Early in February the Parish Council sought discussions with Thames Water about the water mains running through Hambledon, in particular along Church Lane, Rock Hill and Lane End where there had been serious bursts during the previous six months, and about pressures in the various mains.
A representative of Thames Water attended a Parish Council meeting in March. Below our photograph of one of the leaks is the latest response from Thames Water, following that meeting.
Hambledon Clean Water Network
We have repaired three burst water mains recently, one in Lane End and two in Rock Hill. These were separate leaks on an 8’’ clean water main. This main transfers water from Hydon Ball Reservoir to a Water Booster station. We appreciate when our mains burst it can cause real disruption to the local area and can interrupt customers’ supplies and apologise for the disruption. We have been working closely with Surrey County Council highways department to ensure any roads affected by the leaks are returned to an acceptable state. We have agreed a larger area of road that shall be re-surfaced following the most recent leaks at Rock Hill. We have investigated recent reports of further visible leaks in the area and tested any standing water but have not found evidence of any leaks.
We have reviewed the area and found the mains around the village are relatively new. The area around Hambledon consists of 20.3km of distribution network. 19% of this has been installed after 1990, 12% between 1970 and 1990, and 27% was installed before 1970 but is not Victorian. The remaining water network is Victorian. Over the last 10 years, any mains that were considered a high risk due to condition and leakage have been replaced. Consequently, we do not have any current plans for mains replacement. However, we are reviewing the performance of water mains around this area, in particular the recent bursts in Lane End and Rock Hill. We model the performance of our entire network taking into account asset condition and asset failure. Based on this, if the main fits the criteria as being high risk, we will look at replacing these in the future.
We have checked the pressure in this particular area and can confirm that the pressure has not changed or been increased and is within acceptable levels for the water network. The pressures in the village do not relate to the proximity of the reservoir, rather the relative elevations of the reservoir and the village. There is an 80m difference in elevation, therefore there will always be significant network pressures as a result. Much of the area around Guildford has very variable elevations and this makes calming the pressures complex as lower pressures in Hambledon would mean that the network would have insufficient pressure to reach other areas.
Leakage and resilience
In the area of Guildford, including Hambledon, we are currently undertaking an industry leading trial in conjunction with our contractor PN Daly to find leakage. We have increased the amount of logging equipment available on the network and developed analytical models to better understand water usage in the Guildford area. Recent successes include 13 hard to find, large leaks in the Guildford area, including a leak on an 18’’ trunk main. By fixing these leaks we have now stopped approximately 4.5 megalitres per day of leakage. We are also carrying out a “source-to-tap” review of the service we provide in the area following some of the issues faced by customers during the Christmas period. This will help us to assess where best to invest in the future to ensure resilience of our water supply and network.