Tideway cuts spills by 86% and prevents 84 tonnes of litter entering the Thames

(by Karma Loveday)

The first annual Tideway benefits report showed storm overflows to the tidal Thames were reduced by 86% compared to the pre-tunnel period (based on modelled volumes).

According to the the first full-year assessment of the environmental benefits delivered by the tunnel during its commissioning phase, there were concrete improvements across all four core objectives of London’s super sewer: reducing sewage discharges, improving water quality, lowering sewage-derived litter and minimising days associated to elevated health risks for river users.

Annual storm overflow volumes fell to just under 3m cubic metres in 2025, compared to a pre-Tideway average of more than 21m cubic metres. Meanwhile, during 2025, an estimated 84 tonnes of sewage-derived litter, including wet wipes, sanitary products and plastics, were prevented from entering the Thames. The report also found river users should feel more confident spending time on the waterway, with days of elevated health risk linked to sewage overflows reduced from 75.7% to 10.4%.

• Earlier this month, Tideway’s financing arm, Bazalgette Finance, successfully issued a £250m 6.625% fixed rate Blue Bond, maturing in 2036. This was its second Blue Bond issuance – a subset of Green Bonds, where proceeds are used to finance expenditure supporting marine and freshwater resources. Bazalgette Finance became the first corporate issuer of a sterling Blue Bond in July 2025. Lloyds, which supported the new issuance, said it attracted strong demand, with peak orders exceeding £875m. The proceeds will be used to refinance existing debt raised to construct the 25-kilometre Tideway Tunnel.