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7. It is not clear how the topsoil for this disturbance will be handled. Please clarify, and if there <br />will be new topsoil piles, please add these to the maps. <br />Response: The topsoil will be recovered and temporarily stockpiled within the construction area, and as the <br />individual treatment cells are constructed, will be replaced within the wetland zones as the vegetative growth <br />media to support the wetland vegetation and on the cell embankments to support temporary vegetation for <br />stabilization of these areas (refer to page 2.05-45.28). <br />8. Please specify the plan for vegetating the proposed passive treatment system including what <br />plant species will be placed and at whatfrequency. <br />Response: The relevant text has been reviewed and expanded to specifically address both wetland plantings and <br />vegetative stabilization of embankment areas. Copies of the revised text accompany these responses for <br />replacement in the PAP. <br />9. Section 2.2 of the design report references Appendix A Treatment Performance Modeling, <br />which present in the 2016 submission but was mostly cut out of the 2018 submission. This <br />included approximately 10 pages of what appears to be relevant data on temperature, <br />evaporation, and analyte removal rates which affected the sizing and anticipate performance <br />of the treatment system. Please include this information or explain why this data was removed. <br />Response: The referenced feasibility analysis was not included in the revised submittal, simply because it had <br />previously been provided. As relevant information, a copy is provided with these responses for insertion in <br />Exhibit 49EE, as a matter of completeness and for future reference. <br />10. Please provide additional design details and sizing for the AgriDrain System. It is not clear <br />what dimensions TC intends to use and pipe sizing between text and diagrams are not <br />consistent. It is not clear what if any maintenance is anticipated to assure function as <br />designed. <br />Response: The AgriDrain discharge control system will be used to control water levels within each of the <br />treatment cells to assure that the wetland beds are saturated and to optimize detention/treatment time at varying <br />flow rates. The AgriDrain system was selected due to its simplicity and the ability to control flows and water <br />levels. It is relatively maintenance -free, consisting of a control box with a vertical weir composed of removable <br />stop -logs, which can be added or removed to control level and flow. It is anticipated that flow/level monitoring <br />and adjustment would be coordinated with any significant changes in the discharge pumping rate from the <br />underground mine workings. The AgriDrain units are sized to accommodate the maximum flow rate of 375 gpm <br />and can be adjusted for any lesser flow rate. The design text ("Pipe Sizing") indicates that 8 -inch diameter piping <br />is recommended for flows between cells within the system, however, TC will have a significant quantity of 10 - <br />inch HDPE piping available following the change -out of the Thickener Underflow piping, so it is anticipated that <br />the 10 -inch pipe will be inspected for suitability and available piping that is in good condition will be reused in <br />construction of the Passive Treatment System. This information has been incorporated in the relevant permit text, <br />and copies of the revised text accompany these responses for replacement in the PAP. <br />H. Please provide additional design detail for the Cascade at the inlet of the system, including the <br />peak flow volume, rational for stone sizing, identification of vortex stones which are in the text <br />of the diagram but not labelled. <br />a. It appears to DRMS that weep holes may be needed, particularly at the discharge end <br />of the cascade structure. Please explain why these are not necessary or consider <br />modifying the design. <br />b. Please provide a description and update diagram showing how the inlet pipe and <br />cascade are being anchored into the drainage, so that neither water moving throw the <br />pipe or precipitation will compromise the function of the cascade. <br />