Providing the Standard for Excellence in the Groundwater Tracing Industry Since 1973

Fluorescent Tracer Dye Specialists in Water and Land Use Investigations

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Cave Springs Area Karst Resource Conservation Study


The OUL was a partner with Crafton Tull Associates (CTA) and Wright Water Engineers (WWE) in developing a science-based workable strategy for the implementation of six federal and state highway projects and for the ongoing development of the Cave Springs Recharge Area in Northwest Arkansas while protecting the largest known population of the Ozark Cavefish, a federally-listed threatened species.  The OUL led the data development component of the project, worked with WWE to develop karst-based best management practices (BMPs) based on a vulnerability assessment of the recharge area, and assisted CTA with the implementation of the BMP strategy.  More information is available at

The OUL led the effort to compile and assess existing data on the hydrology, geology, biology, and land use in the Cave Springs area, performed scientific studies to fill data gaps, and developed a vulnerability assessment and hazard assessment to identify lands most vulnerable to future water quality degradation.

Dye Tracing in Groundwater Remediation Studies

The OUL has worked for numerous confidential clients on site assessment and groundwater remediation projects that need to use groundwater tracing approaches.  Tracer dyes are commonly introduced as a slug immediately before introducing a remediation agent.  The dye identifies the points to which the remediation agent should move if it has not been consumed by the contaminants.  Fluorescent tracer dyes are also used to determine groundwater travel rates, discharge points, intercepting wells, and zones of influence.  They are very useful in verifying the credibility of groundwater models for waste sites and for demonstrating that constructed monitoring wells are actually monitoring waters derived from potential contamination sources.  The OUL routinely assists in designing tracer tests, recommending dye types and quantities, providing tracer dyes and activated carbon samplers, and conducting quantitative dye analysis of both activated carbon samplers and water samples.

Dye Tracing Investigations for the Mining Industry

The OUL has extensive experience in groundwater tracing investigations at current and former mine sites throughout North America with some projects in South America, Australia, Indonesia, and Africa.  A number of projects have involved using fluorescent tracer dyes to address acid mine drainage issues.  We have used tracer dyes to identify leakage zones from several tailings impoundments and help in their characterization.  We have conducted groundwater traces from recently formed sinkholes to open pit limestone quarries a mile or more away.  The OUL has done tracing to identify groundwater supplies likely to be impacted by proposed waste rock dumps or other mine activities and to help plan mine drainage.  In addition, the OUL has done tracing associated with unanticipated increases in water inflow rates into underground mines.

Groundwater Tracing to Assess Leaky Impoundments and Dams

The OUL has done a number of confidential tracing projects associated with leakage from impoundments or through earthfill dams.  A key factor that can be determine with tracer dyes is the travel time for water from the reservoir to a leakage point on the downstream face of the dam.  Very rapid travel times potentially indicate appreciable soil piping and a substantial risk of catastrophic failure of the structure.  Results from OUL traces have been critical in designing remediation for leaking impoundments and dams.  The OUL typically conducts field work, designs tracer studies, and conduct the analytical work to detect and quantify dye concentrations.

Recharge Area Delineations for Karst Aquatic Species of Concern

The OUL has worked with the U.S. Fish and Wildlife Service, Missouri Department of Conservation, Arkansas Natural Heritage Commission, and The Nature Conservancy and other state agencies in Missouri, Arkansas, Oklahoma, Illinois, Tennessee, Alabama, and Alaska to develop over 50 recharge area delineations and vulnerability assessments for the protection of karst aquatic species of concern including, but not limited to, the following:

Ozark Cavefish

Hine’s Emerald Dragonfly

Grotto Sculpin

Hell Creek Cave Crayfish (Hell Creek Cave Natural Area)

Foushee Cavesnail (Foushee Cave Natural Area)

Tumbling Creek Cavesnail (Tumbling Creek Cave)

Groundwater tracing with fluorescent tracer dyes was used to determine the areas that contribute water to caves, springs, and fens that have been identified as habitat for threatened or endangered species.  In addition, many of the studies included a hazard mapping and vulnerability assessment component.  Land uses with the potential for causing water quality degradation were identified in these studies.  Geologic, hydrologic, biologic, land use and other pertinent data were compiled and assessed.  These data were used to create vulnerability classifications for lands within the delineated recharge areas.  These vulnerability maps have been used by local, state, and federal agencies to aid in planning and zoning issues, highway construction, and land and water conservation efforts while protecting water quality and karst resources.

Barton Springs Edwards Aquifer Conservation District and City of Austin, Texas

For over 20 years (1996 to 2016 and continuing) the OUL has worked with these two entities on groundwater tracing studies in the Barton Springs segment of the Edwards Aquifer and in some adjacent areas.  This is a critically important source of drinking water for this portion of central Texas.  The OUL has conducted essentially all of the dye analysis work and has assisted (especially in the early years) in designing traces and sampling strategies.  Sampling reliance has been based primarily on activated carbon samplers with grab samples of water to measure dye concentrations at specific times.  The tracing work has provided an excellent characterization of this portion of the Edwards Aquifer and has resulted in essential data for land management decisions in this urbanizing area.  Tracer dyes have been detected in at least 22 wells (including some municipal water supply wells) and in Barton Springs and associated springs.  Straight line travel distances have been up to 16 miles with travel rates of as much as 4 miles per day through this karst aquifer.

One unique investigation used tracer dyes as surrogates for potential accidental highway or railroad spills into the Barton Springs Segment of the Edwards AquiferRead more about this project here.

Dye Tracing Investigations at Military Facilities

The OUL has been involved in a wide range of groundwater tracing projects at military facilities.  Many of these have been involved with hazardous waste sites in limestone terrain where one of the key questions is identifying off-site properties that may be affected.  In some cases extensive groundwater tracing programs have been needed for sites undergoing BRAC (Base Realignment and Closure).  The OUL has typically been responsible for tracer test design and dye analysis; we have sometimes been involved in dye introductions and sometimes routine sampling at complex sites.

The OUL has also been involved in dye tracing at some military facilities under the Operational Range Assessment Program (ORAP) as well as extensive involvement in dye analysis for investigation and remediation projects at military installations across the U.S.

Interstate 69 – Evansville to Indianapolis – Karst Feature and Groundwater Flow Investigation

The OUL led the karst studies investigation for the I-69 corridor in the area around Bloomington, Indiana.  The study focused on characterizing karst features and related groundwater flow paths relevant to Section 5 of the new highway and identifying caves, springs, sinkholes, and other karst features that could be impacted by construction and use of the new interstate highway.  The protection of karst species of concern as well as maintaining groundwater quality and quantity were primary concerns.  The OUL has worked with the Indiana Department of Transportation (INDOT), the Indiana Department of Natural Resources (IDNR), the Indiana Department of Environmental Management (IDEM), and the U.S. Fish and Wildlife Service (USFWS) as well as local officials and stakeholders to identify and manage karst features that will be affected by construction in the highway corridor of this new interstate highway.

Assessing Cross Connection of Storm and Sanitary Sewers and the Integrity of Sewer Lines

The OUL has designed and conducted hundreds of traces from waste lines to storm sewers, springs, surface streams, and marine waters.  This has included work at large industrial facilities, city sewer systems, and military facilities.  The use of tracer dyes is an excellent way to address these issues.  The OUL typically assists in the design of the tracer studies, provides dyes and special sampling equipment, and conducts all analytical work.

Northwest Arkansas Regional Airport – Airport Site Evaluation Study and Airport Access Corridor Study

The OUL performed two studies relating to the Northwest Arkansas Regional Airport.  The first study, completed in 1992, involved the delineation of groundwater recharge basins at two potential sites for the airport.  The second study, completed in 2001, involved investigations for the potential for adverse groundwater impacts along six alternative highway corridors connecting to the airport. Cave Springs and the karst-related fauna associated with this groundwater system were the most significant considerations in this study.

Hydrogeologic Mapping of Unincorporated Greene County, Missouri

In 1980, the OUL completed the hydrogeologic mapping of unincorporated Greene County, Missouri.  In response to the rapid development around Springfield, the OUL created a series of maps to guide planners in development in unincorporated Greene County, Missouri.  The mapping project was concerned with two major hydrologic problems in Greene County:  1) sinkhole flooding and 2) groundwater contamination. Maps created as part of the study included the following:

  • Sinkhole flooding hazards
  • Lineaments, fracture trends and faults
  • Generalized soil suitability for septic tank absorption fields
  • Important water supply areas
  • Water quality contamination hazards

These maps are used as a tool not only for local planning agencies, but also as a resource to attract developers to the area.  Information developed in this study has been in routine use by Greene County for over 35 years.

Hydrogeologic Evaluation to Support Nutrient Groundwater Pathway Delineation at Silver Springs, Marion County, Florida

The OUL was a key team member in this study for the St. Johns River Water Management District to determine the dominant groundwater pathways and travel times between specific location and Silver Springs, one of Florida’s largest spring complexes and the headwaters of the Silver River. The results of the study are being used as an important tool for federal, state and local agencies to refine and improve water management plans and develop TMDLs. It is also being used to assess the effectiveness of existing best management practices within watersheds, springsheds, and targeted restoration focus areas related to matters such as agriculture, storm water management, land use planning, and others.

Landfill Groundwater Monitoring in a Karst Environment

The OUL was a critical member of a team to evaluate the monitorability of an orphan municipal landfill located in a well-developed karst landscape in Tennessee. This old landfill created extensive and continuing off-site contamination. The OUL worked with a local consulting company and jointly did an extensive groundwater tracing program and other geotechnical work. The work demonstrated to the state regulatory agency that the site could be effectively monitored; this was a critical hurdle. A permit was granted to expand the landfill by accepting new wastes. Under the permit these wastes were combined with wastes excavated from the previous landfill and the mixture was then placed in a new landfill that met all regulations. This strategy provided an income stream for both rehabilitating the previous landfill and creating a new landfill needed in the area. Read more about this project here.

1572 Aley Lane        |        Protem, Missouri 65733        |        Phone  417-785-4289        |        FAX  417-785-4290

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