Laserfiche WebLink
GL&A <br />October 7, 2015 <br />Ross Bachofer <br />P.O. Box 652 <br />LaSalle, Colorado 80645 <br />Hvdroaeolog;ical and Environmental Consultants <br />RE: Addendum to HEC -RAS Modeling Report -Potential Impact of Migration of South Platte <br />River on Flooding Bachofer Property; 7525 Highway 85, Fort Lupton, Colorado <br />Dear Mr. Bachofer: <br />This letter is an addendum to the HEC -RAS Modeling Report Dated October 6, 2015 and rebuttal to the <br />assertion (Tom Parko's letter from Weld County dated March 4, 2015) that flooding on the Bachofer <br />property is due to the temporal migration of the South Platte River. In addition to this claim, Mr. Parko <br />also speculates prior to the Aurora LOMR (Letter of Map Revision) that the Bachofer property was <br />outside of the FEMA mapped floodplain and that the movement of the river could be what is causing <br />Mr. Bachofer's flooding and not mining activities. <br />Recent results HEC -RAS modeling conducted by GL&A, clearly demonstrate there is no evidence to <br />support this speculation and hypothesis. Below are a series of Google Earth photos (Figures l to 17) <br />over a period of 21 years from June 1993 to June 2014. These photos date back prior to mining <br />activities when the current mine site was used for agricultural purposes. While these photos were taken <br />during different months of the season when river flows vary considerably, as can be seen from Figures <br />to 17 the position of the river channel with respect to the Bachofer property has not changed or moved <br />with time. Furthermore, lateral movement of the channel would not affect flood levels. The extent of <br />flood plain flooding is dependent of the elevation of the channel and surrounding areas adjacent to the <br />river channel. While slight changes to the river bottom may occur with time due to erosional and <br />depositional processes, these phenomena will not impact major changes to water levels and river stage. <br />As explicitly demonstrated by the results of the HEC -RAS modeling report by GL&A, topographic <br />alteration of the floodplain due to mining activities at the LG Everist mine site has caused unnatural <br />flooding of the Bachofer property. <br />If you have any questions about this letter and addendum, please feel free to contact me. <br />Sincerely, <br />Ganser Lujan & Associates <br />Joel M. Sobol P.G. <br />6692 TV. 96Th Place, Westminster, CO 80021, 720-272-2306, caluian(a),comcast.net <br />