Advisor: Bernhardt Saini-Eidukat, PhD, Professor of Geology, NDSU

Degree Progress: Masters in Environmental Science expected in May 2007

Office: 205 Waldron Hall

Email: damion.knudsen@ndsu.edu

Masters Project

An Investigation into Subsurface Sampling and Characterization Efficiency Using a High Resolution GIS Based Earth System
Budget, spatial, and time constraints limit the number of samples that can be analyzed from a site. An Earth System Simulator (ESS) is being developed to investigate improvements to site characterization and management of three dimensional subsurface analyte distributions. The ESS is used to research the optimization of old and new technologies in site characterization.
Subsurface and groundwater contamination is a major issue affecting people’s health; every year vast sums of money are used in remediation.  The majority of investigators of contaminated sites currently use traditional sampling methods (TSM) such as hollow stem auger and direct push soil borings, hand held photo-ionization detectors (PID), visual confirmation, and laboratory analysis to determine the extent of a subsurface contaminant source zone. These methods are time consuming, costly, and can create large amounts of waste. Improving upon traditional site characterization (TSC) methods using direct sensing instruments (DSI) can greatly reduce the time and budget constraints of site characterization. Investigators may now be able to understand the extent of contamination and create draft or preliminary 3-D conceptual site models (CSM) in real time while still in the field. Shallow subsurface DSI are comparable to measurement while drilling and geophysical wire line bore hole instruments used in the oil and mining industry. Direct sensing, measurement while drilling, and wire line instruments usually collect large amounts of data preceded or followed by TSM used for calibration and data verification. Many times in environmental investigations both DSI and TSM will be operating on a site at the same time with DSI finding hotspots guiding the TSM.
These concepts are in agreement with site characterization experts at the Environmental Protection Agency (EPA) who developed the TRIAD approach. One portion of the triad approach emphasizes that a greater number of higher density direct sensing or real-time measurements followed by a low number of lower density traditional sampling logs for calibration and data verification, will be more economical with regards to the accuracy of a geostatistically modeled subsurface three dimensional analyte distribution. The ESS is being used to test this as a hypothesis.
With DSI between 4,000 and 40,000 semi-quantitative measurements are collected depending on the size of the site and the degree of accuracy of the characterization desired by the site investigator. The term semi-quantitative is used because subsurface DSI only give measurements in percent of a reference standard or in photomultiplier tube (PMT) volts. To further extend the usability of this data a calibration study would need to be done converting the observed measurement values to a chemical concentration usually in parts per million (ppm).