Silver Creek - Division of Water Quality - Utah.gov

Silver Creek Watershed TMDL Final Report
As the terrain flattens, flow velocities in the stream and from runoff events decrease and begin to
deposit the sediments from the upper watershed. Increased sediment deposition leads to
increased contamination at these locations (Park City, Silver Maple Claims, Meadow area).
The middle to lower reaches (Flood Plain, Richardson Flats, Meadow area) are substantially
flatter than the upstream reaches. These areas were used for tailing reprocessing and disposal.
The landscape is littered with mounds of contaminated mine tailings. The meadow area from just
below Richardson Flat to Atkinson is nearly completely covered with tailings. The stream
channel runs through tailings for a stretch of approximately 4 miles in this meadow area. The
contamination processes that are visually apparent include direct storm water runoff to the creek,
direct stream contact with tailings and shallow ground water contact with tailings. The ground
water table is fairly high and is believed to exchange freely with water in Silver Creek, thus
increasing the contaminant load in the stream.
The Silver Creek WRF is a relatively small source of zinc loading currently as it contributes
approximately only 598 of the 12,000 lbs per year of zinc passing the Atkinson Station (See
Table 8). This represents 5 percent of the total load at Atkinson. Additionally, none of the
samples for zinc obtained at the WRF in the 12-year period of this study exceeded the water
quality standard for zinc. However, once best management practices are implemented in Silver
Creek, the relative contribution of the WRF will become more significant. If growth projections
for the WRF are met, the discharge volume will grow from a current value of 1.4 MGD to 2.0
MGD in the next 10 years. This would result in the WRF contributing some 628 lbs. of zinc
annually to a combined load at Atkinson after BMP implementation of 4,810 lbs. (13% of the
combined load)
Cadmium levels have consistently been below the detection limit, indicating that the WRF does
not appear to be a contributor of cadmium to Silver Creek.
The last stream reach (to Wanship) has no tailings or other sources of contaminants besides
sediment loads within the stream. This reach is the only section of stream that exhibits reducing
levels of contaminants, again probably due to contaminants being adsorbed or precipitated.
Page 38