FEMA Filter Manual

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FEMA Filter Manual

FEMA Filter Manual - an OverviewWorkshop No. 19Water flowing in eroded slot ofspecimen bottom has nearly full appliedpressure1.0 mm preformed hole isnot erodedFeb. 22-23, 2012Emmitsburg, MDThin skin at filter face has voids chokedwith eroded debris.Water seeping in voids just below choked filterface is approximately at atmospheric pressureUS Army Corps of EngineersBUILDING STRONG ®


Filters for Embankment Dams -Best Practices for Design andConstruction• NDSP sponsored development of thedocument• Joint agency effort2BUILDING STRONG ®


Primary Authors• David Hammer, USACE (retired)• Danny McCook, NRCS (retired)• Mark Pabst, USACE and Reclamation• Jim Talbot, NRCS (retired)• Noah Vroman, USACE3BUILDING STRONG ®


Chapters1. Purpose and Theory of Filters2. Types of Filters and Applications3. Additional Applications4. Laboratory Testing5. Filter Design Procedure6. Other Design Considerations7. Construction4BUILDING STRONG ®


NomenclatureNarrowly graded = Uniformly graded = Poorly gradedBroadly graded = Widely graded = Well graded5BUILDING STRONG ®


NomenclatureOLD (Sherard)d = base soil particle diameterD = filter particle diameterNEWDxxYD85B, D15F, D15E, etc.6BUILDING STRONG ®


NEWNomenclatureDxxYD85B, D15F, D15E, etc.This was done to help in two stage filterdesign where the filter of one stage is thebase of the other.7BUILDING STRONG ®


NomenclatureOLD―Filter‖ and ―Drain‖Historically used interchangeably as nouns andverbs.NEWFilter = first stageDrain = second stage8BUILDING STRONG ®


Chapters1. Purpose and Theory of Filters2. Types of Filters and Applications3. Additional Applications4. Laboratory Testing5. Filter Design Procedure6. Other Design Considerations7. Construction9BUILDING STRONG ®


1. Purpose and Theory• 50% of dam failures are related toseepage.• Filters prevent particle movement (piping).• Filters are protective elements.• Cost, constructability, and reliability gohand-in-hand in providing an economicallysafe structure.10BUILDING STRONG ®


1. Purpose and Theory11BUILDING STRONG ®


1. Purpose and Theory12BUILDING STRONG ®


1. Purpose and Theory13BUILDING STRONG ®


Chapters1. Purpose and Theory of Filters2. Types of Filters and Applications3. Additional Applications4. Laboratory Testing5. Filter Design Procedure6. Other Design Considerations7. Construction14BUILDING STRONG ®


2. Types of Filters & Applications• New Dams• Existing Dams15BUILDING STRONG ®


2. Types of Filters & ApplicationsChimney filterBlanket filterSlope protectionNew DamToe drainExisting DamExisting DamSlope protectionHStability bermChimney filter> H 216BUILDING STRONG ®


2. Types of Filters & ApplicationsEmbankment Dam Design Elements (zones)ImperviousblanketTransition zoneRiprap and beddingUpstreamshellCutoff wallImperviouscoreCutofftrenchChimney drainChimney filterDownstream shellSeepage stability bermTrenchfilterBlanketToedrainDraintrenchDrainage ditchRelief well17BUILDING STRONG ®


2. Types of Filters & ApplicationsAppurtenant Structures• Conduit Filter Diaphragms• Filters Adjacent to Concrete Structures18BUILDING STRONG ®


2. Types of Filters & ApplicationsCutoff collars should NOT be used19BUILDING STRONG ®


2. Types of Filters & ApplicationsEmbankment/Concrete Dam Interface 20BUILDING STRONG ®


2. Types of Filters & ApplicationsFilter protection of spillway chute walls21BUILDING STRONG ®


2. Types of Filters & ApplicationsBlankets (lower 1 st stage)22BUILDING STRONG ®


2. Types of Filters & ApplicationsBlankets (middle 2 nd stage)23BUILDING STRONG ®


2. Types of Filters & ApplicationsBlankets (upper 1 st stage)24BUILDING STRONG ®


2. Types of Filters & ApplicationsToe Drains – vertical trench25BUILDING STRONG ®


2. Types of Filters & ApplicationsToe Drains – trapezoidal trench26BUILDING STRONG ®


2. Types of Filters & ApplicationsToe Drains – 1 stage vs. 2 stage27BUILDING STRONG ®


2. Types of Filters & ApplicationsExisting toe drains 28BUILDING STRONG ®


2. Types of Filters & ApplicationsExisting toe drains29BUILDING STRONG ®


2. Types of Filters & ApplicationsExisting toe drains30BUILDING STRONG ®


2. Types of Filters & ApplicationsExisting toe drains31BUILDING STRONG ®


2. Types of Filters & ApplicationsExisting toe drains32BUILDING STRONG ®


2. Types of Filters & ApplicationsRecommendations – 1/2• New dams – Conduit filter diaphragms arerequired regardless of height, site conditions, orhazard classification.• Full filter protection is recommended for allsignificant to high hazard dams.• Cost should not be the basis for eliminating filterprotection in small dams.• When modifying existing dams, filter protectionis only added for identified deficiencies.33BUILDING STRONG ®


2. Types of Filters & ApplicationsRecommendations - 2/2• Collection of seepage on pervious foundationsshould not be underestimated.• Existing dams with large amounts of seepagecan be made worse by adding a filter that blocksflow in more pervious foundation layers.• Relief wells clog with time, resulting indiminished effectiveness. Maintenance isrequired.Clay tile and metal pipes should not be used for drains.34BUILDING STRONG ®


Chapters1. Purpose and Theory of Filters2. Types of Filters and Applications3. Additional Applications4. Laboratory Testing5. Filter Design Procedure6. Other Design Considerations7. Construction35BUILDING STRONG ®


3. Additional ApplicationsAbandonment of Old Drains and Grouting• Abandoned old drains need to be addressed.• As a minimum, plug the ends.• When grouting, do not fracture the dam.36BUILDING STRONG ®


3. Additional ApplicationsAdding Filter Protection to Existing Conduits• Unacceptable methods of adding filterunder conduits.• Removal and replacement of conduitsection for filter installation.37BUILDING STRONG ®


3. Additional ApplicationsLocation of Filter Around Conduit38BUILDING STRONG ®


3. Additional ApplicationsLocation of Filter Around Conduit39BUILDING STRONG ®


3. Additional ApplicationsMinimum Dimensions for Filters Added toExisting Conduits• Differs from the FEMA Conduit Manual40BUILDING STRONG ®


3. Additional ApplicationsGeotextiles in Embankment Dams• Technical Evaluation of GeotextilesLimitations of Geotextile FabricsSoil Discharge FaceCoarsedrainfill ondownstreamside ofgeotextileprovides widespacing ofcontact pointson soildischarge face41BUILDING STRONG ®


3. Additional ApplicationsGeotextiles in Embankment Dams• The supported face concept is introduced• Historical use of geotextiles in earth damconstruction42BUILDING STRONG ®


3. Additional ApplicationsRecommendations• Due to issues with clogging, geotextiles shouldonly be used in noncritical areas of embankmentdams.• Existing drains, when abandoned, must besealed to prevent the chance of any materialeroding into (them) . . .43BUILDING STRONG ®


Chapters1. Purpose and Theory of Filters2. Types of Filters and Applications3. Additional Applications4. Laboratory Testing5. Filter Design Procedure6. Other Design Considerations7. Construction44BUILDING STRONG ®


4. Laboratory TestingTwo Parts to this Chapter• Particle Retention• Material Quality45BUILDING STRONG ®


4. Laboratory TestingParticle Retention46BUILDING STRONG ®


Quality4. Laboratory Testing• Sample Size per ASTMMaximum size ofaggregate(mm)Minimum sample size(kilograms)Fine aggregateMinimum samplesize(pounds)2.36 mm (No. 8 sieve) 10 224.75 mm (No. 4 sieve) 10 22Coarse aggregate9.5 mm (3/8 inch) 10 2212.5 mm (1/2 inch) 15 3319.0 mm (3/4 inch) 25 5525.0 mm (1 inch) 50 11037.5 mm (1.5 inches) 75 16550 mm (2 inches)47100 220BUILDING STRONG ®


Quality4. Laboratory Testing• Soundness Test• Test for Plasticity (PI)• Sand Equivalent Test• Petrographic Analysis• Vaughan Test for Cohesion (Sand Castle Test)• Compressive Strength Test48BUILDING STRONG ®


Quality4. Laboratory Testing• Sand Equivalent TestSand heigth /Clay height x 100 = SEVSEV > 8049BUILDING STRONG ®


Quality4. Laboratory Testing• Sand CastleTest50BUILDING STRONG ®


Quality4. Laboratory Testing• Modified Sand Castle TestDry (cure) at 120°FModified Sand Castle and SEV showpromise of detecting cementing not pickedup by the PI test.51BUILDING STRONG ®


4. Laboratory TestingRecommendations 1/2• Plasticity of fines should always be measuredusing ASTM D4318.• When quality is suspect, self-healing potentialshould be measured using Modified Sand Castleand/or Compressive Strength Tests.• Quality requirements for filters should bespecified using test results and not qualitativestatements.52BUILDING STRONG ®


4. Laboratory TestingRecommendations – 2/2• Due to material quality issues, aggregateobtained from concrete recycling operationsshould never be used for filter or drain materialin embankment dams.Reclamation has a Crack Box study underway -stay tuned for more developments53BUILDING STRONG ®


Chapters1. Purpose and Theory of Filters2. Types of Filters and Applications3. Additional Applications4. Laboratory Testing5. Filter Design Procedure6. Other Design Considerations7. Construction54BUILDING STRONG ®


5. Filter Design ProcedureHow doyou selectthe basesoilgradation?What arethe finalgradationlimits?55BUILDING STRONG ®


5. Filter Design ProcedureBase Soil Selection• Base Soil VariabilityCoreFoundation56BUILDING STRONG ®


5. Filter Design ProcedureBase Soil Selection• Geologic InterpretationGradation data shows there‘s no differencebetween the layers.57BUILDING STRONG ®


5. Filter Design ProcedureBase Soil Selection• Geologic InterpretationGradation data shows theirs is a differencebetween the layers.58BUILDING STRONG ®


5. Filter Design ProcedureBase Soil Selection• UndifferentiatedUnits―Alluvium‖59BUILDING STRONG ®


5. Filter Design ProcedureBase Soil Selection• UndifferentiatedUnitsQ: What is Alluvium?A: Alluvium is material deposited bycreeks, rivers or other swiftly flowing water.It is NOT sand and gravel.60BUILDING STRONG ®


5. Filter Design ProcedureBase Soil Selection• Outliers and Sampling ErrorsOutlier61BUILDING STRONG ®


5. Filter Design ProcedureBase Soil Selection• Filter Barriers62BUILDING STRONG ®


5. Filter Design ProcedureBase Soil Selection• Base Soil Selection FlowchartsIn Situ SoilsEarthfill63BUILDING STRONG ®


5. Filter Design ProcedureRegrading• Mathematical ‗scalping‘ on the No. 4 sieve.• Corrects for internal instability.• Probably the single most common mistake in filterdesign.64BUILDING STRONG ®


5. Filter Design ProcedureRegrading• Incorrect65BUILDING STRONG ®


5. Filter Design ProcedureRegrading• Correct66BUILDING STRONG ®


5. Filter Design ProcedureRegrading67BUILDING STRONG ®


5. Filter Design ProcedureRegradingStep 2a- Base soil contains gravel.YesStep 2b- Base soil contains less than 15% fines.- Base soil is not gap graded.- Base soil is not broadly graded (i.e.,Cu not > 6 and Cz not between 1 and 3).AllyesNoStep 4- Place the base soil in a category based onthe % passing No. 200 sieve in accordance withthe base soil category's table.One or more are noStep 3- Prepare adjusted gradation curves by:a. Obtain a correction factor by dividing 100by % passing No. 4 sieve size.b. Multiply the % passing each sieve size of thebase soil < No. 4 by the correction factor.c. Plot the regraded curve.d. Use regraded curve to find % passing No. 200.68BUILDING STRONG ®


5. Filter Design ProcedureBase Soil CategoriesBase soilcategoryPercent finer than No. 200sieve (0.075 mm) (afterregrading whereapplicable)1 > 852 40 – 853 15 – 394 < 15Base soil descriptionFine silts and claysSands, silts, clays, and silty sandsSilty and clayey sands and gravelsSands and gravelsNote: mm = millimeter69BUILDING STRONG ®


5. Filter Design ProcedureFiltering CriteriaBase soil category12Filtering – Maximum D15FThe maximum D 15 F should be ≤ 9 x D 85 B, but not less than 0.2 mm, unlessthe soils are dispersive. Dispersive soils require a maximum D 15 F that is ≤6.5 x D 85 B size, but not less than 0.2 mm.The maximum D 15 F should be ≤ 0.7 mm unless soil is dispersive, in whichcase the maximum D 15 F should be < 0.5 mm.For nondispersive soils, the maximum D 15 F should be:3 40A 4015 where:A = Percent passing No. 200 sieve.4xD85B 0.7mm*+ 0.7mm*When 4 x D 85 B is less than 0.7 mm*, use 0.7 mm** - For dispersive soils, use 0.5 mm instead of 0.7 mm.4 The maximum D 15 F should be ≤ 4 x D 85 B of base soil after regrading.70BUILDING STRONG ®


5. Filter Design ProcedureFiltering CriteriaControl Points71BUILDING STRONG ®


5. Filter Design ProcedureFilter Gradation Limits• Horizontal Method• Vertical Method72BUILDING STRONG ®


5. Filter Design ProcedureLimit Fines Content and OversizeBase soil category Maximum D 100 F Minimum D 5 FALL categories≤ 2 inches(51 mm)0.075 mm(No. 200 sieve)73BUILDING STRONG ®


5. Filter Design ProcedureLimit SegregationBase soil categoryALL categoriesIf D 10 F is:(mm)< 0.50.5 – 1.01.0 – 2.02.0 – 5.05.0 – 10> 10Then, maximum D90F is:(mm)20253040506074BUILDING STRONG ®


5. Filter Design ProcedureDetermine the Gradation Band within the ControlPoints75BUILDING STRONG ®


5. Filter Design ProcedureFour Examples1. Particle Retention Filter2. Drainage Filter3. Transition Filter4. C-33 Concrete Sand76BUILDING STRONG ®


5. Filter Design ProcedureDetermine the Gradation Band within the ControlPointsParticleRetentionFilter77BUILDING STRONG ®


5. Filter Design ProcedureDetermine the Gradation Band within the ControlPointsDrainageFilter78BUILDING STRONG ®


5. Filter Design ProcedureDetermine the Gradation Band within the ControlPointsTransitionZone79BUILDING STRONG ®


5. Filter Design ProcedureDetermine the Gradation Band within the ControlPointsC-33,concretesand80BUILDING STRONG ®


Chapters1. Purpose and Theory of Filters2. Types of Filters and Applications3. Additional Applications4. Laboratory Testing5. Filter Design Procedure6. Other Design Considerations7. Construction81BUILDING STRONG ®


6. Other Design ConsiderationsCritical Gradient• More complicatedthan i > 1.IncreasingpipingpotentialDecreasingpipingpotential82BUILDING STRONG ®


6. Other Design ConsiderationsChimney Dimensions83BUILDING STRONG ®


6. Other Design ConsiderationsChimney DimensionsFilter ThicknessWidth – feetSlope 16 9 6 5 31:1 11.7 6.6 4.4 3.6 2.22:1 7.5 4.2 2.8 2.3 1.43:1 5.1 2.9 1.9 1.6 1.04:1 3.8 2.2 1.4 1.2 0.784BUILDING STRONG ®


6. Other Design ConsiderationsChimney Dimensions85BUILDING STRONG ®


6. Other Design ConsiderationsIdentifying & Investigating Material Availability86BUILDING STRONG ®


6. Other Design ConsiderationsIdentifying & Investigating Material AvailabilityVertical Face isRequired forExamination87BUILDING STRONG ®


6. Other Design ConsiderationsIdentifying & Investigating Material AvailabilitySandGravelCobble88BUILDING STRONG ®


6. Other Design ConsiderationsIdentifying & Investigating Material AvailabilityBouldersTrenchSpoil pile89BUILDING STRONG ®


6. Other Design ConsiderationsIdentifying & Investigating Material Availability• Cost Comparison for Imported versus OnsiteMaterials• Lack of Suitable Clean Materials• Production Plants for Filter Materials90BUILDING STRONG ®


6. Other Design ConsiderationsIdentifying & Investigating Material Availability• Commonly Available Filter MaterialsSieve size Percent passing, by weight3/8-inch 100No. 4 95-100No. 8 80-100No. 16 50-85No. 30 25-60No. 50 5-30No. 100 0-10No. 200 1 0-2 21Requirement beyond the ASTM C33 designation.2 Two percent stockpile, 5 percent in-place.91BUILDING STRONG ®


6. Other Design ConsiderationsIdentifying & Investigating Material Availability• Commonly Available Filter MaterialsSieve size Blend 579 1 No. 8 No. 892 inches — — —1½ inches 100 — —1 inch 90-100 — —¾ inch 75-85 — —½ inch — 100 1003/8 inch 45-60 85-100 90-100No. 4 20-35 10-30 20-55No. 8 5-15 0-10 5-30No. 16 0-5 0-5 0-10No. 50 — — 0-51This gradation is a blend, in equal parts, of gradation Nos. 5, 7, and 9. It isnot an ASTM standard aggregate.92BUILDING STRONG ®


6. Other Design ConsiderationsRecommendations• Inclined Chimneys should be > 5‘ wide.• Vertical Chimneys should be > 3‘ wide.• Blankets should be > 18‖ thick.• When designing drainage elements on coarsefoundations, the best understanding offoundation conditions will not be available untilafter excavation.93BUILDING STRONG ®


Chapters1. Purpose and Theory of Filters2. Types of Filters and Applications3. Additional Applications4. Laboratory Testing5. Filter Design Procedure6. Other Design Considerations7. Construction94BUILDING STRONG ®


7. ConstructionConstruction of Inclined Chimneys95BUILDING STRONG ®


7. ConstructionConstruction of Inclined Chimneys96BUILDING STRONG ®


7. ConstructionConstruction of Vertical Chimneys97BUILDING STRONG ®


7. ConstructionConstruction of Vertical Chimneys98BUILDING STRONG ®


7. ConstructionConstruction of Vertical Chimneys99BUILDING STRONG ®


7. ConstructionManufacture and Storage• SegregationFront to BackorBelt Segregation100BUILDING STRONG ®


7. ConstructionManufacture and Storage• SegregationRoll DownSegregation101BUILDING STRONG ®


7. ConstructionHauling and DumpingChimneyCrossing102BUILDING STRONG ®


7. ConstructionHauling and DumpingBellyDump103BUILDING STRONG ®


7. ConstructionSpreadingBlading104BUILDING STRONG ®


7. ConstructionSpreadingSpreaderBox105BUILDING STRONG ®


7. ConstructionSpreadingDoubleBinSpreaderBox106BUILDING STRONG ®


7. ConstructionSpreadingDumpingintoSpreaderBox107BUILDING STRONG ®


7. ConstructionSpreadingTowingSpreaderBox108BUILDING STRONG ®


7. ConstructionSpreadingTowingSpreaderBox109BUILDING STRONG ®


7. ConstructionSpreadingTruckMountedConveyor110BUILDING STRONG ®


7. ConstructionCompaction Moisture Requirements• Previously, recommended to water right in frontof the roller.• This results in ‗bulking‘ which limits densification.• Vibratory compaction overcomes ‗bulking‘.• Moistened sand segregates less.• Permeability and self healing are more importantthan density.111BUILDING STRONG ®


7. ConstructionBulking112BUILDING STRONG ®


7. ConstructionCompaction Specification• Minimum 70% relative density.• Per ASTM D4253 and D4254.113BUILDING STRONG ®


7. ConstructionField Compaction• Vibratory Compactors.• Compactor Operation.• Compaction of Contacts with Adjacent Materials.114BUILDING STRONG ®


7. ConstructionField Compaction115BUILDING STRONG ®


7. ConstructionProtecting Placed Fill116BUILDING STRONG ®


7. ConstructionProtecting Placed Fill117BUILDING STRONG ®


7. ConstructionRemoving an Equipment Crossing118BUILDING STRONG ®


7. ConstructionGeomembrane Protection at Equipment Crossing119BUILDING STRONG ®


7. ConstructionDamage to Pipes• Compaction by ‗bucket thumping‘.• Wheel rolling.• Haunches not backfilled.• Equipment crossings without sufficient cover.120BUILDING STRONG ®


7. ConstructionField Testing - Density• Sand cone test.• Nuclear moisture-density meter.• Frequency of testing.121BUILDING STRONG ®


7. ConstructionLab Testing - Density• Relative Density.• Vibratory Hammer.• Proctor Maximum Density.122BUILDING STRONG ®


Narrow Toe Drain123BUILDING STRONG ®


Narrow Toe DrainDuring refilling, cloudy discharge was seen comingfrom the new drain.Silt and sand appear in the sedimentation traps.A forensic investigation was undertaken.124BUILDING STRONG ®


Narrow Toe Drain125BUILDING STRONG ®


Narrow Toe DrainMissing Filter126BUILDING STRONG ®


Narrow Toe DrainFnd soil pipesinto gravel drain127BUILDING STRONG ®


Narrow Toe DrainFnd soil enterspipe128BUILDING STRONG ®


Narrow Toe DrainTrench sidesare too steepDrain toonarrow*Filtertoonarrow*Trench istoo deepfor thiswidth* Too many zones for this widthTrench width istoo narrow129BUILDING STRONG ®


Filter Design Standard RevisionsReclamation – Release, Spring 2012.NRCS – Release, Spring 2013.USACE – No plans.130BUILDING STRONG ®


Some think the glass is half emptyothers, half full.Engineers wonder why the correctsize glass wasn’t used.Questions?BUILDING STRONG ®

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