202 - 2780 Veterans Memorial Parkway Victoria, BC, V9B 3S6 Phone: 778-433-2672 web: www.greatpacific.ca E-Mail: [email protected] COWICHAN VALLEY REGIONAL DISTRICT MARINE DISCHARGE OUTFALL ENVIRONMENTAL IMPACT STUDY STAGE 1 FINAL – REV 0 Attention: Cowichan Valley Regional District 175 Ingram Street Duncan, BC V9L 1N8 June 25, 2015 1019-001 REV 0 Cowichan Valley Regional District Marine Discharge Outfall - EIS Executive Summary The Cowichan Valley Regional District (CVRD) is undertaking the development of Amendment 3 to the existing Central Sector Liquid Waste Management Plan (CSLWMP). The Central Sector is serviced by the Joint Utilities Board (JUB) Lagoon Systems co-owned by the City of Duncan and the Municipality of North Cowichan, and also provides service to properties within parts of CVRD Electoral Areas D and E and parts of Cowichan Tribes reserve. The Joint Utilities Board (JUB) sewage treatment lagoons are located adjacent to the Cowichan River. The aerated lagoon treatment system produces secondary quality effluent, which is disinfected by chlorination, then dechlorinated. Treated wastewater is discharged into the lower reaches of the Cowichan River and subsequently to the Cowichan Estuary and ocean environment. In recent years, low flows in the Cowichan River have resulted in a situation where there is insufficient dilution of the effluent plume with respect to the river flow. This resulted in the temporary closure of the Cowichan River to recreational activities in August of 2014. It is proposed that the point of discharge be moved from the Cowichan River to the marine environment of Satellite Channel, where significantly more dilution can be achieved and where the likelihood of interaction between the effluent plume and sensitive areas can be reduced. The proposed replacement outfall is recommended to support a population of 70,000. This Stage 1 Environmental Impact Study (EIS) is intended to provide a review of known receiving environment conditions and a preliminary assessment of the potential impacts to the environment from the proposed marine outfall with respect to current regulatory requirements. Satellite Channel is located along the east coast of Vancouver Island, within the Gulf Islands. The Cowichan and Koksilah Rivers discharge to the head of Cowichan Bay, which opens to Satellite Channel and Salish Sea. Water depths in excess of 50 m are easily achieved within Cowichan Bay and Satellite Channel, and the substrate composition is favorable for the installation of a marine outfall. The near surface water currents are a combination of tidal circulation and estuarine flow. The estuarine flow results from the discharge of fresh water from the two major rivers at the head of Cowichan Bay. The tidal currents are likely to dominate the circulation within Cowichan Bay and Satellite Channel. Receptors of concern in relation to the siting of a new outfall include; waterfront parks and primary recreational activities, important First Nations fishing areas, and intertidal and subtidal marine resources, particularly bivalve shellfish that, when harvested and consumed, can transfer pathogens which originated in the effluent plume to humans. Bivalve shellfish areas have been identified in Satellite Channel, such as at Boatswain Bank. Areas suitable for the proposed outfall are limited within Satellite Channel. Limitations include: The regulatory minimum depth of discharge is 10 m; i Cowichan Valley Regional District Marine Discharge Outfall - EIS The maximum depth of the outfall should be minimized where possible to reduce construction and maintenance cost and safety; The point of discharge must be setback a minimum of 400 m from bivalve shellfish waters; and, High valued fishing areas, specifically Sansum Narrows; and. Numerous freighter anchor berths located within the bay. The proposed outfall should be constructed in a location that minimizes the chance of damage to the outfall from freighter anchors. Based on these primary limitations, the preferred location for the discharge is over 400 m from the low water mark, at a depth of approximately 60 m, near Chery Point marina in the proximity of the existing Lambourn outfall. Dilution modelling of the effluent plume was carried out for a discharge at the proposed location. The model predicts that the effluent plume will be trapped below a depth of 39 m and the minimum (worst case) dilution of the effluent plume is 219:1 at the boundary of the initial dilution zone (IDZ, 100m from the point of discharge). Based on the minimum dilution, identified effluent constituents will be within applicable water quality guidelines for aquatic health at the boundary of the IDZ. Fecal coliform concentrations were calculated, with respect to distance from the outfall diffuser for effluent with and without disinfection. The fecal coliform concentration in the effluent, is anticipated to be 200 MPN/100 mL with disinfection and 1 x 105 (USEPA, 1986) without disinfection. A fecal coliform concentration of 14 MPN/100 mL is predicted within 5 m of the diffuser with disinfection, and within 1,200 m to 6,300 m from the diffuser without disinfection, depending on the tidal, meteorological, and effluent flow conditions. With disinfection, water quality guidelines for bivalve shellfish harvesting are predicted to be achieved at bivalve shellfish areas. A Stage II EIS is recommended to verify the results of this study and to collect baseline receiving environment monitoring data prior to the installation of the outfall. An amendment of the LWPM will be prepared based on the results of this study. The scope of the Stage 2 EIS should include; comprehensive effluent characterization, tidal current measurements, water column profiling, and 3 dimensional hydrodynamic modelling. A pre-discharge receiving environment monitoring program is recommended for the proposed outfall replacement that includes the following components: Water quality sampling at the boundary of the IDZ and receptor sites Sediment chemistry and benthic community sampling Bio-accumulation testing in sediments, benthic infauna and wild tissue. Based on the data collected from the pre-discharge receiving environment monitoring program, modifications to the proposed outfall placement may be required. ii Cowichan Valley Regional District Marine Discharge Outfall - EIS Contents 1 Introduction .......................................................................................................................... 1 1.1 Scope of Work ................................................................................................................... 2 2 Study Area ............................................................................................................................ 3 3 Regulatory Framework......................................................................................................... 4 3.1 Existing Permit .................................................................................................................. 4 3.1.1 Effluent Monitoring ........................................................................................................ 4 3.1.2 Receiving Environmental Monitoring ............................................................................ 5 3.1.3 Outfall Inspection .......................................................................................................... 5 3.2 Provincial and Federal Regulations .................................................................................. 6 4 Wastewater Treatment System ........................................................................................... 9 4.1 Existing Wastewater Treatment and Disposal .................................................................. 9 4.1.1 Effluent Quality ............................................................................................................. 9 4.2 Future Wastewater Treatment ........................................................................................ 10 4.3 Source Control and Inflow Infiltration .............................................................................. 10 5 Existing Receiving Environment Characteristics (Cowichan River) ............................. 11 5.1 Climate Change .............................................................................................................. 13 5.2 Potential Risks to the Existing Outfall ............................................................................. 14 5.3 Cessation of Discharge from Existing Outfall .................................................................. 14 6 Receiving Environment Characteristics - Proposed Marine Discharge ........................ 15 6.1 General Site Characteristics and Bathymetry ................................................................. 15 6.2 Existing Nearby Discharges ............................................................................................ 17 6.3 Climate ............................................................................................................................ 18 6.4 Waves ............................................................................................................................. 19 6.5 Tides ............................................................................................................................... 19 6.6 Currents .......................................................................................................................... 20 6.7 Water