Sinkholes and the Engineering and Environmental Impacts of Karst (2008)

On June 13, 2006, several large sinkholes developed within Scott Lake, Polk County, Florida. Due to potentiometric head differences between the lake and the underlying Floridan aquifer, one of the sinkholes drained the entire lake over a seven-day period. Slope failures affected the shoreline and damaged residential properties and other structures. The exposed lakebed revealed two large cover-subsidence sinkholes aligned along a northwest trend, along with multiple circular topographic features consistent with older, in-active (paleo) sinkhole features. Investigation of residential structures along the lakeshore found minor to significant settlement damage related to the slope failures and soil raveling. Standard Penetration Test (SPT) borings showed significant stratigraphic disruptions in the subsurface, suggesting the recent sinkhole activity was associated with reactivation of the pre-existing paleo-sinkhole feature(s). Remediation of damaged properties included compaction grouting to stabilize deeper raveled soils, in combination with foundation underpinning and shallow chemical grouting. The size of the sinkhole features and rapid draining of the lake require substantial cavernous permeability within the Floridan aquifer. Periodic reactivation of paleo-sinkhole features and development of new sinkholes are part of the cycle of formation of lake basins within the mantled karst upland areas in Central Florida. It also provides a mechanism for the transport of large amounts of fine organic sediments into the subsurface.

Recent geologic mapping at a scale of 1:24,000 has enabled a qualitative correlation of the occurrence of springs and sinkholes with bedrock structures and ground-water conditions in the northern Great Valley of Virginia and West Virginia. Sinkholes tend to be concentrated in zones of faulting, local minor folding, and clustered within susceptible bedrock units at the noses and axes of large plunging folds. Alignment of sinkholes mainly occurs along strike of bedding. Enhanced rock solution and conduit formation correlates with carbonate units of greater limestone purity and finer grain size, suggesting some lithologic control on karst formation. In addition, there is an apparent topographic correlation, with sinkholes usually formed in elevated and flat (<5 degrees slope) areas, as well as frequent sinkhole occurrence proximal to entrenched surface streams. Density of sinkhole occurrence tends to increase in areas where water-table fluctuations are large. Large perennial springs occur along faults, and may lie above base level streams indicating upward flow gradients particularly where cross-strike faults and joints intersect bedding planes and strike-parallel faults. Sinkhole formation also frequently occurs in areas proximal to entrenched surface streams, reflecting subsequent vadose-zone modification and excavation of sediment-filled conduits where downward ground-water flow gradients are most steep. Geologic evidence indicates that deep karst development may have taken place by rising fluids under confined (hypogenic) conditions in the distant geologic past in this region.

In 2004, the Illinois State Geological Survey (ISGS) was contacted by two homeowners in southwestern Illinois about subsidence problems with their houses. Although bedrock in southwestern Illinois is predominantly made up of Mississippian-age limestone, and is the site of Illinois' sinkhole plain, the houses were located about 1.6 kilometers (km) from the nearest karst feature. In addition, bedrock beneath the houses was made up of Aux Vases Sandstone (not a karst-forming unit). However, the sandstone in this area is intercalated with and underlain by Ste. Genevieve Limestone, a major karst-forming unit in Illinois and other states, and the sandstone bedrock is bounded on two sides by covered karst limestone. We conducted an examination of the houses using aerial photographs, drill logs, and seismic and resistivity surveys across an apparent lineament between the two houses. The seismic survey revealed a 75 meter (m)-wide zone of disturbance in the bedrock surface that consisted of at least seven crevices bounding six slightly rotated blocks. Vertical disruption of the blocks was only on the order of a meter. Based on our observations of sinkhole formation in the sinkhole plain to the west, that bedrock crevices were at least 15 cm or more wide and were the main reason for the subsidence beneath the houses. The resistivity survey showed that the sediment overlying the trend between the two houses and probably the sediment beneath the two houses is saturated. The wetness of the material beneath the houses is probably the result of storm runoff infiltrating near the houses which would be conducive to piping and soil collapse into the bedrock crevices/conduits along the trend. Further, the resistivity survey showed areas of high resistivity (low conductivity) along the same trend that we interpreted as open cavities in the soil zone and within bedrock. These were probably the features into which sediment was collapsing suggesting that they are fairly substantial openings, possibly characterized as incipient sinkholes in the soil zone and a collapsed cave system in bedrock.

Rocky desertification is widespread over karst mountain areas, particularly underlain by pure carbonate rocks in Southwest China and has had great impacts on local social and economic development. This paper focuses on the mechanism of rocky desertification and its acceleration by human activities. Soil creeping and sliding occur intensively in the weathering crusts of carbonate rocks and at the interfaces between the crusts and the underlying bedrock. The abrupt soil-rock contact at the interfaces is caused by long-term soil creeping and sliding on the bedrock surfaces, which are often very smooth. Both surficial and underground soil losses can cause rocky desertification in this area. Underlain by pure carbonate rocks, underground pipe erosion may be the predominant process of rocky desertification because soil formation rates are usually slower than natural soil erosion rates. In general, rocky desertification is a natural, irreversible geomorphologic process for most karst mountain areas underlain by pure carbonate rocks in Southwest China. Human activities often accelerate rocky desertification. Present soil conservation measures, such as forestation and terracing, have little effect on mitigation of rocky desertification. It is a new challenge to mitigate rocky desertification in karst mountain areas underlain by pure carbonate rocks.

Recent advances in karst research have provided a better understanding of hypogenic speleogenesis—i.e., the formation of caves and other solution-enlarged permeability structures by upwelling waters—and how it integrates with hydrogeologic processes. Southeastern Minnesota has several carbonate units containing features that are being reinterpreted as examples of hypogenic karst processes. Examples of hypogenic features and karst systems can be found in units such as the Dubuque Formation and the Prairie du Chien Group. The latter is also associated with several examples of breccia pipes in the overlying St. Peter Sandstone, including one in an actively developing area of the Minneapolis-St. Paul metropolitan area.

Field hydrogeological investigations in Puding county, Guizhou province, found many underground rivers and caves developed in the synclinal axis, and some developed along a large-scale compressive fault zone, the trend of which agrees with the synclinal axis and compressive fault. Under the action of the tectonic stress field, the distortion of the rock bed gradually increased, and then formed a syncline. Meanwhile, due to local stresses along the synclinal axis, the upper rock bed of the syncline continued to be compressed, and the lower rock bed of the syncline became tensile; radial tensile cracks then formed. At the large-scale compressive thrust fault, the fault zone was extensively compressed and rubblized, causing an obstruction of groundwater flow. Because of the towed fold of the compressive fault, tensile cracks on the hanging block developed. This tensile cracking was beneficial for the development and movement of groundwater resources and karst development. This study furthers the understanding of karst development controlled by structural geology.

In August, 2006, the kitchen and attached garage of single-family home in Nixa Missouri collapsed into a catastrophic sinkhole. To help assess the potential geologic hazard to adjacent residential properties, a geophysical investigation, consisting of surface wave and electrical resistivity data, was performed in combination with a standard geotechnical engineering boring exploration. The borehole control was used, in part, to constrain the interpretation of the geophysical data. Analyses of the surface wave and electrical resistivity data supports the conclusion that the sinkhole developed at the intersection of two near-orthogonal joint systems. The geophysical data suggest that karst-related subsidence at the bedrock level occurred in the study area in the geologic past. No evidence was found that the void associated with the catastrophic sinkhole extended onto adjacent properties.

A team of geologists, geophysicists, and geotechnical engineers completed a subsurface characterization of a property located in a known karst area that was proposed for residential development. The objective of the study was to identify potential areas of instability and define remedies prior to construction. Electrical resistivity surveys were used to aid characterizing subsurface conditions in addition to site reconnaissance, soil and rock coring and air track probes. The electrical resistivity survey results identified trends in the subsurface and several areas of potential structural concern that were subsequently verified by drilling and grouting. The survey results aided conceptualization of subsurface conditions which eventually led to identification of areas recommended for stabilization prior to construction.

Karst regions present some of the most challenging conditions for design of new and remediation of existing structures. Without the appreciation of the highly variable conditions that often typify karstic regions, expediential increases in site development costs can occur both during and after construction. Properly selected and applied geophysical tests can significantly reduce site "unknowns", allowing for better prediction of costs and better selection of appropriate foundations in the planning stage rather than during or after construction. Case studies are given for projects in west-central Florida that have used geophysical tests to provide early information on subsurface conditions allowing optimization of site use and foundation design.

Electrical Resistivity profiles were acquired along three separate parallel traverses on a steeply dipping slope at a construction site near Kansas City, Missouri. The intent was to determine variable depth to bedrock and differentiate the interlayered limestones and shales. This information in conjunction with boring data was necessary for optimum location of a foundation. The determination of depth to bedrock along the electrical resistivity traverses was complicated by several factors. First, eleven different formally-defined lithologic units (alternating limestones and shales) subcrop along the length of the traverses, so the top of rock is not defined by a fairly-consistent resistivity contour-value. Additionally, the limestone units do not thin gradually. Rather, they terminate abruptly as undercut scarps. The differentiation and mapping of the various subsurface lithologic units was also complicated because of variable water saturation along the length of the traverses. As a result, each lithologic unit is characterized by a range in electrical resistivities that vary depending upon the degree of saturation. The interpreted electrical resistivity profiles correlate well with the three borings that were acquired on-site and depth to water table control.

The Marshall Space Flight Center is a 688 hectare (1700-acre) NASA facility located in a karst prone area of northern Alabama. In 2005, a paper was presented at this conference discussing the local and regional karst investigation completed utilizing extensive surface and borehole geophysical techniques. The purpose of the surface and borehole geophysical investigation was to potentially identify significant karst features (conduits, dissolutioned fracture zones, cavities, etc.) and increase the opportunity for placing deep bedrock borings in areas of groundwater flow. This effort included the integration of geophysical measurements with existing well and boring data along with regional geologic information. Geophysical measurements included microgravity, multi-channel analysis of surface waves (MASW), and geophysical logging. The use of multiple geophysical methods provided supporting datasets with overlapping depths of investigation. The integrated geophysical approach to the karst characterization allowed multiple geologic variables to be assessed simultaneously with a greater level of spatial sampling than borings alone. Anomalous conditions identified in the geophysical data that correlated with other supporting data guided the location of deep bedrock borings. This current paper provides follow-up to the karst investigation previously completed presenting the results of an extensive drilling, testing and sampling program. The bedrock wells were used to acquire a suite of downhole measurements that advanced the characterization of the hydrogeologic setting at the site. The suite of measurements included geophysical logging, acoustic and optical televiewer and hydrophysical logging of selected boreholes to quantify flow. At this site, bedrock wells were often dry. The results of the integrated, multi-phase investigation provided an increased effectiveness in drilling the deep bedrock borings in areas with an improved opportunity for encountering groundwater and groundwater flow.

N.S. Nettles & Associates (NSN) has completed extensive geophysical investigations that have guided engineering practices for a resort community in Rendezvous Bay, located in Anguilla, BWI. Located in a modern carbonate depositional environment, the project site is characterized by surficial and sub-surface karst features that were of concern to the geotechnical engineer for structural stability issues and proper design criteria. Diverse technologies were used including Multi-Electrode Resistivity (MER), Continuous Resistivity Profiling (CRP), and Multi-channel Analysis of Surface Waves (MASW). Resistivity techniques allowed for differentiation of geologic units and the identification of karst features and sub-surface anomalies. To determine sub-surface density variability, MASW transects were performed. This multi-method approach provided confidence in the location of anomalies that were later targeted for drilling practices. Borings, including Standard Penetration Tests (SPT), Cone Penetration Tests (CPT), and rock cores were used to investigate anomalies and calibrate the geophysics. Additionally, a stagnant salt pond was mapped using CRP and MER to determine unconsolidated sediment thickness and the competency of underlying limestone. Results provided accurate volume calculations for dredging, the first phase in the transformation of the hypersaline pond to a functional marine habitat. Combined results have provided the geologic framework for engineers to implement a successful construction strategy for the Rendezvous Bay Resort.

The use of borehole logging data is common in engineering geological investigation programs. These data offer a vertical view to the variation of the physical, chemical or lithological properties of the rock series. Concerning karst, the interpretation of borehole data has been, so far, mainly restricted to the detection and characterisation of dissolution voids, which have been usually considered as randomly distributed in space and therefore any prediction of karst occurrences at a more regional scale was supposed as not possible. Our research focussed on the analysis of the 3D geometry of several of the largest cave systems in the World (almost 1500 km of analysed cave conduits). It showed that the development and position of karst conduits under phreatic conditions is remarkably related to a restricted number of so called "inception horizons". An "inception horizon" — a concept introduced by Lowe (1992) — is a part of a rock succession that is particularly susceptible to the effects of the earliest cave forming processes. This concept provides a theoretical framework in which the interpretation of borehole data can be used to characterize and predict karst occurrences up to a regional scale.

This paper explains a conceptual database model used to construct the database management system (DBMS) to investigate karst features. The conceptual model of the karst feature database (KFD) includes three interactive modules: spatial operation, spatial analysis, and hydrogeology modules. All three modules manipulate data from the central database, verify and update attribute values of karst feature data, and put meaningful results back to the database. A working database is developed to include many mapped karst features in Minnesota. The database is currently being expanded to include karst feature data and related geologic and geomorphic data in the Upper Mississippi Valley Karst and Appalachian Karst regions. Standardized metadata and management tools have been developed for this data model that will be beneficial for management and future study of karst features in the U.S. The U.S. Geological Survey, partnering with the National Cave and Karst Research Institute and many karst workers and state agencies, is producing a new national karst map of the United States. The new karst map is being compiled digitally and will be available as GIS data layer at a resolution of 1:1 million. This conceptual model, along with the national karst data network and karst information portal, offers a comprehensive metadata and a potential framework for integration of karst data sets of many resolutions from national to local scales.

Hydrologic data models (HDMs) are GIS-based digital representations of surface drainage networks that are being increasingly applied to address complex water-resources management and protection issues in a variety of topographic and hydrologic settings. However, the application of HDMs to karst terrain is problematic and has not received much prior attention. Using results obtained in a pilot study, this paper discusses the major difficulties and steps involved in creating a HDM capable of incorporating surface and subsurface drainage characteristics of a conduit-dominated karst basin. These include acquiring the necessary geospatial datasets, and the HDM processing techniques used to digitally represent karst features such as internally drained catchments (sinkholes or sinking streams), subsurface conduit flow paths, and temporally-spatially variable flow. A modeling approach is described that uses a combination of manual and automated terrain and HDM processing methods to create an aggregated polygon-and-vector drainage network. The drainage network links internally drained sinkhole catchments, dye-tracer-input sites, and sinking streams (inputs) to karst springs or surface streams (outputs) by way of tracer-inferred flow paths (throughputs). The resulting karst HDM is an effective digital representation of the physical hydrologic framework typical of many well-developed karst basins. Although data input and processing requirements are intensive, and some practical and technical limitations exist, karst HDMs have potential as a valuable new GIS tool, aiding the assessment, management, and protection of karst water resources.

Karst collapse is one of the main geological hazards in Guilin, Guangxi Province, China. Collapse is a geological phenomenon, but the dangerous result is a social and economic phenomenon. With the rapid development of the economy and the increase of human engineering activities in recent years, collapses have happened more frequently and have taken a greater toll on human life and industry. The purpose of this paper is the assessment of potential collapses which can furthest reduce losses, and prevent or reduce collapse hazards. The paper started with the significance of the risk evaluation and zoning of karst collapse. Inducing factors of collapse include geological conditions, development levels of karst, structure of Quaternary soil, depth of overlying soil, dynamic condition of groundwater, faulted structure and well site withdrawal. These influences on collapse were analyzed respectively. And then, using the GIS techniques and discriminatory analysis methods, assessment of the risk of karst collapse hazard in Guilin city was made. Risk zoning was identified and mapped.

Since the inception of the Pennsylvania sinkhole inventory project in 1985, remote sensing techniques have played a large role in helping to define the areal extent of the karstic landscape. These techniques can range in scope and can often provide valuable data for a number of cross-cutting disciplines in statewide and more regional applications. This includes the use of high resolution laser-based imagery such as lidar and multispectral imagery in forest and agricultural studies. It was during a period of drought that an agricultural survey of Lancaster County revealed crop anomalies related to moisture. Color infrared imagery showed more vigorous growth in zones of increased soil moisture availability. This coincided with the surface expression of subsurface structures related to dissolution along bedrock discontinuities. Color infrared imagery is a useful tool in recognizing areas of stressed vegetation. The near infrared (NIR) portion of the spectrum can be used to measure leaf moisture as well as plant health. The near infrared range of 0.8–1.1 μm reflects brightly when a plant has sufficient water and chlorophyll. Thus plants growing in an area with increased soil moisture relative to surrounding areas during a time of drought will have higher reflectance in the NIR and more easily interpreted. An advantage in using the infrared imagery is that it is not dependent on being free of vegetative cover. One can interpret patterns of stressed vs. non-stressed vegetation and not be limited to using leaf-off aerial imagery. In addition, finer resolutions provide a more usable base than a standard 1:24,000 topographic map. Coupled with GIS software, the newer digital photography can be georeferenced and interpreted features can be transferred to the base map without major offsets. This results in a more accurate location of karst surface features during the early phase of a site investigation or in the creation of a karst features map.

Ordovician karst water in the floor of working faces is the major water hazard threatening coal mining operation in North China type coalfields, also a major water hazard source in large scale coal mines in China. The paper presents audio frequency electrical penetration technology adopted at present into China's coal mines. The technology based on the theory of full space DC electrical field, adopted stratified imaging by VL frequency electrical field, realized imaging of karst aquifer distribution in the floor of working face. The paper, also with the technology as the core, presents geophysical technical framework for Ordovician karst water control in China's underground coal mines, and the effect of detection by the technology in dewatering and reinforcement of floor in combination with some engineering examples.

Devil's Sinkhole, located northeast of Rocksprings in Edwards County, Texas, was first visited by European settlers in 1867 and is a registered National Landmark and a Texas Parks and Wildlife Department - State Natural Area. The Sinkhole provides a natural exposure of a near vertical >100 m stratigraphic section of the lower Cretaceous, Edwards Group Limestone. Devil's Sinkhole is 107 m deep which makes it the third deepest cave in Texas. It is one of the few caves in the Edwards Plateau that penetrates to the water table. Two freshwater lakes on the perimeter of Devil's Sinkhole are home to two unique crustacean species — an endemic amphipod and a rare aquatic isopod. The walls of the cave support a Mexican fern species found in few other locations in the United States. The walls of the cave are also the summer home to a population of Mexican free-tailed bats whose nightly departures to forage for insects is a significant tourist attraction. When the bats migrate, the sinkhole becomes the home of three to four thousand swallows. The use of LiDAR (Light Detection and Ranging) instruments to map Devil's Sinkhole was initiated in 2005 with volunteer help of cavers from the Texas Cave Management Association and staff members of the Texas Parks and Wildlife Department and Texas Bureau of Economic Geology. This multifaceted project supports a major public outreach program for the Devil's Sinkhole State Natural Area. Access to the pit is limited because of the 42-meter deep vertical drop. The 3-D, LiDAR model will allow visitors to experience a virtual, bat's-eye view tour inside the Sinkhole. The project also offers quantitative data for geological and biological studies of karst terrains. In 2007, Real Earth Models introduced to the Devil's Sinkhole project, a unique process for draping digital photography onto the LiDAR point cloud surface to produce a 3-D Photo Real Model. This process integrates high-resolution LiDAR data and digital photographs to accurately match the actual geology exposed within the Sinkhole. The resultant 3-D Photo Real Model combines the resolution of digital photos (mm scale) with the positional accuracy of cm-scale LiDAR. This model is a life-like, replica of Devil's Sinkhole that can be rotated and viewed from any perspective. The model also allows a precise, quantitative measurement of physical properties, texture and surface features in natural color.

Underwater exploration at Sistema Zacatón reached human limits when Jim Bowden descended to a depth of 289 meters April 6, 1994. In order to understand this karst system, unmanned robotic exploration is required to document the immense geometry of the underwater caves. The DEPTHX (DEep Phreatic THermal eXplorer) vehicle was developed with support from NASA to approach this problem, with the additional impetus to address robotic exploration in outer space. During the winter and spring of 2007, DEPTHX conducted three-dimensional (3D) underwater mapping missions of 4 cenotes in Sistema Zacatón: El Zacatón, Caracol, Poza Verde, and La Pilita. The detailed maps discovered no lateral tunnels connecting the cenotes, which are only 100–200 meters apart from each other. The deepest cenote, El Zacatón was bottomed out at a depth of 319 meters (339 meters including above water cliff), making it the deepest underwater vertical shaft and second deepest underwater cave in the world. No side tunnels were discovered. However, the 3D data revealed geomorphic features of the cenotes to document how the karst system may have evolved through time. Spatial geochemical data collected contemporaneously during mapping missions indicate that water in the three warmest cenotes is extremely homogeneous, and the cooler cenote displays chemoclines similar to lacustrine type settings. The data collected by DEPTHX are being used with other types of geologic information to investigate the specific nature of hypogenic karstification that formed the cave system.

Soil voids and sinkhole collapses are main geological hazards during highway construction in the karst regions of southwestern China. Controlled by karst development and groundwater fluctuation, soil void usually forms abruptly and then expands progressively until a sinkhole develops. The goal of this research is to develop a cost-effective and efficient method to monitor the soil void formation and propagation, which would potentially prevent and greatly reduce damages caused by future sinkhole collapses. Recent monitoring methods include Ground Penetrating Radar (GPR), inclinometers, Interferometric Synthetic Aperture Radar (InSAR), real-time water pressure monitoring in karst opening, the Brillouin Optical Time Domain Reflectometry (BOTDR), and Time Domain Reflectometry (TDR). The unique features of the BOTDR and TDR techniques such as distributed measurement, long distance range, high resolution, and remote monitoring make them more effective to monitor soil voids and sinkholes along highways in active karst area. Because of the high cost of the Optical Fiber Strain Analyzer, the equipment for BOTDR, TDR was used as a cost-effective method to monitor soil voids and sinkholes. In a pilot study, a 110 m section of subgrade along Guilin-Yangshuo highway was selected to establish a long-term monitoring site, where soil voids formed frequently and more than 43 voids were delineated by GPR. Five lines of coaxial cables were installed on the surface of the subgrade. These lines were parallel to the main axis of the highway with a 3 m separation interval in between. A monitoring station was established on December 21, 2006, and soil deformation measurements were recorded monthly. In addition, water pressure in karst opening was monitored by piezometer and precipitation was recorded by rain gauge at the station. Results of the monitoring measurements show no major subgrade deformation in the past 10 months. One cable fault caused by construction truck was detected by TDR. One minor cable fault caused by subsurface voids or uneven subsidence during construction was detected. Further testing or GPR scan are needed to interpret the minor cable fault.

Human activity on the karst landscape can result in subsidence or collapse, particularly when the thickness of the residual soil layer is reduced due to excavation. When collapse occurs beneath or adjacent to structures or highways, it may result in extensive damage. The stability of the residual soils that overlie solution cavities in limestone is often a concern during the construction, and a simple means to evaluate the stability of these residual soils may be valuable. In this study, the undrained stability of residual soil in karst terrain was investigated by the Finite Element Method (FEM). The results are summarized in a design chart in terms of dimensionless stability numbers and the geometry of a potential soil void above a cavity in the underlying limestone. The use of the stability chart for short-term stability is demonstrated by an example. Such stability numbers can be useful to estimate the stability of a given site based on the expected thickness of the soil overburden and the likely range of anticipated soil void diameters.

Geologic hazards can be identified in a complex urban environment and then combined with historic main break, leak and sinkhole data to develop a utility failure knowledge management system for use in karst areas. Development of a predictive utility failure model based upon 35 years of pavement management, sidewalk reconstruction, utility break, and utility line construction records is presented. Pavement cracking and clusters of service breaks were found to be indicators of slow subsidence in pinnacled solution-prone bedrock areas. High risk deep solution weathering cutter zones were identified using sanitary sewer profiles and verified by ground probing radar. The developed leak-break knowledge management system will be used to identify high risk water, gas, sewer, and stormwater utility areas.

A dataset of 556 collapsed sinkholes covering six 1:24,000 scale geologic quadrangles was analyzed in order to map the relative likelihood of sinkhole formation in Frederick Valley, Maryland, USA. Factors that help predict the density of sinkholes included clustering of sinkholes, geologic structure, rock type, and proximity to: quarries, water bodies, streams, roads, faults, axes of synclines or anticlines, and depth to groundwater. Spatial statistical analyses (K-function, Geographically Weighted Regression (GWR) and Inverse Distance Interpolation) were performed to calculate sinkhole density potential within the study area. K-function analysis was performed to find the clusters over different spatial scales. Using these results sinkhole density was determined for each sinkhole location. Relations of external factors to the calculated interdependent sinkhole density were then examined using Geographically Weighted Regression. The result is a map of sinkhole susceptibility that considers geologic, hydrologic, and anthropogenic factors. The results show that the proximity to the groundwater table, proximity to fold axes, proximity to faults, and proximity to quarries are the factors that significantly influence new sinkhole development, in order of decreasing significance. These results may be a guide for future development activities in this region and others like it.

Over 170 karst collapses were documented in reports by the Missouri Department of Natural Resources between 1968 and 2007. Several collapses occurred in populated areas and several resulted in loss of property. Historically, several sewage lagoons in Missouri have failed due to karst collapse resulting in considerable groundwater contamination and leading to the development of a method for evaluating the potential for karst collapse. Typically, karst collapse potentials are evaluated by scoring a set of risk factors on the basis of casual observation. It is known that the likelihood of a collapse occurring is directly related to several factors including overburden characteristics, depth to groundwater, weather, geologic setting, and karst development. These factors must be identified and quantified or normalized in order to be utilized in an analytical method. Methods of analysis include measuring and normalizing geologic outcrop patterns, identifying water wells that intersect karst features, and developing spatial databases of existing springs, sinkholes, geologic structural features, and other factors. This presentation will discuss the use of spatial and cultural information, associated databases, hazard, risk, and vulnerability analysis.

Estimation of the sinkhole danger in small areas where construction of one new building or reconstruction of one existing building is planned requires site specific information. Unlike qualitative estimates sufficient for large territories, estimates for small sites need to be quantitative forecasts. It is usually necessary to give the engineering-geological recommendations for antikarst protection of a building. This paper presents a description of an approach intended for the solution of these problems. The practical usage of this approach is illustrated with a site-investigation in Moscow.

The State of Florida has developed statutes that provide the most comprehensive set of rules and regulations for the investigation of sinkholes. These rules are more comprehensive than those developed by any other state. However, an unexpected consequence of the statute is confusion in the interpretation of subsurface conditions as they relate to sinkhole claims. An example is provided of the typical abuse that occurs in the use of the Florida Statute and a solution is presented in a method for quantifying sinkhole risk by ranking sites into three categories corresponding to a sinkhole risk score. This method is intended to reduce some of the problems that have caused unprecedented increases in the cost of Florida sinkhole insurance.

Groundwater tracing and cave mapping conducted in the Woodville Karst Plain of north Florida have revealed an extensive dendritic network of saturated conduits, more than 70 km in total length, that convey water to Wakulla Spring from the northeast, north, northwest, and south. In some places, the conduits are known to connect to swallets and in others are known to extend up-gradient into the aquifer matrix. Two sets of tracer tests were performed in 2005 and 2006 to map groundwater flow pathways between the Ames Sink group of swallets, which receive approximately 60% of the City of Tallahassee's storm water runoff, and the City's wastewater spray field, and characterize groundwater velocities along those pathways. The results of these tests revealed that water flows rapidly from both locations to Wakulla Spring. Groundwater velocities through the swimmable portion of the conduit network range from ~1500 to >2000 m/day and velocities through the smaller conduit pathways range from 250 to >800 m/day. We have also compared the shape and timing of the tracer concentration recovery curves to groundwater levels and swallet stage during the tested periods. The results indicate that the aquifer is composed of conduits with varying capacities to convey water and that those capacities establish controls on local hydraulic gradients in the aquifer. More broadly, the results of these tracer studies indicate that tracer recovery curves can reveal significant and potentially quantifiable insights about the hydraulic dynamics of the aquifer when interpreted relative to continuously measured hydraulic data such as heads and flows within the region being tested.

The presence of subterranean conduits within the Woodville Karst Plain is inferred from statistical analysis of several sets of microgravity measurements. In addition to determining the locations of such conduits, their approximate relative depths and sizes are estimated as well. An iterated non-linear least squares method is used to fit observed gravity data to a proposed theoretical model for the conduit-gravity relation. The spatial density of the conduits is examined with respect to their relative cross-sectional areas. A known conduit's presence is verified via the proposed method.

Wakulla Spring is a first-magnitude spring fed by flow within a dendritic network of deep (~ 85 m below the water table) karst tunnels and having many notable hydrologic features, including flashy discharge, constancy of water temperature (less than 1°C) and strong tidal influence (observed in flow, temperature, electrical conductivity and water level). Beginning in 2004 an ambitious program, funded by the Florida Geological Survey and strongly supported by the Woodville Karst Plain Project, was launched to study and quantify flow and transport dynamics within this system, employing both oceanographic flow meters (measuring flow, temperature and electrical conductivity), water-level meters and tracing experiments. This paper describes a select few of the many interesting features of the system that have been revealed, illuminated and quantified by these instruments and experiments. Of particular interest is that the state of the flow system changes episodically; measurements of flow velocity within tunnels show distinct changes in mean speed, direction and variability, lasting typically several months, suggesting that the system may operate in as many as three distinct dynamic modes. Also, measurements of temperature suggest a hidden source of water for Wakulla Springs, not measured by the flow meters currently in place.

Ground water from the karstic Upper Floridan aquifer (UFA) is the sole source of water supply for Tallahassee, Florida, and surrounding areas of Leon County. The City of Tallahassee (City) currently operates 28 water-supply wells. Most of these wells yield an ample supply of potable water; however, low levels of tetrachloroethylene (PCE) have been found in water from several wells. The City removes the PCE from the water by passing it through granular-activated carbon units before distribution. To ensure that water-supply wells presently free of contamination remain PCE-free it is necessary to understand the ground-water flow system in sufficient detail to protect the contributing areas. The City cooperated with the U.S. Geological Survey (USGS) in developing a ground-water flow model of the UFA to delineate contributing areas of water-supply wells and conduct age dating. Ground-water samples collected from four public-supply wells along a north-south transect were analyzed for tritium, helium-3, chlorofluorocarbons (CFCs), and sulfur hexafluoride (SF₆). All three dating methods indicate that the apparent age of ground water generally decreases from northern to southern Leon County. This southward trend of decreasing ages is consistent with increasing amounts of recharge that occur as ground water moves from north to south. Ground-water age data derived by geochemical analyses were used in combination with ground-water flow modeling and particle tracking to determine an effective porosity for the Hawthorn clays and UFA. The Hawthorn clays range from a few meters thick to hundreds of meters thick and extend from land surface (or near land surface) down to the top of the UFA. The effective porosities for the UFA that resulted in best model matches were averaged to determine an average effective porosity of 7 percent, and the effective porosities for the Hawthorn clays that resulted in matches were also averaged to produce an effective porosity of 22 percent. Probabilistic contributing areas were determined for 26 wells using MODFLOW and MODPATH. Five-year time-dependent capture zones assuming effective porosities of 0.1, 1, and 7 percent were delineated for four representative wells. Higher probabilities of capture (greater than 40, 60 and 80 percent) of the 5-year time-dependent capture zones were similar for all effective porosities; however, the lower probabilities of capture showed a large range of variability. The combination of ground-water flow modeling, age dating, and geochemical analyses provided critical information for a better understanding concerning recharge areas to public supply wells in this karstic aquifer system.

The Woodville Karst Plain (WKP) is a complex hydrogeologic system characterized by major recharge areas, large conduits, cavities, caves, sinkholes, and karst windows along with an abundance of springs, some of which are recognized national treasures. A comprehensive surface and groundwater model for this system is currently being developed. Major efforts are being made to map existing features and their interconnection through cave diving, spring mapping and dye tracing. One of the many features being mapped is the extensive underwater cave and conduit system present within the WKP that have a significant impact to any groundwater model. While over 63 km (39 mi) of cave passages have been mapped using divers, it may only represent a small portion of what may exist within the entire WKP. Therefore, a non-invasive surface geophysical technique, microgravity, was used to provide an increased spatial sampling across the WKP. The microgravity method was selected based upon its ability to map low-density zones that may be due to a cave or conduit. A test project was completed over known conduits to evaluate the effectiveness of the method. This test of the microgravity method was quite successful and led to a production survey of over 43 line-km (27 line-mi) of data acquired across a large portion of WKP. Many low-density anomalies similar to those identified in the test phase were detected. A limited drilling and geophysical logging program of four borings were then completed as follow-up to the microgravity survey. Borings were located in areas corresponding to significant microgravity anomalies. While major conduits were not encountered, there were significant indications of secondary porosity, flow and interconnection such as flow carrying suspended particles up the borehole, turbulent flow indicated at selected fractures and the presence of a crawfish-like creature observed in one borehole. The drilling and geophysical logging program confirmed the significance of the microgravity anomalies and the complexity of the WKP system and reaffirmed that an integrated approach is required for karst investigations.

Groundwater flow in the Santa Fe River Basin (SFRB) and the Woodville Karst Plain (WKP) in northern Florida is controlled by large volume karst conduits that transport groundwater and surface water to large discharge points such as Wakulla and Hornsby Springs. Tracer tests have confirmed that these conduits receive surface water input from sinking streams throughout both regions and that water can move through these conduits at velocities greater that 1.5 km/day. Cave surveys have shown that the size and shape of these conduits repeatedly morph between large open passages more than 100 feet in diameter and highly bifurcated networks of small tubes. Groundwater / surface water exchange is reflected by tea-colored spring discharge during wet periods and clear water discharge during drought periods. The combination of these conditions presents a significant challenge to understanding and simulating regional groundwater flow patterns and their susceptibility to human-induced or natural environmental changes. We have had great success in simulating groundwater flow in the SFRB and throughout northern Florida by constructing a finite-element model with conduits represented as embedded discrete element features. This method allows for the assignment of varying conduit area and friction parameters along the flow path. By explicitly defining the conduit network, we have been able to develop flow models that are simultaneously calibrated to head, spring discharge, stream loss, and tracer-defined conduit velocities. In doing this the model has both successfully simulated observed surface water / groundwater interactions and provided insights on the controlling mechanisms. Simulations show that under wet conditions, surface water entering through sinkholes dominates the conduit flow and suppresses the transport of groundwater whereas under dry conditions, surface water input decreases allowing for rapid transport of groundwater. Though it is often dismissed in karst aquifers, these results demonstrate the utility of modeling if an estimated pattern of conduits can be defined through cave surveys, dye tracing, or detailed head mapping. Once a realistic pattern is established, the model itself provides an excellent tool for estimating non-observable conditions such as the effects of internal gradients on conduit-matrix interactions through calibration to heads, spring discharges, and velocities.

The Pennsylvania State University's Office of Physical Plant has instituted an extensive surface water monitoring project with over 25 permanent gages located throughout the University Park, Pennsylvania area in an effort to protect its water resources. This paper will look at data collected from a cluster of six gages located within the Big Hollow Watershed, which is an under-drained carbonate valley. Data collected show exactly where and when surface water is being generated within the gaged area of Big Hollow. Data indicate that the vast majority of the surface runoff that reaches the main stem of the Big Hollow is being generated in a small sub-watershed even though it accounts for less than 6.4% of the land area and 12% of the total imperviousness within the study area due to surface runoff from other areas being infiltrated before reaching the gages. This paper presents the collected data, explains why this phenomenon occurs and the University's efforts to protect the other remaining critical hydrologic land areas within the watershed, and how the University has integrated its wastewater, groundwater, and surface water systems in a karst terrain.

The development opportunities of energy base in China's northern Shaanxi are broad; however, a serious shortage of water resources there is restricting the construction and development of the base. The eastern half of the base, located in Fugu County, covers a karst groundwater system of Tianqiao Spring Basin that has a broad distribution area and good recharge conditions. Unfortunately, the base is at the downstream end of this karst groundwater system, where the water has high hardness and TDS or elevated manganese and nitrogen concentrations. Based on data obtained in a survey of karst water in Fugu in the past two years, a water quality evaluation was conducted in accordance with "Quality Standard for Groundwater" (GB/T14848-93) for cities, industrial and mining water supply. The evaluation concluded that: the quality of most karst water in Fugu exceeds the standard of Grade III, reaching Grade IV and Grade V, and items over standards are respectively total hardness, TDS, sulfate, chloride, manganese, nitrate, nitrite, ammonia, fluoride. As a source of water supply for cities, industrial and mining enterprises, the karst water must be treated with different water treatment technologies before use.

Collection of representative data in karst aquifers often requires monitoring at appropriately-located springs. Following dye tracing and geophysical investigations, one spring was selected as monitoring location for a landfill facility in southern Indiana. Nine rounds of sampling were conducted under different flow conditions. Sequential discrete water samples were collected across the hydrograph curve for each storm-pulse sampling event. The sampling frequency varied according to the flow conditions and the spring responses to the recharge events. Such sampling approaches characterized the natural variations of the water quality at the spring but complicated the development of an effective statistical evaluation plan for the landfill. A suite of combined Shewhart-CUSUM control charts were developed for parameters that are subject to statistical analyses to statistically determine the possible impact of the landfill on the karst system. The statistical power of the control charts was evaluated by Monte Carlo simulations.

A short-term rise in pool levels in Lechuguilla Cave in response to extreme precipitation and flash-flooding events demonstrates the connectivity between the cave and the regional aquifer system. Lechuguilla Cave, currently ranked as the deepest limestone cave in the continental United States, is formed in middle Permian carbonates in the Guadalupe Mountains of southeastern New Mexico. Lake of the White Roses, the lowermost pool in the cave, is thought to intersect the regional water table in the Capitan Reef Aquifer, which provides the water supply for the city of Carlsbad and much of surrounding Eddy County. Direct measurements and datalogger records show that pool levels had steadily declined by over 5 meters since the pool was discovered in 1989, a period during which New Mexico was subject to episodic drought conditions. In 2004 Eddy County experienced unusually high rainfall that included a severe storm in early April. This extreme precipitation event caused flash flooding in the Pecos River and in arroyos in the Guadalupe Mountains, which serve as line sources of recharge to the Reef Aquifer. Within 3 days, pool levels in Lake of the White Roses began to rise, reversing a 13-year declining trend. Water levels in the pool eventually rose 4 cm above pre-flood conditions, then began to decline over the next two weeks. However, beginning in September, pool levels began to rise again, ultimately increasing by almost a meter relative to levels recorded at the beginning of 2004. The higher water levels persisted for several months, consistent with the longer-term precipitation record in Eddy County, which was twice the annual average in 2004. The short and medium-term increases in pool levels in Lechuguilla Cave also correlate to increases in hydraulic head recorded in a monitoring well completed in the Reef Aquifer more than 32 km northeast of the cave, and appear to reflect the triple porosity system — conduit + fracture + matrix — that is typical of karstic aquifers.

Since 1975, site operators have manufactured specialized equipment and assembled utility trucks at the now closed site. Several Environmental Site Assessments (ESAs) were completed from 1990 to 2004. A fuel underground storage tank was removed, shallow wells were installed, and halogenated hydrocarbon-contaminated soil was removed. The hydrogeologic setting has been interpreted from subsurface data from prior investigations and data from corehole drilling and drilling and construction of 24 wells (monitoring wells, hereafter referred to as MW-11 through MW-25 including designations of shallow [S], intermediate [I], and deep [D]). Double cased monitoring wells were constructed to prevent interconnection of the water-bearing zones and downward migration of contaminants. The site is underlain by a Cambrian age formation, the Conasauga Formation, consisting predominantly of interbedded limestone and calcareous shale with an approximate thickness of 1,100 to 1,900 feet. Ground-water movement occurs along solutionally enlarged fractures of limited size and bedding planes. Interpretation of ground-water elevations indicate the direction of ground-water movement is generally toward the southeast, similar to the dip of the formation. Ground-water analyses indicate that many wells have concentrations of halogenated hydrocarbons above Maximum Contaminant Levels. The distribution of the organic constituents in nested wells illustrates the source area in the vicinity of the site operational area in shallow wells and migration and degradation by-products (chemical and biological transformation) in deeper wells, along strike. The contaminated ground water encompasses most of the site and has also migrated to at least 225 feet below land surface.

A limestone quarry was proposed near the Ebenezer Swamp in central Alabama. The University of Montevallo owns a portion of the swamp and uses it as a teaching aid. Fearing that quarry operations would alter the existing balance between surface water and ground water that the swamp and its ecosystem depend upon, the University filed for an injunction to prevent the quarry development. To convince the Court that damage to the Ebenezer Wetlands Ecological Preserve would occur if the quarry was developed, hydrogeologic investigations were completed by, and on behalf of the University. The investigations included review of published information regarding the hydrology and geology of the area, limited site reconnaissance because of the on-going between the University and the developer of the quarry, review of drilling logs from earlier exploration at the site, modeling of predicted drawdown of the water table that would be caused by dewatering of the quarry, and limited drilling and geophysical logging at the site.

The study area is located in the Houzhai Basin, Guizhou Province, in southwest China. The aquifer is a highly heterogeneous triple porosity karst aquifer with diverse hydraulic properties. The Pingshan Sinkhole serves as a perfectly placed well whose water level records the water level in the aquifer. The rainfall and water level time series from 1990 to 1995 have been analyzed and the results indicate that the observed water level variation can be divided into three stages, i.e. low water level stages, water level decreasing-rising stages and high water level stages. A Pingshan Sinkhole water level prediction model has been developed using partial least squares (PLS) regressions and artificial neural network (ANN) methods. The rainfall in the previous 12 hours and the antecedent water level are the main factors influencing the sinkhole water level in the rainy season. The predicted results obtained by the ANN or PLS regression combined with the ANN method are better than the results of PLS regression method alone. The study of the variation and prediction of water level in the Pingshan Sinkhole could benefit the understanding of the hydrological cycle and the hydrogeological conditions in this highly heterogeneous triple porosity karst aquifer.

In the karstic system, numerous karstic features influence hydrologic behavior. Underground stream discharges reflect the fluctuation of ground water level and variability of ground water storage in the watersheds. However, karstic aquifers in southwest China are largely located in the mountain areas and observation data of groundwater level are usually absent. Therefore, numerical groundwater models are inappropriate for simulation of groundwater flow and rainfall-underground outflow responses. In this study, an artificial neural network (ANN) model was developed to simulate underground stream flow discharges. ANN model was applied in the Houzhai subterranean drainage watershed in Guizhou Province of southwest China, a representative of karstic geomorphology in the humid areas of China. Correlation was used to determine the model inputs and time-lags between inputs and outputs. ANN model was trained using the error backpropagation algorithm and validated at three hydrological stations with different karstic features. Study results show that the ANN model performs well for the modeling of karstic aquifers, which are highly non-linear systems. The ANN model offers a promising tool for better understanding of karstic hydrological processes and thus estimation of groundwater resources in the karstic aquifer.

Carbonate bedrocks encompass a vast range of primary porosities and permeabilities, which are further modified by the addition of secondary porosities as a result of fissure, fracture, and conduit development. The wide variety of primary and initial secondary porosities found in carbonates further complicate the already difficult task of modeling speleogenic processes. Understanding carbonate dissolution requires consideration of the aqueous speciation of a host of chemical elements (e.g., H, O, C, Ca, Mg, and S). It also requires simultaneous solution for the complex, typically non-Darcian, flow field over a wide range of spatial and temporal scales as the flow field affects the degree of advection and diffusion of the chemical species to and from the host rock. Lattice-Boltzmann methods are particularly suited to modeling the complex fluid dynamics involved in carbonate dissolution. Lattice-Boltzmann simulations are adept at reproducing complex and changing boundary geometries, as well as turbulent and laminar flows, multiphase-multicomponent flow, and buoyancy-induced convection due to solute and thermal gradients. Here, we present some preliminary numerical models, using lattice-Boltzmann simulations, to reproduce permeability development over a range of length and time scales for two different karst systems: continental Paleozoic systems and modern carbonate platforms.

Coastal karstic aquifers are affected by the tides, primarily due to pressure variations moving inland via tunnels or conduits. This behavior is clearly demonstrated by recent measurements made in the Woodville Karst Plain near Wakulla Springs. The decay rate, λ, and phase speed, V, of these waves are determined by statistical analysis of observations of water levels (made every 5 minutes) over a period of 144 days at two locations 16.6 km apart: one at the coast close to Spring Creek Springs and one at a borehole that connects to a karst tunnel close to Wakulla Spring. The calculated values are λ = 7.87 x 10^–5 m^–1 and V = 2.0 m s^–1 for diurnal tidal modes and λ = 9.25 x 10^–5 m^–1 and V = 4.4 m s^–1 for semi-diurnal tidal modes. These decay rates are equivalent to e-folding scales of 12.7 and 10.8 km, respectively. The decay rate is smaller and the phase speed is larger than predicted for a Darcian aquifer by factors of roughly 100, illustrating the profound influence that a conduit can have on aquifer dynamics.

An investigation of a local karst system in Howell County, Missouri was conducted using fluorescent dye tracing techniques. This investigation was initiated after several local residents complained of "contaminated" water supply wells. It was determined that suspected contaminants may originate from a local dairy that periodically discharged large quantities of animal waste effluent into a losing stream. Howell County is located in the southern Missouri Ozarks, an area typified by extensive karst development. Relatively deep solution weathering of the bedrock results in rapid migration of surface water to the subsurface. Development of this system has resulted in the occurrence of springs, sinkholes, losing streams and other karst features of interest to this study. Prior to this investigation, hydrogeologic data in this area consisted of an analysis of the hydrologic characteristics of the basin and the major springs within. However data available for the area of the basin of interested was limited to a single dye trace and regional potentiometric surface mapping. Field reconnaissance revealed important information on geology, hydrogeology and geomorphology. Several springs with flow greater than 250 l/sec were identified as possible groundwater discharge points receiving recharge from the area of the dairy lagoon. The field reconnaissance coupled with the existing data allowed the formulation of a reasonable hydrogeologic model. The resulting information from this study established the existence of hydrologic connections from the dye injection site to two regional springs.

Southeastern Minnesota's karst lands support numerous trout streams. These trout streams are formed by springs discharging from Paleozoic bedrock. Dye tracing has been the tool of choice for mapping the springsheds (karst groundwater basins) that feed these springs. Previous work was focused on the Galena limestone karst. In order to accelerate springshed mapping, a two-year study was funded by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR). Across southeastern Minnesota, numerous springs discharge from the Cambrian St. Lawrence formation. The St. Lawrence is considered to be a confining unit under the Minnesota well code. A dye trace was initiated when a stream sink was discovered in the upper St. Lawrence Formation. The sampling points included springs, stream crossings, and a municipal well that may be at risk for surface contamination. Dye was recovered at one spring in less than two weeks and at two other springs in less than three weeks. This translates into travel times of 200–300 meters/day. The springs all discharge from the lower St. Lawrence Formation. The St. Lawrence contains beds of dolostone; the dye trace demonstrates that there is a karst conduit flow component in this formation. This is evidence that these springs are significantly more susceptible to degradation than previously thought.

Southeastern Minnesota's karst lands support numerous trout streams created by coldwater springs emanating from Paleozoic bedrock. While trout streams have been traditionally managed as surface water resources they are fundamentally supported by clear, relatively constant temperature groundwater. In karst areas this groundwater resource is as vulnerable as surface waters to human activities. Designing Best Management Practices (BMPs) to protect groundwater fed springs should improve the overall protection of Minnesota's trout streams. Dye tracing has been the tool of choice for mapping the recharge area or groundwater basin that feed a particular spring. These karst groundwater basins have been termed "springsheds". In order to accelerate springshed mapping, a two-year study was funded by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR). To improve the effectiveness of dye tracing we are applying a variety of new tools to increase our knowledge of the underlying karst systems Techniques being investigated include temperature and discharge monitoring, detailed structural mapping of the aquifers, unit hydrographs, chemical and isotopic studies. These new methods to define the size and geometry of springsheds can be tested against basins previously defined by dye tracing. In previously untraced basins these predictive tools can be used to design more efficient tracing programs. The following paper demonstrates the application of structural mapping to dye tracing.

A professionally designed, installed and inspected conforming waste water treatment system and a conforming water supply well were installed at a new restaurant in rural Door County, Wisconsin. In the two weeks following the opening of the restaurant, over 250 people became ill with viral gastroenteritis. Testing of the new, conforming well at the restaurant found contamination with a viral agent causing the illnesses. Stool samples of ill individuals had positive test results for norovirus, campylobacter and salmonella. Following the installation of a multi-stage water treatment system on the well, the restaurant re-opened and no further illness has occurred. The raw water from the well continues to show evidence of human waste contamination. A dual dye trace was conducted to identify possible rapid connections between the waste water treatment system and the water supply well. Dye injected in the dosing chamber that feeds the system drain field began to appear in the water supply well after fifteen days. The appearance of this dye is a measure of the flow through time from the dosing chamber to the water supply well. A second dye injected into a toilet in one of the restaurant's restrooms began to appear in the water supply well after six days. The rapid appearance of this latter dye indicates a leak in the plumbing system before the effluent reaches the dosing chamber. Both dyes reached off site private wells about one-half mile down gradient in about three months and document a natural gradient groundwater flow velocity of about three kilometers per year. These results in a new conforming rural waste water disposal system call into question the efficacy of the current construction standards, guidelines and siting practices for large on-site waste water disposal treatment systems in karst.

The Southwest Florida Water Management District, Florida, USA (SWFWMD) has recorded several instances of karst-related features (e.g. solution pipe formation) forming within constructed, surface, water management systems. Previous studies, including DRASTIC, Florida Aquifer Vulnerability Assessment (FAVA), and parameter weighting/scoring methodologies, provided delineations of areas at risk for surface water contamination of ground water aquifers. Each of those methods identified terrains where discharges of untreated surface waters may introduce contaminants into groundwater aquifers. None of the previous studies recommended a specific area for enhanced, regulatory protection. This study examined the previous studies' methodologies, tested the efficacy of methods to predict known sinkhole and pond failure sites, and recommended a Sensitive Karst Area (SKA) for regulatory purposes. This study recommended several interim actions that are within current regulatory authority, including questions for reviewers to ask and strategies to propose as permit conditions. This study proposed enhanced strategies for possible rule making.

Federal and State regulations are not specifically written to account for the special aquifer conditions present in a karst terrane. As such, specifications to investigate aquifer characteristics, establish ground water monitoring programs, and/or conduct remedial actions are at risk of being ineffective. Site specific and aquifer specific measures must be taken by regulatory agencies to properly perform ground water monitoring and protection in karst areas, and still maintain the regulatory framework.

Due to access, only one deep boring could be obtained for the geotechnical investigation for a raw water intake structure in Cadiz, Kentucky to be set into a limestone bluff and founded in limestone bedrock 21 feet below river stage. The rock core indicated high recovery and rock quality designation (RQD) values. A small cave was noted in the bluff, suggesting that karst could be encountered during excavation. Unfilled and clay-filled caves were encountered during excavation, along with vertical and low-angle fault zones and fault-controlled karst. A lower boundary of cave development was observed above the planned foundation bearing level. Once below river stage, water inflow entered the excavation from the sidewall and floor along fault- or karst-controlled discontinuities. Shallow, karst-enhanced faults dipped into the cuts made for the permanent terrace and access road. Stability analyses suggested that block failure onto the terrace could occur in the design earthquake. The extent and magnitude of karst development were not revealed by the single deep boring. This project underscored the need to obtain adequate geotechnical information, including sufficient borings, during the project design phase. We emphasize the need for understanding the geologic history and structural geology of a project site, including the use of topographic and geologic maps and the capability of recognizing and mapping structural features such as faults, joints, slickensides, and shattered rock zones. Review of rock core alone may not reveal local evidence of faulting, if subsequent karst development removes the evidence of movement.

This paper presents a new method to remedy a common sinkhole problem in karst terrains by using geosynthetics over drilled shafts to support an embankment. Numerical analysis using FLAC^2D software was conducted to verify the effectiveness of this method. In the numerical analysis, foundation soil, rock, and a drilled shaft wall were assumed to be elastic while embankment fill was assumed to be linearly elastic-perfectly plastic with a Mohr-Coulomb failure criterion. A geosynthetic layer above the drilled shaft wall was modeled using cable elements. The construction of the embankment was simulated in three stages. The numerical results include the settlement at the base of the embankment, the tension in the geosynthetic layer, and the axial force in the drilled shaft. A parametric study was conducted to investigate the effects of the void size and the tensile stiffness of geosynthetic. The numerical analysis demonstrated that this proposed method could be effective in maintaining the stability of the embankment over the sinkhole. This paper presents a preliminary study using geosynthetics and drilled shafts to mitigate the embankment over a small sinkhole. Further study is under way to investigate embankments over large sinkholes with multiple drilled shaft walls.

Geophysical surveying using the seismic reflection method was used to help determine zones of karstic bedrock and develop geotechnical parameters for design and construction of an elevated 400,000-gallon water storage tower at a site northwest of the City of Jackson, Missouri. The area was known to have karst topography. This history was used to develop a site evaluation program. Results of geophysical surveying were used to plan and prioritize subsurface exploration, including drilling and sampling. By combining geophysical and traditional drilling, the exploration was more cost efficient and effective than either individual element. Data from the seismic reflection survey, subsurface exploration and previous well drilling correlated well, indicating the southern portion of the survey area was generally more impacted by karst including the presence of irregular and pinnacled weathered rock and therefore avoided during site development planning. Highly variable bedrock depth and quality could adversely affect foundation design and construction. Therefore, QA/QC observation and testing were required to further assess rock quality at foundation locations. Overall, the exploration program helped identify comparatively higher quality bedrock, simplify design, and reduce overall construction cost and risk.

Construction and site development for new facilities in the Corydon, Indiana area, typically involve treatment of one or more sinkholes, given the presence of the St. Louis-Ste. Genevieve limestone throughout this portion of southern Indiana. The site selected for the new Harrison County hospital included ten closed-contour depressions at the start of the project; site development activities disclosed five additional features. Foundation construction involved drilled piers bearing on competent limestone, with significant blasting required to excavate a walkout basement. Foundation construction encountered a highly variable upper rock surface, as well as a cave system with a flowing stream. Concrete placement in a number of the piers required creative field techniques, such as the use of dry cement to plug voids, to prevent flow of concrete into the cave system. Site development was accomplished using four of the features as drainage facilities for surface water runoff. One feature in particular was designed to receive runoff from 11 acres and was in close proximity to the stream in the cave system. The excavation for this drainage feature extended almost 40 feet vertically and the throat collapsed partially during construction. Special measures, including installation of oil-water separators, were employed to prevent contaminants, in the form of petroleum hydrocarbon residue from the parking lots, from reaching the sub-surface system.

Forensic geotechnical engineering deals with the geotechnical investigation of soil-interaction related failures of geotechnical origin not only from a technical viewpoint but also the possibility of legal proceedings. Typically, forensic investigations differ from conventional geotechnical investigation in that they are retrospective. They seek to explain "What happened?" and "Why did it happen?", rather than to predict future performance. Of course, these are often followed by, "How can it be fixed?", and all to often, "Whose fault is it?" and "Who is going to pay?". Two forensic case studies are presented where updated and current methods were used to detect, mitigate, and repair Karst sinkhole conditions prior to and after construction of a structure. Consulting services were provided to assist the retained counsel in resolution of one of the cases. The project owner was able to recover a major portion of the loss and litigation cost from the insurer.

Subsurface sand slurry injection was initiated as an alternative to concrete grout injection, which is widely used across Florida to stabilize subsurface sinkhole activity or otherwise unstable subsurface conditions. Instead of pumping concrete grout under pressure, a sand slurry mixture is utilized. The sand slurry injection method provides for subsurface stabilization in the same way as concrete grout injection, but it also provides other benefits that are not possible to achieve with the concrete grout method. The injected sand slurry provides for long term stable subsurface conditions as well as anticipated effective permeability through the repaired subsurface. The sand slurry injection also avoids "grouting in" of buried utilities or other underground structures. The injection of natural sand to repair subsurface unstable conditions does not require introduction of hardening and effectively impervious material (cement), the application is simpler than concrete grout, and the cost is significantly less than the concrete grout alternative. The method of sand slurry injection is not intended as a blanket alternative to concrete grout injection, however, it can be a more advantageous method for special projects. The sand slurry method has been proven to be effective for filling large sinkhole cavities, raveled subsurface conditions below storm water ponds, sinkhole related collapses of roads, stabilization of storm water structures, and sinkhole activity created by pumping wells.

Sinkholes and Karst windows are very common in southwestern Kentucky. Several sinkhole collapses over the past 20 years has resulted in the acknowledgement of the importance of an adequate subsurface characterization program for new construction projects. A large formally agricultural site was being considered for development into a large Intermodal Industrial Park. The several hundred acre site is north of Bowling Green, Kentucky and south of the Mammoth Cave National Park. The property had several small sinkholes scattered throughout the property. To quantify the risk of future dropouts, several geotechnical engineering evaluations were conducted. Following the conceptual planning, a microgravity subsurface study was conducted to; determine areas of incipient voids in the overburden soils, depth to bedrock and to located voids, caves or crevices in the bedrock. Microgravity surveys use a microgravity meter to measure the gravitational field of the subsurface. Variations in the gravitational field indicate anomalies within the soil overburden. Once these anomalies were located, they were explored using traditional geotechnical drilling and test pit excavations. Results from the microgravity survey and the accompanying geotechnical engineering exploration quantified the risk such that the local economic development agency invested in the construction of the project attracting several large industrial tenants and high paying jobs.

Sinkholes and roadway depressions are one of the common and reoccurring problems along interstate highways, state roads, county roads, and local roads within the State of Florida. Such incidents cause significant problems that may include lane and/or road closure, interruption to the public normal way of life, construction delays and interruption to construction schedule. This paper presents a case history of identification and repair of a roadway depression in Columbia County, Florida. The noted distress was attributed to sinkhole activity based on the detection of a cavity in SPT borings, zones of low blow counts, disturbed soils in GPR pseudo sections, and a highly variable limestone bedrock surface. Pressure grouting using high slump neat cement was used to remediate the sinkhole. A total of 147.5 cubic yards of grout was required for remediation. The majority of the grout (approximately 70%) was pumped into the detected void. The remainder of the grout was pumped into zones approximately 15 feet above the top of the bedrock surface.

Structural underpinning with hydraulically-driven steel pipe piles (underpins) is often employed for foundation remediation in order to address displacement related distress. This paper discusses thee (3) different underpinning approaches based on the subsurface mechanism(s) encountered at the subject site. First, a restorative underpinning approach is utilized to address the portion of the structure which has been structurally compromised by displacement. This approach is used to lift and re-level a structure that has experienced displacement related distress. This approach can be applied to a portion of or an entire structure. Second, a stabilitive underpinning approach is utilized to maintain a structure in its current state while preventing additional movement from occurring. This approach is not used to lift and relevel mainly to prevent collateral distress and damage. Lastly, a preventative underpinning approach is used to eliminate the potential for future movement to a structure from subsurface mechanism(s) by isolating the structure from the problematic soils which cannot be feasibly remediated with standard soil remediation techniques. This approach may take one of two forms. A structural preventative approach addresses only those load-bearing components of the structure while a comprehensive preventative approach addresses all portions of the structure susceptible to displacement. It is important to note that while underpinning is intended to address the structure and remediate displacement related distress, it is not intended to address or remediate the subsurface conditions responsible for the displacement of the structure.

A comprehensive geotechnical investigation was carried out at a residential area under development, 20 Kilometers North of Kuwait City, by M/S Public Authority for Housing Welfare (PAHW). The investigations resulted in significant information regarding the stratigraphy and engineering and geological properties of the sub-soil. Those investigations indicated that the top layer consisted of very loose to loose silty sand with groundwater occurring at about 1.3 meters below ground surface. During excavation, a network of small interconnected cavities were found to exist at depths ranging from 0.5 to 8 meters. Those cavities were found to extend horizontally starting with depths coinciding with that of the groundwater levels at the area. This could be an indication of the existence of collapsible soils that compact and collapse upon wetting. Groundwater movement towards the sea could have caused dissolution of cemented sediments and washed out fine soils as traces of organic and salt sediments were found to exist on the cavities walls. The cavities could have also been formed due to liquefaction as several earthquakes with magnitudes ranging from 3 to 4.5 on the Richter scale struck the area in the past. It was observed that cavities did not exist in the dense layers (2–8 meters below ground surface). To reduce the risk of cavity development in the area, several soil improvement techniques were suggested. Soil placement improvement technique was chosen by PAHW and used for the whole depth of cavities occurrence.

As a result of dewatering in the Venterspost Groundwater Compartment, Far West Rand, South Africa, numerous catastrophic sinkholes occurred in the surrounding area of Venterspost Town. Due to this large occurrence of events, this particular area, where the access road to Venterspost crosses the Wonderfontein Stream, became known as the `sinkhole farm". Despite this dramatic history barely 30 years ago, the demand for developable land has required that development in Venterspost Town, with its excellent but abandoned infrastructure, be reconsidered. In the late 1990's the South African Council for Geoscience (CGS) classified the Town into zones of development suitability based on their risk according to the affects of dewatering. While stands considered safe for development may be reused and the poorer areas left abandoned, a dilemma exists for the road joining the Town and Westonaria however. The mining groups which were the responsible parties for the dewatering of the area are concerned that continued use, and even increased use due to the arrival of new residents, of the access road could place the public at risk. Westonaria on the other hand, as the local municipal authority, desperately need this road to be able to service Venterspost Town which is part of its municipal area.

The 66 km long Guilin - Yangshuo highway is located in northern Guangxi, China. The entire highway was built through an active karst area characterized by tower karst, karst valleys, and watershed divides. The highway construction has induced many sinkholes since the construction started in 2004. The primary goals of this research are to detect locations of subsurface voids and potential sinkholes and to treat these voids to prevent future collapses. A 200m section representing typical karst setting of the highway was chosen for a preliminary survey. Ground Penetrating Radar (GPR), multi-electrode electric resistivity, and shallow seismic reflection were used for the preliminary survey. Comparison of the three geophysical methods indicates that GPR can detect subsurface voids in a more effective and timely manner. Therefore, GPR was applied to a 12 km section highway to located subsurface voids in a highly active karst area. 337 subsurface voids, 1–6 m in diameter, 1–5.5 m deep, and density up to 48 per 100 m, were detected using GPR. Further assessment of the study area indicates that water table fluctuations around bedrock and soil interface cause the formation of subsurface voids. Excavation for the foundation of the highway induced more surface water into the karst aquifer and water pumping from the bridge foundation significantly lowered the water table of the karst aquifer. Highway construction changed the natural drainage pattern and caused more hydrodynamic changes of the karst aquifer, which in turn formed more subsurface voids or enlarged existing voids. Finally excavation, graded-filter, and geofabric lining techniques were suggested to treat clustered subsurface voids and grouting was suggested to treat isolated voids. This treatment plan has been accepted by the highway construction company.

Water began to flow into a quarry through a karst conduit connecting the quarry to a large nearby creek. Flow into the quarry was about 4,000 gallons per minute (gpm) [15,150 liters per minute]. The site, a dolomite quarry in north-central Alabama, is in an area underlain by structurally deformed Cambrian carbonates with documented karst development. Field mapping identified a dominant fracture orientation that controlled ground-water flow and permitted development and implementation of a grouting program to inhibit water flow in the conduits. The quarry and inflow point are about 400 feet (122 meters) southwest of a large creek. Bedrock exposed in the bed of the creek is fractured and cavernous openings were observed, as was a sinkhole on the left bank (the southwest bank) of the creek. The quarry operators had attempted to repair the sinkhole with gravel and other materials prior to the investigation. However, water continued to flow from the creek into the sinkhole. The flow in the creek was about 5,000 gpm (18,900 liters per minute) less (about 40 percent) downstream of the sinkhole than at the upstream measuring location. Dye was introduced into the stream near the sinkhole and appeared in the inflow of the quarry within about 4 minutes. Based on the dye study, a grouting program was designed. Ten boreholes were drilled to depths as great as 120 feet (37 meters) below land surface in a line nearly perpendicular to the line between the sinkhole and the inflow. During drilling of some of these boreholes, water-filled cavities were penetrated and the water flowing into the quarry became muddy. A secondary line of two boreholes was drilled and grouted about 10 feet (3 meters) toward the creek from the first line. A third line of three boreholes was drilled along the highwall near the inflow point. All boreholes, and the sinkhole on the left bank of the creek, were grouted using high viscosity grout. As a result of the grouting program, inflow into the quarry was reduced to less than 1,000 gpm (3,790 liters per minute).

Dongpang Mine, located in Xingtai, China, was flooded in 2003 by a water inrush in which pressurized groundwater in the underlying limestone suddenly flowed into the mine through a karstic collapse column. In order to restore the flooded mine and prevent future water inrushes, a grout-plug was constructed within the collapse feature. The grouting was conducted on the surface by drilling boreholes and pumping grout into the collapse column, while monitoring of the effectiveness of the plug was carried out underground by artesian flow tests through directionally drilled wells. The completed grout-plug is 73m high. Construction of such a large in-situ plug in an underground collapse feature overcame several engineering challenges. A key component to the success of this project was that all the grout holes including primary, secondary and tertiary ones were directed precisely to the designed locations. In addition, the technique, quality control, grouting stages, and completion criteria of each stage were tailored to the site-specific conditions. The effectiveness of completed plug was evaluated by core samples collected at boreholes and underground water-injection and water drainage tests.

Pressure grouting is often called for in treating Karst for one of two possible objectives; prevent or arrest surface settlement as a result of sinkholes, or stop the movement of water through Karstic voids. For arresting loss of soil, the throats of karst features must be sealed which might be through injection of low mobility, compaction, or permeation grout. Rarely is it reasonable to fill large Karstic spaces although many contractors favor such, especially with payment based on the volume of grout pumped. Conversely, in water control it is necessary to fill sufficient voids to create a continuous impermeable curtain. Very large grout quantities are often required, so the lowest cost, effective mixture available, should be injected at the highest pumping rates and pressures that can be safely used. The grout must be resistant to washout which can be readily achieved with standard concrete admixtures. To stop rapid flows of moving water, a pumping rate sufficiently fast to literally overwhelm the water flow should be used. While past practice has often employed expensive special grout materials and unique injection equipment to slowly build up plugs in the formation, available concrete pumps and advanced concrete mix design, now allow placement of very large quantities of cohesive, stable, grout material very quickly. This allows us to virtually overwhelm even massive flows of water rapidly, while using readily available resources.

The geology of the Mid-Atlantic Region of the United States includes carbonate rock prone to solutioning and sinkhole development. Grouting for sinkhole repair has gained popularity in this area for two primary reasons. First, demand has increased for the benefits realized from successfully implemented grouting projects. Second, supply of Geotechnical professionals and contractors advocating its use has increased. There are different approaches taken by professionals and contractors in the Mid-Atlantic Region regarding the use of grouting for sinkhole repair. The broad term of "Pressure Grouting" is often used in the local vernacular to describe the process. This term can be expected to include many different materials, methods, and opinions. One idea that consistently appears around sinkhole repair programs relates to the difficulty in budgeting such projects due to the inherent, obvious unknowns associated with the geology and the sinkhole mechanism. While it must be admitted that the very nature of sinkhole repair presents difficulties in estimating the actual costs, the authors argue that reasonable estimates can be formulated. This paper presents the perspective of Geotechnical Engineers turned grouting contractors. An approach to grouting for sinkhole repair and two case histories are presented herein.

The Geotechnical Engineering Section of the Tennessee Department of Transportation developed karst maps for use in planning and locating new highway corridors in East Tennessee. Using existing 7.5 minute topographic quadrangle maps with 6 meter (20 foot) contour intervals, areas of high concentrations of sinkhole development can be identified in relation to proposed highway corridors. A total of six karst geohazard maps showing areas of high concentrations of sinkholes and numerous caves were developed for certain roadway projects in East Tennessee. These include SR 475, I-140, and SR 71 in Knox County, SR 91-Extension in Carter County, and I-181 Welcome Center and SR 357 in Sullivan County. By using these karst maps, geologists and engineers have been able to better select corridor routes for future design and construction projects that can provide a more environmentally friendly alignment.

Prior to construction, a geotechnical evaluation was conducted of the 90-mile long Wyoming to Jackson's Ferry 765 kilovolt electrical transmission line that included almost 60 miles in the section on the southern end of the line that could be underlain by carbonates. The evaluation concentrated on the planned tower locations along the 200-foot wide corridor through southern West Virginia and western Virginia. It was determined that 40 of the 219 tower sites in that section were underlain by formations where significant karst could be anticipated. The work included compiling the geology for the entire corridor and identifying the potentially karst forming formations. Field reconnaissance, drilling and geophysics (electrical imaging) was conducted to determine site conditions. Potentially affected towers were moved or replaced with multiple structures in areas where karst features could directly impact the stability of a tower or where construction could affect the karst system. Abandoned surface iron and manganese mines were also encountered during the work.

Quarrying in karst poses potential environmental risk. Historically, well-documented, large-scale negative impacts related to extensive and deep quarries, include dewatering of aquifers, changes in groundwater flow, and induction of land subsidence and sinkholes. Estimating and mitigating risk prior to quarrying are difficult. Some geotechnical techniques in karst may be unreliable or imprecise owing to a high degree of anisotropy and heterogeneity transmitting groundwater exclusively through fractures (secondary porosity) and dissolutionally enlarged openings (tertiary porosity). Surficial geophysical investigations, (e.g. electrical resistivity, ground-penetrating radar, seismic exloration, lineament analysis) are useful but rarely definitive in characterizing a quarry site. Borehole geophysics, although very precise within each well, may not reflect the true configuration of conduit flow within the footprint of the quarry. Statistically, wells drilled in dense bedrock with wide fracture spacing may intersect few, if any, significant openings. Geophysical parameters and pump tests from such wells may lead to erroneous hydrogeologic conclusions about the site, including the areal extent of influence of a quarry. Dye-trace studies typically provide a better indication of potential risk. Quarries close to zones of recharge may introduce steep hydraulic gradients near the excavation, augmenting discharge into the opening. Conversely, quarries distant from such zones may produce much gentler gradients and have a reduced environmental impact.

Six electrical resistivity profiles were acquired along separate parallel traverses at the Route 60 study site in Springfield, Missouri. Analysis of the acquired geophysical data supports the conclusion that limestone bedrock within the study area is dissected by numerous near-orthogonal solution-widened joint sets that trend NNW and ENE, respectively. All of the more visually-prominent solution-widened joints imaged on the resistivity profiles are interpreted as clay-filled; several extend to depths of more than 16 m (below top-of-bedrock). None of the solution-widened joints appears to be air-filled.

The territory of the Tatarstan Republic is located within the soluble Permian sequences (mainly limestone, dolomite and gypsum), which occur at a low depth under the surface (up to 200–300 m). About 96% of studied territory is karst hazardous. Oil and gas pipelines, as well as pipelines of different purpose (the total length over 55 thousand km) are maintained within the limits of the Tatarstan Republic territory. The paper is devoted to main approaches for karst economic risk assessment with reference to pipelines. The algorithms of the probabilistic-deterministic assessment of karst economic risk on regional and local levels by the example of karst terrain in the southeast of the Tatarstan Republic are the subject of our discussion. The assessment of karst economic risk of the losses is carried out on the basis of the analysis of geological structure of territory, hydrogeological and engineering-geological conditions of territory, identification and prediction of karst hazards in time and space, assessment of vulnerability of linear objects to karst hazards. The obtained values of economic risk are the basis for choosing alternative pipeline routes, for estimating service conditions and engineering protection measures.

The Vazante Zinc Mine is located in the Vazante District of the Minas Gerais Province of Brazil. The zinc ore is mined from underground operations and is located in a well-developed fracture zone in karstic dolomites belonging to the Vazante Group. The mine has an installed pumping capacity of 16000 cubic meters of water per hour and pumps an annual average of 6300 cubic meters per hour. In April 1999, the underground mining operations intercepted a karstified structural zone causing a flood on the order of 5000 cubic meters per hour, which, in turn, affected the local dolomite groundwater table. The accelerated lowering of the water table caused damage to surface installations due to the generation of a doline of approximately 1000m in diameter and up to 0.4m deep. Since this incident, more than 821 new sinkholes and dolines have been observed in the vicinity of the mine, and Votorantim has intensified its hydrogeological studies. The currently implemented monitoring scheme and data management system have greatly assisted the mine in minimizing risks and impact to the environment.

Karstic terrain constitutes one of the most difficult grounds to be explored and assessed by engineers due to its unpredictable geometry and the voids that lie in the subsurface. This geological formation is normally associated with soluble rocks, of which one of the most typical representations is calcium sulphate. Calcium sulphate was found to extend over more than 20% of the land surface on the earth. It exists in various forms, the most common ones are gypsum (CaSO₄·2H₂O) and anhydrite (CaSO₄). The existence of gypsum terrains under construction zones is dangerous due to the collapsible nature of gypsum with the presence of water. Remarkable evidences are available on failures in dams, highways and some other structures constructed above gypsiferous soils or rocks. In this paper, some of the physical and chemical properties of gypsum are reviewed. Then the authors present the gypsum-anhydrite transition phenomena and the existing techniques for stabilizing gypsiferous terrains.

Throughout Central Texas burgeoning development and population growth in urban and semi-rural areas have led to increased demand for alternative traffic routes, as well as improvements of existing roadways. As growth occurs around urban and suburban centers, traffic alignment alternatives are increasingly planned for previously undisturbed areas dominated by karst zones with a high probability for presence of threatened and/or endangered karst invertebrate and endangered bird species habitat. In this area, routine geologic assessments conducted in association with roadway design have recently expanded methodologies to include the application of various geophysical techniques as field-screening tools to better determine possible extent of subsurface caverns and sinkholes. The potential for endangered species habitat, specifically the Bone Cave Harvestman (Texella reyesi), the Coffin Cave mold beetle (Batrosides texanus) and the Tooth Cave ground beetle (Rhadine persephone) have led to the need for early coordination with regulatory agencies and establishing creative techniques for evaluating construction-related impacts. These innovative approaches have proven key to the engineering design, approval and implementation of roadway improvements and the development of sound environmental plans to mitigate and protect natural resources while meeting the demands of construction schedules.