PC Channel Islands

Another busy year for Guernsey Water

GUERNSEY WATER PROFILE Guernsey Water has enjoyed another busy year of capital development projects, ranging from the creation of a new operational depot in St Andrews to vital surface and foul water main separations in St Peter Port.

As a business unit of Guernsey’s Public Services Department, Guernsey Water oversees the collection, treatment and distribution of high quality drinking water to around 65,000 islanders. Despite being part of the States of Guernsey, Guernsey Water acts as a trading board with a turnover of £10m per annum, and creates all of its income from water charges. Around half of this income is invested into the drinking water infrastructure, which consists of over 500km of water main, four water treatment works, sixteen raw water storage reservoirs, four treated water service reservoirs and twelve raw water pumping stations. There is no external shareholding in the business.

2011 was a typically busy year for GW, and included closer working with Guernsey’s wastewater function. The proposal to amalgamate the two functions into one body will be considered by the States of Guernsey early in 2012.

Here are a few of the capital projects that took place during 2011:

Brickfield House Operational Depot

 For much of Guernsey Water’s history (and previously the States Water Board), staff and operations have traditionally been spread out over a number of sites. However, the long-term intention has always been to bring everyone and everything together into one site, and in 2011, this ambition was finally realised.

Back in 2003, the States Water Board purchased the St Andrew’s quarry site for £2million. After carrying out stabilisation works on some of the quarry walls and installing the service infrastructure, consideration began on creating a new operational centre on the site which would allow full centralisation of the business. This ambition was noted within Guernsey Water’s first Business Plan, published in 2003.GUERNSEY WATER PROFILE

However, there followed a long hiatus while the States Water Board/Guernsey Water worked to gain the appropriate planning permissions from the Environment Department. Planning permission was finally gained in December 2009 which allowed the tendering process to begin. The development contract was awarded to Harbour View in February 2010, and work began two months later.

The contract value was just under £5million, and this was funded through the rationalisation and selling off of Guernsey Water’s property assets. This included the disposal of Jubilee Terrace at South Esplanade in St Peter Port, where a number of staff had previously been sited.

The contract required the development of a fit-for-purpose operational depot which would be able to meet the business’ requirements for fabrication, machining, storage and electrical testing, whilst allowing space for the centralisation of all 75 or so staff into one building. As staff and operations had previously been spread among three sites (South Esplanade, St Saviours treatment works and the original depot at the St Andrew’s site) this took careful planning in order to balance the needs of the business with the requirements of the planners.

The first phase of the contract, the development of the depot itself, was completed by early May 2011. The second phase, the demolition of the old depot and creation of a new external compound area began straight after this, and was completed within two months. The third and final phase, external works and car-parks, was completed on 22nd August 2011. By the end of September the snagging items were rectified and the project complete.

An opening ceremony was held for the depot on 13th May 2011 shortly after the first phase was complete, and the building was officially named ‘Brickfield House’. The site has been referred to as the Brickfields since the 19th century, so it seemed a fitting name to tie the past and future together.

The benefits of centralising operations and staff onto one site were myriad – overhead costs would be reduced by operating and maintaining one building instead of three; staff communications and morale would be improved by working under the same roof in a new purpose-built depot; staff time would be saved by not having to travel from one site to another for meetings/discussions etc.GUERNSEY WATER PROFILE

At the time of writing, staff have been working in Brickfield House for over six months, and already the benefits of closer working and cross-pollination can be seen. Efficiencies and better ways of working are being realised, and this can only benefit the business, and ultimately, the customer.

Douit du Moulin Pumping Station

 As any water business will tell you, capturing precipitation when it falls is absolutely key in ensuring that customer demand for potable water can be met. Guernsey Water operates a number of pumping stations dotted around the coastline, which are able to capture the streamflow which does not travel directly into storage reservoirs, before it is lost to sea. Collecting and pumping ‘fresh water’ is far cheaper than desalination treatment.

In 2008, Guernsey Water identified the need for a new pumping station in the Douit du Moulin area in St Peters. The Pre du Murie station further inland was reaching the end of its useful operational life, and it was decided that the replacement station would be situated closer to the coast, giving it the capability to capture streamflow from an even greater area.

Local contractors United Formwork & Carpentry Ltd began work on site in July 2009. The £345k-rated contract for the station included the installation of a state-of-the-art mechanical screen manufactured by Huber, which circulates a perforated conveyor belt to remove debris (e.g. leaves, twigs) from the streamflow. This kind of screening is typically used in wastewater applications, but Guernsey Water decided that this innovative approach would work very well in a clean water application. The screens remove anything larger than 6mm diameter, and have a built-in wash cycle to keep them clean and operating effectively.GUERNSEY WATER PROFILE

Liaison took place with La Société Guernesiaise, Guernsey’s local history and conservation society, as the stream intake needed to be installed on their land. The intake was designed in such a way that it does not appear incongruous in the attractive fields and meadows of the area.

 The station itself was completed in June 2010, but further landscaping and screening works were carried out up to the end of that year. In early 2011 negotiations were formalised with La Société Guernesiaise regarding the management of the stream intake on their land, and by April 2011 the project was officially completed, and came in under budget by nearly £30k.

The now defunct Pre du Murie pumping station has been put up for sale with planning permission in place to convert it into residential accommodation. Income from this sale will be reinvested in Guernsey Water’s capital development programme.

Rehabilitation of Raw Water Transfer Main: Kings Mills WTW – St Saviours WTW

 Guernsey Water invests a lot of time and money into maintaining and improving the 500km of water main which reside under the ground. Maintaining the resilience of the network and the quality of water transported through it is vital to the business’ operations, and the capital programme takes this into account by apportioning expenditure to mains rehabilitation and replacement each year. GUERNSEY WATER PROFILE

One of the key strategic lengths of raw water main is the one between the two treatment works’ at Kings Mills in Castel and at St Saviours. It runs for 2.35km between the two plants and allows the raw water to be transferred from one to the other depending on demand and circumstances. At present, the treatment plant at Kings Mills is used as a back-up. However, plans are afoot to upgrade the plant to modern day standards which would improve water quality when it is required. Water Safety Plans have indicated that it is essential that Guernsey Water is able to transfer raw water between all of its treatment plants in order to be as resilient and reliable as possible.

Starting in early October 2010, Guernsey Water staff began the rehabilitation of the 16” UPVC main by sliplining the main with new HPPE (High Performance Polyethylene). Due to past experience in pipe rehabilitation, staff were able to carry out the task without recourse to external contractors (apart from the hiring of local company Ronez to excavate the roads where necessary). Unusually, parts of the main were located under private land, which necessitated the need to liaise with landowners in order to get the relevant permissions. Fortunately, the landowners were very cooperative and allowed the project to progress on time and to budget.

By February 2011 the project was complete, and another strategic piece of water infrastructure was secured for the next few generations.

 St Saviours WTW – Installation of an Electrolytic Chlorine Generation Plant

 Chlorine is an essential chemical for water businesses, as it is used for keeping treated water at a high quality while it passes through the distribution network (i.e. where water is transferred to customer homes). In Guernsey, chlorine disinfects the water through the use of a ‘contact tank’, which is a tank with different compartments into which the chemical is pumped. The treated water is mixed in the tank, and the design of the tank ensures that all of the water comes into contact with the chlorine for a specified amount of time, disinfecting it thoroughly.GUERNSEY WATER PROFILE

The problem that many water companies face is that chlorine is a hazardous chemical, and poses a danger to human health if not handled correctly. Originally, Guernsey Water would import cylinders of chlorine from the UK. However, this was an expensive and potentially dangerous process. In order to improve the process, Guernsey Water contracted Severn Trent Services to install an on-site electrolytic chlorine generation plant at each of the major sites.

The plant works by passing a direct electric current through a brine solution (water containing salt), creating sodium hypochlorite, which is then used to disinfect the treated water. Creating chlorine in this manner is much safer than dealing with large quantities of chlorine gas, and is more cost-effective as chlorine cylinders do not need to be imported then returned again once empty. At St Saviours the plant was manufactured by ClorTec, and the main civil engineering works package awarded to local company Crocker Civil Engineering following competitive tendering, at a cost of £178k.

The project began on site in October 2010, and was successfully completed a year later. Commissioning of the plant had to be planned carefully as it required taking the water treatment works offline for a short period of time. For the next step, Guernsey Water will be installing a similar plant at one of its service reservoirs in the Forest.

Kings Mills WTW – Interim Improvements

 As mentioned previously, it is planned to upgrade Kings Mills WTW in order to produce better quality drinking water when it is called into action. Before this can happen, it is important that the basic infrastructure at Kings Mills was improved to an interim level whereby the upgrading could take place.GUERNSEY WATER PROFILE

The main thrust of these interim works was to maintain the integrity of the contact tank and to improve the basic control and operation of the plant. One of the key aspects of this was to fit new filter nozzles into the existing sand tanks; a careful operation in which 1,300 nozzles were installed to within a 3mm tolerance over a four-day period. The nozzles work in two different ways – when the tank is full of water, gravity pulls the water down through the 3mm holes in the nozzles, filtering it through to a lateral pipe which transports the water away for further treatment in the contact tank. Once the filter becomes blocked, then they are backwashed with air being pumped back through the nozzles. This cleans the filter and after a period of water washing and recirculation the normal filtering process resumes.

Contractors AMT (Applied Materials Transfer Systems Ltd) installed the filter nozzles, and the project which ran from April to October was completed on time and within budget. The next set of upgrading works will take place in early 2012. Once these works have been carried out, Guernsey Water will be able to decommission Juas WTW in St Sampsons, which is also currently acting as a back-up WTW. This rationalisation of two back-ups into one will reduce expenditure on maintenance and overhead costs.

Wastewater Business Plan and CCTV Survey

 Guernsey Water’s wastewater section also had a very busy 2011, with the creation of their first Business Plan which will run from 2012 – 2019. The plan is due to receive final approval from the States of Guernsey in January 2012, and outlines the key issues and capital expenditure required over the next eight years in order to maintain, improve and extend the wastewater infrastructure in a planned and resilient manner.

Part of the plan involved carrying out a CCTV survey of the wastewater network, which consists of 150km of foul and surface water mains. Contractors OnSite carried out the work, the field element of which took place between September and December of 2010. The survey involved the use of a remote-controlled mobile camera system which was inserted into the sewer through manholes. Many hours of footage were collected and pored through to look for problems with the condition and/or structure of the sewers.

Once the mass of data was collected and sorted (the analysis of the data continued into March 2011), a categorisation of sewer condition was carried out which informed a prioritised plan of rehabilitation – and this forms the backbone of the Wastewater Business Plan.

Vauvert Surface Water Separation

 Historically, much of Guernsey’s urban wastewater network was built as a combined sewer system, so both foul flows (wastewater) and surface water flows (rainwater) travelled through the same pipe. As the Island’s population grew, foul flows through the system increased, and when combined with heavy rainfall, sewers would overflow, causing spills and flooding of ‘stormwater’ (a mix of sewage and rainwater). Sewage treatment requires the flows to be separated, so as to reduce volumes and guarantee the effectiveness of the bacteriological processes.

To counteract this, a programme of surface water separation has been running for a number of years, which essentially splits the two flows so that overflows are less likely to occur. One such project taking place in 2011 was the separation of flows in Vauvert, St Peter Port, which involved the installation of a new surface water main in the road.

Local contractors Geomarine began work on the contract during the 2011 school summer holidays in order to minimise inconvenience for the nearby primary school. The contract value was £150k, and formed part of a multi-phased project to separate flows in St Peter Port. Further works will take place along the remaining area of Vauvert in the future, and similar works at the adjoining New Place will commence in the 2012 summer holidays.

The new surface water main was immediately put to the test by a heavy rainfall event on 6th September – and it was pleasing to report that it passed with flying colours!

 

About the author

Roma Publications

Leave a Comment