Caves contain
significant resources related to biology, geology, hydrology,
archeology, paleontology, recreation, and scenery. Cave
environments, by their very nature, provide unique, closed systems
that are valuable for scientific study and environmental education of
underground resources and the interrelationship between surface and
subsurface. Potential hazards to cave/karst resources and
surrounding communities may result from the following natural gas
activities:
- Contaminants
such as lost drilling fluids as well as hydrocarbons from spills or
leaks (including floods) from well casings, storage tanks, reserve
pits, pipelines, and production facilities that may enter into the
cave/karst systems;
- Cements
escaping into voids which may restrict groundwater flow and introduce
pollutants;
- Vented or
escaped gases, collecting in sinkholes and caves. These gases can
cause a die-off of plant and animal life that use the special habitat
created by the microclimate of the cave entrances or sinkhole. Some
cave systems in the Greenbrier Valley extend for miles under
thousands of acres below homes, building and towns. An explosion
touched off by cavers with carbide lamps or other source of ignition
could result in major loss of life and property. There is not
only a explosion hazard but also an aphyxiation hazard to the lucky
homeowner, business owner, customer or caver;
- Increased soil
erosion from gas development activities (i.e., well pads, roads,
etc); and
- Corrosion of
the casing strings.
Caves are "known" openings in
the limestone that have a person sized connection to the surface so
they can be entered and explored. In karst areas, for every
"known" cave there could be literally hundreds or thousands
more - number, feet, miles - of "unknown" passage that has
no connection to the surface or has not been discovered. Water
well drillers have hit as many as eight voids on their way through
the karst. So when gas drilling companies say they will stay away
from "known" caves they are whistling in the dark.
When asked about drilling through
karst, gas drillers tend to respond like its the same as hitting an
abandoned mine passage - they say they just keep drilling and then
double case the void so it is sealed and then continue drilling below
it. In karst - and in WV - there are MANY cave passages that
are over 50 ft in height - and MANY over 100 ft.......the
largest underground continuous vertical drop in WV is 350 ft in a
cave in Pendleton County. So one question is how do you
drill and case something over 30-40 ft in height? Another is
how do you drill and case through 8 successive voids.
Another difficulty in drilling through
a karst void that increases the likelihood of problems with casing
integrity is that the bottom of the cave often consists of large
boulders making it extremely difficult to begin drilling in a spot
that is directly under the hole entering the void, resulting in a
casing that is not straight.
The integrity of the casing is vital in
preventing leaks, and minor flaws may not become an issue until time
has passed. Because natural gas has no odor until it is added, there
would be no warning of a buildup of gas in a karst area. Some may
argue the gas will stay fuel rich (non-flammable)underground due to
lack of oxygen or displacement of air from the cave. Caves have
air the same as the surface - and they breath - suck in when high
pressure weather system moves through the area and blow out when
lower pressures weather system moves through the area. High
entrances tend to suck air and lower entrances blow air during summer
due to bouyancy effects. In summer, "cold" cave air
is heavier and flows out lower entrances - causing a slight negative
pressure in the cave which causes upper entrances to suck air in to
replace that which flows out the lower entrances. In
winter the process reverses - now warm cave air is lighter than
outside air and pours out upper entrances, the lower entrances then
pull in surface air to replace. So caves are always exchanging
air with surface - bringing fresh air with oxygen to make flammable
mixture. Also any gas in the cave will be pulled out and to the
surface with the cave air exchanged making it more likely to find an
ignition source - a passing car, tractor, lightning........someone
lighting a cigarette in their living room.