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From
Bureau of Economic Geology, The University of Texas at Austin (www.beg.utexas.edu).
2004 GSA Annual Meeting, Denver, Colorado, November 7–10, 2004 Methods Comparison of Field Parameter Quantification of Unsaturated Flow at an Existing Wastewater Infiltration System; Mines Park, Golden, Colorado Danielle M. Bailey, John McCray, Bridget R. Scanlon, Robert C. Reedy, and Kathryn S. Lowe Abstract: Mountain
watersheds commonly experience water quality and sustainability issues
associated with septic-tank wastewater treatment systems (SWTS). The current
understanding of SWTS is poorly understood and the design of these systems
is generally accomplished through the use of judgment and experience rather
than rigorous quantitative methods. An established wastewater infiltration
experimental site at Mines Park, Golden, CO, is the location of a detailed
vadose-zone characterization
of unsaturated hydraulic conductivity (K(u)). In addition, a comparison
was conducted of various methods utilized for estimating or measuring
K(u). The method comparison addresses both the consistency between the
various methods and the understanding of K(u) variability over the area
typical of a domestic SWTS. Experimental field data was collected from
a two-tier 30-foot long trench excavated at the Mines Park wastewater
infiltration experimental site. The utilized methods of field data collection
include Guelph permeameter measurements (8 locations) and tension-disk
infiltrometer measurements (6 locations). Soil samples, representative
of the two-tier trench, were also collected for in-lab experimentation
at the Bureau of Economic Geology. The in-lab experiments include van
Genuchten-Mualem transformations of capillary-pressure curves determined
from both hanging-column and pressure-plate measurements (14 locations)
and estimated from soil grain-size classifications and bulk density (14
locations). Differences in K(u) from the various methods are illustrated
by comparing K(u) versus water content curves. Statistical analyses are
used to demonstrate the significance of the spatial variability in the
two-tier trench. This research will advance the use of rigorous quantitative
measurements and methods to better understand the impact of wastewater
pollutants on water quality and water sustainability in mountain watersheds. |