Email Anne Milton MP TODAY and let her know that Cranleigh has a sewage crisis. She has previously said that if she gets more than 5 emails from residents on a given subject she will act. Let’s make sure her Inbox is bursting!

It’s official, there’s no capacity in the sewage system for Crest Nicholson’s 149 houses off the Horsham Road and it could end up being stored on Snoxhall playing fields!

In a report from Thames Water (Thames Water Report on Capacity April 2015) they confirm that:

5.1.3 Foul System Improvement Works
The hydraulic model indicates that the foul network does not have available capacity downstream of the proposed connection manhole to accept the proposed development flows. On inclusion of the additional flows from the development site, an increase in the predicted volume of flooding and surcharge on the downstream sewer network is predicted to occur.

Thames Water statement on Crest Nicholson Site

Then Thames Water has come up with two options for all that raw sewage flowing from these houses.

Option 1: to provide a pumping station which could only operate in dry weather, or when existing sewer levels are low, which as far as we are aware would be rarely!

It will be based on a telemetry system, which if this is reliant on a good mobile signal, there will be simply no hope for it! A similar system in Alfold has consistently failed due to flooding of the equipment and poor phone signal.

Crest will need to conceal in the ground on the north-eastern edge of the site a huge 821m3 storage tank, which needs to store up to 19 hours’ worth of sewage from the estate.

This capacity is what the developers have calculated they need in the event of a 1 in 20-year flood (which happens when surface water caused by rainfall overwhelms the sewage network and/or when groundwater levels are high); this can also be referred to as a 20% chance of a flood occurring within any given year.

There seems to be no accommodation in the tank’s capacity for multiple flood events so we’re not sure what they propose if we have several days of heavy rainfall as we did in the winter of 2013/14 – these tanks would fail if that same event occurred.

Another problem is that after 12 hours of storing sewage there is a high risk of septicity which means that bacteria will multiply and this produces hydrogen sulphide. This is a colourless gas with the characteristic foul odour of rotten eggs; it is heavier than air, very poisonous, corrosive, flammable, and explosive!

The image below shows where this tank could be buried.

Sewage tanks on Crest Nicholson Site

Not very comforting for existing residents that will be living right next to this tank, which if it fails the effects would be catastrophic.

It is the developer’s responsibility to size this tank, not Thames Water, who are obviously washing their hands of this task, perhaps because if it fails it isn’t their liability!

Then there’s

Option 2: to stick an even bigger storage tank somewhere. Now where would be the perfect place? One of the community’s much-loved green spaces and our children’s football pitches perhaps? Yes, you guessed it, Snoxhall Playing Fields!

We would like to know who offered the Parish Council owned field for the storage of 1216m3 of foul waste, this is basically a sewage plant on Snoxhall.

It has the potential for the same problem with septicity and spillage as the tanks on the Crest site, however, there are very few details provided by Thames Water. A case of dump and run perhaps!

The image below shows the proposed position of the sewage tank under Snoxhall football pitches.

Sewage tanks on Snoxhall

You might at this stage be wondering where the sewage is going to go from the 125 houses at Amlets, we have heard that Thames Water has not given permission for these houses to be connected to the sewage system yet.

Then there’re 425 houses on the Berkeley’s site that have just been approved, we can’t wait to see what Thames Water’s strategy is going to be for this massive housing estate. Perhaps they have been saving a bit of space for Berkeley’s as they seem to have a special relationship.

We have already uncovered and advised Waverley Borough Council of the sewage issues, they are fully aware, however, they continue to dump all the Borough’s housing here and leave us with the mess.

Surprise, surprise now Berkeley’s has been approved we have been told that the Knowle Park Initiative (West Cranleigh Nurseries) have come out of the woodwork and could be in front of Waverley’s Joint Planning Committee as early as 27th April.


Email Anne Milton MP TODAY and let her know that Cranleigh has a sewage crisis and we need her help!


Read more about the sewage crisis in our articles