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PROJECT

Geophysical Survey, Bedrock Mapping and Water Table Level Detection Services in Ireland

Client
> Veolia Water Ireland – Luimeagh Water Treatment Plan

Sector/Market
> Natural Environment

Services
> Subsurface Surveys, Geophysical Surveys

Location
> Limerick, Ireland

Project summary

Murphy Geospatial was commissioned by Veolia Water Ireland to carry out a geophysical survey at the Luimneagh Water Treatment Plant.

To achieve this, a combination of Seismic Refraction and Electrical Resistivity Tomography (ERT) was employed.

The survey was conducted in coordination with Murphy Geospatial’s Digital Engineering department, ensuring continuous data integration. Final deliverables included AutoCAD drawings, and a technical report whose findings are all validated against geotechnical borehole data. The results confirmed high accuracy in geological layer depth and water strike detection, supporting future planning and development of the site.

The brief

Murphy Geospatial was tasked to conduct a geophysical survey, combining Seismic Refraction and Electrical Resistivity Tomography (ERT). The objectives of the investigation were:

  • To characterise the subsurface material present at the site.
  • To assess the depth to bedrock, where possible
  • To evaluate the depth of the water table
  • To confirm the absence of karst features

The challenges

The main challenge was the presence, of a buried treated water storage tank located near one of the survey lines, whose influence was clearly visible in the resistivity section. However, as mentioned in the next sections, results from the seismic refraction survey helped resolve this issue.

Figure 1 - Proximity to the water tank induces a low resistivity zone.

Our work

The geophysical survey was carried out with Murphy Geospatial’s Digital Engineering department, ensuring continuous integration of spatial data across disciplines.

The geophysical component followed standard procedures, with surveyors adhering strictly to the Health, Safety, Environment, and Quality (HSEQ) protocols mandated by the client. This ensured that all work was conducted safely, efficiently, and in full compliance with site-specific regulations.

Figure 2 - Surveyor in full PPE, complying with on-site HSEQ rules

The dataset from this acquisition was processed in our Kilcullen office.

After data processing, the seismic, ERT and geological interpretation sections were compiled and delivered in AutoCAD format. The geophysical dataset was also documented in a dedicated technical report. The results were then cross-referenced with findings from the geotechnical investigations to validate the accuracy and reliability of the geophysical interpretations.

Results

No karstic features were detected on site, and borehole data confirmed that the depths of the geological layers were determined with an accuracy of approximately 0.5 metres.

Most notably, borehole data also provided information on the water strike depth, which closely matched the interpretation derived from the seismic refraction inversion sections. This correlation was particularly important, as ERT data on some lines was affected by the proximity of a buried water tank.

Figure 3 - Interpretation of line 1. The cyan rectangles highlight borehole data points, which closely align with the geophysical interpretation.
Figure 4 - Interpretation of Line 2. The cyan rectangles also highlight borehole data points, which closely align with the geophysical interpretation.
Figure 5 - On top: Seismic refraction section of Line 1 overlaid with isoresistivity contours. The delineated features correspond closely with those identified in the seismic inversion, highlighting the consistency between datasets. At the bottom: Isovelocity contours from the seismic refraction inversion of the same line. The cyan rectangles highlight borehole locations: green indicates dry boreholes, while blue marks the water strike levels. The water strikes observed in both BH01 and BH02 align closely with the depth range inferred from the seismic refraction data-specifically, between the yellow and green isovelocity contours.
Figure 6 - Seismic refraction inversion section and corresponding isovelocity contours for Line 2. The dry borehole at BH04 aligns precisely with the observed drop in isovelocity at the center of both sections.

The results confirmed high accuracy in geological layer depth and water strike detection, supporting future planning and development at the site.

Contact

For more information on this project, please email info@murphygs.ie or call us on +353 (0)45 484 040