Blacklion Wastewater Treatment Plant Upgrade

The scope

This project involved an upgrade to Blacklion wastewater treatment plant in County Cavan. Phase 1 of the project took place between March and September 2021, involving a detailed design stage including stakeholder workshops and HAZOP/ALM process. Phase 2 construction stage was from December 2021 to June 2022. 

The work

Conway Engineering assumed the roles of designer, contractor, PSCS and PSDP for this design and build with all the duties and responsibilities that entails. We designed each element of the upgrade – civil, structural, process, mechanical, electrical, and ICA telemetry. We produced detailed design submissions for the employer’s representative for review and we project managed design workshops and the HAZOP/ALM process with all stakeholders.

We also coordinated with Cavan County Council staff operatives to maintain plant operational and compliant during the upgrade works. 

Upgrading Blacklion WwTP comprised construction and commissioning of inlet works channel with manual bypass bar screen and access platform, a storm overflow chamber with flow regulator hydroslide, a storm pumping station including civil, mechanical and electrical works. The project also included building and commissioning a precast concrete storm tank with flow return pumping station and storm tank cleaning system, and a RAS/ WAS pumping station including civil, mechanical and electrical works. 

We upgraded the existing sludge drying reed beds (SDRBs) measuring 283m2 including distribution and collection pipework to deliver equal sludge loadings to all sections of the reed bed, maximising dewatering capability of the process. These were built using cast in-situ concrete base with precast concrete retaining walls due to site constraints. Vegetation planting took place as specified by Uisce Éireann. We installed a French drain along the rear of new SDRBs for surface water runoff and a filtrate pumping station to return filtrate to the head of the works. As part of this project, Conway Engineering also provided ancillary civil works including access road, hardstanding, ducting, plinths, pipework below ground.