Hazlett-Kincaid, Inc.
Specialized Geological Modeling Services

An internet-based electronic publication of Hazlett-Kincaid. Copyright © 2000. Hazlett-Kincaid, Inc. All rights reserved. 
Volume 1, Number 6 (October 2000)

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A Modeling Approach to More Effective Site Characterization

Todd R Kincaid & Timothy J. Hazlett

Hazlett-Kincaid, Inc.  204 South 7^th Street, Akron, PA 17501

Introduction

This article contends that effective and expedient site characterizations are hindered by a growing trend in the environmental industry that emphasizes data collection rather than thoughtful geologic and hydrogeologic interpretations.  The apparent trend is to devote most of the resources for site characterization to data acquisition with diminishing regard for its appropriateness to the problem being addressed or its value to the development of cost-effective remediation, protection, or development strategies.  Rather than attacking the utility of any type of hydrogeologic data, however, this article is advocating the synthesis of all available data into computer-based conceptual models of site and regional hydrogeology from the earliest stages of investigation, with the purpose of using the model to guide further data collection and expedite site closures, the development of effective protection strategies, and construction/engineering efforts.  By the term “conceptual model,” we are describing a synthesis of regional and site data into an interpretation of the inter-relationships between physical, chemical, and environmental factors that control the site-scale processes being investigated. 

Creating a site conceptual model is standard practice in good hydrogeology (Sara, 1993) and, in that context, this paper’s premise is not a new idea.  In practice, however, the development of a meaningful conceptual model inclusive of all site data and hydrogeologic interpretations is considerably more difficult now due to larger quantities and more varied data.  Responsibilities for data acquisition and interpretation are often delegated to multiple specialists leaving the synthesis of data and thus the development of the conceptual model to project managers.  Increasingly, time constraints and/or inexperience with varied types of data result in ineffective conceptual models if a formal model is ever indeed constructed.  Consequently, data collection strategies are rarely optimized, the value of collected data is diminished, and site characterizations are more costly and time-consuming than necessary.

The practice of interpretative modeling is an effective method of dealing with the problem.  An interpretative model is one designed to elicit insight into the controlling parameters and important interactions in site-specific settings.  A well designed interpretative model will provide a framework from which cost-effective data collection strategies can be designed, ideas about system dynamics can be formulated, and process oriented modeling can be performed.  The most important characteristic of an interpretive model is that it is constructed specifically to synthesize all available data into an interpretation of present-day site conditions rather than to predict future conditions.

Problems with Standard Modeling Approaches

There are several problems with the standard predictive modeling approach.  First and foremost, as Mary Anderson predicted, the Emperor is now appearing to be largely naked (Anderson, 1983).  That is to say that the applicability and reliability of predictive models is becoming increasingly questionable, largely due to misuse by practitioners poorly versed in either modeling theory or physical hydrogeology.  An analysis of failed or inadequate modeling efforts will most often reveal that the model was based on a poor conceptualization of site conditions and therefore did not contain the necessary framework to handle site complexities.  Even when standard predictive models are properly constructed and adequately embrace thoughtfully articulated site complexities, they are most often:

• only designed to address a specific question,
• difficult and expensive to update with new data, and
• not easily accessible to end-users.

Digital Conceptual Model

Solids and parameter modeling provides a vehicle with which to construct better and more useful site conceptual models.  A solids and parameter model is a computer generated, digital interpretation of site features and conditions that uses statistical and/or deterministic interpolation schemes to synthesize multiple forms of data and hydrogeologic interpretations into a 2- or 3-D visual and query-able database.  As with all predictive models, model construction should be performed by a solids-modeling specialist who is adept with the modeling software and well versed in the modeling principles.  Once a digital site conceptual model is complete, however, it provides a living tool for site characterization and management efforts because (1) it allows end-users access to all of the data and interpretations through graphical interfaces, (2) it can be easily updated as new site data becomes available, and (3) it provides a framework that will support multiple types of investigations, i.e. hydrogeological, geotechnical, risk assessment, etc.  Because the model framework is digital, i.e. a set of 2- and 3-D grids, model components can be ported into process models thereby facilitating the accurate articulation of key site complexities.

EarthVision® by Dynamic Graphics, Inc. is the best modeling software available for the construction of digital site conceptual models.  EarthVision is an integrated software system specifically designed for earth science professionals to synthesize a wide variety of geo-spatial data into comprehensive conceptual models through which the data can be visually and numerically analyzed.  In addition to viewing the model in 3-D on a computer screen, cross-sections, stratigraphic columns, fence diagrams, and structural surface contour maps can be constructed through any desired set of coordinates.  The strength of EarthVision models is their unique ability to describe the geologic framework of a site and then incorporate parameter data such as contaminant concentrations or permeabilities, and engineering data such as borehole and tunnel orientations into the geologic framework model.

View from a digital site conceptual model showing (1) the distribution of permeability in the unsaturated and saturated zones interpolated from a series of field measurements (2) the bedrock surface, (3) the water table surface, (4) the orientation of a proposed infiltration gallery, and (5) topographic features, site facilities, and borehole locations.  The model was generated with EarthVision® by Hazlett-Kincaid, Inc and used to help the client cost-effectively design and locate a site infiltration gallery.

 View from a digital site conceptual model showing (1) the distribution of 5 ppb PCE contamination from an industrial facility in both the saturated and unsaturated zones, (2) the water table surface including a cone of depression associated with a municipal pumping well, and (3) topographic features, site facilities, and borehole locations.  Model was constructed by an environmental consultant with EarthVision® and provided to Dynamic Graphics for promotional purposes.  The model helped the consultant substantially reduce characterization costs by providing for the optimization of well drilling strategies.

Integration with Predictive Models

In the event that a groundwater modeler is presented with a well-characterized site, most times he must create his own conceptual model of the site to suit the purposes of the modeling effort.  In doing so, much of the data acquired in the site characterization process may be lost or reinterpreted.  Using a dual-modeling approach where process-oriented models are integrated with digital conceptual models, as much data as possible is preserved via the seamless integration of the 3D solids/parameter model with the groundwater modeling process.

 The benefits of this approach are many.  For example, seamless integration allows a sophisticated groundwater flow model to be conceptualized and designed in a reduced amount of time.  For a geologically complex site with multiple features, the timesavings alone should justify its use.  Also, the explicit and quantitative articulation of site complexities yields better predictive modeling results.  Finally, the existence of a single interactive conceptual model that synthesizes all available data allows the groundwater modeler to gain invaluable insight into parameter relationships that the modeler might not otherwise have had.  These insights ultimately foster better and more rapid model calibrations.

Large-scale Applications of the Approach

Yucca Mountain Project

The Yucca Mountain Project has adopted a dual-modeling approach to evaluate the viability of Yucca Mountain, Nevada as a high-level radioactive waste repository.  An EarthVision® - Geologic Framework Model of the mountain forms the foundation for what is called the Integrated Site Model (ISM).  The ISM is designed to maintain, retrieve, and model existing site characterization data; and to provide facilities designers with a common framework for understanding site stratigraphy, rock properties, and mineralogy.  The ISM also integrates performance assessment modeling (saturated and unsaturated zone flow and transport models, thermal studies, and Total System Performance Assessment studies) to provide a comprehensive model of how the proposed repository is likely to interact with the natural and engineered environments (YMP, 2000).  Utilization of the ISM (dual-modeling approach) has saved the YMP substantial time and money by effectively communicating subsurface data to the Nuclear Regulatory Commission thereby reducing the number of mandated tunnel and borehole installations and cost-effectively guiding all of the required facilities and environmental testing.

MTA/LIRR East Side Access Project

The Metropolitan Transit Authority (MTA) and the Long Island Rail Road (LIRR) have begun a ten-year, $6 billion-dollar effort to connect the LIRR to New York's Grand Central Terminal.  The connection begins at the Harold Interlocking in Queens where tunneling and cut-and-cover excavations will join LIRR lines to the existing 63rd Street Tunnel via six new tunnel tracks that span approximately 5,500 feet.  From the Manhattan side of the 63rd Street Tunnel, the connection will progress southwest through one new deep tunnel for approximately 5,000 feet to the Grand Central Terminal (MTA, 2000).  The new tunnels will traverse several existing rail yards and underground tunnels, extensive utilities, and multiple hazardous waste sites containing various subsurface contaminants in both the saturated and unsaturated zones. 

The Tunnel Engineering Consultants, Parsons Brinckerhoff Quade & Douglas Inc. and STV Inc. have contracted Hazlett-Kincaid, Inc. to synthesize existing geotechnical and environmental data into a 3-D and query-able digital site conceptual model.  The model will be used to optimize site characterization and excavation strategies, and to supply the framework for later process-oriented modeling thereby minimizing environmental costs.

Vision for the Future

Reincorporating the conceptual modeling process into the initial stages of site characterization will optimize characterization efforts and, in the end, result in more technically sound solutions to environmental, water resources, and subsurface engineering problems.  The best way to achieve that end is to capitalize on state-of-the-art computer modeling software to construct digital and interactive conceptual site models that will allow practitioners to more easily interpret, optimize, visualize, and manage complex geologic and hydrogeologic site data.  Such models will likely become the focal point for all site investigations facilitating communication between engineers, geologists, project management, regulators, and the general public.

Hazlett-Kincaid, Inc. was founded in 1999 to provide specialized geological modeling services.  We utilize EarthVision® to synthesize multiple forms of site data and hydrogeologic interpretations into visually interactive 2- and 3-D conceptual models that help our clients understand site complexities and parameter relationships and thus optimize characterization efforts.  When necessary, we capitalize on the digital framework of the conceptual models to facilitate the development of sophisticated flow and transport models using both finite-difference and finite-element modeling techniques.§

References

Anderson, M.P., 1983, Ground-water modeling – The emperor has no clothes, Ground Water, vol. 21, no. 6, pp. 666-669.

Metropolitan Transportation Authority (MTA), 2000, MTA / Long Island Rail Road East Side Access Phase 1: Early Design and Environmental Impact Statement (EIS), Metropolitan Transportation Authority, New York, New York - http://www.lirr.org/planning/esas/

Sara, M.N., 1993, Standard Handbook for Solid and Hazardous Waste Facility Assessments, Lewis Publishers, Boca Raton, FL, var. paginated at 976 p.