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DocuSign Envelope ID: 197F5956-19D6-4F92-82DE-3E2CEC3A7F29 <br /> IrIJ­ Ii/"`V <br /> July 9, 2020 <br /> Page 2 <br /> Response: Attachment 2.05.3(3)-6 and 2.05.3(3)-21,have outdated information that is not <br /> current with conditions of Pond 013 and the watershed contributing to it. There is zero <br /> justification for a permit document to contain three hydrology models for one sediment pond that <br /> puts Tri-State at risk of receiving a notice of violation due to duplication of materials in the <br /> permit. This risk is easily avoided by removing the outdated information. Further, duplicate <br /> information in a permit also places the Division in a position to not be able to understand what is <br /> current on the ground, and enforce rules when multiple iterations of a pond hydrology are <br /> presented in a permit document. Therefore,it is fully appropriate to remove both of these <br /> attachments and consolidate all of the Pond 013 hydrology into one location (Attachment <br /> 2.05.3(3)-32). <br /> That being said, Tri-State does agrees with the Division that several items from Attachment <br /> 2.05.3(3)-21 should remain in the permit document. The Pond 013 embankment compaction <br /> results and the safety calculations have been inserted into Attachment 2.05.3(3)-32 accordingly. <br /> Attachment 2.05.3(3)-32 <br /> 5. Please explain why Tri-State decided to no longer reference Table 2.05.3(3)-IA (SCS Curve Numbers) <br /> on page I of the attachment, but instead references historical curve numbers in another table. <br /> Response: Please see response to comment 2. This issue has been corrected with the <br /> incorporation of the approved TR-98 items. <br /> 6. Please provide an explanation the large change inflow out of Structure 92,fi^om 0.00 acre feet to 8.18 <br /> acre feet. (Seepage 4 in the proposed SEDCAD run for the 10 year storm) <br /> Response: While trying to determine why there was a change in the flow from Structure 92,it <br /> was discovered that the previously submitted and approved SEDCAD model had multiple errors <br /> and inconsistent networking between the 10-year and 25-year storm events. Tri-State requests <br /> that the Division disregard the old model due to multiple errors, and review the compliant <br /> SEDCAD model submitted under TR-99. <br /> 7. Regarding Ditch C-9, it appears that the left sideslope was entered incorrectly. Should it be 2:1? (See <br /> page 7 in the proposed SEDCAD run for the 10 year storm.) <br /> Response: The typographically error for the left sideslope of the C-9 ditch has been corrected as <br /> noted, and the 10-year and 25-year hour storm event demonstrations have been resubmitted. <br /> 8. Regarding Page 10 in the SEDCAD run for the 10 year storm,please explain why the dead space <br /> increased to 20%fi^om 0%with this submittal. <br /> Response: SEDCAD defaults to 20%dead space as this is the recommended amount of dead <br /> space for a pond with and average width ratio of 2:1 at the principle spillway according to Dr. <br /> Richard Warner as described in the SEDCAD 4 Design Manual and User Guide. The default <br /> selection of 20%is more reflective of the actual Pond 013 width ratio,rather than 0%. <br /> MV EQUAL i ihJPi..0)"ER <br /> A Touchstone Ene:rgy'Cooperative <br />