Project Overview

DP Basal Wells are required to depressurize the in-pit mine area prior to advancement of mining activities. The water from the DP wells has levels of hydrogen sulphide that needs to be treated prior to water being discharged to the onsite ponds. The original design had some safety, operability, maintainability, and reliability issues. In addition, the measurement and control system was unable to meet the performance requirements for the project.
Rally was asked to review and redesign the 3rd party system for the 2nd generation of these mobile water treatment plants, and modify the design as required to ensure all known issues were addressed. The 2019 mine plan required that the modular water treatment plants be deployed to six well sites, resulting in the project delivering 44 skids.

Basal DP Wells main Basal DP Wells first Basal DP Wells second

Process Engineering / Instrumentation

The original 3rd party vendor’s design did not meet the performance specifications associated in treating the H2S concentrations in the water. Rally conducted a technical review of the process design and issued a findings report to the client identifying the necessary changes to ensure the performance of the skids, that formed the basis for the 2nd generation water treatment design.
The system was developed using a highly specialized probe capable of measuring dissolved H2S in water that been developed for use in open water systems, and not intended for inline pressure piping systems. After consultation with many vendors, it was determined that there were no other alternatives capable of obtaining the necessary measurements. Rally redesigned the system using the original probes installed in a fast-loop arrangement which allowed measurements to be taken in a low flow system which was not exposed to the pressures in the rest of the reaction zone area. This redesign of the probe system enabled accurate measurements to be taken which enabled the automation of the peroxide dosing system.


The project schedule for construction of the wells was highly aggressive to meet the client stakeholder requirements.
Detail engineering of the new system began in March of 2019, allowing eight months for detail engineering, procurement of vendor equipment and bulk materials, modular fabrication, and onsite construction.
To meet the in-service dates, Rally developed an aggressive schedule for the commissioning and start-up of the water treatment systems. To accomplish the aggressive schedule Rally successfully employed the following techniques:

  • An integrated team was formed between the Owner, Rally Engineering, and the Constructor. A combined engineering / procurement and construction schedule was maintained throughout the project.
  • Constant management of equipment and bulk material delivery requirements were a focus of the project team. Engineering planning was executed to ensure delivery dates for the project could be met.
  • A robust weekly status reporting program was implemented to ensure that the client always understood the requirements of the project from a cost, schedule, and projects needs perspective and able to react in a timely fashion.
  • By having an integrated team including the constructor at the onset of the project, the project was able to design the project with consideration for constructability. This significantly lessened the amount of RFIs and construction inquiries after engineering packages were issued for construction (IFC).
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