Technical Manual: Conduits through Embankment Dams (FEMA 484)

Conduits through Embankment Dams11.3.4 Repair ................................................27611.4 Alternative means of reservoir evacuation . . . . . ..................27711.4.1 Siphoning . . . . . . . . . . . . . . . . . . . . . . . . . . . . .................27811.4.2 Pumping ..............................................28111.4.3 Removal of the inlet structure (tower or riser pipe) of a drop inlet spillway conduit . . . . . . . . . . . . . . . . . . . . . . ..................28211.4.4 Removal of the control structure of the spillway (concrete spillway) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .................28411.4.5 Excavation of a trench through an earthcut spillway ...........28411.4.6 Excavation of a spillway through the embankment dam abutment..................................................28411.4.7 Controlled breach of the embankment dam ..................28611.5 Gate or valve operational restriction . . . . . . . . . ..................28611.6 Reservoir operating restriction . . . . . . . . . . . . . . ..................287Chapter 12—Renovation of Conduits ...................................28912.1 Sliplining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .................29112.1.1 Thermoplastics .........................................29312.1.1.1 Design considerations................................29312.1.1.2 Construction considerations...........................30412.1.2 Steel pipe..............................................31612.1.2.1 Design considerations................................31612.1.2.2 Construction considerations...........................31912.2 Cured-in-place pipe . . . . . . . . . . . . . . . . . . . . . . . ..................32412.2.1 Design considerations ...................................32412.2.2 Construction considerations ..............................32712.3 Spray lining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .................330Chapter 13—Replacement of Conduits..................................33113.1 Embankment excavation slopes . . . . . . . . . . . . . ..................33213.2 Removal of the existing conduit . . . . . . . . . . . . . ..................33313.3 Design and construction of the conduit . . . . . . . ..................33313.4 Design and construction of the filter . . . . . . . . . ..................33313.5 Design and construction of the replacement embankment dam .....33313.5.1 Zoning ...............................................33413.5.2 Compaction considerations for backfill used in rebuilding theembankment dam...........................................33413.6 Construction impacts . . . . . . . . . . . . . . . . . . . . . ..................33513.7 Construction of a cofferdam or temporary diversion channel . ......33613.8 Design of entrance and terminal structures . . . . ..................33613.9 Microtunneling . . . . . . . . . . . . . . . . . . . . . . . . . . . .................33713.10 Horizontal directional drilling . . . . . . . . . . . . . . ..................341xiv