2.7.16. Intracoastal Waterway

2.7.16.1. About the Intracoastal Waterway

Figure 2.45 The Intracoastal Waterway Tributary (WBID 2205C) with sanitary sewer overflows reported by JEA in 2019 (JEA 2019b).
Figure 2.45 The Intracoastal Waterway Tributary (WBID 2205C) with sanitary sewer overflows reported by JEA in 2019 (JEA 2019b).

 

  • Near the mouth of the St. Johns River
  • Primary Land Use: Marsh/Wetland (Land Cover)
  • Current TMDL reports:
    Mercury
  • 2016 Verified Impairment for
    Fecal Coliform and Iron (2205C)
  • WBID Area: 23.9 sq. mi.
  • Beneficial Use: Class III M (Recreational – Marine)

2.7.16.2. Data sources

Data were downloaded from the FL STORET and WIN websites (DEP 2010f; DEP 2018c) and filtered based on the stations (DEP 2010g) in the Intracoastal Waterway (ICW) WBID 2205C (DEP 2014c) shown above. The filtered dataset reflects water column concentrations and was used to generate Table 2.17.

2.7.16.3. Discussion

Water quality data for the ICW are shown in Table 2.17. The ICW does not appear to provide a significant nutrient load to the St. Johns River. Arsenic concentrations are higher compared to other tributaries, although those concentrations have decreased over the past three years. Many of the listed metals (such as cadmium, copper, lead, and zinc) increased in concentration in 2018 and remained elevated in 2019; numerous water samples exceeded the WQC for copper. 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 is impaired for iron and fecal coliform (DEP 2016j).  FDEP considers the ICW a low priority for development of a TMDL to address fecal coliform and a medium priority for development of a TMDL to address iron.  Limited fecal coliform measurements were available prior to 2019, but the average fecal coliform level in 2018 and 2019 exceeded the WQC.

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

Table 2.17 Water quality data for the Intracoastal Waterway.

 Water QualityAverage and Number of Samples º
ParameterCriteria (SW)201720182019
Dissolved Oxygen (mg/L)≥4.05.66
(1 of 14 samples)
6.20
(0 of 24 samples)
6.13
(1 of 24 samples)
Total Nitrogen (mg/L)<1.54Not availableNot available0.50
(0 of 3 samples)
Total Phosphorus (mg/L)<5.44.20
(2 of 9 samples)
0.10
(1 of 22 samples)
0.06
(0 of 6 samples)
Chlorophyll-a (µg/L)<114.20
(0 of 9 samples)
4.57
(5 of 11 samples)
2.00
(0 of 3 samples)
Arsenic (µg/L)≤5010.99
(0 of 10 samples)
6.36
(0 of 22 samples)
20.0
(0 of 6 samples)
Cadmium (µg/L)≤8.80.18
(0 of 10 samples)
0.50
(0 of 22 samples)
0.50
(0 of 6 samples)
Copper (µg/L)≤3.71.36
(0 of 10 samples)
4.36
(17 of 22 samples)
4.67
(5 of 6 samples)
Iron (mg/L)≤0.3Not available0.23
(10 of 22 samples)
0.14
(0 of 6 samples)
Lead (µg/L)≤8.50.11
(0 of 10 samples)
0.50
(0 of 22 samples)
0.50
(0 of 6 samples)
Nickel (µg/L)≤8.30.58
(0 of 10 samples)
1.00
(0 of 22 samples)
1.00
(0 of 6 samples)
Silver (µg/L)≤0.92*0.01
(0 of 10 samples)
0.50
(0 of 22 samples)
0.50
(0 of 6 samples)
Zinc (µg/L)≤863.02
(0 of 10 samples)
5.00
(0 of 22 samples)
5.00
(0 of 6 samples)
Fecal Coliform (CFU/100 mL)<400Not available1100
(1 of 1 sample)
750
(3 of 11 samples)
Turbidity (NTU)<296.98
(0 of 9 samples)
6.13
(0 of 10 samples)
3.26
(0 of 3 samples)
Note: Hardness-dependent freshwater criteria for cadmium, copper, lead, nickel, and zinc were generated based on a hardness concentration of 100 mg/L.
° = Number of samples below Water Quality Criteria for Dissolved Oxygen; Number of samples above Water Quality Criteria 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.