Abstract
Samples of cave water were analyzed for volatile
organic compounds during four separate storm events. The
major compounds detected were toluene, 1,1,1-trichloroethane, trans-1,2-dichloroethylene, methylene chloride, and
1,1-dichloroethane. Minor compounds detected were trichloroethylene, tetrachloroethylene, 1,1-dichloroethylene,
and ethylbenzene. These compounds were detected in varying
amounts at each of the three study sites. During a storm
event, the levels of each contaminant changed significantly
at all three sites studied. Two effects were observed when
a storm event occurred. The first effect was the dilution
of the volatile organic compounds during the storm event.
These effects were related to the amount of rainfall and the
rate at which the rainfall occurred during a given storm
event. The second effect was the drastic increase in the
level of all contaminants after the storm event.
Introduction
Bowling Green, Kentucky, is located in a karst region.
Karst areas are best characterized by numerous sinkholes,
infrequent surface streams, and an extensive connecting
network of subsurface streams flowing through solutionally
enlarged conduits in the underlying bedrock. These areas
are of interest because of their extreme sensitivity to
contamination and pollution. Any compound capable of being
leached from the soil or transported by storm water runoff
into sinking streams and sinkholes may eventually
contaminate the underlying drainage system. Upon entering
the subsurface network of streams, compounds can travel
several miles in a few hours. Contamination problems are
especially dangerous when they involve volatile toxic and
explosive compounds. Not only are these compounds toxic to
aquatic life and a threat to water supplies, but upon.
vaporizing they may become concentrated in the cave air and
rise through cracks and openings in the limestone and enter
homes on the surface.
Explosive and toxic fumes are not a new problem for the Bowling Green area. As early as 1969, gasoline fumes were reported in the basements of several homes. Again, in the spring of 1981, the same homes had to be evacuated because gasoline fumes had reached explosive levels in their basements. Gasoline fumes rising from underlying caves have been a reported problem from homes on Riverwood Street, Chestnut Street, Nashville Road, and other areas. Bowling Green has an estimated 1000 buried gasoline tanks. The leakage of these tanks is believed to be the major source of the gasoline fumes in the cave system. Gasoline from a leak may travel in a few hours several miles on the surface of an underground stream, filling the cave passages with fumes. Homes built over sinkholes, water wells, storm-water drainage wells, basement drains, and natural cave openings are all susceptible to rising fumes.
In 1981, an underground explosion in the sewer system of Louisville, Kentucky, travelled along the sewer system for eleven blocks causing much damage. Studies performed by Dr. Nick Crawford, professor of geology and geography at Western Kentucky University, indicated high readings on a combustion meter for two storm-water drainage wells in the Fairview Plaza Shopping Center parking lot. Therefore, a similar underground explosion in the caves under Bowling Green is probably remote but certainly possible (Crawford, 1984).
In addition to gasoline fumes, toxic fumes are a problem. In the fall of 1982, the Kentucky Division of water detected benzene, a carcinogen, and methylene chloride, a suspected carcinogen, in the Lost River. The total organic compound concentration was measured on May 1983 by the U.S. Environmental Protection Agency using a portable organic vapor analyzer. The concentration of the vapors were as high as 15 parts per million (ppm). In September 1982, the problem was also reported by cave explorers (Elliot, 1973) who encountered a very strong "paint thinner- or "kerosene" odor and observed a red and gray scum on the water at several locations in the cave. The fumes are still bad in the cave at times, and few people have gone into the cave since the fall of 1982. It appears that these volatile organic compounds are vaporizing in the 14.70 oC cave atmosphere. Exposure to these compounds poses a potential health threat. A major source of these compounds is believed to be a small spring south of Bowling Green which flows into the Keith Pond. The pond overflows into a sinkhole, and the contaminated water flows into the Lost River and subsequently under Bowling Green. Dye traces performed by Dr. Nick Crawford for the U.S. Environmental Protection Agency, Emergency Response Team, have shown that dye injected into the ground above the buried tanks of a nearby chemical company flows to Keith Pond. The company removed its storage tanks during the spring of 1983 and was ordered by the Environmental Protection Agency to remove the chemicals from the contaminated soil which surrounds the tanks. Future rains may leach contaminants from the soil at the site down into the cave streams. Because of numerous complaints of fumes in the Forest Park area starting in December 1983, the U.S. Environmental Protection Agency, Emergency Response Team, began their investigation. Because the preliminary results indicated the presence of toxic compounds such as toluene, xylene, aliphatic hydrocarbons, alkyl benzenes and possibly methylene chloride, a health investigation in cooperation with the U.S. Centers for Disease Control was made the first priority. Air samples from 125 homes, urine samples from residents, and other air samples from basements were analyzed. To this date, the results of this study have not been published.
Spills, leaks, and sometimes deliberate dumpings of
toxic and explosive chemicals likely occur frequently in a
city as large as Bowling Green. For example, within the
past two years three significant spills from underground
tanks have occurred. Two of the three involved gasoline or
diesel fuel. Four thousand gallons of gasoline and six
thousand gallons of diesel fuel are known to have entered
the Lost River drainage under the city (Crawfrod, 1982).
Unlike most areas, karst regions such as Bowling Green
allow chemical spills to quickly sink into the underground
streams. The flow of these compounds through underground
passages result in the formation of concentrated vapors
which may rise through the soil and enter homes on the
surface. The rise of the cave water level during a storm
event displaces floating chemicals upward and upstream. As
the water level drops, a deposit is left on the cave walls
and ceilings, and in small stagnant pools above the stream
level. These conditions were verified by Dr. Nick Crawford,
who ventured into the cave to take water samples following
the flood of August 30, 1982. Analysis of these samples
indicated the presence of benzene and methylene chloride
mixed with diesel fuel. Floating chemicals trapped against
the cave ceiling at the point where the cave passage becomes
water-filled are believed to be a major source of the fumes
which are rising into homes.
The components of the fumes and of water samples have
been shown to contain toluene, methylene chloride, and
xylene as well as a wide range of other organic compounds.
Chlorinated industrial solvents have also been detected.
These solvents include 1,1,1-trichloroethane, trans-1,2-dichloroethylene, 1,2-dichloroethane, and trichloroethylene
all exhibiting a wide range of biological effects
ranging from toxicity to carcinogenicity (Kirshen, 1984).
Water quality should be a major concern of all
residents of all geographical areas. Chemical spills, leaks
from storage tanks, and dumping of toxic and explosive
chemicals have become a serious water pollution problem.
Constant water testing should be performed screening the
water for organic chemicals.
Karst regions are extremely vulnerable to all types of
pollution. Since the spring of 1983, the city of Bowling
Green has had to address the problem of toxic, explosive
fumes and chemicals in the groundwater. Crawford's (1982, 1984)
past studies have shown a direct link between observed
deposits of chemicals in the cave and fumes on the surface.
The possible health threat to residents in all areas of
Bowling Green is very serious and obvious. Other ground-
water contamination studies (Dowty et al., 1975, McCann et al., 1975) in other areas have shown
compounds in the water supply similar to those found in the
cave water of the Lost River. To this date, there are very
few reports of karst area problems with respect to ground-
water contamination.
The problem of toxic and explosive fumes is presently
being studied by the EPA Emergency Response Team, the
Kentucky Department of Environmental Protection, and city
agencies. Hopefully it will be solved before the cave
atmosphere is accidentally ignited. The health risks of
long-term exposure to fumes originating in the cave
atmosphere are certainly serious, and residents in those
areas deserve the full attention of state and federal
agencies.
2. Vapor pressure from aqueous phase. Assume the organics exist only in aqueous phase. Calculate cave vapor pressure for maximum concentrations found in solution at Keith Pond. Use Kh vs. temperature equations of Bissonet et al. (manuscript) from the table of Hc values.
3. Compare both results to permissable exposure levels (PELs).
Study Sites
Figures:
Three sites were chosen for study because of their
location in the Lost River drainage. The first site, Keith
Pond, is located approximately 2 1/2 miles south of Bowling
Green on Highway 31W. It is a site that is directly
downstream of a 1983 chemical company spill and leak (Crawford, 1982).
At this pond site the water rises to the surface, flows for
a short distance (ca. 50 meters), and reenters the
subsurface drainage. The second site, the Lost River Blue
Hole, is also located a short distance off the Nashville
Road and is a rising stream where the water can be easily
sampled. This site was chosen in order to measure the
contribution of Keith Pond as a source of volatile
contaminants. The last site, Lost River Rise, is located a
short distance off Highway 231 North in Lampkin Park and is
the final rising for the Lost River drainage system. At
this site contaminant levels can be measured after the
stream has flowed under Bowling Green. All three sites are
strategic in that they are accessible and allow the rising
cave water to be sampled with a minimum loss of volatile
organic compounds.
Results
At each of the three sites, storm events resulted in a
significant change in the concentrations of volatile organic
compounds present in the Lost River cave water. Depending
upon the amount of rainfall and the rate at which that
rainfall occurred, two responses were observed for the
levels of volatile organic compounds in the cave-water. In
storm event one (SE-1), 2.14 inches of rain fell over a
period of three days . At Keith Pond toluene,
1,1,1-trichloroethane, and trans-1,2-dichloroethylene were
the primary pollutants (Figure - Contamination of VOCs at Keith Pond, part 1). The toluene concentration
was initially 0.5 ppm and during the storm event rose
to a level of approximately 10.0 ppm. The concentration of
1,1,1-trichloroethane and trans-1,2-dichloroethylene
increased several fold during the same time, rising from a
baseline level of 1.0 and 2.0 ppm to a maximum level of 4.0
and 5.0 ppm, respectively. Minor contaminants responded
similarly during the same storm event at the same site
(Figure - Contamination of VOCs at Keith Pond part 2
). These secondary compounds, 1,1-dichloroethane,
1,1-dichloroethylene, triIchloroethylene, tetrachloroethane,
and tetrachloroethylene, increased by a factor of 2 or 3.
At the Blue Hole a similar group of organic compounds were
detected (Figure -Contamination of VOCs at the Blue Hole). Toluene and 1,1,1-trichloroethane
increased from sub-detectable levels to 0.1 and 0.3 ppm
respectively. It was also observed that the compounds in
he cave water at this site were very dependant on the amount
of rain fall. Four separate rainfalls occurred during this storm period,
and there were four different increase in the concentrations of toluene
and 1,1,1-trichloroethene.
Discussion
The study results have shown that Keith Pond is a site
which contributes a substantial portion of organic
contaminants to the cave water in the Lost River drainage
system. Specifically, toluene, 1,1,1-trichloroethane, and
trans-1,2-dichloroethylene were found to be the major
contaminants at all three sites studied. In the case of
Keith Pond, several other minor contaminants were detected
during each storm event. Trichloroethylene, 1,1-dichloroethane,
1,1-, and methylene chloride were also detected at various times at the Lost River Rise,
indicating the presence of numerous sporadic sources of
organic compounds along the Lost River drainage system.
More specifically, the Multi-Chem Company spill and leak in
1983 upstream of the pond appears to be a major source of
toluene, 1,1,1-trichloroethane, and trans-1,2-dichloro-
ethylene. Also, this research has revealed that the
occurrence of a storm event significantly effects the level
of all of the volatile organic compounds in the cave water.
Since the Multi-Chem Company site was the likely source
of several volatile organic compounds detected in this
investigation, future studies at this site are of paramount
importance. The clay soil plays a significant role in the
retention of these organic compounds. Future researchers
should include investigations of the ability of different
soil types within this karst region to retain volatile
organic compounds and the ability of soil cave
microorganisms to metabolically change the chemical
composition of the cave water.References
Study Problems
1. Vapor Pressure from NAPL (non-aqueous phase liquids). Assume that the organic compounds detected at Keith Pond accumulate as separate phases. Calculate the vapor pressure of each compound in cave air (assuming equilibrium is maintained) at 15oC. Use equation 4-17 and 4-18 from Schwarzenbach et al. (1993) Environmental Organic Chemistry.