Chapter 6.0 North
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North Bay-Mattawa Source Protection Area –Assessment Report as approved Feb 10, 2015 6.0 North Bay 6.1 Introduction & Summary of Findings This Section includes analyses of vulnerability with respect to both water quantity and water quality for the surface water intake for the City of North Bay. General methodology for water quality vulnerability assessments for surface water systems is described in Section 3 of this report. The information specific to water quality vulnerability in this Section is based primarily on the Surface Water Vulnerability and Threats Assessment for Drinking Water Source Protection for the City of North Bay, 2010a, prepared by AECOM Canada, and includes the following: intake characterization (including water treatment plant and raw water quality); intake protection zone (IPZ) delineations; uncertainty analysis of IPZ delineations and vulnerability scores; drinking water issues evaluation; threat identification and assessment; and gap analysis and recommendations The primary purpose is to identify existing and potential activities that could negatively impact the quality of drinking water. To that end, the conclusions must summarize all circumstances that could pose either chemical or pathogenic threats based on the MOE Table of Drinking Water Threats. Water quantity assessments were reviewed by a peer review committee as well as by the Manager of Environmental Services for the City of North Bay. Technical review of the water quality assessment was provided by a technical advisory committee, which consisted primarily of members of the Trout Lake Watershed Advisory Committee, a multi-stakeholder committee including representatives of various ministries, institutions, associations and municipalities. Local knowledge was solicited and comments received at two public meetings, one early in the process and another when the draft findings were presented. Additional peer review was not conducted because the technical challenges posed by the assessment were considered well within the expertise of the consultant. The full report is available at www.actforcleanwater.ca or directly from the North Bay-Mattawa Conservation Authority. Based on this evaluation, there are no existing significant drinking water threats related to either chemicals or pathogens for the City of North Bay. However, the North Bay-Mattawa Source Protection Committee (SPC) has submitted a request to the Ministry of Environment (MOE) to add, as a local threat, the transportation of hazardous substances along the rail line and highway that run through the Intake Protection Zone-1 (adjacent to Delaney Bay where the source water intake is located). The MOE decision is pending. 6.2 Water Budget and Water Quantity Stress Assessment General principles were explained earlier in Section 2.5 Conceptual Water Budget. The methodology specified in the Technical Rules Part III describes a tiered approach whereby all subwatersheds are subjected to a Tier One Subwatershed Stress Assessment and if stress is low during all months of the year, no further assessment is required. If stress levels are shown to be either moderate or significant, a more robust Tier Two Subwatershed Stress Assessment 204 North Bay-Mattawa Source Protection Area –Assessment Report as approved Feb 10, 2015 is completed and, similarly if that reveals moderate or significant stress, a Tier Three Local Area Risk Assessment must be undertaken The subwatershed analyzed to assess quantity stress related to the City of North Bay supply is a combination of the contributing areas to both Trout Lake and Turtle Lake, herein referred to as the Trout/Turtle Lake subwatershed. The channel between the two lakes was previously lowered by blasting and the outlet of Turtle Lake is controlled by a stop-log dam such that the water surface of both lakes is contiguous. The Trout/Turtle subwatershed from which the City of North Bay draws its water underwent all three tiers of analysis for water quantity. The Tier One Subwatershed Stress Assessment was completed by Gartner Lee Ltd (2008b). The Tier Two Subwatershed Stress Assessment and Tier Three Local Area Risk Assessment were undertaken by AquaResource (2010). For the Tier Two and Three studies, in addition to a surface water flow model, a reservoir routing model was developed enabling verification of model results to a secondary dataset to increase confidence. Since there are no hydrometric gauges on the Trout/Turtle outflow, the adjacent LaVase River and Chippewa Creek subwatersheds were both modelled and the water budget components applied as appropriate to model the Trout/Turtle subwatershed. Further detail is provided below, while a comprehensive description of the approach used for water budget modelling is provided in Appendix B of the Trout/Turtle Lake Tier Two Subwatershed Stress Assessment and Tier Three Local Area Risk Assessment report, available at www.actforcleanwater.ca. To further understand the nature of the hydrologic flows within a subwatershed and protect vulnerable areas, there is also a need to identify Significant Groundwater Recharge Areas (SGRAs). These are areas which typically facilitate the transmission of precipitation to recharge the aquifer. SGRAs for the Trout/Turtle Lake subwatershed were identified using the threshold of 115% as per Rule 44(1), further described below. The purpose of this analysis is to make sure that the dynamics of the system area are well enough understood to ensure the water supply is well managed now and into the future. Ontario Regulation 287/07 Section 1.1(1) identifies 21 prescribed drinking water threats for the purpose of defining “drinking water threat” under the Clean Water Act (2006) subsection 2(1). Two of these relate to water quantity threats as follows: an activity that takes water from an aquifer or surface water body without returning the water taken to the same aquifer or surface water body; and an activity that reduces the recharge of an aquifer. The City of North Bay withdraws drinking water from Trout Lake in the Ottawa River watershed and returns the treated wastewater to Lake Nipissing in the Great Lakes watershed. This practice significantly predates the Great Lakes Charter Annex (2001) (see Section 2.8 Great Lakes Agreements) and is permitted under Ontario Permit To Take Water 6565-7T6PTN. All such inter-basin transfers do constitute a prescribed threat as per clause 19 above. Further, Trout Lake is located in the headwaters of the Mattawa River and it depends on a relatively small basin to capture precipitation to maintain lake levels. This makes it more vulnerable to over-exploitation; however the City of North Bay has in place policies and practices intended to minimize over use and loss. Historically, the Trout Lake water level has never dropped below the drinking water intake. The intake is located in Delaney Bay of Trout Lake at a depth of 21.5 m. Therefore the lake can function as a reservoir for significant periods continuing to provide water to the North Bay system even if the level of the lake was dropping. Therefore, the tiered assessments focus on 205 North Bay-Mattawa Source Protection Area –Assessment Report as approved Feb 10, 2015 scenario two and three: percent water demand under normal conditions and the drought assessment scenario as necessary. A subwatershed’s potential for stress is estimated by comparing the amount of water consumed to the amount of water flowing through the subwatershed. Estimated consumptive demand, when divided by the available water supply, minus a reserve term (to allow for other users and ecological demands), and expressed as a percentage, results in a value known as Percent Water Demand. If the moderate or low threshold is surpassed at the Tier One level, a Tier Two assessment is required. The Provincial Thresholds are shown in Table 6-1 below: Table 6-1. Thresholds for Stress Levels based on Percent Water Demand Surface Water Potential Maximum Monthly (%) Stress Level Assignment Water Demand Significant ≥ 50% Moderate > 20% and < 50% Low ≤ 20% The percent water demand calculations and threshold values in a Tier Two Subwatershed Stress Assessment are the same as a Tier One Subwatershed Stress Assessment. However, the Tier Two assessment uses more refined water demand estimates as well as a more advanced water budget model, including both a continuous surface flow model and a groundwater flow model. For the Trout/Turtle Lake subwatershed, there are no permitted groundwater takings and the sole municipal water supply is from Trout Lake. As such, a groundwater flow model was not considered. Municipal water supplies within a confirmed Moderate or Significant potential for stress at the Tier Two level proceed to a locally focused Tier Three Local Area Risk Assessment. The object of the Tier Three Assessment is to estimate the likelihood that municipalities will be able to meet current and future water quantity requirements, while meeting the needs of other water uses. Water budget modelling at the Tier Three level is even more sophisticated than the other Tiered Assessments. The tasks required to assess the Risk level of each Local Area within a Tier Three Local Area Risk Assessment are listed below: 1. Local Area Delineation. The Local Area for a surface water intake is referred to as an intake protection zone for water quantity, abbreviated as “IPZ-Q”. IPZ-Qs are delineated by determining the total drainage area that provides water to a municipal intake located within subwatersheds identified through a Tier Two Subwatershed Stress Assessment as having a Moderate or Significant potential for stress. 2. Assign Tolerance Level. Tolerance is defined as the municipal system’s ability to meet peak water demands. If the municipal system is able to meet peak water demands, a Tolerance level of “High” is assigned. If the municipal system is not able to meet the peak water demands, a Tolerance level of “Low” is assigned. 3. Assign Exposure Level. Exposure evaluates whether a Local Area can supply sufficient water to meet the demands of the municipal system, and other water users.