## 3 Results and Discussion
However, since As seems to follow the other elements, it is likely that background As levels in soils are reached at the same distances that background concentration are reached by all other elements measured. Interestingly, the crustal abundance for As is 10 ppm, and, the background concentrations of all other elements measured in this study are close to the crustal abundances listed in reference [31]. Figure 4 is a Google(r) photo of the mine site showing the two major housing projects, Lake Las Vegas and Calico Ridge. The partial sampling radii are shown for 0.8 km, 1.6 km, 3.2 km and 4.8 km. The 1.6 km radius just shy of the eastern edge of Calico Ridge and the 3.2 km radius cross through the NW edge of Calico Ridge. Soil samples are at background levels for all of the chemical elements before reaching Calico Ridge's eastern edge. There are houses in Lake Las Vegas at the 0.8 km, 1.6 km, and 3.2 km radii. Unfortunately, no transects were taken going to the N and NW, because of the extensive anthropogenic activity since 1980: house construction, road building, landscaping and construction of weirs on the Las Vegas Wash. The wind rose diagram in Figure 3 shows that there are low frequency winds from the S, SSE and SE, which have episodes of winds with speeds of \(>\)5 m/s. Along with wind devils that occur periodically, one could speculate that there is transport of tailings to the N, NNW and NW to 0.8 km. Also, there is transport of tailings to 0.8 km on all transects, except Transect 7 (which goes west). Transect 1 passes through the light gray new home sites across Lake Mead Parkway. These future home sites are on this NE transect between 0.4 km and 2.3 km downwind from the tailings ponds, in an area highly impacted by tailings which exceed the USEPA RSLs. In the NE corner of the tailings ponds (Figure 4), there is a short white line near the base of the Transect 1 arrow. This is a bike rental-boat storage business. It is definitely impacted by tailings transport to the NE. At the base of the tailings ponds is a water culvert, where the black arrow crosses Lake Mead Parkway. It is apparent that water runoff from the tailings ponds does not carry tailings downhill to the City of Henderson, but is almost immediately channeled to this culvert which goes \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Element** & **Tailings** & **Background** & **Tailings/** & **Natural abundance** & **EPA’s RSL** & **Tailings/** \\  & **(mg/kg)** & **(mg/kg)** & **background** * & **(mg/kg)** & **(mg/kg)** & **RSL** \\ \hline Mn & \(1.53\times 10^{5}\) & 580 & 264 & 440 & \(1.8\times 10^{3}\) & 85 \\ Fe & \(4.08\times 10^{4}\) & \(2.5\times 10^{4}\) & 1.63 & 0.5–\(5\times 10^{4}\) & 5.5 \(\times 10^{4}\) & 0.7 \\ Cu & 260 & \(<\)50 & 13 & 20 & \(3.1\times 10^{3}\) & 0.084 \\ Zn & 2050 & 69 & 30 & 64 & \(2.3\times 10^{4}\) & 0.089 \\ As & 3690 & \(<\)10 & 369 & 10 & \(6.1\times 10^{-1}\) & 6000 \\ Rb & 120 & 79 & 1.5 & 30–250 & & \\ Sr & \(1.87\times 10^{4}\) & 730 & 26 & \(18\)–\(3.5\times 10^{3}\) & \(4.7\times 10^{4}\) & 0.40 \\ Zr & 190 & 360 & 0.5 & 35–550 & & \\ Mo & 44 & \(<\)5 & 22 & 2 & \(3.9\times 10^{2}\) & 0.11 \\ Pb & \(1.53\times 10^{4}\) & 43 & 356 & 23 & \(4.0\times 10^{2}\) & 38 \\ \hline \hline \end{tabular}
* Natural abundance used if “background” less than LOD.  
\end{table} 
Table 1: Concentrations of the elements in the tailings, “background”, tailings/“background”, natural abundance [31], U.S. Environmental Protection Agency’s (EPA’s) RSL (Regional Screening Levels) and the tailings/RSL [2]. under Lake Mead Parkway (the black arrow in Figure 4) onto property belonging to the Lake Las Vegas Resort. It ultimately goes into the Las Vegas Wash. Before Lake Las Vegas was built, the runoff from the tailings ponds flowed freely downhill to the Las Vegas Wash, which in turn discharged into Lake Mead. In addition, in Figure 4, is Lake Las Vegas, a man-made lake. The Las Vegas Wash flows under this lake on its way to Lake Mead.