Optimum Exposure Area Grid Placement for Human Health Risk Assessment Using ArcGIS Spatial Analyst

The Environmental Restoration Program for the U.S. Department of Energy/National Nuclear Security Administration’s Pantex Plant recently completed a baseline human health risk assessment of exposure to hazardous substance releases from legacy waste management units to help determine the need for further cleanup actions.

A quantitative analysis method using the PointStats Neighborhood Analysis function of the ArcGIS Spatial Analyst extension was used to determine the optimum exposure grid placement for risk evaluation at the Pantex Plant. The objectives included evaluating the impact of various grid configurations on risk results and determining if risk results are sensitive to exposure grid configuration. The optimum grid placement was selected using the most sensitive grid configuration and locating the grid in areas of elevated risk with consideration of worker patterns and facility use.

PointStats Neighborhood Analysis
The ArcGIS PointStats analysis tool was used to identify the shape and orientation of the neighborhood around a hot spot resulting in the highest average risk ratio when the grid was centered on that location. Six different configurations were assessed: a horizontal and vertical rectangle, a square, and each of those shapes turned at a 45-degree angle.

Exposure Area Grid Creation
A regular grid was then replicated around the beginning cell, using the same configuration as the beginning cell, so that the grid encompassed the entire area being assessed.

Courtesy of BWXT Pantex, LLC.