## 3 Results and Discussion
### Septic System Density
Road salts are not routinely applied throughout winters in the study area due to milder winters yielding infrequent snow and ice storms. However, the January 2016 sampling event occurred several days after a snowstorm hit the area when road salts were likely used, thus explaining the larger variability and sudden increase in chloride and specific conductance in all watersheds (Figure 3). Median _E. coli_ and enterococci loadings increased with septic system density for the SF watersheds (Figure 4; Table 2) but the same was not observed for the CS watersheds. Despite the observed differences in median values, FIB loadings data were too variable to find significant differences. When isolating density effects in the SF watersheds, statistical tests were nearly significant (\(p\) = 0.053) between the SF3 and SF1 watershed for _E. coli_ and enterococci loadings. These same trends were not observed in the conventional septic watersheds, likely due in part to a prolonged period of little to no flow in the CS3 watershed. From June-October 2015, the CS3 watershed was dry or contained disconnected pools of stagnant water, which explains the large variability in the FIB loading data for this watershed (Figure 4). Research in Georgia [24] and North Carolina [15; 16] showed median FIB exports typically ranged from 191-1116 and 101-721 MPN s\({}^{-1}\) ha\({}^{-1}\) for _E. coli_ and enterococci, respectively, for watersheds with \(\geq\)0.9 systems ha\({}^{-1}\). In the current study, watersheds with septic systems contained densities that other studies [16; 24] classified as low density (<1 system ha\({}^{-1}\)). [PERSON] et al. [24] reported a mean density of 0.22 systems ha\({}^{-1}\) for low density watersheds, and these watersheds exported a mean value of approximately 200 and 450 MPN s\({}^{-1}\) ha\({}^{-1}\) of _E. coli_ and enterococci, respectively. [PERSON] et al. [16] reported median values of 80 and 24 MPN s\({}^{-1}\) ha\({}^{-1}\) for _E. coli_ and enterococci from watersheds with a median septic system density of 0.15 systems ha\({}^{-1}\). In the current study, median _E. coli_ and enterococci exports ranged from 35-151 and 11-66 MPN s\({}^{-1}\) ha\({}^{-1}\), respectively (Table 2). These exports overlapped with FIB yields (_E. coli_: 0.8-2559 MPN s\({}^{-1}\) ha\({}^{-1}\)  
Figure 3: Chloride (**A,C**) and specific conductance (**B,D**) values from watersheds grouped by wastewater treatment approach and increasing septic system density. Pooled data are shown for each group as CS = conventional septic; SF = sand filter; SEW = sewer. The asterisks (*) denote outliers. enterococci: 2-5382 MPN s\({}^{-1}\) ha\({}^{-1}\)) reported in the aforementioned studies from watersheds with \(<\)0.9 systems ha\({}^{-1}\)[16; 24]. Previous studies have shown that watersheds with septic system densities greater than 1 system ha\({}^{-1}\) can contain substantially elevated FIB concentrations and exports relative to watersheds with lower septic system densities or without septic systems [15; 16]. However, [PERSON] et al. [24] reported similarities in FIB concentrations and exports at the watershed scale regardless of septic system density. As noted earlier, their low-density watersheds exhibited substantial variability in non-point sources of FIB because of land use, whereas high-density watersheds were mostly residential developed lands (approximately 70%) with less forest and agricultural cover. In the current study, results suggest that water quality impacts may be observed at lower densities than observed by previous studies. Watersheds with septic system densities of 0.4 systems ha\({}^{-1}\) contained elevated FIB concentrations that were statistically different from watersheds containing densities of approximately 0.2 systems ha\({}^{-1}\). In addition to density, watershed-scale FIB concentrations could be affected by the distance from the septic system to watershed outlets.