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<br />Mary L. Gillam, Ph.D. <br />~~~~ . <br />Consalting Geologist <br />115 Meadow Road East -' ~ ~- ~ 9 ~ ~ - b lr <br />Durango, CO 81301-7093 <br />970-259-09661970-259-6064 fax <br />gillam@rmi.net <br />- ~I~~O ~@ ~.. <br />November 28, 2003 <br />Ms. Kara A. Hellige <br />DEC ~ ,, ~3 h <br />Orvisi°golrytjneral u~C <br />Chief, Durango Regulatory Office sd"~s°0~°g ~ ~ ~~~3 ~ <br />dur~ <br />" 278 Saw e ~Dri e #lEngineers, Sacramento District lonof~~he ~ ~~eet <br />Durango, CO 81303-7916 ~9Y <br />/~ <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 maybe granted until November 30, 2004, and new permits <br />maybe issued for mining after that time. To assist yau, 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 far 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. 1n reality, USACE loosened or did not immediately" <br />enforce some permit requirements. Natural rates of gravel replacement were generally low, sc I <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 indict <br />of these impacts is average channel incision of approximately 2.9 ft at the Bar-D Pit, 3.1 ft at <br />Hermosa Meadows Pit, and 1.9 ft at the Dattan Pit (where extraction was well below the <br />permitted limit}. Since 1977, available data suggest net incision ranging from approximatel° <br />Gillam to Hellige, Nov. 2$, 2003 page 1 <br />