Make sure the site is prepared and ready. The tanks and sumps should be in place. Pipe Burial Guidelines recommended burial depth of UPP pipe is a minimum of 12" (300mm). All trenches should be sloped back towards the storage tanks. The fall back (slope) for all pipework to the tank chambers should be a minimum of 1/8" per foot or 1m every 100m. This may vary to meet local requirements.
The position of the entry fittings at the furthest dispenser sump away from the tank chambers may be considerably higher than that of the entry fittings on the closest dispenser sump.
Vapor return lines should have a slope of 1/4" per foot and never less than 1/8" per ft. back towards the tank farm, unless in-line joints such as elbows are to be used and trench corners should have a radius of 5ft (1.5m). A recommended 6" (15cm) bed of backfill material should be laid underneath the pipe prior to installation and there must never be voids under or around the pipe.
Clean washed sand and backfill material must not be contaminated with any petroleum product or other contaminant. When laying duct onto a concrete base a 6" (150mm) thick bed of compacted sand should be laid on the concrete, below the duct.
All beds should be laid so that the pipe will not dip or sag when it is installed. Laying of pipe should start from the tank farm. Underground pipe runs may be continuous or have electrofusion welded joints. Any mechanical joints or compression fittings must be located within a containment chamber or sump.