the vento in the Bridges, Calgary A PRIMER: rainwater reuse february, 2005

Transcription

1 the vento in the Bridges, Calgary A PRIMER: rainwater reuse february, 2005

2 through Background The Vento is the fi rst of two buildings by Windmill Developments in the Bridges, Calgary. A mixed-use project, the street level is occupied by retail outlets including the Heartland Cafe and the Healthiest Home and Building Supply Store as well as two affordable housing units. A further twenty town houses occupy the second and third fl oors. The Vento is targeting to be the fi rst mixed-use Leadership in Energy and Environmental Design (LEED) Gold building in North America. Benefits of LEED LEED certifi cation demonstrates a developer s commitment to the environment, a signifi cant reputational advantage. careful fixture selection, and stormwater collection, treatment and reuse, the building will use 61% less water than a traditional building design. Marketing benefi ts typically include free publicity in the form of newspaper articles, interviews and publications. In addition, reduced operating costs can lead to long term savings in cases when the developer maintains ownership of the building(s). From the perspective of the City, the LEED standard results in reduced demand on municipal infrastructure for water, sewage, energy and waste disposal services. Residents and/or commercial space owners benefi t from future-proofi ng against rising utility costs (building design minimises energy and water consumption), a healthier place to live, a more durable building and signifi canlty improved indoor air quality. Ownership in/of a green building is an ethical investment, due to its signifi cantly reduced environmental impacts. 2

3 Project History The City of Calgary has created a master plan for the Bridges, the former site of the Calgary General Hospital. The master plan refl ects a vision of a pedestrian-friendly urban village with 1,525 residential units mixed with commercial and retail space. Parcels of land are being sold for redevelopment in accordance with the master plan. Location Fixture Flow Rate/ Volume Commercial/ Residential Commercial/ Residential Table 1: Low Flow Fixtures Toilets (Caroma Dual Flush) Lavatories (La Torre Faucet) Low Flush = 0.8 gal/flush Full Flush = 1.6 gal/flush 0.5 gpm Site Description The Vento occupies all of its lot (Figure 1), Commercial/ Residential Shower (Bricor with 1.5 gpm restrictor) 1.5 gpm ha/0.49 a, and there is no landscape available for stormwater infi ltration (see Table 2). Parking is incorporated underground, the only exception being spaces for visitors and the handicapped. The tight site boundary results in an innovative urban Residential Commercial Commercial Kitchen Sinks (Grohe faucets with Bricor addon aerator) Urinal (Falcon Waterless) Kitchen Sinks (Grohe faucets) 0.9 gpm gpm strategy to address stormwater management. Rainwater Collection Rainwater, collected from the terraces, the roofs and 78 percemt of the parking space, fl ows into the rainwater reuse tank (23,540 L/6075 US gallons). Rainwater from the remaining 22% of the parking area (7 m 2 /72 ft 2 ) on the east side of the building discharges directly into the stormwater retention tank due to site constraints. Rainfall calculations were based on average rainfall data available from Environment Canada. Peak fl ows are taken from the Alberta Building Code. 3

4 4 Figure 1: Site Plan: Main Floor Landscapingm

5 Rainwater is treated with chlorine, a fi ve micron and a carbon fi lter (See the technical sequence in Figure 2 for detailed specifi cations). If there is more water than the recycled rainwater tank can hold, stormwater will overfl ow into the stormwater retention tank (38,986 L/10,300 US gallons) and then will be discharged to the City storm system at a controlled rate of 608 lpm/158gpm. The stormwater retention tank is a City requirement to reduce the fl ow rate of storm water entering the City storm sewer system. In Brief: The Rainwater Reuse System Rain falls on the 3rd floor roof and balconies, on the 2nd floor terraces, planters and balconies and on the ground floor parking areas, planters and terraces. (See Table 2 for the percentages of the site attributed to these surface types) The water is collected and directed via piping into the recycled rainwater tank. If there is too much water, it fl ows into the stormwater retention tank and then is released into the City stormwater system at a controlled fl ow rate. If there is too little rainwater to meet the building needs, the recycled rainwater tank signals a valve that draws potable water from the municipal system. Combining rainwater and potable water at the tank is cost-effective as it eliminates the need for a second piping system (for potable water) to each fixture. From the rainwater reuse system the water is chlorinated and passed through a 5 micron fi lter. Water is then used in the second fl oor toilets and in pipes to water plants during drought periods. The toilets are dual fl ush, thus signifi cantly reducing water demand. Wastewater fl ows into the City sewage system at a controlled rate. 5

6 Figure 2: Schematic of Rainwater Reuse Systemm DESIGN BY KEEN 6 Control Sequence: 1. Pump P-6 shall cycle to maintain pressure in system. Pump shall cycle on at a pressure of 240 kpa (PSIG) and cycle off at 410 kpa (60 PSIG). 2. Upon sensing a low level in the tank, the low level float switch shall open the solenoid valve to start filling the tank. The high level switch shall close the solenoid. 3. The Chlorine system shall control the chlorine level in the recycled rainwater tank to an adjustable level of 2 ppm. System shall include: -SAI-FC-FX-100-P Amperomatic chlorine a-nalzyer c/w buffer bottle, sample tubing, control panel c/w 4-20mA signal output. Analyzer shall have adjustable range from D to 3.5 ppm. Treatment system shall be c/w pump and 5 pails of liquid sodium hypochlorite. -Upon sensing a low chlorine condition, the system shall lock out P-7 and shall activate the strobe light. The alarm shall be manually acknowledged and reset. 4. Filter F-1 shall be a floor mounted, 304 stainless steel filter unit, c/w 40 mm inlet and outlet, (Water Better W84SC or equal) c/w 5 micron filter (Water Better HC/40-5/5 or euqal). Provide 5 spare filters. 5. Filter F-2 shall be a floor mounted, 304 stainless steel filter unit, c/w 40 mm inlet and outlet, c/w activated carbon filter (Water Better HC/40-Ac-5 or equal). Provide 2 spare filters. 6. Under normal operating condition the storm water will discharge into the recycled rainwater tank and be used in the buildings. Control Valve CV-2 shall be closed. Upon sensing a high level in the recycled rainwater tank, CV-2 shall open and CV-1 shall close to divert all stormwater in the storm retention tank. What the water falls below the high level, CV-1 shall open and CV-2 shall close. 7. Safety controls: A high level float switch in the recycled rain water tank initiate an audible high level alarm, CV-1 shall be a fail closed control valve and CV-2 shall be a fail open control valve.

7 Parking Area Filtration and Reuse Water from 78% of the surface parking area (23 m 2 /289 ft 2 ) will be fi ltered to remove hydrocarbons and over 80% of total suspended solids prior to being released into the rainwater reuse cistern. Rainwater Reuse Water entering the rainwater reuse cistern will either be used for fl ushing toilets or watering plants by hose during dry periods. As a safety measure, pipes containing non-potable water are indicated with pipe makers both in each room and before they go through the wall into adjacent rooms. Hose bibbs, complete with locked lids, are clearly marked with signage. Low Flow Fixtures The Vento uses waterless urinals in the commercial space, dual flush toilets throughout the building, high efficiency showerheads, lavatories, kitchen faucets and high efficiency dishwashers in the residential spaces. The reduced water storm water is used for flushing toilets, hand watering during drought conditions and if there is an excessive amount, the water will go into the stormwater retention tank. consumption results in an added energy-saving due to a lower hot water demand. Table 2: Stormwater Collection Area Description Area Drained Area (m 2 /ft 2 ) Stormwater to Rainwater Reuse Cistern Main fl oor- parking (78%) 107 / 1,157 Main fl oor- terraces 16 / 170 Main fl oor- planters- parking & terrace area 18 / fl oor- terraces/balconies 485 / 5,222 2 fl oor- planters 186 / 2,007 3 fl oor- roof, patios,balconies 1137 / 12,234 Stormwater to Stormwater retention tank Main fl oor- parking (22%) 30 / 326 Total 1979 / 21,305 7

8 Landscaping No permanent irrigation system is being installed on the Vento site for landscaping. The plants selected for the main fl oor and the second fl oor are native or adaptive species eliminating the need for irrigation once established. The plants will need to be irrigated for the fi rst two years- they will be watered using water from the recycled rainwater tank. The planters on the roof are also a stormwater retention and uptake system- water is stored in the soil, used by plants, and/or reevaporated into the atmosphere. Maintenance The rainwater reuse system requires little maintenance. Filters must be changed periodically and the chlorine level must be monitored in order to ensure the analyzer is working. Toilets using recycled rainwater will require no more maintenance than a standard toilet water consumption is further reduced by using native and adaptive species. No premanent irrigation system is necessary. fi xture. Challenges The industry is leading the plumbing code with regard to a project of this nature. The ultimate decision for approval lay not with the City of Calgary, but with the Provincial Plumbing Inspector. This is a challenge unique to Alberta as other municipalities and jurisdictions in Canada have more fl exibility to approve new and innovative technologies and systems. Approval was also required from the Calgary Health Region (CHR) Environmental Health Department; they showed leadership in working on these issues with our development team. They required protection against cross contamination which was satisfi ed with a distinct piping system. A requirement of bacterial control using 8

9 chlorine was later added. Their approach was conservative in approving the system and it was a time consuming task for the development and consulting teams to navigate. In summary, the challenges for the developer were fi rstly, the amount of time required to receive approvals and secondly, consulting costs required to get the approvals, which were as signifi cant as the total cost of the system. Most developers would not risk these delays and uncertainties and thus the uptake of stormwater reuse systems in private development in the City is likely to be quite slow. Given the serious water issues facing the City of Calgary and the Province of Alberta, these challenges should be dealt with as soon as possible. Table 3: LEED Canada NC 1.0 Credits Measure Requirements LEED Credits Water Effi ciency Credit 1.1: Water Effi ciency Credit 1.2: Water Effi ciency Credit 2: Water Effi ciency Credit 3: Innovation in Design Credit 1: Sustainable Sites 6.1: Sustainable Sites 6,2: Water Effi cient Landscaping: reduced by 50%. Water Effi cient Landscaping: no potable water use or no irrigation. Innovative Wastewater Technologies: reduce the use of municipally provided potable water for sewage conveyance by 50%. VENTO Solutions 1 No irrigation system for landscape irrigation is installed; the plants selected for main and second fl oor are native or adaptive species. 1 No irrigation system for landscape irrigation is installed; the plants selected for main and second fl oor are native or adaptive species. 1 Low fl ow fi xtures in combination with the rainwater reuse system reduce potable water consumption for sewage conveyance by 66.3% and 85.1% in the commercial and residential spaces respectively. Water Use Reduction: 30%. 2 Water effi cient fi xtures in combination with the rainwater reuse system resulted in savings of 62% and 61.2% in the commercial and residential spaces respectively. Exceptional Performance above the requirements Stormwater Management Rate/Quantity: 25% decrease in the rate and quantity of stormwater runoff. Stormwater Management, Treatment: remove 80% of the total suspended solids and 40% of total phosphorous. 2 Water reuse systems reduces water consumption by 61.3% and reduced potable water consumption for sewage conveyance by 77.4%. 1 Stormwater is rate and quantity is reduced by 50 percent from the previous site. 1 Water from the surface parking area is fi ltered to remove 80 percent of the total suspended solids and all of the hydocarbons. 9

10 Table 4: Sample Calculations for LEED Water Effi ciency Credit 3.0 fi xture fl ow rate gallons/fl ush or gpm total people use/person/day duration # fl ushes or sec total consumption (g) COMMERCIAL SPACE design case consumption with low fl ow fi xtures (occupancy 35) dual fl ush toilet (female) dual fl ush toilet (female) toilet (male) waterless urinal (male) lavatory 0, shower kitchen sink janitor s sink total daily consumption 151 annual consumption 47,112 less rainwater collection -11,050 total 36,062 base case consumption with LEED sample reference fi xtures toilet (male) toilet (female) urinal lavatory shower kitchen sink janitor s sink total daily consumption 304 annual consumption 94,848 commercial space savings 62.0% 58,786 RESIDENTIAL SPACE design case consumption with low fl ow fi xtures (occupancy 38) dual fl ush toilet (female) dual fl ush toilet (female) toilet (male) toilet (male) lavatory 0, shower kitchen sink total daily consumption 661 annual consumption 241,265 less rainwater collection -33,872 total 207,393 base case consumption with LEED sample reference fi xtures toilet (female) toilet (male) lavatory shower kitchen sink total daily consumption 1,464 annual consumption 534, residential space savings 61.2% 326,967 total gross savings 61.3% 385,753

11 1 2 Recommendations: Create a City sustainablity team with appropriate authority and membership would ensure that proposals such as this are addressed in a coordinated approach. Another option is a Code appeal process consisting of a hearing before a city/industry committee. Table 5: System Costs Component (beyond City requirements) Wall in cistern seperating rainwater and stormwater storage Contact Information Developer Windmill Development Group Approximate Cost ($) 14,000 Waterproofi ng premium (more durable) 5,000 Water Treatment and Pump 24,000 Specifi c recycled water plumbing and irrigation 15,000 Total 58,000 Cost savings/year (@ water rate of $0.9448/m3 and sewer charge of 64.56% of water rate) 2,269 3 Work with provincial agencies and municipal authorities to build more fl exibility into the Provincial codes that allows municipalities to have more authority and fl exibility to approve Architect Busby, Perkins + Will Architects, Ltd innovative water saving technologies. Mechanical Engineers Keen Engineering Create fi nancial and cost sharing incentives for developments to integrate rainwater reuse systems. Structural Engineers Read Jones Christoffersen Ltd Build a closer relationship between the City of Calgary and the Calgary Health Region Environmental Health Department. Green Building Consultants BuildGreen Consulting The City and Health Authority need to take the lead to ensure approval for innovative projects Landscape Architecture Riparia Limited Landscape Architects and technologies, through a pre-screening and approval process. This will take the onus of this research and work off the development community. Project Management Stuart Olson Constructors Inc