Laserfiche WebLink
Binns, Janet <br />From: Kaldenbach, Tom <br />Sent: Thursday, October 08, 2009 4:15 PM <br />To: Binns, Janet <br />Cc: Hernandez, Daniel <br />Subject: Foidel Creek Mine (C-82-056), PR-8, modified Item 6 comment <br />Attachments: schematic cross section.doc <br />Janet, <br />My modified response to Item 6 is shown below. This comment and the attached cross-section can be forwarded to the <br />operator. The operator's responses to my other comments in our initial adequacy letter were adequate. <br />Item 6. The Division recognizes a possible consequence from subsidence is there will be no impact to the springs because <br />the springs may have perched sources as a result of local permeability changes or geologic structure. The Division also <br />recognizes a reasonable probability that the six adjudicated springs are not significantly isolated by local permeability <br />changes or structure (that is, they are not perched) and they have formed along the outcrop belt of the Williams Fork <br />Formation as a result of the intersection of the regional potentiometric surface with the land surface in this area, as shown <br />in the attached schematic cross-section. <br />Please add to the prediction of worst possible consequences from subsidence either "a" or "b", below. <br />a) The information previously requested for the springs, for a scenario in which: <br />i. The main source of each spring is the intersection of the regional potentiometric surface with the land <br />surface along the outcrop belt, and <br />ii. Faults between the Western Mining District and the springs are not significant barriers to flow. <br />b) Detailed geologic information for each spring that demonstrates: <br />i. The local lateral permeability change or geologic structure that completely (or nearly so) isolates the <br />source of the spring from the regional ground water flow, and <br />ii. There is no reasonable probability that a significant source of the spring is the intersection of the regional <br />potentiometric surface with the land surface along the outcrop belt. <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) 866-3567, ext. 8128