LIQUID EFFLUENT DISCHARGE LEVELS
(1) All storm runoff from the operating site and all liquid effluents resulting from the operation shall be collected and treated to meet the following suspended solids concentrations prior to discharge into a watercourse or beyond the property boundaries: (a) maximum suspended solids concentration in an grab sample – 50 mg/l; (b) maximum arithmetic monthly average suspended solids concentration – 25 mg/l.
The quote above is directly from the Pit and Quarry Guidelines for Nova Scotia.
Aggregate quarries produce waste such as dust, silt, liquid effluent discharge, and chemical wastes, and HRM has noted mounting concern about water borne silts in lakes and streams in the Shubenacadie watershed area.
We consulted with the Forest Watershed Research Center and they advised us on the nearby watercourses, wetlands and groundwater. Considered together, the geographical location and hydrology of the site, along with the clearing of 12.6ha by excavation, present great challenges to designing a quarry able to meet the Pit and Quarry Guidelines for suspended sediment. These guidelines, when not properly accommodated, likely lead to sediment suspension and runoff events that may exceed the guidelines limits and during quarry operations. This may have already taken place during the recent excavation operations at the quarry. In terms of sediment filtering, Wetland “A” in Figure 2, which is beyond the property boundaries, may already have accommodated some to the sediment release prior into Soldier Lake but it does not occur in compliance with the Pit and Quarry Guidelines for: reduced 1) effluent introduction into nearby watercourses; and 2) into watercourses beyond the property owned by Scotian Materials.
The overall suspended solids dilution factor for the water flowing from the two quarry-containing watersheds (pictured above in the pale purple and yellow) can be expected to be about 10, on account of the other inflow areas, and these streams themselves are habitat areas for fish and other wildlife. In addition, the wetland labeled “A” is located on Crown land. Holland Brook (the watercourse leading from the pond to wetland “A” in the large dark green watershed) and Soldier Lake are popular recreational fishing spots known to have trout and bass. Most of the water that enters the watersheds surrounding the quarry through precipitation and pumping water will flow toward Soldier Lake. According to the industrial application, the till at this location is quite thin (e.g, <50cm), and hydrological modelling predicts that other than a quarter to a third of annual precipitation which evaporates and transpires, much of the rest will flow towards Soldier Lake. Only a small amount likely enters the below-surface bedrock aquifers as long as the bedrock conditions remain impervious. Forest vegetation takes up large quantities of water during the summer, and plays an important role in protecting against soil erosion and allowing ground water recharge. Now that the forest has been cleared on 12.6ha of land, there will likely be much more biologically unfiltered water remaining within the area of the proposed footprint. Wetlands help to keep sediment from entering watercourses in general. However, wetlands can be overtopped especially when small during high flow events. Recent flooding caused provincially mapped wetlands at a nearby location (Perrin Dr. at Sanctuary Court) to become submerged. High flow events in January 2016 caused driveways to wash out on nearby Preakness Crescent.
Why does suspended sediment matter? It smothers fish eggs, causes gill abrasion to fish, hides their food, and reduces productivity in the ecosystem. It scours stream beds and increases erosion. At high levels it’s not good for drinking water or plant life.
Member of the Nova Scotia Road Builder’s Association Robert MacPherson. Scotian Materials Limited. Rob MacPherson. Contact. Address: 100 Venture Run, Suite 103. Dartmouth. #scotianmaterials scotianmaterials.com scotianmaterials.info scotianmaterials.ca Halifax quarry quarries aggregate gravel #noFRquarry Scotian Materials Ltd.