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Benefits of installing additional rain sensors within the UBC irrigation system : a business case analysis Thiessen, Michael; Drysdale, Chelsie 2013

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UBC Social Ecological Economic Development Studies (SEEDS) Student Report       Benefits of Installing Additional Rain Sensors within the UBC Irrigation System Michael Thiessen, Chelsie Drysdale  University of British Columbia CHBE 484 April 20, 2013           Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report”.   1         Benefits of Installing Additional Rain Sensors within the UBC Irrigation System A Business Case Analysis    Prepared for: Dr. Tony Bi, CHBE 484 & UBC SEEDS office    Submitted by: Michael Thiessen  Chelsie Drysdale  Winter 2013  2  Table of Contents LIST OF TABLES ...................................................................................................................................................... 3 LIST OF FIGURES .................................................................................................................................................... 3 EXECUTIVE SUMMARY ......................................................................................................................................... 3 INTRODUCTION ...................................................................................................................................................... 5 OBJECTIVE ................................................................................................................................................................................ 5 SCOPE OF REPORT ................................................................................................................................................................... 5 DESCRIPTION OF CURRENT UBC IRRIGATION WATER USE .............................................................................................. 6 RAIN SENSOR BACKGROUND ................................................................................................................................................. 7 DATA ANALYSIS ...................................................................................................................................................... 8 WATER USAGE ......................................................................................................................................................................... 8 ECONOMICAL ANALYSIS ......................................................................................................................................................... 9 CONCLUSION AND RECOMMENDATIONS .................................................................................................... 10 APPENDIX A: DATA ............................................................................................................................................ 13 APPENDIX B: MAP ............................................................................................................................................... 16 APPENDIX C: SAMPLE CALCULATIONS ........................................................................................................ 17 APPENDIX D: REFERENCES .............................................................................................................................. 19      3 List of Tables Table 1: Critical Areas calculated for rain sensor installation with a 10 year return period .. 9 Table 2: Current and projected water prices as shown in the UBC Irrigation Action Plan (Stantec, 2012) .................................................................................................................................................... 13 Table 3: Calculated water usage values for lawns and beds and timed and rain sensored plots ......................................................................................................................................................................... 13 Table 4: Projected economic analysis for a plot of lawn with 84% savings ................................ 14 Table 5: Projected economic analysis for a bed with 84% savings ................................................ 14 Table 6: Projected economic analysis for a plot of lawn with 15% savings ................................ 15 Table 7: Projected economic analysis of a bed with 15% savings .................................................. 15  List of Figures Figure 1: Current UBC water use patern ...................................................................................................... 6 Figure 2: Water sensor currently in use at UBC ........................................................................................ 7 Figure 3: Rock garden at Westbrook Mall and Thunderbird; no irrigation required ............. 11 Figure 4: Map of campus irrigated areas…………………...……………………………………………………16    4 Executive Summary  Analysis of the irrigation data available indicates that rain sensors save 84% of the water used and are therefore economically viable on a plot of lawn of 260 sq. m and a bed of 520 sq. m based on a 10 year return period.  The manufacturer specifies a water savings of 15% which would make rain sensors economically viable on a plot of lawn of 1460 sq. m and a bed of 2920 sq. m based on a 10 year return period.  There is insufficient data to have confidence in the results from the data analysis so more research is required.  If the results of the data analysis are confirmed then this report recommends rain sensors to be installed on all plots larger than the critical area.  Plots smaller than the critical area can be transmogrified into rock gardens to further help achieve UBC’s goal of reducing their irrigation water consumption by 75% by 2020.   5 Introduction  Objective  The main objective of this report was to determine whether or not it would be economically feasible to install additional rain sensors within the UBC irrigation system to reduce the amount of potable water used for irrigation purposes. Specifically, to determine the minimum area of irrigated land that would economically benefit from the installation of a rain sensor.  Scope of Report  This report took into consideration five plots currently on the UBC irrigation grid, three of which are equipped with a rain sensor and two are on a timer. A map of UBC irrigation plots can be seen in Appendix B. Water usage patterns from 2006 to 2012 were used to project water usage for the next decade on a cubic meter water per meter squared basis for lawns and beds. Predicted potable water price inflation information was obtained from the UBC Irrigation Action Plan.    6 Description of current UBC irrigation water use   Irrigation currently makes up approximately 15% of UBC’s total water usage. Potable water currently costs UBC $0.78/cubic meter.  Table 2 presents estimated water prices for the next two years as well as past trends in price increase. UBC currently spends around $500,000 annually on grounds irrigation, this cost encompasses irrigation system maintenance and the cost of potable water used for irrigation. UBC has set a goal of reducing the irrigation water usage by 75% by 2020. This aim is outlined, in detail, in the current UBC irrigation action plan.  Figure 1 represents irrigation’s place in UBC’s overall water consumption (Stantec ,2012).  Figure 1: Current UBC water use pattern     7 Rain Sensor Background  The UBC irrigation system is made up of approximately 140 zones. Each zone operates independently of the others. The UBC irrigation system is responsible for watering 453,000 m3 of lawns and beds. Presently, rain sensors monitor only 167,000 m3 of this total, approximately 36.9%. The irrigation products supplier, Rain Bird, provides the rain sensors currently being used by UBC. Each rain sensor and its corresponding modular timer can be purchased for approximately $118. The use of a contractor is required for installation. Instillation costs are estimated to be around $400 per unit. The typical life span of a rain sensor is between 15 and 25 years.  This report uses a conservative lifespan of 10 years to account for vandalism and other unexpected damages.  Figure 2 shows the bucket style rain sensors currently being used in UBC’s rain sensored areas.    Figure 2: Water sensor currently in use at UBC   8 Data Analysis  Water usage data was collected for five parcels of irrigated land: Triumph house, Rashpal Dhillion track, Wolfson field, the baseball field, and an area near the Angus building.  The data obtained for the Angus building parcel was collected by reading the meter on 13/02/2013 and, when analysed, this data produced a result that was a clear outlier.  The data from the Angus building parcel was not used for further calculation or interpretation.  The Triumph house and Wolfson field parcels’ irrigation systems are controlled by a timer while the Rashpal Dhillion track and baseball field parcels’ irrigation system is controlled by a rain sensor.   Since lawns are watered approximately twice as much as beds, it was necessary to calculate the volume of water used per square meter per year for both lawn and bed areas (see Table 3).  Because the calculation was based on proportionality between water required for lawns and beds, the water savings, in percent, is the same for both.   Water Usage  On average, the water amounts used for lawns were 0.18 m3/m2 yr and 0.03 m3/m2 yr for timed and rain sensored plots respectively.  Beds used 0.09m3/m2 yr and 0.015 m3/m2 yr for timed and rain sensored plots respectively.  The data points used for these calculations agreed well with each other and were all within 1.5 standard deviations of the mean (see Appendix A).  According to this data, rain sensors reduce water usage by 84%. According to literature produced by the manufacturer, rain sensors reduce water usage by 15%.  Due to  9 the large discrepancy between these values, further calculations were completed for both values (see Tables 4-7).  Due to the quality and quantity of data obtained from UBC, some outlying data points had to be eliminated without qualitative explanation of why they were unusual. Plot areas and lawn to bed ratios are not recorded so estimations were made from ARCGIS and employee knowledge.  The estimations used seem to be sufficient based on the agreement between the resulting values.  Economical Analysis A pricing scheme for water used at UBC was obtained from the UBC Irrigation Action Plan (see Table 2).  The prices for future years were calculated based on a $0.07/m3 increase per year. Based on the capital cost to purchase and install a rain sensor and the savings on water usage, a minimum area of lawn and bed was calculated for rain sensor installation to be economically feasible, based on a return period of 10 years (see Table 1). Table 1: Critical Areas calculated for rain sensor installation with a 10 year return period   84% saved 15% saved   Lawn Bed Lawn Bed Area (m2) 260 520 1460 2920  The formuli can be seen in Appendix C; the full calculation can be seen in Tables 4-7.     10 Conclusion and Recommendations  The results in this report were based on limited data and so it is recommended to obtain more robust data before installing rain sensors.  The irrigation water use data currently held by UBC are neither well organized nor complete.  Plot areas and lawn to bed ratios should be measured. Meter readings should be conducted regularly (although annually is sufficient for the purpose of this report). These data should be compiled into one database. The calculations seen in Appendix C can be applied to all plots to determine water usage for beds and lawns. If the results of this report are confirmed for the 84% savings then rain sensors should be installed on all plots larger than the areas indicated in Table 1.  For areas consisting of lawn and bed, the following formula should be satisfied for rain sensors to be economical.                                    For plots that do not satisfy the above equation, other water saving measures can be taken.  Fully or partially replacing an irrigated plot with an attractive rock garden, such as the one found on the Southwest corner of Westbrook Mall and Thunder Bird Boulevard (see figure 3), can reduce or eliminate irrigation needs depending on the degree of coverage of the rocks.  11  Figure 3: Rock garden at Westbrook Mall and Thunderbird; no irrigation required  In addition to the economical benefits, the installation of rain sensors throughout the UBC irrigation system would have several environmental benefits that would significantly contribute to UBC’s sustainability goals. The reduced water usage would decrease UBC’s environmental impact by lowering the university’s energy demands. The energy associated with pumping water to feed UBC’s water supply would be reduced. Additionally, because UBC’s irrigation system is fed from the main potable water supply to the university, the environmental impacts of water treatment would decrease.  Some of these water treatment  12 impacts would include a lowered need for chlorine and UV light to treat the water at the Capilano water treatment plant, where UBC gets its supply of potable water from.  If a rain sensor and timer can be applied to multiple plots it would compound the savings.  This would enable the critical area to be applied to the cumulative area of multiple plots under the control of the same timer and rain sensor.    13 Appendix A: Data  Table 2: Current and projected water prices as shown in the UBC Irrigation Action Plan (Stantec, 2012) Year Water price ($/m3) 2011 0.64 2012 0.71 2013 0.78 2014 0.85 2015 0.92 2016 0.99 2017 1.06 2018 1.13 2019 1.2 2020 1.27 2021 1.34 2022 1.41 2023 1.48 2024 1.55  Table 3: Calculated water usage values for lawns and beds and timed and rain sensored plots  Water used for lawns (m3/ m2 yr) Water used for beds (m3/ m2 yr)   Rashpal Dhillon Track 0.0267 0.0133 Rain Sensored 0.0261 0.0131 0.0361 0.0180 Baseball Field 0.0244 0.0122    Average 0.0283 0.0142 Standard Deviation 0.0053 0.0026      Wolfson Field 0.1716 0.0858 Timed 0.2052 0.1026 Triumph House 0.1603 0.0802 0.1801 0.0901    Average 0.1793 0.0896 Standard Deviation 0.0190 0.0095   14 Table 4: Projected economic analysis for a plot of lawn with 84% savings Lawns with 84% savings              Critical Area (m2) 260                 timer rain sensor    year water price ($/m3) water usage (m3/yr) total cost ($) water usage (m3/yr) total cost ($)  net savings ($) 2014 0.85 46.62 39.62 7.36 6.26  33.36 2015 0.92 46.62 82.51 7.36 13.03  69.48 2016 0.99 46.62 128.66 7.36 20.32  108.33 2017 1.06 46.62 178.07 7.36 28.13  149.94 2018 1.13 46.62 230.75 7.36 36.45  194.30 2019 1.2 46.62 286.68 7.36 45.29  241.40 2020 1.27 46.62 345.89 7.36 54.64  291.25 2021 1.34 46.62 408.35 7.36 64.50  343.85 2022 1.41 46.62 474.08 7.36 74.89  399.19 2023 1.48 46.62 543.07 7.36 85.79  457.28 2024 1.55 46.62 615.32 7.36 97.20   518.12  Table 5: Projected economic analysis for a bed with 84% savings Beds with 84% savings              Critical Area (m2) 520                 timer rain sensor    year water usage (m3/yr) water usage (m3/yr) total cost ($) water usage (m3/yr) total cost ($)  net savings ($) 2014 0.85 46.62 39.62 7.36 6.26  33.36 2015 0.92 46.62 82.51 7.36 13.03  69.48 2016 0.99 46.62 128.66 7.36 20.32  108.33 2017 1.06 46.62 178.07 7.36 28.13  149.94 2018 1.13 46.62 230.75 7.36 36.45  194.30 2019 1.2 46.62 286.68 7.36 45.29  241.40 2020 1.27 46.62 345.89 7.36 54.64  291.25 2021 1.34 46.62 408.35 7.36 64.50  343.85 2022 1.41 46.62 474.08 7.36 74.89  399.19 2023 1.48 46.62 543.07 7.36 85.79  457.28 2024 1.55 46.62 615.32 7.36 97.20   518.12    15  Table 6: Projected economic analysis for a plot of lawn with 15% savings Lawns with 15% savings              Critical Area (m2) 1460                 timer rain sensor    year water usage (m3/yr) water usage (m3/yr) total cost ($) water usage (m3/yr) total cost ($)  net savings ($) 2014 0.85 261.76 222.50 222.50 189.12  33.37 2015 0.92 261.76 463.32 222.50 393.82  69.50 2016 0.99 261.76 722.47 222.50 614.10  108.37 2017 1.06 261.76 999.93 222.50 849.94  149.99 2018 1.13 261.76 1295.73 222.50 1101.37  194.36 2019 1.2 261.76 1609.84 222.50 1368.37  241.48 2020 1.27 261.76 1942.28 222.50 1650.94  291.34 2021 1.34 261.76 2293.04 222.50 1949.09  343.96 2022 1.41 261.76 2662.13 222.50 2262.81  399.32 2023 1.48 261.76 3049.54 222.50 2592.11  457.43 2024 1.55 261.76 3455.27 222.50 2936.98   518.29  Table 7: Projected economic analysis of a bed with 15% savings Beds with 15% savings              Critical Area (m2) 2920                 timer rain sensor    year water usage (m3/yr) water usage (m3/yr) total cost ($) water usage (m3/yr) total cost ($)  net savings ($) 2014 0.85 261.76 222.50 222.50 189.12  33.37 2015 0.92 261.76 463.32 222.50 393.82  69.50 2016 0.99 261.76 722.47 222.50 614.10  108.37 2017 1.06 261.76 999.93 222.50 849.94  149.99 2018 1.13 261.76 1295.73 222.50 1101.37  194.36 2019 1.2 261.76 1609.84 222.50 1368.37  241.48 2020 1.27 261.76 1942.28 222.50 1650.94  291.34 2021 1.34 261.76 2293.04 222.50 1949.09  343.96 2022 1.41 261.76 2662.13 222.50 2262.81  399.32 2023 1.48 261.76 3049.54 222.50 2592.11  457.43 2024 1.55 261.76 3455.27 222.50 2936.98   518.29  16  Appendix B: Map  Due to the size and format of the map (Figure 4), it has been electronically appended as a separate file.   17 Appendix C: Sample Calculations  Water usage per square meter of bed per year Assumption: Lawns are watered twice as much as beds                                     Ubed – Water usage per square meter of bed per year (m3/ m2 yr) Utotal – Total water usage for a plot (m3/ m2 yr) Alawn – Area of plot that is lawn (m2) Abed – Area of plot that is bed (m2) Atotal – Total area of plot (m2)  Water usage per square meter of lawn per year              Ulawn – Water usage per square meter of lawn per year (m3/ m2 yr) Ubed – Water usage per square meter of bed per year (m3/ m2 yr)    18 Net savings (for lawn and bed)                       E – Net savings over n years ($) S – Water savings from using rain sensors (0.83 or 0.15) Pi – Price per cubic meter of water ($/m3) U’i – Water used by a timed plot (m3/m2 yr) A’ – Size of plot (m2) CC – Capital cost ($518) With n=10 years and E=$0, the critical area can be obtained.  This is the minimum area that a rain sensor should be installed on to be economically feasible.     19 Appendix D: References   Hood I., Seabrooke Amy, Stantec, UBC Irrigation Action Plan, February 2012  http://sustain.ubc.ca/campus-initiatives/water/water-action-plan  2010 products catalogue, http://www.rainbird.com. (Retrieved March 2012)  The Intelligent Use of Water: Water-Efficient System Overview, 2009, Rain Bird Corporation  http://sustain.ubc.ca/campus-initiatives/water/water-conservation   

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