NWT RESEARCH DATABASE

Regions: North Slave Region

Tags: physical sciences, water sampling, water monitoring

Objective(s): To conduct water monitoring to ensure that the project is overall compliant with the environmental permit and approval conditions and requirements.

Project Description: This licence has been issued for the scientific research application No.4946. The objective is to conduct water monitoring to ensure that the project is overall compliant with the environmental permit and approval conditions and requirements. Monitoring at water crossing locations will be required for any in-water construction and where there is potential for entrainment of sediments. This includes locations where there may be construction below the high-water mark and where flows are present (i.e., the water is not frozen to bed or dry at the time of construction). Monitoring of turbidity levels may be initiated on non-permanent water bodies when there is a construction-related incident resulting in potential entrainment of sediments. Prior to initiation of a monitoring program, the monitoring crew will survey the study area at each crossing location. The crew will set up sampling (cross-sectional) transects relative to the work area per crossing (one upstream and three downstream transects); the positioning of downstream transects will depend on the size of the water body. All transect locations will be marked with a Global Positioning System (GPS) in addition to any other site marking methods used (e.g., flagging tape). Development of Relationship Between TSS and Turbidity Total Suspended Solid (TSS) is a composite of suspended inorganic and organic solids and cannot be immediately or directly measured in the field. Measurements of TSS (milligrams per litre [mg/L]) require specialized equipment and considerable time, making the required analytical procedure impractical for use in field settings. For this reason, measurements of turbidity (Nephelometric Turbidity Units [NTU]) will be used for the Tli?cho All Season Road as a surrogate measurement for TSS. TSS (mg/L)-turbidity (NTU) relationships can vary between water bodies, and in larger systems, can vary between sites. Prior to construction, a sediment sample will be collected from instream and exposed portions of riverbed substrate adjacent to each crossing. For each water body, the crossing-specific sediment and water samples will be combined to produce approximately 20 surrogate suspended sediment samples, creating a range of turbidity values that might be encountered during construction. The TSS samples may be collected up to one month in advance of construction; collecting TSS samples during periods with increased suspended solids (i.e., during freshet, following heavy rains) should be avoided to ensure that samples with low levels of suspended solids are included when calculating the TSS turbidity relationship. Upon receipt of results, TSS and turbidity data will be plotted graphically and analyzed using statistical modelling to create a TSS-turbidity relationship specific to the crossing location. As a result, it will be possible based on the relationship to determine when TSS levels exceed the CCME TSS guideline in the field and provide notification to the NSI Environmental Manager to apply the appropriate mitigation measures during construction. The TSS correlation will be updated monthly to validate / calibrate the TSS turbidity relationship, using weekly TSS samples that are concurrent with the turbidity readings. Turbidity Measurements Locations of manual sample collection during in-water construction will be determined by crews on a day-to-day basis and may vary based on environmental conditions and ice safety at the time of collection. All transects and sample stations will be sampled at a minimum frequency of two times daily during any works taking place below the high-water mark, but more frequent monitoring may be triggered based on monitoring results. No less than six hours should pass between the start of the first sample collection and the start of the last sample collection for each day, and at least one set of samples should be collected immediately prior to work starting below the high-water mark to identify any baseline variations in TSS/turbidity between sampling sites. Photos upstream, downstream, and of the left and right downstream banks at each transect must also be taken during a sampling event. Information for every photo taken must be recorded in a “Photo Log” datasheet. Turbidity levels and calculated TSS for each sample will be documented in the data sheet. Water throughout the water column will be collected for each sample, with the crew lowering and raising a bottle attached to a pole through the water column at a steady rate to collect the sample. For sites where depths are shallower than 0.5 m, samples can be collected by hand at the mid-column depth. Any samples where the bottle or pole contact the substrate will be discarded and resampled after any disturbed sediment has settled out (e.g., 30 seconds). Collection of samples to be upstream of the sampler to avoid capturing sediment disturbed by field personnel. Turbidity will be measured using a portable turbidity meter. The meter will be calibrated daily using a blank (0 NTU) and a standard appropriate for the range of expected turbidity levels (i.e., 10, 40, 100, or 400 NTU), following manufacturer’ instructions. Prior to measuring turbidity, each sample collection container will be gently agitated to re-suspend settled solids. The outside of the 20 mL test vial will also be cleaned and dried with ultra-low lint tissue prior to testing. The inside of the test vial will then be rinsed three times with a portion of the sample being tested, and then a sub-sample will be immediately withdrawn from the sample container and analyzed in the test vial. This process will be repeated for each sample. Samples will be disposed of on site or archived for TSS analysis, if needed. Weekly TSS water samples will be collected and sent to a certified lab for analysis. Turbidity measurements in the field will be used to predict TSS. Where multiple sample points exist along a site’s upstream transect (cross section), the results for each of the upstream sample points measured during an individual sampling event will be averaged to determine a background TSS concentration (mg/L) for that sampling event. The average TSS concentration (mg/L) will then be calculated for each of the downstream transects (cross sections) separately, and then these transect averages will be compared to the background TSS concentration (mg/L). Where sampling transects consist of only a single sampling point per transect, downstream results will be compared directly to upstream results from the same sampling event with no averaging required. Monthly and annual report will be generated and provide to the community organization. The project also has a working group that consists of personnel from Department of Fishers and Ocean, Government of Northwest Territories, GWNT Environmental Natural Resources, Environment and Climate Change Canada, Tlicho Government, Wek’eezhii Land and Water Board as well as elders and community members from Whati, North Slave Region and Behchoko, which meet every 6 months to discuss different topic or any project concerns. The project also has an engagement management plan that is followed and documents all engagement that has take place for the project. The fieldwork for this study will be conducted from June 17, 2021 to December 31, 2021.