Re: Searchmont Ski Resort –…

Re: Searchmont Ski Resort – Proposed Wastewater Treatment Plant (WWTP) – Submission to the Environmental Registry of Ontario
To the Ministry of the Environment, Conservation and Parks,
I am submitting this comment in response to the proposed wastewater treatment plant (WWTP) for the Searchmont Ski Resort. These concerns are based on a summary of findings from an independent wastewater treatment expert who reviewed the design brief.
The expert concluded that while the proposed treatment technology is commonly used in Ontario and can perform well, several important design assumptions appear to be incomplete or underestimated. These issues could / would affect the plant’s ability to reliably meet its effluent limits and protect the sensitive receiving watercourse.
Below is a summary of our understanding of the key concerns the expert identified and the considerations and calls to action we are asking the MECP to consider carefully:
1) Concerns About Underestimated Influent Strength and Commercial Wastewater Impacts
The Design Brief describes the influent as “typical domestic wastewater.” However, based on the concentrations presented in Table 5 of the report, the proposed influent characteristics align more closely with weak to medium strength domestic sewage according to standard wastewater literature. The report does not explain whether these values were derived from actual monitoring at the existing facility or whether they are purely assumed. This lack of clarity is concerning given the nature of the proposed development.
A significant portion of the projected wastewater flow—approximately half—will originate from commercial uses, including restaurants and a conference centre. These types of facilities are well documented to produce wastewater with substantially higher concentrations of:
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· Total Suspended Solids (TSS)
· Biochemical Oxygen Demand (BOD)
· Total Kjeldahl Nitrogen (TKN)
· Total Phosphorus (TP)
· Fats, Oils, and Grease (FOG)

Commercial restaurant wastewater can have BOD concentrations in the several hundreds to thousands of mg/L, depending on food type, cooking practices, dishwashing procedures, and grease management. In contrast, the design basis used in the report assumes an influent BOD of only 110 mg/L, which is typical of weak domestic sewage and does not reflect the expected contribution from commercial kitchens.
The expert review concluded that the influent concentrations used by the proponent and Napier-Reid are likely underestimated for a facility with this level of commercial activity. If 50% of the daily flow originates from restaurants and food service operations, all influent design concentrations (BOD, TSS, TKN, TP, FOG) should be re-evaluated and increased to reflect the higher strength wastewater expected from these sources.
Underestimating influent strength has direct implications for:
· Nitrification performance and the ability to meet ammonia limits
· Aeration requirements and blower sizing
· Alkalinity demand
· Sludge production rates
· SBR cycle timing and tank sizing
· Tertiary filtration loading
· Overall treatment reliability

If actual TKN concentrations are higher than assumed, the plant may not achieve the required ammonia removal, and the treatment equipment may be undersized for real-world conditions.
Given the sensitivity of the receiving watercourse and the importance of accurate influent characterization, I respectfully request that MECP require the proponent to:
1. Clarify the basis for the influent concentrations used in the design (measured data vs. assumptions).
2. Reassess influent strength to account for the substantial contribution from restaurants and commercial kitchens.
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3. Demonstrate that the treatment system is adequately sized for realistic BOD, TSS, TKN, TP, and FOG concentrations.

These steps are necessary to ensure the WWTP is designed to handle the actual wastewater characteristics expected from the proposed development.
2) Peak Flows May Be Higher Than the Design Assumes
The design uses a peaking factor of 2.0, but existing data from the resort shows peaks closer to 2.0–2.4, especially on weekends and holidays.
Without flow equalization, underestimating peak flows could lead to hydraulic overloading and reduced treatment performance during busy periods.
The design proposes an average daily flow (ADF) of 180 m³/day and a peak daily flow of 360 m³/day, which represents a peaking factor of 2.0. For a resort facility with highly variable occupancy — including weekends, holidays, and seasonal surges — a peaking factor of 2.0 appears low. Resorts typically experience sharp, short-duration spikes in water use, and the expert review noted that a higher peaking factor would be more realistic for this type of facility.
Based on the existing flow data already collected by the proponent, the actual peaking factor appears to range from approximately 2.0 to 2.4. This means the design is using the lowest end of the observed range, rather than the upper end that would provide a margin of safety. Underestimating peak flows can lead to hydraulic overloading of the SBRs, reduced settling performance, increased solids carryover to filtration, and reduced UV disinfection effectiveness.
Given the sensitivity of the receiving river and the importance of accurate design flows, I request that MECP require the proponent to justify the selected peaking factor and demonstrate that the plant can reliably handle peak flows at the upper end of the observed range (2.4), not just the minimum value.
3) Concerns About Design Flows, OBC Values, and Flow Monitoring
The proposed design flows in Table 3 of the Kresin Design Brief reference the Ontario Building Code (OBC) as the basis for flow generation rates. While the OBC values used for the restaurant and conference room components appear accurate, it is not clear where the value of 225 L/bed for the hotel component was derived. This is not an OBC value. Under the OBC, the applicable design flows are:
· 500 L/person for a resort hotel
· 250 L/room for a regular hotel/motel
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The design brief does not explain why a non-OBC value (225 L/bed) was selected, nor does it justify why a lower value is appropriate for this facility. This is a significant concern because OBC values represent peak or maximum day flows, not average day flows. Since the proposed design does not include any up-front flow equalization, the accuracy of both the average and peak design flows becomes critical to ensuring the plant can reliably handle real-world peak conditions.
If the development is phased, detailed flow monitoring will be essential to verify actual average and peak flows. This is normally a standard ECA condition requiring the owner to track and report daily flow values. However, the design brief does not specify how daily flows will be measured.
The Napier-Reid package appears to include a flow meter as part of the tertiary treatment equipment, but this meter is located after the treatment process. A post-treatment flow meter does not represent the true influent entering the plant from the resort and therefore cannot be used to verify whether influent assumptions were correct or whether peak flows are being exceeded.
To ensure accurate flow tracking, the proponent should install a flow meter on the raw/influent sewage pumping station, where all wastewater first enters the system. If such a meter is already included in the lift station package, it is not clearly shown in the available drawings, and it would not typically be included unless explicitly specified.
Given the sensitivity of the receiving watercourse and the importance of accurate design flows, I request that MECP require the proponent to:
1. Justify the use of 225 L/bed and explain why OBC-specified values were not used.
2. Demonstrate that the design flows adequately capture peak conditions, especially in the absence of equalization.
3. Include influent flow monitoring at the raw sewage pumping station to ensure accurate tracking of actual flows entering the plant.

These steps are necessary to ensure the design is protective, robust, and based on defensible flow assumptions.
4) Technology Is Proven, but Performance Depends on Accurate Design Inputs and Proper Operation
From a high-level perspective, the proposed treatment technologies are well-established and capable of meeting the effluent targets if the design assumptions are accurate. Sequencing Batch Reactors (SBRs) are a reliable and proven biological process for BOD
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removal and nitrification, and Napier-Reid has a long track record of successfully implementing this technology over the past 25 years.
However, the expert review emphasized that the ultimate performance of the plant will depend heavily on the accuracy of the design flow and influent quality assumptions. As noted in earlier comments, several influent parameters—particularly BOD, TSS, and TKN—appear to be underestimated given the significant contribution of wastewater from restaurants and commercial kitchens. If the plant receives higher or different influent strength than what the design is based on, the system may experience difficulty meeting its effluent limits, especially for ammonia.
In addition, the expert noted that plant operations will play a major role in performance. The way the facility is operated and maintained by the owner and their contracted wastewater operator will directly influence effluent quality. Even proven technologies can underperform if influent assumptions are incorrect or if operational oversight is insufficient.
Given these factors, I request that MECP require the proponent to:
1. Reassess influent flow and loading assumptions to ensure the design basis reflects realistic conditions for a resort with substantial commercial wastewater contributions.
2. Demonstrate that the treatment system is adequately sized to handle higher-strength influent if actual conditions exceed the assumed values.
3. Provide an operations and monitoring plan that ensures the system will be properly managed to achieve consistent performance.

These steps are necessary to ensure that the plant’s proven technologies can reliably meet effluent targets under real-world operating conditions.
5) Phosphorus Removal Technology Is Proven, but Design Inputs Must Be Re-Evaluated
The proposed phosphorus removal strategy—chemical precipitation followed by filtration—is a well-established and widely used treatment approach in Ontario. While many facilities historically used sand filters, cloth disc filters such as those proposed here are also proven technologies and can achieve comparable performance with a smaller footprint. The effluent phosphorus limits proposed for this facility are stringent, but with a properly designed and operated system, they are technically achievable.
The expert review provided two relevant Ontario examples using similar Napier-Reid SBR systems with chemical precipitation and filtration:
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· Havelock WWTP
o Technology: Napier-Reid SBR + chemical precipitation + sand filtration
o Dry-season TP limit: 0.14 mg/L
o 2020 performance: 0.07 mg/L average TP
o Operating at ~65% of rated capacity

· Teeswater-Formosa WWTP
o Technology: SBR + chemical precipitation + sand filtration
o TP objective: 0.1 mg/L
o TP limit: 0.15 mg/L
o 2024 performance: 0.1 mg/L average TP
o Operating at ~74% of rated capacity

These examples demonstrate that the proposed effluent phosphorus limits are theoretically achievable with this type of treatment process.
However, the expert emphasized that achieving these limits depends heavily on the accuracy of the influent flow and concentration assumptions used in the design. As noted in earlier comments, the influent BOD, TSS, TKN, and TP values appear to be underestimated, particularly given that approximately half of the wastewater flow will originate from restaurants and commercial kitchens, which are known to produce significantly higher-strength wastewater.
If influent concentrations are higher than assumed, this will directly affect:
· chemical dosing requirements
· sludge production
· filtration loading
· SBR cycle performance
· the plant’s ability to consistently meet low TP limits

For these reasons, I respectfully request that MECP require the proponent to:
1. Reassess influent concentrations, particularly BOD, TSS, TKN, and TP, to reflect the substantial contribution from commercial food service operations.
2. Demonstrate that the phosphorus removal system is adequately sized for realistic influent conditions.
3. Confirm that the proposed filtration system can reliably meet the effluent TP limits under peak flow and peak loading scenarios.
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These steps are necessary to ensure that the phosphorus removal system performs as intended and that the receiving watercourse is adequately protected.

6) Buoyancy Control and the Need for Watertight Construction

The design appropriately includes anchoring of the lift station and tanks to protect against buoyancy, which is necessary given the shallow groundwater conditions at the site. However, the expert review noted that watertightness of all buried tanks and piping is equally important and is not addressed in the design brief.
If tanks, joints, or piping are not fully sealed, groundwater infiltration can enter the system, which can:
· significantly increase hydraulic loading on the treatment plant
· reduce treatment performance
· compromise SBR cycle timing
· increase sludge production
· reduce the effectiveness of tertiary filtration and UV disinfection

Even though MECP does not typically regulate construction-level details such as sealing methods, excess infiltration is an operational and performance risk that can directly affect the plant’s ability to meet its effluent limits. Given the shallow groundwater table at this site, watertight construction is essential to prevent inflow and infiltration from overwhelming the system.

I respectfully request that MECP require the proponent to:
1. Address watertightness of all buried tanks and piping in the detailed design.
2. Demonstrate that the system is protected against infiltration, especially during periods of high groundwater.

These steps are necessary to ensure the WWTP can operate reliably and maintain compliance under real-world site conditions.

7) Winter Temperatures, Insulation, and Biological Treatment Performance
The design brief does not mention insulation of tanks or process components, aside from noting in the Napier-Reid documentation that insulation is excluded from their scope.
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Insulation is an important consideration for maintaining wastewater temperatures within the biological treatment system. Colder temperatures slow down biological processes, including BOD removal and nitrification, which could affect the plant’s ability to meet effluent limits—particularly ammonia.
Physical and chemical processes associated with solids removal and phosphorus removal are generally less sensitive to cold temperatures, provided that equipment is protected from freezing. However, the biological processes in the SBRs are temperature-dependent, and maintaining adequate wastewater temperature is essential for consistent performance.
The expert review noted that Napier-Reid’s design calculations do consider both winter and summer conditions, including biological treatment performance at wastewater temperatures as low as 5°C. If the tanks are buried and insulated, achieving a winter wastewater temperature of approximately 5°C is reasonable, and the modelling appears to appropriately account for the process implications of winter conditions.
However, because insulation is not described in the design brief, it is unclear how the proponent intends to maintain the temperatures assumed in the modelling. Without insulation or equivalent construction measures, actual winter temperatures could fall below the design basis, potentially compromising biological treatment performance.
I respectfully request that MECP require the proponent to:
1. Clarify how wastewater temperatures will be maintained to match the assumptions used in the Napier-Reid design calculations.
2. Confirm whether insulation or other thermal protection measures will be included in the detailed design of buried tanks and process components.
3. Demonstrate that the plant can reliably achieve the required biological treatment performance under realistic winter operating conditions.

These steps are necessary to ensure that the winter temperature assumptions used in the design are achievable and that the plant will perform as intended throughout the year.

8) UV Disinfection Limits and the Need for Redundancy
The proposal includes UV disinfection for pathogen removal, which is a well-established and standard technology widely used in Ontario. The proposed effluent limit of 200 CFU/100 mL is consistent with many ECAs; however, the expert review noted that several
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comparable facilities in Ontario operate under more stringent limits, typically in the range of 100–150 CFU/100 mL. Based on the expert’s experience, an objective of 100 CFU/100 mL would be more consistent with similar ECAs, although the final limit should reflect the sensitivity of the receiving watercourse.
The expert also noted that well-operated SBR + filtration + UV systems routinely achieve far better performance than the proposed limit. For example:
· Havelock WWTP and Teeswater-Formosa WWTP, both using similar Napier-Reid SBR systems with chemical precipitation and filtration, regularly achieve <10 CFU/100 mL.
These examples demonstrate that significantly lower pathogen levels are achievable with this type of treatment process.
However, the proposal includes only a single UV disinfection train sized for maximum flow. This creates a single point of failure. If the UV unit requires maintenance or experiences an equipment issue, the plant would have no ability to disinfect effluent, which could result in non-compliance and increased pathogen loading to the receiving river.
To improve reliability and ensure continuous disinfection, the expert recommended considering two parallel UV units. This would allow one unit to remain in operation while the other is offline for maintenance or repair.
Given the sensitivity of the receiving watercourse and the importance of reliable pathogen control, I respectfully request that MECP require the proponent to:
1. Re-evaluate the proposed effluent E. coli objective and limit, considering that similar facilities routinely achieve <10 CFU/100 mL.
2. Assess whether a lower objective (e.g., 100 CFU/100 mL) is more appropriate for this site.
3. Provide redundancy in the UV system, such as two parallel UV trains, to ensure continuous disinfection during maintenance or equipment downtime.

These steps are necessary to ensure the WWTP can reliably meet pathogen removal requirements and protect the receiving watercourse under all operating conditions.
9) Ammonia Limits, Nitrification Capacity, and Concerns About Underestimated Influent Nitrogen
The proposed summer ammonia limits for this facility are quite low. While these limits are technically achievable, the expert review emphasized that reliable nitrification
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performance depends heavily on the accuracy of the influent nitrogen assumptions used in the design.
A well-operated biological nitrification process can achieve total ammonia nitrogen (TAN) concentrations below 1 mg/L, and comparable facilities in Ontario routinely achieve even better performance. For example:
· Havelock WWTP and Teeswater-Formosa WWTP (both using similar Napier-Reid SBR systems) regularly achieve average effluent ammonia levels in the range of 0.1–0.2 mg/L.
These examples demonstrate that the proposed ammonia limits are achievable if the plant is designed based on accurate influent nitrogen concentrations and has sufficient aeration and alkalinity to support full nitrification.
However, the expert noted that the influent nitrogen concentration used in the design appears to be underestimated, particularly given the significant contribution of wastewater from restaurants and commercial kitchens. If actual influent TKN is higher than assumed, the plant may not have:
· adequate aeration capacity
· sufficient alkalinity
· appropriate SBR cycle timing
· enough biological volume

to achieve the required ammonia removal.
In the expert’s words:
“If the influent nitrogen concentration has been underestimated, modifications may be needed to the nitrification calculations/design.”
The expert also confirmed that alkalinity is essential for nitrification and that the Napier-Reid design appropriately includes chemical alkalinity addition if natural alkalinity is insufficient. However, the adequacy of this provision depends on the accuracy of the influent nitrogen assumptions.
Given the sensitivity of the receiving watercourse and the importance of meeting low ammonia limits, I respectfully request that MECP require the proponent to:
1. Reassess influent nitrogen concentrations, particularly TKN, to ensure the design basis reflects realistic conditions.
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2. Demonstrate that aeration capacity, alkalinity supply, and SBR cycle design are sufficient to achieve full nitrification under peak loading conditions.
3. Confirm that the nitrification design has been evaluated for higher influent nitrogen scenarios, given the likelihood that commercial wastewater will increase nitrogen loading.
These steps are necessary to ensure the WWTP can reliably meet ammonia limits under real-world operating conditions.
10) Concerns About the Proposed Nitrate Limit and Unit Errors in the ACS
Nitrate is not typically included as an effluent parameter for surface-water discharges in Ontario. Nitrate limits are generally applied to groundwater discharges, not surface water, unless the receiving watercourse is extremely low-flow or highly sensitive. While it is not impossible for an ECA to include a nitrate limit in a surface-water context, it is unusual and requires strong technical justification.
The expert review also identified a technical issue in the assimilative capacity calculations: the proponent appears to have mixed nitrate-as-N and nitrate-as-NO₃ units. This is a common source of error, but it has important implications for interpreting water quality criteria.
Specifically:
· The CCME guideline of 13 mg/L applies to nitrate as NO₃.
· When expressed as nitrate-as-N, the equivalent value is 2.93 mg/L.
· The river data in the ACS is reported as nitrate-as-N, meaning the proponent should have compared it to 2.93 mg/L, not 13 mg/L.
Despite this unit error, the expert concluded that correcting the calculation would not change the overall outcome. The receiving watercourse has sufficient assimilative capacity according to the ACS so it’s unclear why a nitrate limit is imposed.
Given this, I respectfully request that MECP:
1. Review the nitrate unit conversion issue in the ACS to ensure the analysis is technically correct. Also are the other values used properly.
2. Explain why a nitrate limit is appropriate, given that nitrate is not a standard parameter for surface-water discharges and the corrected ACS indicates adequate assimilative capacity.