Pumping and Treating a Large Volume of Water to Enable the Development of the West Midlands Interchange

Project Summary

The proposed works involve the dewatering and treatment of water pooled in various lagoons across the quarry site. A previous report concluded that the water in the lagoons is primarily rainwater, with minimal groundwater inflow. It was determined that a volume of 150,000 m³ needs to be pumped to designated discharge points to dewater the lagoons and allow the client to commence the construction phase.

Dewatering Strategy

PDL designed pumping and treatment systems that comply with the limitations set by the relevant environmental permits. Two discharge points were established, each permitted to handle a flow rate of 30 l/s. The water quality at these discharge points had to meet specific pH and Total Suspended Solids (TSS) ranges. To achieve this, PDL proposed surface-mounted diesel pumps at four lagoons. Each pump and its associated pipework can discharge more than 30 l/s. As the water level in the lagoon drops significantly and the pump can no longer maintain the 30 l/s rate, another pump will be activated at a different lagoon to compensate. Before discharge, the water is treated for pH and TSS content. Two large Water Treatment Systems (WTS) were designed to manage the flow rate while ensuring the treated water meets the standards of the environmental permit. The treated water is then gravity-fed to the final outfall point. Regular pH and turbidity spot readings are conducted and documented, supported by real-time telemetry. Additionally, water samples are analysed by laboratories to ensure compliance with the environmental permit. A dewatering supervisor was appointed by PDL to oversee this operation on-site, with support from PDL project managers in the office.

Outcome

This project is still ongoing but has already achieved success thanks to extensive preparation and problem-solving by PDL, as well as close cooperation with the principal contractor. We will continue to provide the best possible service to ensure the project is completed while remaining compliant with both flow rate and water quality standards.