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Z 04.8 Baseline Climatological Information <br />Permit section 2.04, Environmental Resources presents climate information. References cited date from <br />1941, 1974, 1978. More recent, updated climate information is available. <br />Site hydrology was updated in 1994 as per Technical Revision Drainage Control Plan II, (TR28). <br />This section of the rules is adequately addressed in the permit with the exception of: <br />As the site is moving into reclamation, climatological data encompassing more current <br />information up to the present should be evaluated and presented. <br />1. Should updated climate information yields increased runoff to permanent <br />ponds and ditches, then the design capacities of these structures must be <br />reevaluated to assure adequate passing of precipitation events. <br />2.05.3 Onerations Plan - Permit Area <br />This is a review of the permit requirements for general and detail design plans for sediment ponds, <br />impoundments and other diversions proposed in the permit as per Rule: 2.05.3(4). <br />Sediment Pond designs are found in Appendices K and K-3 of the permit. Ponds have been designed to meet the <br />requirements of a 10 year 24 hour storm event. Permanent Sedimentation Pond 2 is in compliance with Rule <br />4.05.6. Drainage facilities are identified in Appendix M-1 of the permit. Proposed permanent drainage facilities <br />for final reclamation, (Sediment Pond 2 and Dugout Pond) are shown in Appendix Q-1 of the permit. <br />This section of the rules is adequately addressed in the permit as per RN6, <br />�g However; should reevaluation of hydrologic data using current data indicate an increase in <br />runoff or sediment production, <br />2. Sediment Pond 2 design and storage capacity should be reassessed to assure <br />containment of storms of increased intensity. <br />4.05 HvdroloQic Balan <br />Because of the low relief and deep, well -drained soils, there is virtually no surface runoff. No streams, springs or <br />seeps exist in the area. All water flows subsurface through aeolian deposits to Ennis Draw, a topographic Swale <br />(ephemeral drainage) located along the eastern boundary of the permit area. Ennis Draw appears to be a <br />complex, braided, ancient stream bed that has been covered by windblown sand. It discharges several miles to <br />the north into Box Elder Creek, (Findings RN6, 2011). <br />Hydrologic characteristics are presented in Appendix K, dated January 1996 and detail surface water runoff, <br />sediment control and storage characteristics. Appendix K also presents as built details for Sediment Pond #2, <br />(dated 1996) and plate 5 illustrates the Dugout Pond and cross section details, ( dated 1997). <br />As per Appendix K-1 of the permit there is no evidence of surface runoff occurrence within the watershed <br />boundary and the infiltration capacity of the deep sands that mantle the area appears to prevent runoff. However, <br />runoff calculations, curve numbers the design storm estimate of three inches, and gross soil erosion were based <br />on precipitation data collected prior to 1961 and soils information from the 1970's. That information is 55 and <br />40 years old respectively. Since there is ample evidence to suggest that prevailing hydrologic balance may have <br />changed since then, prudence suggests the reevaluation of this information. <br />In order to assure no offsite impacts as this mine moves into the 10 year reclamation period, <br />(see comment above as per Rule 2.04.8), please verify permanent pond and ditch capacities to <br />handle any increases in runoff and provide this analysis to DRMS by verifying: <br />3. Detention storage requirement of Sediment Pond 2 <br />4. Or, demonstrate to DRMS that the data and values presented in Appendix K-1 of <br />the permit remain valid in 2016 and through 2026. <br />