KENTUCKY KARST
are thus common in the area (Johnson, 1966; Miller, 1967). The Grier Member of the Lexington Limestone formation consists of nodular and fossiliferous argillaceous limestone, with irregular to rubbly and lenticular bedding: interbeds of thin medium-dark-gray shale are found in portions of the unit. The rock acts as a confining bed hydrologically in local areas, and is mostly impermeable (Black, 1965; Johnson, 1966; Miller, 1967).
Average annual rainfall in Kentucky ranges from 107-132 cm (42-52 in) (Kentucky Mesonet, 2019). In the two days pre- ceding the dye injection, it rained 9.17 cm (3.61 in). Thus, this study was conducted during high-flow conditions.
The objective of this dye trace was to measure conduit-flow more accurately than traditional dye trace methods and to test the efficacy of the Cyclops 7 infrared probe (herein referred to as “probe”).
Methodology
Company-supplied directions were followed and the probe was calibrated accurately using titration prior to this study. Background data were collected at McConnell Springs and Campbell House on June 17th and June 18th, 2019 to ensure no background dye existed in the system prior to the dye trace. A “Dye-Trace Notification” permit was submitted to the Kentucky Division of Water on June 17, 2019.
To power on the probe, one side was unscrewed and turned to the “record” position. The probe was then installed at the McConnell Spring “Blue Hole,” which is the location where dye from the Campbell House injection site first appeared at the surface (per the Norris et al. 2016 study). The distance from the Campbell House sinkhole to McConnell Springs is 1.93 km or 1.2 miles (refer to Figure 2).
One gallon of liquid fluorescein dye was deployed into the flooded Campbell House sinkhole on June 18th, 2019, at 11:15am (Figure 3).
Figure 3 - Flooded Campbell House Sinkhole. This sinkhole often dries out completely between major rain events.
A higher-than-average amount of dye was added due to flood conditions and the possibility of dilution. Following the injection, data were collected primarily using the probe instead of traditional methods (‘traditional’ meaning activated char- coal dye receptors [CDRs] and water “grab samples” using 8 ml borosilicate glass sample vials – See Norris et al., 2016), though these sampling techniques were used as backups. Precautionary measures (such as gloves and transporting dye separate from the probe and other materials) were used to ensure that there was no dye contamination. Temperature collection on the probe was also set to one-minute intervals.
Results and Discussion
As noted in the introduction, in the two days preceding the injection, Fayette County received 3.61 inches of rain (Kentucky Mesonet, 2019), which is well above the 0.148 in (0.376 cm) daily average for June in Lexington. Discharge recordings at the nearby USGS Wolf Run Gauging Station were consistently above the mean for the year (12 cf/s), peaking up to 873 cf/s on June 18, 2019 the night before the injection (Figure 4). Discharge at the time of injec- tion (11:45am on 6/18/19) was 85.7 cf/s. The excess rainfall occurring before and during sampling, thus facilitated rapid movement of dye through the system.
Figure 4 - Discharge at Wolf Run gauging station over the study period.
Dye appeared at McConnell Springs at 3 hours post-injection and increased to 600ppb at 3.75 hours on June 18th, regressed, then again peaked at its highest value of just over 1,200ppb on June 19th before gradually decreasing to background levels over the next two days (Figure 5). Comparison of Figures 4 and 5 suggests that there is a correlation between discharge and dye concentra- tions due to flushing of the karst system,
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