Robert G. Tipping

Deep Time Origins of Sinkhole Collapse Failures in Sewage Lagoons in Southeast Minnesota

1850s and 1930s filled many of the conduit systems with soil. Over eighty years of soil conservation efforts have significantly reduced the flux of mobilized soil into the conduits. Those conduits are currently flushing much of those stored soils out of their spring outlets. Finally, the increased frequency and intensity of major storm events is reactivating conduit segments that have been clogged and inactive for millions of years.

Electronic Access to Minnesota Springs, Karst Features & Groundwater Tracing Information

Poster presentation highlighting history, availability and tools for three statewide GIS resources: Minnesota Karst Feature Database (KFD), the Minnesota Groundwater Tracing Database (MGTD), and the Minnesota Spring Inventory (MSI). Collectively, this information is a significant asset for use in water resource planning and management in the State of Minnesota.

A multidisciplinary-based conceptual model of a fractured sedimentary bedrock aquitard: improved prediction of aquitard integrity

A hydrogeologic conceptual model that improves understanding of variability in aquitard integrity is presented for a fractured sedimentary bedrock unit in the Cambrian-Ordovician aquifer system of midcontinent North America. The model is derived from multiple studies on the siliciclastic St. Lawrence Formation and adjacent strata across a range of scales and geologic conditions. These studies employed multidisciplinary techniques including borehole flowmeter logging, high-resolution depth-discrete multilevel well monitoring, fracture stratigraphy, fluorescent dye tracing, and three-dimensional (3D) distribution of anthropogenic tracers regionally. The paper documents a bulk aquitard that is highly anisotropic because of poor connectivity of vertical fractures across matrix with low permeability, but with ubiquitous bed parallel partings. The partings provide high bulk horizontal hydraulic conductivity, analogous to aquifers in the system, while multiple preferential termination horizons of vertical fractures serve as discrete low vertical hydraulic conductivity intervals inhibiting vertical flow. The aquitard has substantial variability in its ability to protect underlying groundwater from contamination. Across widespread areas where the aquitard is deeply buried by younger bedrock, preferential termination horizons provide for high aquitard integrity (i.e. protection). Protection is diminished close to incised valleys where stress release and weathering has enhanced secondary pore development, including better connection of fractures across these horizons. These conditions, along with higher hydraulic head gradients in the same areas and more complex 3D flow where the aquitard is variably incised, allow for more substantial transport to deeper aquifers. The conceptual model likely applies to other fractured sedimentary bedrock aquitards within and outside of this region.RésuméUn modèle conceptuel hydrogéologique, qui améliore la compréhension de la variabilité spatiale de l’intégrité d’un semi-perméable, est présenté pour une unité de substratum sédimentaire fracturé du système aquifère Cambro-Ordovicien du milieu du continent nord-américain. Le modèle est dérivé de multiples études portant sur la formation silicoclastique St. Lawrence et les couches adjacentes, avec une large gamme d’échelles et de conditions géologiques. Ces études ont mis en œuvre des techniques multidisciplinaires comprenant des mesures au micro-moulinet en forage, du monitoring de forage multi-niveaux à haute résolution au sein d’intervalles discrets, du traçage avec traceur fluorescent et, régionalement, la distribution tri-dimensionnelle (3D) de traceurs anthropogéniques. Cet article étudie un volume de semi-perméable qui est fortement anisotrope à cause de la faible connectivité des fractures verticales qui traversent une matrice de faible perméabilité, mais comportant des diaclases ubiquistes parallèles à la stratification. Les diaclases génèrent une forte perméabilité horizontale, analogue à celle des aquifères du système, tandis que les multiples horizons de terminaison préférentielle des fractures verticales forment des intervalles discrets de faible perméabilité verticale qui inhibent l’écoulement vertical. Le semi-perméable a une variabilité substantielle de son aptitude à protéger l’eau souterraine sous-jacente de la contamination. Au sein des vastes zones où le semi-perméable est enfoui profondément sous des formations plus récentes, la terminaison préférentielle des horizons confère une forte intégrité au semi-perméable (i.e. une protection). La protection est réduite à proximité des vallées incisées où le relâchement des contraintes et l’altération ont augmenté le développement d’une porosité secondaire, comprenant une meilleure connexion des fractures à travers ces horizons. Ces conditions, ainsi que des gradients hydrauliques plus forts dans les mêmes zones et un flux 3D plus complexe là où le semi-perméable est variablement incisé, permettent un transport plus substantiel vers les aquifères plus profonds. Le modèle conceptuel s’applique probablement à d’autres semi-perméables de substratum sédimentaire fracturé au sein ou à l’extérieur de cette région.ResumenSe presenta un modelo hidrogeológico conceptual que mejora la comprensión de la variabilidad en la integridad del acuitardo para una unidad de roca sedimentaria fracturada en el sistema acuífero Cámbrico-Ordovícico del medio continente de América del Norte. El modelo se deriva de múltiples estudios sobre la formación silicoclástica de St. Lawrence y los estratos adyacentes a través de un rango de escalas y condiciones geológicas. Estos estudios emplearon técnicas multidisciplinarias que incluyen el registro del caudalímetro del pozo, el monitoreo discreto de alta resolución de multinivel de profundidad de los pozos, la estratigrafía de las fracturas, el trazado de colorantes fluorescentes y la distribución tridimensional (3D) de trazadores antropogénicos a nivel regional. El trabajo documenta un acuitardo que es altamente anisotrópico debido a la mala conectividad de las fracturas verticales a través de la matriz con baja permeabilidad, pero con separaciones extendidas en forma paralela en el lecho. Las divisiones proporcionan una conductividad hidráulica horizontal alta, análoga a acuíferos en el sistema, mientras que los horizontes de terminación preferencial múltiple de las fracturas verticales sirven como intervalos discretos de conductividad hidráulica vertical baja que inhiben el flujo vertical. El acuitardo tiene una variabilidad sustancial en su capacidad para proteger el agua subterránea subyacente de la contaminación. En áreas extensas donde el acuitardo está profundamente enterrado por un lecho rocoso más joven, los horizontes de terminación preferencial proporcionan una alta integridad del acuitardo (es decir, protección). La protección se reduce cerca de los valles, donde la liberación de estrés y la intemperie han mejorado el desarrollo de los poros secundarios, incluyendo una mejor conexión de las fracturas en estos horizontes. Estas condiciones, junto con mayores gradientes de la carga hidráulica en las mismas áreas y un flujo 3D más complejo donde el acuitardo está incidido de forma variable, permiten un transporte más importante hacia acuíferos más profundos. Es probable que el modelo conceptual se aplique a otros acuitardos de roca sedimentaria fracturados dentro y fuera de esta región.摘要这里展示了北美大陆中部寒武-奥陶含水层系统破碎沉积基岩单元能提高认识弱透水层整体性变化的水文地质概念模型。模型源自对不同尺度和各种地质条件下硅质碎屑St. Lawrence 地层和毗邻地层的多项研究。这些研究采用了多学科技术,包括钻孔流量测井、高分辨率深度分离多级井监测、断裂地层学方法、荧光染色示踪、区域人为示踪剂三维分布等。本文论述了一个整体弱透水层,这个弱透水层高度各相异性,因为穿过透水性低、但具有无所不在的地层平行缝隙的基质的垂直断裂联系度很差。缝隙提供了很高的整体横向水力传导率,与系统中含水层相似,而多个垂直断裂的优先终点层成为控制垂直水流的分离垂直水力传导率区间。弱透水层在保护下伏地下水免遭污染的能力上有很大的变化性。在弱透水层被年轻基岩深深掩埋的广大地区,有限终点层提供了很高的弱透水层整体性(即保护)。在切割的山谷附近,应力释放和风化增强了次生空隙发育,包括穿过这些层的联系度进一步改善,因此,保护作用降低。这些条件,伴随同一地区较高的水头梯度,以及更复杂的三维水流,造成弱透水层被处处分割,使更多的水流运移到深部含水层。概念模型还可以用于本地区或者其他地区断裂沉积基岩弱透水层中。ResumoUm modelo conceitual hidrogeológico que melhora o entendimento da variabilidade da integridade de aquitardos é apresentado para as unidades sedimentares fraturadas do sistema aquífero Cambro-Ordoviciano da América do Norte central. O modelo deriva de diversos estudos na Formação St. Lawrence, unidade siliciclástica e estratos adjacentes, em diversas escalas e condições geológicas. Estes estudos aplicaram técnicas multidisciplinares tais como perfilagem de poço com medidor de fluxo, poços de monitoramento multiníveis de alta resolução, estratigrafia de fraturas, testes com traçadores fluorescentes, e distribuição tridimensional (3D)regional de traçadores antropogênicos. O presente trabalho documenta um aquitardo altamente anisotrópico devido a baixa conectividade de fraturas verticais desenvolvidas na matriz de baixa permeabilidade, porém apresentando fraturas horizontais pervasivas no acamadamento. As fraturas horizontais proporcionam altas condutividades hidráulicas nesta direção, análogas à aquíferos no sistema, enquanto os múltiplos horizontes de terminação de fraturas verticais agem como intervalos discretos de baixa condutividade hidráulica vertical inibindo fluxo vertical. O aquitardo tem grande variabilidade em sua habilidade de proteger as águas subterrâneas subjacentes de potenciais fontes de contaminação. Ao longo de amplas áreas onde o aquitarde encontra-se sobreposto por unidades mais jovens, os horizontes de terminação preferencial propocionam alta integridade do aquífero (ou seja, alta proteção). A proteção diminui nas imediações de vales incisos onde o alívio de pressões litostáticas e intemperismo intensificaram o desenvolvimento de porosidade secundária, incluindo melhor conexão de fraturas através destes horizontes. Estas condições, em conjunto com maiores gradientes hidráulicos nas mesmas áreas e fluxos 3D mais complexos onde o aquitarde apresenta desenvolvimento de vales incisos, permitem maior transporte para aquíferos mais profundos. O modelo conceitual tem potencial aplicação para outros aquitardos sedimentares fraturados dentro ou fora da região estudada.

History and Future of the Minnesota Karst Feature Database

Since the 1990s the University of Minnesota and the Minnesota Department of Natural Resources have maintained a karst features database that is used to conduct research on karst processes and inventory karst features. Originally designed as a tabular database only, the karst features database developed into a spatial database in 2002 with tabular data stored in Microsoft Access and a spatial component managed in ESRI ArcView. In 2012 the database was converted to a single, relational database platform, PostgreSQL, with both tabular and spatial components edited in ESRI ArcMap. Custom editing forms are written in Visual Basic and are accessed in ArcMap sessions by ESRI add-ins. The current database infrastructure allows for remote editing. Read-only versions of the data are available in GIS/spatial format for public use via web services. Future development plans include links to water chemistry data, water level measurements, and other ancillary data; along with the addition of vectors to represent dye traces and polygons for larger karst features. Introduction Karst is recognized as a term describing both distinct landscapes—karst terrains—and distinctive hydrology related to the movement of water in soluble bedrock – karst processes. The construction of a karst features database that adequately documents both karst terrains and karst processes for researchers, regulators, and planners is a formidable task. How do uses and potential abuses impact database design and content? What should be in such a database? How does data get in, or out? While the Minnesota Karst Features Database (KFD) has been primarily research oriented, these broader questions have guided past and current database development and will continue to guide development going forward. This paper documents the history and future of the KFD, with the goal of providing the reader a better understanding of how it came to be and where it is going. History and Methods The Minnesota Speleological Survey created the database in the early 1970s as a sinkhole inventory. Sinkhole locations were collected on 4-by-6 inch index cards with unique identifiers, and plotted on 1:24,000-scale USGS 7.5-minute topographic maps (Alexander, 2015). About one hundred sinkholes were mapped in this manner, and this process continued into the early 1980s. Many sinkholes in Minnesota, especially those several meters or less in diameter, are ephemeral features that appear in fields and are filled, if possible, to minimize disruption of agricultural practices. As personal computers and spreadsheet software became available in the 1980s the evolution towards fully functional geographic information systems (GIS) manTipping, Robert G. University of Minnesota, Minnesota Geological Survey, 2609 Territorial Road, St. Paul, Minnesota, 55114, USA, tippi001@umn.edu Rantala, Mathew University of Minnesota, Minnesota Geological Survey, 2609 Territorial Road, St. Paul, Minnesota, 55114, USA, mjrantal@umn.edu Alexander, E. Calvin Jr. University of Minnesota, Department of Earth Sciences, 310 Pillsbury Drive SE, Minneapolis, Minnesota, 55455, USA, alexa001@umn.edu Gao, Yongli Center for Water Research, Department of Geological Sciences, University of Texas, San Antonio Department of Geological Sciences, One UTSA Circle, San Antonio, Texas 78249, USA, yongli.gao@utsa.edu Green, Jeffrey A. Minnesota Department of Natural Resources, Ecological and Water Resources, Rochester Office, 3555 9th Street NW, Suite 350, Rochester Minnesota, 55901, USA, Jeff.green@state.mn.us