Sewage Outfalls Update
Monitoring of wastewater discharges, surface waters and the seafloor environment in the vicinity of the Maculay and Clover points outfalls has been conducted as part of the Wastewater and Marine Environment Program on a regular basis since the late 1980s.
With the updated Core Area Liquid Waste Management Plan, there were additional investigations required over the routine ones CRD had been doing.
The 2010 Annual Report presents results and updates for the different elements of the Macaulay and Clover points.
Surface water monitoring continue to show that during slack tide the sewage plume does still reach the surface. At Macaulay Point the highest fecal coliform count was during a visible plume event which happened in September but there is also plume surfacing in the summer, just not as frequent. Clover Point had it’s highest concentration in October and also had summer plume surfacing as well. The data indicated that the Clover Point effluent plume was predominantly trapped below the surface, with occasional surfacing events!
Seafloor Monitoring at Macaulay Point showed exceedences at monitoring stations within 200 m of the outall and included copper, mercury, PAHs, pyrene, phenanthrene, 1.4-dicholorobenzene (used in disinfectant, deodorant and pesticides), 1,2,4-trichlorobenzene (solvent), and phenol (antispetics and disinfectants and used in manufacturing resins, nylon, dyes and pharmaceuticals).
Overall, 2010 results indicated demonstratable impacts of the outfall on sediment chemistry and thus there is potential for the biological communities to be affected by substances in sediments, especially at stations within 200 m of the Macaulay Point outfall.
Benthic Communities – A comprehensive multi-year trend assessment including the 2010 benthic community data indicated potential declining environmental conditions around the Macaulay Point outfall. Conclusions made in the past assessments require revision because true changes are now occurring in the biological assemblages.
The most significant changes near the outfall included a lower total organism abundance, a modified benthic community with fewer types of species and lower numbers of individuals, reduced biological diversity that now extends beyond the initial dilution zone (and in some cases beyond the near field stations), a decreased abundance of sensitive species and an increase in abundance of pollution-tolerant species.
In 2010 the benthic community data at the outfall terminus station were indicative of a “highly degraded” benthic community. Taxa richness at the outfall terminus has changed since the first comprehensive assessment was undertaken in 1994.
Seafloor monitoring at Clover Point showed exceedences of copper, mercury, acenphthene (used as plasticizer in manufacturing of PVC and in hydraulic fluid, also found in coal tar) and bis (2-ethylhexyl) and phthalate (used in coatings for pharmaceutical pills and nutritional supplements, adhesives and glues, and personal care products, to name a few uses).
Similar to Macaulay Point, these exceedences at Clover Point outfall has the potential to impact the biological communities due to the contaminants in the sediments.
There were a high resolution analyses of two components done in 2010. Tributyltin (organic compound of tin used as a biocide especially in marine antifouling paints) was one compound and the levels exceeded Canadian and BC water quality guidelines.
Methylmercury (an organic form of mercury that is most easily bioaccumulated in organisms like fish) is a highly toxic substance that can build up in predatory fish. 2010 analysis showed this was below guidelines.
Both methylmercury and tributyltin analyses will be shifted to the routine monitoring to allow for long-term monitoring of concentrations, environmental loadings and potential for environmental toxicity.