EAST TENNESSEE GEOLOGICAL SOCIETY
February
2011


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 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.


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