漫话英伦：伦敦的 '超级下水道'

choi

BBC Chinese, Oct 3, 2014.
www.bbc.co.uk/zhongwen/simp/brit ... n_focus_super_sewer

(2) 超级下水道 Super Sewer has an official name:
Thames Tideway Scheme
en.wikipedia.org/wiki/Thames_Tideway_Scheme
(a proposed 25 km (16 mi) tunnel running mostly under the River Thames through central London, intended to provide storage and conveyance of combined raw sewage and rainwater discharges that currently overflow into the river. On 12 September 2014, the UK Government approved the plans")

Note:
(a) There is no need to read the rest of the Wiki page. You will learn more about London sewer by reading the following entries. I did, and basically Thames Tideway Tunnel is for storage of storm waters, something Boston, Chicago and Tokyo have built, all of which use combined sewer system.
(b) The official name of the project is Thames Tideway Tunnel, as shown at the top of the table in right margin. The table also gives an URL that no longer works (www.thamestunnelconsultation.co.uk).

choi

(3)
(a) The official website of Thames Tideway Tunnel is
www.thamestidewaytunnel.co.uk/

In the top horizontal bar, the tap "The Project" offers a menu. Read them all. You will see the tunnel, for most of its course, will mostly run UNDERNEATH the river. The first sentence of "History" in the menu states, "Did you know? Sir Joseph Bazalgette’s brick sewers are made up of 318 million bricks laid by hand."

(b) London Sewers. BBC, undated (under the heading "Seven Man Made Wonders).
www.bbc.co.uk/england/sevenwonders/london/sewers_mm/index.shtml

View only the photo of brick sewer underneath London.

(c) search images.google.com with (Joseph Bazalgette’s brick sewers)--WITHOUT quotation marks--and you will see Old London used brick sewer. Didn't (doesn't) it leak: the jargon is "exfiltration." See
Robert S Amick and Edward H Burgess, Exfiltration in Sewer Systems. National Risk Management Research Laboratory, Office of Research and Development, US Environmental Protection Agency (Cincinnati), at page 1 (Order No. 8C-R551-NASX).
nepis.epa.gov/Adobe/PDF/2000E6PB.pdf

Quote: "Over the years, many of these systems have experienced major infrastructure deterioration due to inadequate preventive maintenance programs and insufficient planned system rehabilitation and replacement programs. These conditions have resulted in deteriorated pipes, manholes, and pump stations that allow sewage to exit the systems (exfiltration) and contaminate adjacent ground and surface waters, and/or enter storm sewers. Exfiltration is different from sanitary sewer overflows (SSOs). SSOs are overflows from sanitary sewer systems usually caused by infiltration and inflow (I/I) leading to surcharged pipe conditions. SSOs can be in the form of direct overflows to receiving water, street flooding, and basement flooding; whereas exfiltration is not necessarily caused by excess I/I and is merely caused by a leaking sewer from its inside to its surrounding outside.

choi

(4) Mary Gayman, A Glimpse Into London's Early Sewers, Part III. Cleaner Magazine, 1996.
www.swopnet.com/engr/londonsewers/londontext3.html        

Go to the third figure (with egg- and oval shape) to see why both shapes, as well as smooth interior clay pipe in SOME occasions, were chosen by Joseph Bazalgette (though discussion of scientific merits is insufficient in my view).