The University has numerous athletic fields in its south campus complex. The varsity

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1 Problem Statement The University has numerous athletic fields in its south campus complex. The varsity field hockey stadium is the largest outdoor sports facility on the University s campus. In 1996, a new drainage system was installed and in 2005, the field was upgraded with a brand-new artificial surface, AstroTurf 12, replacing the outdated Astroturf. This field requires up to two irrigations a day, from August through November, to maintain optimal playing conditions. As a result, the field is irrigated using portable water cannons that are connected to the city water supply 1. Thousands of gallons of potable water are used every year to maintain this field for the field hockey team. The south campus complex also contains a large Field House (arena), built in Today, the 9,500 seat arena is mainly a practice facility featuring an indoor field used by many of the University s intercollegiate teams. 2 The circular arena has a large roof area of approximately 97,700 ft 2, leading to significant runoff during rainstorms. The University has had to account for storm water runoff from the arena roof as well as runoff from many other large buildings on campus by building additional reservoirs to hold back the runoff water and release it at a slower controlled rate over a period of time 3. This preventative measure avoids overwhelming the city s combined sewer system. Project Summary/Background The challenge of both storm water capture and potential reuse has been the focus of various studies and numerous projects and has been published in trade and commercial literature. In order to avoid sudden release of rain water at the time of severe storms or to avoid overwhelming combined sewer systems, various preventative actions can be taken. These include increase of bare soil areas, use of landscape forms, rain water collection and storage 1

2 systems, swales, pervious hardscapes, cross drains, and retaining walls. 4 The University utilizes a system of reservoirs to hold back the storm water, for later controlled release. All of the above mentioned methods have been implemented at different scales at recently constructed buildings on the University s campus. Currently, the varsity field hockey field is watered with portable cannons that are hooked up to the municipal water supply. Thus, the usage of potable water can be quite large. One study performed for Princeton University s Bedford Field found that it took 80 minutes and approximately 12,000 gallons of water to saturate an AstroTurf field. This level of watering is necessary prior to all practices and also twice during games to maintain optimal playing conditions. Watering schedules, of course, depend on the weather conditions (drought, etc.), so water usage can vary from week to week. The important challenge is to maintain the optimal moisture levels on the field while conserving as much potable water as possible. 5 Rainwater harvesting from a building s roof is one method used to control water runoff and to prevent sewer systems from being overloaded. Using this approach for the arena building will likely supply a significant portion of the water required to water the adjoining field hockey turf field, since the arena building s roof area is large. Also, this approach will avoid using municipal potable water and instead replace it with the collected rainwater. Relationship to Sustainability The University s Sustainability Division focuses on Energy Systems and Sustainability Management with a mission statement to provide leadership to [the] University and the global community through the identification and promotion of sustainable practices that reduce the University s environmental impact in an economically responsible manner. 6 This project encompasses this ideology by improving not only the sustainability of the University s athletic 2

3 operations, but the surrounding City as well. The proposed project will help reduce the city potable water used by the university and will lessen the demand that the University operations place on the city s combined sewer systems. Environmental tradeoffs to this project should be minimal. The greatest concern will most likely be the additional labor and cost associated with maintenance and upkeep of the rainwater harvesting system. However, elimination of the filtration and disinfection system (not required when the collected water is exclusively used for turf watering) will most likely keep the project attractive for the University. Materials and Methods To gain field information, a successful rainwater harvesting system installed at a University owned building was visited that uses collected rainwater for flushing toilets. The system at this particular building is much smaller than the proposed system for this project, however it provided a basic understanding of how rainwater harvesting works and the components involved. In order to properly size a rainwater harvesting system, first, the possible collection capacity must be determined. The average monthly rainfall for the area was found using weather data from the National Climatic Data Center. The total amount of rainwater that can be harvested (RWH) for each month can be calculated using the following equation. RWH = MR A C C (Equation 1) in, ft 3 ft,gal Where, MR = Monthly rainfall (in) A = 2 Facility roof area ( ft ) C in, ft ft = Conversion factor (0.083 ) C ft 3, gal ft 3 gal = Conversion factor (7.48 ) η = Runoff coefficient in 3

4 These monthly amounts can then be compared to the average monthly water usage to determine if the possible capacity is adequate as a water supply. If the RWH amount exceeds the monthly usage amount, then a sustainable water supply is available. If the RWH amount is less than the monthly usage amount, then not enough rainwater is available and an alternative water supply must also be used. In either case, a backup water source is necessary as a precautionary measure. Members of the project team focused on specific areas of the project work, as follows: Team Leader: System sizing and calculations Team Member #2: System design Team Member #3: Background information and literature survey Results, Evaluation and Demonstration The quantity of water that can be collected from a roof is a function of rainfall, roof area, and roof material. The total area of this domed surface is 97,700 ft 2, however, only the horizontal component of this shape will be considered for the collection of rainwater. In order to determine the possible collection capacity, the roof area of the Field House was first determined. Using an online map distance measuring tool, the diameter of the building was determined to be approximately 336 ft. The area of the roof was determined as follows. 336 ft. A= 2 2 A 88,686 ft 2 Roof material affects the amount of reclaimable water based on texture: smoother surfaces create more runoff. The existing roof system on the Field House is a Sarnafil G410 light grey adhered membrane. A conservative runoff coefficient of 0.80 is appropriate for this type of roof system. 4

5 University personnel estimated that it takes approximately 25 minutes to water the field. During games, this is done twice, once before and once at half time. In addition, the field is watered before every practice. University personnel also estimated that the field is used from the beginning of August until the end of November. Accounting for double practices, games and days off, it is estimated that the field is watered once a day, on average, during this time period. The University does not meter the water for this application so they were unable to estimate how much water is used in each watering. From an article on a similar field, Princeton s Bedford Field, it was estimated that during 80 minutes of watering, approximately 12,000 gallons are dispensed, or at the rate of 150 gal min. The total water (WU) required for a 25 minute watering is determined as follows. WU = 150 gal min 25 min WU = 3,750 gal The monthly water usage can be found by multiplying the WU by the number of days in the month. The table below shows the comparison between the possible collection capacity and the monthly water usage. Period * Average Rainfall (in) Possible Collection Capacity (gal) Monthly Water Usage (gal) August , ,250 September , ,500 October , ,250 November , ,500 Totals ,829, ,500 Table 1: Rainwater Harvesting Comparison * Note: only the four months of the field hockey season are shown in the table. There is potential rainwater harvesting in other months not shown in the table. 5

6 In all months, the possible collection capacity exceeds the monthly water usage. Therefore, the rainwater harvesting system can be used as the primary water source. A backup system to the city water supply should still be in place as a precautionary measure. According to Table 1, a potential 457,500 gallons of city water can be saved as a result of rainwater harvesting. The university pays approximately $ / gal. Therefore, the total annual savings (TAS) was determined as follows. $ TAS = 457,500 gal gal TAS = $2,059 The University can save up to $2,059 annually in city water costs by installing a rainwater harvesting system. Additional benefits resulting from the installation of a rainwater harvesting system include the reduction in demand that the University places on the city s water supply and combined sewer systems. Sewer costs may also decrease because the rainwater will be absorbed by the field and soil. However, these savings depend on the existing draining system in place. There are six major components to a standard rainwater reclamation system 7 : 1. Catchment Surface: surface or roof area from which rainwater is collected for reclamation. 2. Collection Gutters and Downspouts: channels and pipes to transport rainwater from catchment surface to storage. 3. Screens, Filters, and Diverters: devices to remove debris and sediment from reclaimed rainwater prior to storage. 4. Collection Cistern: One or more tanks to store rainwater. 5. Delivery System: feed systems to transport rainwater from collection cistern to end use. 6. Additional Treatment and Purification: end use may require additional treatment and purification systems. No alterations to the Field House roof will be necessary for use as a catchment surface. The current roof drainage system can also be used for rainwater reclamation with minimal alterations. Rainwater runs off the domed roof to drains that line the exterior of the surface, as highlighted (blue) in Figure 1. This water is then channeled to the local sewer system. 6

7 Figure 1: Field House Drainage System For large roof areas it is common to collect rainwater at several points around the building. Based on the current layout of the facility, it is proposed that rainwater be collected and stored at four separate points around the Field House. A downspout will be installed at each point of collection to redirect rainwater from the existing drainage pipes to a collection cistern below. It is important that each downspout is sized to handle the same flows as the current drainage pipes to avoid overflow. Sealed PVC piping is commonly used in this application. A mesh leaf screen must be installed over each roof drain leading to a collection cistern to prevent leaves, insects, and other debris from entering the system. An example of a leaf screen on a roof drain is depicted in Figure 2. Additionally, at least two 45 PVC elbows are necessary to bring the downspout pipe snug to the side of the building. This installation will also require various hardware components such as bolts, brackets, straps, etc. Figure 2: Mesh Leaf Screen over Roof Drain Cover At the bottom of each downspout, a first-flush diverter will be installed to divert the initial flow of water during rainfall away from the storage tank and into the local sever system. This is done to wash away small contaminants, such as dust and pollen that are typically 7

8 collected on the roof. It is recommended that the first-flush diverter remove one to two gallons of rainwater for every 100 ft 2 of collection area before allowing water to reach the cistern. Each first-flush diverter is sized accordingly. After the first-flush diverter, rainwater will be stored in four cisterns, or water storage tanks. The size of a water storage tank is selected based on several factors: amount of collectable rainwater, water demand, projected draught periods, and budget. In typical residential rainwater reclamation systems, tank capacity is selected to match either the annual collectable rainfall or the annual water demand; however, for large institutional buildings, this sizing method would require large, expensive, custom-built water tanks. This is not practical for application at the Field House. It was determined by the project team that the total tank capacity should be capable of storing three weeks (21 days) worth of collectable rainwater. Three weeks of storage is small enough to store onsite at the Field House while still large enough to provide water to supplement the domestic water demand over short draught periods. Four 20,000 gallon water storage tanks will be used to handle this storage. In case of storm conditions, the tank selected must be manufactured with an overflow control mechanism. When the tank is full, excess water entering the tank will be diverted to the local sewer system to avoid flooding the downspouts and roof drains. The type of tank installed is another important design issue. Water storage tanks can be made of concrete, metal, poly/plastic, or fiberglass. Each of these materials has certain advantages and disadvantages, depending on the application. Although fiberglass is relatively expensive, it is corrosion resistant, sturdy, and long-lasting which makes fiberglass tanks a good fit for the Field House system. 8

9 The water will be piped from storage to water cannons that are used to water the fields around the Field House. Without treatment, this water is not potable and cannot be connected to a municipal or private drinking water system. The water will need to be piped directly from the storage tanks to the water cannons without connecting to the existing water system, and therefore needs to be pressurized using small water pumps. Table 2 provides a summary of all equipment that must be purchased and installed in order to fully implement this rainwater collection system. Item Description Unit Price Quantity Total Roof Drain Leaf Screen 20 8 PVC Piping, Coupling, and Hangars PVC Elbow 10 8 Downspout Diverter Kit 50 20,000 gal Fiberglass Storage Tank, 15 6 D, 14 0 H 13,650 ½ HP Water Pump 500 Misc. Hardware 200 Estimated Labor and Burden 65 $ / ea 4 $80 $ / ft 500 $10,500 $ / ea 8 $80 $ / ea 4 $200 $ / ea 4 $54,600 $ / ea 4 $2,000 $ / ea 4 $800 $ / hr 240 ** $15,600 Totals $83,860 Table 2: Implementation Costs Rainwater harvesting systems can be used year round, but are subject to freezing in winter weather. Due to the size of the proposed storage tanks, there is not enough indoor space available to house an indoor system. Anti-freezing tanks are commercially available for such cases, but are considerably more expensive. The water usage is such that the system can be decommissioned, cleaned and drained at the end of the field hockey season to avoid freezing. One drawback of rainwater harvesting is the associated increase in maintenance. These costs may include pump maintenance, pipe and tank cleaning and winterizing the system. ** Estimating installation takes one month 9

10 The project team is scheduled to prepare and exhibit a poster at the April 2013 exhibition event, as required by the sponsors of this student research grant. Subsequent to the event, the poster is planned to be displayed at the University where students and staff can learn about rainwater harvesting and this proposed sustainability project. Conclusions The final results of this project are $2,059 in savings per year and $83,860 in implementation costs. The simple payback is calculated by dividing the annual savings from the implementation cost. $83,860 Simple Payback = $2,059 per year Simple Payback = 40.7 years While the payback period is long, the University may find additional benefits from installing a rainwater harvesting system. A similar system under construction on another campus building is receiving extensive press and praise for installing an innovative green technology, and for contributing to campus and community sustainability. In addition, the calculations and estimates were only made for watering the field hockey turf. There are many other grass fields in the surrounding area that also require watering. Therefore, the system use may be extended beyond the four months of the field hockey season, resulting in further reductions in city water usage. In order to obtain a better estimate of water usage, a survey should be conducted during the field hockey season. Due to the project timeline, this was not feasible. In addition, a survey of the field drainage system should also be conducted. Availability of improved systems that reduce the water required to saturate the field should also be explored. 10

11 Endnotes/References: Information obtained from Pete Sala, Senior Associate Athletics Director for Facility Operations at Syracuse University 4 Slow it. Spread it. Sink it. A Homeowner s Guide to Greening Stormwater Runoff. Resource Conservation District of Santa Cruz County 5 Managing Sports Fields in Drought/Adverse Conditions. James A. McAfee, Ph.D. Associate Professor and Extension Turfgrass Specialist. Texas AgriLife Extension Service, Dallas, Texas. 6 Obtained from SU Sustainability website