Trench Specification Guide for developers who choose to undertake ground works for water mains
or water and gas mains off the public highway in both contaminated and non-contaminated ground.
A) Trench specification for water main only (off the public highway).
B) Trench specification for water and gas mains laid in a common
trench (off the public highway).
Contact details
Telephone
08451 552 088*
Mon–Fri 8.30am to 5pm (4:30pm Fri)
A 24 hour emergency service operates
outside of these hours.
Please call 08457 823333
*Calls may be monitored or
recorded for training purposes.
Post
THE TABLE BELOW DETAILS BOTH PARTIES’ RESPONSIBILITIES FOR THE SCENARIOS ABOVE
Contaminated
land
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Excavate as required *1
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Non
contaminated`
land
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Excavate as required *2
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Developers responsibility
• Set out line and level.
• Excavate a minimum of 200metres of trench in advance of our arrival on site in accordance with finished line and level and trench specification above.
• Provide certificated driver and appropriate excavator/lifting equipment to work in conjunction with our main laying contractor. Excavate trench as required.
• Keep working area clear of all obstructions, i.e. scaffolding, plant, skips, materials etc.
• Supply pea shingle/sand.
• Place pea shingle/sand in base of trench ( to minimum of 80mm depth).
• Excavated spoil to be placed a minimum of 1 metre from edge of trench and surplus spoil to be removed from site.
• Provide trench support where necessary.
• Provide suitable plant and labour to excavate additional trenching in advance and back fill trenches, ensuring gang productivity is not adversely affected.
• Provide suitable plant and labour to excavate extra-over trenching to accommodate thrust blocks and oversize fittings etc.
• Place pea shingle/sand above pipe.
• Supply GSB1 where required to meet highway specification.
• Back fill trench and compact “As-dug” or GSB1 material.
• Surface restoration as required, providing materials where necessary.
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• De-water trench as necessary during main laying.
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• All road crossings must be back filled above pea shingle course with GSB1.
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• Supply water pipe and fittings.
• Lay pipe and fittings in excavated trench.
• Provide and place concrete for thrust blocks around bends and fittings.
• Pressure test.
• Chlorinate, sample and approve water main.
• Make final connection to existing network and complete all works in the public highway including excavation and reinstatement.
Developer Services Department
Affinity Water Ltd
Tamblin Way
Hatfield
Hertfordshire AL10 9EZ
Fax
01707 679 206
Email
[email protected]
Website
www.affinitywater.co.uk
N O T E S
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*1 – In contaminated land we generally lay ductile iron water mains rather than plastic. As iron pipe is much heavier than plastic, it requires a machine to handle. It is sometimes more productive and
safer to excavate the trench, lay the pipe and backfill the trench in one process rather than excavate the trench in advance. Where the developer chooses to excavate the trench in this manner
it will be necessary to provide two full time machines. One machine to excavate the trench ahead of our team, the other to lift pipes into the trench and place the bedding material. If the
absence of suitable machinery adversely affects our productivity, we will pass in the cost of waiting time to you
*2 – On uncontaminated sites where the developer chooses to excavate the trench. Affinity Water reserves the right to lay a coil of pipe in some instances. Where a coil is used, the developer’s
ground worker will be expected to provide a machine to pull the coil from the trailer into the trench.
REF CH 11/ 13
Our responsibility