Water and Effluent Treatment Magazine
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10 WET NEWS JANUARY 2015 New pipework included complex manifold layouts Crampton WTW's 21st century makeover • South East Water's Crampton WTW was built 45 years ago. But the upgrade to make it one of today's most technically advanced, fully automat- ed facilities required ten shutdowns of live supply pipelines – while it re- mained fully operational. Stuart Griffiths explains. TECHKNOW • The design and build contract centred on the existing 9,500m³ capacity concrete storage tank • Bellmouth-shaped pipes were installed through 250mm thick reinforced concrete tank walls • Re-routing new supply pipework has meant half the original site area is now redundant, freeing up land for redevelopment or sale • 2km of mainly ductile iron pipework was installed, varying from 250mm to 500mm diameter • Trenchless directional drilling eliminated possible access restrictions for local residents NEED TO KNOW 1 The very last connection linking treated water supplies into the delivery mains to Riverhill proved the most difficult and triggered a three-week contract extension 2 Even though the conventional 4m deep open cut trench was dug only in short sections to maintain its stability, the excavation frequently flooded 3 Every shutdown proved a major logistical exercise T he extensive £4.6M up- grade undertaken by J Murphy & Sons at South East Water's (SEW) Cramptons Road water treatment works (WTW) at Sevenoaks, Kent de- manded ten programmed shut- downs of key, live supply pipe- lines while still ensuring the 45-year old plant always re- mained fully operational. In addition, the area's great crested newts and resident bats were carefully protected while more than 2km of new pipe- work was integrated into the original site layout. The new pipework re-routes borehole water supplies through the plant's contact storage tank and into existing pipework feeding three nearby service reservoirs. Also boasting a new state of the art pumping station, chemi- cal dosing system and control station, the now fully auto- mated works continues to sup- ply 40,000 Sevenoak's residents with more than 21 million litres of treated water every day. Contact tank Built in 1969, Cramptons Road WTW, 3km north of Sevenoaks, abstracts aquifer water through onsite and nearby boreholes. A"er chemical dosing and stor- age in an underground contact tank, the treated water is pumped to three service reser- voirs some 7km away that pro- vide a major water source for Sevenoaks. The treatment works is located on a partially wooded three hectare site bordered by PROJECT SPECS • £4.6M upgrade of Crampton WTW at Sevenoaks • Replace the old pumps, chemical dosing system and much of the onsite pipework • Install new facilities and an auto- mated control room • Re-route borehole water supplies THE VERDICT • The state-of-the-art fully automated motor control centre now only requires occasional on-site checking • JMH Directional Drilling completed the work in just three days, a saving of at least four weeks over conventional open trenching methods • The fully automated works continues to supply 40,000 Sevenoak's residents with more than 21Ml/d ONSITE REFURBISHMENT housing and a suburban rail line, and the original buildings housed not only a pumping sta- tion and chemical dosing facili- ties, but also headquarter offices for the then owner West Kent Water. Pipework With these offices long empty, and the works' pumping and chemical facilities in need of a considerable upgrade, current owner South East Water decided to replace the old pumps, chem- ical dosing system and much of the onsite pipework with new facilities and an automated con- trol room. These have been located mainly on a previously under- used area of the site but still close to the original central bur- ied contact storage tank which is being retained. By carefully re-routing new supply pipework, about half the original site area is now redun- dant and demolition of the old structures frees up this land for redevelopment or sale. The treatment works takes its water from four boreholes, three on site and a fourth a few hundred metres north of the plant. This aquifer supply was orig- inally routed directly into the buried, twin cell contact storage tank before being fed, when needed, to the pumping station. Here it was dosed with chlorine and pumped into existing onsite water delivery mains feeding to Riverhill, Solefields and Oakbank service reservoirs on the outskirts of the town.