Technical Manual: Conduits through Embankment Dams (FEMA 484)

Chapter 12—Renovation of Conduitsachievable, and the steel pipe slipliner is typically designed to withstand allinternal and external loadings independently from exterior conditions.Grout injection can be accomplished by a number of methods, includinggravity and pressure:• Gravity.—For guidance on gravity grouting, see section 12.1.1.• Pressure.—Steel pipe slipliner grout pipes (typically 1 to 1½-inchdiameter) are welded to the crown of the slipliner prior toinstallation. For guidance on pressure grouting, see section 12.1.1.Postinspection and acceptance.—Trained personnel should visually inspect thecompleted steel pipe slipliner installation to evaluate the conditions within therenovated conduit. If the sliplined conduit is too small for man-entry inspection,CCTV inspection methods should be used. See section 9.5.2 for guidance oninspection of conduits. No damage to linings or coatings, or infiltration ofgroundwater should be present.Maintenance and repair of the completed steel pipe slipliner.—Maintenancetypically performed on steel pipe slipliners involves coatings on the interior of theslipliner. The interior surface of the pipe may require periodic recoating, if it hasbeen subjected to abrasion or corrosion. The only other maintenance required forsteel pipe slipliners would involve cleaning of the conduit. Periodic operation of theconduit usually is sufficient to flush sediments through the system. The steelslipliner is smooth and generally resists the adherence of sediment. See section 9.6for guidance on cleaning of conduits.If the steel slipliner experiences some type of localized damage (abrasion, buckling,cavitation, corrosion, etc.) over the long term, the damage should be assessed bytrained personnel using man-entry or CCTV inspection methods as discussed insection 9.5. Repair of steel pipe slipliners after installation and grouting is completedcan be accomplished, if the pipe is of sufficient diameter to allow man-entry. If thedamaged area of steel pipe is not extensive, the repair would typically involve cuttingout the damaged area and welding a new piece of steel plate in place or applyingweld material in the damaged area. The welded material would be ground to asmooth finish. If the steel pipe slipliner diameter is too small for man-entry, a steelpipe slipliner of smaller diameter can usually be inserted and grouted in place.For examples of projects that utilized steel pipe sliplining, see the case histories forComo and McDonald Dams in appendix B.323