THE USE OF COMPUTER WORKSTATIONS IN THE STUDY OF ENVIRONMENTAL GEOLOGY: INTEGRATION OF GEOPHYSICAL AND GEOLOGIC DATA A. Martinez1, T. Carr1, R. Black2, H.R. Feldman1, J.F. Hopkins1, A.J. Feltz1, D.R. Collins1, J. Doveton1 and N.L. Anderson3, 1Kansas Geological Survey, Lawrence, KS 66044; 2Department of Geology, University of Kansas, Lawrence, KS; and 3Department of Geology & Geophysics, University of Missouri-Rolla, Rolla, MO ABSTRACT Geophysical techniques coupled with the modern computer workstation have not been widely used in environmental geology. The Kansas Geological Survey is investigating the application of the computer workstation in a number of projects underway that involve environmental questions and problems associated with salt dissolution. The computer workstation provides an efficient approach to integrate geologic and geophysical interpretations of the shallow subsurface. In addition to modification of available techniques originally developed for computer-aided exploration and development of hydrocarbons, several new applications unique to shallow subsurface characterization are being developed. All applications are capable of addressing environmentally-related questions at various scales from regional aquifer mapping to site specific characterization. Various geophysical and geologic methods have been used to image the shallow subsurface (0-100 m). These methods used in conjunction with a modified computerized interpretation system include high-resolution seismic reflection (2-D and 3-D), vertical seismic profiling (VSP), ground-penetrating radar (GPR), and color image transformation and treatment of the transformed wireline log data as "seismic" traces (pseudo-seismic). The computer workstation approach allows efficient, detailed and integrated studies to be performed at these sites. Examples from throughout Kansas involving a variety of environmental questions and problems associated with salt dissolution are used to illustrate the utility of using the computer workstation in the study of environmental geology. KEY WORDS computer workstations, environmental geology, Permian salts, geophysical data INTRODUCTION digital databases, have radically changed the petroleum industry's approach to expl o- Computer workstation-based interpret a- ration and development. Emphasis within tional software has revolutionized how the petroleum industry is now on powerful geophysical, geologic and engineering data interpretational software that minimizes r e- are interpreted by the petroleum industry. petitive tasks, integrates technologic disc i- Major computer technologies, including plines, maximizes analysis and simulation, near super-computing capabilities on inte r- and increases the number of mistakes (dry active desktop workstations, complex ne t- holes) that are drilled on the desk instead working, high capacity mass storage d e- of in the field. These powerful computer- vices, 3-D visualization software, and large aided interpretational systems have yet to Proceedings of the 10th Annual Conference on Hazardous Waste Research 341 entire aquifers to localized dissolution co l- lapse features. Causation is a complex i n- teraction of natural processes and anthr o- pogenic activities (e.g., irrigation and oil field activities). Examples from Kansas illu s- trate the utility of the computer workstation to perform integrated studies of enviro n- mental problems at scales ranging from small-scale site investigation to regional aquifer studies (Figure 1). Data were co l- lected as part of ongoing studies of ground water aquifers in Kansas by the Kansas Figure 1. Location of the Siefkes Study Site and the Geological Survey. selected pseudo-seismic line from the Dakota Study Area in Kansas. Various geophysical methods were used at several site investigations to image the g e- be widely used by environmental profe s- ology of the shallow subsurface (0-100 m). sionals. These methods include high-resolution seismic reflection (2-D and 3-D), vertical Adequate understanding of heterogeneities seismic profiling (VSP), and ground- of near subsurface geology is an important penetrating radar (GPR). These geophys i- component to improved site investigations, cal methods along with subsurface geologic avoidance of excess spending and ineffe c- data are used in conjunction with a co m- tive remediation. Environmental investig a- puterized interpretation system. The sy s- tions have focused on the point data o b- tem allows efficient, detailed and integrated tained from the drill rig. Point data are often studies to be performed at these sites. inadequate for understanding preferential flow pathways and variations in relative In order to undertake a regional aquifer permeability. Near-surface computer-aided study, a new application of computer geophysical and geologic methods are a n- workstation-based interpretational software other way to image the subsurface. Appl i- was developed. This application treats cation of computer-aided visualization and transformed wireline log data as "seismic" analysis systems in conjunction with the traces for the purposes of processing, i n- use of near-surface geophysical and ge o- terpretation and display. A color image logic methods can provide detailed info r- transformation can combine data from s e- mation of subsurface structures that affect lected wireline logging tools to generate a fluid flow direction and rate of fluid mov e- color coded "crossplot log" for each well. A ment and enhance containment and rem e- well-designed transformation can provide diation procedures. an image of the spatial distribution of su b- surface lithology or fluids. The transformed This paper presents projects underway in image, in either 2-D or 3-D, can be treated Kansas that involve the application of ge o- on the workstation as "seismic" data, ea s- physical and geological methods and the ing the data handling burdens through use computer workstation to a variety of env i- of computerized techniques designed for ronmental questions and problems assoc i- interpretation of seismic data. ated with salt dissolution. Permian salts present in the shallow subsurface of the SMALL- TO MEDIUM-SCALE central and southern parts of Kansas result in a number of environmental problems APPLICATIONS: THE SIEFKES ranging from large-scale contamination of STUDY SITE 342 Proceedings of the 10th Annual Conference on Hazardous Waste Research Figure 2. Detail map of the geophysical study at the Siefkes Study Site. The locations of the ground-penetrating radar (GPR) profile, 2-D seismic reflection profiles, 3-D seismic reflection patch and vertical seismic profiles (VSP) are shown. The Siefkes Study Site is located in central severely limited site characterization and Kansas (Section 27, T21S, R12W, Stafford subsequent ground water mode ling. County). The site is contaminated with a region of salt water intrusion into the fresh In order to improve site characterization, a water aquifer. Salt water contamination of series of geophysical investigations were subsurface fresh water supplies is a serious performed (Figure 2). The geophysical data concern within this area of central Kansas collected include a ground-penetrating r a- [1]. The main source of fresh water in the dar profile imaging the very-near surface region is a near-surface aquifer contained above the water table, 2-D and 3-D near- within unconsolidated Quaternary alluvium. surface seismic reflection data imaging the Salt-rich waters are upwelling from the Permian bedrock surface and deeper rock Permian bedrock into this overlying all u- units, and near-surface vertical seismic vium. At the Siefkes Study Site there is a profile data used to depth-tie the seismic noticeable upwelling of salt-rich waters data with lithological information. around an irrigation well late in the pumping season. Salt water contamination reaches Ground-penetrating radar (GPR) a high enough level that crop damage can A short line (76 m) of GPR data was a c- result. quired in the vicinity of two wells at the Siefkes Study Site. Data was acquired u s- The Siefkes Study Site is part of the Mi n- ing a GSSI SIR System 8 GPR unit with a eral Intrusion Study Area, a region of i n- 500-MHz transducer. The data were tensive study by the Geohydrology Section downloaded from the unit and converted of the Kansas Geological Survey [2, 3]. Site into SEGY format for data integration and characterization and ground water mode l- interpretation within the workstation env i- ing of the Siefkes Study Site were unde r- ronment. The vertical (time) and horizontal taken in order to improve understanding of (distance) scales for GPR data differ co n- ground water flow within the area. Two siderably from seismic reflection data. B e- monitoring wells were placed within the cause the GPR data length is in nanose c- proximity of the irrigation well to monitor onds, rather than milliseconds, it was ne c- subsurface salinity levels and provide essary to time-scale the sample interval of lithological information. Ground water the data by a factor of 1x106 for viewing modeling of the area used information pr o- purposes. The horizontal spacing (CDP) for vided by these ground-water monitoring this data set is approximately 1.2 cm per wells. However, the limited control points CDP point. Proceedings of the 10th Annual Conference on Hazardous Waste Research 343 Figure 3. Detailed image of ground-penetrating radar profile across a feature interpreted as a paleo-stream cha n- nel. The cut bank, as well as several lateral