2.7.19. Mill Creek About Mill Creek

Figure 2.51
Figure 2.52 The Mill Creek Tributary (WBID 2460).
  • East of the St. Johns River feeding into Sixmile Creek
  • Primary Land Use: Wetlands/forest
  • Current TMDL reports: Fecal Coliform, DO/Nutrient
  • Verified Impaired 2016 (final): Iron (high)
  • WBID Area: 11.6 sq. mi.
  • Beneficial Use: Class III F (Recreational – Freshwater) Data sources

Result data was downloaded from the FL STORET website (DEP 2010e) and filtered based on the stations (DEP 2010f) in Mill Creek WBID2460 (DEP 2014d) shown above. The filtered dataset was used to generate Table 2.20. Discussion

Water quality data for Mill Creek are shown in Table 2.20. The fecal coliform level, averaged over all the stations in Mill Creek, is above the critical level of 2.6, which is the logarithm of the state maximum of 400 colony-forming-units (cfu) per 100 mL. Thus, a TMDL for fecal coliform was published in 2009 (Rhew 2009b). (Note: the data analyses in the TMDL are based on different criteria than that used in this report). In addition, Mill Creek has been identified as impaired for dissolved oxygen and associate nutrients and a TMDL addressing this was published in 2010 (Magley 2010). Iron has been added in the recent revised verified impaired list (DEP 2016j) for Mill Creek and is potentially a natural condition, common in Florida blackwater streams such as this.

Table 2.20 Water quality data for Mill Creek.
ParameterWater Quality Criteria (SW)LowAverageHighSamplesSampling Period
Dissolved Oxygen (mg/L)34% sat. (~3.0)2.385.429.561152002 - 2013
Total Nitrogen (mg/L)<1.54‡ - 2013
Total Phosphorus (mg/L)<0.12‡ - 2013
Chlorophyll-a (μg/L)<20‡07.2750672002 - 2013
Arsenic (μg/L)≤500.031.684.64582005 - 2009
Cadmium (μg/L)≤0.300.050.19562005 - 2009
Copper (μg/L)≤9.30.552.357.51742005 - 2009
Lead (μg/L)≤ - 2009
Nickel (μg/L)≤520.090.63.74442005 - 2008
Silver (μg/L)≤0.0700.080.4482006 - 2009
Zinc (μg/L)≤1200.874.4732.2732005 - 2009
Fecal Coliform (log #/100 mL)<2.6‡ - 2008
Turbidity (NTU)<291.98.73130662002 - 2012
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.