2023-10-31_REVISION - M1973021 (7)

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Holcim-WCR,Inc. I Morrison Quarry Drainage Report Appendix E—Hydrology • Drainage 03— Flows continue to be managed by routing to the Central Quarry. The hydrologic boundary is updated to reflect the installed haul road and proposed drainage diversion. No culverts or takeoffs were installed during haul road construction, and it is anticipated that flows will be collected and conveyed along the haul road to the Central Quarry as shown in Appendix B. • Drainage 04—This drainage is now incorporated within Drainage 02B and requires no additional analysis. • Drainage 06—The hydrologic boundary at its far south end was adjusted slightly where mine construction activity has occurred. The adjustment reduces the area of Drainage 06 by approximately 2% and was not included in this analysis because the change does not significantly alter the site drainage characteristics nor affect the proposed diversion design. Model Parameters and Assumptions The hydrological assumptions generally follow the CUHP guidelines and are consistent with the Phase II Drainage report. The following tables summarize the inputs used for the calculations. All areas are hydrologic soil group D with variation in the impervious areas based upon land use. The precipitation input is for both the 100-year and 5-year return periods for Morrison and can be seen in the calculation workbooks attached. Table 1 — Hydrologic Input Drainage Proposed Area Flow Path Length Percent Identification - - s) Impervious 02A 15 0.405 25 02B 55 0.327 50 03 87 1.401 50 Hydrological Results The CUHP input and output workbooks are attached to this calculation. The table below summarize the results presented in the Appendix B proposed drainage figure. Table 2— Hydrological Results Drainage Identification - 100-Year VF(`cfs) (cfs) VP 02A 6.6 25.4 02B 67.3 201.8 03 48.9 151.4