Middle St. Johns - Florida Department of Environmental Protection

484 Water Quality Assessment Report: Middle St. Johns
background conditions. The basis for this opinion is that the watershed is reasonably
undisturbed and has a very high percentage of low-relief with intact wetland cover.
This supposition is subject to further verification and Volusia County is currently
planning additional surface water and groundwater monitoring stations in this basin
aimed at determining background verses anthropogenic influence. The St. John’s
River Water Management District is planning to develop PLRGs for the Deep Creek
basin. We suggest a joint meeting among FDEP, SJRWMD, and Volusia County to
coordinate future monitoring activities, with an objective toward determining if
metals sources and oxygen regimes are anthropogenic or natural prior to verifying a
TMDL for this basin. Given the uncertainties of the sources, with reason for
believing natural background levels may be controlling concentrations, we
recommend shifting metals and dissolved oxygen proposed as “Verified Impaired”
under WBID 2925 to the “Planning List” (Table 7). If legal constraints or court
decisions prevent this, we ask that sufficient time be given to implement a more
definitive monitoring program for determining if sources are anthropogenic or
background before setting and implementing a TMDL [Volusia County Deep Creek
Assessment, BCI Engineers and Scientists, Inc. July 2003].
RESPONSE: Silviculture (tree plantations) and crop and pasture lands are the most
significant land uses in the Deep Creek – Lake Ashby Canal (WBID 2725) watershed,
per the 1995 St. Johns River
Water Management District’s land use coverage (Figure 1). Next most significant
perhaps are surface waters and wetlands. All of the data used in the assessment of
this segment for metals content came from samples taken at station 21FLSJWMDMR
on Deep Creek (red dot on Figure 1). A wastewater residual (biosolids) application
area is located 4.5 miles upstream of this station. The residual application area
appears to have the potential for hydrologic connection to Deep Creek through a
series of roadway ditches, canals and wetlands, particularly during high-water
conditions (Figure 1). What’s more, wastewater residuals are commonly used in
silviculture because they have been found to promote timber growth. Though it’s
unknown at this time if residuals are being used in the silvicultural industry in this
segment, if so, runoff from such applications would presumably be another source of
heavy metals to Deep Creek. It should be noted that station 21FLSJWMDMR is
within feet of a tree plantation.
With the exception of iron, most of the metals for which this segment is verified
impaired are among the ten most common metals of concern in residual applications,
per 40 CFR Part 503 of the Federal Register. While the Department does agree that
the metals of concern in this segment do exist naturally in the environment, the levels
observed are not consistent with natural levels. High concentrations of metals in
groundwater does not necessarily indicate a natural condition, if the potential exists
for surface water contaminants to be introduced to groundwater. This is particularly
important in this segment in light of the likelihood of significant surface
water/groundwater interaction. Before concluding that residual application is not a
significant source of contaminants in this segment, the Department would like to