Duffin Creek Water Pollution Control Plant, Schedule C Class Environmental Assessment, Receiving Water Impact Assessment

Transcription

1 14 Abacus Road, Brampton Ontario, Canada. L6T 5B7 tel: (905) ; fax: (905) Mr. David Estrin Gowling LaFleur Henderson LLP 1 First Canadian Place, Suite King Street West, Toronto, Ontario. M5X 1G5 Dear Mr. Estrin: Reference: Duffin Creek Water Pollution Control Plant, Schedule C Class Environmental Assessment, Receiving Water Impact Assessment EcoMetrix Incorporated (EcoMetrix) issued a Gap Analysis 1 for the April 2006 version of the above referenced report. We have since received a revised report (the Report) of the same title dated September 2006, prepared by CH2MHill. We have reviewed the revised Report and conclude that the issues identified in the Gap Analysis remain unaddressed. The Report presents the findings of a receiving water impact assessment (RWIA) that was completed as part of the Class EA process as specifically required under Condition 7 of the Environment Minister s 2004 Order. This condition required appropriate analysis to avoid adverse impacts to nearby water users, municipal drinking water supplies, swimming beaches and aquatic habitats. The Ministry of Environment (MOE) provided specific terms of reference for the RWIA which required, among other things, consideration of Provincial Water Quality Objectives (PWQO), performance objectives for the diffuser, the physical size of the mixing zone, and overall environmental impacts. After reviewing the final Report, it is our opinion that there are significant deficiencies in the RWIA 2 which result in under-estimation and under-statement of the impacts of both the existing discharge limit as well as any future expansion for the Duffin Creek Water Pollution Control Plant (WPCP). These deficiencies prevent the Report from being used as a reliable receiving water impact assessment. Further, the Report focuses only on concentration limits and performance objectives for the diffuser, but neglects all other requirements of the MOE s terms of reference. The most significant of these neglected requirements is the impact of excess total phosphorus (TP) and unionized ammonia (UIA) on the Ajax beaches and waterfront, the Ajax Water Supply Plant (WSP) intake, and the environmentally sensitive habitats at the Duffin Creek Wetlands, which is a provincially significant wetland. 1 EcoMetrix Incorporated, July Appendix L to the Schedule C Class Environmental Assessment.

2 25 Mr. Estrin, Gowling Page 2 of 2 Reference: Duffin Creek Water Pollution Control Plant, Schedule C Class Environmental Assessment, Receiving Water Impact Assessment In our opinion, Condition 7 of the Minister s Order and the specific MOE terms of reference for the RWIA have not been met. However, even though impacts have been under-estimated in the Report, the modeling results nevertheless show that PWQOs for TP and UIA will not be met for significant times at the Ajax waterfront, the Ajax WSP intake and at the mouth of a provincially significant wetland at Duffin Creek. Had appropriate modeling been carried out, the peak concentrations and areal extent of the PWQO exceedance for TP and UIA would be substantially greater than reported. The Report acknowledges the exceedance of PWQO for TP will cause growth of nuisance algae but under-states its significance even though the Town of Ajax reports significant adverse impacts under the existing discharge limit. These impacts include excess growth of cladophora, which is a type of algae that grows on the bottom in nutrient rich waters. The cladophora turns the water a highly turbid green colour that is unpleasant for swimming or any other form of direct water contact. It also accumulates along the shoreline and creates an unpleasant odour as it decays. The sight and smell of the decaying algae severely impacts the aesthetic quality of the waterfront, beach areas and walking trails to the extent that residents no longer enjoy this valued resource. Based on these facts, the issues identified in our Gap Analysis remain unaddressed, and hence our original conclusions remain, which are: the impacts of the proposed expansion of the Duffin Creek WPCP are potentially under-predicted, based on an under-representation of the existing background contamination and an under-prediction of concentrations within the wastewater plume; accordingly, the water quality impacts at the Ajax shoreline and at the Ajax Water Supply Plant (WSP) intake have the potential to be greater than predicted in the Report. These unaddressed concerns are discussed in further detail in the attached addendum to our Gap Analysis. Additional concerns and issues are discussed in the original Gap Analysis. Yours truly, EcoMetrix Incorporated Bruce T. Rodgers, M.Sc., P.Eng. Principal

3 Duffin Creek Water Pollution Control Plant, Schedule C Class Environmental Assessment, Receiving Water Impact Assessment ADDENDUM TO THE 31 JULY GAP ANALYSIS 1.0 INTRODUCTION EcoMetrix Incorporated (EcoMetrix) issued a Gap Analysis for the April 2006 version of the above referenced report. We have since received a revised report (the Report 3 ) of the same title dated September 2006, prepared by CH2MHill. We have reviewed the revised Report and conclude that the issues identified in the Gap Analysis remain unaddressed. The Gap Analysis identified a number of serious deficiencies with respect to the receiving water impact assessment. These deficiencies raise questions concerning the degree of environmental protection provided under both the existing Certificate-of-Approval (C-of-A) for the Duffin Creek Water Pollution Control Plant (WPCP) as well as any future expansion. These deficiencies also raise questions concerning the accuracy of the modeling undertaken by CH2MHill to support the interpretation of potential environmental effect. Our original conclusions from our Gap Analysis remain, which are: the impacts of the proposed expansion of the Duffin Creek WPCP are potentially under-predicted, based on an under-representation of the existing background contamination and an under-prediction of concentrations within the wastewater plume; accordingly, the water quality impacts at the Ajax shoreline and at the Ajax Water Supply Plant (WSP) intake have the potential to be greater than predicted in the Report. Our main, unaddressed concerns are discussed in the sections below. Further concerns are discussed in greater detail in our Gap Analysis, which is appended to this letter. 3 The Report refers to Appendix L of the Duffin Creek Water Pollution Control Plant, Schedule C Class Environmental Assessment, Receiving Water Impacts Assessment. Ref

4 2.0 EXISTING WATER QUALITY ISSUES 2.1 Existing Conditions along the Ajax Waterfront As outlined in our Gap Analysis, an environmental assessment normally provides a thorough description of the environmental baseline condition. This was not done. If it had, it would conclude that the waterfront for the Town of Ajax is already severely impacted by elevated levels of bacteria and nutrients that have resulted in the degradation of the beach and waterfront areas. This impact is characterized by the thick accumulation of cladophora along the Ajax waterfront as illustrated in the photograph in Figure 1. Cladophora is a type of algae that grows on rocks and other hard substrates in nutrient rich waters. As shown in the photograph, the cladophora turns the water a highly turbid green colour that is unpleasant for swimming or any other form of direct water contact. It also accumulates along the shoreline and creates an unpleasant odour as it decays. The sight and smell of the decaying cladophora severely impacts the aesthetic quality of the waterfront, beach areas and walking trails to the extent that residents no longer enjoy this valued resource. FIGURE 1 Photograph taken on 26 June 2006 at Rotary Park Beach. The photograph shows the accumulation of cladophora and the resulting highly turbid, greenish waters along the shoreline. Ref

5 Field Survey of Cladophora and Total Phosphorus Cladophora is present throughout the nearshore of the Ajax waterfront, as demonstrated by the underwater video survey completed by The Toronto and Region Conservation Authority (TRCA) on 09 August Figure 2 illustrates the results from that survey and shows moderate to high densities of cladophora across the Ajax waterfront and extending offshore more than a kilometer. FIGURE 2 Density of Cladophora per station observed from under water video 09 August The TRCA also measured TP concentrations across the Ajax waterfront on 09 and 29 August The results are presented in Figure 3a and 3b, respectively. As shown, the concentration of TP along the shoreline at Rotary Park Beach was mg/l and mg/l on 09 and 29 August 2006, respectively, with concentrations in the range to mg/l measured further offshore. In comparison, the PWQO for TP is mg/l for protection against nuisance algal growth, and International Joint Commission has set an 4 TRCA, Water Quality Survey, Ajax Waterfront. Presentation from Mr. Bowen to Ajax Town Council, 25 September Ref

6 objective of mg/l (under the Canada-U.S. Great Lakes Water Quality Agreement) for protection of Lake Ontario. FIGURE 3a Measured Concentrations 5 of Total Phosphorus at Ajax Waterfront 09 August FIGURE 3b Measured Concentrations of Total Phosphorus at Ajax Waterfront 29 August Concentration measurements in µg/l µg/l = 1 mg/l. 6 TRCA, Water Quality Survey, Ajax Waterfront. Presentation from Mr. Bowen to Ajax Town Council, 25 September Ref

7 These elevated levels are not solely attributed to the Duffin Creek WPCP since other local sources have also been identified. However, the Duffin Creek WPCP is estimated to be by far the largest source of phosphorus to the waterfront under existing conditions. From our estimates, the Duffin Creek WPCP accounts for 360 kg/d of TP under the existing discharge of 360 MLD 7, in comparison to an estimate loading of 5 kg/d from Duffin Creek and 2 kg/d from all storm sewers combined. In addition to creating an aesthetic issue, the cladophora also attracts birds (as shown in the photograph in Figure 4) due to the feeding opportunities it provides. These birds are also attracted to the park by the open grasslands and beach areas, so cladophora is not the only reason why birds are abundant at Rotary Park Beach. These birds contribute to the elevated bacteria levels across the waterfront (which is confirmed through genetic testing of the bacteria at the waterfront). However, beach postings are based only on E. coli counts and do not distinguish between human and non-human sources. FIGURE 4 Photograph taken on 26 June 2006 at Rotary Park Beach. The photograph shows the many birds that flock to the waterfront to feed on the crustaceans that are associated with the cladophora. These birds contribute to the elevated bacteria levels across the waterfront. 7 MLD refers to Megalitres per day, which equals 1,000 cubic metres per day (m 3 /d). Ref

8 2.3 Predicted Total Phosphorus at Existing Discharge Limit The Report discusses TP under the existing C-of-A limit of 420 MLD from the Duffin Creek WPCP, and concludes that the TP concentrations exceed the PWQO of mg/l over a distance of 10 km or more along the shoreline and several kilometers offshore, as illustrated in Figure 5. The Report further acknowledges that these elevated levels of phosphorus may encourage growth of nuisance algae 8. Clearly this is in fact the case. As discussed in Section 4.0, the model predictions likely under-estimate the water quality impacts associated with the Duffin Creek WPCP. As a result, the peak concentration of TP and size of the impacted area are likely greater than that shown in Figure 5. FIGURE 5 Model prediction of Total Phosphorus for design flow of 420 MLD showing percent time exceeding PWQO of 0.02 mg/l Predicted Unionized Ammonia at Existing Discharge Limit The Report further demonstrates that the Ajax waterfront is impacted by elevated levels of unionized ammonia (UIA) under the existing C-of-A of 420 MLD. The PWQO for UIA is 0.02 mg/l for protection of aquatic life (and is acutely toxic at higher levels). The September version of the Report (Figure 6a) shows that the PWQO is exceeded 5% of the time (220 hrs) over a region extending 5 km alongshore, and the April version of the Report (Figure 6b) shows the PWQO is exceeded 1% of the time (50 hrs) over a considerably larger area extending along the shoreline more than 10 km and offshore nearly 2 km. 8 The Report, Section 5.3.1, Page The Report, Section 5.3.1, Page 5-8, Figure 5.3. Ref

9 FIGURE 6a Model prediction of Unionized Ammonia for design flow of 420 MLD 10. Shows the percent time exceeding PWQO of 0.02 mg/l (September version). FIGURE 6b Model prediction of Unionized Ammonia for design flow of 420 MLD. Shows the number of hours exceeding the PWQO of 0.02 mg/l (April version) 10 The Report, Section 5.3.1, Figure 5.1. Page 5.6 in September version and Page 5.5 in April version. Ref

10 The September version of the Report does not show the model results at the 1% level and therefore gives the false impression that the zone of non-compliance with the PWQO is smaller and does not contact the shoreline. As discussed in Section 4.0, the model predictions likely under-estimate the water quality impacts associated with the Duffin Creek WPCP. As a result, the peak concentration of UIA and size of the impacted area are likely greater than that shown in Figures 6a and 6b. 2.5 Classification of Ajax Waterfront as MOE Policy 2 The MOE established the PWQO to protect aquatic life and recreational uses of Ontario s surface waters. The MOE has also established policies to provide guidance on how to assess point source discharges in situations where water quality is better or worse than the PWQO. It is apparent from the field measurements and model predictions that the existing surface water quality across the Ajax waterfront does not meet the PWQO for at least TP and UIA, and possibly other water quality parameters (e.g., E. coli). As a result, and according to MOE policy, these waters are classified as Policy 2. In this situation, the MOE stipulates that the water quality shall not be further degraded and all practical measures shall be undertaken to upgrade the water quality to the Objective 11. The Report acknowledges that the water quality across the Ajax waterfront does not comply with the PWQO, but it does not acknowledge that the waters are classified as Policy 2 nor does it comply with the requirements of the MOE policy. The Report does not identify measures to upgrade the water quality to the PWQO, and, proposes further degradation of water quality through expansion of the Duffin Creek WPCP. Assessment of cumulative effects is often required for Policy 2 waters in order to quantify the relative contribution from each identified source of pollution. This further requirement is also not addressed in the Report other than unsubstantiated statements suggesting birds and other local sources are the main contributors of pollution. Our findings suggest otherwise. The growth of nuisance cladophora (algae) that presently impacts the Ajax waterfront is directly related to the exceedance of the PWQO for TP caused by the existing discharge from the Duffin Creek WPCP. The aesthetic impairment caused by cladophora is severe and unacceptable to the residents of the Town of Ajax. By all accounts, the present level of impact is unacceptable, and any further exacerbation of the existing impact is also considered unacceptable. 11 MOE, Deriving receiving water based point source effluent requirements for Ontario Waters, Procedure B-1-5, PIBS#3302. Ref

11 3.0 POTENTIAL FUTURE WATER QUALITY ISSUES 3.1 Conclusions Regarding Environmental Impacts The Report suggests that the present environmental state of the Ajax waterfront is acceptable under the present C-of-A of 420 MLD, and that further expansion of the Duffin Creek WPCP is also acceptable without mitigation up to a flow of 560 MLD. At 560 MLD, the Report suggests mitigation may be required in the form of an outfall extension. We disagree with these conclusions and believe mitigation is required at present. As discussed above, the Town of Ajax considers the waterfront severely impacted by nuisance algae, and hence the existing discharge limit of TP from the Duffin Creek WPCP is not adequately protective of the environment. The aesthetic quality of the water and beach areas is so poor that people s enjoyment of the waterfront for swimming, sun bathing or even walking along the beach is impaired. As the Report shows, this impairment is directly related to the elevated levels of TP along the shoreline under the present discharge conditions for the Duffin Creek WPCP. The model also shows elevated levels of UIA that could be acutely toxic to fish and other aquatic organisms within the nearshore areas. These impacts are not acceptable under present conditions, and any further expansion of the Duffin Creek WPCP will only exacerbated these issues. Despite these realities, the Report erroneously concludes no potential for environmental effects under present conditions, and no potential for environmental effects up to 560 MLD. These conclusions are based entirely on a performance measure of 20:1 dilution 12 for the diffuser rather than on a meaningful assessment of environment effects. As specifically required under Condition 7 of the Minister s Oder, the RWIA was specifically required to assess the potential for adverse impacts to any nearby water users, nearby municipal drinking water supplies, swimming beaches and to avoid adverse impacts to aquatic habitats. Clearly, this requirement was not met or even considered, for if it had, the Report would have concluded severe impacts to the Ajax waterfront under both the existing and proposed future discharge limit for the Duffin Creek WPCP. 3.2 Predicted Total Phosphorus at 560 MLD Discharge Limit It is puzzling that the Report concludes no potential for environmental effects up to 560 MLD when the predictions of TP presented in the Report clearly exceed the PWQO over a very large area. As presented in Figure 7, the peak concentration of TP at the surface is greater than mg/l (6.7 times greater than the PWQO of 0.02 mg/l), and the area exceeding the PWQO extends beyond the 8.5 by 3 km waterfront area shown in the figure. The Report concludes that the PWQO exceedances (for TP) are infrequent and may contribute to some but not a substantial amount of algae bloom formation 13. This conclusion is made without identifying other sources of TP or the respective contribution from each source. Yet, the model results for the 420 MLD flow condition show frequent 12 The Report, Section 5.2.1, Page The Report, Section 6.3, Page Ref

12 exceedance of the PWQO that clearly explain the observed growth of nuisance algae throughout the Ajax waterfront under present conditions. From our estimates, the Duffin Creek WPCP accounts for 560 kg/d of TP under the 560 MLD flow scenario, in comparison to an estimate loading of 5 kg/d from Duffin Creek and 2 kg/d from all storm sewers combined. This suggests the Duffin Creek WPCP is in fact the most significant source of TP to the Ajax waterfront, and therefore responsible for a substantial amount of the algae bloom formation. As discussed in Section 4.0, the model predictions likely under-estimate the water quality impacts associated with the Duffin Creek WPCP. As a result, the peak concentration of TP and size of the impacted area are likely greater than that shown in Figure 7. FIGURE 7 Model prediction of surface peak Total Phosphorus levels at 560 MLD 14 (Note: the contour for the PWQO of 0.02 mg/l TP extends beyond the bounds of the figure). 3.3 Predicted Unionized Ammonia at 560 MLD Discharge Limit The Report also predicts exceedance of the PWQO for UIA over a very large area even at the more restrictive discharge limit of 0.1 mg/l UIA. As presented in Figure 8, the peak concentration of UIA at the surface is greater than 0.05 mg/l (2.5 times greater than the PQWO of 0.02 mg/l), and the area exceeding the PWQO extends more than 8 km along the shoreline and more than 3 km offshore. The Report attempts to argue that decay of ammonia will reduce the stated impact of UIA, however, this is not an appropriately conservative assumption since the bacteria responsible for the decay process generally take several days to form. The Report further attempts to argue that the PWQO of 0.02 mg/l for UIA is not appropriate since the 14 The Report, Section 5.3.2, Page 5-11, Figure 5.7. Ref

13 exceedances are of short duration. However, this is also not an appropriately conservative assumption since the source is continuous and the PWQO is based on a standard 96-hr LC 50 toxicity test 15 which is also of short duration relative to the exceedances. As discussed in Section 4.0, the model predictions likely under-estimate the water quality impacts associated with the Duffin Creek WPCP. As a result, the peak concentration of UIA and size of the impacted area are likely greater than that shown in Figure 8. FIGURE 8 Model prediction of surface peak Unionized Ammonia levels at 560 MLD 16 from September version of the Report. 3.4 Criteria for the Receiving Water Impact Assessment The Report rationalizes the need for mitigation at 560 MLD based on initial dilution requirements rather than environment effects. As stated in the Report, modeling results show that the existing outfall has a capacity of up to 560 MLD, while still meeting the MOE minimum dilution objectives of 20:1 17. It is important to note that the 20:1 dilution is a minimum requirement only, and only pertains to the performance objectives of the diffuser. The MOE reserves the right, and has the responsibility, to impose additional requirements to ensure adequate protection of the environment. As outlined in the original Terms of Reference for the plume delineation, key considerations should have included, among other things, consideration of PWQO, performance objectives for the diffuser, the physical size of the mixing zone, and overall environmental impacts. These considerations are described below. 15 MOE, Rationale for the Establishment of Ontario s Provincial Water Quality Objectives, page The Report, Section 5.3.2, Page 5-10, Figure The Report, Section 5.2.1, Page 5-2. Ref

14 1. The discharge diffuser should provide a minimum initial dilution of 20:1. This is a performance requirement for the diffuser and does not ensure protection of the environment. The Report predicts an initial dilution of 22:1 under the present C-of-A limit of 420 MLD and an initial dilution of 20:1 at a discharge limit of 560 MLD. However, the Report concludes mitigation is required at this higher flow but not at the present limit of 420 MLD. This is not a rational conclusion since, in all practical terms, the difference between 22:1 and 20:1 dilution is purely theoretical and based on a model that is not sufficiently accurate to resolve such a small difference. If mitigation is required at 560 MLD, then it is also required at 420 MLD based on the logic presented in the Report. 2. The diffuser should be capable of achieving the required mixing over the full range of effluent flows and ambient conditions commencing with the start-up of the upgraded WPCP. This is also a performance requirement for the diffuser. It requires that the minimum initial dilution of 20:1 be achieved under all conditions and at all times. This minimum requirement has not been achieved. The calculated 20:1 dilution at 560 MLD is based on an assumed current velocity of 4 cm/s and assumed water temperature difference of 8 o C, which do not account for the full range of ambient conditions. Under calm conditions, the Report estimates that the initial dilution is only 5:1 18 under the 560 MLD discharge scenario, which is significantly below MOE s minimum requirement of 20:1. As a result, the water quality within this area of initial dilution will be significantly poorer (by a factor of four) than the minimum requirement. Temperature differences up to 14 o C 19 are also identified although not discussed in the Report. These higher temperature differences will also reduce the initial dilution. 3. The PWQO should be met at the edge of the near field mixing zone. The mixing zone is a defined term in the MOE policy 20 and refers specifically to an area of water contiguous to a point source where the water quality does not comply with one or more of the PWQOs. As required by the policy, the mixing zone should: not be used as an alternative to reasonable and practical treatment; be as small as possible; and not interfere with other beneficial water uses, such as drinking water supply or recreation. These requirements of the MOE policy are not met as discussed further in the points below. 4. The mixing zone should be designed to be as small as possible. The defined mixing zone for the Duffin Creek WPCP extends approximately 10 km along the shoreline and approximately 3 km offshore under the present C-of-A of 420 MLD, and some unspecified larger area under the proposed expansion to 560 MLD. This exceedingly large mixing zone is one of the largest in the province, and definitely does not comply with the policy requirement to be as small as possible. Improved treatment of the wastewater, or redesign and relocation of the diffuser further offshore would reduce the size of this mixing zone. 18 The Report, Section 5.3.2, Page The Report, Appendix B, Section 2.1.2, Page 2-6, Figure MOE, Deriving receiving water based point source effluent requirements for Ontario Waters, Procedure B-1-5, PIBS#3302. Ref

15 5. As a minimum requirement, the near field mixing zone should be limited to half the distance between the offshore length of the outfall and the nearest shore. This minimum requirement is not met at either the present or proposed expanded discharge for the Duffin Creek WPCP. The mixing zone engulfs the shoreline across the Ajax waterfront over a distance of 10 km or more. 6. The mixing zone should not interfere with other water uses, such as water supply intakes, other effluent discharges, bathing beaches, fish spawning areas, or fish migration routes. This requirement is also not met. The mixing zone for the Duffin Creek WPCP extends across the intake for the Ajax WPCP thus it interferes with the drinking water supply for the township. The mixing zone also extends across the waterfront and is directly responsible for the excess growth of nuisance cladophora (algae) that has severely impacted the aesthetic quality of beach and waterfront areas to the extent residents no longer enjoy this valued resource. Furthermore, the mixing zone extends across the mouth of the Duffin Creek Wetland, which is a provincially significant wetland. 7. The effluent should not be acutely lethal to aquatic life. Compliance with this policy objective cannot be assured. The existing C-of-A for the Duffin Creek WPCP does not limit the ammonia concentration of the final effluent nor does it require the facility to demonstrate compliance through routine toxicity testing. Furthermore, the Report presents anticipated future compliance criteria for total ammonia of 10 mg/l during the summer and 20 mg/l during the winter which does not achieve the 0.1 mg/l UIA target recommended by the MOE. In our opinion, Condition 7 of the Minister s Order and the specific MOE terms of reference for the RWIA have not been met. The Report has not adequately considered the specific requirements for the RWIA. Even the required minimum initial dilution of 20:1 (Criteria #1) has not adequately considered variability of the ambient conditions, which results in a minimum initial dilution of only 5:1 21 (four times lower than the policy objective) under calm conditions. The exceedingly large mixing zone hardly complies with the other stated considerations, such as as small as possible, limited to half the distance (500 m) between the offshore length of the outfall and the nearest shore, or should not interfere with other water uses including the Ajax WSP, Rotary Park Beach or the Duffin Creek Wetland. Based on the above considerations from the original Terms of Reference for the plume delineation, there is no rational basis to delay imposing mitigation to the time flows reach 560 MLD since mitigation is already required under the present C-of-A limit of 420 MLD. 21 The Report, Section 5.3.2, Page 5-8. Ref

16 4.0 WATER QUALITY MODELING CONCERNS The Minister s 2004 Order specifically required the Region to conduct a detailed receiving water impact assessment as part of the Class EA process, and that the assessment shall include a mixing zone analysis using appropriate mathematical models to predict the plume delineation and various parameter concentrations within the plume under different effluent loadings and lake ambient conditions. As discussed in Sections 2 and 3, it is our opinion the Region has not fulfilled this Order since the assessment under-states the existing and potential future environmental impacts associated with the Duffin Creek WPCP, and does not address the specific terms of reference for the plume delineation. Furthermore, it is our opinion the mathematical modeling undertaken in support of the RWIA may under-predict the water quality impacts for the Duffin Creek WPCP. Our Gap Analysis described the basis for this opinion, however, the expressed concerns remain unanswered. These concerns are described in further detail in the Gap Analysis. The two main concerns are described below. These include lack of model calibration; and potential under-prediction of the water quality impact. 4.1 Model Calibration, Verification and Confidence Concerns Model calibration and verification is a process by which a model prediction is compared to measured data. Calibration provides a rational basis to adjust model parameters, whereby improving the accuracy of the prediction, and verification provides confirmation of the model prediction against an independent dataset. Together, calibration and verification builds confidence in the model if the model predictions compare well to the measured data. In the absence of calibration and verification, it is difficult to have confidence in the model prediction. Errors in model parameters or inappropriate assumptions can drastically affect the accuracy of the model prediction, and thereby drastically affect the conclusions drawn from these predictions. The Report claims the model has been calibrated, although this statement is misleading since calibration against measured water quality data is limited. The September version of the Report presents a comparison of measured and predicted ammonia concentrations at the Ajax WSP. As shown in Figure 9, the prediction with decay under-estimates the ammonia concentration throughout the six month simulation period, whereas the prediction without decay shows the same general magnitude as the observed but does not match the timing of the peaks. The Report concludes there are no correlations with the observed ammonia levels at the intake 22 which implies a poor calibration since no other source of ammonia is identified to explain the observed concentrations at the Ajax WSP. 22 The Report, Appendix B, Section 3.8.4, Page Ref

17 FIGURE 9 Comparison of Predicted and Measured ammonia concentration for the Ajax WSP 23 The Report also provides a comparison of measured and predicted temperature at the Ajax WSP, however, temperature is not necessarily relevant. The Report states that the lake is well-mixed from surface to bottom within the nearshore area extending from the discharge to the shoreline. Within this area, temperature does not vary as a result of vertical mixing (since the temperature is uniform from surface to bottom). As such, the calibration of temperature within this nearshore area is substantially based on parameters for heat transfer and not for the vertical dispersion of pollutants. (The concern is that the model is being used to predict the environmental impacts of a buoyant wastewater discharge, yet the Report does not demonstrate that the model is capable of accurately predicting the vertical dispersion of the buoyant plume. This is extremely important to the accuracy of the model since a buoyant plume tends to remain near the surface and at higher concentrations than a well mixed plume. The temperature calibration provided does not address this concern.) The Report also provides a limited comparison of measured and predicted current velocity for the period 21 September to 02 October 1993, however the Report only shows the best few days of prediction and does not show the full prediction. Overall, there is no basis to gain confidence in the model prediction, and if anything, a basis to conclude a poor prediction. The Duffin Creek WPCP has been operational for many years so data could have been collected to calibrate the model. Simple field investigations as completed this summer by the TRCA and as described in our Gap Analysis would provide data to calibrate and verify the model and hence build confidence in the prediction. 23 The Report, Appendix B, Section 3.8.4, Page 3-23, Figure Ref

18 4.2 Potential Under-prediction of the Water Quality Impacts The analysis of receiving water effects is made primarily using the Mike-3 hydrodynamic and water quality model. It is recognized that this model is highly sophisticated and is capable of simulating the complex three-dimensional distribution of velocity and water quality within the nearshore zone. However, it is also recognized that this model requires significant effort to ensure proper calibration and verification of the physical and biochemical processes simulated by the model. As discussed above, this has not been done. The model is not properly calibrated or verified against relevant water quality data, and therefore there is no basis to gain confidence in the prediction. As discussed in our Gap Analysis, various assumptions were made in the model implementation that are cause for concern. These assumptions all bias the prediction towards under-estimation of the potential water quality and environmental impacts. Several of these concerns have also been raised by the MOE and have been responded to by CH2MHill through additional modeling. However, the response only demonstrates the validity of the concern. These continued concerns are outlined in the sections below. Inappropriate Representation of the Buoyant Wastewater Plume As required of the Minister s Order, the RWIA was to use appropriate mathematical models to predict the plume delineation under different effluent loadings and lake ambient conditions. In our opinion, this was not done adequately and may bias towards an underprediction of water quality impact. The basis of the concern is best described through example. Figures 10a and 10b compare the predicted TP concentrations in the surface layer for two different assumptions regarding the initial mixing of the wastewater plume. The first assumption is based on a bottom source and the second assumption is based on a vertically distributed source. The assumed bottom source is presented in Figure 10a. It assumes that the warm wastewater enters at the bottom of the lake and then gradually mixes with the cooler ambient lake water. The model is relied upon to predict the initial dilution of the wastewater within the near-field zone. For this assumed bottom source, the model predicts an exceedance of the PWQO for TP (for 1200 hours) over a small area extending several hundred meters around the diffuser. In comparison, Figure 10b is based on the assumption that the warm wastewater rapidly rises through the water column due to buoyancy and can be mathematically represented by a vertically distributed source. For this assumed vertically distributed release, the model predicts an exceedance of the PWQO over an area extending 3 km long and nearly 1-km wide. This prediction is drastically difference than the model prediction based on an assumed bottom source. This comparison is very significant to the interpretation of the model results presented in the Report. The predictions in the Report are based on an assumed bottom source, which is Ref

19 the least conservative assumption. The most conservative assumption is that of a surface release (not shown) which is what is predicted using the CORMIX model. FIGURE 10a Model prediction of surface Total Phosphorus (as hours above PWQO) 24 with the discharge located in 1-cell at the bottom of the model grid. FIGURE 10b Model prediction of surface Total Phosphorus (as hours above PWQO) 25, with the discharge located in 9-cells distributed from surface to bottom of the model grid. The predictions provided in the Report are based on the mathematical model (Mike-3), which is a far-field model that is not specifically designed to, nor proven capable through 24 The Report, Appendix F, Response to MOE Comments from 29 August 2006, Figure The Report, Appendix F, Response to MOE Comments from 29 August 2006, Figure 2. Ref

20 calibration of, accurately predict the complex momentum and buoyancy effects of the wastewater plume within this initial mixing zone. As such, it may under-predict the buoyancy of the wastewater plume and thereby under-predict the water quality impacts. This same issue has been raised by the MOE 26 and responded to, in part, by CH2MHill. CH2MHill s reply to MOE s comments suggests the vertically distributed release is not a reliable prediction, however we disagree. The bottom release does not accurately represent the true mixing characteristics of the buoyant wastewater plume. This is confirmed by the CORMIX predictions provided as supporting information to the Report. These predictions show a surface plume that is several meters thick at the surface and extends 1.5 to 2 km alongshore and offshore under a 4 cm/s current (a larger mixing zone is expected at lower currents and calm conditions). CORMIX is often used with greater reliability to describe the behavior of a buoyant plume within the near-field region. Surface versus Bottom Water Quality The Report only shows surface water quality. However, in the response to the MOE concerns regarding the Mike-3 model, figures are presented that compare the predicted surface and bottom water quality. These figures are reproduced as Figures 11a and 11b. As illustrated, the concentration of TP at the surface exceeds the PWQO (for 1200 hours) over a small area extending several hundred meters around the diffuser. In comparison, the TP concentration at the bottom exceeds the PWQO over a 4 km distance parallel to the shore and nearly 1 km distance perpendicular to the shore. This difference is significant and further shows that the results presented in the Report are biased towards an under-representation of the potential water quality impacts. Considering cladophora grows on rocks and other hard substrate on the bottom, the higher concentrations of TP predicted on the bottom are more important to the interpretation of environmental impacts than the surface concentrations presented in the Report. Other Factors As a further point, the Report considered temperature differences (between wastewater and ambient Lake Ontario) of 8 o C, 2 o C and -1 o C, whereas the data presented in the Report shows a maximum temperature difference of 14 o C 27. Temperature difference is significant to the prediction of water quality since the greater the difference the greater the tendency for the plume to rise and remain buoyant on the surface. The lower temperature differences used in the Report biases the outcome towards a less buoyant plume and hence lower water quality impact. 26 MOE Memorandum from Peter Nettleton to Ted Belayneh, 26 July 2006; and follow-up exchanges on 29 August, and in September The Report, Appendix B, Section 2.1.2, Page 2-6, Figure 2-4. Ref

21 FIGURE 11a Model prediction of Surface Total Phosphorus (as hours above PWQO) 28. (for bottom source) FIGURE 11b Model prediction of Bottom Total Phosphorus (as hours above PWQO) 29. (for bottom source) 28 The Report, Appendix F, Response to MOE Comments from 29 August 2006, Figure The Report, Appendix F, Response to MOE Comments from 29 August 2006, Figure 4. Ref

22 5.0 CONCLUSIONS After reviewing the final Report, it is our opinion that there are significant deficiencies in the RWIA which result in under-estimation and under-statement of the impacts of both the existing discharge limit as well as any future expansion for the Duffin Creek Water Pollution Control Plant (WPCP). These deficiencies prevent the Report from being used as a reliable receiving water impact assessment. Further, the Report focuses only on concentration limits and performance objectives for the diffuser, but neglects all other requirements of the MOE s terms of reference. The most significant of these neglected requirements is the impact of excess total phosphorus (TP) and unionized ammonia (UIA) on the Ajax beaches and waterfront, the Ajax Water Supply Plant (WSP) intake, and the environmentally sensitive habitats at the Duffin Creek Wetlands, which is a provincially significant wetland. In our opinion, Condition 7 of the Minister s Order and the specific MOE terms of reference for the RWIA have not been met. However, even though impacts have been under-estimated in the Report, the modeling results nevertheless show that PWQOs for TP and UIA will not be met for significant times at the Ajax waterfront, the Ajax WSP intake and at the mouth of a provincially significant wetland at Duffin Creek. Had appropriate modeling been carried out, the peak concentrations and areal extent of the PWQO exceedance for TP and UIA would be substantially greater than reported. The Report acknowledges the exceedance of PWQO for TP will cause growth of nuisance algae but under-states its significance even though the Town of Ajax reports significant adverse impacts under the existing discharge limit. These impacts include excess growth of cladophora, which is a type of algae that grows on the bottom in nutrient rich waters. The cladophora turns the water a highly turbid green colour that is unpleasant for swimming or any other form of direct water contact. It also accumulates along the shoreline and creates an unpleasant odour as it decays. The sight and smell of the decaying algae severely impacts the aesthetic quality of the waterfront, beach areas and walking trails to the extent that residents no longer enjoy this valued resource. Ref