Applying the HPT-GWS System for Evaluation of Managed Recharge in Unconsolidated Aquifers

Tuesday, December 5, 2017: 11:00 a.m.
102 B (Music City Center)
Wes McCall, PG , Direct Image, Geoprobe Systems, Salina, KS
Thomas Christy, PE , Direct Image, Geoprobe Systems, Salina, KS
Mateus Evald, Intern , Geological Engineering, Federal University of Pelotas, Pelotas, Brazil

A modified HPT probe has been designed with multiple injection ports that also may function as sampling ports. This probe is called the Hydraulic Profiling Tool-Ground Water Sampler. Field testing of the HPT-GWS was conducted in an alluvial aquifer system in central Kansas, at depths approaching 30m. The injection pressure logs were monitored to define the hydrostratigraphy and determine permeable zones in the formation where groundwater could be successfully sampled. Water quality parameters were monitored to stability prior to sampling. Changes in water quality parameters versus depth were observed and used to guide selection of depth intervals for sampling major element cations/anions as well as arsenic, barium and uranium.

During field work, subtle variations in the EC log across the coarse-grained aquifer were observed where the corrected HPT pressure log was flat. A strong relation also was observed between groundwater specific conductance and bulk formation EC in the coarse-grained aquifer facies. Modeling of field data found that the DP EC logs follow Archie’s Law in the aquifer facies even at the relatively low dissolved ion concentrations observed. Negative EC anomalies were observed where fresh water recharge was occurring below local storm water retention basins. Conversely, positive EC anomalies were observed where brine from the underlying shale bedrock was impacting the water at the base of the aquifer. These results demonstrate that the HPT-GWS can be used to define formation hydrostratigraphy at the centimeter-scale and sample for contaminants at multiple depths (profiling) in unconsolidated, permeable formations. The system also could be used to effectively assess seawater/brine impact and evaluate sites for placement of aquifer recharge basins or wells. Additionaly, the logs and profile samples may be useful in assessing the changes in groundwater geochemistry and extent of artificial recharge in unconsolidated aquifers.


Slides in PDF
Wes McCall, PG, Direct Image, Geoprobe Systems, Salina, KS
Mr. McCall has an M.S. in Geology and is a licensed geologist (KS28). He has managed investigations using direct push technology for over 25 years. Mr. McCall joined Geoprobe in 1995 where he conducts applications research related to groundwater, environmental and geotechnical investigations. He is active in the ASTM D18 Subcommittee on direct push technology where he has assisted in development of several standards. Wes has been involved with application of the MiHPT system to evaluate performance of the system to delineate formation permeability and contaminant distribution. He recently published the results of a field study about application of the HPT-Groundwater Profiling system.

Thomas Christy, PE, Direct Image, Geoprobe Systems, Salina, KS
Mr. Christy graduated with a B.S. in Civil Engineering from the University of Missouri-Rolla in 1980. Mr. Christy’s career has focused on soil and groundwater site characterization. In 1987, Mr. Christy, along with his partner, Melvin Kejr, formed Geoprobe Systems; a company dedicated to the development and manufacture of subsurface investigation equipment. Mr. Christy has designed numerous soil probing tools for vapor, soil core, and groundwater sampling. He participates in the Geoprobe research and development team and is responsible for probe deployed soil and contaminant sensors developed by the company. He has authored several technical papers and holds patents for sampling and sensing devices. Mr. Christy is a registered professional engineer in the state of Kansas.

Mateus Evald, Intern, Geological Engineering, Federal University of Pelotas, Pelotas, Brazil
Mr. Evald is an undergraduate senior in Geological Engineering at the Federal University of Pelotas, Brazil. He was an intern for Geoprobe Systems in 2015 where he assisted in field work and analysis of the data acquired with the HPT-Groundwater Profiling system. He currently works with research about the benefits and advantages of the use of High Resolution Site Characterization Methods, specifically the MiHPT system, in comparison with traditional methods that are used in Brazil.

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