LINKING GEOLOGY AND GEOTECHNICAL ENGINEERING IN KARST: THE QATAR GEOLOGIC MAPPING PROJECT Randall C. Orndorff U.S. Geological Survey, 12201 Sunrise Valley Drive, Reston, Virginia, 20192, USA, [email protected] Michael A. Knight Gannett Fleming, Inc., P.O. Box 67100, Harrisburg, Pennsylvania, 17106, USA, [email protected] Joseph T. Krupansky Gannett Fleming, Inc., 1010 Adams Avenue, Audubon, Pennsylvania, 19403, USA, [email protected] Khaled M. Al-Akhras Ministry of Municipality and Environment, Doha, Qatar, [email protected] Robert G. Stamm U.S. Geological Survey, 12201 Sunrise Valley Drive, Reston, Virginia, 20192, USA, [email protected] Umi Salmah Abdul Samad Ministry of Municipality and Environment, Doha, Qatar, [email protected] Elalim Ahmed Ministry of Municipality and Environment, Doha, Qatar, [email protected] Abstract During a time of expanding population and aging urban Introduction infrastructure, it is critical to have accurate geotechnical Currently, the State of Qatar does not have adequate and geological information to enable adequate design geologic maps at regional and local scales with detailed and make appropriate provisions for construction. This descriptions, proper base maps, GIS, and digital geoda- is especially important in karst terrains that are prone to tabases to adequately support future development. To sinkhole hazards and groundwater quantity and quality better understand the region’s geological and geotech- issues. The State of Qatar in the Middle East, a country nical conditions influencing long term sustainability of underlain by carbonate and evaporite rocks and having future development, the Infrastructure Planning Depart- abundant karst features, has recognized the significance ment (IPD) of the Ministry of Municipality and Environ- of reliable and accurate geological and geotechnical ment (MME) of the State of Qatar has commenced the information and has undertaken a project to develop a Qatar Geologic Mapping Project (QGMP). This project robust geotechnical relational database and prepare geo- will develop high-quality geologic maps, geotechnical logic and thematic digital maps. These products will data, and thematic maps important in meeting this ob- support planning, design, and decision-making process- jective, which includes understanding the State’s karst es related to urban infrastructure development in the rap- environment and characteristics through development of idly growing State and be particularly useful in the early a geologic framework. stages of geotechnical investigations. The U.S. Geolog- ical Survey (USGS), Gannett Fleming, Inc., and the Qa- Qatar, located in the Middle East, is a peninsula sur- tar Ministry of Municipality and Environment (MME) rounded on three sides by the Arabian Gulf (Figure 1). have partnered to design a geologic mapping project that Although it has an arid climate with average annual will merge geological and geotechnical information to precipitation of 7.5cm, its karst topography is well de- develop a framework to model the geology, karst, and veloped with more than 9700 depressions identified in a resources important to support growth in the State. The country of 11,586 km2 (U.S. Central Intelligence Agen- Qatar Geologic Mapping Project (QGMP) has a mission cy, 2017). Large open throat and collapse sinkholes, to integrate sound geoscience data for the State of Qatar and caves are found in rural and urban areas. Although to address societal, environmental and educational needs Qatar is a desert environment, karst that formed during a that include water and mineral resources management wetter climate in the Pleistocene impacts the State today and natural hazards reduction. as developers often encounter cavities in the subsurface 15TH SINKHOLE CONFERENCE NCKRI SYMPOSIUM 7 383 Figure 1. Simplified geologic map of Qatar showing facies types of the Rus Formation and differ- ences in karst development (modified from Eccleston et al., 1981). Schematic sections A-A’ and B-B’ are shown on figure 2. 384 NCKRI SYMPOSIUM 7 15TH SINKHOLE CONFERENCE during construction activities. One of the essential ob- The surface and near subsurface stratigraphy includes as jectives of the QGMP is to analyze the geologic controls much as 600 m of Tertiary carbonate and evaporite rocks on karst development, particularly in terms of lithology, with some interbedded clastic units (Figure 3). Within groundwater, regional structures, and fractures by uti- the limestone and dolostone exposures of the Eocene lizing geologic field mapping, subsurface information, Dammam Formation, the Umm Bab Member is an im- and remote sensing data. Development of high-quality portant unit to structural engineers based on its common geologic and thematic maps coupled with a robust geo- use as a load-bearing stratum, however it also exhibits technical relational database will provide planners, de- a proclivity to air- and water-filled cavities, and thus, velopers and designers the scientific basis to make in- is the focus of considerable geotechnical investigation. formed decisions with respect to the potential physical The base of the Dammam consists of clay or shaley to and financial risks associated with future land use and clayey dolomitic limestone called the Midra Member. In development. southern and central Qatar, this member can be consid- ered an aquitard where it is sufficiently thick and mostly Geologic Setting clay; it is absent in the northern part of Qatar. The un- The low relief of the Qatar peninsula is coincident with derlying Eocene Rus Formation also demonstrates litho- a broad, north-trending fold called the Qatar arch with logic changes between the northern and southern parts of the axis of the arch being nearly equidistant from east the State (Figure 1). Thick sequences of gypsum in the and west coastlines (Figures 1 and 2). Along the western lower part of the Rus Formation are present in the south, margin of the peninsula is the Dukhan anticline, a struc- but not in the north where both depositional conditions ture that defines Qatar’s largest onshore oil field (Figures and secondary dissolution may explain its absence (Ec- 1 and 2). Approximately 80 percent of the land surface cleston et al., 1981). The Paleocene and lower Eocene exposes chalky dolostone and limestone of the Eocene Umm er Radhuma Formation is a complex, poorly un- Dammam Formation (Figure 1). In southern Qatar, the derstood unit that only occurs in the subsurface of Qatar. Dammam is disconformably overlain by 40-80 m of Due to its secondary and tertiary porosity, the Umm er limestone, dolostone, and evaporite rocks of the Mio- Radhuma Formation is an important unit for injection cene Dam Formation. The Dam Formation commonly of treated sewage effluent and waste fluid disposal in oil occurs as erosional remnants that cap the higher eleva- and gas production areas. Also, the unit is under evalu- tions. ation for use in regional aquifer storage and recovery programs. Qatar has been part of a stable platform from the Permian through part of the Tertiary as recognized by the cycles Robust Geologic Map Products of shallow water carbonate rocks with some anhydrite, The wide variety of uses of geologic maps is so broad gypsum and clay deposits (Perotti et al., 2011). that they are one of the most requested scientific products whose return on investment have been calculated at more than 25 times their cost to produce (Bhagwat and Figure 2. Schematic geologic cross sections of Qatar (modified from Seltrust Engineering Ltd., 1980). Lines shown on figure 1. 15TH SINKHOLE CONFERENCE NCKRI SYMPOSIUM 7 385 Figure 3. Stratigraphic column for the Qatar Geologic Mapping Project including age and thick- ness of uppermost Cretaceous and Cenozoic units in Qatar. Sources include Al-Husseini (2008), Al-Saad and Ibrahim (2002), Al-Saad (2005), Dill et al. (2003), Dill et al. (2005), Dill and Henjes- Kunst (2007), Haq and Al-Qahtani (2005), Kok and LeBlanc (2012), LeBlanc (2008), Sharland et al. (2004), Williams and Walkden (2002). Ipe, 2000a; Bhagwat and Ipe, 2000b). The benefits of other development issues will continue to provide useful a geologic map include increased credibility of projects information to address future needs. and time saved in completing projects. The robustness of a geologic map is found in its multiple uses. For The MME has undertaken the development of a example, a geologic map produced to address mineral geotechnical relational database to compile and and energy resources of a region can be used by other preserve existing subsurface information, and to provide investigators to evaluate groundwater resources. a structure for future updates. This investment in Therefore, geologic maps tailored to geotechnical and engineering and science is now actively used to assess 386 NCKRI SYMPOSIUM 7 15TH SINKHOLE CONFERENCE conditions in and around on-going infrastructure and Karst Characterization development projects. In addition, the database serves as With carbonate and evaporite rocks at and near the a substantial information source for producing geologic surface, Qatar exhibits widespread karst features maps and 3D frameworks, structure contour maps, and characterized by sinkholes, shallow closed depressions, isopach maps. The geotechnical attributes contained and caves. Active karst regions are usually associated in the database provide detail for the many engineering with humid climate regimes where precipitation and investigations being completed in Qatar, and they add organics in soils create carbonic acid