Tucker Chapman and Faculty Mentor: Greg Carling, Department of Geology

Introduction

Snake Creek is a tributary to the Provo River, which is an important water source for over two million people along the Wasatch Front. Arsenic concentrations in Snake Creek exceed the EPA limit of 10 μg/L and mixing water in the Provo River exceed the EPA (recommended level) of 1 μg/L. Snake creek contributes about 20% to the overall flow of the Provo River. This study focused on the probable source of arsenic in snake creek. Hot springs and faults are probable causes for high trace element contamination are were the focus of this study.

Methods

In order to determine a probable source for the Arsenic contamination in Snake Creek we sampled springs, and streams near Midway, UT. Stream samples were taken at three times during the 2014 water year at five sites along Snake Creek. A “clean hands/dirty hands” system was used to minimize contamination. Thirteen springs, including seven hot springs, in the Midway, UT area were sampled once in June 2014. Arsenic concentrations were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) at the University of Utah.

Results

It was found that Snake Creek headwaters have very low concentrations of arsenic and other trace elements. The springs near the headwaters are also low in arsenic and trace elements. Hot springs located in Midway along a fault line have very high concentrations of arsenic. Snake Creek mixing with the Provo River dilutes the arsenic concentrations but arsenic loads are not affected by dilution.

Figure 1: Charts of arsenic concentrations in Snake Creek and nearby streams. All hot springs are before the SC in Midway location. High groundwater levels in the area cause the stream to mix with water from hot springs.

Discussion

The headwaters of Snake Creek have very low concentrations of arsenic. There are other springs located near the confluence with the Provo River but these springs are also low in arsenic. Hot springs found along the path of Snake Creek have very high concentrations of arsenic and many other trace elements (figure 2). As Snake Creek flows past these hot springs groundwater mixing increases the concentrations of arsenic in Snake Creek to above EPA limit for drinking water. The hot springs in the area are the largest source for the high concentrations of arsenic found in Snake Creek. There are several faults in the midway, UT area that are the cause of the small concentration of hot springs. The water in the hot springs has circulated through plutonic rock and rose up along the faults in the area. High groundwater in the area causes active mixing between the hot springs and stream water. There has also been some historic mining activity in the area but it is unlikely that this activity has any effect on the arsenic concentrations of Snake Creek. The hot springs are a significant source of the arsenic found in Snake Creek.

Conclusion

Snake Creek inputs high concentrations of arsenic into the Provo River. We found that the hot springs found along the path of Snake Creek were a significant source of high concentrations of arsenic. Future sampling of springs in the area will help to better understand the chemistry of Snake Creek. Snake Creek is a small tributary but has a large impact on the overall chemistry of the Provo River.

Figure 2: Map of the Snake Creek watershed. Colors represent an interpolation of arsenic concentration using sampled springs. Highest concentrations of arsenic are near the hot springs. (Basemap is a hill shade created using USGS digital elevation models.)