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Aggregate Industries South Platte Combined SWSP June 1, 2021
<br /> Plan IDs 3614, 4773, 3624, 4772, 4616, 3437, 3376, 3650, 3668, 5475, 5829, 8t 6090 Page 21 of 23
<br /> Depth to Groundwater Percent Reduction in Calculated HCU'
<br /> (Feet) Native Grass Alfalfa
<br /> 1 85% 100%
<br /> 2 50% 90%
<br /> 3 30% 75%
<br /> 4 20% 50%
<br /> 5 15% 35%
<br /> 6 1 10% 20%
<br /> 7 5% 15%
<br /> 8 0% 10%
<br /> 1. Adapted from EVAPOTRANSPIRATION AND AGRONOMIC RESPONSES IN FORMERLY IRRIGATED
<br /> MOUNTAIN MEADOWS, South Park, Colorado, March 1, 1990; Revised September 1, 1991
<br /> 17. Dewatering at the Wattenberg Pit, W.W. Farms Pit, Tull Pit, Tucson South Pit, and
<br /> Irwin-Thomas Pit will produce delayed depletions to the stream system. As long as the pits are
<br /> continuously dewatered, the water returned to the stream system should be adequate to
<br /> offset the depletions attributable to the dewatering operation. Once dewatering at a site
<br /> ceases, the delayed depletions must be addressed. Accordingly, dewatering is required to
<br /> continue at the W.W. Farms Pit, Wattenberg Pit, and Tull Pit during the term of this approval.
<br /> Once dewatering has begun at the Tucson South Pit and Irwin-Thomas Pit it will be required
<br /> to continue during the term of this approval. At least three years prior to completion of
<br /> dewatering, a plan must be submitted that specifies how the post pumping dewatering
<br /> depletions (including refilling of the pit) will be replaced, in time, place and amount.
<br /> 18. Prior to claiming any credit for the water returned to the stream system from dewatering in
<br /> excess of lagged dewatering depletions (a net accretion), the applicant must install a
<br /> totalizing flow meter that accurately measures the quantity of water being pumped and
<br /> returned to the stream system via dewatering operations and account on a real time basis for
<br /> the actual dewatering depletions and accretions. No net accretion credits are sought by the
<br /> Applicant for this approval period.
<br /> 19. If dewatering of any of these sites is discontinued, the pit would fill, creating additional
<br /> depletions to the stream system due to increased evaporation. To ensure that additional
<br /> depletions to the river do not occur, a bond has been obtained through the DRMS for lining or
<br /> backfilling of the lakes. Therefore, if the dewatering is discontinued these bonds can finance
<br /> the completion of the lining of these pits or the backfilling, thus preventing depletions to the
<br /> stream system.
<br /> 20. The approval of this substitute water supply plan does not relieve the Applicant and/or
<br /> landowner of the requirement to obtain a Water Court decree approving a permanent plan for
<br /> augmentation or mitigation to ensure the permanent replacement of all depletions, including
<br /> long-term evaporation losses and lagged depletions after gravel mining operations have
<br /> ceased.
<br /> 21. If reclamation of the mine sites will produce a permanent water surface exposing
<br /> groundwater to evaporation, an application for a plan for augmentation must be filed with
<br /> the Division 1 Water Court at least three (3) years prior to the completion of mining to
<br /> include, but not be limited to, long-term evaporation losses and lagged depletions. If a lined
<br /> pond results after reclamation, replacement of lagged depletions shall continue until there is
<br /> no longer an effect on stream flow. According to the SWSP request, mining of material has
<br /> ceased at the Jeronimus Pit, Platte Valley Pit, F-Street Pit, Brighton Pit, Tucson Pit, Distel
<br /> Pit, and Wattenberg Pit. Since material mining has ceased at these sites, either the lakes
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