2015-09-25_REVISION - M1980183 (3)

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Applegate Group, Inc. Water Resource Advisors for the West September 25, 2015 Mr. Tyler O'Donnell Division of Reclamation, Mining and Safety 1313 Sherman Street, RM 215 Denver, CO 80203 RECEDED SEP 2 5 2015 DIVISION OF RECLAMATION MINING AND SAFETY RE: Brannan Sand & Gravel Company Pit 29, Permit No. M-1980-183, Amendment to AM -02, Datum Shift Dear Mr. O'Donnell: This letter updates my letter of September 18, 2015, concerning the AM -02 objection letter filed by Albert Frei & Sons (AFS). That letter identified an AFS concern that there should be "a way to correlate the elevations being proposed in the amendment to [AFS Worthing Pit and Stagecoach Pit] approved elevations so we all know they will not cause a problem we will have to fix later." To clarify my September 18 letter, while the AFS objection letter might suggest that the depth of the french drain be adjusted to a lower elevation if NAVD 88 elevations were consistently used, the wording of the AFS objection suggests only that a survey clarification occur if, as in this case, baseline, pre -mining groundwater elevations were not based on the NAVD 88 survey presently in common use. As detailed below, that survey clarification is appropriate and, with this letter, now part of the AM -02 record. Correction As another initial note, in my September 18 letter, I discussed Brannan's justification for placement of the french drain four feet below the ground surface, and our concern that adjusting this plan to a deeper elevation could have adverse impacts. Specifically, we reported that Mr. Einspahr, the immediate neighbor to the south of AM-02,was concerned about shallow wells and vegetation on his property. We believed it was appropriate to account for these concerns in the design of the french drain regardless of whether they are real or perceived. However, independent of these concerns and based on the detailed discussion below, we believe the french drain is properly located to minimize any disturbance to the prevailing hydrologic balance. Detailed discussion of survey clarification In my September 18 letter, I stated that it is entirely possible that the benchmark french drain elevation of 5007 is the same as the documented pre -mining groundwater surface elevation in this location. I have been able to locate a source to resolve the datum issue. NOAA (specifically the National Geodetic Survey, NGS) has an online tool that converts the old datums to the new datums. 7405 W. Highway 50, Suite 123 1490 W. 121" Avenue, Suite 100 118 W. 6`h Street, Suite 100 Salida, CO 81201 Denver, CO 80234 Glenwood Springs, CO 81601 303-452-6611 www.applegategroup.com