Thames Tideway Tunnel

The Westbourne, or Kilburn, also known as the Ranelagh Sewer, is a cultivated small River Thames tributary in London, rising in Hampstead and Brondesbury Park, and which, as a drain, unites and flows southward toward Kilburn and Bayswater, west end of Paddington, to skirt underneath the east end of Hyde Park's Serpentine Lake, and then through central Chelsea under Sloane Square.

It passes centrally under the south side of the Royal Hospital Chelsea's Ranelagh Gardens before discharging into the inner London's combined sewer system, with the exception discharges into the inner London Tideway.

Since the latter 19th century, the population of its catchment has risen further, but to reduce the toll in places on the Beckton Sewage Treatment Works and related bills, its narrow basin has been assisted by private soakaways and public surface water drains.

This depression has been replaced with and adopted as a reliable route for gravity combined sewer.

The station was badly bombed during the Bombing of London in November 1940, but the pipe was not damaged.

After flowing beneath the eastern lands of the Royal Military Hospital gardens and beneath a corner of Chelsea Barracks, the drain was in all but exceptional storms entirely designed to be received by the Joseph Bazalgette-designed Northern low-level sewer.

As some of its foul content overwhelms the system with further inflows from the west, an improvement, the Thames Tideway System Tunnel, will enable that sewer to continue to cope.

A clearance in sand against the Tideway is about 300 yards west of Chelsea Bridge, an emergency combined sewer overflow, also called the Brownlee Sewer.