CALL Course on Geology: Field Trip 4

CALL Course Field Trip 4
Water: streams, lakes, oceans, and groundwater

July, 2006

Stop 1. Colyer Lake Dam

The ridge on the skyline is underlain by the Tuscarora Formation, the lower ridge by the Bald Eagle Formation, and the intervening valley by the Juniata Formation. Valleyward of the lower ridge is the Reedsville Formation. That formation is ideal for the bed of a lake, because shale has very low permeability and therefore will not leak. No outcrop is visible here, but subcrop indicates that both shale and siltstone are present. We may stop at a small quarry on Taylor Hill Road to view the Reedsville Formation.

Stop 2. Tussey Sink

Sinking Creek flows into and out of Colyer Lake. It continues into Penns Valley, sinking all the while. Another small creek comes off Tussey Ridge, flows over the Reedsville, and then disappears into Tussey Sink. This is an extensive, linear sinkhole, where water coming off the mountain goes underground. As we have said several times previously, the underground water flow in the valley is much more extensive than the above-ground water flow.

Stop 3. US322 Bypass. Bellefonte Formation and Mount Nittany

These beds of dolomite with thin interbedded shales are 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 sealevel, 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). And notice in the field that the Bellefonte does indeed dip to the northwest.

Stop 4. US322 Bypass. Salona and Coburn Formations and the intervening bentonite

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 Mt Nittany syncline.

Stop 5. 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 6. 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.