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Water Balance Workshop
Tuesday, February 20, 2007 Black Creek Pioneer Village Toronto, Ontario
Water Balance WorkshopTuesday, February 20, 2007 Black Creek Pioneer Village 8:30 a.m. 2:30 p.m. SUMMARY NOTES
Welcome and Introductions
A list of meeting participants can be found in Attachment A. All participants were recommended to review the following information prior to the meeting: Agenda (Attachment B); Water Budget Discussion Paper by Gartner Lee; Stormwater Management and Watercourse Impacts: The Need for a Water Balance Approach by Aquafor Beech; and Action Plan for Sustainable Practices by Freeman Associates. The three reports were made available on the Sustainable Technologies Evaluation Program (STEP) website at http://www.sustainabletechnologies.ca/. Adele Freeman, Director of Watershed Management, Toronto and Region Conservation Authority (TRCA), welcomed participants to the workshop and thanked the speakers for coming. Ms. Freeman introduced the concept of water balance, and stressed the importance of water management to TRCA in projects such as this development of integrated watershed management plans and the role of the Authority in source water protection. Slides from the speakers presentations outlined below can be found in Attachment C. Slides from Hans Schreiers presentation were unavailable.
Water Budget Overview
Joe Puopolo, Senior Water Resources Engineer, Gartner Lee Limited, spoke on TRCAs development of a policy for a balanced water budget approach to watershed management. This presentation was based on the water budget discussion paper previously made available to workshop participants. See Section 3.0 for questions on this presentation.
Water Balance Workshop February 20, 2007
Need for a Water Balance Approach
Dr. Craig MacRae, Aquafor Beech, spoke on the need for a water balance approach. Current practice has focused on end-of-pipe solutions to stormwater management. However, a new approach is needed which incorporates ponds, green roofs, reuse of rainwater, etc. The amount of stormwater runoff seen in urban areas is now more greatly affected by frequent small storm events than by the infrequent large events that were the main focus of flood control projects. Water that was once absorbed now runs off, due to the huge increase in impermeable surfaces in the urban environment. Sediment particle size was highlighted as an important issue in Dr. MacRaes talk, as it is important to determine where permeable surfaces would best be placed. Clay soils will not absorb water whereas soil with larger particles, such as gravel, will be able to absorb stormwater. Questions on Water Balance Overview and Need for a Water Balance Approach: Q. A. Are you aware of any case studies using low impact development at densities contemplated in the GTA? (JP) No, Im not aware of any. (CM) I do not know of any either. Are there examples of current technology implemented now or planned to be in the near future that would meet the targets for permeability that are identified here? (CM) Yes, there are methods to reduce volume, such as downspout disconnection, changes in top soil use, roadside biofilters, etc. The soil in my area is clay. Are there examples of studies done in such areas, and how much change was seen? (CM) There are only a few studies that I know of, but these methods were very effective in those studies. (JP) In the U.S., it was determined that the footprint of development also needed to be taken into account. Clay soils are definitely a greater challenge, but the cost of ignoring the volume aspect of stormwater is extremely high. Pilot projects in clay soil areas are needed. Could you comment on the idea that our streams are relatively young compared to those studied by Leopold? Could the failure of our stormwater ponds be due to this? (CM) I see it was a physics problem the amount of energy transported is the main factor, rather than the age of the streams. We found channels from various geographic locations that still had similar properties.
Don Ford, Manager Geoenvironmental, TRCA, spoke on groundwater in the TRCAs jurisdiction. A geological map of the area shows that it is 80% till, which is a relatively impervious material. Some water does penetrate through till. Only a small portion of the jurisdiction has bedrock that contains a fair amount of groundwater. Most bedrock is marine
Water Balance Workshop February 20, 2007
shale containing little water; what water there is in these rocks tends to be very saline. Stormwater usually infiltrates to the bedrock through fractures in the till. The recharge rates are being determined, but are still being refined based on links between groundwater and surface water. Present estimates for recharge on the south side of the Oak Ridges Moraine are relatively low, but higher than expected in areas near Lake Ontario. Groundwater was tracked to determine where the particles within it originated, and it was determined that groundwater originates in various areas, including the Moraine but also including areas outside the jurisdiction of TRCA. Groundwater flows very slowly. The transit time from the Moraine to the Lake is a few days for surface water and 3,000 years for groundwater. To monitor groundwater, TRCA has only 22 wells in 19 locations throughout its jurisdiction. Also, these wells will generally be drilled only to the shallowest aquifer, and there may be deeper ones below. It is important to understand that mitigation measures involving increased permeability of surfaces may not be effective in some areas. We need to identify these locations, to focus on other measures, such as green roofs, that do not depend on increased perviousness. There were no questions on this presentation.
Sustainable Technologies Evaluation Program (STEP)
Glenn MacMillan, Senior Manager, Water & Energy, TRCA, spoke on the Sustainable Technologies Evaluation Program (STEP). The program was initiated about one year ago. Components include monitoring of the York University Computer Science building green roof, a permeable pavement study at Seneca College in King City, a study on rainwater harvesting and evaluations of clean air initiatives such as solar panels, windmills, and biowalls. The York University green roof was monitored for three years and compared with a control section of the same roof. Average runoff volume was reduced by 63% in spring-fall months and 54% overall compared to the control. Water quality also improved, except for phosphorus levels, which increased due to phosphorus in the growing medium. The average additional cost of 21 green roofs across the GTA was found to be $10.45/square foot. The permeable pavement study found that a granular sub-base was needed under the pavement and soils were not very permeable. Sand bases cannot be used, since the sand collects between the stones and permeability is decreased. It is also important to avoid sanding of snow on this pavement. For more information about the STEP Program, please visit http://www.sustainabletechnologies.ca/.
Water Balance Workshop February 20, 2007
Questions on STEP: Q. A. Was any government funding provided for the construction of the green roof at York? No. The study was part of the recommendations made by a consultant, but no government funding was provided for it. What are your next projects? Are you working on front/backyard monitoring? We are listing are prioritizing technologies for future study. We are also working on a sustainable house at Kortright. One of the goals of this project is zero water runoff. How do you maintain the vegetation on the green roof under dry conditions or in winter? Maintenance is needed for green roofs and needs to be considered in the costs, usually maintenance amounts to $1 2/square foot annually. Vegetation is not replanted each year, and native plants requiring minimal watering should be used. The York roof does require watering, although this is not ideal for a green roof. For the bioswale, were sediments running off from the parking lot an issue? Monitoring is ongoing, but to date we have not seen this problem.
Wet Weather Flow Stormwater Management Guidelines
Ted Bowering, Manager Policy and Program Development, City of Toronto Toronto Water, spoke on the stormwater management guidelines under the Citys Wet Weather Flow (WWF) Master Plan. Urban runoff is a main concern for Torontos sewer infrastructure. Although combined sewer outflow is also an issue, even in areas were there arent any CSOs, volume and water quality issues are seen due to runoff. The WWF Master Plan views rainwater as a resource and requires hierarchical management of it. The guideline document was released in November 2006 (view it online at: http://www.toronto.ca/water/protecting_quality/wwfmmp/pdf/wwfm_guidelines_2006-11.pdf) and documents what is expected on-site for construction projects. The Green Development Standard is a voluntary standard adopted last year by City Council. Besides stormwater management initiatives, it offers recommendations for development that reduces energy use, helps maintain biodiversity, reduces bird collisions, etc. It can be accessed here: http://www.toronto.ca/environment/pdf/gds_standard_jan07.pdf. There were no questions on the Wet Weather Flow presentation.
Water Balance Model Demonstration Project
Mike Hulley, Associate, XCG Consultants Ltd., spoke on the study for TRCA on whether this model, developed for use in B.C., was appropriate for use in the GTA. The model will be an online tool at www.waterbudget.ca (the website is no