Geosciences Home | OLLI Course Home

OLLI Course on Geology and  Environmental Geology of the State College Area
Field Trip: Karst, carbonates, and constant headlines: all our problems DO NOT sink (pun intended) out of sight: hydrogeology of the Nittany Valley

Stop 1.  US322 Bypass.  Bellefonte Formation (dolomite) and Mount Nittany

     These beds of dolomite with thin interbedded shales comprise the Bellefonte Formation.  The dolomite-shale sequences are cycles recording sea level rise and fall.  A trained geologist can tell driving by at 60 mph that it is a dolomite and not a limestone by its yellow-brown to tan color on a weathered surface, as opposed to the grey of a limestone.  Also, fine-scale fracturing is more common in brittle dolomites than in less-brittle limestones. 
     Within the Bellefonte Formation is a 10-15 ft member called the Dale Summit Sandstone, a beach deposit.  It represents a more drastic change in sea level, during which the shoreline moved from somewhere in Wisconsin to Pennsylvania and then back again.
     Mount Nittany syncline can be viewed here also.  The ridge is asymmetric because

the beds on the two sides of the ridge do not dip at the same angle.  Note the position of the Bellefonte (Obf). 

 Stop 2.  US322 Bypass.  Salona and Coburn Formations (limestone), the intervening bentonite, and some karst features

     Both the Salona and Coburn (both within the Ocn in the figure) consist of limestone beds overlain by calcite-rich shale beds in cycle after cycle.  These cycles represent sea level rise and fall.  In the Salona the cycles range from 1-4 ft thick, whereas in the overlying Coburn the cycles are about 1 ft thick.  The Salona contains fossils, but fewer than in the Nealmont below it.  The Salona formed in subtidal conditions, whereas the Salona formed, overall, nearer the shoreline.  Together, these formations are representative of the warm, shallow sea that covered the continent between the Grenville and Taconian orogenies.
     There is a prominent bentonite layer at the contact of the two formations.  Bentonite is a swelling clay that, when present in large quantities, is mined for drilling mud.  It forms from altered volcanic glassy ash.  Here that glass blew westward from volcanoes in a chain of islands offshore to the east.  Bentonite is the first sign of the coming Taconian orogeny, which made its presence fully felt with the arrival of muds of the Reedsville Formation.  There are actually a number of bentonites within the Salona and Coburn that can be correlated over several states.
     Both formations dip to the southeast, because they sit on the northern flank of the Mount Nittany syncline.

 STOP 3.  Radio Park Elementary School.  Big Hollow

     Behind Radio Park are large blocks, which may or may not be outcrop, of Stonehenge limestone.  Darker-colored bedding layers are considerably disrupted, probably by burrowing marine worms.  A variety of fossil fragments can be seen.
     Just to the south is Big Hollow, which extends to the west and to the east.  It runs through the Armory on Fox Hollow Road, an area that contains Penn State’s well field.  Big Hollow is a zone of concentrated fractures along which considerable volumes of groundwater flow.  Note that there is no stream, ever, in this topographic low.  All water movement is underground.  But pollutants that might reach this feature, such as from the old State College municipal dump to the north, would travel quickly also, and groundwater is not easy to clean up.  Small sinkholes develop within Big Hollow, some of which are visible.  The cartoon below is applicable to Big Hollow.

 STOP 4.  Big Hollow again, near the Armory on Fox Hollow Road

     The main Penn State well field is nearby, drilled into the fractured rocks of Big Hollow.  The former Centre County Fire School was a few hundred yards to the west, along the macadam road.  It was discovered that a drycleaning solvent had penetrated the soil there.  Fortunately, it had not worked its way down to the water table, but threatened the well field.  The soil was completely excavated and taken to a secure land fill in Ohio.

 STOP 5.  A recent sinkhole on Slab Cabin Run

     A new sinkhole problem occurs almost monthly in the State College area.  This hole began to emerge in October 2006 on the bank of Slab Cabin Run, directly under the Mount Nittany Expressway.  Water entering the sinkhole could potentially have reached the water table and polluted 3 Penn State wells and a College Township well, all of which are downstream.  It was remediated in January by damming Slab Cabin Run long enough for repairs to be made.

 Stop 6.  Centre County Kepone Superfund Site

http://www.epa.gov/reg3hwmd/super/sites/PAD000436261/index.htm

The Nease Chemical Co. manufactured the pesticides mirex and kepone from 1959 to 1974.  Wastes were collected onsite in unlined lagoons so that the sludge could be collected and disposed of at roughly 10 year intervals.  Fish kill in Spring Creek and discovery of kepone in fatty fish tissue alerted the company that pesticides from the lagoons had leaked down to the water table.  Actually, we now know, they sink through groundwater to reside in the bedrock, because the pesticides are denser than water (DNAPLs).  The company then lined the lagoons with concrete or asphalt.  In these basins, lime was added to the wastewater, and the "treated" water was then sprayed on open fields at the southern end of the site, a procedure that only served to contaminate the soil. And the lined lagoons probably continued to leak.
     In 1982 the EPA proposed to add the site to the National Priorities List (Superfund).  Preliminary work was performed to haul away contaminated soil from a ditch near the Benner Pike, and the pond sludges were taken to a secure landfill in Ohio.
     In 1988 Ruetgers-Nease agreed to perform a Remedial Investigation/Feasibility Study with EPA oversight.  Evaluation of sediments, surface water, ground water, air, and fish tissue was completed in 1994.  A public meeting in 1995 resulted in a Record of Decision, and a work plan was Court approved in January 1996. 
     The geology of the site consists of colluvium over carbonate bedrock that strikes parallel to the local ridges (parallel to Benner Pike).  Ground water flows quite rapidly through the karst bedrock, picking up mirex, kepone, and VOCs (volatile organic compounds) from sunken DNAPLs and issuing into Spring Creek at several points, including Thornton Spring.  Mirex and kepone are not easily degraded, adhere to sediment, and are concentrated up the food chain.  They were detected at levels above EPA standards in waters, sediments, and fish.  A catch-and-release protocol was ordered for Spring Creek.  Today levels in Spring Creek have dropped at present to acceptable standards, and the order has been rescinded.
     Ruetgers-Nease, although no longer operating here, is presently pumping groundwater and treating it.  They have installed wells upstream to intercept ground water flow under the site, where the water picks up kepone from DNAPLs.  They are cleaning VOCs from contaminated soil with soil vapor extraction.

 Stop 7.  Thornton Spring (near the Sheetz on College Avenue)

     Contours in the diagram above are elevations on the water table.  Groundwater flow is perpendicular to these contours and from high numbers to lower numbers.  Groundwater coming from the south and entering the eastern part of the Superfund site will travel north or northwest and go under the ridge north of Rte 26 and end up in Spring Creek.  Groundwater entering the site farther to the west will all be turned to the west and issue from Thornton Spring.  The Spring in fact was a major outlet for entrance of kepone, mirex, and VOCs from the Nease site into Spring Creek.  Several years ago the spring had a distinct “organic” smell from the VOCs.  Today those odors are undetectable.
     The spring is also testament that Spring Creek is in fact fed by springs.  Much of the creek bed sits above the water table and so “leaks” downward.  But it is replenished by springs along its course.