Controls on Groundwater Flow in a Karst Aquifer Near an Aggregate Quarry

- a collaborative project with Dr. Sarah Tindall of Kutztown University
and Dr. Lane Schultz of Berks Products Corp. (Ontelaunee Quarry)

Hydrogeology research groupContents:


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Because we get so much of our drinking water from wells that tap groundwater, and because the flow of groundwater has the potential to spread spills of harmful pollutants, it is important to be able to predict and model groundwater movement.  Groundwater flow through porous media such as sandstones can be modeled using Darcy’s Law because water interacts with the small particles of rock during slow intergranular fluid flow.  Groundwater flows through limestones much more quickly by a process called open channel fluid flow, however, because the groundwater moves through larger cavities formed by dissolution of the limestone.  Understanding the geologic controls on where these conduits form is thus critically important to discovering drinking water supplies and predicting flow of pollutants through limestones.  In addition to groundwater modeling applications, the ability to predict where dissolution caverns form is also key to mitigating sinkhole hazards and exploring for mineral deposits in limestones. 

Several geologic factors have the potential to localize the formation of dissolution features in limestone.  These include:  1) limestone strata that are more calcitic and therefore more soluble, 2) limestone strata with a higher initial intergranular porosity (i.e., number of holes between grains), a more favorable grain size, or a more conducive layering characteristic, and 3) fractures related to faulting or folding that focus groundwater flow and dissolution.

In cooperation with Berks Products, we are using a multidisciplinary approach to studying the controls on cave and conduit formation and groundwater flow near a limestone aggregate quarry near Ontelaunee, Berks County, Pennsylvania.  The project is an excellent example of how private industry can work together with small public universities like Kutztown University to give students practical experience doing research in the field.  Dr. Lane Schultz is a professional geologist working for Berks Products specializing in mining geology and hydrology.  Dr. Kurt Friehauf, a specialist in the geochemistry of water-rock interactions, and Dr. Sarah Tindall, a specialist in the physics and geometry of rock fracture, represent Kutztown University. 

Facets of the project

Jeremy monitoring well

Water table monitoring Part 1: Long-term water monitoring – paid internship

Provides one student with paid internship – a continuation of internship sponsored by Berks Products over the past two years

Students manually measure water level in each of 20 monitoring wells on the Ontelaunee Quarry property to detect long-term changes in groundwater flow in the study area

The shape of the water table is affected by the permeability of the rocks hosting the groundwater (i.e., the ease with which water flows through rock).  Over long periods of time, if there are no changes in the character of the rock, the water table establishes a stable, average shape.  If, however, the permeability of the rocks in the aquifer changes significantly when new caves open up or when old caves collapse, the water table will then shift until a new equilibrium state is achieved.  Monitoring and making maps of the water table on a weekly basis highlights sudden shifts in the overall shape of the water table and so indicates changes to the system of dissolution conduits. 

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Water table monitoring Part 2: Pump Test – Drs. Kurt Friehauf and Lane Schultz

Four undergraduate students involved - Autumn 2003:

Berks Products will pump water from a well drilled in the floor of the quarry at a rate of 10,000 – 15,000 gallons per minute in order to depress the water table in the study area

Automated pressure transducers with data loggers (i.e., devices that measure water level and water temperature in wells) mounted on ten (10) wells plus a head monitor (i.e., device that measures pressure) affixed to an artesian spring that bubbles up onto the floor of the quarry will be used to monitor groundwater fluctuations in response to pumping

Contour maps of water table will be made for each hour during pumping and for a 24 hour period following pumping

Although the water table establishes a generally stable equilibrium configuration over long periods of time, the water table experiences short term fluctuations in response to rain storms.  Rainwater enters the groundwater system by infiltration from the surface and by increased infiltration related to swollen streams.  This effect is amplified in the case of the Ontelaunee quarry because Berks Products pumps water out of the quarry pit, thereby depressing the local water table and creating a pressure difference (“head”) that draws groundwater from the streams (Maiden Creek and the Schuylkill River) toward the quarry.  The groundwater monitoring well field located between nearby streams and the quarry therefore provides an excellent opportunity for studying groundwater flow in response to changing head, thereby highlighting principal flow paths. 

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Water table monitoring Part 3: “Catching a Storm” – Drs. Kurt Friehauf and Lane Schultz

Four undergraduate students involved - Autumn 2003:

Automated pressure transducers with data loggers mounted on ten (10) wells located in the field between the quarry and the confluence of two nearby streams (Maiden Creek and the Schuylkill River)

Water levels and temperature in each well will be monitored every five (5) minutes for a 2-3 week period before, during, and after a rain event

Contour maps and shaded relief maps of the water will be drawn for each 5 minute time frame using ArcMap GIS software

Shaded relief maps for each time frame will be put together into a movie illustrating the response of the water table to changing inflow from the nearby swelling streams

Another way to determine principal groundwater flow paths through the aquifer is to measure groundwater levels in the monitor wells following a rainstorm.  Following a rainstorm, the water level in nearby streams goes up as the streams drain the land of rainwater.  Some of the water from the swollen streams infiltrates into the ground through fractures and sinkholes, thereby increasing the pressure (“head”) that drives groundwater flow.  Rainwater that falls on the surface also infiltrates down into the ground, further engorging the aquifer.  Water levels in the aquifer (i.e., the water table) bulge upward in zones of maximum flow.  This response to changing pressure is very rapid in limestone aquifers because the groundwater flows through cave channels with relatively little resistance.  It is therefore necessary to measure the water level in each of the 10 monitoring wells very frequently – on the order of every few minutes – during the rain event in order to observe the response of the water table to the storm.  Compiling the data into the form of an animated movie of a shaded relief model of the water table will compliment the pump test data and serve as an excellent visual aid for teaching introductory geology students in the classroom.

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Water table monitoring Part 4: Chemical fingerprinting of water-rock interactions – Drs. Kurt Friehauf and Lane Schultz

One undergraduate student involved - Autumn 2003:

When groundwater flows through limestone, the water dissolves a tiny amount of rock, slowly enlarging the dissolution conduits in the rock.  As a result of rock dissolution, elements characteristic of the dissolved rock become dissolved in the groundwater.  Calcitic limestone is rich in calcite (CaCO3), so interaction with groundwater with calcitic limestone would enrich the water with calcium ion.  Dolomitic limestone, on the other hand, is rich in the mineral dolomite (CaMg(CO3)2), so interaction with groundwater with dolomitic limestone enriches the water in both calcium and magnesium.  The dissolved rock therefore leaves a sort of geochemical fingerprint in the water that passes through it.  By comparing chemical analyses of the groundwater, we hope to identify chemical tracers indicating which rock beds have the most dissolution cavities. 

Student will collect samples of water using a bailer from each well and analyze the composition of the water using the Graphite Furnace Atomic Absorption Spectrometer to identify chemical markers that record water-rock interactions.  The calcium:magnesium ratio will be interpreted in terms of the relative degrees of interaction of the water with calcitic and dolomitic limestones. 

Student will sample the well field several times to identify changes in the chemical trends in the aquifer that might suggest changing flow paths in the limestone.

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Fracture study within the quarry – Drs. Kurt Friehauf and Sarah Tindall

Two undergraduate students involved - Autumn 2003:

Systematic mapping of the orientations and abundance of fractures in different rock formations and the relationship between folding of the rocks and rock fracture 

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The intergranular porosity of fine-grained limestones like those in eastern Pennsylvania is very low – the rock is simply quite dense and therefore does not allow much water to flow directly through the tiny spaces between mineral grains.  Most groundwater flow through limestones therefore occurs through fractures.  Due to the ready dissolution of limestone by flowing groundwater, tiny fractures and swarms of fractures can grow to become large conduits.  There are many geologic processes that cause rocks to fracture.  In the case of the limestones in eastern Pennsylvania, the main mechanisms are most likely related to faulting and folding.  Faulting by mountain-forming stresses creates fractures that may cut across bedding at almost any angle.  Folding of rocks during mountain formation can also cause rocks to fracture either along bedding planes in the limestone or at a high angle to bedding.  Alternatively, the release of pressure during erosion can cause horizontal fractures to form within the rock.  Careful measurement of the orientations and abundance of fractures and folding of the limestones exposed in the quarry will allow us to determine which processes of fracture formation dominate in the Ontelaunee area and which process formed fractures that most closely correspond to major groundwater flow paths in the area. 

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Characterization of the mineralogy and chemistry of the different limestone formations in the study area – Dr. Kurt Friehauf

Two undergraduates student involved – part of rock fracture project:

Collect systematic suite of rock samples every 5 feet across the quarry

X-ray diffraction (XRD) study of samples to get semi-quantitative estimate of relative proportions of the minerals calcite, dolomite, quartz silt, and clay by comparing characteristic peak heights of each mineral on XRD scan

X-ray fluorescence (XRF) study of samples to get quantitative analyses of Ca, Mg, Si, Al, Fe content of rocks using Evansville Cement facility (their machine is already calibrated for these types of rocks), from which we can calculate theoretical mineral proportions more precisely

Thin sections of samples will be studied to document the porosity, grain size, and fine-scale textures in each rock type

Some limestone beds may be more soluble in rainwater than others and so be more vulnerable to cave formation.  Limestone is composed of varying proportions of the minerals calcite (CaCO3), dolomite (CaMg(CO3)2), quartz (SiO2), and clay (Al2Si2O5(OH)4).  Calcite is by far the most soluble of the four, followed by dolomite, whereas quartz and clay are essentially insoluble.  The size of the mineral grains can also play a big role in determining the solubility of a rock – fine-grained rocks are generally more soluble than coarser-grained ones.  Finally, rocks that contain pores through which some water can flow allow more water-rock interaction and thus potentially more dissolution.  Rock outcrops exposed in the quarry show what appear to be dissolution channels that follow bedding, occurring only within specific rock layers.  A combined approach using XRD to characterize the minerals present, XRF to determine the chemical composition of the rocks, and analysis using petrographic microscopic will help us to evaluate the potential differences in the solubility of different limestone layers. 

The students studying mineralogical and geochemical variations in the sedimentary rocks will also be doing the rock fracture study with Dr. Tindall.  The students will sample rock as they measure fractures.  Integrating the rock fracture and the mineralogical study will allow for us to say something about the interplay between a rock’s composition and propensity to fracture.

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What makes this project so special

This project is an excellent example of how scientific research can bring together undergraduate students, several professors of differing specialty, and local industry in a collaborative effort to solve some fundamental questions. 

By selecting a large group of student participants, more students have opportunity to gain experience doing more things, while still maintaining a sense of “ownership” of their own part of the study.  Working as a group also requires students to learn to cooperate be responsible for their part of the work. 

Because the project involves such a tight collaboration with local industry, students develop connections in the field that may lead to jobs when they graduate.  In addition to Berks Products, Evansville Cement Corp. and Suburban Water Testing have both contributed to the project. 

Cooperation with local industries promotes Kutztown University as important members of the community. 

By involving multiple Kutztown professors, the project encourages faculty interactions and builds group cohesion within the department. 



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