2012-01-06_PERMIT FILE - C1982057A ‎(4)‎

• Permit No: C1982057A
• IBM Index Class Name: Permit File
• Doc Date: 1/6/2012
• Section_Exhibit Name: Tab 17 Probable Hydrologic Consequences
• Media Type: D
• Archive: Yes

be negligible, because these structures have been designed to minimize impacts to the •
hydrologic balance (see Tab 13, Facilities). The diversions and culverts involve such
minor areas of disturbance that changes in chemistry and sediment loads in discharges
through these structures will be unmeasu ra ble.
Effects of Runoff from Reclaimed Areas on the Quantity of Streamflow. The effects of
runoff from reclaimed areas proposed at the Seneca II-W Mine on Streamflow quantity
(runoff and sediment loads) have been estimated using the lumped-parameter computer model
SEDIMOT II. The impacts of runoff from reclaimed areas established at the Seneca II-W
Mine are inferred from this modeling exercise. Input parameters take into account
precipitation, soils, topography, and vegetation. Adjustment of these parameters allows
for the evaluation of watershed response changes resulting from mining activities.
Input parameters selected for the model reflect both premining and postmining (reclaimed)
conditions, and resulted in two separate model outputs: 1) premining runoff and sediment
loadsl and 2) postmining runoff and sediment loads. Both outputs include runoff volumes
and rates (peak discharge), sediment concentrations, and sediment yields. The following
paragraphs discuss the scope of the modeling effort, the selection of input parameters, •
surtmaries of nadeling results, and a section which discusses the significance of the
modeling results. The reader should refer to the SEDI MOT II Manual on Modeling Techniques
(Wilson, et al., 1981) and the SEDIMOT II User's Manual (Warner et al., 1961) for
reference.
The watershed areas directly above both Pond 006 and proposed Pond 005 were selected for
estimating runoff and sediment loads using SEDIMOT II. Mining will disturb more than 80
percent of the watersheds above both ponds. Mining related disturbances in the tributary
to Sage Creek above proposed Pond 009 will be considerably smaller in extent. Inferences
about impacts made using SEDIMOT II to model both the 005 and 006 pond watersheds can be
applied to the area above Pond 009. Exhibit 17-2 depicts watershed boundaries used for
modeling premining conditions in both the 005 and 006 Gulch drainages. Exhibit 17-3,
which includes the proposed postmining topography in the upper portions of both the 005
and 006 Gulch drainages, portrays watershed boundaries used for modeling postmining
conditions in both watersheds.
Model results generated for premining conditions reflect that no mining-related activities •
have occurred within the watershed boundaries, and that associated input parameters
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