Middle St. Johns - Florida Department of Environmental Protection

Water Quality Assessment Report: Middle St. Johns 461
2956B that dissolved oxygen is naturally low, and bioassessment data indicate that
aquatic life use support is being maintained, therefore these have not been listed. As
of the November 5, 2003 update of the IWR database, DO was not impaired in water
segment 2986B and it is not listed.
3. Those impaired water segments on the 1998 303(d) list that do not meet the
sufficiency requirements for the planning list must be placed in category 3c and on
the planning list to remain consistent with [section] 62-303.300(2) of the IWR]. The
assessment status of two water segments needs to be changed from insufficient data
to planning list. (WBID: 2994A, 2962).
RESPONSE: All 1998 303(d) listed parameters for which there were no data or
insufficient data for assessment under the IWR were retained on the planning list, in
the 3c EPA Integrated Report Category, but their proposed status is shown as “no
data” or “insufficient data” (ND/3c or ID/3c). This was done to distinguish them
from 3c listings for which there were sufficient data for assessment (PL/3c). All non-
1998 303(d) listed parameters for which there were no data or insufficient data were
shown as such, and placed into categories 3a or 3b respectively (ND/3a or ID/3b).
4. According to EPA guidance, when sufficient evidence of impairment is presented in a
small data set, the water should be identified as a water quality limited segment. In
several water segments insufficient data are found in the verified period, but
sufficient exceedances occur to place a parameter on the verified list. Although the
data may be insufficient according to the IWR (< 20 samples), the number of
exceedances is higher than that allowed by the IWR. EPA views this as sufficient
evidence of impairment and believes it should be placed on the verified list. (WBID:
2893A, 2973, 2893B, 2929B1, 2956).
RESPONSE: Table 2 in section 62-303.420 of the IWR provides thresholds of
verified impairment, based upon a minimum number of exceedances at given ranges
of total observations. A minimum of 20 observations is required, for verification to
be considered under the IWR. This minimum number is intended to ensure that
conclusions about impairment are not drawn based upon small, unrepresentative data
sets.
5. Silver is not listed as a new parameter of concern from the IWR on the master list.
Please enter silver into that column. (WBID: 2925).
RESPONSE: Silver in water segment 2925 met the data sufficiency requirements
for assessment under the IWR, as of the November 5, 2003 update of the IWR
database, and is considered potentially impaired. It has been added to the planning
list.