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.~(~1~kL~- Pv~ <br />Mary L. Gillam, Ph.D. 115 Meadow Road East ' ~,~ ~ 1 ~ ~'-0 9' 4' <br />Durango, CO 81301-7093 <br />970-259-0966/970-259-6064 fax <br />Consulting Geologist giltam@rmi.net <br />November 28, 2003 0 ~cFi~~ RQ(.~tg. <br />oiYi . '' ~"~~ <br />Ms. Kaza A. Hellige so~o, FC iap ~ SEC C 3 2o~3 ,~ <br />Chief, Durango Regulatory Office «,-, p <br />U.S. Army Corps of Engineers, Sacramento District "..`` 4 vU/vTe1°p°ofM~e~efs ~~ <br />278 Sawyer Drive #1 ~ <br />Durango, CO 81303-7916 °81' <br />Re: ANIMAS RIVER IN-STREAM GRAVEL PITS - <br />SELECTED ISSUES RELATED TO CHANNEL GEOMORPHOLOGY <br />This report analyzes certain aspects of active in-stream gravel mining since 1996 as input to <br />USACE's regulatory process. I understand that you are considering whether to extend the <br />current permits and if so, what additional requirements should be included. These permits expire <br />on November 30, 2003, extensions may be granted until November 3Q 2004, and new permits <br />maybe issued for mining after that time. To assist you, I have reviewed applicable permit <br />conditions or agreements, compliance, and some mining impacts on the river channel. I have <br />also suggested new permit conditions or activities that would either reduce impacts or facilitate <br />their assessment. <br />1.0 INTRODUCTION <br />A recurrent theme in Durango's discussions of in-stream gravel mining for at least 20 years has <br />been the need to mine sustainably, by managing extraction volumes and practices to avoid <br />excessive environmental impacts and to balance natural gravel supply. When USACE prepared <br />the current permits, it moved toward this goal by creating uniform requirements for all operators <br />and by adding procedures for annual monitoring and regulatory review. If the original permit <br />requirements had been enforced, the period since late 1996 would have provided a rigorous test <br />of the practices needed to mine sustainably. In reality, USACE loosened or did not immediately' <br />enforce some permit requirements. Natural rates of gravel replacement were generally low, so <br />mining also impacted the river more than it would have if larger spring floods had occurred. <br />During the past seven years, impacts from in-stream mining have continued. A simple indicator <br />of these impacts is average channel incision of approximately 2.9 ft at the Bar-D Fit, 3.1 ft at the <br />Hermosa Meadows Pit, and 1.9 ft at the Dalton Pit (where extraction was well below the <br />permitted limit). Since 1977, available data suggest net incision ranging from approximately S to <br />Gillam to Hellige, Nov. 28, 2003 page 1 <br />