Traditionally, sewers carried both foul flows and storm water runoff and are known as combined sewers. However, it is now more common for sewerage systems to be separated into two independent drainage systems.

The key benefit of a separate system is that when the storm sewer becomes overloaded it does not contain foul pollution. However, where combined sewers are present, overloaded sewers discharge polluted effluent to a watercourse causing gross solids pollution and detriment to water quality.

Additionally, many thousands of properties are at risk of flooding from sewers due to ongoing development and inadequate sewerage infrastructure. As well as being a key issue for the owners and occupiers of affected properties, it is one that has important implications for sewerage undertakers and the water industry regulator, Ofwat.

Where sewer flooding, or discharge from overflows is a problem, hydraulic modelling is often used to better understand the behaviour of the drainage system. The benefits of detailed modelling are that, in many cases, the solutions can be optimised and need not involve expensive capital works. We have carried out a number of studies that have included the causes and prevention of flooding in urbanised areas, flood estimation, flood routing and detailed engineering design of storm sewerage systems.

Hydraulic and water quality modelling using InfoWorks is a key specialism offered by EPG Clear. Our expertise lies in the production of robust, fit for purpose models that are used to formulate needs and develop cost effective options. EPG Clear has extensive expertise in the following areas: