2.7.16. Intracoastal Waterway

2.7.16.1. About the Intracoastal Waterway

Figure 2.48
Figure 2.49 The Intracoastal Waterway Tributary (WBID 2205C).
  • Near the mouth of the St. Johns River
  • Primary Land Use: Marsh/Wetland (Land Cover)
  • Current TMDL reports: Mercury
  • Verified Impaired 2016 (final): Fecal Coliform (low), Iron (med)
  • WBID Area: 23.9 sq. mi.
  • Beneficial Use: Class III M (Recreational – Marine)

2.7.16.2. Data sources

Result data were downloaded from the FL STORET website (DEP 2010e) and filtered based on the stations (DEP 2010f) in the Intracoastal Waterway (ICW) WBID 2205C (DEP 2014c) shown above. The filtered dataset was used to generate Table 2.14.

2.7.16.3. Discussion

Water quality data for the ICW are shown in Table 2.14. All parameters listed are within normal limits, although arsenic concentrations are higher compared to other tributaries.  Some metals (lead, silver) have decreased in concentration over the past three years, while the others have remained steady. Based on these data, the ICW is relatively healthy and does not appear to provide a significant nutrient load to the St. Johns River. The Intracoastal Waterway was identified as being impaired for mercury, based on elevated levels of mercury in fish tissue, which is addressed by the statewide mercury TMDL (DEP 2013c). The Intracoastal Waterway was also identified as being impaired for iron and fecal coliform (DEP 2016j); however, no new fecal coliform measurements have been reported in STORET since 2007.

No recent measurements were available in STORET between 2015 and 2017 for the following parameter:

  • Fecal Coliform

Historical water quality data for this parameter in the Intracoastal Waterway are available in previous versions of the River Report.

Table 2.14 Water quality data for the Intracoastal Waterway (2015-2017).

 Water QualityAverage and Number of Samples º
ParameterCriteria201520162017
Dissolved Oxygen (mg/L)≥4.05.67
(2 of 18 samples)
6.36
(0 of 6 samples)
5.66
(1 of 14 samples)
Nitrate-nitrite N (mg/L)§§0.06
(9 samples)
0.11
(3 samples)
0.04
(8 samples)
Total Phosphorus (mg/L)<5.43.53
(1 of 9 samples)
2.59
(0 of 3 samples)
4.20
(2 of 9 samples)
Chlorophyll-a (µg/L)<113.53
(0 of 9 samples)
2.59
(0 of 3 samples)
4.20
(0 of 9 samples)
Arsenic (µg/L)≤507.40
(0 of 16 samples)
18.19
(0 of 6 samples)
10.99
(0 of 10 samples)
Cadmium (µg/L)≤8.80.06
(0 of 16 samples)
0.09
(0 of 6 samples)
0.18
(0 of 10 samples)
Copper (µg/L)≤3.71.27
(0 of 16 samples)
1.19
(0 of 6 samples)
1.36
(0 of 10 samples)
Lead (µg/L)≤8.50.48
(0 of 16 samples)
0.14
(0 of 6 samples)
0.11
(0 of 10 samples)
Nickel (µg/L)≤8.30.30
(0 of 16 samples)
0.54
(0 of 6 samples)
0.58
(0 of 10 samples)
Silver (µg/L)≤0.92*0.08
(0 of 16 samples)
0.03
(0 of 6 samples)
0.01
(0 of 10 samples)
Zinc (µg/L)≤863.25
(0 of 16 samples)
2.70
(0 of 6 samples)
3.02
(0 of 10 samples)
Turbidity (NTU)<2919.96
(2 of 9 samples)
3.96
(0 of 3 samples)
6.98
(0 of 9 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.