2019-05-03_PERMIT FILE - C1981038A (4)

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2.05 APFLICi1TICii iCTc ra'Fu'Li' c"C.t'Z uuia¢~a:u ~ L^.:.:..C":.GL.a :~.`1uw~ ~1L'1'i'vl"'i s~S. - MINIIi@f RflQQIRF242TI'3 FCR OPERATION 7+PID crnr.~vnTTQd PLT~PS. • 2.05.6 liitigati.on of bl~rfaoe Opal ;T;*+~ Eapncts (Cbnt'd.) (s) (a) (ii) (Cont'd.) surface in the area of the spring. The collection point far the spring itself is situated immediately adjacent to and at essentially the same elevation as a small ephemeral channel. The Upper Cabin Spring is atypical as dared to other monitored springs in the permit area in that *~a~~~hle flows appear to occur year around and flow rates are relatively hick. The co~aratively large drainage area (approximately 440 acres) arxi enhanced subsurface collection system installed at this site likely account for the consistent flaw pattern observed. The collection system consists of a network of 4" perforated PVC pipe bedded in gravel and buried approximately 3 to 8 feet deep. COVCC does not believe that mining proposed within the West Roatcap drainage constitutes a significant threat to either the quantity or quality of water emanating from the Upper Cabin Sprirxj. Significant and potentially disruptive sulsidence effects for surface resourrns within the COVCC permit are anticipated only in areas where mining occurs below less than 800 feet of Overburden (refer to Geo-Hydro Subsidence Study, Volume 3). Consequently, buffer zones affo~im only limited opal extraction within certain areas of Lease OOC-37210 were defined within the permit • area to protect surface resources and prevent subsidence. As a further resource protective measure, the western boundary of lease COC-37210 was moved east from it's originally proposed location to it's present location in cooperation with and in response to concerns voiczd by the Stucker Mesa Domestic Water Company during the original lease tract delineation procp~a. Mining in the nearest proximity of the Upper Cabin Spring will be located at a miniumun of 1700 feet distant from the surface expression and collection point of the spring. Subsidence projections for the permit area developed by Geo-Hydro Consulting, Inc., in 1983 have been shown to be reasonably conservative through subsidence data collection efforts conducted subsequent to the study (refer to Annual Subsidence Reports). The worst case iugnct predictions based upon the subsidence projections contained in the Geo-Hydro study do not entail significant aryl lasting impacts to colluvial and alluvial water sources in areas of greater than 800 feet of overburden. The Upper Cabin Spring is located over approximately 1000 feet of overburden cover while mining in the nearest proximity will occur under approximately 1300 feet of overburden cover. It is most probable that the Upper Cabin Spring derives it's water from shallow surficial sources and that potential ir~acts due to mining will be negligible and temporary if detectable at all. If, however, the Upper Cabin Spriry source is disrupted at depth as a result of mining or if surface subsidence effects in the West Roatcap Creek drainage • result in a disruption of surface and shallow groundorater flow patterns to the d~ree that they becmne evident at the sprirx3, the following 742 93-22 Revised 03/18/93 98A