Humber River State of the Watershed Report - Surface Water Quality 2008 Humber River State of the Watershed Report – Surface Water Quality EXECUTIVE SUMMARY • The lower reaches of streams in the West Humber with its clay soils, low baseflow rates and urbanizing landscape exhibit the poorest overall water quality in the Humber River watershed. Conditions at the mouth of Black Creek and at the Old Mill station on the Lower Humber are not much better. The absence of modern stormwater management controls in the older urban developments upstream of these stations contributes significantly to the dirty water at these sites. TRCA, in partnership with municipalities, has identified stormwater retrofit opportunities in these areas to help address this issue; • Surface waters in the upper portions of the watershed on Cold Creek, Centreville Creek and on the Upper Main Humber display reasonably good water quality. Even the East Humber, which has experienced moderate levels of urbanization over the past 10 years, remains relatively clean; • The concentration of suspended solids in surface waters is a particularly important water quality indicator because solid particles act as a primary transport vector for other contaminants such as phosphorus, most heavy metals, and bacteria. Levels of suspended solids were highest in the West Humber, where erodible clay soils predominate, followed by the Lower Humber at Old Mill. Options available to reduce suspended solid concentrations include vegetated riparian buffers and restrictions on cattle access in rural areas, improved sediment controls on construction sites in urbanizing areas, and enhanced management of stormwater in cities and towns. The key is to reduce the volume of stormwater that runs off into streams by infiltrating as much of it as possible; • Bacteria levels in the rivers often failed to meet the provincial guideline for recreational swimming, even on streams dominated by natural and rural land uses. For instance, only 29% of samples collected in the mostly rural Centreville Creek subwatershed met the guideline. The highest concentrations were observed in the City of Toronto and on the West Humber; • All Humber watershed swimming beaches were unsafe during most of the swimming season in 2004, with the exception of Albion Hills, which chlorinates the enclosed beach area in order to keep the beach open. The three Toronto waterfront beaches were closed most frequently, in large part due to their close proximity to the mouth of the Humber River, which is a source of significant bacterial contamination. Year-to-year variations in beach posting frequency primarily reflects the frequency, duration and intensity of rain storms occurring in any given year; • The benefits of stormwater management in reducing bacteria levels at Toronto waterfront beaches was modelled as part of the City of Toronto’s Wet Weather Flow Management Master Plan in 2003. Results indicated that even with aggressive new stormwater controls in the City, the waterfront beaches would remain closed for most of the swimming season. Improvements could be achieved only if waterfront sources of beach contamination are addressed (e.g., combined sewer overflows) and upstream municipalities commit to a similarly aggressive approach to improving stormwater controls; Humber_SW_Quality_FINAL_062408F.doc i Humber River State of the Watershed Report – Surface Water Quality EXECUTIVE SUMMARY (continued) • The somewhat stringent provincial objective for phosphorus in receiving waters was rarely met anywhere in the Humber. Elevated levels in part reflect the limited capacity of current stormwater ponds and other end-of-pipe stormwater management facilities to remove this constituent. Even during dry weather, effluent concentrations from stormwater ponds and wetlands are typically at least double the provincial water quality objective for phosphorus. Stormwater infiltration practices such as permeable pavement and underground perforated pipe systems are much more effective in reducing phosphorus loads but to date, there are very few instances in the Humber River watershed where these types of practices have been implemented; • Chloride is a major constituent of de-icing salts applied to roads during the winter. Chloride levels in the Humber River are rising due to increasing urbanization. Winter levels in the Lower Humber, West Humber and Black Creek are often above the threshold established to protect aquatic life. The highest median values were recorded at the mouth of the Black Creek subwatershed which is fully urbanized. At this station, only 38% of samples collected were below the 250 mg/L limit. Further downstream, at the Old Mill station, 67% of samples collected met the guideline and in all areas north of Steeles, over 90% of samples met the guideline. A leveling off of chloride levels in Humber streams may be expected in the future as municipal salt management plans, developed in 2004, begin to take effect. Alternatives to road salts will need to be considered on local roads if significant reductions in chloride levels are to occur; • Organic and inorganic chemicals entering watercourses through spills or accidental discharges are controlled by federal, provincial and municipal governments through a complex array of regulations and programs. The large number of spills that continue to occur in the GTA suggest that still more could be done in this area. Between 1988 and 2000, there were approximately 900 oil spills and 750 chemical spills in the Humber River watershed, of which roughly half drained to the Humber River or one of its tributaries. In terms of volume, the chemical, transportation and general manufacturing sectors contributed the most to chemical spills, often as a result of container or fuel tank leaks. Actions that would help to address this problem include better spill prevention programs, improved structural controls on spill prone areas, stronger penalties for violations and stepped-up enforcement of existing laws; • Trends in water quality were assessed for copper, zinc, total suspended solids, chloride and phosphorus at the Old Mill Station on the Lower Humber. Chloride was the only one of the five variables analyzed that showed an upward trend. These data suggest that stormwater management controls in newly developed areas do appear to be effective in removing contaminants associated with suspended sediment, such as copper, zinc and phosphorus. If they were not, Humber water quality would have been expected to deteriorate with steady growth of the urban footprint in the watershed since the early1980s. Humber_SW_Quality_FINAL_062408F.doc ii Humber River State of the Watershed Report – Surface Water Quality TABLE OF CONTENTS 1.0 INTRODUCTION............................................................................................................ 1 2.0 UNDERSTANDING THE FACTORS AFFECTING SURFACE WATER QUALITY ......... 1 3.0 MEASURING SURFACE WATER QUALITY.................................................................. 4 4.0 EXISTING CONDITIONS............................................................................................... 8 4.1 Swimming and Body Contact Recreation: The Bacterial Indicator ............................... 8 4.2 Conventional Contaminants: the Aquatic Health Indicator.......................................... 10 4.3 Organic and Metal Contaminants: the Chronic Effects Indicator................................ 16 4.4 Water Quality Trends in the Humber River Watershed................................................ 25 4.5 Other Issues: Spills, Landfills, Sanitary Servicing, Golf Courses ................................ 27 5.0 SUMMARY AND MANAGEMENT CONSIDERATIONS .............................................. 29 6.0 REFERENCES............................................................................................................. 32 LIST OF FIGURES Figure 1: Water Quality and Fish Tissue Monitoring Stations................................................... 6 Figure 2: Percent of Samples that Meet Guidelines for E.coli and Conventional Variables... 12 Figure 3: Percent of Samples that Meet Guidelines for Selected Trace Metals. .................... 22 Figure 4: Trends in Annual Median Concentrations of Chloride, TP, TSS, Copper and Zinc at Old Mill Station (Lower Humber).............................................................................. 26 LIST OF TABLES Table 1: The Environmental Effects and Sources for Key Water Quality Variables. ............... 5 Table 2: Data Sources, Locations and Period of Record......................................................... 7 Table 3: Humber River E.coli Levels and Humber Beach Postings ........................................ 9 Table 4: Percent of Time Selected Conventional Pollutants Met Guidelines at Humber River Monitoring Stations (2002 - 2004) ............................................................................ 11 Table 5: Wet Weather Concentrations During the Warm Season (1996 to 2004)................. 15 Table 6: Levels of Canada-Ontario Agreement ‘Tier 1' Contaminants in the Lower Humber River at Old Mill station............................................................................................. 18 Table 7: Levels of Poly-Aromatic Hydrocarbons (PAHs) Sampled in the Lower Humber River at the Old Mill Station................................................................................................ 19 Table 8: Percent of Samples that Met Guidelines for Selected Trace Metals at Humber River Monitoring