Diary of a Sutton Councillor

Wallington flash flooding

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The flooding under the railway bridge in Manor Road, Wallington has made the national news with pictures of the submerged cars and the dramatic rescue thanks to a quick thinking local man.

The reason the road dips so dramatically here is that it was lowered many years ago to allow double decker buses under the bridge. However this dip means that in severe weather all the local runoff gets directed into the dip and there were a number of occasions when significant rainfall resulted in floods under the bridge.

A major part of the 2011 improvement works involved addressing the flooding issues under the railway bridge. This involved installing four new soakaways* in Beddington Gardens, Ross Parade and Woodcote Road and improving the existing one under the bridge.

These five soakaways appeared to have addressed the problem, until Tuesday’s rainstorm.

We know that exceptional amounts of rainfall does lead to some drains being unable to cope with the volume leading to what is known as flash flooding. Apparently the rainfall this time was so torrential that elsewhere the sheer force of water gushing through the drains pushed the drain covers off, including in Stafford Road.

Sutton Council does undertake a program of gully & drain clearing – look out for a small lorry with a tube going into the drains, but I don’t know when the soakaways were last checked. As your ward councillors we will of course be finding out whether there were any issues with cleaning that may have contributed to the situation.

Update 10th June – feedback from council on gully cleaning:

Roads noted as high flood risk have a gully cleanse quarterly. The most recent gully cleanse of Manor Road from Wallington Green to the traffic lights at Sainsbury’s was on 14th April 2016.  It is on the high flood risk list so is cleaned quarterly and would be due again in July.  No issues were noted on last clean. All the other roads in the town centre were done in mid May around the 18th including Ross Road, Ross Parade, Elgin Road to the east of the town Centre and Shotfield, Parks Hill Ave and Beddington Gardens to the west.  These roads all feed down to the sewer under the bridge.

The crew use a gully tanker to suck all the silt and debris out of the gully pot, clear debris from the grill and then flush the system.  They check the gully pot is clean and working efficiently.  If they detect a blockage, they use a jet to try to remove the obstruction and get the gully and connecting drain that links it to the Thames Water main sewer running again.
If they are unable to get the system working, they note this on their report sheet.  Defects are then reported to the Highways Service so they can instruct their contractor to investigate further and make a repair.
 Update 23rd June – further work on Ross Road area drains to be undertaken
Thanks to an impromptu survey mid-rainstorm by a public spirited resident we have learnt from the council that at the last gully cleansing there were problems accessing some of the drains and gullies due to parked cars. This means that they cannot be certain that all the gullies in the Ross Road area are completely clear of blockages, and certainly the information supplied by the resident and checked on myself would suggest that there are some issues that need to be addressed and liaison with Thames Water as necessary.
To address this the council will seek to suspend parking for a day in relevant areas so that they can have a good look at the missed gullies and clean them out as necessary.
We appreciate that any suspension of parking is very inconvenient, particularly in Ross Road and surrounding streets, but it is the only way that the drain cleansing can be addressed, so when you see the parking suspension notices go up, please obey them. If people park and prevent access to the drains then it means that the crews have to keep coming back which means more days with parking suspended.

*According to Susdrain Soakaways are square or circular excavations either filled with rubble or lined with brickwork, pre-cast concrete or polyethylene rings/perforated storage structures surrounded by granular backfill. They can be grouped and linked together to drain large areas including highways. The supporting structure and backfill can be substituted by modular or geocellular units.

Soakaways are a sustainable way to provide stormwater attenuation, stormwater treatment and groundwater recharge, are installed underground and are not visible.

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June 9, 2016 - Posted by | Information | , , ,

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