2.7.10. Dunns Creek/Crescent Lake

2.7.10.1. About Dunns Creek/Crescent Lake

Figure 2.40
Figure 2.41 The Dunns Creek/Crescent Lake Tributary (WBID 2606A/B).
  • East of the St. Johns River in Flagler County
  • Primary Land Use: Forested/Wetlands
  • Current TMDL reports: Mercury – 2606B, Nutrients – 2606B (draft)
  • Verified Impaired 2016 (final): Fecal Coliform (2606A low), Nutrients (Chlorophyll-a, Total P 2606B med)
  • WBID Area: 585 sq. mi.
  • Beneficial Use: Class III F (Recreational – Freshwater)

2.7.10.2. Data sources

Result data was downloaded from the FL STORET website (DEP 2010e) and filtered based on the stations (DEP 2010f) in the Dunns Creek/Crescent Lake WBIDs 2606A/B (DEP 2014d) shown above. The filtered dataset was used to generate Table 2.11, with freshwater stream WQC’s reported. These should be regarded as guidelines only because Dunns Creek (2606A) is accessed as a stream, Crescent Lake (2606B) is accessed as a lake and has different WQC’s.

2.7.10.3. Discussion

Water quality data for Dunns Creek/Crescent Lake are shown in Table 2.13. This tributary is a significant non point-source contributor to nutrient levels in the St. Johns River (Magley and Joyner 2008). There is a significant variation of dissolved oxygen going upstream of the creek and into the lake as evidenced by the wider spread of values in Figure 2.41.

Dunns Creek (WBID 2606A) was identified as being impaired for mercury, based on elevated levels of mercury in fish tissue, however this is being delisted (DEP 2016h) as it has been addressed by the statewide mercury TMDL (DEP 2013e). In addition, a TMDL for Nutrients was recently drafted (Bubel 2015) for Crescent Lake based on its Trophic State Index (TSI), calculated from the total nitrogen (TN), total phosphorus (TP), and chlorophyll-a levels. Crescent Lake is listed on the revised verified list for chlorophyll-a and total phosphorus (DEP 2016j).

Table 2.11 Water quality data for Dunns Creek/Crescent Lake.
Water QualityConcentrationSampling
ParameterCriteria (FW)LowAverageHighSamplesPeriod
Dissolved Oxygen (mg/L)34% sat. (~3.0)07.5116.9324751997 - 2016
Total Nitrogen (mg/L)<1.540.531.33.249561997 - 2015
Total Phosphorus (mg/L)<0.1200.070.5128711997 - 2016
Chlorophyll-a (µg/L)<200.1519.89198.1114311997 - 2016
Arsenic (µg/L)≤5001.55.774391997 - 2016
Cadmium (µg/L)≤0.300.071.023861997 - 2016
Copper (µg/L)≤9.301.43392.97161997 - 2016
Lead (µg/L)≤3.200.795.364611997 - 2016
Nickel (µg/L)≤5201.1153.263591997 - 2016
Silver (µg/L)≤0.0700.131.163451997 - 2016
Zinc (µg/L)≤12003.35133.77641997 - 2016
Fecal Coliform (log #/100 mL)<2.6-0.30.653.681241998 - 2013
Turbidity (NTU)<290.655.4735.414291997 - 2016
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.
Figure 2.41
Figure 2.42 Variation of the dissolved oxygen in Dunns Creek and Crescent Lake going upstream (left to right) Note: The data in this graph are not consistent in sampling interval and/or timeframe.