4.1 Re-evaluating the Site-specific Objectives
· The site-specific objective for fecal coliforms to protect raw drinking water that will receive only disinfection was not always met. However, the turbidity of the river was such that partial treatment (e.g., filtration) to remove the turbidity prior to drinking was needed most of the time. We recommend that the fecal coliform objective be re-evaluated to consider the need for partial treatment plus disinfection. The guideline to protect water receiving partial treatment plus disinfection (i.e., 90th percentile of 100/100 mL) was met.
· Monitoring should include: flow, dissolved organic carbon, fecal coliforms, true colour, hardness, total dissolved nitrogen, total phosphorus, low-level dissolved ortho-phosphorus, non-filterable residue, turbidity and total and dissolved metals (aluminum, chromium, copper, iron, manganese, titanium, and zinc).
· Lower minimum detectable limits (MDLs) are needed for antimony, arsenic, cadmium, lead, selenium, silver, and thallium should these metals be monitored in future. MDLs should be at least 10 times below the water quality guidelines or objectives for all variables.
· Increased sampling (five samples in 30 days), should be employed for fecal coliforms and copper to compare results to objectives and guidelines more accurately.
· Field blanks and replicates should be collected to assess artificial contamination and precision.