When there is exceptionally heavy rainfall there is a risk of flooding for many basements in homes in Hammersmith and Fulham, and Kensington and Chelsea. In the July 20th 2007 storm there were 1,700 homes flooded in the two boroughs. The water flowed down from Brent and Camden.

There has been nothing on that scale since. That amount of rain – a month’s rain in a day – is very rare. Perhaps once a decade, once a generation, once a century. We never know. But it is certainly right to seek ways to safeguard against the misery and disruption of flooding when it does occur.

Some basements are more at risk than others. Some of those flooded had faced the same problem in 2004. The good news is that if there was an equivalent downpour now around 600 of them would be protected as they have had anti flooding devices called FLIPs (flooding local improvement projects) installed. These are mini pumping stations that can help prevent sewage from entering homes through pipes and lavatories. The hi-tech devices cost around £35,000 each.

Other mitigation work has been done. One important project has been to clean out the existing sewers including the one at Counters Creek – lorry loads of sludge have been removed.

On the other hand, there are also more basements now than there were eight years ago as people as people have strived to get more space in their properties.

So it would be good to do more to deal with the flooding problem. But what? Thames Water propose a relief sewer connected to existing sewers at Counters Creek. (Counters Creek used to be a stream from Kensal Green that flowed down to the River Thames via Little Wormwood Scrubs, Stamford Bridge, Brompton Cemetery, Lots Road and Chelsea Creek. It got filled in at various stages – mostly to provide a railway.)

The proposed Thames Water scheme is staggeringly expensive – it has a price tag of £300 million. If it averted flooding of a thousand basements that would cost £300,000 a time.  As with the notorious Super Sewer project Thames Water can just pass the cost onto customers as it is a monopoly. Indeed it has a perverse incentive to spend money and thus build up its asset base.

Furthermore the Thames Water proposal would involve considerable environmental damage in various parts of the borough. Residents in Astrop Terrace and Hammersmith Grove could face 15 months of drilling through concrete (7am-7pm weekdays, 7am-1pm Saturday). That would be followed by two months of 24 hour construction work. 25 lorries everyday, reversing up Hammersmith Grove and Richford Street. In the long term the vents from the sewer would cause pollution. Sewer gas emissions are dangerous to health. Trees would be damaged.

A small but heavily used and valued park by Gwendwr Road, just north of the Talgarth Road, is threatened with the same disruption.

The public garden in Baron’s Court Road near West Kensington tube is also on the hit list. So is a site in Sulgrave Road and another by the Edward Woods Estate.

Could the £300 million be better spent?

George Warren, the Council’s Flood Risk Manager, has sent me a briefing note about one such scheme in Australia Road.

He says:

The proposals are to convert the existing road into a pedestrian and cyclist space with limited vehicular access for emergency and maintenance vehicles. It also helps provide a safer link between the Early Years Centre and the playgrounds (on opposing sides of the road).

Initial neighbourhood wide consultation with residents, businesses and councillors was undertaken in March 2013 as part of the White City Neighbourhood scheme. During this neighbourhood wide consultation, the initial idea to convert part of Australia Road into a pedestrian space was raised by Randolph Beresford Early Years Centre and supported by both Team White City and the White City Residents’ Association. Further consultation was undertaken on-site with Team White City, Randolph Beresford Early Years Centre and the White City Residents Association between March 2013 and March 2014 as the concept design for the scheme was being developed.

Public consultation regarding the concept design for the Australia Road pedestrian space was undertaken in February and March 2014. Residents responded to the consultation either during the public meeting held on 18 February 2014 at the White City Community Centre or via online and postal options.

The scheme includes the following SuDS / flood risk reduction elements:

• Permeable Paving
• Rainwater Harvesting
• Raingardens
• Bio-retention Basins
• Controlled Sewer Release

Sustainable drainage is a core aspect of the concept design. The aim is for water to be retained within the site during storm conditions and for peak discharge into the combined sewer system to be reduced during rainfall events. The retention basins are the critical features to achieve this. Permeable paving will also be used throughout the paved areas of the site. Rainwater from the school roof will be fed into a retention basin using open channels.

The design restricts runoff rates to the sewer to greenfield rates up to the 1 in 30yr ARI and reduces overall flow volumes to sewer by 50%.

Recent hydraulic modelling carried out as part of the Surface Water Management Plan (SWMP), currently out for public consultation (www.lbhf.gov.uk/swmp), shows this section of Australia Road to be a Flooding Hotspot. The implementation of SuDS here will help to address this flooding issue as well as provide amenity and biodiversity benefits.

The project will cost approximately £830,000, made up from TfL LIP Funding, Lead Local Flood Authority Funding and an additional contribution from the GLA.

Work began on site on 10th March 2015 and is due to be completed in late July 2015. Planting may occur at a later date to avoid placing plants under stress during the summer months.

That project will reduce the risk of flooding. But that is not the only benefit. It will make visiting the Early Years Centre, the adventure playground, and the community playground easier and more pleasant. It will mean more community events and a safe space for children to play and learn to ride a bike. Planting will enhance the natural environment. There will be improved air quality.

So that is costing £830,000 (Thames Water declined to chip in towards the cost incidentally). £300 million would pay for 360 such schemes. That could transform our borough. Council estates could see vast areas of concrete replaced by grass and flowers.

Yet little or no serious work seems to have been done on whether comparing the impact of SUDS schemes on such a massive scale with the relief sewer in effectiveness of reducing the risk of flooding.

The Council don’t seem to have made any estimates of the impact. At the Council meeting last night Cllr Lisa Homan, The Council’s Cabinet Member for Housing,  said the relief sewer was essential as however much was spent on SUDS it could not possibly be as effective. She said this was established by the report from the Flooding Scrutiny Task Group of 2012, which was chaired by Matt Thorley. It was an excellent report but it established nothing on the sort. It didn’t even mention the relief sewer.

Thames Water themselves haven’t been able to come up with anything so far.

An Ofwat spokesman tells me:

“It is for Thames Water to set out and decide how to meet their outcomes, and that means it is a decision for the company to set out the best and most efficient way for delivering.”

What about the Consumer Council for Water?

Their spokesman tells me:

“Essentially we don’t have the technical expertise in this area to make that kind of assessment, and it’s not part of our remit.”

Hammersmith & Fulham Council does have the power to prevent the Counters Creek scheme from going ahead.

I asked:

“Please advise if we could choose to prevent the Counters Creek Storm Relief Sewer from proceeding by denying planning permission? Or is it one of those major projects (like the Super Sewer) that we are obliged to allow?”

Ellen Whitchurch, the Council’s Head of Development Management replied:

“Thank you for your query about the Counters Creek flood alleviation sewer project. Unlike the Thames Tideway Tunnel, this project does not appear to be of a scale to be classed as a Nationally Significant Infrastructure Project (NSIP) to be considered by the Planning Inspectorate.

“Instead, there will need to be a series of planning applications submitted relating to the new sewer construction and the interceprion sites where shafts will be sunk and cabins and/or vents remain. These applications will be determined by H&F through the normal process, considering development plan policies. The Local Plan policy does support, in principle, measures to reduce flooding to properties in the borough. However, local circumstances and impacts could, in theory, result in the refusal of individual applications.

“In practice, however, Thames Water will be seeking detailed pre-application advice on individual sites once the options under consideration have been further assessed. There will also be further public consultation before apy applications are submitted. Officers would expect Thames Water to have regard to consultation response, and would not anticipate applications to be submitted where sites have generated significant grounds for objection.”

I am not convinced that the present proposal represent good value – either for money or for the environment. There needs to be some proper accountability and transparency in considering the SUDS alternative.