# Modeling Subsurface Petroleum Hydrocarbon Transport

## Application of Models

Once we understand contaminant transport, we can begin to apply models. This portion of the course contains four major themes:

• introduction to mathematics,
• introduction to model application,
• review and critique of model application, and
• the basis and use of selected models.

### Introduction to Mathematics

The intent of this course is not to emphasize mathematics. There are, however, certain mathematical aspects of models that must be understood in order to appreciate features of model results. This section is as brief as possible.

### Introduction to Model Application

Beyond the mathematics, there are a range of important considerations for model application. These include the dimensionality of the model (1D, 2D, or 3D), treatment of the contaminant source, and other boundary conditions. This is the area where much of the art of modeling resides. We'll give some of the basics, but there's much that only experience can teach.

### Review and Critique of Model Application

Here's where the fun begins. All of the contaminant transport and modeling principles studied to date are needed to review model applications. In this section we present modeling work and look it over to see what we can find. Sometimes there's a lot, as in a case from North Carolina:

Model grid from the North Carolina site--hint: the grid is one of the problems we'll investigate.

### The Basis and Use of Selected Models

Several models will be described in a fair amount of detail, tutorials will be given on how to use the models and application to sites will be shown. The models selected all have a strong tie to EPA. Because of the importance of Risk-Based Corrective Action (RBCA), one module describes the modeling basis of ASTM-RBCA. We'll use the transport and modeling principles we've learned to take a look at this approach.

#### The Hydrocarbon Spill Screening Model (HSSM)

One model that will be covered in detail is the Hydrocarbon Spill Screening Model (HSSM) which was developed by the U.S. EPA. HSSM simulates

• the release of a fuel from the surface,
• the formation and decay of a lens at the water table,
• dissolution of contaminants, and
• transport to receptors.
HSSM version 1.50 produces HTML files as outputs, so the user is provided with a pre-formatted report that contains all inputs and outputs. The report consists of three HTML files containing:

The pre-formatted report is provided for the convenience of the user and to transmit all information about the simulation to the report recipient.

HSSM version 1.20 is at no charge. HSSM version 1.50 is currently in beta testing and will be available at the same location.