2015-10-16_GENERAL DOCUMENTS - M1999120

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GANSER LUJAN & ASSOCIATES Hydrogeological and Environmental Consultants Figure 7 (Continued) Pre -Mining Bachofer 8-12-2015 RS 634,05 4910, 04 >e 48. w 4Bi 0 3700 4000 6060 8000 Sbim (a) Pm -Mining Bachcfer8-12-2015 Rs- D4- B- �J 48 Od 6 '04 3 4885 1 1 4675 6 of w 4870wd.x Contributions of Alluvial Flow In addition to mining activities altering topographic relief and floodplain characteristics, including the floodway and storage configurations, slurry wall construction around these open -pit aggregate mines has created subsurface flow constrictions, which cause alluvial groundwater to back up or mound behind these walls on the up -gradient side. Groundwater levels tend to decline on the down -gradient side. As a result, mounding has caused higher water levels than historic levels in the river alluvium upstream and adjacent to the Bachofer property and, as a secondary result, has induced greater groundwater flow into the river through this constriction. This phenomenon has been noted in modeling studies by the USGS (Arnold et al., 2010) and show a mounding effect where groundwater levels rise 2 to 4 feet on the south and east sides of lined pits across the river from the Bachofer property. Pre -Mining Bachofer 8-12-2015 RS- 1381101 3 1e 4885 1 EGPF3 WS PF 3 EGPF2 N8 PF 2 f4875 w EGPF1 WS I 48 -PF Goutl 4%6 13" 81• 0 1000 3100 3000 4600 SOOD 60av X00 8000 S61m(Iq Pre -Mining Bachofer 8-12-2015 RS 634,05 4910, 04 >e 48. w 4Bi 0 3700 4000 6060 8000 Sbim (a) Pm -Mining Bachcfer8-12-2015 Rs- D4- B- �J 48 Od 6 '04 3 4885 1 1 4675 6 of w 4870wd.x Contributions of Alluvial Flow In addition to mining activities altering topographic relief and floodplain characteristics, including the floodway and storage configurations, slurry wall construction around these open -pit aggregate mines has created subsurface flow constrictions, which cause alluvial groundwater to back up or mound behind these walls on the up -gradient side. Groundwater levels tend to decline on the down -gradient side. As a result, mounding has caused higher water levels than historic levels in the river alluvium upstream and adjacent to the Bachofer property and, as a secondary result, has induced greater groundwater flow into the river through this constriction. This phenomenon has been noted in modeling studies by the USGS (Arnold et al., 2010) and show a mounding effect where groundwater levels rise 2 to 4 feet on the south and east sides of lined pits across the river from the Bachofer property.