Hogsmill Sewage Clean-up
According to Blogger statistics, one of the most-read posts of 2016 to date has been The Hogsmill Sewage Spill (8.2.16). It therefore seems appropriate to provide an update here, rather than respond individually to the many enquiries received. This also serves as a useful way of maintaining a chronological record of events, while keeping ward councillors informed, particularly as they are already dealing with other sewage-related issues, such as persistent odour problems.
The previous post detailed the amount of 'rag' that appears downstream of the outfall on an almost weekly basis. During the flood of 25 June 2016, however, a substantial quantity of this material—including nappy liners, sanitary towels, condoms and their wrappers, cotton buds and, despite assurances that it does not survive passage through the Hogsmill Storm Relief (HSR) outfall, toilet paper—was deposited across the adjacent Public Open Space (POS).
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| Rag at the outfall |
So, here's what happened on Thursday and Friday, 30 June and 1 July 2016. A professional team from Adler & Allan, based in Tunbridge Wells, was brought in to clean up the outfall, together with the accumulated 'rag' and sewage-related debris along the Hogsmill as far as Villiers Road.
According to the company's website, Adler & Allan began trading as a coal merchant in London. Through the acquisition of related businesses, it has grown into a national environmental services company, providing major spill response and hazardous waste management for organisations including Thames Water and the Environment Agency.
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| Operatives from Adler and Allan |
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| Toilet paper (E. Newton) |
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| Rag at Ewell Storm Tanks (P Harwood.) |
So why are these spills occurring much more frequently? Data from overflows show that the 'emergency' mechanisms for retaining sewage during times of excess rainfall, are inadequate.
These are known as the storm tanks and are located further upstream at Ewell Court and at the Hogsmill Sewage Works (HSW). The HSW storm tanks overflowed into the river twice during May 2016, on 5 May and again on 30 May.
What was once a mechanism designed to protect the Hogsmill during extreme weather events now serves to inundate the river with a tide of untreated sewage, killing fish and creating a hazardous environment for those working alongside and within the river. This is of particular concern to those constructing in-channel river improvements and volunteers involved in the Riverfly Monitoring Initiative (see side tabs).
During these overflow events, sewage has overtopped the storm tanks, bypassing the screening processes that are intended to prevent 'rag' from entering the river.
In addition to the persistent problem of misconnections—with sediments, sewage and chemical run-off evident at outfalls along the Hogsmill—there is also evidence of sewage overtopping the river bank from the works and flowing directly into the Hogsmill. The result is a toxic cocktail, detectable both by our basic monitoring equipment and, all too often, by our noses.
These are known as the storm tanks and are located further upstream at Ewell Court and at the Hogsmill Sewage Works (HSW). The HSW storm tanks overflowed into the river twice during May 2016, on 5 May and again on 30 May.
What was once a mechanism designed to protect the Hogsmill during extreme weather events now serves to inundate the river with a tide of untreated sewage, killing fish and creating a hazardous environment for those working alongside and within the river. This is of particular concern to those constructing in-channel river improvements and volunteers involved in the Riverfly Monitoring Initiative (see side tabs).
During these overflow events, sewage has overtopped the storm tanks, bypassing the screening processes that are intended to prevent 'rag' from entering the river.
In addition to the persistent problem of misconnections—with sediments, sewage and chemical run-off evident at outfalls along the Hogsmill—there is also evidence of sewage overtopping the river bank from the works and flowing directly into the Hogsmill. The result is a toxic cocktail, detectable both by our basic monitoring equipment and, all too often, by our noses.
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Misconnection Villiers Road Channel Of Cess
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| Pumping out cess |
So why has this situation arisen and what can be done to restore the river quality? The aspirations of the council to develop more and more of our open space see 'Direction of Travel' document will not help this situation. It is also not fair to be expecting our POS's to take more and more these operational impacts (see Fishponds). Kingston’s “Direction of Travel” (on local growth and
development) consultation is available for comment till 29th August at http://consult.kingston.gov.uk/portal/planning/direction_of_travel
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