GENERAL41964 - Laserfiche WebLink

Home Browse Search

• Gravel will be mined as much as 6 ft below the January, 1996 thalweg elevation (text); in practice, this limit will be identified as approximately 5 ft below either the existing water table or channel bed (Appendix A). • Mining will be conducted such in a manner that the thalweg will never drop more than 6 ft below its level in January, 1996 (text and Appendix B). • The existing channel gradient will be maintained (Appendix B). • Bank stability will be maintained by not mining in a 25-ft buffer zone next to the banks (Sheet 1), and by rip-rapping as needed (text, Appendix B). • The river bed will be left in a braided condition to spread flows and reduce erosion, if necessary by excavating artificial channels after mining (text, Appendix A). Initial Permit Conditions and Later Amendment When executed in January, 1997, the permit did not incorporate these provisions; most importantly, it applied the same excavation depth limit to Bar-D as to all other pits (no mining below the existing low flow channel level). Roughly one month later, in an undated letter that USACE received on February 13, 1997, Sugnet & Associates requested that USACE amend the mining depth limit in the permit to "not more than six (6) feet below the elevations of the low flow channels, as surveyed on January 3, 1996." USACE accepted this permit change as well as the mining and channel monitoring plans contained in the 1996 report (Art Champ to Ronald Pettigrew, 5/19/97). Sugnet & Associates chazacterized the new depth limit as a "minor modification" although it gave the Bar-D operators an unfair business advantage and increased mining impacts. 3.3 Compliance with Documentation Requirements and Recent Requests • Baseline thalweg elevations were established during January, 1996, earlier than at other pits. • Most adjacent cross sections are approximately 100 to 400 ft apart, but two are approximately 500 to 550 8 apart. • Cross sections and longitudinal profiles were obtained once per mining season during most (but not all) seasons after the permit was signed. • To date, USACE has received one survey for each cross section during 5 of 7 mining seasons after the permit was signed, for a total of 65 surveys; in comparison, the monitoring plan (text) promised two surveys of each cross section per year, or a total of 182 surveys (Table 1). • Cross sections were not included in the first two "Bank Stabilization and Channel Survey" reports, but when provided they showed all prior surveys. • It appears that all of the surveys furnished so far depict pre-mining conditions as defined here (see Section 2.0). This interpretation is based on specific mining dates for the last four years (Paul Sugnet to Kara Hellige, 10/16/03) and the fact that earlier surveys were done about the same time of yeaz. In contrast, Sugnet & Associates (later renamed Sugnet Environmental) regazds these as post-mining surveys (Sean Moore to Lesley McWhirter, 8/25/03). Gillam to Hellige, Nov. 28, 2003 page 4