Assessments of Stormwater Quality and Snowmelt Runoff in Whistler Creeks, 2007-2008
Water quality monitoring results have highlighted the need for erosion and sediment source control, biofiltration pond maintenance, and improved winter road maintenance practices.
 The British Columbia Ministry of Environment (MoE), in partnership with the Resort Municipality of Whistler (RMOW), conducted water quality monitoring studies in three urbanized Whistler watersheds during stormwater (October 2007) and snowmelt (May 2008) runoff periods. Whistler waterbodies may be at risk from both types of runoff, as storm sewers convey water and potential pollutants directly into ditches, stormwater ponds, and streams, which ultimately lead to larger creeks and lakes that have high fisheries and recreational values. Common contaminants in both types of runoff include nutrients, bacteria, metals, hydrocarbons, and suspended sediments, while chloride and some impurities in road salt (e.g. copper) are additional contaminants in snowmelt runoff. The goal of both studies was to determine whether land use and winter road maintenance practices in the Whistler, Crabapple, and Fitzsimmons Creek watersheds were leading to water quality impacts in downstream locations, as well as in a stormwater ‘biofiltration’ pond that treats Whistler Village stormwater runoff.
 Results of the stormwater study showed that all three creeks and the pond had elevated levels of suspended sediment and turbidity, along with sediment-associated metals (copper, iron and zinc) that exceeded British Columbia Approved Water Quality Guidelines (BC AWQGs) for the protection of aquatic life. Activities in the upper Whistler and Crabapple Creek watersheds, including summer service road maintenance, the 2010 Winter Olympic ski run construction in 2006/07, and bike park operation on Whistler Mountain, along with urban stormwater runoff, appeared to be contributing to the observed water quality impacts. The glacially-derived Fitzsimmons Slip in upper Fitzsimmons Creek appears to be a significant source of the creek’s suspended sediments, although urban runoff from the Whistler Village area is also contributing to elevated levels of both sediments and associated metals during periods of high runoff.
 Results of the snowmelt study showed elevated levels of chloride, some metals (copper and zinc), suspended sediment and turbidity in all four waterbodies in urban areas during periods of high runoff. While Whistler and Fitzsimmons Creeks were relatively well buffered from snowmelt runoff impacts, Crabapple Creek (with higher stormwater drainage inputs) was more affected by either the high flows associated with snowmelt or practices such as snow storage within its stream banks along lower reaches. The elevated levels of copper and zinc, likely derived from sediment and road sources, exceeded BC AWQGs in Crabapple and Fitzsimmons Creeks only. Copper was also found to be a potentially significant contaminant in raw road salt and sand material used for winter road maintenance.
Results of the biofiltration pond effectiveness study showed that the pond was receiving pollutants from urban stormwater runoff at times that exceeded BC AWQGs. Elevated levels of suspended sediments, turbidity, E. coli, and metals (cadmium, copper and zinc) were observed during periods of high runoff, i.e. first flush events and early snowmelt runoff. In October 2007, the biofiltration pond was particularly effective in reducing higher levels of suspended sediments and associated metals (total copper, iron and zinc). In May 2008, total copper was effectively removed, while turbidity, total iron, nitrate and total phosphorus were only somewhat effectively removed.
Recommendations to improve water quality during both runoff periods include:
- Evaluation and improvement of current erosion and sediment control measures on summer maintenance roads and the bike park on Whistler Mountain;
- Optimization of source controls in neighourhoods draining into Whistler creeks and the biofiltration pond, e.g. low-impact development (LID) and increased infiltration;
- Optimization of winter road maintenance practices, e.g. avoid storage of excess snow near or within stream and pond banks and use of appropriate amounts of road salt and sand;
- Improvement of the biofiltration pond's performance, e.g. upgrade pond to trap sediment at inlet and periodically remove and properly dispose of the accumulated sediment.
Preliminary actions taken by RMOW as of May 2009
RMOW has indicated that the study findings and recommendations will be considered for use:
- As technical input for RMOW's stormwater management planning, now in Year 2;
- As Whistler2020 Natural Areas monitoring indicators (for water quality);
- To maintain working relationship with Whistler Blackcomb to improve conditions in Crabapple Creek resulting from bike park operation;
- To adjust winter road maintenance activities performed by RMOW Roads crew.
The complete report is available here (PDF/3.62MB)
juLY 2009
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