Download - Engineering Surveyor

Sewers and drains: initial checksBefore setting-out sewers and drains, the site engineer should mark the approximate line(s) then:walk the line, noting existing features and correlate with the site drawings. note and report any variationsnote any potential setting-out or construction difficulties and consider solutionswhere possible, check soil conditionsclear any discrepancies and agree the proposed method with the supervising authority before proceedingwith the detailed setting-out.Adjacent and crossing existing servicesThe supervising authority should have notified the statutory undertakers of the proposed works, obtained details ofadjacent services and checked these thoroughly before proceeding to ensure adjacent cables and pipes will not beat risk. The site setting-out engineer should: consult public utilities drawings of mains and cables to ensure that proposed sewers and manholes do notconflict with these services. If in doubt, dig trial holes do not assume that an existing sewer follows a uniform gradient or straight line between manholes. Do notforget to take into account pipe thickness and collars or patent joints mark up drawings with all available information and confirm these with the statutory undertakers check that the distance between new and existing services will be sufficient for excavation, trench supportand working space, including construction of manholes.Warning: Record drawings of existing services are frequently unreliable.Interference by drain connectionsInspect the drawings for the location of drainage connections and determine whether these might interfere with anyadjacent services, particularly as regards to level/depth.Note: House services are unlikely to be shown.Manhole positionsAgree and confirm with the supervising authority the intended location of the manholes on the ground. Normally,sewer drawings do not show exact positions or take account of local details.Discharge levelsIf a new sewer is to discharge into an existing manhole or outfall, check physically on site that the level shown on thedrawings is accurate. This is vital – errors may require redesign of part or whole of the system.Gully connectionsCheck that the surface water sewer invert level is sufficient to accommodate connections from road gullies.CIRIA C70955