Groundwater Modeling & Litigation Support

SSP&A, as a company, is probably best known for its work in groundwater modeling and litigation support. In this capacity, SSP&A has completed hundreds of projects which involved some component of modeling the subsurface environment. The company provides litigation support in a variety of areas including environmental insurance coverage, natural-resource damage claims, toxic tort claims, remedial-action disputes, environmental liability claims, water-rights adjudication, water and environmental permit disputes, and water-resource regulations.


SSP&A is part of multi-firm team developing remedial alternatives and strategies for RI/FS and post-ROD activities.

SSP&A was retained in 2006 to provide support in the evaluation, design and optimization of a large groundwater remedy at the 200-ZP-1OU of the USDOE Hanford Site. A 5-square-mile plume, which extends to 600 feet below land surface; an estimated 800 to 1,000 tons of carbon tetrachloride were released, together with trichloroethylene, hexavalent chromium and tritium. SSP&A developed a modeling strategy to support an RI/FS and remedial design and developed a step-wise strategy to evaluate the relative benefits of alternate remedies, focusing on combined pump and treat and MNA. The first step involved the development and application of a simple superposition modeling approach written by SSP&A, calibrated to over 60 years of water-level data at dozens of wells that recorded the response of the aquifer to discharged wastewater. Calibration was complemented by use of the program PEST. Advective-dispersive particle-tracking, undertaken with a code developed by SSP&A, illustrated that the calibrated superposition model reproduced contaminant patterns throughout the area of interest. As a result, the superposition model was used to develop and provide a cost-basis for the remedy alternatives described in the FS. Successful completion of the RI/FS led to agreement between the U.S. EPA and the Washington State Department of Ecology, and signing of the first final Record of Decision (ROD) for a groundwater OU at the Hanford Site. 

SSP&A has completed numerous groundwater flow and contaminant transport simulations for all Contaminants of Concern (COCs), in support of the Remdial Design/Remdial Action (RDRA) work plan, 30%, 60% and 90% designs. These simulations included evaluations of the sensitivity of influent concentrations and masses, and attainment of the remedial action objectives, to reasonable variations in pumping rates and contaminant transport properties. The computer codes MODFLOW, MODPATH, and MT3DMS were used for these simulations. To resolve the dry-cell problem in MODFLOW, SSP&A implemented a variably-saturated flow equation within MODFLOW, with an asymmetric matrix solver and Newton-Raphson linearization scheme that has been benchmarked against MODFLOW-SURFACT.

SSP&A also developed an ensemble approach for assessing the performance of the various Hanford pump and treat remedies that combines numerical flow, pathline and transport modeling; multi-event water-level mapping combining kriging and analytic elements; and, analysis of COC trends. Based on this approach Hanford annual reports now incorporate Capture Efficiency maps and Capture Frequency maps to depict the likely extent of hydraulic containment developed by each pump and treat system.

USEPA Region V

SSP&A provides technical support to the EPA Region V Groundwater Evaluation and Optimization System (GEOS) program for evaluating the performance of numerous groundwater and soil remedies at several Superfund sites throughout Region V. SSP&A has provided remedial oversight to more than 20 Superfund sites in Region V.  SSP&A has authored and co-authored numerous reports to support statutory Five Year Reviews, including recommendations on remedy and monitoring program optimization.  In addition, SSP&A develops computational software with graphical user interface (GUI) support to assist USEPA Remedial Project Managers (RPMs) in their statutory Five Year Reviews. Notably, SSP&A has developed KT3D_H20, a user-friendly mapping program for calculating recovery well capture zones using site data.

Martin-Marietta Manufacturing Facility - Denver, Colorado

SSP&A was retained to develop a quantitative framework to be used in making various management decisions concerning the remediation of contaminated groundwater on a 5,000-acre facility located adjacent to the Front Range south of Denver, Colorado. The groundwater system at this site is complex as the result of rugged topography and intricate interactions between the streams and the alluvial ground water. No off-the-shelf groundwater models were appropriate for modeling this site. Therefore, SSP&A developed a three-dimensional finite-element linked groundwater and surface-water transport model to simulate chemical transport in the environment at this site. The modeling results and investigations completed by SSP&A were used as part of technical arguments for insurance litigation.

Hardage/Criner Site - Oklahoma

SSP&A has conducted several investigations at the Hardage/Criner site, a former hazardous waste disposal site facility in central Oklahoma, now in litigation under CERCLA. SSP&A conducted groundwater flow and transport modeling studies as part of the site Feasibility Study. A three-dimensional flow model of the site was constructed, calibrated, and used to assess the groundwater flow and contaminant transport for a number of proposed remedial alternatives, eventually optimizing well locations and pumping rates for the preferred alternative.

Initial investigations at the site involved evaluation and reanalysis of existing data, design of field tests, and analysis of results to determine hydraulic conductivities and piezometric heads in formations of low permeability. Other investigations included analyses to relate fracture spacings and apertures to regional hydraulic parameters; regional flow simulation to estimate hydraulic parameters and to identify potential long-term contaminant migration pathways; evaluation of the potential for dense non-aqueous phase liquid (DNAPL) migration from the waste mounds; analysis of water-quality data to determine contaminant pathways; simulations of flow and solute transport to analyze the effectiveness of various proposed source-control remedies and groundwater clean-up schemes; and, negotiations with technical representatives of the U.S. Environmental Protection Agency on source-control issues.

Work on the project has involved interaction with a technical committee representing numerous potentially responsible parties (PRPs) and with other consulting firms. Additionally, SSP&A provided coordination of the activities of an expert panel retained by the PRPs and technical support for legal counsel in charge of the defense. Expert testimony was presented by Dr. Papadopulos on behalf of the client.

Love Canal - Niagara Falls, New York

Numerical groundwater models were developed to analyze the mechanisms of contaminant migration away from the Love Canal in Niagara Falls, New York, prior to 1980. The flow model developed for the site was calibrated using an inverse technique developed at SSP&A for calibration of three-dimensional transient flow models. Contaminant transport was simulated using particle-tracking methods. The modeling incorporated a large data base and enabled very detailed modeling of the area surrounding the waste source. Extensive sensitivity analyses were conducted for purposes of identifying uncertainties in the understanding of contaminant migration. The analyses conducted by SSP&A were used in support of litigation over cost recovery for implementing remedial actions at Love Canal. Expert testimony was presented by Mr. Larson.

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Intersil Facility - Sunnyvale, California

SSP&A conducted numerical flow modeling and contaminant transport modeling at the former Intersil facility in Sunnyvale, California. The facility is underlain by a shallow plume of multiple contaminants, including PCE, TCE, and 1,2-DCE. The plume, which has multiple sources, is believed to have originated in part through spreading from a pool of DNAPLs located beneath a leaking underground pipeline. SSP&A used the results of the groundwater and transport modeling to evaluate the effectiveness of several alternative configurations for the pump-and-treat extraction system for groundwater remediation. The design of the system was optimized under a number of constraints, including total clean-up time and cost. SSP&A also evaluated the currently-operating extraction system and devised a cost-allocation scheme between Intersil and adjacent facilities.

Kodak Park West

SSP&A developed and calibrated a three-dimensional groundwater flow model for Kodak Park West, a section of the Kodak Park industrial complex, and used it to estimate directions and rates of groundwater flow and to evaluate remedial options. The site is an extensive industrial facility used for film manufacturing and processing and is currently under regulation as a RCRA facility. The model utilizes a finite-difference mesh of five layers and represents flow in a sequence of hydrogeologic units underlying the site. Using the model, SSP&A developed a detailed groundwater budget for Kodak Park West, determined the existing pattern of groundwater flow in each hydrogeologic unit, and tested proposed remedial measures. The model-development process and the results of hydrogeologic calculations made with the model were summarized in a detailed project report.

Savannah River Site

SSP&A developed three-dimensional (multi-layer) numerical flow and transport models of the A- and M-Areas of the Savannah River Site, which is operated by the U.S. Department of Energy. The work performed at the site includes the development of several innovative modeling techniques, including a convolution process which allows the rapid evaluation of the migration of several chemicals with varying retardation and half-life properties. The models were used to assess the future migration of more than eighty chemical compounds assuming certain loading rates to the groundwater environment. The groundwater flow model was calibrated using state-of-the-art parameter estimation techniques based on application of the non-linear optimization techniques that were developed at SSP&A for rapid calibration of three-dimensional models. The results were integrated into an Environmental Impact Statement prepared for the operation of the site.

In addition, SSP&A developed a groundwater flow model of the A- and M-Areas and vicinity to evaluate the effectiveness of an extraction system which is presently in operation. The results of the flow model were used in conjunction with particle tracking programs developed specifically for this project to determine if the present system was effectively removing contaminated groundwater.

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Cyril, Oklahoma

Past oil production operations near the town of Cyril in Caddo County, Oklahoma have resulted in chloride contamination of groundwater from oil-field brine. The chloride plume which covers an area of over 400 acres had affected the former water-supply wells of the town of Cyril. A groundwater flow model of the hydrogeologic system underlying the affected area and its vicinity was developed as part of the litigation support, and was made available upon settlement of the legal case. The groundwater flow model covers an area of about 24 square miles, about 4 miles wide and 6 miles long, encompassing the natural boundaries of the hydrogeologic system. The model was coupled with a particle-tracking routine (PATH3D), to determine the migration pathways of the chloride plume, and with a transport model (MT3D) to evaluate the fate and transport of the plume under natural flow conditions. Transport simulations were also made to evaluate several remediation alternatives such as (1) containment and remediation of the plume by an extraction well system and treatment or deep disposal of the pumped water, and (2) pumping at the high concentration area of the plume for a limited period to reduce peak concentrations and treatment or disposal of the pumped water. Based on the results of these simulations, a remedy consisting of "natural attenuation" with a stream and groundwater monitoring program was recommended and accepted as the appropriate remedy for the site.

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