TALOYOAK, NUNAVUT – SEWAGE TREATMENT FEASIBILITY STUDY

CSCE 2021 Annual Conference Inspired by Nature – Inspiré par la Nature

26-29 May 2021

TALOYOAK, NUNAVUT – SEWAGE TREATMENT FEASIBILITY STUDY Johnson, K1,4, Browne, D2 1

EXP, Canada Government of Nunavut, Canada 4 ken.johnson@exp.com 2

Abstract: The Hamlet of Taloyoak in the Kitikmeot region of Nunavut utilizes trucked water distribution, and trucked wastewater collection to provide the community with water services. The wastewater is currently discharged into a natural two pond system for passive wastewater treatment, which flows through a natural wetland before discharging into the ocean.

Concerns were raised by regulators and the community about this wastewater strategy, and in response to these concerns, the Government of Nunavut initiated a wastewater feasibility study to investigate alternative locations and alternative processes for the development of an engineered system. Six potential locations for a new facility were investigated, and four of the sites were screened from future consideration. An advanced reconnaissance program was completed on the two remaining sites which included a topographic survey, a geotechnical investigation, an ecological investigation of the wetland. This additional site information was applied to an analysis for the development of a wastewater system on the sites, along with the potential treatment processes, that included a passive lagoon system, an aerated lagoon system and a mechanical treatment system. A passive facultative lagoon system with a single cell lagoon and supplemental wetland system was selected as the most appropriate technology that would meet the effluent quality standards in the community’s water licence. The screening of the potential sites favoured Sites 3 and 4, and ultimately Site 4 was selected for the facility.

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INTRODUCTION

The Hamlet of Taloyoak is located on the Boothia Peninsula approximately 1,300 kilometers west of Iqaluit and 1,200 kilometers northeast of Yellowknife. Taloyoak had a population of approximately 1,029 in 2016, and this population is expected to grow over the next 20 years to reach a population of approximately 1,413 in 2040.

Wastewater from the community is currently trucked and discharged to a natural (non-engineered) series of ponds approximately 2.5 Kilometers to the west of the community. Pond one has a surface area of approximately 1.6 Ha, which is connected to Pond 2 by a 20-meter-wide channel. Pond two has a surface area of approximately 3.1 Ha, and ultimately discharges to a natural wetland system to the south, which flows into Spence Bay, which is within the St Roch Basin. The wastewater storage volume provided by the two ponds is unknown.

The pond system has no flow control structures, so it operates as a continuous discharge facility in the summer months. During the winter months, freezing of the ponds causes the discharge to stop. From a wastewater process perspective, the ponds would be expected to operate as a continuous discharge facultative lagoon system during the summer months, and a sedimentation lagoon system during the winter months. It would be expected that most of the solids would accumulate in Pond one.

Concerns have been raised with the current wastewater management strategy. More specifically since the ponds do not have any flow control structures, there is a concern that the current natural series of GEN411 - 1

ponds does not have capacity to store the current and future annual wastewater generation from the community.

There are also concerns associated with the discharge into the natural wetlands adjacent to the ponds.

There are no flow control structures to manage either the timing or rate of discharge from the ponds into the wetlands. In response to the various concerns arising from the current wastewater facilities, the Government of Nunavut, commissioned a wastewater treatment feasibility study.

Figure 1. Existing Taloyoak community infrastructure.

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SYSTEM REQUIREMENTS

The proposed sewage treatment facility must meet the long-term needs of the Hamlet, as well as the regulatory requirements of the Hamlet’s water license. The design horizon for the Taloyoak sewage lagoon was set 20 years ending in 2040 based upon design guidelines for Arctic lagoons. The 2016 population of the community was 1030 and the estimated population in 2040 is 1410.

The sewage generation for the purposes of design is based upon the recorded water use in the community. The recorded water use in Taloyoak over a three-year period from 2017 to 2019 (47,733,866 L in 2017, 47,747,464 L in 2018 and 46,502,454 Litres (L) in 2019) was on average 47,327,000 L per year. Based upon a population of 1029 people (2016), the per capital water use is 126 Litres/capita/day (L/c/d). Based upon the 2040 population of 1410, the annual sewage generation is estimated to be 65,000 m3.

Several wastewater treatment processes were considered for the community. These processes included passive facultative lagoon treatment, aerated lagoon treatment and mechanical treatment. Aerated lagoon treatment and mechanical treatment were screened from further consideration because of the challenges associated with capital and operation and maintenance costs, which are considerably higher than a passive facultative lagoon system in the Arctic. Another importance consideration for the screening of aerated lagoon treatment and mechanical treatment are the human resource requirements for operation in the Arctic, particularly for the mechanical treatment system. It is also anticipated that GEN411 - 2

regulatory requirements for treated effluent can be achieved without the use of aerated lagoon treatment and mechanical treatment.

The configuration selected for the passive facultative lagoon was a single cell, which applies retention of the sewage for 10 to 12 months before discharge into a supplementary wetland treatment system. Since the Government of Nunavut is currently engaged in a process through the community water license to increase the effluent quality regulatory requirements for this wastewater treatment system, a conservatively low effluent quality standard was applied to this design – specifically, 45 mg/L BOD5, 45 mg/L Total Suspended Solids, 1.25 mg/L un-ionized ammonia, and 1x104 CFU / 100 mL Fecal Coliforms at the downstream end of the wetland. It should be noted that, based on research facilitated by the Government of Nunavut, effluent criteria of 120 mg/L BOD5, 120 mg/L Total Suspended Solids, and 1.25 mg/L un-ionized ammonia are environmentally-appropriate effluent discharge criteria to marine water bodies within the Territory of Nunavut.

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REVIEW OF POTENTIAL SITES

A total of six wastewater treatment facility sites, 5 new sites and the existing lagoon, were identified, and investigated.

Site 1 was screened from further consideration because of the upstream drainage area, which would require the development of a substantial drainage control measures. The site also has a limited opportunity to develop a wetland for supplemental treatment, and the community expressed a strong sentiment against the site because of its proximity to the community cemetery.

Site 2 was screened from further consideration because of the potential to adversely impact the sand pit and community use in the area. The site also was expected to have challenges with construction of a wetland.

Site 5 was screened from further consideration because of the anticipated challenges of road construction over potentially unsuitable ground. The site would also require the construction of a new wetland, and the require a new discharge point to the sea.

Taloyoak

Spence Bay

Figure 2. Wastewater sites considered in Taloyoak.

The new two sites recommended for further assessment and that were subsequently approved by Hamlet Council were the focus of the feasibility study. The two sites, Site 3 and Site 4, along with the existing lagoon, were retained for further consideration due to their potential for developing a suitable facility and their opportunity to incorporate the existing wetland and ocean discharge point.

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SITE #3

Potential Site #3 is located approximately 3 km from the community and 700 m from the runway, immediately east of the existing lagoon site. The proximity of the site to the airfield is not a concern in association with the airport zoning because the airport zoning regulations for Taloyoak do not exclude the development of facilities that could attract wildlife. Development of this site would include the construction of an engineered single lagoon cell, and vehicle access would be achieved through the construction of a short access road from the existing truck turn-around pad. Discharge from the lagoon could be directed into the existing lagoon, followed by supplemental treatment in the existing wetland. The site contains a seasonal stream that bisects the site, which would require consideration of runoff diversion around the site.

The site is overlain by tundra, while surficial boulders and soil depths are reported between 0.8 and 3.5 meters over most of the site. The drainage course, which transects the eastern portion of the site, overlies saturated soil. The soils in northern half of the site were also noted as having high moisture content. High moisture content suggests potential for subbase degrading from ice lenses melting and the potential for significant settlement with time in any earth structure.

Development of a lagoon on Site 3 may also require the removal of ice-rich soil and replacement with thaw stable material, as a measure to avoid thaw settlement due to permafrost degradation. It is further anticipated that there will be a requirement for the redirection of the drainage course and stabilization of the flow channel by removal, and replacement of the underlying saturated soil.

Figure 3. Final selected sites with development areas for sewage lagoon.

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SITE #4

Potential Location #4 is located approximately 300 m west of the existing sewage truck turnaround on the opposite side of the existing lagoon. This site is approximately 600 m from the runway. The proximity of the site to the airfield is not a concern in association with the airport zoning because the airport zoning regulations for Taloyoak do not exclude the development of facilities that could attract wildlife.

Development of this site would require the construction of an engineered lagoon cell and construction of a new access road. Discharge from the lagoon could be directed into the existing lagoon, followed by supplemental treatment in the existing wetland.

The site is overlain by tundra, with surficial boulders. It is reported that most of the site is well drained with no evidence of contained moisture. Soils are reported as sand to silty sand with gravel and occasional cobbles and boulders, and soil depth is reported as approximately 1 meter to bedrock. The presence of

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granular materials on the site and the proximity of bedrock suggests that significant thaw settlement of any earth structures on the site is not anticipated.

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WETLAND TREATMENT

Based upon the anticipated performance of the retention lagoon, it will not provide a discharge that is compliant with the ocean discharge criteria, without additional supplemental treatment. Wetland systems are an effective means of achieving this supplemental treatment. A significant number of Nunavut communities make use of wetlands for supplemental treatment of a lagoon discharge.

The ecological assessment of the existing wetland was conducted in July 2015 and noted that the wetland is achieving some improvement of the quality of the existing lagoon effluent. It was further noted that rehabilitation of the existing sewage system was required, and the recommended scope of rehabilitation included the existing wetland.

As part of the detailed design of the lagoon and wetland systems, the development of a wetland model specific to the wetland area will provide explicit estimates of the removal performance of fecal coliforms, suspended solids, and nutrients.

Figure 4. Sewage wetland in Taloyoak

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ANTICIPATED LAGOON PERFORMANCE

The removal mechanisms within a facultative lagoon include both physical and biological processes. The physical process of sedimentation will remove BOD5 and suspended solids through settling. The typical removal rates of 35% and 65% of BOD5 and suspended solids, respectively, can be obtained through primary sedimentation, and these values for removal are consistent with the demonstrated performance of a primary lagoon in Iqaluit. This is anticipated to be a conservative estimate because other Nunavut-specific cold climate studies have reported BOD5 in the range of 25 to 180 mg/L and Total Suspended Solids ranging from 25 to 115 mg/L for treatment from a single cell lagoon.

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Over winter the lagoon will be covered by a significant layer of ice, and therefore, the only treatment process that may occur is sedimentation. In early summer no significant improvement in quality is anticipated during the period when the ice on the lagoon thaws. It is further anticipated that decanting of lagoon contents may start in August and should not start any later that early September in order to take advantage of the treatment process that can occur through an active wetland.

The period, over which biological improvements will occur, is estimated to be 45 days, which is consistent with the observed performance of the Iqaluit lagoon for effluence BOD5 reduction in the period between of July, August, and September. It is further assumed that the lagoon contents will warm to 5⁰C over this period. The BOD5 in the decanted effluent is conservatively estimated at approximately 100 mg/L at the end of this 45-day period.

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ANTICIPATED WETLAND PERFORMANCE

The wetland downstream of the existing lagoon has an area of approximately 7.5 ha. The wetland is transected by a meandering, and slow-moving stream flowing in the north to south direction. Not all the wetland area may be incorporated into the wetland treatment activity, but the area may be maximized with the use of berm structures to disperse the flow and reduce the channelization. The anticipated performance of the wetland is presented in Table 1. The performance estimates for the wetland were based upon local studies that were benchmarked against an extensive data base of wetland performance information presented for CBOD in Figure 5.

TABLE 1 Anticipated Wetland Performance Parameter

Forecast mg/l & CFU/100 mL (E.coli)

TSS

13

CBOD

37

NH3-N

0.21

TP

0.47

E.coli

181

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Figure 5. Wetland performance for CBOD reduction.

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LAGOON SCHEMATIC DESIGN

The recommended schematic design of a sewage retention lagoon is presented in Figure 6. The lagoon is 260 metres long and 160 metres wide and operates with a 1 metre freeboard. The berm structures have recommended slopes of 3.5 :1 on the exterior, and 3:1 on the interior, and the lagoon will include a synthetic liner system. The working depth of the lagoon is 2 metres, with an additional sludge zone of 1 metre. The discharge system for the lagoon is a fuel driven pump system that pumps over the berm into the existing pond and wetland treatment system.

Figure 6. Site 4 Schematic lagoon design GEN411 - 7

10 CONCLUSIONS AND RECOMMENDATION 1. An initial list of 6 candidate sites for a wastewater facility was identified. Following an initial site review this list was screened to include only Site 3 and Site 4.

2. It is anticipated that a lagoon and wetland treatment system will provide an effluent that meets the effluent quality requirements.

3. The application of a 10 to 12-month retention lagoon system with impermeable berms and active (pumped) decanting is the most appropriate treatment system.

4. A minimum lagoon volume of 65,000 m3 is required. This is in addition to allowances for freeboard and sludge storage.

5. Alternative 4 is recommended for advancing to detailed design.

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