- Water
- 15 Aug 2025
Client: Scottish Water (CWA)
Duration: September 2022- July 2025
Situation
As part of the Caledonia Water Alliance (CWA), a joint venture between AECOM and M Group Water, we’ve been supporting Scottish Water to increase sewer network capacity and storage within the Marchmont area of Edinburgh, reducing the risk of flooding to businesses and residents.
For several years, persistent flooding has impacted businesses and residents due to a lack of capacity in the existing sewer network and increase in frequency and intensity of heavy rainfall events.
Task
We constructed a 20m internal diameter, 15m deep attenuation storm tank using underpinning methods creating 3000m3 of storage, housing a Vacflush™ column from CSO Group.
This involved installing 600m of upsized sewer along Marchmont Crescent, connecting to the existing network at Meadow Place.
Storm flows spill into a bifurcation chamber on Marchmont Road and the new 20m diameter, 3000m3 offline storm storage tank in Bruntsfield Links.
The new storm tank will be able to hold around 3.5 million litres of storm water, minimizing future storm events. Additional work included two duty/standby pumps, 600m of new sewer, and 24 PCC manholes to a depth of 4.5m.
Action
Storm Tank Construction
The new storm tank was constructed under the Bruntsfield Links to reduce the risk of internal and external sewer flooding in the Marchmont area. CWA hit a huge milestone in March 2024, when the roof of the storm tank was lowered into place. The roof is made up from reinforced concrete beams and slabs, and weighs over 400 tonnes, covering the 20m wide by 15m deep tank.
Collaboration with the Public and Other Utilities
We’ve maintained access for nearby properties and businesses, influencing the construction schedule and traffic management.
Close collaboration with utility providers was necessary due to excavation near their assets, requiring vibration monitoring and method adjustments. Residents were regularly informed, and a public information event was held in Meadows Park before work began. Noise levels were communicated weekly, and condition surveys were conducted for residents.
Together with Scottish Water, we launched a water ‘top-up-tap’ in Meadows Park to reduce single-use plastics, supporting Scotland’s Net Zero Targets
Due to the extensive works being carried out, traffic management was put in place to ensure the safety of customers and residents. Throughout the road closures, CWA has ensured that local business remain open. To further minimise the impact to residents and business, all work is being conducted in short phases.
Results
We’ve successfully introduced trenchless methods to preserve mature trees, complying with City of Edinburgh Council requirements.
The pipe specification was changed from 900mm ductile iron to 900mm Aquaspira, a composite steel-reinforced pipe that is over 7.5 times lighter, allowing for easier installation.
Significant carbon savings were achieved with Ground-penetrating radar (GPR) pipe installation, weighing only 10% of the traditional concrete pipes.
From the outset of the project, it was agreed that the site would be restored as a wildflower meadow upon completion. In 2015, experts from Brechin-based Scotia Seeds, the University of Edinburgh, and the Scottish Wildlife Trust collaborated to develop a bespoke wildflower seed mix tailored for urban pollinators, particularly bees, which require consistent food sources throughout the summer months. To ensure its effectiveness, the mix was trialled on several sites, including a smaller existing meadow adjacent to the new site.
