Wekiva Onsite Nitrogen Contribution Study
Task Updates and Reports
Task 1: Field
Work, $200,000, Ellis & Associates, Inc.
There will be detailed field
sampling within the Wekiva Study Area (WSA) at a few conventional septic
systems. The WSA boundary was defined by incorporating data from various
contributing sources to the Wekiva River System. The question that this field
work portion of the Wekiva project will address is how much nitrogen is
transported to the groundwater by analyzing samples of septic tank effluent, in
the saturated zone underneath a drainfield and in shallow groundwater. There is
an increased level of uncertainty when measuring away from the source, as the
actual source inputs (wastewater, fertilizer, etc.) are variable, but electrical
conductivity as tracer and nitrogen isotope tests are expected to help
differentiate between organic and inorganic nitrogen. This will aid the
researchers in determining the relative inputs from the inorganic forms found in
many commercial fertilizers versus the inorganic forms found in wastewater,
livestock and pet wastes.
There will be a maximum of
three systems assessed. Each site location will be within the boundaries of the
WSA and will be chosen based on a comprehensive list of criteria that RRAC
developed. The criteria include being able to reach the actual water table with
the equipment, choosing a location within each of the three affected counties,
having a public water supply, having a minimum lot size to allow for
identification of the wastewater plume, etc. Once the field work has been
completed, there will be a better understanding of what one septic system in the
WSA contributes to the groundwater and whether this contribution is different
from literature values.
Task 2: Categorization and quantification of nitrogen loading, $25,000, Otis Environmental Consultants, LLC
This task will further
discuss differences between nitrogen loading by different categories of septic
systems (e.g. by applied nitrogen species, infiltrative surface location,
drainage class, depth to saturated zone and soil organic content). The next
part of this step is to then look at the different potential categories of
contribution to come up with an estimate of overall loading.
Task 3: Assessment of the contribution of OWTS relative
to other sources, $25,000, Dr.
Linda J. Young with the Department of Statistics at the University of
In this task, the estimates
from Task 2 will be compared with the amount of loading estimates from other
sources (wastewater treatment facilities, residential fertilizers, commercial
fertilizers, etc.) to determine what percentage of the nitrogen inputs are from
Task 4: Cost-effective solutions, DOH Staff
This task is to recommend a
range of cost effective solutions if contributions of nitrogen from onsite
systems are found to be significant. RRAC has advised the Department staff to
perform preliminary research for this task. Further results from the first
three tasks will influence how this task will be completed. The approach will
be to obtain cost information from each county, and research various strategies
(i.e. recordkeeping, planning, performance, etc.)
Final Project Report
Additional research information can be found at the
Research Review and Advisory Committee (RRAC) web page.
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