ENVIRONMENTAL & WATER-RESOURCE CONSULTANTS June 5, 2008 Ms. Kathryn Pounder, MA, MCIP, RPP Niagara Escarpment Commission 232 Guelph Street Georgetown, Ontario L7G 4B1 Subject: Peer review of Duntroon Quarry hydrogeologic modelling: Report #1 Dear Ms. Pounder: We have conducted a preliminary review of the groundwater modelling conducted for the proposed expansion of the Duntroon Quarry, Clearview Township, County of Simcoe. For our preliminary review we have studied the reports of the modelling and assembled a set of questions and comments that we hope will clarify the analyses of current conditions, and enable us to understand fully the work that has been conducted in anticipation of the predictive scenarios. We expect that in some instances our comments will require a simple response directing us to other parts of the extensive documentation for the application. Our preliminary review is presented in two parts: Overview comments; and Detailed technical comments/questions. For our final review, we will review the results of the predictive analyses in detail, and examine the model input and output files. Since we do not have access to the computer code that has been used for the updated modelling (MODFLOW-SURFACT), we expect that the final part of our review may require meeting with the modellers of Jagger Hims Limited. 90 FROBISHER DRIVE, UNIT 2B, WATERLOO, ON, N2V 2A1 TEL: (519) 579-2100 FAX: (519) 579-9779 WWW.SSPA.COM
Page: 2 I. Overview The reporting of the groundwater modelling has been submitted in two parts: Jagger Hims Limited, 2005: Duntroon Quarry Expansion: Geological Report and Level 2 Hydrogeological Assessment, Lot 25 and Part Lot 26 Concession 12 and Part Lot 25 Concession 11, Clearview Township, County of Simcoe, prepared for Georgian Aggregates and Construction Inc., September 2005. [The groundwater model is documented in Appendix F]; and Jagger Hims Limited, 2007: Duntroon Quarry Expansion: Level 2 Hydrogeological Assessment Addendum, Proposed Expansion and Proposed MAQ Highland Quarry, Computer Groundwater Modelling, Response to Agency Review Comments, prepared for Walker Aggregates Inc., October 2007. We obtained these documents by downloading files from the Walker Industries Holdings Limited web site (http://www.walker-net.com/geoaggexpansion). Some of the pieces of the 2005 report that are relevant to our review were missing, and Jagger Hims Limited (JHL) supplied them immediately. In particular, the missing pieces were Figures 6-11 and 6-22, and the tables in Appendix F. Mr. Andrew G. Hims, P.Eng., during a brief conversation regarding the electronic reports, indicated that the analyses described in the 2007 addendum build on the 2005 analyses. Based on our review of the two documents, it is clear that a significant additional effort has been undertaken. The analyses have been revised substantially. We note the following changes in the 2007 analyses: 1. The distribution of the specified recharge has been modified based on a reassessment of the karst features at the site; 2. The distribution of hydraulic conductivity has been revised; 3. The water level targets for the calibration to existing conditions have been supplemented with data from the proposed MAQ Highland Quarry; 4. The examination of the match between observed and calculated water levels for the calibration to existing conditions has been expanded; 5. Flow observations have been incorporated in the evaluation of the simulation of existing conditions; 6. The analysis has been extended to consider seasonal water level data rather than only long-term average conditions; and 7. The predictive scenarios consider the cumulative impact of the proposed MAQ Highland Quarry.
Page: 3 In our opinion, the analyses generally have been conducted at a relatively high technical level that is consistent with the state-of-the-practice. During calibration of the model for existing conditions a close match has been obtained to some of the observations. However, based on our review of the calibrated model we do have reservations regarding its application for future conditions. We are not sure how well the analysis of existing conditions has been constrained by the available data. Furthermore, we are not clear about key elements of the analysis of existing conditions. Our reservations and requests for clarification and selected additional results are presented in the following detailed technical comments.
Page: 4 II. Detailed technical comments/questions 1. It is not clear how well the distributions of hydraulic conductivity that have been inferred from model calibration are constrained by the available data from hydraulic testing. In the 2005 modelling, relatively simple distributions of hydraulic conductivity are considered (Figures F-5, F-6 and F-7). In contrast, the hydraulic conductivity distributions adopted for the 2007 modelling show a significant amount of detail. The reporting does not allow us to assess whether this detail is supported by the results of hydraulic testing, or whether it has been invoked in an ad-hoc manner solely to improve the matches to observed water levels on a well-by-well basis. In our opinion, the connection between the results of testing and the inferences from calibration needs to be strengthened. We recommend that maps be produced that correspond to Figures A-1 through A-4 of the 2007 report, with the estimates of hydraulic conductivity estimated from in-situ tests superimposed on the most recent interpretation of the distribution of material properties. 2. It is not clear from the reporting whether hydraulic conductivity estimates are available from slug tests conducted on all of the monitoring wells on the Walker lands (existing quarry and expansion footprint) and the site of the proposed MAQ Highland Quarry. Are these data available? If they are, we recommend that they be included in the maps recommended in Point #1. 3. It is not clear how well the calibrated model is able to match the results of controlled pumping tests conducted in the vicinity of the site. Pumping tests are discussed in JHL (2005; p. 40-46). We expect that most of these tests provide only a local impression of material properties, and may therefore be valuable additions to a compilation of the results of single-well testing. Our real interest is in tests that may have stressed a larger area, such that the observations might be appropriate for testing the calibrated model. Are any of the pumping tests suitable for this purpose? It is indicated on Page F-7 of JHL (2005) that pumping tests are typically about an order of magnitude greater than packer testing results for the same aquifer. Is this suggestion based on results from the site, or from more general experience?
Page: 5 4. The model documentation refers to anisotropy of horizontal hydraulic conductivity (JHL, 2005; p. F-20). Are any maps available that indicate interpreted preferential directions of jointing and/or dissolution channels in the vicinity of the site? A horizontal anisotropy ratio of 1.67:1 is indicated on Table F-7. In our opinion, this is a subtle ratio. Can a ratio this low be inferred reliably from the calibration? Are sufficient data from hydraulic tests available to support this inference? Is there evidence that supports the assumption that the principal directions of hydraulic conductivity follow the north-south alignment of the finitedifference grid? 5. Insufficient information on the calibrated model is provided to develop independent calculations of key quantities such as the inflow to the existing quarry. In particular, we request that additional maps be prepared of the thicknesses of each model layer. These maps should include a posting of the points used to constrain the mapping. 6. The representation of the seepage face along the Niagara Escarpment is described briefly in JHL (2005; Page F-7). It is indicated that groundwater discharges from the lower section of the aquifer (Amabel Formation + Fossil Hill Formation). This is consistent with the modelling approach described on Page F-16, in which drain nodes are assigned control levels that correspond to the interface between the Fossil Hill Formation and the Cabot Head Formation. This approach is not consistent with our experience at other sites along the Niagara Escarpment. Our experience at sites in southern Ontario suggests that seepage faces form at the contact between the overburden and the Amabel Formation, at discrete depths within the Amabel Formation, and at the base of the Amabel Formation. Our experience is illustrated in Figure 1, and is consistent with the theoretical and experiment results of Rulon and Freeze (1985) and Rulon and others (1985). Is there evidence from the site that the only seepage from the escarpment is at its base? Elsewhere in southern Ontario, lines of ice that form along the walls of rock cuts and quarry walls provide visual evidence of multiple seepage faces, as do accumulations of vegetation. Have seepage faces been mapped along the face of the Escarpment? The effect of specifying drains with a control level only at the base of the Fossil Hill is a tendency of the model to predict relatively low groundwater levels and discharge rates along the Escarpment. This tendency appears to be corroborated in the updated model of existing conditions; in particular, a zone of relatively low hydraulic conductivity has been added parallel to the Escarpment in model layers 1 and 2 to keep water levels high. Is this zone of reduced hydraulic conductivity supported by data from hydraulic tests? 7. A similar approach is adopted to represent the quarry. The control levels for the drains that represent the existing quarry are set at the base of the quarry. Have seepage faces been mapped in the existing quarry?
Page: 6 Figure 1. Expected distribution of seepage faces along the Niagara Escarpment
Page: 7 8. The reporting does not indicate how the conductances have been estimated for the drains representing the Escarpment and the existing quarry. Are the conductances correlated to the properties of the rock adjacent to these features? On Page F-7 (JHL, 2005), it is indicated that the drain conductances for the quarry were assigned a value greater than the conductance of the Amabel Aquifer. Is this approach significantly different from assigning the heads directly in the quarry? 9. We are not clear how the western boundary of the model is represented. It is indicated in JHL (2005) that the boundary is represented with General-Head Boundary (GHB) conditions. However, the report does not indicate the bases for assigning the control levels and conductances for the GHBs. The conventional interpretation of the GHB Package is illustrated in Figure 2. Although the function describing GHBs is general, the application suggested in Figure 2 is the representation of a physical hydrologic boundary that is distant from the edge of the model. In this conceptual model, regional groundwater flow is roughly perpendicular to the edge of the model, L represents the distance between the edge of the model and the natural hydrologic boundary and K H represents the average hydraulic of the intervening material. C GBH = K L H bw Figure 2. Conceptual model for General-Head Boundaries
Page: 8 In our opinion, the application of GHBs in this particular application is unorthodox, as groundwater flow appears to be directed approximately parallel to the western boundary of the model. This is confirmed by the results of the overall water budget presented on Table F-8 for the original model (JHL, 2005). The tabulated results indicate that there are both inflows and outflows along the boundary, but both represent a relatively small portion of the water budget (about 2% and 4% of the cumulative recharge, respectively). Although the GHBs do not appear to be significant with respect to the overall water budget, and at least with respect to existing conditions, we recommend that the rationale for the assignment of the western boundary condition be described in greater detail. 10. Seasonal fluctuations in water levels in observation wells are described in both the 2005 and 2007 reports. However, neither report discusses the possibility of long-term trends. Are there sufficient data to plot long-term water level records for any of the observation wells? If there are, do the data suggest that long-term conditions are approximately stable, upon which are superimposed seasonal fluctuations? 11. The set of water level targets for the calibration is revised significantly between the 2005 and 2007 analyses. The calibration targets for the revised model are listed on Table 2-1 (JHL, 2007). The 2007 targets include water levels from 23 wells on the MAQ site. This is an important addition. Referring to the 2007 set of targets, what is the rationale for excluding five wells from the 2005 calibration (98-8, CLF5, 102-C, 104-A, OW1-4)? The 2007 targets also include an additional 4 targets (BH02-6, BH03-7-1, BH03-7-II, and Dempsey). Why have these wells been added? 12. It is indicated in JHL (2005) that wells were not used as calibration targets if less than one year of water level measurements was available. How many wells are excluded based on this criterion? 13. Are we correct in understanding that no information from MOE water well records has informed either the development of the conceptual model, or been used as a rough check on the calibration? In our opinion, what the information from MOE water well records lacks in reliability it makes up for in spatial coverage. We recommend that a map be prepared indicating the locations of MOE water well records in the regional model area. 14. The description of the calibration approach suggests that both recharge rates and hydraulic conductivities were adjusted during calibration. In our experience, recharge rates and the hydraulic conductivity of the uppermost model layer are generally correlated. How is this addressed in the calibration?
Page: 9 15. The reporting for the 2005 model includes maps of calculated water levels in the absence of a quarry and the inferred long-term drawdowns due to the existing quarry (Figures 6-9 and 6-10). We recommend that similar maps be prepared for the updated 2007 model. 16. In our opinion, an essential element of the reporting of the results of each simulation is a summary of the calculated overall water budget. An overall budget is presented for the initial simulation of existing conditions on JHL (2005; Table F-8). However, a similar budget is not included for the revised simulation of existing conditions. We request that a budget summary be prepared for each steady-state scenario considered. Furthermore, we request that the calculated quarry inflows and discharges to the Niagara Escarpment be reported separately. 17. To establish that the calibrated model can be used with confidence for predictive applications, it is particularly important that the model be demonstrated to be capable of matching observations of quarry inflows and stream baseflows. Limited assessments of model-calculated quarry inflows and streamflows are presented in JHL (2007; p. Tables 2-3 through 2-7). Are additional observed values presented elsewhere in the reporting? Simulated quarry inflows for existing conditions are compared against observations on JHL (2007) Table 2-3. The comparison is between the results of a steady-state analysis and inflows estimated to be between 10 and 20 L/s (these are apparently not measured). Have quarry inflow rates been monitored since the start of operations? Are time histories of quarry inflows tabulated and/or plotted? Where are the locations of the stream gauges against which the results of the calibrated model are compared on Tables 2-3 through 2-7? Are time histories of stream flows available for the stream gauges? Do the available stream flow data support the development of estimates of baseflows, for example with the code BFLOW, or with ranked-durations plots following the methodology of the Grand River Conservation Authority?
Page: 10 18. We have compared observed and calculated flows in Figure 3, using results from JHL (2007; Tables 2-3 through 2-7). The match between the model calculations and observations appears to be relatively poor. The transient results are shown for August. In the case of SW6, it is indicated in the report (Page 24) that the observations represent an average flow, while the model calculations represent only the groundwater contribution, that is, baseflow. Is this also the case for the other gauges? Are data now being collected that would support a more appropriate check on the model results? Based on precipitation records and Environment Canada estimates of evapotranspiration, is 2006 a typical year, and therefore an appropriate measure for comparing the results from a simulation of long-term average conditions? 10000 SW6 Calculated steady flow (m 3 /d) 1000 100 SW6 10 Steady-state Transient (August) 10 100 1000 10000 Observed average flow (m 3 /d) Figure 3. Comparison between observed and calculated stream flows
Page: 11 Closing We hope that our preliminary review comments assist in clarifying the conceptual model for the simulation of existing conditions. If you have any questions regarding our proposal, please contact Mr. Christopher Neville at (519) 579-2100, or by E-mail at cneville@sspa.com. Sincerely, S. S. PAPADOPULOS & ASSOCIATES, INC. Christopher J. Neville, M.Sc., P.Eng. Vice President, Senior Hydrologist CJN/cjn P:\Duntroon Quarry\Reporting\Duntroon Quarry_01_Letter_Pounder_20080605.doc
Page: 12 References Rulon, J.J., and R.A. Freeze, 1985: Multiple seepage faces on layered slopes and their implications for slope-stability analysis, Canadian Geotechnical Journal, 22, pp. 347-356. Rulon, J.J., R. Rodway, and R.A. Freeze, 1985: The development of multiple seepage faces on layered slopes, Water Resources Research, 21(11), pp. 1625-1636.