| PELA
has conducted karst investigations for environmental and engineering
purposes all over the world. PELA has also consulted extensively
on groundwater and geologic issues for quarries and mines, many
of which are located in karst areas. Only PELA combines this
specialized expertise in karst with the infrastructure and resources
of an international consulting firm with more than 40 years
of experience. The summaries that follow demonstrate some of
PELA's project experience in karst terranes. |
| During
a karst geophysical and hydrogeologic investigation at a facility
in Indiana, PELA applied an innovative approach to the collection
and analysis of natural potential (NP) data, also known as SP
(self-potential, spontaneous potential, and streaming potential).
This methodology was utilized to identify and locate zones of
vertical groundwater flow, indicative of discrete aquifer recharge
features within the epikarstic zone. Groundwater tracing was
also performed using fluorescent dyes to determine groundwater
flow routes and related hydrologic parameters. |
PELA
conducted a karst investigation in the Valley and Ridge physiographic
province of eastern Tennessee to assist with the siting of a
high-yield well to supply water for an industrial process. An
inventory of karst features was prepared, including springs
submerged beneath a reservoir. Geophysical surveys (electrical
resistivity and natural potential) and fracture-trace analyses
were also conducted. |
| PELA
is conducting a comprehensive investigation of ground stability
and highway stormwater runoff management in support of the design
of a major interstate-highway interchange on I-70 in Maryland.
The future interchange lies in an area of active sinkhole collapse.
PELA will be performing geophysical and groundwater tracing
investigations for its client and the Maryland State Highway
Administration. |
PELA
performed a hydrogeologic investigation at a large underground
limestone mine in Missouri. Dewatering projections were developed
and monitoring programs were designed and initiated based on
the results. PELA developed recommendations regarding future
limestone reserves and the tunneling necessary to connect them. |
| PELA
assisted the Kuwait Institute for Scientific Research with an
investigation of sinkhole collapses which have damaged numerous
homes in suburban Kuwait City, resulting in the evacuation of
several city blocks. PELA was requested to assist with determining
the cause of the collapses and to recommend possible remedial
methods. |
PELA
is working under a contract with the Federal Highway Administration
to conduct a fifteen-state investigation of groundwater impacts
associated with highway stormwater runoff in karst areas. A
major objective is the development of a practical, passive system
for improving the quality of highway runoff entering karst aquifers.
Field pilot studies are being conducted at project sites in
Tennessee and Maryland. |
| PELA
worked with the Arkansas Highway and Transportation Department
to protect a karst groundwater basin providing habitat for the
threatened Ozark cavefish (Amblyopsis rosae). The area was studied
in an effort to protect the cavefish from groundwater contamination
and other impacts associated with construction and highway drainage. |
PELA
performed a regional assessment of subsidence and sinkhole development
in eastern Tennessee for the U.S. Department of Energy. This
work was performed to assist in evaluating environmentally acceptable
techniques for on-site disposal of low-level radioactive wastes
in areas overlying carbonate rocks at the Oak Ridge Reservation. |
| PELA
assisted a county government in Georgia with the preparation
of a RCRA Part B permit application and the design and implementation
of a quarterly groundwater monitoring program. This permit was
for post-closure care of an inactive industrial facility on
a former military base in a karst area. |
PELA
performed hydrogeologic investigations and provided expert testimony
regarding flooding of an active limestone quarry adjacent to
a public water supply reservoir in Alabama. The project included
preparation of reserve estimates and a series of five-year plans
for mining the remaining limestone resources. |
| PELA
performed a hydrogeologic investigation for a large limestone
quarry in Georgia. A groundwater recharge program was developed
and implemented to control localized impacts associated with
prolonged groundwater withdrawal. The program was successful
and was approved by regulatory authorities. |
PELA
assisted with an evaluation of karstic groundwater flow on the
island of Guam for the closure of military facilities. |
| PELA
assisted with a team effort to develop a closure plan for a
Missouri landfill in a karst setting. Subsequently, PELA conducted
an evaluation of karstic collapse potential at an adjacent municipal
sewage treatment lagoon. The latter project included the application
of electrical resistivity and an exploratory drilling program. |
PELA
was retained to characterize geologic, hydrologic, and hydrogeologic
conditions at the site of an existing hazardous-waste landfill
and to provide testimony regarding the hydrogeologic setting
to the New York State siting board in support of a permit for
expansion of the 385-acre facility. The project involved work
in an area of complex karst hydrogeology near the Canadian border.
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| PELA
provided specialized expertise in karst hydrogeology to a study
of the Edwards Aquifer for the City of San Antonio, Texas, as
part of a multidisciplinary team addressing karst hydrogeology,
stormwater runoff, urban planning, drainage engineering, economics,
and law. The purpose of the study was to determine the limits
of development which could safely occur within the recharge
zone and drainage area of the aquifer without degradation of
the groundwater supply. PELA assisted with the development of
a water quality management plan and program for protecting the
Edwards Aquifer recharge zone. PELA has also provided expert
testimony regarding "Community Right-to-Know" issues. |
PELA
assisted with environmental investigations, development of remedial
alternatives, and technical support during litigation and arbitration
involving five PCB-contaminated sites in Indiana. Many environmental
issues were involved because the sites were located in sensitive
areas of karstic limestone. |
| PELA
performed multiphase hydrologic and hydrogeologic studies for
a major kaolin producer in Georgia. A surface water discharge
monitoring program was developed, and a wetlands evaluation
was performed. Regional aquifer analyses were also conducted
to develop water budgets and evaluate groundwater quality in
the area. PELA also prepared an NPDES permit for wastewater
discharge. |
PELA
performed a hydrogeologic assessment of a three-county area
in eastern Tennessee for the US Office of Surface Mining to
assess mining impacts on domestic groundwater supplies. |
| PELA
provided technical services and expert testimony on proposed
groundwater protection regulations for the State of Florida
and the US Environmental Protection Agency (US EPA) wellhead
protection program. |
PELA
was retained to evaluate the suitability of mine spoil material
for use as a topsoil substitute in reclaiming mined areas in
Alabama. Chemical and weathering characteristics were evaluated
to determine the most suitable vegetative cover. As a result
of this project, a variance was issued by the US Office of Surface
Mining permitting the use of spoil material in lieu of topsoil
for reclamation purposes. |
| PELA
has conducted a planning study to assist a pipeline company
in addressing karst-related hazards along a 500-mile-long corridor
in Florida. |
PELA
provided services related to the permitting of seven mines in
north-central Alabama. Work included hydrogeologic investigations
and monitoring programs, as well as preparation of mining permit
applications. Data were also collected and evaluated in support
of an NPDES permit for wastewater discharge. |
| PELA
conducted hydrogeologic investigations and groundwater modeling
and provided expert testimony regarding Consumptive Use Permits
in the Southwest Florida Water Management District. Impacts
of dewatering were modeled for three aquifers based on data
obtained from pumping tests. PELA's client received a favorable
ruling. |
PELA
performed a detailed evaluation of karst features along a natural-gas
pipeline route in Alabama. Field monitoring of active subsidence
was conducted, and pipeline installation was supervised along
an alternative route. |
| PELA
performed hydrogeologic studies at Figeh Spring, one of the
three largest springs in the world, in Damascus, Syria. The
project included evaluation of storage, discharge and recharge
potential to determine water availability during periods of
low flow. |
PELA
provided the Agency for International Development and the Government
of Egypt with a series of studies over a twelve-year period
to evaluate water reserves and assist in long-term planning
for water supply development and management. |
| PELA
performed hydrogeologic investigations for the City of Bogata,
Columbia, to assess karst development at the site of a proposed
dam and water supply reservoir. |
PELA
investigated seepage associated with a landfill in a karst area.
The State of Tennessee accepted PELA's recommendations, and
the remedial action was successful. |
|
In conjunction with other
geophysical methods and investigative techniques, PELA has
conducted and interpreted the results of electrical resistivity
tomography (ERT) surveys in karst areas with a considerable
degree of success. Several recent projects demonstrate a range
of applications.
- ERT was the primary methodology
employed to assess the ground stability characteristics
at the proposed site of the Spallation Neutron Source at
Oak Ridge National Laboratory in Tennessee. This planned
linear particle accelerator will lie in tunnels beneath
a ridge of carbonate bedrock containing sinkholes and other
karst features. This technique was used to collect data
on the nature of the bedrock surface between geotechnical
borings.
ERT was used to characterize a highly irregular bedrock
surface to plan the expansion of a limestone quarry in a
karst area of Alabama. This approach provided the aerial
coverage needed by the quarry operator to optimize future
activities without the expense of an extensive drilling
program.
ERT was used to assess ground stability characteristics
at the future site of a large manufacturing facility in
a karst area of Alabama. This method was employed to characterize
the limestone surface in the vicinity of soil voids discovered
during a geotechnical boring program. Interpretation of
the images indicated that weak zones in the soil were caused
by subsurface erosion related to buried karst features.
Further investigations and ground modifications were recommended.
ERT was applied to evaluate potential areas of sinkhole
collapse and to guide a boring program at the construction
site of a commercial development plagued by collapses in
Kentucky. In particular, the developer required data regarding
voids and potential collapse risk beneath the footprint
of a large commercial building. ERT provided the data in
a timely, cost-effective manner; and the results were confirmed
by a drilling program.
ERT was an instrumental component of an assessment of sinkhole-collapse
risk at a future waste-disposal facility in a karst area
of the Midwest. This method was applied to locate depressions
in the limestone surface, indicative of karstic solution
activity related to epikarstic groundwater flow and potential
sinkhole hazards. The findings of the geophysical survey
were supported by limited exploratory drilling.
|
PELA
routinely conducts ground-penetrating radar (GPR) surveys to
identify causes of karstic subsidence and to locate areas of
potential sinkhole collapse. Examples of recent projects include
the following.
- PELA conducted a GPR survey
along a gas pipeline route in Florida. Based on the GPR
records, the detected karst features were categorized according
to their risk levels. Karst features with great sinkhole
risk were further investigated by detailed GPR survey and
natural potential measurements to determine their sizes.
PELA conducted a GPR survey
to locate areas of potential karstic subsidence at a power
plant site near Orlando, Florida. PELA's map was used to
guide the activities of the ground improvement contractor,
who validated its accuracy.
PELA performed a GPR survey near Sylacauga, Alabama to evaluate
possible underground cavities near structures in an area
of historic subsidence.
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