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However, the existing thalweg is now about 3.1 ft lower, on average, than its 1996 level. <br />If Hermosa Meadows Gravel mines this channel only to the 1996 thalweg level, the <br />channel would carry some peak flows but mining it may not prevent erosion in the target <br />area. (Ironically, this reach had multiple channels in 1996.) If mining diverts the river to <br />this now-abandoned channel, overall channel sinuosity would be decreased, thus <br />promoting further channel incision. <br />6.0 WALKER PIT <br />6.1 Operator <br />• Sandco, Inc. since before 1996 <br />6.2 Changes to Permit Special Conditions <br />Channel Monitorine Plan <br />Sandco said that it would establish two sections at an unspecified time to encompass only <br />the existing active mining area at the required horizontal spacing. <br />USACE formally accepted this plan, ensuring that baseline surveys would not be <br />conducted in 199b or throughout the pit during a single season. <br />Plan was silent on all other points in permit, which were not modified by plan <br />acceptance. <br />6.3 Compliance with Documentation Requirements <br />• The two cross sections were first surveyed during March, 1998, a little more than one <br />year. after the permit was signed, and no other sections have been added later (Table 8). <br />Therefore; no baseline data aze available for the low-flow channel that existed in late <br />1996/eazly 1997. <br />• Permit and Channel Monitoring Plan require 121ate summer orpre-mining surveys <br />(through spring 2003); 7 complete surveys and 3 partial surveys (omitting the thalweg) <br />were done. <br />• Permit and Channel Monitoring Plan require 12 spring orpost-mining surveys (through <br />spring 2003), but 10 were done. <br />• Permit and Channel Monitoring Plan require 6 late summer or pre-mining longitudinal <br />profiles (through spring 2003), but none were done. <br />• Permit and Channel Monitoring Plan require 6 spring orpost-mining longitudinal profiles <br />(through spring 2003), but none were done. <br />• No surveys were performed during the 2002-2003 mining season, so current pre-mining <br />data are not available for assessment. <br />• Sandco has used an arbitrary local elevation datum for the surveys (Table 9), preventing <br />comparison to data from other sources such as the 1977 flood study (USACE, 1977). <br />Gillam to Hellige, Nov. 28, 2003 page 13 <br />