VII. Impacts of the Project

The Commission concerned itself primarily with potential transboundary impacts. It has left to Canadian institutions the questions associated with any effects that may be confined to Canada, although some of those effects may be briefly noted.

Water levels upstream of the proposed intake, in the Chippawa-Grass Island Pool, are maintained within levels prescribed in the International Niagara Board of Control Directive of 1993 (see Appendix 1). Based on statements by Ontario Hydro and the conclusions of the Commission's International Niagara Board of Control, which are based on physical modeling performed for the proposed project, while the pattern of daily fluctuations of the Chippawa-Grass Island Pool and lower Welland River might be altered following the addition of the two tunnels for the project, the levels in the Chippawa-Grass Island Pool would be maintained within the levels prescribed in the International Niagara Board of Control Directive of 1993. Similarly, during construction when cofferdams are installed in the river at the International Niagara Control Works, the levels in the Chippawa-Grass Island Pool would be maintained within the levels prescribed in the International Niagara Board of Control Directive of 1993. Water levels further upstream in the Niagara River and Lake Erie would be unaffected.

The minimum flows which must pass over the Falls would be maintained during and following construction of the project, and an unbroken crestline at the Falls would be maintained. Currently, one country is entitled to use the portion of the share of water allocated to the other country for power purposes but for which facilities are not available. Construction of the project would further enable Ontario Hydro to withdraw the portion of flows to which it is currently entitled under the 1950 Niagara River Diversion Treaty. Under certain higher flow conditions where the United States might currently divert a portion of Canada's share of water or where flows in excess of minimum would pass over the Falls, a greater portion of these flows would be diverted by Ontario Hydro after construction of the project. Flows diverted in the United States and Canada are returned to the Niagara River downstream of Niagara Falls.

After construction of one or both tunnels, but prior to construction of the proposed additional generating station, Ontario Hydro would return additional diverted flows through its current generating stations. Diverted water would flow either directly to the existing stations or be stored in the Pumping Generating Station Reservoir for use during the peak hours of daily power demand. Fluctuations in the reservoir will increase; however, the reservoir is located wholly within Canada. During periods of above average river flows, there would be greater frequency of maximum discharge from the existing generating stations. Conversely, with Ontario Hydro making greater use of its share of water, there would be a lesser frequency of maximum discharge from the existing New York Power Authority generating stations on the U.S. shore under certain high flow scenarios. Total flow in the Niagara River downstream of the returned diversion would be changed only to the degree that diverted flows are stored in the Pumping Generating Station Reservoirs prior to release.

After construction of the proposed additional generating station, diverted flows would return to the river via either the existing generating stations or the new tailrace at the new generating station. The new generating station would be located downstream from the existing Sir Adam Beck No. 1 and No. 2 stations. This would provide an additional entry point for outflows. At the new tailrace outlet, under certain high river flow conditions, there would be an instantaneous increase in water levels of up to 21 centimetres (approximately 8 inches). This change will be negligible within approximately 100 metres downstream of the Queenston plant site. Again, total flow in the Niagara River downstream of the returned diversion would be changed only to the degree that diverted flows are stored in the Pumping Generating Station Reservoir prior to release.

The International Niagara Board of Control noted that no increase in sediment suspension is expected to occur in the Niagara River at the intake since the tunnel excavation will be through bedrock. Normal construction precautions to preclude introduction of material into the river will be undertaken to address water quality issues. Therefore, no sediment or water quality transboundary impacts are anticipated.

Ontario Hydro stated that groundwater issues were considered with respect to inhibiting groundwater movement into and from all excavations for both the tunnels and the powerhouse. Injection grouting will be utilized. Water bearing strata would be locally sealed at the excavations to ensure that there is not groundwater movement into or out of the structures. Hence, Ontario Hydro concluded that there would be no cross contamination between aquifers.

Blasting will occur during construction. Ontario Hydro stated that there will be no blast effects to the United States side of the river, several hundred metres (several hundred yards) away as blast size will be restricted to maintain the integrity of the International Niagara Control Works structure and associated control building which, in places, are a few metres (a few yards) from the blast area. Blasting will likely affect fish in the river. Ontario Hydro has obtained authorization to destroy fish by any means other than fishing from the Canadian Department of Fisheries and Oceans; the authorization contains mitigation measures.

Ontario Hydro stated that air emissions will be associated with tunnel ventilation, from any concreting batch plant operations and equipment movement. Contract documents specify that dust collection systems must be installed on all appropriate equipment such that any emissions comply with the necessary Ontario Ministry of the Environment Certificates of Approvals. Dust suppressants would be used on roads and material storage piles. Emissions would be monitored and would be maintained below the Ontario Ministry of the Environment requirements. Operations would be halted if emissions exceed these limits. In this way, Ontario Hydro affirms that there would be no transportation of airborne particulate matter to the United States from the project.