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3. TERT CHANGES TABLE 43 WATER QUANTITY EFFECTS Pumping Rate (gpm) Annual Water Use (acre-ft)a Total Use for Mine Lde (acre-ft) Water Lek in Cavities (acre-ft) Water Left is Cavities with Subsurface Fly Ash Disposal (acro-ft)d Depletion in Flow from Yellow Crk (eft) Percent of Average Daily Flow Depletion io Flow from Piceance Crk (eft) Perant of Average Daily Flow No Proposed Action SO,OOD TPY Action 500,000 TPY 60 80.00 109.00 436.00 93 124.00 169.00 674.00 186 3,720.00 5,070.00 20,220.00 13 574.00 1,404.00 5,615.00 13 574.00 1,404.00 5,488.00 None 0.04 D 0.06 ~ 0.29 ~ None 2.00 3.20 15.30 None 0.04 b 0.10 ~ 0.51 ~ None 0.10 0.30 1.90 + Assumes pumping at specified rate for 24 hours per day, 350 days per yeu. b Assumes that 50 percent of the pumping will be sUesm depletion and that the effect will be evenly divided between Piceaoce Creek and Yellow Cra:k. ~ Stream depletion after 30 years of pumping modeled by Wright Water Eagirteers (1986). d Fly ash disposal is considered under the 500,000 TPY Altemative only. for the Proposed Action (125,000 TPY}, and l.9 percent (.51 cfs) for the 500,000 TPY Alternative. (For a discussion 0o the significance of these depletions, please see Section 4.4.6, Water Uses and Water Righes.) These reductions would take place gradually, with foil depletion obtained 25 to 27 years after mining begins. These depletions could persist for many years after pumping has stopped, until surface and groundwater systems recover to natural conditions. These projected depletion rates could substan- tiallychange if a second water supply well were incorporated to satisfy production requirements for the 500,000 TPY Altemative. Pumping rates and location of this second wet! would compound the effects of drawdown on the upper aquifer and the associated depletion e~f the surface waters. Therefore, additional hydraulic simulation and analysis will be required to further determine surface water impaces prior to approval of the 500,000 TPY Alterative. The depletion amounts shown in 'cable 43 are based on mathematical modeling of the cone of depression for the upper aquifer from a single well source (William H. Bellis 1986). The scope of model sinnulations are limited by the structure of the model, the availability of site specific detailed data, and annual and seasonal variations of natural conditions. Additional field data are needed to accurately verify predicted depletions and they sil;nifitxnce. Therefore, BLM will require that springs and stream flows of Yellow and Piceance creeks, potentially affected by these depletions, be inventoried by WRC and monitored on a regular basis, prior to and during mining operations. Monitoring will include water quantity and quality of stream Bow above and below lease boundaries, and all springs within the cone of depression. 4.4.2 Surface Water QtraBty Surface water quality could be degraded by ao increase in sediment delivered to the stream associated with sodium project construction/operation or by a spill of brine from mine operations. The mine site is located at least 2 miles of ephemeral stream distance from any perennial water. The interim revegetation standards proposed in the reclamation section should also quickly stabilize the soils. It is, therefore, unlikely that any significant increase in sediment yield would occur in either Yellow or Piceance Creek under any alternative. To mitigate possible impacts to surface water, the mine operator has proposed to install leak detection alamu on all surface piping. Also, the piping has been designed so that it coo be drained to the evaporation ponds before it is moved. Visual inspections of the piping system are also planned. These precautions would limit any leaks of brine from the piping to small amounts. The mine facilities would be built on concrete slabs and drained via a sump system 3-l5