080121-08MN006-Sabina Hackett River Project Proposal ... - NIRB

Description of the Existing Environmentin CHS (1994). The estuarine influence is clear in the low salinity, warmer surface layer and thehigher salinity, cold deep layer found in the water column structure studies conducted in BathurstInlet (Rescan 2002; Rescan 2008b).6.1.11.2 Marine Water Column Structure and CharacteristicsSecchi depth is a measure of water clarity or transparency, and is a field measurement that issensitive to suspended solids and phytoplankton abundance. Secchi depth can be used tocalculate the base of the euphotic zone (the zone in the water column where enough lightpenetrates so that photosynthesis can occur).The average Secchi depth measured near the port site during the 2001 and 2007 surveys was3.5 m. The resulting calculated average depth of the euphotic zone was 9.8 m deep.The water column was highly stratified in August of both 2001 and 2007, with layering observedat several stations in 2001. Data show a warmer, fresher mixed layer approximately 7 m deepoverlying a water column continuously stratified in both temperature and salinity. The surfacetemperature in both years was ~11˚C, and salinity was ~10 PSU in 2001 and 16 PSU in 2007.The exception was Station 01-1 in 2001, which exhibited a surface layer of freshwater (0 PSU)that was not present in August 2007.Salinity approached 26 PSU and temperature approached 0˚C at depths greater than 30 m.The water column structure present near the port site is typical of partially mixed estuaries,characteristic of the seaward reaches of fjords where there is relatively greater wind mixing,stronger tidal currents and action, and lower run-off than at the head of the fjord (which issheltered and usually the location of the freshwater source).Vertical profiles of dissolved oxygen collected in 2007 show an oxygen maximum atapproximately 15 m depth, suggestive of highly oxygenated, cooler, and saltier offshore watersinking beneath the fresher surface layer.6.1.11.3 Marine Water QualityMarine water quality data are available from 2001 and from 2007 (Rescan 2002, Rescan 2008b).Both surveys were conducted in August. In 2001, 5 stations were sampled, with water samplesbeing collected from 5 depths at each station. In 2007, 4 stations were sampled (including areference station across the inlet), with water being collected from 4 depths per station. Duringboth surveys, water sampling depth was calculated based on a CTD (conductivity, temperature,depth) profile and the measured pycnocline depth at the station being sampled. Pycnoclinedepths were generally around 10 m during both surveys.TDS, major dissolved anions and cations (fluoride, silicate, bromide, sulphate, chloride, calcium,magnesium, potassium, sodium, strontium) all had similar profiles, with low concentrations inthe upper water column, higher concentrations around the pycnocline, and high concentrations atdepth. These parameters reflect the lower salinity water near the surface and the high salinitywater (although still more dilute than oceanic seawater) at depth.January 2008 Hackett River Project – Project Proposal Sabina Silver CorporationReport Version B.1 6–24 Rescan Environmental Services Ltd. (Proj. #833-2)