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Northwestern Colorado, USGS Water-Resources Investigations Report 90-4020. A spring's location in <br />alluvium on the land surface does not necessarily prevent hydraulic connection to the underlying bedrock unit <br />(please see attached schematic cross-section). Regarding faults as permeability barriers, permeability can vary <br />greatly along a fault plane resulting in the fault plane being a barrier to flow in some places and a conduit for <br />flow in other places. Also, significant ground water flow across a fault is not necessary for a drop in the <br />regional potentiometric surface to extend across the fault. The drop in elevation of the potentiometric surface <br />caused by mine subsidence cracks would extend outward from the mine area due to the breach of the hydraulic <br />pressure system overlying the workings. This appears to have occurred in well FBR-2 (please see attached <br />hydrograph). <br />Spencer Spring #2, Bear Run Spring, House Spring #1 - Please provide the locations of these springs so that we <br />can determine if they need to be added to Map 15A. <br />Sincerely, <br />Tom Kaldenbach <br />Environmental Protection Specialist <br />Colorado Division of Reclamation, Mining and Safety <br />1313 Sherman St., Room 215 <br />Denver, CO 80203 <br />(303) 866-4923 <br />E-mail Disclaimer: The information contained in this e-mail, and in any accompanying documents, may <br />constitute confidential and/or legally privileged information. The information is intended only for use by <br />the designated recipient. If you are not the intended recipient (or responsible for the delivery of the <br />message to the intended recipient), you are hereby notified that any dissemination, distribution, copying, <br />or other use of, or taking of any action in reliance on this e-mail is strictly prohibited. If you have <br />received this email communication in error, please notify the sender immediately and delete the message <br />from your system.