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 2014c) shown above. The filtered dataset was used to generate Table 2.9, 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 2.9. 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 2013c).

This tributary is a significant non-point-source contributor to nutrient levels in the St. Johns River (Magley and Joyner 2008), and a TMDL for Nutrients was adopted (DEP 2017a) 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 final verified list for chlorophyll-a and total phosphorus (DEP 2016j).  Data for total phosphorus concentrations were available for Crescent Lake (2606B) for the past three years, but no new measurements of total phosphorus in Dunns Creek were available in STORET after 2014. The average total phosphorus concentration in Crescent Lake has hovered around the criterion value for colored lakes (0.05 mg/L) the past three years.

No recent measurements were available in STORET from 2015 to 2017 for the following parameter:

  • Fecal Coliform

Historical water quality data for this parameter in Dunns Creek/Crescent Lake are available in previous versions of the River Report.

Table 2.9 Water quality data for Dunns Creek/Crescent Lake (2015-2017).

 Water QualityAverage and Number of Samples º
ParameterCriteria201520162017
Dissolved Oxygen (mg/L)≥34% sat.
(≥3.0)
6.72
(4 of 81 samples)
7.62
(1 of 45 samples)
7.38
(0 of 18 samples)
Nitrate-nitrite N (mg/L)§§0.06
(32 samples)
0.04
(19 samples)
0.01
(6 samples)
Total Phosphorus (mg/L)<0.050.05
(28 of 54 samples)
0.06
(19 of 33 samples)
0.04
(6 of 16 samples)
Chlorophyll-a (µg/L)<2019.56
(13 of 32 samples)
17.98
(5 of 20 samples)
24.96
(5 of 8 samples)
Arsenic (µg/L)≤501.03
(0 of 29 samples)
0.88
(0 of 17 samples)
0.92
(0 of 8 samples)
Cadmium (µg/L)≤0.30.02
(0 of 29 samples)
0.00
(0 of 17 samples)
0.06
(0 of 8 samples)
Copper (µg/L)≤9.30.51
(0 of 29 samples)
0.84
(0 of 17 samples)
0.76
(0 of 8 samples)
Lead (µg/L)≤3.20.40
(0 of 29 samples)
0.41
(0 of 17 samples)
0.36
(0 of 8 samples)
Nickel (µg/L)≤520.29
(0 of 29 samples)
0.30
(0 of 17 samples)
0.47
(0 of 8 samples)
Silver (µg/L)≤0.070.01
(0 of 29 samples)
0.00
(0 of 17 samples)
0.01
(0 of 8 samples)
Zinc (µg/L)≤1202.02
(0 of 29 samples)
1.29
(0 of 17 samples)
1.21
(0 of 8 samples)
Turbidity (NTU)<294.21
(0 of 24 samples)
4.33
(0 of 19 samples)
8.67
(0 of 7 samples)
Note: Hardness-dependent freshwater criteria for cadmium, copper, lead, nickel, and zinc were generated based on a hardness concentration of 100 mg/L.
º = Number of samples below WQC for Dissolved Oxygen, Number of samples above WQC for all other parameters
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.
§ = No water quality criterion has been established for Nitrate-Nitrite nitrogen. No Total Nitrogen data were available in STORET for 2015-2017.