Sustainable Drainage Solutions for Hounslow Schools

In 2021, the London Borough of Hounslow secured funding from Thames Water as part of the Thames Water Strategic Partnership (TWSP). This five-year initiative aims to improve surface water management and sewer capacity through Sustainable Drainage Systems (SuDS). As part of this, Metis was tasked with enhancing surface water management and sewer capacity for two schools in Hounslow: The Green School for Girls, Isleworth, and The Smallberry Green Primary School, Isleworth. 

The Challenge

We were tasked with conducting a feasibility study, designing the SuDS features and overseeing the construction phase.  The challenge was to design a resilient solution that would reduce the risk of flooding and alleviate sewer capacity for many decades to come while minimising disruption to the school day. 

Additionally, we were required to carry out a cost estimate for maintenance at an early stage to assure the schools that the tasks would be feasible and comparable to their existing drainage maintenance regime. 

The Solution

Feasibility approach 

As part of our feasibility approach, we conducted CCTV Drainage Surveys to ascertain the depths and locations of the sewers, to determine the feasibility of disconnecting and attenuating runoff from the sewers. 

Our experience and expertise in accessing external funding, enabled us to support Hounslow in identifying third party funding opportunities to contribute towards the overall SuDS in School cost. This led to  the Department for Education (DfE) providing funds on the basis that the project would bring about flood risk improvements to local schools. Greater London Authority (GLA) also contributed to the completion of some of the SuDS features. 

Detailed design 

Our detailed design aimed to free up sewer capacity and improve the local area’s resilience to flooding. To achieve this, we incorporated our feasibility study findings into our designs and InfoDrainage modelling. 

We acquired topographic and utility surveys to assess whether ground levels were suitable for SuDS implementation and to verify the absence of below-ground interferences, such as telecoms. 

We carried out ground investigations to assess the feasibility of infiltration at each scheme’s location. This was conducted in accordance with Thames Water’s scoring criteria. Disconnecting surface water from Thames Water’s sewer systems would free up sewer capacity and enhance local resilience to flooding – the more sewer capacity created, the higher the score. 

We provided an estimate for the SuDS maintenance tasks using Metis’ Commuted Sums tool. This estimate was based on comprehensive information from CIRIA’s SuDS Manual and the dimensions of the specific SuDS feature to be delivered. 

Project management

Our experience in delivering similar schemes with Thames Water funding, coupled with our broader expertise in implementing SuDS enabled us to successfully manage the project from inception to completion.   

The use of project management software allowed us to effectively track the project in terms of time, budget, and quality. 

Our strong partnership with the London Borough of Hounslow and the seamless collaboration among all stakeholders: Thames Water, Department for Education, Greater London Authority, various Council service delivery teams, surveyors, and contractors led to the projects’ sustained success. 

The Outcome

The project facilitated the sustainable management of surface water and produced additional benefits, including the improvement of water quality, enrichment of local biodiversity and habitat creation, and the enhancement of aesthetics and functionality in local educational spaces.  In addition, it contributed to the delivery of two raingardens and twenty-five planters to absorb water, as well as filter polluting particulates across two schools.  

The work was completed ahead of schedule and well within budget and we were able to achieve third party funding to contribute to the successful delivery of SuDS in these Schools. 

As a result, the London Borough of Hounslow expressed interest in collaborating once again with Metis to deliver more surface water management improvement works across the Borough.

PROJECT STATUS:  Started in November 2021, Completed in October 2023.

Want to learn more about our work? Check out some other Metis case studies.

Get in Touch

Our team of experts are ready to work with you to design and manage the implementation of your next SuDS project.  If you’re interested in partnering with us, please click here to contact us.