Monday,
February 14, 2011
6:00 - 7:30 pm
Pellissippi
State Technical Community College
10915 Hardin
Valley Road, Knoxville
J.L Goins Administration Building, Cafeteria Annex
FEBRUARY
PRESENTATION
Cost
Optimization of DNAPL Site Remediation
Considering Prediction Uncertainty
By
Dr.
Jack Parker
Associate Director for Research
Institute for a Secure and Sustainable Environment
Department of Civil and Environmental Engineering
University of Tennessee
Knoxville, Tennessee
Abstract
A stochastic cost optimization
toolkit was been developed to guide cost-optimal decisions for
DNAPL source and dissolved plume remediation and monitoring to
meet specified objectives considering uncertainty in model
predictions, compliance/performance monitoring data, and assumed
unit costs and discount rates. The approach uses a
semi-analytical model for dissolved transport with multiple
time-dependent DNAPL sources to simulate performance of various
strategies for source zone and dissolved plume remediation. The
model is coupled with (i) an inverse solution to estimate model
parameters and their uncertainty from available data, (ii) a
module to compute net present value cost to meet defined
remediation criteria given unit monitoring, operating and capital
costs, and discount rates, (iii) an error analysis module to
determine uncertainty in performance and cost, and (iv) a module
to determine optimal decision variables to meet specified
objectives. Uncertainty is dealt with by minimizing the expected
value of net present value cost over a set of Monte Carlo
realizations. Applying this approach over many sites should
reduce total costs. For risk-averse decision-makers, more
conservative designs may be determined by applying a
&ldquopenalty cost&rdquo for failure to meet specified
criteria.
Applications to synthetic data sets indicate optimization cost
reductions of 20 to 50% or more compared to designs based on
conventional engineering practices. The program was applied to a
site at Fort Lewis, Washington where multiple DNAPL sources have
resulted in a primary TCE plume in the unconfined Vashon aquifer
and a secondary plume in the semi-confined Sea Level aquifer due
to leakage through a &ldquowindow&rdquo in the aquitard.
When the optimization study commenced, groundwater extraction
systems were operating in both aquifers to control plume
migration, source zone thermal source treatment had been
performed for three identified sources, and pilot tests for
enhanced bioremediation were in progress. Model calibration using
pre-remediation data indicated possible DNAPL beyond the
identified sources, which is consistent with observed
under-performance of thermal source treatment vis à vis
reduction in groundwater concentrations. Design optimization
indicated a low probability of success for thermal treatment due
to uncertainty in DNAPL source delineation. Further design
optimization was performed after recalibrating with post-thermal
treatment data and bioremediation pilot data. Reduced source
delineation uncertainty after recalibration and lower cost
sensitivity of source zone bioremediation to source uncertainty
indicated better success likelihood for bioremediation.
Optimization results provide guidance on injection well locations
and rates, monitoring frequency, and criteria for terminating
injection.
Biographical Sketch
Dr. Jack C. Parker is a Research Professor of Civil and
Environmental Engineering responsible for research on subsurface
fluid flow and reactive chemical transport. He earned a PhD in
soil physics from Virginia Tech in 1980. Prior to joining the
University of Tennessee, Parker served for 6 years as a
Distinguished Research Scientist at Oak Ridge National Laboratory
after 12 years as president of the consulting company
Environmental Systems & Technologies, Inc., which he founded.
He started his career in academia as a Professor of Contaminant
Hydrology at Virginia Tech for 15 years and was a visiting
professor at the Swiss Federal Institute of Technology (ETH).
Dr. Parker has directed many research and consulting projects
involving the modeling of subsurface contaminant transport in
aqueous, gaseous and/or nonaqueous liquid phases at refineries,
terminals, manufacturing plants and other facilities. He is an
ISI Highly Cited Researcher with over 200 technical publications
and has served on numerous expert panels, advisory and review
boards, and delegations for government agencies, professional
groups, private industry and others. He has taught academic and
professional courses and has presented workshops and invited
seminars on modeling of subsurface contaminant transport in 15
countries. Computer models he developed have been employed in
over 30 countries and he has served as an expert witness in
numerous civil actions involving groundwater contamination with
hydrocarbons and organic solvents.
Page updated May 26, 2018 |