EXECUTIVE SUMMARY
The Aquatic Effects Technology Evaluation (AETE) Program was established to conduct field and laboratory evaluation and comparison of selected environmental effects monitoring technologies for assessing impacts of mine effluents on the aquatic environment. Field evaluations were conducted at seven mine sites in 1996 to determine which sites were suitable for further evaluation in 1997. This final field survey report provides detailed information on work conducted at the Heath Steele Mine site near the City of Miramichi, New Brunswick.
The 1996 field survey at the Heath Steele Mine involved the following study/field components: historical data review:
- sublethal toxicity testing;
- habitat characterization and classification;
- water chemistry sampling;
- benthic invertebrate sampling;
- fish population sampling; and
- fish tissue collection.
A summary of the results of the 1996 survey at the Heath Steele Mine are presented in the following executive summary table. The 1996 field survey results indicated that this site meets some of the suitability criteria for hypothesis testing in 1997. The evaluation of the suitability of this site is presented under separate cover.
An extensive historical database on effluent, water chemistry and benthic invertebrate community structure exists for the Heath Steele Mine. Fisheries population studies have also been conducted to determine the presence and absence of species and to monitor the recovery of populations in the Tomogonops and Northwest Miramichi Rivers. This historical data was valuable for assessing where reference and exposure areas should be located in the 1996 field survey. Results of the 1996 program were also compared to these historical data sets.
The Heath Steele Mine site was easily accessible and multiple reference and exposure areas of uniform habitat and substrate composition were available. There were no confounding discharges into the receiving environment which would affect result interpretation. The mine discharges both point (tailings discharge) and non-point (seepage) sources into the South Branch, and North and Little South Branches, of the Tomogonops River, respectively. To optimize sampling effort in the 1996 survey, the exposure area was located on the Tomogonops River below the confluence of the North and South Branches. This area is frequented by sentinel fish species and is exposed to the combined mine discharges (tailings effluent and seepage). The reference area was located on the Northwest Miramichi River at Payne’s Bridge.
The exposure area selected for the 1996 survey, had not been sampled historically. Exposure stations have typically been located on the North Branch, Little South Branch, South Branch or the Tomogonops River upstream of its confluence with the Northwest Miramichi River. Stations located on the different Branches are exposed to either mine seepage or mine effluent which differ in effluent composition and may affect aquatic biota differently. In addition, fish populations on these Branches are of limited abundance. The historical exposure station located on the Tomogonops River at the confluence with the Northwest Miramichi River (HS-20) was not an optimal station for the 1996 survey as fish and benthic communities have recovered at this station over the last several years. Therefore, the exposure area sampled in 1996 was located on the Tomogonops River below the confluence of the North and South Branches as this area is exposed to the combined mine discharges and provided for optimized sampling effort for water chemistry, benthic invertebrate communities and fish populations.
Effluent is discharged continuously at the Heath Steele Mine site from the tailings pond east overflow. Sublethal toxicity testing was conducted on the effluent and results clearly indicated toxicity to Ceriodaphnia dubia reproduction, juvenile fathead minnow survival and growth, Selenastrum capricornutum growth, Lemna minor growth, and trout embryo viability. It is recommended for future studies involving sublethal toxicity testing, that receiving (dilution) water be screened for toxicity to C. dubia and fathead minnow prior to effluent testing, that all sublethal tests be performed on effluent collected on the same day, and that sublethal tests be conducted on more than one occasion to obtain an estimate of testing variability.
Suitable representative depositional areas did not exist in either the reference or exposure area for sediment sampling. Due to the lack of sediments, the water column represents the main source of exposure of aquatic biota to metals discharged from the mine. As a result, water chemistry analyses should be used in future field programs to measure exposure. A significant difference in general water chemistry (chloride, sulphate, conductivity, hardness, TDS and DOC) and total and dissolved metals (Ba, Ca, Cu, Mg, Mn, Na, Pb, Sr and Zn) existed between the reference and exposure areas. Results from the benthic invertebrate sampling program showed significant differences in total species abundance and richness between the reference and exposure areas.
Richness of sensitive species did not differ between areas. These results were consistent with historical results. Based upon the results of BEAK (1996c), it is recommended that a mesh size of 250 µm be retained for sample collection and composite Surber samples be collected at each sampling station.
Juvenile Atlantic salmon and lake chub were the dominant species found in both the reference and exposure areas and these species were abundant. Significant differences in lengths and weights of salmon occurred between these areas. Although sample sizes were small, juvenile salmon were larger and heavier in the reference area. Estimates of variability in condition did not differ between areas for either salmon or lake chub. However, size-at-age relationships significantly differed between areas for both species.
Tissues of lake chub and juvenile Atlantic salmon were sampled for metals and metallothionein (MT) analyses from the Northwest Miramichi River (HS-21) and the Tomogonops River (JW-El). Although MT levels were significantly higher in both species from the exposure area, sample sizes were small, metals data did not support the MT results, and results from the alternate reference area (BCL-4) showed the highest MT levels in lake chub. Future studies of metals and metallothionein are possible at this mine site with two restrictions. Firstly, a barrier does not exist at the site to eliminate the possibility of fish migration between the reference and exposure areas. Thus, caged fish would be a suitable alternative for evaluating effluent exposure at this site. Secondly, as only small fish are available and abundant (juvenile Atlantic salmon and lake chub) in the reference and exposure areas, comparison of different tissue burdens could not be evaluated as the fish are too small for dissection.
Overall, the Heath Steele Mine site was suitable to sample all program components in 1996 with the exception of sediments. The sampling locations were accessible and a reasonable level of effort was required to complete the field survey.
