Middle St. Johns - Florida Department of Environmental Protection

478 Water Quality Assessment Report: Middle St. Johns
threshold of the IWR for mercury (in fish tissue), but they have been removed from
the verified list to the planning list, pending confirmation of the 7.5 year age of data.
Lake Harney (2964A) met the verification threshold of the IWR and we were able to
confirm the 7.5 year age of the data used in the assessment, therefore it has been
retained on the verified list. Verified mercury in fish tissue listings are not due for
TMDL development until the year 2011.
36. Lake Harney (WBID 2964A) is categorized as impaired for nutrients (TSI). A review
of this impairment is driven by a single year’s exceedance in 2000. In 2000, Central
Florida was experiencing unusually warm conditions in the winter along with drought
conditions all year long. This caused many waters bodies to be denied their natural
circulation. This results in nutrients being unnaturally accumulated in the water
column. Thereby, this single seasonal spike in nutrients is not characteristic of the
over all character of the water body and should not be the basis for impairment.
Recommendation: Remove nutrients from the verified impairments listing [Seminole
County TMDL Analysis 4 PBS&J #100339.02 July 2003].
RESPONSE: As of the November 5, 2003 update of the IWR database, there were
ten TSI annual mean values calculated for years 1991 – 1996, and 1999 – 2002 for
Lake Harney (2964A), ranging from 48.1 to 65.6, with 50% of them above 57. There
were two exceedances of the TSI threshold; in 2000 (65.6) and 2001(64.7). These
figures substantiate that this lake typically has a high TSI level. While it is
understood that periods of drought can serve to concentrate nitrogen and phosphorus,
this should not cause TSI to exceed 60, in lakes with normal levels of these
constituents. Seminole County was unable to provide the Department with sufficient
evidence of the water level in Lake Harney being unusually low in 2000 and 2001,
and a cause for it which could be considered atypical for this lake, therefore this water
segment was retained on the verified list.
37. Lake Jesup Near St. Johns River (WBID 2981A) represents the water body segment
of the St Johns River where the Lake Jesup outfalls. This reach is more
representative of the St Johns River than it is of Lake Jesup, thereby a classification
of the reach as a stream is warranted over the current Lake
classification. This classification will alter the impairment from Nutrients (TSI) to
Nutrients (Chl-a). Recommendation: Switch the impairment from nutrients (TSI) to
nutrients (Chl-a) in the
verified list [Seminole County TMDL Analysis 4 PBS&J #100339.02 July 2003].
RESPONSE: The Department finds that these stations used to assess this segment
are immediately proximal to the lake and are representative of the outfall from the
lake, they are more characteristic of lake conditions than stream conditions. This
water segment has been retained on the verified list.
38. Lake Mobile (WBID 2998B) Review of the FDEP data indicated that the 158
sampling events collected at three LakeWatch sampling stations that are currently