Using the BC “Guidance for Assessing the Design, Size and Operation of Sedimentation Ponds used in Mining" to comply with federal/provincial sediment control legislation Clark, J.C.; Hemachandra Jayasena, H.A.
British Columbia (BC) mining companies and federal/provincial regulators have the most stringent international minesite total suspended solids (TSS) standard to contend with. Addressing the generation, mitigation and compliance of sediment release from existing and proposed minesites means end-of-pipe and runoff must not exceed a TSS standard of 30 mg/L for a grab sample (and 15 mg/L for a monthly average) – this is a requirement of the Metal Mining Effluent Regulation (MMER) under the Fisheries Act. Add to this requirement in BC: minesite discharges must not cause exceedence of the stringent BC Water Quality Guidelines (BCWQG), exceedence of which may result in pollution, as defined in the BC Environmental Management Act (EMA). A frequent use of flocculants to achieve compliance with the MMER, a BC effluent permit, and the BCWQG TSS standards, may result in flocculant-induced toxicity, which is a contravention of the MMER, the EMA, and a BC mine effluent permit. Achieving compliance with these TSS requirements requires the application of a Best Achievable Technology (BAT). In 2002, the MMER was enacted and the Ministry of Environment (MOE) developed their Guidance for Assessing the Design, Size and Operation of Sedimentation Ponds Used in Mining. An essential part of designing for federal/provincial sediment release compliance for proposed mines is the preliminary sampling/testing of minesite soils and determining the need for a flocculant addition and control system. Sampling and testing is required for: (a) prediction of sediment pond discharge and runoff quality, and (b) execution of a well-designed Sediment Pond Management Plan (SPMP) and an Erosion and Sediment Control Plan (ESCP). Failure to follow a plan which uses a predictive methodology, using site specific soils and settling testing, leaves the issue of legislative compliance to chance. If existing mines are not in compliance, it may often be the result of not performing the recommended testing and planning. The MMER is currently under review to include coal mines, Al, Fe, ammonia, Se, and may potentially generate additional onerous requirements as Environment Canada (EC) recently asked for more stringent government rules to prevent water pollution from mines. This paper will comment on and provide conclusions related to the effectiveness of the following in predicting and preventing water pollution caused by TSS: (1) BC effluent permitting, (2) the BC sediment pond design approach, (3) proposed MOE guidance on designing erosion and sediment control plans, (4) the BC TSS/turbidity Water Quality Guidelines, (5) the MMER, and (6) other applicable prediction, design and operating strategies.
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