In the world of environmental testing, numerous systems can complement traditional due diligence to produce the most ac- curate data for clients. One method that deserves more attention is Geographic Informational Systems (GIS) technology, which offers a relatively cost-effective way to optimize testing quality control by comparing geospatial analysis to sampling data in the lab. While GIS is a widely accepted tool in environmental sciences, oil and gas, municipal agencies, and other industries, the system has yet to be regularly deployed in the environmen- tal testing sector. AGIS is a computer framework that gathers, stores, and analyz- es geographical data relating to positions on the Earth’s surface. These stored data points can help users better understand spatial patterns and relationships that can be useful in specifics areas of interest, such as topological modeling, slope and aspect, hy- drological representation, and multi-criteria decision analysis. For reporting and presentation purposes, the data can be visually organized in layers using maps and other display formats. Real estate developers, engineers, energy companies, state and local governments, the military, and others who must confirm a tract’s suit- ability for specified project requirements often rely on environmental geotechnical testing to identify previous site activity that is not visible to the naked eye, or to document the tract’s geological and develop- ment history. Using even a basic GIS technology like Google Earth, we can provide historical imagery dating back two decades, making it easy to visualize how a site has evolved over time, as well as the impact of natural or man-made occurrences, as seen in these four progressive satellite images showing how development transformed the terrain in Sugar Land, Texas, between 2002 and 2019. An analysis of these images could indicate the need for specific types of testing in certain areas or modifications to a proposed project, providing the client with valuable information at low additional cost. For more complex needs like determining terrain stability, sophisti- cated GIS systems such as Interferometric Synthetic Aperture Radar (InSAR), which measures satellite radar signals to detect land dis- placements, can yield critical information about events that may have compromised a site’s terrain stability. InSar can also mitigate ongoing risk by monitoring for potentially damaging geohazards throughout the life of the project. Use Geographic Informational Systems to Optimize Quality Control in Geotechnical Environmental Testing By Adewumi Andrew
Figure 1: April 8, 2002, Sugar Land, TX,
Figure 2: March 10, 2011, Sugar Land, TX
GIS imagery offers a reliable way for environmental testing labs to validate findings in soils, hydrology, and vegetation made in field sam- plings. Additionally, data results in the lab should be consistent across the spectrum of testing and conform with the historical activity or site characteristics revealed in geospatial imagery. For example, in a Dry Sieve Analysis, if the calculated values of samples obtained in the field indicate 20 percent graveI but the soil description is fine sand, there is likely an error in the procedure. When I detect a miscorrelation between the values in data calculations and the normal range of a sample’s quali- fying characteristics, geospatial imagery may point to information that indicates a mistake in the calculations or data recording. Undetected, that mistake will compromise an analyst’s findings and produce erroneous results that could ultimately jeopardize a project. In my environmental consulting experience, when conducting tests for Free Product Mobility, Hydraulic Conductivity, or Moisture Content, I add an extra layer of quality security by using geospatial imagery to verify a site’s fluvial activity over time. When GIS photos combined with FEMA data show no fluvial factors that might contribute to the moisture content of the soil, in correlation with appropriate soil lithol- ogy, I can speculate that the results of a Moisture Content test will be low, so any test values that are inconsistent will warrant further investigation. Among other applications, I have also used historical imagery obtained through Google Earth Pro to document vegetation on
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november 2020
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