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Rule for Northern San Juan Basin—Fruitland Formation (see Rule 17.7.D.2). The State <br /> Engineer finds there is clear and convincing evidence supporting his adoption of a rule <br /> identifying water withdrawn from the Fruitland Formation by wells located within <br /> delineated areas within the geologic formation known as the Northern San Juan Basin <br /> ("NSJB") in southwestern Colorado to be nontributary for purposes of his administration <br /> and permitting of wells pursuant to C.R.S. § 37-90-137(7). The Northern San Juan Basin <br /> is defined as that portion of the San Juan structural basin located within Colorado. <br /> The State Engineer's finding is based primarily upon the testimony and evidence <br /> regarding the development, operation and calibration of a numerical ground water model <br /> of the Northern San Juan Basin (the "NSJB Model") utilizing MODFLOW. The State <br /> Engineer thus finds that there is clear and convincing evidence that the NJSB Model is <br /> capable of conservatively demarcating areas within the Fruitland Formation in the NSJB <br /> as nontributary in manner that is consistent with C.R.S. § 37-90-103(10.5) and, therefore, <br /> provides a useful tool for the State Engineer's administration and permitting of ground <br /> water wells pursuant to C.R.S. § 37-90-137(7). <br /> First, the State Engineer finds there is clear and convincing evidence that the detailed <br /> conceptual model of ground water flow in the Fruitland Formation within the San Juan <br /> Basin more than adequately represents the geologic and hydrogeologic characteristics of <br /> the pertinent formations for purposes of developing a ground water flow model meeting <br /> the objective of this rulemaking. The NSJB has been the subject of numerous studies by <br /> independent parties over an extended period of time. As a result, there is an extensive <br /> site specific robust geologic and hydrogeologic data for the NSJB. These robust data <br /> include permeability,basin geology, formation thickness and location, recharge amounts <br /> and location, location of outcrops, climatology, surface water hydrology, and ground <br /> water/surface water interaction. The testimony and evidence provided by the witnesses <br /> throughout this proceeding demonstrated that there was appropriate reliance upon these <br /> datain development of the NSJB conceptual model. Where there was doubt with respect <br /> to a certain data, the conceptual model generally relied on conservative data. Dr. James <br /> McCord, Ph.D,P.E., an expert representing parties generally opposed to adoption of the <br /> NSJB conceptual and numerical models, did concede that many aspects of the NSJB <br /> models are well founded on site specific data. <br /> Certain parties expressed concern that the recharge amount for the Fruitland Formation, <br /> which was estimated based upon a chloride mass balance method, may be inaccurate <br /> because of the possible contribution of chloride from the formation itself. However, the <br /> recharge estimate is consistent with independent recharge estimates by Kernoddle (1996). <br /> Certain parties also note that the Kirtland Shale Formation thins out in the eastern portion <br /> of the NSJB, and questioned whether the formation should be considered a confining <br /> layer for that portion of the model. However, the evidence demonstrated that even to the <br /> east the Kirtland Shale Formation remains at a thickness which is much more than <br /> sufficient to act as a confining layer. Finally, certain parties questioned whether certain <br /> "dikes" formed by vertical to near-vertical intrusive igneous features in the eastern <br /> portion of the NSJB might act as pathways for hydraulic communication between the <br /> Produced Nontributary Ground Water Rules 2 CCR 402-17, Statement of Basis and Purpose <br /> -13- <br />