Browsing by Author "Tipping, Robert G."

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    C-30 Geologic Atlas of Wright County, Minnesota [Part A]
    (2013) Tipping, Robert G.
    Surface and subsurface geology of Wright County, Mn. includes bedrock topography and depth-to-bedrock. Additional data added 2015; raster data sets of the elevation of the top and bottom, and the thickness of bedrock units in Wright County.
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    Characterizing groundwater flow in the Twin Cities metropolitan area, Minnesota a chemical and hydrostratigraphic approach.
    (2012-06) Tipping, Robert G.
    Historic chemical and isotopic data for groundwater within the 11 county Twin Cities Metropolitan Area, extended (TCMAx) were used to distinguish three regional groundwater types based on similar chemical and isotopic composition: 1.) recent waters, characterized by detectable tritium, elevated chloride and/or the presence of anthropogenic compounds; 2.) waters with elevated strontium to calcium plus magnesium ratios; and 3.) naturally elevated chloride-distinct from recent waters based on carbon-14 dating and low chloride to bromide ratios where sufficient data exists. The three-dimensional distribution of these hydrochemical facies were compared to permeability of unconsolidated sediments, the distribution of macropores within sedimentary (Paleozoic) bedrock, and the regional distribution of vertical hydraulic head gradient. Results of this investigation demonstrate that groundwaters within the TCMAx can be broadly categorized by chemical composition, and that their distribution is controlled both by regional differences in subsurface permeability and natural hydraulic head gradients, and by regional changes in hydraulic gradient due to high-capacity pumping. Chloride content and chloride to bromide ratios, in particular, can be used to identify the presence of recently recharged groundwater in bedrock aquifers and further characterize the movement of these recent waters through bedrock macropores. Urban groundwater systems present unique challenges for resource management and scientific investigations due in large part to the transient nature of hydraulic head gradients and changing landuse. For urban planners charged with groundwater resource management, results in this thesis demonstrate the utility of having groundwater hydrochemical types fully integrated with a hydrogeologic framework model in a three-dimensional geographic information system (GIS) environment, where age and chemical quality of groundwaters can be compared with other, more familiar factors, such as locations and pumping levels of high capacity wells. For groundwater modelers of urban aquifers, these same results can guide conceptual models of recharge to bedrock aquifers and constrain model calibration to produce flux estimates in agreement with flowpaths indicated by the distribution of recent waters.
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    OFR14-02, Geologic controls on groundwater and surface water flow in southeastern Minnesota and its impact on nitrate concentrations in streams
    (Minnesota Geological Survey, 2014) Runkel, Anthony C.; Steenberg, Julia R.; Tipping, Robert G.; Retzler, Andrew J.
    This report summarizes the results of a Minnesota Geological Survey (MGS) investigation conducted for the Minnesota Pollution Control Agency (MPCA) designed to support watershed planning efforts in southeast Minnesota. Specifically it provides better understanding of the geologic controls on nitrate transport in the region, including nitrate in groundwater that is the source of baseflow to streams. Nitrate contamination of surface water and groundwater is a long- standing issue in southeastern Minnesota. We focused much of our investigation on an evaluation of nitrate (NO3 ion) transport in the Root River watershed because of the relatively advanced understanding of the karstic conditions in that area. However, the overall scope of the project includes the entire bedrock-dominated landscape of southeast Minnesota. Our results therefore support a broader MPCA watershed planning effort that directly pertains to the Root River, as well as to other watersheds within the Lower Mississippi River Basin in Minnesota.
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    OFR14-03, Geologic Controls on Groundwater and Surface Water Flow in Southeastern Minnesota and its Impact on Nitrate Concentrations in Streams: Local Project Area Report
    (Minnesota Geological Survey, 2014) Steenberg, Julia R.; Tipping, Robert G.; Runkel, Anthony C.
    This report summarizes the results of part of a Minnesota Geological Survey (MGS) investigation conducted for the Minnesota Pollution Control Agency (MPCA) designed to support watershed planning efforts in southeast Minnesota. The broader project provides better understanding of the geologic controls on nitrate transport in the region, including nitrate in groundwater that is the source of baseflow to streams. This report describes a local scale subproject focused on a relatively small part of the Root River watershed in Fillmore County. We conducted new mapping that provides a more detailed depiction of the geologic conditions in a three dimensional electronic format suitable for groundwater-surface water modeling. In addition, we used existing maps and reports along with new field data collected during the course of this project to improve the hydrostratigraphic characterization of the bedrock. This led to a more comprehensive understanding of the hydrostratigraphic attributes of bedrock that forms the Upper Carbonate Plateau, which dominates the landscape in the local project area. Cross sections within the local project area are used to illustrate how nitrate is transported in the ground and surface water system.
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    OFR14-05, A HYDROCHEMICAL SURVEY OF GROUNDWATER FLOW IN THE ROCHESTER METROPOLITAN AREA, MINNESOTA
    (Minnesota Geological Survey, 2014) Tipping, Robert G.
    Historical chemical and isotopic data from Olmsted County, Minnesota were used to distinguish groundwater types based on similar chemical and isotopic composition. The extent of recent waters, identified by detectible tritium, chloride, nitrate or sulfate concentrations above background levels, along with groundwaters having elevated calcium to magnesium molar ratios were mapped in three dimensions. The distribution of these waters can be explained, in part, by the permeability of unconsolidated sediments overlying bedrock, bedrock hydrostratigraphy, and vertical hydraulic gradients within the Rochester Central Metropolitan Area (RCMA) dueto high capacity pumping. The spatial distribution of groundwater chemical types is also a function of changes in vertical hydraulic gradients with time. Within the last 20 years, the extent of recent waters within the RCMA has expanded both horizontally and vertically. Groundwater calcium to magnesium ratios in the Prairie du Chien Group (Shakopee aquifer) and the Jordan Sandstone (Jordan aquifer) within the RCMA have also increased and show greater variability through time, indicating a greater percentage of recharge to these aquifers moving vertically within the RCMA and from the Decorah edge than before high-capacity pumping began.
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    OFR15-01, HYDRAULIC CONDUCTIVITY AND HYDROSTRATIGRAPHY OF THE PLATTEVILLE FORMATION, TWIN CITIES METROPOLITAN AREA, MINNESOTA
    (Minnesota Geological Survey, 2015) Runkel, Anthony C.; Steenberg, Julia R.; Tipping, Robert G.; Jansen, Steve; Retzler, Andrew J.
    This report synthesizes a large body of data that provide a better understanding of the hydrogeologic characteristics of the Ordovician Platteville Formation in the Twin Cities Metropolitan Area (TCMA). The carbonate-dominated Platteville Formation plays an important role in the TCMA hydrogeologic system by limiting vertical infiltration of relatively recent water to the more commonly utilized aquifers beneath it. Furthermore, it has been impacted by numerous contaminant plumes, which threaten the water quality in domestic wells and the large number (dozens) of springs along the Mississippi River and its tributaries. Hydraulic conductivity data are synthesized and interpreted across a range of scales, with the recognition of variable user needs. For example, generalized bulk hydraulic conductivity for parts of the Platteville Formation may be useful for modeling water budgets through relatively large areas. In contrast, more site-specific needs such as development of remediation strategies and prediction of flow paths may be facilitated by considering the large range in hydraulic conductivity, measured at a number of scales, and by recognizing the location of fast-flow secondary pore networks as well as key aquitards.