Transport
of Anthropogenic and Natural Contaminants (TANC) Study: Plio-pleistocene deposits
- northern High Plains (Small-area effort cont.)
Objectives:
Determine the contributing areas of water to York, Nebraska public-supply
wells.
Identify the processes controlling the transport and fate of anthropogenic
and natural contamination along flow paths to York public-supply wells.
Quantify the impacts of extensive human modification to the hydrologic
system (withdrawals for irrigation and increased recharge) on the transport
of contaminants to York, Nebraska public-supply wells (see
map).
Approach:
The TANC involves two levels of National effort that includes a small-scale
(SS), and a large-scale (LS) approach to regional analysis. The LS component
allows for the general comparisons of important contaminant-transport mechanisms
across the Nation and helps extrapolate and explain findings from multiple
source-water assessments of ground water. The LS efforts are also intended
to increase knowledge about aquifers, and provide for assessments of the representativeness
and transferability of findings for extrapolation, forecasting, and national
synthesis. The LS study efforts include analysis of existing water-quality
information, synthesis of hydraulic and geochemical information, and refinement
of generalized sub-regional scale models. The LS effort is complete except
for reports that are planned to be published in 2004. The SS effort began
in 2003 and is designed to build on the LS effort. More detailed and processes
oriented studies are planned to identify factors controlling the fate and
transport of natural and anthropogenic contaminants to York public-supply
wells.
Timing: 2002 Accomplishments
Retrospective data analysis and compilation complete in 2002.
Compilation of water-quality data from a variety of sources is complete.
Preliminary analysis of the water-quality data is occurring to determine
priority constituents for investigation and general aquifer geochemical
setting.
Compilation of information on possible sources of anthropogenic contamination
has begun. A preliminary report outline for the study unit report describing
the methods and results of the large-scale study is being prepared.
2003 Accomplishments:
Retrospective data compilation for the following large-scale characterization
tasks is complete: water use and well characteristics; hydrogeology; sources
of anthropogenic contamination; sources of natural contamination; and input
and calibration data for the ground-water flow model for simulating contributing
areas to York public supply wells.
Simulations of the ground-water system in the large-scale study area is
complete.
An existing regional ground-water flow model was used to created a telescoped
model of the large-scale study area.
A first draft of study area chapters on site characterization and ground-water
modeling were submitted for inclusion in national synthesis reports on TANC
activities.
Shallow and deep monitoring wells were installed along the axis of the
defined contributing area for a selected York public-supply well.
Monitoring wells were developed and sampled once for a selected list of
water-quality constituents.
