The Government of Nunavut Department of Community and Government Services (CGS), on behalf of the Hamlet of Arviat, is applying for the expansion of the existing sewage treatment facility, and amendment of the discharge effluent limits in the existing water licence to effectively service the growing population in Arviat until the design horizon of 2040. A business case was developed, which recommended a dual lagoon system, with seasonal effluent pump out to the wetland treatment area, to occur late in the season to allow for optimal wetland establishment. The requested amendment to the effluent limits within the wetland are based on the most comprehensive research completed to date on passive systems in Nunavut, and consider the significant change to the hydrologic regime that will be influenced by the seasonal pump out, rather than the exfiltration berm. CGS retained Nunami Stantec Limited to develop the Business Case Report for the upgrade of the current sewage lagoon in the Hamlet of Arviat. This study projected the flow and loadings based on the population growth, proposed the treated effluent goals and standards, reviewed and selected the most suitable location and treatment technologies, conducted a conceptual level geotechnical investigation and environment assessment, sized the lagoon system and conducted a conceptual schematic design.The treatment goals for the lagoon-wetland effluent criteria were established as 100, 120, and 1.25 mg/L for carbonaceous biochemical oxygen demand, total suspended solids, and un-ionized ammonia as nitrogen, respectively, based on a 6-year research project completed by Centre for Water Resources Studies at Dalhousie University.Given an estimated population of 2,657 residents in 2016 (Statistics Canada 2016), the design population to be serviced by the expanded lagoon was projected to be 4,338 people in 2040. This population will contribute a design flow rate of 434 m3/day at the end of the design horizon, requiring active storage volumes of 130,200 m3 and 158,410 m3 for 10 and 12 months of storage, respectively. The report recommends that a new lagoon cell be constructed directly adjacent to the existing lagoon to provide a storage capacity of 7 months (95,000 m3). The existing lagoon will be demolished and replaced with a new impermeable cell with an effective storage capacity of 5 months (67,000 m3) bringing the total effective storage capacity to approximate 12 months. The lagoon discharge point into the wetland treatment area will remain at the same location, but will be by controlled manual pump out.