REV101480

• Permit No: M1974015
• IBM Index Class Name: Revision
• Doc Name: EXHIBIT G WATER INFORMATION
• Type & Sequence: AM6
• Media Type: D
• Archive: No

• • ~r1C
Mr. Scott Gudahl
January 28, 1997
Page 4
500 to 1,000 feet downstream of a lined pond. There are no known wells within 500 to 1,000 feet
of the ponds west of the cement plant. Consequently, these ponds should not impact water users.
The shadow effect downgradient of the proposed southeast lined pond is judged to have little or no
impact to water users near the Zapf or Darby wells due to distance from the pond and the presence
of the South Branch. The shadow effect will, however, impact wells on the south side of Hygiene
Road between Foothills Reservoir and just east of 61st Street. However, Impacts to these wells can
be mitigated by engineering an infiltration structure on the south side of the pond and applying
water from the pond or other sources.
SUMMARYAND CONCLUSIONS
Hydrogeologic conditions at the site and surrounding area are monitored with a system of
37 wells and staff gauges installed by Western Mobile. Data collected from the wells
indicates a high degree of connection between surface water and groundwater.
Laboratory analyses of groundwater samples at and near the site indicates total coliforms in
the area commonly exceed human health standards. In addition, dissolved manganese and
dissolved iron commonly exceed secondary drinking water standards. Groundwater in the
area should be treated prior to human consumption.
Groundwater from alluvial wells is the primary water source for domestic and/or stock water
for many of the site's neighbors. Details regarding locations, depths, yields, and
construction of these wells are not known. However, in our experience, these wells tend to
be shallow, hand-excavated, and inefficient.
Inefficient wells are highly susceptible to minor fluctuations (two to three feet) of the water
table.
Some wells, surface water features, and wetlands will be impacted by dewatering activities
during mining. These impacts can be mitigated by strategically applying dewatering
discharge or other available water in ways that maintain groundwater levels near affected
wells, surface water features, and wetlands. In addition, ditches may be lined to minimize
seepage losses.
Groundwater level impacts after reclamation on the north side of the proposed slurry wall
paralleling St. Vrain Creek and the South Branch are judged to be minimal (less than two to
three feet). Impacts on the south side of the slurry wall can be mitigated by strategically
applying available water and/or constructing slurry walls around wetlands and lining ditches
where they cross the alluvium to minimize seepage losses.
Groundwater levels at the Shupe residence and east of 61st Street are expected to be close
to pre-mining conditions because unlined ponds, the slurry wall, and the South Branch will
tend to maintain the water table in this area. Consequently, impacts to wells are judged to
be minimal. Water levels on the south side of Hygiene Road will be impacted by the