Technical Manual: Conduits through Embankment Dams (FEMA 484)

Conduits through Embankment DamsInitial inspection of the existing conduit.—For a discussion of the initialinspection of an existing conduit refer to section 12.1.1.Selection of the diameter and thickness.—The selection of the diameter andthickness of the steel pipe slipliner should consider the following factors:• Size and condition of the existing conduit.—Similar size and condition requirementsare needed for steel pipe slipliners as are used for the design of HDPEslipliners, see section 12.1.1 for further details.• Discharge requirements.—Similar discharge requirements are needed for steel pipeslipliners as are used for the design of HDPE slipliners, see section 12.1.1 forfurther details.• Clearance requirements for grouting of the annulus between the existing conduit and the steelpipe slipliner.—Similar clearance requirements are needed for steel pipe sliplinersas are used for the design of HDPE slipliners, see section 12.1.1 for furtherdetails. However, it should be noted that flanged joints generally require moreclearance than heat fused HDPE joints or welded steel joints.• Internal and external loadings.—Similar loadings can be expected on steel pipeslipliners as are used for the design of HDPE slipliners; see section 12.1.1 forfurther details. Steel pipe slipliner thickness requirements are generallygoverned by external pressures and the potential for buckling during futureunwatering of the slipliner. Steel pipe should be designed in accordance withindustry-accepted methods, such as those found in AWWA M11 (AWWA,2004c), Amstutz (1970), and Jacobsen (1974).Thermal expansion/contraction.—Thermal expansion/contraction is generallynot a concern with steel pipe slipliners, as long as it does not have any portionexposed to the environment.Stress cracking.—Stress cracking is generally not a concern with steel pipeslipliners.Fabrication.—Steel pipe used for sliplining should be fabricated in accordance withAWWA C200 (1997) and ASTM A 36 and A 53. The steel pipe slipliner should behydrostatically tested at the factory based on the design pressures. The steel pipeslipliner should be coated as specified by the designer.To avoid delays to the construction schedule, the steel pipe slipliner should be shopfabricated while other site preparations for installation of the slipliner are beingperformed (e.g., construction access, or concrete removal). Depending on thediameter and length of the steel pipe slipliner, it may be advantageous to shop318