Technical Manual: Conduits through Embankment Dams (FEMA 484)

Chapter 12—Renovation of ConduitsHDPE pipe should be carefully handled and stored according to all of themanufacturer’s recommendations. The manufacturer often ships handlinginstructions with the HDPE pipe. Cold weather handling precautions should beused to eliminate any impacts on HDPE pipe when temperatures are at or belowfreezing to avoid fracturing of the pipe. Handling of HDPE pipe when thetemperature is below -10 °F is not recommended. The pipe should not be droppedor allowed to be dumped when off-loading. Strap slings should be utilized forstraight HDPE pipe and the use of chains and hooks should be avoided. Liftingpoints should be well spread and evenly spaced. The HDPE pipe should be fullyinspected at the time of delivery, with any defects noted. The HDPE pipe should bestacked on firm, flat ground, adequately supported, kept away from heat sources, andkept in original protective packaging until used. Pipes should not be stacked higherthan five units or 10 feet, whichever is less. Stacking pipe with differing wallthicknesses and pressure ratings should be avoided. Testing has shown that unlikePVC, HDPE pipe does not become brittle under exposure to ultraviolet (UV)radiation. This resistance to UV radiation is the result of the small percentage ofcarbon-black which is added to the HDPE pipe material during the manufacturingprocess. Since virtually all conduits are buried, such exposure is generally minimal.Installation.—HDPE pipe is a flexible material and, as such, can easilyaccommodate minor changes in vertical and horizontal alignment of the existingconduit being lined. Guidance on sliplining installation includes:• Preparation of existing surfaces.—The existing conduit surfaces that grout will beplaced against need to be free of roots, sediments, mineral deposits, dust,latence, loose or defective concrete, curing compound, coatings, and otherforeign materials. Any sediments or debris should be removed from the invertof the existing conduit. Any bolts or other projections should be cut off flushand/or ground smooth with the interior surface of the existing conduit. Seesection 9.6 for guidance on cleaning conduits.A thorough inspection of the existing conduit is required prior to installing theHDPE slipliner to ensure that no obstructions remain that may hinder sliplinerinsertion. Prior to slipliner insertion, a soft pig or inflatable pipeline sphere ofthe same diameter as the HDPE pipe should be pulled through the existingconduit to check for proper clearance. Consideration should be given foradequate spacers and grout pipes to be attached to the HDPE slipliner.• Leak testing of joints.—Hydrostatic testing of the joints is required and should bedone prior to installation, using a sustained pressure test to find leaks in theHDPE slipliner. Prior to performing the hydrostatic test, the slipliner shouldbe properly restrained from movement. Depending on the limits of the testingequipment, the entire length of HDPE slipliner can be tested at one time or thetest can be separated into shorter sections. If a leaking joint is found, it will305