2.7.27. Sixmile Creek About the Sixmile Creek

Figure 2.61
Figure 2.62 The Sixmile Creek Tributary (WBID 2411).
  • East of the St. Johns River in St. Johns County
  • Primary Land Use: Forested/Wetland
  • Current TMDL reports: None
  • Verified Impaired 2016 (final): None
  • WBID Area: 59.5 sq. mi.
  • Beneficial Use: Class III F (Recreational – Freshwater) Data sources

Result data were downloaded from the FL STORET website (DEP 2010e) and filtered based on the stations (DEP 2010f) in the Sixmile Creek WBID 2411 (DEP 2014d) shown above. The filtered dataset was used to generate Table 2.28. Discussion

Water quality data for Sixmile Creek are shown in Table 2.28. Dissolved oxygen levels in Sixmile Creek are relatively low, compared to other tributaries (Figure 2.41); however, this is likely attributed to the wetland areas surrounding the creek and therefore it is not listed as impaired (DEP 2009c). Chlorophyll-a levels have exceeded WQC in the past but recent data have shown levels are decreasing, and now the average is below the water quality criteria (20 µg/L) for freshwater streams. Silver levels are elevated, yet this has not been identified as an impairment.

Table 2.28 Water quality data for the Sixmile Creek.
Water QualityConcentrationSampling
ParameterCriteria (FW)LowAverageHighSamplesPeriod
Dissolved Oxygen (mg/L)34% sat. (~3.0)0.585.2610.822771997 - 2015
Total Nitrogen (mg/L)<1.540.521.041.861721997 - 2014
Total Phosphorus (mg/L)<0.120.0090.090.673551997 - 2014
Chlorophyll-a (µg/L)<200.0511.493.452191997 - 2015
Arsenic (µg/L)≤500.092.5822.111091997 - 2011
Cadmium (µg/L)≤0.300.193.741101997 - 2011
Copper (µg/L)≤ - 2011
Lead (µg/L)≤3.2018.021261997 - 2011
Nickel (µg/L)≤5203.498.71251997 - 2011
Silver (µg/L)≤0.0700.293.41951997 - 2011
Zinc (µg/L)≤1200.274.8332.721621997 - 2011
Fecal Coliform (log #/100 mL)<
Turbidity (NTU)<290.52.6833.52101997 - 2015
Note: Hardness-dependent freshwater criteria for cadmium, copper, lead, nickel, and zinc were generated based on a hardness concentration of 100 mg/L.
FW = freshwater; SW = saltwater (marine). Values denoted with (*) indicate a proposed criterion, which has not yet been adopted.
Values denoted with (†) are reference values based on EPA criteria (EPA 2010b), but the water body is not regulated by this standard.