Aquatic monitoring in the vicinity of the South Bay Mine, northwest Ontario / prepared for prepared for Talisman Energy Inc.

Abstract

Talisman Energy Inc. (Talisman) is responsible for maintenance and monitoring at the South Bay mine in northwest Ontario. This underground copper and zinc mine was operated from 1971 to 1981 and was subsequently decommissioned in the mid-1980's. Talisman is currently utilizing 'ecological engineering' to neutralize acid mine drainage (AMD) from the former mine area. Modeling predicts that AMD will continue for a minimum of 1,000 years and a maximum of 36,000 years (Kalin 1994). Water quality monitoring conducted for Talisman indicates that acid discharge and heavy metals are reaching nearby Confederation Lake in both surface and groundwater (Kalin 1994). Representatives from the Ontario Ministry of Environment and Energy (MOEE), Ministry of Natural Resources (MNR), and Ministry of Northern Development and Mines (MNDM) are concerned that this input could have long term or chronic effects. Prior monitoring has focused on biophysical conditions on the former mine site, and on the chemical composition of AMD discharges. Available data do not allow definition of the chemical or biological zone of influence of South Bay Mine discharges on Confederation Lake, nor do they help determine whether Confederation Lake is being stressed by one or more disturbances. Salmo Consulting Inc. was asked to design a cooperative aquatic monitoring program to: 1. define the zone of influence of mine discharges; 2. differentiate effects from other potential disturbance sources; and 3. determine whether Confederation Lake is being stressed by mine discharge . This report summarizes aquatic monitoring data collected in the South Bay mine area to address these objectives. Data sources include earlier studies conducted by MNR, MOEE, and consultants to Talisman, and water quality, sediment chemistry, benthic invertebrate, and phytoplankton data collected in August, 1995. Section 1 describes the biophysical setting of the South Bay mine and summarizes historical monitoring and biophysical information. Methods used during the August 1995 sampling program are given in Section 2. Aquatic ecosystem information for Confederation Lake and the three AMD discharge areas is provided in Section 3. Section 3.1 reviews historical and August 1995 water quality, sediment chemistry, benthic invertebrate, and phytoplankton data for Confederation Lake and discusses overall health of the lake and its three sub-basins. Similar data specific to the Boomerang Lake, Mill Bay, and Mud Lake AMD discharge areas are presented in Sections 3.2, 3.3, and 3.4, respectively. Each section begins with a review of the AMD discharge characteristics, reviews monitoring data, and discusses the observed zone of influence. Section 4 summarizes information from Confederation Lake and the three AMD discharge areas and provides conclusions for the three monitoring objectives identified above.