Agenda and minutes

There were no apologies.

RESOLVED

Cllr D Watson was CONFIRMED as the Chairman of the Little Marlow Sewage Treatment Works Liaison Committee.

Minutes for the meeting held 24^th May 2017

Minutes of the 24 May 2017 meeting were circulated for information only.

Present from Thames Water were Ms R Followell-Mattin, Customer Stakeholder Manager (operations), Mr D Collyer, Local Government Lead, Mr A Scott, Regional Operations Manager.

Copies of emails from Thames Water to the Chairman regarding the recent equipment failure had been circulated to attendees. A copy of these emails would be appended to these minutes.

Mr Collyer gave a presentation.

• Overview of day to day operations:
• Little Marlow was an activated sludge plant making use of a super bacteria that eat away at the organic material breaking solids down into sludge. Mr Collyer recommended the recent BBC documentary The Secret Life of Waste, available on BBC i-Player for information.
• The site had 4 bespoke flat-bottomed final settlement tanks (FST) custom built for the site circa 2006. Each tank was 6,300 square metres, the equivalent of 2.5 Olympic sized swimming pools. They utilised a central column with a slewing ring and siphons to recirculate the sludge.
• The FST were designed to separate the sewage that passed through them into effluent and sludge. The sludge and the beneficial bacteria stayed in the FST while effluent flowed over the top of the tank where it was monitored and passed back into the water course.
• Some other sites had a tertiary treatment but FST was the final stage of treatment at the Little Marlow site.

Overview of the recent failure at the plant:

• Following a catastrophic mechanical failure of its assembly unit 1 of the 4 FST needed to be taken out of commission. The tanks slewing ring could not turn, consequently solids could not be separated out and the effluent discharging from that tank into the water course would include solid waste.
• Once out of commission the FST needed to be drained, cleaned, and scaffolded. The broken pieces of the equipment needed to be removed by crane to be taken off site for examination.
• The necessary parts were found to be beyond repair and a new custom part needed to be fabricated to the original designs, work was to be carried out by same company who originally built the tanks. The replacement parts were expected to be on site by 19 April 2021 after which installation and testing would be carried out before removing scaffolding etc and return the FST to full use.
• Initially the remaining 3 FST were used to manage all incoming sewage. The site was able to manage a peak flow of 1,000 litres per second. To prevent the remaining tanks from becoming overloaded during peak times the decision was taken to utilise storm tanks normally only brought online during heavy rain fall. Stored discharge was then fully treated during quieter times.
• The Environment Agency (EA) were made aware of actions being taken as they took place. Had no action been taken there would have been a large discharge of solid waste, both from the broken tank and the functioning tanks during periods of excess flow, depriving the water course of oxygen over a large area and resulting  ...  view the full minutes text for item 4.

Present from the Environment Agency (EA) were Mr A Valentine, Senior Investment Manager, and Ms L Bee, Environment Management Team Leader.

Mr Valentine and Ms Bee gave an overview from the EA perspective:

• Mr Valentine had visited the site on March 2021. The EA believed there had been a breach of the site permit and this would be investigated.
• Initial concerns had been around the potential scale of the issue linked to the site size, Little Marlow was in the top ten largest treatment sites in the area, and has a history of past issues. However, it was acknowledged this had been a single catastrophic event unlike previous issues where the site had experienced multiple problems over an extended period. The use of storm drains was acknowledged as not ideal but had allowed for overflow effluent to be monitored.
• Thames Water had shared their monitoring data and the EA had carried out their own downstream monitoring 4-5 times since the event. They had also installed 2 real time monitors that could be viewed remotely. There had been low ammonia levels recorded, a good indicator of pollutants, and no impact on dissolved oxygen levels. A small amount of sewage fungus had been seen over a small area but overall, there had been no serious impact from pollution.
• The EA would be asking Thames Water to review the level of redundancy at the site and to review their position on having critical spares readily available.
• The EA would be circulating their own email briefing shortly which they would share with local groups they had previously been in correspondence with.
• The EA pollution hotline remained open for reporting 0800 807060 for all issues not just Little Marlow.

The following points were discussed as a result of questions asked by attendees:

• Thames Water were expected to do everything they could to comply with their environmental permits which were descriptive not prescriptive. This included reviewing and updating their environmental permit to ensure it adequately covered local growth.
• The EA did not have the regulatory rights to insist on a specific level of redundancy or to make their own inspections of equipment. There would be a phased roll out of new environmental permit regulations for management system conditioning meaning the EA could take a more in-depth look at site management. If the EA felt that a permit holder was not operating within their permit, notices could be issued outlining specific steps that must be taken.
• This was felt to be right approach as the EA were responsible for overseeing many different areas of business and it was the site operators who were the subject matter experts for their area. Mr Valentine felt it was in the providers best interest to comply.
• The burden on commuter towns had increased with approximately 3m less commuters traveling into London.  Thames Water confirmed the normal diurnal patterns of peak flow in morning and evening had been replaced with 12 hours of higher flow rates.
• Had the same issue occurred at  ...  view the full minutes text for item 5.

No complaints had been received.

There was no other business due to time restrains.

To be confirmed.

Members of the committee wished to continue to meet at this time. The date of the next meeting would be confirmed after the May local elections.