This episode details my technical contribution to an urban infrastructure initiative aimed at enhancing the quality of electricity service in the town of Leones and its surrounding area, serving approximately 11,000 residents.

The project entailed the expansion of the Leones Transformer Station (ET) from 66 kV to 132 kV, the integration of a new 1x40 MVA field, and the construction of a 132 kV overhead transmission line segment.

The project was financed by provincial public funds, with a total cost of USD 1,532,248 and a completion time of 270 calendar days.

During the execution of the bored piles for the extension of the Leones Transformer Station, we faced a critical technical challenge related to the stability of the deep excavations. The piles, approximately 16 metres deep and 1.2 metres in diameter, were driven using bentonite slurry as the stabilising fluid. From a depth of 12 metres, partial failures were identified in the walls of the shafts, which caused slippage and increased the risk of collapse prior to concreting.

Through direct observation, drilling reports and mud analysis, I determined that the soil at that level had saturated fine sand strata with intercalated layers of silt, characterised by high permeability and low cohesion. This condition favoured the loss of bentonite fluid into the ground, which reduced the hydrostatic pressure within the borehole and compromised the structural integrity of the pile.

The risks were significant: loss of shaft section, reduced bearing capacity, difficulty in inserting the reinforcement and contamination of the concrete with loose material, which endangered the stability of the entire foundation system.

Faced with this situation, I proposed and coordinated a series of technical corrective measures:

• Adjusting the bentonite sludge 

I performed intensive monitoring of the sludge properties, using tools such as the Marsh Funnel, API sludge balance and Filter Press. We increased the sludge density to 1.12 g/cm³ and the viscosity to over 45 seconds per litre, improving the lateral holding capacity. We also incorporated stabilising additives to reduce fluid seepage in permeable soils.

• Controlled natural filter formation 

I established a technical pause procedure during excavation, allowing a bentonite film (cake) to form on the borehole walls, which acted as a natural waterproof barrier. This measure reduced fluid losses and stabilised the surrounding ground.

• Reinforcement of the cleaning and concreting process 

I coordinated the cleaning of the bottom of the shaft with a bailer to remove sediment and ensure proper bonding of the concrete. I established a rigorous protocol for concreting with tremie pipe, ensuring a continuous flow from the bottom of the pile upwards, which prevented segregation, air ingress and contact with residual sludge.

• Constant monitoring and quality control 

I designed a system for daily monitoring of slurry parameters before, during and after excavation. In addition, I managed the execution of PIT (Pile Integrity Test) tests to verify the structural continuity of the shaft and validate the effectiveness of the measures taken.

Thanks to these actions, it was possible to stabilise the excavations, guarantee the verticality of the piles and carry out the concreting without contamination or loss of volume. Integrity tests confirmed that all structural elements were within the expected technical tolerances, thus ensuring the reliability of the transformer station foundation.

• Plans of foundations, construction details, sections, and building.

• Calculation memorandums.

• Site photographs.

• Internal certifications.

• Management system documents.

• Site plan / Task diagram.