Headington sewer capacity

Here are some notes from a meeting with Thames Water, following sewage spills in and around London Road and Brookside.

Pipe capacity

  • There is a 150 mm pipe down London Rd
  • This joins a 300 mm pipe in All Saints Road
  • Capacity has been checked in and around the junction of Headley Way, London Road and Brookside and this is OK.
  • If capacity were a problem then the sewer would block up daily.
  • Sewer pipes need to be fairly full as they are self-cleaning so require steady flow

Monitoring capacity

  • Growth forecast  is considered every 6 months so incremental change is spotted.
  • They have just finished plotting capacity across the City and Headington is OK. (evidence shown for this)
  • London Road sewer (incl Brookside) is on the 1 year planned maintenance list because of the frequency of incidents but the latter have all been due to a build-up of fat and grease

How to contact Thames Water

Thames Water enquiry number is 0800 316 9800 to report drainage issues

Responsibility for sewers

Thames Water look after shared sewers. As soon as a sewer leaves your land then Thames Water looks after it

  • If a sewer pipe runs past no. 1, 3, 5, 7 then the owner of no. 1 is responsible for sorting out problems with the pipe inside his/her curtilage but when it gets to no. 3 and thereafter it’s the responsibility of TW
  • If unsure whose responsibility it is, ring Thames Water enquiry number

Causes of sewer blockage

Fat and grease clings to non-biodegradable wipes – these are everywhere now, not just baby wipes but surface wipes, make-up wipes etc

New technology to detect blockage

Echo system technology is newly available – don’t have to dig up major roads to put cameras down from now on, can send down an echo finder and get a reading from that

Further action agreed

  • TW to send posters/leaflets/.pdf link to Cllrs to promote what can and can’t go down sinks/toilets
  • TW to establish whether promotion dept is working with Oxford Brookes and Headington School
  • Cllrs to contact Thames Water if we think street traders are pouring grease into the sewers

Latest news on Brookside spillage

We have received another bulletin from Thames Water regarding sewer capacity in Brookside and dated yesterday. It reads as follows:

I am pleased to confirm our Technical Specialist has assessed the footage from the recent clean of the sewers in London Road and Brookside. He has confirmed that the sections of sewer which have been cleaned are now free-flowing and fully operational. 

There is a final section of the foul sewer in London Road which we now need to clean and camera survey to ensure the sewer is operating at full capacity. This has been scheduled for 4 October. 

Further to our discussion about sewer size in the area, our Asset Management team have confirmed that they recently completed a catchment wide hydraulic modelling study using flow monitors. This did show a degree of hydraulic incapacity in the London Road – Brookside area but our Sewer Flooding History Database shows the last flooding caused by hydraulic overload was in 2010. 

All of the recent flooding incidents have been caused by blockages of fat and grease, so there is insufficient history of a capacity issue to justify further studies or a network upgrades at this time. They have also confirmed that increasing the size of the sewers is not the right solution for sewer flooding relating to blockages as even with a larger size sewer, blockages will still occur.

Once the clean of the sewer in London Road has been completed I will ask the local Field Operations Specialist to consider placing the sewer in London Road and Brookside on our Planned Maintenance programme. This will mean they are cleaned regularly to prevent flooding caused by blockages from happening.       

I hope this information is useful, I will continue to monitor our progress and will contact you with a further update by 7 October to confirm the final section of sewer was cleaned as planned.

Thames Water – further response re Brookside sewer

Here is our latest update sent to us this morning.

I am writing to update you further to my email of 4 August.

Our team attempted to clean the sewer in Brookside on 8 August but were unable to completely clear it of fat and grease. As a result, our Technical Specialist reviewed all the work we had completed so far and extended the scope of the clean to include a section of the foul sewer in London Road.

I am pleased to confirm that the first section of this new clean was completed on 16 and 17 August. Our team removed large amounts of fat and scale from the sewer and left it free flowing. The final section of the clean has been planned for 24 August. Once all sections have been cleaned and surveyed, the footage will be assessed again by our Technical Specialist to decide if further work is needed. I will contact you with a further update by 5 September.

Pollution fears by residents justified

The Brookside sewage spills were very upsetting for residents, and there were also fears about pollution to Boundary Brook.

We have received the following report from the senior case manager at Thames Water and will publish follow-up correspondence.

Dear Councillor Wilkinson

Thank you for highlighting the repeated external sewer flooding suffered by residents of Brookside. Sewer flooding is always a terrible experience and I fully appreciate residents’ desire for a solution to be put in place given the repeated nature of the problems and the pollution caused as a result.

I would like to reassure you that our investigations into the cause of the flooding are ongoing but our initial findings have not identified a lack of capacity in the sewers. The recent flooding incidents have all been caused by blockages of paper and toilet wipes, rather than hydraulic overload. Hydraulic overload is where the flows in the sewers are higher than they are designed to cope with and usually occurs after heavy rainfall. 

I understand from your email that other residents in Brookside have experienced flooding which they have not reported to us. It is really important that they do report any flooding as soon as possible to our 24 hour Customer Contact Centre on 0800 316 9800. This allows us to investigate and help them as soon as possible and also allows us to build a full history of issues in Brookside, which our operational team then use to justify further investigations or improvements.    

Our operational team have been working hard to identify and resolve the root cause of the blockages. If there is a defect or obstruction in the pipe this would cause items to catch and lead to flows backing up and causing the floods. Our engineer’s inspection of Boundary Brook on 13 July confirmed that floodwater had entered the highways drainage and then into the Brook causing a pollution. As a result he arranged for a full clean and camera survey of the 150mm foul water sewer in Brookside to be completed to check for any obstructions or defects in the line. When our engineer revisited Boundary Brook on 16 July he confirmed that the pollution has stopped but also arranged for our team to complete a clean-up of the Brook on 18 July.     

Our camera team completed the clean and camera survey of the foul sewer in Brookside on 19 July. They cleared scale and debris from the line and left the pipe free-flowing and fully operational. The footage will be shortly viewed by one of our technical specialists to determine if further work is required. I will contact you with the results of the review by 4 August.