applied to any work yard across the city of Vancouver. 7.0 Conclusion  The city should look to implement rainwater harvesting at the work yards. As has been presented there is an abundance of opportunities for harvested rainwater at these sites and a substantial amount of savings could be achieved. By implementing RWH system at city work yards the city can lead by example and guide its citizens towards more sustainable water practices. The city will also display its commitment to the Greenest City 2020 Action Plan and maintain its standing as a leader in sustainability.      28  Works Cited Abbasi, T, and SA Abbasi. "Sources of Pollution in Rooftop Rainwater Harvesting Systems and Their Control." Critical Reviews in Environmental Science and Technology. 41.23 (2011): 2097-2167. Print. Anonymous Interview Informant (March 20 2014). Manitoba Works Yard: Informational Interview. City of Vancouver. Greenest City 2020 Action Plan. Vancouver: Hemlock Printers, 2012. Print. City of Vancouver. Greenest City 2020 Action Plan: 2012-2013 Implementation Update. Vancouver: Hemlock Printers, 2013. Print. City of Vancouver (03 Jan 2014). Metered Utility Rates. Retrieved from City of Vancouver (15 March 2014). Separating Sewage From Rainwater. Retrieved from Despins, C. Canada. Canada Mortgage and Housing Corporation. Guidelines for Residential Rainwater Harvesting Systems Handbook. 2012. Print.  Farreny, Ramon, Tito Morales-Pinzon, Albert Guisasola, Carlota Taya, Joan Rieradevall and Xavier Gabarrell. "Roof selection for rainwater harvesting: Quantity and quality assessments in Spain." Water Research. 45.10 (2011): 3245-3254. Print. Hansen, Alex (February 28 2014). Informational Interview: Maintenance Technician of Creekside Community Centre. City of Vancouver.  29  Harvey, Ian  (February 28, March 7 & 24 2014). Informational Interview: Manager of Building Operations. City of Vancouver. Krishna, Hari J. Texas. Texas Water Development Board.Texas Manual on Rainwater Harvesting. 2005. Print. Lawson, Sarah, Adrienne LaBranche-Tucker, Hans Otto-Wack, Rick Hall, Benjamin Sojka, Ed Crawford, David Crawford, and Cabell Brand. “Virginia  Rainwater Harvesting Manual”.The Cabell Brand Center. Virginia . Salem, Virginia: 2009. Print Lee, William (March 7 2014). Informational Interview: Maintenance Technician of VanDusen Visitor Centre. City of Vancouver. May, S, and R Prado. "Experimental evaluation of rainwater quality for nonpotable applications in the city of São Paulo, Brazil." Urban Water Journal. 3.3 (2007): 145-151. Print Mendez, C, J. Brandon Klenzendorf, Brigit R. Afshar, Mark T. Simmons, Michael E. Barrett, Kerry A. Kinney and Mary Jo Kirisits. "The effect of roofing material on the quality of harvested rainwater." Water Research. 45.5 (2011): 2049-2059. Print. Oesterholt, Frank, Gerard Martijnse, Gertjan Medema and Dick van der Kooij. "Health risk assessment of non-potable domestic water supplies in the Netherlands." Journal of Water Supply: Research and Technology. 56.3 (2007): 171-179. Print. Oregon. Department of Consumer & Business Services:Building Codes Division. Oregon Smart Guide: Rainwater Harvesting. Salem:Print. Regional District of Nanaimo. Regional District of Nanaimo.Rainwater Harvesting Best Practices Guidebook. Nanaimo: 2012. Print. 30  Sisolak, Joel, and Kate Spataro. Cascadia Green Building Council. Toward Net Zero Water: Best Management Practices for Decentralized Sourcing and Treatment. 2011. Print. Ward, S, F. A. Memon, and D. Butler, "Performance of a large building rainwater harvesting system." Water Research. 46.16 (2012): 5127-5134. Print World Weather Information Service (March 2014). Vancouver, British Columbia. Retrieved from  


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