Technical Manual: Conduits through Embankment Dams (FEMA 484)

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Conduits through Embankment DamsDepending on the model, camera-crawlers used in conduits with very smalldiameters (about 4 to 14 inches) have cameras with some pan, tilt, and zoomcapabilities, a wide range of tether pulling capacity (200 to 1,000 feet), and somesteering capabilities. Camera-crawlers used in conduits with diameters of 15 inchesor larger are steerable, have a greater cable tether-pulling capacity (500 to 1,500 feet),and have cameras that can provide a wider array of optical capabilities, including pan,tilt, and zoom. As the technology of CCTV inspection equipment advances, greatertether lengths and optical capabilities will become available. Actual tether limitsobtainable in the field, vary greatly, depending upon a number of factors, such asconduit diameter, bends, invert slopes, and existing invert conditions, such assediments, mineral encrustations, and bacterial growths.In large diameter conduits, the video camera can be attached to a scissor mechanismmounted to the transport vehicle. The scissor mechanism, controlled by theoperator, can raise or lower the video camera as needed for inspection. In addition,the video camera usually has a high powered zoom, which can be used to providecloseup views of areas that might be difficult for the transport vehicle to get near.These features allow examination of very large conduits with diameters as large as40 or 50 feet.If required, some models of camera-crawlers allow for the attachment of retrievaltools, such as alligator clamps, grippers, and magnets. These tools can be used toremove light debris or damage. The attachment of any type of retrieval tool willrequire additional clearance within the conduit to operate the retrieval tool. Somemodels of crawlers have robotic cutters attached to them. These cutters can be usedto remove debris or protrusions in concrete, steel, or reinforcement. Most cameracrawlersystems are portable and can be carried to conduit access locations(figure 130). The use of an all-terrain vehicle (ATV) may be beneficial for transportof equipment in difficult access areas.Sometimes the conduit is too small and a transport vehicle cannot be used, orobstructions/invert conditions exist that prevent the transport vehicle fromtraversing the conduit. For these types of situations, a small color video camera(1.5 to 3 inches in diameter) with maximum pressure depth ratings up to 1,000 feetof water can be used. Figure 131 shows an example of this type of video camera.This video camera can be attached to metal or PVC poles (commonly referred to aspush poles) and manually pushed up the conduit. Push poles are normally used forstraight sections of conduit. The use of push poles for advancement is generallylimited to about 400 feet of conduit length. If bends exist in the conduit, a flexiblesnake device (spring steel wire, coiled wire, or flexible polypropylene-jacketedfiberglass push rod) can be used instead of the push poles. A coaxial cable connectsthe video camera to a video cassette recorder and television monitor. Snake devicesare generally limited to about 75 to 200 feet of conduit length.224
Chapter 9—Inspection and Assessment of Conduit-Related ProblemsFigure 130.—Most CCTV inspection equipment is portable and can becarried to conduit access locations.The quality and adaptability of CCTVinspection equipment can vary greatly,depending on the requirements of theinspection. Any company or contractorselected to perform a CCTV inspectionshould have a wide range of availableequipment for differing site conditions. NoCCTV inspection equipment exists that isfully adaptable for all conditions, and avariety of crawler configurations andcameras may be required.Camera-crawler inspection equipment isexpensive to purchase, operate, andmaintain. The environment being inspectedFigure 131.—A small color video cameraused for CCTV inspection.is typically harsh and can pose many hazards and obstructions. Although rare,camera-crawler inspection equipment can become lodged in small diameter conduitsif adverse offsets or obstructions exist. If camera-crawler inspection equipmentbecomes lodged within a conduit, it can partially block the conduit, reducing itsdischarge capacity. Also, due to the harsh environment, this type of inspectionequipment can experience breakdown while operating within the conduit. Theretrieval process for removing a lodged camera-crawler can be expensive and timeconsuming. If the camera-crawler inspection equipment becomes stuck in totallyinaccessible portions of a conduit, complete abandonment and loss of the equipmentis possible. For this reason, the operator of any inspection equipment must be veryexperienced and have a clear understanding of the capabilities and limitations of the225
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Technical Manual:Conduits throughEm
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PrefaceTens of thousands of conduit
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Prefacecondition. The hazard classi
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PrefaceLakeLine MagazineMaryland Da
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Conduits through Embankment Dams11.
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Contents23 Precast concrete pipe be
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Contents81 On first filling, a high
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Contents117 This conduit was severe
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Contents158 An example of a histori
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ContentsFigures in the AppendicesNo
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ContentsB-33 Aerial view of Como Da
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ContentsB-81 Cross section of Wiste
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ContentsMASW, multichannel analysis
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Symbolsc, cohesionE', modulus of so
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ContentsD 3350D 4221D 4253D 4254D 4
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IntroductionConduits convey water f
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IntroductionFigure 3.—A 15-inch d
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Introductionunstable. When seepage
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IntroductionAn embankment dam with
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A vortex may form at the location w
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IntroductionWater from the reservoi
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IntroductionFlowing water from the
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IntroductionThe process of dislodgi
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Introductionbe observable at the su
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IntroductionFigure 11.—Example of
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Introductionwhere conduits were ass
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Introduction• Conduits within lev
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IntroductionFigure 12.—An example
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Introductionmore recent practiced h
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IntroductionThe “best practices
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Chapter 1GeneralConduits have been
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Chapter 1—GeneralFigure 14.—Ant
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Chapter 1—GeneralFigure 17.—Fai
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Chapter 1—Generalmeans the condui
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Chapter 1—Generalfacilitate futur
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Chapter 2Conduit MaterialsVarious m
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Chapter 2—Conduit MaterialsFigure
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Chapter 2—Conduit Materials• Co
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Chapter 2—Conduit MaterialsSteel
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Chapter 2—Conduit Materials2.3.2
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Chapter 3Hydraulic Design of Condui
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Chapter 3—Hydraulic Design of Con
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Chapter 4Structural Design of Condu
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Chapter 4—Structural Design of Co
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Chapter 5Foundation and Embankment
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Chapter 5—Foundation and Embankme
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Chapter 6Filter ZonesZones of desig
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Chapter 6—Filter Zonesseepage or
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Chapter 6—Filter ZonesFigure 87.
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Chapter 6—Filter Zones3. Upstream
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Chapter 6—Filter Zonesbedrock sur
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Chapter 6—Filter Zoneszones, and
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Chapter 6—Filter Zonesfiltering t
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Chapter 6—Filter Zonessoil. This
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Chapter 6—Filter Zones6.8 Specifi
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Chapter 6—Filter ZonesVarious deg
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Chapter 6—Filter Zones• For pre
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Chapter 7Potential Failure Modes As
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Chapter 7—Potential Failure Modes
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Page 211 and 212: Chapter 7—Potential Failure Modes
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Page 283 and 284: Chapter 10Evaluation by Geophysical
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Chapter 11—Appropriate Emergency
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Chapter 12Renovation of ConduitsThe
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Chapter 12—Renovation of Conduits
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Chapter 13Replacement of ConduitsGe
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Chapter 13—Replacement of Conduit
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Chapter 14Repair and Abandonment of
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Chapter 14—Repair and Abandonment
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ReferencesThe following references
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ReferencesBureau of Reclamation, De
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ReferencesCooper, Chuck, E. Wesley
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ReferencesJacobsen, S., “Buckling
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ReferencesNatural Resources Conserv
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ReferencesU.S. Army Corps of Engine
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ReferencesWooten, R. Lee, Peter S.
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Additional ReadingThe following ref
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Additional ReadingCarter, Brent H.,
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Additional ReadingJohnson, Brian, J
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Additional ReadingNatural Resources
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Additional ReadingU.S. Army Corps o
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Additional ReadingVan Aller, Hal, R
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GlossaryThe terms defined in this g
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Glossary• Backward erosion piping
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GlossaryCathodic protection system
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GlossaryConsequences (FEMA, 2004):
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Glossarymalfunction or abnormality
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GlossaryDrawdown (FEMA, 2004): The
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GlossaryFailure mode (FEMA, 2004):
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GlossaryGate chamber: An outlet wor
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GlossaryImpervious: Not permeable;
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GlossaryLeakage (FEMA, 2004): Uncon
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GlossaryOpen cut: An excavation thr
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GlossaryPolyvinyl chloride (PVC): A
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GlossaryResistivity: A measure of t
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GlossarySettlement (FEMA, 2004): Th
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GlossaryStandard Proctor compaction
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GlossaryThermoset (ASTM F 412, 2001
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GlossaryReferencesAmerican Concrete
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IndexAAbandonment of conduits, 225,
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IndexCompaction of backfill, 6, 10,
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IndexDDamembankment, 113-130, 333-3
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IndexExisting conduit, 23, 31, 45-5
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IndexHydraulic fracture, 4-11, 17,
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IndexMechanical caliper, 246Metal c
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IndexPressure flow, see Conduit, pr
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IndexSliplining, 39, 45-47, 51, 164
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IndexUUltrasonic pulse-echo, 245, 2
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Appendix AHistory of Antiseep Colla
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Appendix A—History of Antiseep Co
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Appendix BCase HistoriesIndexDam Lo
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Appendix B—Case HistoriesDam Loca
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Appendix B—Case HistoriesProject
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Appendix B—Case HistoriesFigure B
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Appendix B—Case Historiesproject,
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Appendix B—Case Historieswatersto
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Appendix B—Case HistoriesLessons
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Appendix B—Case HistoriesThe cond
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Appendix B—Case Historiesroadway.
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Appendix B—Case Historiesentire c
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Appendix B—Case Historieshauled i
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Appendix B—Case Historiescoal tar
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Appendix B—Case Historieshistory
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Appendix B—Case Historiesarea, a
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Appendix B—Case Historiespipe. Du
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Appendix B—Case Historiesinvert o
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Appendix B—Case Historiesdownstre
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Appendix B—Case HistoriesThe caus
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Appendix B—Case Historiesof sever
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Appendix B—Case HistoriesThe down
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Appendix B—Case Historieshose and
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Appendix B—Case HistoriesADownstr
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Technical Manual: Conduits through Embankment Dams (FEMA 484)

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