Middle St. Johns - Florida Department of Environmental Protection

466 Water Quality Assessment Report: Middle St. Johns
14. Lake Corner (WBID 3033C) and Lake Drawdy (WBID 3033D) are shown as being
impaired for nutrients (TSI). Based upon a review of the data, the impairment
condition for nutrients cannot be substantiated. Recommendation: Remove the
Nutrient Impairment for Lake Corner from the Verified List [Orange County TMDL
Analysis 5 PBS&J 100504.01 July 2003].
RESPONSE: As of the November 5, 2003 update of the IWR database, there were
no data available from these segments which met the requirements of the IWR,
therefore these segments have been removed from the draft verified list for nutrients.
15. Lake Dot (WBID 2997Q) is shown as being impaired for nutrients (TSI). Lake Dot is
a 6-acre pond with a 298-acre drainage basin that outfalls to Lake Concord to the
north via a 108” storm pipe. Recognizing the high potential for lake impairment,
Lake Dot was retrofitted in 1989 when the City of Orlando built an alum injection
system to treat the entire watershed. The construction of this treatment system
resulted in shifting the lake’s conditions from hypereutrophic to mesotrophic. Annual
TSI averages range from 43.97 to 56.68 from 1992-2002 except for the year 2000
which resulted in a 60.19 TSI measurement. Information about this data point, as
provided by the City of Orlando, revealed that during this year the alum injection
system experienced operational problems, which resulted in the system working
sporadically for most of the year. Due to the large drainage basin and small lake
volume, even short periods of untreated stormwater entering the lake had a
dramatic effect on the lake water quality. Since the historic data for this WBID has
been within limits except for the single, non-representative, fall-season sample
measurement, which was the result of a the temporary operational failure of the alum
injection system treating this lake, the data do not support the conclusion that this
water body is impaired for nutrients. Recommendation: Remove the Nutrient
Impairment for Lake Dot from the Verified List [Orange County TMDL Analysis 5
PBS&J 100504.01 July 2003].
RESPONSE: As of the November 5, 2003 update of the IWR database, TSI values in
this segment ranged from 44.1 to 60.8 from 1992 through 2000. Color data were
missing for all of these years, therefore the TSI threshold of 60 was used in
assessment. As noted in Orange County’s comments, one annual TSI mean exceeded
this threshold, in 2000 (TSI = 60.8), when the alum treatment system failed. Annual
mean for 2000 was above threshold, but resulted from violations of the City of
Orlando's Environmental Resource Permit (4-095-0204GMT), therefore this segment
has been removed from the draft verified list.
16. Lake Fairview (WBID 3004B) is recommended for removal from the verified list for
nutrients [Orange County TMDL Analysis 5 PBS&J 100504.01 July 2003].
RESPONSE: As of the November 5, 2003 update of the IWR database, Lake
Fairview is planning listed only for nutrients. It does not meet the verification
threshold of the IWR for nutrients.