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4.08.1 Surface Water <br />21. The current page 4 -173; section 4.08.1.2, discusses haul road culvert sizing. This section <br />references Tables 4.8 -1 and 4.8 -1 a which are proposed to be replaced with Table 4.8 -2 and 4.8 -2a <br />submitted with the revision. Please update the permit text on this page with the revised table <br />numbers cited. <br />Trapper Response to Comment 21: Page 4 -173 has been revised with the requested change to the table <br />references and is enclosed. <br />22. Proposed Table 4.8 -2; Haul Road Culvert Sizing, lists the culverts that exist at the site. The <br />following culverts were added to the table and depicted on the revised M51 maps; ASH -1, ASH -2, <br />BH -1, EMF -1, MZ -1, MZ -2, MZ -3 and MZ -4. It appears these culverts have been installed but <br />were not part of the current approved permit. Also, many culverts are depicted on the M5I(Sheet 3) <br />map for proposed culverts that appear to be for the future haul roads to be constructed in the next <br />permit tern. Rule 4.03.1(4)(e)(v) indicates that "culverts shall be installed to accommodate flow <br />from the intersecting drainages, and from road surface drainage as necessary to control erosion. <br />Designs for culverts shall be in accordance with 4.03.1(4xe) except where alternative specifications <br />are approved." Permit section 4.08.1.2 indicates culvert sizes are determined by running hydrologic <br />models. For the culverts listed above and the future culverts to be installed, please submit the <br />information/parameters used to determine the proper culvert sizing. Other Operators submit copies <br />of the SEDCAD runs they use to design culverts. <br />Trapper Response to Comment 22: Table 4.8.2 has been updated to indicate the status of each <br />culvert on the site. Per permit section 4.8.1.2 and the regulations, only culverts in undisturbed <br />areas require designs. Rule 4.03.1(4)(a)(iii) states haul roads within disturbed areas will be <br />designed and constructed using the best technology available. The footnote column of Table <br />4.8.2 indicates whether a particular culvert is placed under a certified haul road built through <br />undisturbed areas per rule 4.03.1(4)(a)(iv) or is present in disturbed areas. Appendix S contains <br />the certified haul road information. Trapper does indeed utilize hydrologic modeling to <br />determine the sizing of it culverts, however these models are typically done as needed at the time <br />of construction and are not retained. For the above referenced culverts, per the regulations, <br />designs are not necessary and were constructed using piratical analysis of the anticipated <br />runoff. The exception is culvert EMF -I which was sized according to the culvert just upstream <br />that was designed many years prior to EMF -1 installation. The table demonstrates that the <br />installed culverts are more than adequate to handle any flow to this structure. <br />Map M -51 will continue to represent all culverts on the site as a reference regardless of their <br />status within active mining, disturbed or undisturbed areas of the site. <br />Future culverts are currently shown on map M -51 as a reference. Table 4.8.2 does not contain <br />their designs yet as the hydrologic models and designs have not been completed for their <br />respective watersheds. When this work is completed Trapper will submit the required <br />information as necessary. <br />Table 4.8.2A was also updated and is enclosed due to an inconsistency between the table and <br />map M -51. <br />