Technical Manual: Conduits through Embankment Dams (FEMA 484)

Conduits through Embankment Damsgrouting operations should be opened to monitor the progress of grouting andobserve any connections between grout holes due to existing voids around theconduit. This will assist in the assessment of areas where notable erosion andembankment damage has occurred and the need for secondary and tertiary groutholes.Prior to any grouting or other conduit remediation work, consideration should begiven to the installation of appropriate instrumentation in the vicinity of the conduitin order to (1) establish baseline water pressure and seepage gradient conditions priorto repair work, and (2) detect any changes to embankment and foundation waterpressures that may result from corrective actions. Depending on the nature of theproblem and the corrective actions, such instrumentation will indicate whether therepairs are successful in lowering embankment water pressures, or when repairs maycause undesirable changes that require further corrective actions.Grouts used for injection into defects or joints and along conduits are usuallycementitious or chemical.• Cementitious.—For guidance on cementitious grout, see section 14.2.2.• Chemical.—For guidance on chemical grout, see section 14.2.2. Figure 192shows grouting operations within a conduit. Chemical grouts have also beenused for grouting voids using drill holes from the surface of the embankmentdam. For additional guidance on chemical grouts, see USACE’s ChemicalGrouting (1995a).See the Lake Darling case history in appendix B, for an example of grouting of voidsexisting along a conduit.14.2 Repair techniquesRepairs to conduits are typically performed to prevent further deterioration or priorto more extensive renovation methods. Repairs often are done to stop the inflow ofwater into the conduit through cracks or joints. The following sections mainlypertain to the repair of concrete conduits. For repair guidance for plastic pipe, seesections 12.1.1 and 12.2; for repair guidance on steel pipe, see section 12.1.2.14.2.1 Concrete repairsConcrete used in modern conduits is very durable and if properly proportioned andplaced will provide a very long service life under normal operating conditions(Reclamation, 1997, p. 1). However, many existing conduits were constructed yearsago using early concrete technology. Neglecting to perform periodic maintenance and348