Geology topics

Research about Prairie du Chien-Jordan aquifer

Source-linked reports with geographic coverage including Prairie du Chien-Jordan aquifer.

4 recordsLinked to original sources

USGS1999

Hydraulic properties of the Prairie du Chien-Jordan aquifer, Shakopee Mdewakanton Sioux Community, southeastern Minnesota, 1997

An aquifer test of the Prairie du Chien-Jordan aquifer was conducted in the Shakopee Mdewakanton Sioux Community located southwest of the Twin Cities metropolitan area. A well open to the Jordan Sandstone was pumped at 600 gallons per minute for 57 hours. Drawdown was monitored in three observation wells located near the pumped well. These wells were open to: (1) the Jordan Sandstone, the principal unit of the aquifer; (2) the Prairie du Chien Group, a secondary, carbonate-rock unit of the aquifer; and (3) a confined, glacial-drift sand aquifer. Test results indicate that the Jordan Sandstone had a transmissivity of 6,267 ft 2 /d, a storativity of 1.193 x 10 -4 , a horizontal hydraulic conductivity of 31 ft/d based on a saturated thickness of 204 ft, and a ratio of vertical to horizontal hydraulic conductivity of 5.29 x 10 -4 . The pumped well was hydraulically connected to the Prairie du Chien Group observation well. No drawdown was observed in the observation well completed in the confined, glacial-drift sand aquifer; thus, a hydraulic connection of this observation well to the pumped well was not indicated.

Minnesota↗

USGS1998

Water-quality assessment of part of the upper Mississippi River Basin, Minnesota and Wisconsin— Ground-water quality in the Prairie du Chien-Jordan aquifer, 1996

The Prairie du Chien-Jordan (PDCJ) aquifer (Prairie du Chien-Trempealeau aquifer in Wisconsin), composed of dolomite and sandstone of Cambrian to Ordovician age, is the principal bedrock aquifer in the Upper Mississippi River study unit of the National Water-Quality Assessment (NAWQA) Program. The aquifer supplies approximately 75 percent of the ground water withdrawn in the area. In certain areas, the aquifer is overlain by bedrock or glacial deposits having low hydraulic conductivity (termed "confined portion" of the aquifer in this report). In other areas the aquifer is overlain by glacial sand and gravel deposits having greater hydraulic conductivity (termed "unconfined portion" of the aquifer in this report). Differences in the hydrogeologic characteristics of these overlying units have potential to affect the downward movement of water and of contaminants into the aquifer from the land surface. Ground-water samples were collected from 50 domestic wells completed in this aquifer in July, August, and September of 1996 as part of the U.S. Geological Survey's National WaterQuality Assessment Program. The purpose of this report is to describe the chemical characteristics of water in the PDCJ aquifer and to summarize the differences in water quality in confined and unconfined portions of the aquifer. Twenty-five wells were sampled in each portion of the aquifer. Water samples from the wells were measured for physical parameters and analyzed for concentrations of major ions, nutrients, dissolved organic carbon, trace metals, radon, tritium, pesticides, and volatile organic compounds. Differences in anthropogenic and naturally occurring materials in water between confined and unconfined portions of the PDCJ aquifer are small and frequently the differences are not statistically significant at the 95 percent confidence level. Dissolved oxygen concentrations were slightly less and specific conductances and alkalinities were slightly greater in water in the confined portion of the aquifer. Only the differences in specific conductance and alkalinity, however, were statistically significant at the 95 percent confidence level (two sample t-test). Concentrations of most major ions were generally greater in water from the confined portion of the aquifer. Nitrate (nitrite plus nitrate as N) and phosphorus were generally greater in the unconfined portion of the PDCJ aquifer although the differences were not statistically significant at the 95 percent confidence level (nonparametric Mann-Whitney test). In the confined portion of the aquifer no samples exceeded the maximum contaminant level of 10 milligrams per liter for nitrate. In the unconfined portion of the aquifer nitrate in two samples exceeded the maximum contaminant level of 10 milligrams per liter. Phosphorus concentrations were generally about an order of magnitude less than nitrate concentrations. Iron and manganese concentrations commonly exceeded the secondary maximum contaminant levels set by the U.S. Environmental Protection Agency and were generally greater in the confined portion of the PDCJ aquifer, although the differences were not statistically significant at the 95 percent confidence level (nonparametric Mann-Whitney test). Radon concentrations were greater in the confined portion of the aquifer than in the unconfined portion, although the difference was not statistically significant at the 95 percent confidence level (two sample t-test), with medians of 500 and 340 picoCuries per liter, respectively. Sixty-six percent of the radon concentrations were greater than the suspended maximum contaminant level of 300 picoCuries per liter. Tritium concentrations indicate that water in the unconfined portion of the PDCJ aquifer may have been recharged more recently than water in the confined portion of the aquifer, although differences in tritium concentrations between confined and unconfined portions of the aquifer were not statistically significant at the 95 percent confidence level (nonparametric MannWhitney test). Atrazine and its metabolite, deethylatrazine, were the most frequently detected pesticide compounds in water samples from the PDCJ aquifer. Volatile organic compounds were detected in 41 of the 50 water samples, but none of the concentrations exceeded 1 microgram per liter. Concentrations of volatile organic compounds were slightly greater in the unconfined portion, although the differences in detection rates were not statistically significant at the 95 percent confidence level (nonparametric Mann-Whitney test). Carbon disulfide and methyl chloride were the most frequently detected volatile organic compounds. Water in the unconfined portion of the PDCJ aquifer in Minnesota and Wisconsin appears to be affected to a greater degree by anthropogenic activities than water in the confined portion of the aquifer. Water in the confined portion has a longer residence time and greater concentrations of dissolution products of minerals. In general, however, differences in anthropogenic and naturally occurring materials among confined and unconfined portions of the aquifer are small and frequently not significantly different.

Minnesota, Wisconsin↗

USGS1985

Ground-water flow in the Prairie du Chien-Jordan aquifer related to contamination by coal-tar derivatives, St. Louis Park, Minnesota

A three-dimensional, ground-water-flow model of the Prairie du Chien-Jordan aquifer and associated hydrogeologic units was developed to evaluate the movement of coal-tar derivatives from a coal-tar distillation and wood-preserving plant in St. Louis Park, Minnesota. A finite-difference grid was superimposed on the modeled area, which includes most of eastern Hennepin County. The individual cells are 400-foot squares in the center of the grid (St. Louis Park area); the cells increase in dimension toward the outside limits of the grid. Five geologic units are represented by four layers in the model. These units include the Jordan Sandstone, the Prairie du Chien Group (dolomite and sandy dolomite), the basal confining unit of the St. Peter Sandstone (silty and sandy shale), the St. Peter Sandstone, and glacial deposits in bedrock valleys. The model was calibrated for steady-state conditions for a period before significant ground-water development (1885-1930) and for a period of significant pumping stress (winter conditions, 1970 fs). A transient calibration was accomplished by simulation of a period during which seasonal changes in potentiometric head in the Prairie du Chien-Jordan aquifer were significant (1977-80). Sensitivity testing indicated that leakage to the upper model layer and the vertical hydraulic conductivity of the basal confining unit of the St. Peter Sandstone were the model hydrologic properties which, when changed, resulted in the greatest changes in model-calculated water levels. The calibrated model generally calculates water levels that are within 10 feet of measured values. Model simulations indicate that the potentiometric surface of the Prairie du Chien-Jordan aquifer would be raised by as much as 3 feet in the area of the plant site by water introduced into the aquifer through wells open to more than one aquifer system. The cones of impression created at these wells could have a significant impact on the transport of contaminants in the Prairie du Chien-Jordan. The presence of coal-tar derivatives in the aquifer has been difficult to explain in wells located upgradient from the plant site to the north, west, and southwest. Simulations suggest that, during periods of heavy withdrawal from certain of these wells (SLP10, SLP15, and SLP5), local hydraulic gradients may have been altered, resulting in the potential for the movement of contaminants from the area of the plant site to the wells. Cones of impression at multiaquifer wells near the plant site contributed to the alteration of local gradients. Simulation of a proposed gradient-control plan, in which lateral homogeneity and isotropy of individual hydro geologic units was assumed, indicates that the actions would be effective in limiting expansion of the contaminated volume in the Prairie du Chien-Jordan aquifer. The plan includes the control of withdrawal from five wells. The simulations also show, however, that modelcalculated potentiometric surfaces are sensitive to changes in withdrawal rates at wells not intended to be under the control of the plan. Management of discharge from these wells also will be important to overall effectiveness of the remedial-action plan.

Minnesota↗

USGS1983

Hydrogeologic and water-quality characteristics of the Prairie du Chien-Jordan aquifer, Southeast Minnesota

Quality of water in the Prairie du Chien-Jordan aquifer is generally good, except for some localized contamination, Coal-tar derivatives that contaminate the aquifer in St. Louis Park, a western suburb in the Twin Cities Metropolitan Area, pose the most serious threat to water quality. High hardness and iron concentration limit suitability for municipal and industrial use in parts of extreme southeast Minnesota. Confining beds of bedrock and drift, however, protect most of the aquifer from surface pollutants. The Prairie du Chien-Jordan aquifer is part of a sequence of sedimentary bedrock units in southeast Minnesota. The Jordan Sandstone is a white to yellow, fine- to coarse-grained sandstone. The Prairie du Chien Group comprises two dolomitic formations that are vuggy and fractured and interbedded with thin layers of shale. The aquifer formations were deposited in Paleozoic seas that occupied the Hollandale embayment. The aquifer dips toward the interior of the embayment where it is as deep as 750 feet below land surface and as thick as 500 feet. Permeability is secondary in the Prairie du Chien Group because of solution cavities and fractures, and intergranular in the Jordan Sandstone. Water in the aquifer is confined except in the eastern part. Water generally flows to the north and east into the Minnesota and Mississippi Rivers. A ground-water divide separates part of the flow southward into Iowa. This aquifer supplies more water than any other bedrock one in the State. Calcium magnesium bicarbonate type water is most common in the aquifer. Calcium and sulfate and, to a lesser degree sodium and magnesium, increase in concentration toward the southwestern part of the study area. Bicarbonate concentration, on the other hand, decreases toward the southwestern corner of the study area. Leakage from overlying Cretaceous deposits is the source of much of the sulfate and other minerals in the southwest. This report is one of a series on the hydrogeology and water quality of the 14 principal aquifers in Minnesota prepared by the U. S. Geological Survey. The U. S. Environmental Protection Agency requested these studies because of the need for information to develop its Underground Injection Control Program.

Minnesota↗