2.7.9. Doctors Lake

2.7.9.1. About Doctors Lake

Figure 2.38
Figure 2.39 The Doctors Lake Tributary (WBID 2389 and 2410).
  • West of the St. Johns River in Clay County
  • Primary Land Use: Forested
  • Current TMDL reports: Nutrient – 2389 (draft), DO/Nutrient – 2410 (draft), Silver – 2389/2410
  • Verified Impaired 2016 (final): Nutrients (Chlorophyll-a 2389 med), Nutrients (Total P 2389 med)
  • WBID Area: 8.4 sq. mi.
  • Beneficial Use: Class III F (Recreational – Freshwater)

2.7.9.2. Data sources

Result data was downloaded from the FL STORET website (DEP 2010e) and filtered based on the stations (DEP 2010f) in Doctors Lake WBIDs 2389 and 2410 (DEP 2014d) shown above. The filtered dataset was used to generate Table 2.10, with freshwater stream WQC’s reported. These should be regarded as guidelines only because Swimming pen creek (2389) is accessed as a stream, Doctors Lake (2410) is accessed as a lake and has different WQC’s.

2.7.9.3. Discussion

Water quality data for Doctors Lake are shown in Table 2.10. Although average total nitrogen and total phosphorus levels were within their WQC limits, average chlorophyll-a concentrations far exceeded the WQC, particularly in summer months (Figure 2.40), and average dissolved oxygen levels are well above the SSAC. Thus, Doctors Lake has been identified as being impaired for nutrients (chlorophyll-a and total phosphorus) (DEP 2016j), and the final TMDL report to address this has been published (Magley 2009e). Elevated maximum arsenic, cadmium, copper, nickel, silver, and zinc concentrations were also measured in Doctors Lake, and as a result, EPA has published a Silver TMDL (EPA 2010a). Doctors Lake is largely used for recreational activities such as boating, fishing, and waterskiing. These activities could account for some of the copper, nickel, and zinc contamination; however, the source of the other contamination is not clear. Two small creeks that flow from swampland merge and enter the lake from the south and the lake enters the mainstem of the LSJR from the northeast through the Doctors Inlet.

Table 2.10 Water quality data for Doctors Lake.
Water QualityConcentrationSampling
ParameterCriteria (FW)LowAverageHighSamplesPeriod
Dissolved Oxygen (mg/L)34% sat. (~3.0)08.0215.5416781997 - 2016
Total Nitrogen (mg/L)<1.540.311.213.779541997 - 2015
Total Phosphorus (mg/L)<0.1200.080.4824791996 - 2016
Chlorophyll-a (µg/L)<200.3628.45198.5411061997 - 2016
Arsenic (µg/L)≤5004.5685.65051997 - 2016
Cadmium (µg/L)≤0.300.34.194011997 - 2016
Copper (µg/L)≤9.302.39246.557381997 - 2016
Lead (µg/L)≤3.202.1426.985431997 - 2016
Nickel (µg/L)≤5203.66117.83191997 - 2016
Silver (µg/L)≤0.0700.34.383451997 - 2016
Zinc (µg/L)≤1200.045.38128.17751997 - 2016
Fecal Coliform (log #/100 mL)<2.6No valid data available
Turbidity (NTU)<290.96.414910981997 - 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 2.40
Water quality data for Wills Branch are shown in Table 2.31. Average total phosphorus, total nitrogen, dissolved oxygen and chlorophyll-a concentrations were within acceptable limits. The fecal coliform level, averaged over all the stations in Wills Branch, are above the critical level of 2.6, which is the logarithm of the state maximum of 400 colony-forming-units (cfu) per 100 mL. As a result, a TMDL for total and fecal coliform was published in 2006 (Wainwright 2006c) for Wills Branch. (Note: the data analyses in the TMDL are based on different criteria than that used in this report). Subsequently, a BMAP for Wills Branch was legally adopted in 2010 (DEP 2010a). Annual Progress Reports for this BMAP were published in 2011 (DEP 2011b), 2012 (DEP 2013b), and 2013 (DEP 2013b); they list repairs, inspections, evaluations, and other improvements conducted by JEA, the Duval County Health Department, COJ, and FDOT.