Establishing the Criteria
The Ministry of Environment, Lands and Parks is developing ambient water quality criteria for British Columbia. This work has two goals:
· to provide criteria for the evaluation of data on water, sediment and biota
· to provide criteria for site-specific ambient water quality objectives
The criteria represent safe conditions or safe levels of a substance, and are set to protect various water uses. A criterion is defined as "A maximum and/or a minimum value for a physical, chemical or biological characteristic of water, sediment or biota, which should not be exceeded to prevent specified detrimental effects from occurring to a water use, including aquatic life, under specified environmental conditions."
The criteria are applied province-wide, but they are use-specific, and are being developed for these water uses:
· raw drinking water, public water supply and food processing*
· aquatic life and wildlife
· agriculture (livestock watering and irrigation)
· recreation and aesthetics **
· industrial water supplies
The criteria are established after considering the scientific literature, criteria from other jurisdictions and environmental conditions in British Columbia. The scientific literature provides information about the effects of toxicants on various life forms. This information is not always conclusive because it is usually based on laboratory work that, at best, only approximates field conditions. To compensate for this uncertainty, and applying the "precautionary principle", the criteria have built-in safety factors that are conservative, but reflect the natural background in the province. The criteria are subject to review and revision as new information becomes available or as other circumstances dictate.
Using the Criteria to Set Objectives
The criteria are used to set ambient water quality objectives for specific waterbodies. The objectives are also based on present and future uses, waste discharges, hydrology, limnology, oceanography, and on existing background water quality.
In most cases, the objectives will be the same as the criteria. However, when natural background levels exceed the criteria, the objectives could be less stringent than the criteria. In rare instances-for example, if the resource is unusually valuable or of special provincial significance-the safety factor could be increased by using objectives that are more stringent than the criteria. Another approach in special cases would be to develop site-specific objectives by conducting toxicity experiments in the field. However, because this approach is costly and time consuming, it is seldom used.
Neither the criteria nor the objectives derived from them have any legal standing. Objectives can be used to calculate waste discharge limits.
These limits are outlined in waste management permits which do have legal standing. (Objectives are not usually incorporated as conditions of a permit.) Objectives are also used in the preparation of waste management orders and approvals. These documents also have legal standing.
