### DEPARTMENT OF THE ARMY EM 1110-2-1913 U.S. Army Corps of Engineers CECW-EG Washington, DC 20314-1000

Manual No. 1110-2-1913 30 April 2000 

### Engineering and Design DESIGN AND CONSTRUCTION OF LEVEES

1. Purpose. The purpose of this manual is to present basic principles used in the design and construction of earth levees. 2. Applicability. This manual applies to all Corps of Engineers Divisions and Districts having responsibility for the design and construction of levees. 3. Distribution. This manual is approved for public release; distribution is unlimited. 4. General. This manual is intended as a guide for designing and constructing levees and not intended to replace the judgment of the design engineer on a particular project. FOR THE COMMANDER:

RUSSELL L. FUHRMAN Major General, USA Chief of Staff

This manual supersedes EM 1110-2-1913, dated 31 March 1978.EM 1110-2-1913 30 April 2000 

## US Army Corps of Engineers 

# ENGINEERING AND DESIGN 

# Design and Construction of Levees

ENGINEER MANUAL

### AVAILABILITY 

### Electronic copies of this and other U.S. Army Corps of Engineers (USACE) publications are available on the Internet at http://www.usace.army.miVinetlusace-docs/. This site is 

### the only repository for all 

### official USACE engineer regulations, circulars, manuals, and other documents originating from HQUSACE. Publications are provided in portable document format (PDF).i 

### DEPARTMENT OF THE ARMY EM 1110-2-1913 U.S. Army Corps of Engineers CECW-EG Washington, DC 20314-1000

Manual No. 1110-2-1913 30 April 2000 

### Engineering and Design DESIGN AND CONSTRUCTION OF LEVEES

Table of Contents Subject Paragraph Page 

### Chapter 1 Introduction Purpose

......................................................... 1-1 1-1 Applicability

..................................................... 1-2 1-1 References

....................................................... 1-3 1-1 Objective

........................................................ 1-4 1-1 General Considerations

............................................. 1-5 1-1 Chapter 2 Field Investigations Preliminary and Final Stage

.......................................... 2-1 2-1 Section I Geological Study Scope

.......................................................... 2-2 2-1 Office Study

..................................................... 2-3 2-2 Field Survey

..................................................... 2-4 2-3 Report

.......................................................... 2-5 2-3 Section II Subsurface Exploration General

......................................................... 2-6 2-3 Phase 1 Exploration

................................................ 2-7 2-3 Phase 2 Exploration

................................................ 2-8 2-3 Borings

......................................................... 2-9 2-4 Geophysical Exploration

............................................ 2-10 2-4 Section III Field Testing Preliminary Strength Estimates

....................................... 2-11 2-6 Vane Shear Tests

.................................................. 2-12 2-6 Groundwater and Pore Pressure Observations

............................ 2-13 2-7 Field Pumping Tests

............................................... 2-14 2-7EM 1110-2-1913 30 Apr 2000

ii Subject Paragraph Page 

### Chapter 3 Laboratory Testing General

......................................................... 3-1 3-1 Classification and Water Content Determinations

.......................... 3-2 3-2 Section I Fine-Grained Soils Use of Correlations

................................................ 3-3 3-2 Shear Strength

.................................................... 3-4 3-7 Consolidation

..................................................... 3-5 3-7 Permeability

..................................................... 3-6 3-7 Compaction Tests

................................................. 3-7 3-7 Section II Coarse-Grained Soils Shear Strength

.................................................... 3-8 3-8 Permeability

..................................................... 3-9 3-8 Density Testing of Pervious Fill

....................................... 3-10 3-8 Chapter 4 Borrow Areas General

......................................................... 4-1 4-1 Available Borrow Material

........................................... 4-2 4-1 General Layout

................................................... 4-3 4-1 Design and Utilization

.............................................. 4-4 4-2 Chapter 5 Seepage Control Section I Foundation Underseepage General

......................................................... 5-1 5-1 Cutoffs

......................................................... 5-2 5-1 Riverside Blankets

................................................. 5-3 5-1 Landside Seepage Berms

............................................ 5-4 5-2 Pervious Toe Trench

............................................... 5-5 5-3 Pressure Relief Wells

............................................... 5-6 5-5 Section II Seepage Through Embankments General

......................................................... 5-7 5-8 Pervious Toe Drain

................................................ 5-8 5-9 Horizontal Drainage Layers

.......................................... 5-9 5-10 Inclined Drainage Layers

............................................ 5-10 5-10 Design of Drainage Layers

........................................... 5-11 5-10 Compaction of Drainage Layers

....................................... 5-12 5-10EM 1110-2-1913 30 Apr 2000

iii Subject Paragraph Page 

### Chapter 6 Slope Design and Settlement Section I Embankment Stability Embankment Geometry

............................................. 6-1 6-1 Standard Levee Sections and Minimum Levee Section

...................... 6-2 6-1 Effects of Fill Characteristics and Compaction

............................ 6-3 6-2 Section II Stability Analyses Methods of Analysis

............................................... 6-4 6-3 Conditions Requiring Analysis

........................................ 6-5 6-3 Minimum Acceptable Factors of Safety

................................. 6-6 6-4 Measures to Increase Stability

........................................ 6-7 6-4 Surface Slides

.................................................... 6-8 6-5 Section III Settlement General

......................................................... 6-9 6-6 Settlement Analyses

................................................ 6-10 6-6 Chapter 7 Levee Construction Section I Levee Construction Methods Classification of Methods

........................................... 7-1 7-1 Section II Foundations Foundation Preparation and Treatment

.................................. 7-2 7-1 Methods of Improving Stability

....................................... 7-3 7-3 Section III Embankments Embankment Construction Control

.................................... 7-4 7-5 Embankment Zoning

............................................... 7-5 7-6 Protection of Riverside Slopes

........................................ 7-6 7-6 Chapter 8 Special Features Section I Pipelines and Other Utility Line Crossing Levees General Considerations

............................................. 8-1 8-1 General Considerations for Pipelines Crossing Through or Under Levees

........ 8-2 8-2 General Consideration for Pipelines Crossing Over Levees

................... 8-3 8-3EM 1110-2-1913 30 Apr 2000

iv Subject Paragraph Page 

### Pipe Selection

.................................................... 8-4 8-3 Antiseepage Devices

............................................... 8-5 8-4 Closure Devices

................................................... 8-6 8-6 Camber

......................................................... 8-7 8-6 Installation Requirements

............................................ 8-8 8-7 Section II Access Roads and Ramps Access Roads

.................................................... 8-9 8-10 Ramps

.......................................................... 8-10 8-10 Section III Levee Enlargement General

......................................................... 8-11 8-12 Earth-Levee Enlargement

............................................ 8-12 8-12 Floodwall-Levee Enlargement

........................................ 8-13 8-13 Section IV Junction with Concrete Closure Structures General

......................................................... 8-14 8-15 Design Considerations

.............................................. 8-15 8-17 Section V Other Special Features Construction of Ditches Landside of Levee

............................... 8-16 8-17 Levee Vegetation Management

........................................ 8-17 8-17 Appendix A References Appendix B Mathematical Analysis of Underseepage and Substratum Pressure Appendix C Design of Seepage Berms Appendix D Filter Design Appendix E Drainage Trench Appendix F Emergency Flood Protection Appendix G Use of Soil Cement for Levee ProtectionEM 1110-2-1913 30 Apr 2000

v 

### Appendix H Notation List of Tables
No. Title Page 

### 1-1. Major and Minimum Requirements

......................................... 1-2 1-2. Classification of Levees According to Use

.................................... 1-3 2-1. Factors Requiring Intensive Field Investigations and Design Studies

................ 2-1 2-2. Stages of Field Investigations

............................................. 2-2 2-3. Types of Contour Maps

................................................. 2-3 2-4. Phase I Boring and Sampling Techniques

.................................... 2-4 2-5. Applicable Geophysical Methods of Exploration

............................... 2-6 2-6. Preliminary Appraisal of Foundation Strengths

................................ 2-7 3-1. Laboratory Testing of Fine-Grained Cohesive Soils

............................. 3-1 3-2. Laboratory Testing of Pervious Materials

.................................... 3-2 6-1. Minimum Factors of Safety - Levee Slope Stability

............................. 6-4 7-1. Classification According to Construction Method of Levees Composed of Impervious and Semipervious Materials

.................................... 7-2 7-2. Embankment Construction Deficiencies

...................................... 7-6 8-1. Criteria for Pipelines Crossing Levees

....................................... 8-2 B-1. Factors Involved in Seepage Analyses

....................................... B-2 B-2. Methods for Determination of Design Parameters

.............................. B-3 B-3. Examples of Transformation Procedure

...................................... B-5 C-1. Summary of Distances to Effective Source of Seepage, Effective Lengths of Riverside Blankets, and Vertical Permeability of Riverside Blanket Materials at the Crest of 1950 High Water

.................................. C-2 C-2. Examples of Design of Seepage Berms

...................................... C-7 D-1. Categories of Base Soil Materials

.......................................... D-2 D-2. Criteria for Filters

...................................................... D-3 D-3. D 10

### and D 90

### Limits for Preventing Segregation

................................. D-3 F-1. Matching Pipe Size to Pump Size

.......................................... F-11 F-2. Crisafulli Pumps - Model CP 2 inch to 24 inch

................................ F-12 F-3. Marlow Self Priming Centrifugal Pumps

..................................... F-12 F-4. Capacity of Corrugated Metal Pipe Culverts

.................................. F-14 G-1. Initial Cement Content for Moisture Density Tests

............................. G-3 G-2. Durability Test Weight Loss Criteria

....................................... G-4 G-3. Unconfined Compressive Strength Criteria (ASTM D 1633)

...................... G-5 List of Figures
No. Figure Page 

### 3-1. Plasticity chart (ENG Form 4334

.......................................... 3-3 3-2. Example correlations of strength characteristic for fine-grained soils

................ 3-4 3-3. Example correlations for consolidation characteristics of fine-grained soils (after Kapp, ref. A-5e)

................................................. 3-5 3-4. Comparisons of Atterberg limits and natural water content

....................... 3-7 3-5. Example correlations for properties of coarse-grained soils

....................... 3-9 4-1. Plan of typical levee and borrow areas with traverse and foreshore

................. 4-3EM 1110-2-1913

30 Apr 2000

vi No. Figure Page 

### 5-1. Example of incorrect and correct berm length according to existing foundation conditions

........................................................... 5-2 5-2. Typical partially penetrating pervious toe trench

............................... 5-4 5-3. Typical pervious toe trench with collector pipe (Figure 5-6 shows trench details)

....... 5-5 5-4. Pervious toe trench located beneath landward slope

............................. 5-5 5-5. Special equipment for compacting sand in pervious toe trenches

.................... 5-6 5-6. Pervious toe trench with collector pipe

....................................... 5-7 5-7. Typical relief well

...................................................... 5-8 5-8. Embankment with through seepage

......................................... 5-9 5-9. Use of horizontal and inclined drainage layers to control seepage through an embankment

......................................................... 5-11 8-1. Typical sections, drainage structures through levees

............................ 8-5 8-2. Typical precast conduit (levees)

........................................... 8-5 8-3. Details of pipeline levee crossing

........................................... 8-9 8-4. Example of levee turnout

................................................. 8-11 8-5. Example of levee turnaround

.............................................. 8-11 8-6. Enlargements

......................................................... 8-13 8-7. I-type floodwall-levee enlargement

......................................... 8-14 8-8. Inverted T-type floodwall-levee enlargement

.................................. 8-15 8-9. Junction of levee and drainage structure

...................................... 8-16 B-1. Illustration of symbols used in Appendix B

................................... B-4 B-2. Transformation of top strata

.............................................. B-6 B-3. Effective seepage exit length for L3 

### = 4and d = 100 m or 100 ft

................... B-8 B-4. Relation between x3 

### for blocked or open exits and x 3 

### for L 3 

### = 4

.................... B-10 B-5. Equations for computation of underseepage flow and substratum pressures for Cases 1 through 4

..................................................... B-14 B-6. Equations for computation of underseepage flow and substratum pressures for Cases 5 and 6

........................................................ B-15 B-7. Equations for computation of underseepage and substratum pressures for Case 7

....... B-16 B-8. Ratio between head landward of levee and head at landside toe of levee for levees found on semipervious to stratum underlain by a pervious substratum

.............. B-18 C-1. Design of landside seepage berms on impervious top stratum

...................... C-4 D-1. Analysis of a gap-graded material

.......................................... D-5 D-2. Illustration of the design of a graded filter

.................................... D-7 E-1. Formulas and design curves for drainage trenches (ref. A-3b (2))

................... E-2 E-2. Example of design of a drainage trench

...................................... E-5 F-1. Sandbag barrier

....................................................... F-5 F-2. Flash board and box levee

................................................ F-6 F-3. Placement of polyethylene sheeting on temporary levee

.......................... F-7 F-4. Placement of polyethylene sheeting in the wet

................................. F-8 F-5. Prefabricated rubber pipe stoppers for outlet opening of a manhole

................. F-16 F-6. Prefabricated rubber pipe stoppers for outlet opening of a manhole

................. F-16 F-7. Typical manhole

....................................................... F-17 F-8. Adapting manhole for use as emergency pumping station

......................... F-18 F-9. Sealing top of manhole with wood

.......................................... F-19 F-10. Treatment of bottom of manhole

........................................... F-20 F-11. Suction line to pump from manhole

......................................... F-21 F-12. Ringing sand boils

...................................................... F-23EM 1110-2-1913 30 Apr 2000

vii No. Figure Page 

### G-1. Typical moisture-density curve

............................................ G-4 G-2. Stair-step method of slope protection

........................................ G-6 G-3. Relationship of slope, facing thickness, layer thickness, and horizontal layer width

...... G-7 G-4. Typical pug mill central plant

............................................. G-10 G-5. Mixing paddles of a twin-shaft, continuous-flow central mixing plant

............... G-10 G-6. Typical construction sequence

............................................. G-11 G-7. “Deadman” pulling vibratory sheepsfoot roller up the slope

....................... G-12 G-8. Transverse single-shaft rotary mixer

........................................ G-14 G-9. Bulk mechanical spreader

................................................ G-15EM 1110-2-1913 30 Apr 2000

1-1 

### Chapter 1 Introduction
1-1. Purpose The purpose of this manual is to present basic principles used in the design and construction of earth levees. 1-2. Applicability This manual applies to all Corps of Engineers Divisions and Districts having responsibility for designing and constructing levees. 1-3. References Appendix A contains a list of required and related publications pertaining to this manual. Unless otherwise noted, all references are available on interlibrary loan from the Research Library, ATTN: CEWES-IM-MI-R, U.S. Army Engineer Waterways Experiment Station, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199. 1-4. Objective The objective of this manual is to develop a guide for design and construction of levees. The manual is general in nature and not intended to supplant the judgment of the design engineer on a particular project. 1-5. General Considerations

a . General (1) The term levee as used herein is defined as an embankment whose primary purpose is to furnish flood protection from seasonal high water and which is therefore subject to water loading for periods of only a few days or weeks a year. Embankments that are subject to water loading for prolonged periods (longer than normal flood protection requirements) or permanently should be designed in accordance with earth dam criteria rather than the levee criteria given herein. (2) Even though levees are similar to small earth dams they differ from earth dams in the following important respects: (a) a levee embankment may become saturated for only a short period of time beyond the limit of capillary saturation, (b) levee alignment is dictated primarily by flood protection requirements, which often results in construction on poor foundations, and (c) borrow is generally obtained from shallow pits or from channels excavated adjacent to the levee, which produce fill material that is often heterogeneous and far from ideal. Selection of the levee section is often based on the properties of the poorest material that must be used. (3) Numerous factors must be considered in levee design. These factors may vary from project to project, and no specific step-by step procedure covering details of a particular project can be established. However, it is possible to present general, logical steps based on successful past projects that can be followed in levee design and can be used as a base for developing more specific procedures for any particular project.Such a procedure is given in Table 1-1. Information for implementing this procedure is presented in subsequent chapters.EM 1110-2-1913 30 Apr 2000

1-2 Table 1-1 Major and Minimum Requirements Step Procedure 1 Conduct geological study based on a thorough review of available data including analysis of aerial photographs. Initiate preliminary subsurface explorations. 2 Analyze preliminary exploration data and from this analysis establish preliminary soil profiles, borrow locations, and embankment sections. 3 Initiate final exploration to provide: a. Additional information on soil profiles. b. Undisturbed strengths of foundation materials. c. More detailed information on borrow areas and other required excavations. 4 Using the information obtained in Step 3: a. Determine both embankment and foundation soil parameters and refine preliminary sections where needed, noting all possible problem areas. b. Compute rough quantities of suitable material and refine borrow area locations. 5 Divide the entire levee into reaches of similar foundation conditions, embankment height, and fill material and assign a typical trial section to each reach. 6 Analyze each trial section as needed for: a. Underseepage and through seepage. b. Slope stability. c. Settlement. d. Trafficability of the levee surface. 7 Design special treatment to preclude any problems as determined from Step 6. Determine surfacing requirements for the levee based on its expected future use. 8 Based on the results of Step 7, establish final sections for each reach. 9 Compute final quantities needed; determine final borrow area locations. 10 Design embankment slope protection.


### (4) The method of construction must also be considered. In the past levees have been built by methods of compaction varying from none to carefully controlled compaction. The local economic situation also affects the selection of a levee section. Traditionally, in areas of high property values, high land use, and good foundation conditions, levees have been built with relatively steep slopes using controlled compaction, while in areas of lower property values, poor foundations, or high rainfall during the construction season, uncompacted or semicompacted levees with flatter slopes are more typical. This is evident by comparing the steep slopes of levees along the industrialized Ohio River Valley with levees along the Lower Mississippi River which have much broader sections with gentler slopes. Levees built with smaller sections and steeper slopes generally require more comprehensive investigation and analysis than do levees with broad sections and flatter slopes whose design is more empirical. Where rainfall and foundation conditions permit, the trend in design of levees is toward sections with steeper slopes. Levee maintenance is another factor that often has considerable influence on the selection of a levee section. b

. Levee types according to location . Levees are broadly classified according to the area they protect as either urban or agricultural levees because of different requirements for each. As used in this manual, urban and agricultural levees are defined as follows: (1) Urban levees. Levees that provide protection from flooding in communities, including their industrial, commercial, and residential facilities.EM 1110-2-1913 30 Apr 2000

1-3 

### (2) Agricultural levees. Levees that provide protection from flooding in lands used for agricultural purposes.

c . Levee types according to use . Some of the more common terms used for levees serving a specific purpose in connection with their overall purpose of flood protection are given in Table 1-2.

Table 1-2 Classification of Levees According to Use Type Definition Mainline and Levees that lie along a mainstream and its tributary levees tributaries, respectively. Ring levees Levees that completely encircle or “ring” an area subject to inundation from all directions. Setback levees Levees that are built landward of existing levees, usually because the existing levees have suffered distress or are in some way being endangered, as by river migration. Sublevees Levees built for the purpose of underseepage control. Sublevees encircle areas behind the main levee which are subject, during high-water stages, to high uplift pressures and possibly the development of sand boils. They normally tie into the main levee, thus providing a basin that can be flooded during high-water stages, thereby counterbalancing excess head beneath the top stratum within the basin. Sublevees are rarely employed as the use of relief wells or seepage berms make them unnecessary except in emergencies. Spur levees Levees that project from the main levee and serve to protect the main levee from the erosive action of stream currents. Spur levees are not true levees but training dikes.



### d

. Causes of Levee Failures . The principal causes of levee failure are (1) Overtopping. (2) Surface erosion. (3) Internal erosion (piping). (4) Slides within the levee embankment or the foundation soils.EM 1110-2-1913 30 Apr 2000

2-1 

### Chapter 2 Field Investigations
2-1. Preliminary and Final StageMany field investigations are conducted in two stages: a preliminary stage and a final (design) stage. Normally, a field investigation in the preliminary stage is not extensive since its purpose is simply to providegeneral information for project feasibility studies. It will usually consist of a general geological reconnaissance with only limited subsurface exploration and simple soil tests. In the design stage, more comprehensive exploration is usually necessary, with more extensive geological reconnaissance, borings, test pits, and possibly geophysical studies. The extent of the field investigation depends on several factors. Table 2-1 lists these factors together with conditions requiring extensive field investigations and design studies. Sometimes field tests such as vane shear tests, groundwater observations, and field pumping tests are necessary. Table 2-2 summarizes, in general, the broad features of geologic and subsurface investigations. Section I Geological Study 2-2. Scope A geological study usually consists of an office review of all available geological information on the area of interest and an on-site (field) survey. Since most levees are located in alluvial floodplains, the distribution and engineering characteristics of alluvial deposits in the vicinity of proposed levees must be evaluated. The general distribution, nature, and types of floodplain deposits are directly related to changes in the depositional environment of the river and its tributaries. Each local area in the floodplain bears traces of river action, and the alluvial deposits there may vary widely from those in adjacent areas. The general nature and distribution of sediments can be determined through a study of the pattern of local river changes as a basis for selection of boring locations.

Table 2-1 Factors Requiring Intensive Field Investigations and Design Studies Factor Field Investigations and Design Studies Should be more Extensive Where: Previous experience There is little or no previous experience in the area particularly with respect to levee performance Consequences of failure Consequences of failure involving life and property are great (urban areas for instance) Levee height Levee heights exceed 3 m (10 ft) Foundation conditions Foundation soils are weak and compressible Foundation soils are highly variable along the alignment Potential underseepage problems are severe Foundation sands may be liquefaction susceptible Duration of high water High water levels against the levee exist over relatively long periods Borrow materials Available borrow is of low quality, water contents are high, or borrow materials are variable along the alignment Structure in levees Reaches of levees are adjacent to concrete structuresEM 1110-2-1913 30 Apr 2000

2-2 Table 2-2 Stages of Field Investigations 1. Investigation or analysis produced by field reconnaissance and discussion with knowledgeable people is adequate for design

where:
a . Levees are 3 m (10 ft) or less in height. b . Experience has shown foundations to be stable and presenting no underseepage problems. Use standard levee section developed through experience. 2. Preliminary geological investigation :

a . Office study : Collection and study of (1) Topographic, soil, and geological maps. (2) Aerial photographs. (3) Boring logs and well data. (4) Information on existing engineering projects. b

. Field survey : Observations and geology of area, documented by written notes and photographs, including such features as: (1) Riverbank slopes, rock outcrops, earth and rock cuts or fills. (2) Surface materials. (3) Poorly drained areas. (4) Evidence of instability of foundations and slopes. (5) Emerging seepage. (6) Natural and man-made physiographic features. 3. Subsurface exploration and field testing and more detailed geologic study : Required for all cases except those in 1 above. Use to decide the need for and scope of subsurface exploration and field testing:
a
. Preliminary phase : (1) Widely but not necessarily uniformly spaced disturbed sample borings (may include split-spoon penetration tests). (2) Test pits excavated by backhoes, dozers, or farm tractors. (3) Geophysical surveys (e.g., seismic or electrical resistivity) or cone penetrometer test to interpolate between widely spaced borings. (4) Borehole geophysical tests. b

. Final phase : (1) Additional disturbed sample borings. (2) Undisturbed sample borings. (3) Field vane shear tests for special purposes. (4) Field pumping tests (primarily in vicinity of structures). (5) Water table observations (using piezometers) in foundations and borrow areas.



### 2-3. Office Study The office study begins with a search of available information, such as topographic, soil, and geological maps and aerial photographs. Pertinent information on existing construction in the area should be obtained. This includes design, construction, and performance data on utilities, highways, railroads, and hydraulic structures. Available boring logs should be secured. Federal, state, county, and local agencies and private organizations should be contacted for information. The GIS (Geographic Information System) became used extensively in major range of projects. It is capable of compiling large multi-layered data bases, interactively analyzing and manipulating those data bases, and generating and displaying resultant thematic maps and statistics to aid in engineering management decisions. Federal, state, and private organizations provide free internet access to such systems. Table 2-3 shows some of the contour maps GIS systems provide.EM 1110-2-1913 30 Apr 2000

2-3 Table 2-3 Types of Contour Maps Contour Type Uses Geologic Structure Contour maps in which each line represents GIS can produce these maps based on the selection Elevation Maps the elevation of the top of a geological material of one of four structure parameters or facies Geologic formations Contours the top of a user-defined geologic formation Blow counts Contours the top of a structure identified by the A blow count is defined as the number of standard first, second, or third occurrence of a specified blows required to advance a sampling device into range of blow counts 150 mm (6 in.) of soil Soil units Contours the top of a structure identified by the first, second, or third occurrence of one or more soil types Fluid level elevation - Show elevation data (hydraulic head) from Help to evaluate the direction of ground water flow water table contour unconfined water bearing units where the fluid and the energy gradient under which it is flowing maps surface is in equilibrium with atmospheric pressure Fluid level elevation - Show elevation data from confined water potentiometric surface bearing units where the fluid surface is under maps pressure because of the presence of a confining geologic unit Hydraulic conductivity Show the rate of water flow through soil under GIS stores vertical and horizontal conductivity data a unit gradient per unit area for up to five water bearing zones Portray the variations in the water-bearing Necessary parameter for computing ground water properties of materials which comprise each flow rates, which is important since groundwater water bearing zone velocity exerts a major control on plume shape


### 2-4. Field Survey The field survey is commenced after becoming familiar with the area through the office study. Walking the proposed alignment and visiting proposed borrow areas are always an excellent means of obtaining usefulinformation. Physical features to be observed are listed in Table 2-2. These items and any others of significance should be documented by detailed notes, supplemented by photographs. Local people or organizations having knowledge of foundation conditions in the area should be interviewed. 2-5. Report When all available information has been gathered and assimilated, a report should be written that in essence constitutes a geological, foundation, and materials evaluation report for the proposed levee. All significant factors that might affect the alignment and/or design should be clearly pointed out and any desirable changes in alignment suggested. All maps should be to the same scale, and overlays of maps, e.g., topography and soil type, aerial photograph and topography, etc., to facilitate information correlation is desirable. The development of a project GIS will simplify and expedite consistently georeferenced map products.EM 1110-2-1913 30 Apr 2000

2-4 

### Section II Subsurface Exploration 2-6. General

a . Because preliminary field investigations usually involve only limited subsurface exploration, only portions of the following discussion may be applicable to the preliminary stage, depending on the nature of the project. b . The subsurface exploration for the design stage generally is accomplished in two phases, which may be separate in sequence, or concurrent: (1) Phase 1, the main purpose of which is to better define the geology of the area, the soil types present and to develop general ideas of soil strengths and permeabilities;(2) Phase 2, provides additional information on soil types present and usually includes the taking of undisturbed samples for testing purposes. 2-7. Phase 1 Exploration Phase 1 exploration consists almost entirely of disturbed sample borings and perhaps test pits excavated with backhoes, dozers, farm tractors, etc., as summarized in Table 2-4, but may also include geophysical surveys which are discussed later.

Table 2-4 Phase I Boring and Sampling Techniques Technique Remarks 1. Disturbed sample borings
a . Split-spoon or standard 1-a. Primarily for soil identification but permits estimate of shear strength of penetration test clays and crude estimate of density of sands; see paragraph 5-3d of EM 1110-1-1906Preferred for general exploration of levee foundations; indicates need and locations for undisturbed samples b . Auger borings 1-b. Bag and jar samples can be obtained for testing 2. Test pits 2. Use backhoes, dozers, and farm tractors 3. Trenches 3. Occasionally useful in borrow areas and levee foundations


### 2-8. Phase 2 Exploration Phase 2 subsurface exploration consists of both disturbed and undisturbed sample borings and also may include geophysical methods. Undisturbed samples for testing purposes are sometimes obtained by handcarving block samples from test pits but more usually by rotary and push-type drilling methods (using samplers such as the Denison sampler in extremely hard soils or the thin-walled Shelby tube fixed piston sampler in most soils). Samples for determining consolidation and shear strength characteristics and values of density and permeability should be obtained using undisturbed borings in which 127-mm- (5-in.-) diameter samples are taken in cohesive materials and 76.2-mm- (3-in.-) diameter samples are taken in cohesionless materials. EM 1110-1-1906 gives details of drilling and sampling techniques.EM 1110-2-1913 30 Apr 2000

2-5 

### 2-9. Borings

a . Location and spacing . The spacing of borings and test pits in Phase 1 is based on examination of airphotos and geological conditions determined in the preliminary stage or known from prior experience in the area, and by the nature of the project. Initial spacing of borings usually varies from 60 to 300 m (nominally 200 to 1,000 ft) along the alignment, being closer spaced in expected problem areas and wider spaced in nonproblem areas. The spacing of borings should not be arbitrarily uniform but rather should be based on available geologic information. Borings are normally laid out along the levee centerline but can be staggered along the alignment in order to cover more area and to provide some data on nearby borrow materials. At least one boring should be located at every major structure during Phase 1. In Phase 2, the locations of additional general sample borings are selected based on Phase 1 results. Undisturbed sample borings are located where data on soil shear strength are most needed. The best procedure is to group the foundation profiles developed on the basis of geological studies and exploration into reaches of similar conditions and then locate undisturbed sample borings so as to define soil properties in critical reaches. b

. Depth . Depth of borings along the alignment should be at least equal to the height of proposed levee at its highest point but not less than 3 m (nominally 10 ft). Boring depths should always be deep enough to provide data for stability analyses of the levee and foundation. This is especially important when the levee is located near the riverbank where borings must provide data for stability analyses involving both levee foundation and riverbank. Where pervious or soft materials are encountered, borings should extend through the permeable material to impervious material or through the soft material to firm material. Borings at structure locations should extend well below invert or foundation elevations and below the zone of significant influence created by the load. The borings must be deep enough to permit analysis of approach and exit channel stability and of underseepage conditions at the structure. In borrow areas, the depth ofexploration should extend several feet below the practicable or allowable borrow depth or to the groundwater table. If borrow is to be obtained from below the groundwater table by dredging or other means, borings should be at least 3 m (nominally 10 ft) below the bottom of the proposed excavation. 2-10. Geophysical Exploration

a . It is important to understand the capabilities of the different geophysical methods, so that they may be used to full advantage for subsurface investigations. Table 2-5 summarizes those geophysical methods most appropriate to levee exploration. These methods are a fairly inexpensive means of exploration and are very useful for correlating information between borings which, for reasons of economy, are spaced at fairly wide intervals. Geophysical data must be interpreted in conjunction with borings and by qualified, experienced personnel. Because there have been significant improvements in geophysical instrumentation and interpretation techniques in recent years, more consideration should be given to their use. b . Currently available geophysical methods can be broadly subdivided into two classes: those accomplished entirely from the ground surface and those which are accomplished from subsurface borings. Applicable geophysical ground surface exploration methods include: (1) seismic methods, (2) electrical resistivity, (3) natural potential (SP) methods, (4) electromagnetic induction methods, and (5) ground penetrating radar. Information obtained from seismic surveys includes material velocities, delineation of interfaces between zones of differing velocities, and the depths to these interfaces. The electrical resistivity survey is used to locate and define zones of different electrical properties such as pervious and impervious zones or zones of low resistivity such as clayey strata. Both methods require differences in properties of levee and/or foundation materials in order to be effective. The resistivity method requires a resistivity contrast between materials being located, while the seismic method requires contrast in wave transmission velocities. Furthermore, the seismic refraction method requires that any underlying stratum transmit wavesEM 1110-2-1913 30 Apr 2000

2-6 Table 2-5 Applicable Geophysical Methods of Exploration a Suspected In Situ Mate rial Subsurface Top of Fault Voids or Cavity Elastic Moduli Boundaries, Conduits Landfill Bedrock Detection Detection (Velocities) Dip, ... and Vessels Boundaries Seismic W S W S Refraction Seismic S S S W Reflection Natural S Potential (SP) DC Resistivity S S S S S W Electro- S S W W Magnetics Ground S S S S S S Penetrating Radar Gravity S S S Magnetics S S
W - works well in most materials and natural configurations. S - works under special circumstances of favorable materials or configurations. Blank - not recommended. After EM 1110-1-1802. a 

### at a higher velocity than the overlying stratum. Difficulties arise in the use of the seismic method if the surface terrain and/or layer interfaces are steeply sloping or irregular instead of relatively horizontal and smooth. Therefore, in order to use these methods, one must be fully aware of what they can and cannot do. EM 1110-1-1802 describes the use of both seismic refraction and electrical resistivity. Telford et al. (1990) is a valuable, general text on geophysical exploration. Applicable geophysical exploration methods based on operation from the ground surface are summarized in Table 2-5. A resistivity survey measures variations in potential of an electrical field within the earth by a surface applied current. Variation of resistivity with depth is studied by changing electrode spacing. The data is then interpreted as electrical resistivity expressed as a function of depth. (Telford et al. 1990; EM 1110-1-1802)

c . Downhole geophysical logging can be used with success in correlating subsurface soil and rock stratification and in providing quantitative engineering parameters such as porosity, density, water content, and moduli. They also provide valuable data for interpreting surface geophysical data. The purpose in using these methods is not only to allow cost savings, but the speed, efficiency and often much more reliable information without lessening the quality of the information obtained. Electromagnetic (EM) induction surveys use EM transmitters that generate currents in subsurface materials. These currents produce secondary magnetic fields detectable at the surface. Simple interpretation techniques are advantages of these methods, making EM induction techniques particularly suitable for horizontal profiling. EM horizontal profiling surveys are useful for detecting anomalous conditions along the centerline of proposed levee construction or along existing levees. Self potential (SP) methods are based on change of potential of ground by human action or alteration of original condition. Four electric potentials due to fluid flow, electrokinetic or streaming, liquid junction or diffusion, mineralizaion, and solution differing concentration, are known.EM 1110-2-1913 30 Apr 2000

2-7 

### The qualitative application of this method is relatively simple and serves best for detection of anomalous seepage through, under, or around levees (Butler and Llopis, 19909; EM 1110-1-1802).

Section III Field Testing 2-11

. Preliminary Strength Estimates It is often desirable to estimate foundation strengths during Phase 1 of the exploration program. Various methods of preliminary appraisal are listed in Table 2-6.

Table 2-6 Preliminary Appraisal of Foundation Strengths Method Remarks 1. Split-spoon penetration 1-a. Unconfined compressive strength in hundreds kPa (or tons per square foot), of clay is about

resistance 1/8 of number of blows per 0.3 m (1 ft), or N/8, but considerable scatter must be expected. Generally not helpful where N is low 1-b. In sands, N values less than about 15 indicate low relative densities. N values should not be used to estimate relative densities for earthquake design 2. Natural water content of 2. Useful when considered with soil classification, and previous experience is available disturbed or general type samples 3. Hand examination of 3. Useful where experienced personnel are available who are skilled in estimating soil shear

disturbed samples strengths 4. Position of natural water 4-a. Useful where previous experience is available contents relative to liquid and plastic limits 4-b. If natural water content is close to plastic limit foundation shear strength should be high 4-c. Natural water contents near liquid limit indicate sensitive soil usually with low shear strengths 5. Torvane or pocket pene- 5. Easily performed and inexpensive but may underestimate actual values ; useful only for trometer tests on intact preliminary strength classifications portions of general samples

or on walls of test trenches


### 2-12. Vane Shear Tests Where undisturbed samples are not being obtained or where samples of acceptable quality are difficult to obtain, in situ vane shear tests may be utilized as a means of obtaining undrained shear strength. The apparatus and procedure for performing this test are described in ASTM D 2573. The results from this test may be greatly in error where shells or fibrous organic material are present. Also, test results in high plasticity clays must be corrected using empirical correction factors as given by Bjerrum (1972) (but these are not always conservative). 2-13. Groundwater and Pore Pressure Observations Piezometers to observe groundwater fluctuations are rarely installed solely for design purposes but should always be installed in areas of potential underseepage problems. The use and installation of piezometers are described in EM 1110-2-1908. Permeability tests should always be made after installation of theEM 1110-2-1913 30 Apr 2000

2-8 

### piezometers; these tests provide information on foundation permeability and show if piezometers are functioning. Testing and interpretation procedures are described in EM 1110-2-1908. 2-14. Field Pumping Tests The permeability of pervious foundation materials can often be estimated with sufficient accuracy by using existing correlations with grain-size determination; see TM 5-818-5. However, field pumping tests are the most accurate means of determining permeabilities of stratified in situ deposits. Field pumping tests are expensive and usually justified only at sites of important structures and where extensive pressure relief well installations are planned. The general procedure is to install a well and piezometers at various distances from the well to monitor the resulting drawdown during pumping of the well. Appendix III of TM 5-818-5 gives procedures for performing field pumping tests.EM 1110-2-1913 30 Apr 2000

3-1 

### Chapter 3 Laboratory Testing

3-1. General

a. Reference should be made to EM 1110-1-1906 for current soil testing procedures, and to EM 1110-2- 1902 for applicability of the various shear strength tests in stability analyses. b . Laboratory testing programs for levees will vary from minimal to extensive, depending on the nature and importance of the project and on the foundation conditions, how well they are known, and whether existing experience and correlations are applicable. Since shear and other tests to determine the engineering properties of soils are expensive and time-consuming, testing programs generally consist of water contentand identification tests on most samples and shear, consolidation, and compaction tests only on representative samples of foundation and borrow materials. It is imperative to use all available data such as geological and geophysical studies, when selecting representative samples for testing. Soil tests that may be included in laboratory testing programs are listed in Table 3-1 for fine-grained cohesive soils and in Table 3-2 for pervious soils, together with pertinent remarks on purposes and scope of testing.

Table 3-1 Laboratory Testing of Fine-Grained Cohesive Soils Test Remarks Visual classification and water On all samples content determinations Atterberg limits On representative samples of foundation deposits for correlation with shear or consolidation parameters, and borrow soils for comparison with natural water contents, or correlations with optimum water content and maximum densities Permeability Not required; soils can be assumed to be essentially impervious in seepage analyses Consolidation Generally performed on undisturbed foundation samples only where:
a . Foundation clays are highly compressible b . Foundations under high levees are somewhat compressible
c . Settlement of structures within levee systems must be accurately estimated Not generally performed on levee fill; instead use allowances for settlement within levees based on type of compaction. Sometimes satisfactory correlations of Atterberg limits with coefficient of consolidation can be used. Compression index can usually be estimated from water content. Compaction a . Required only for compacted or semi-compacted levees b . Where embankment is to be fully compacted, perform standard 25-blow compaction tests
c . Where embankment is to be semi-compacted, perform 15-blow compaction tests Shear strength a . Unconfined compression tests on saturated foundation clays without joints or slickensides b . Q triaxial tests appropriate for foundation clays, as undrained strength generally governs stability
c . R triaxial and S direct shear: Generally required only when levees are high and/or foundations are weak, or at locations where structures exist in levees d

. Q, R, and S tests on fill materials compacted at appropriate water contents to densities

resulting from the expected field compaction effortEM 1110-2-1913 30 Apr 2000

3-2 Table 3-2 Laboratory Testing of Pervious Materials Test Remarks Visual classification Of all jar samples In situ density Of Shelby-tube samples of foundation sands where liquefaction susceptibility must be evaluated determinations Relative density Maximum and minimum density tests should be performed in seismically active areas to determine in situ relative densities of foundation sands and to establish density control of sand fills Gradation On representative foundation sands:
a . For correlating grain-size parameters with permeability or shear strength b . For size and distribution classifications pertinent to liquefaction potential Permeability Not usually performed. Correlations of grain-size parameters with permeability or shear strength used. Where underseepage problems are serious, best guidance obtained by field pumping tests Consolidation Not usually necessary as consolidation under load is insignificant and occurs rapidly Shear strength For loading conditions other than dynamic, drained shear strength is appropriate. Conservative values of φ ’ can be assumed based on S tests on similar soils. In seismically active areas, cyclic triaxial tests may be performed



### 3-2. Classification and Water Content Determinations After soil samples have been obtained in subsurface exploration of levee foundations and borrow areas, the first and essential step is to make visual classifications and water content determinations on all samples (except that water content determinations should not be made on clean sands and gravels). These samples may be jar or bag samples obtained from test pits, disturbed or undisturbed drive samples, or auger samples.Field descriptions, laboratory classifications, and water content values are used in preparing graphic representations of boring logs. After examining these data, samples of fine-grained soils are selected for Atterberg limits tests, and samples of coarse-grained soils for gradation tests. Section I Fine-Grained Soils 3-3. Use of CorrelationsComparisons of Atterberg limits values with natural water contents of foundation soils and use of the plasticity chart itself (Figure 3-1), together with split-spoon driving resistance, geological studies, and previous experience often will indicate potentially weak and compressible fine-grained foundation strata and thus theneed for shear and perhaps consolidation tests. In some cases, in the design of low levees on familiar foundation deposits for example, correlations between Atterberg limits values and consolidation or shear strength characteristics may be all that is necessary to evaluate these characteristics. Examples of correlations among Atterberg limits values, natural water content, shear strength and consolidation characteristics are shown in Figures 3-2 and 3-3. Correlations based on local soil types and which distinguish between normally and overconsolidated conditions are preferable. Such correlations may also be used to reduce the number of testsrequired for design of higher levees. As optimum water content may in some cases be correlated with Atterberg limits, comparisons of Atterberg limits and natural water contents of borrow soils as shown in Figure 3-4 can indicate whether the borrow materials are suitable for obtaining adequate compaction.300 u A

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### 3-4. Shear Strength EM 1110-2-1913 30 Apr 2000

Approximate shear strengths of fine-grained cohesive soils can be rapidly determined on undisturbed foundation samples, and occasionally on reasonably intact samples from disturbed drive sampling, using simple devices such as the pocket penetrometer, laboratory vane shear device, or the miniature vane shear device (Torvane). To establish the reliability of these tests, it is desirable to correlate them with unconfined compression tests. Unconfined compression tests are somewhat simpler to perform than Q triaxial compression tests, but test results exhibit more scatter. Unconfined compression tests are appropriate primarily for testing saturated clays which are not jointed or slickensided. Of the triaxial compression tests, the Q test is the one most commonly performed on foundation clays, since the in situ undrained shear strength generally controls embankment design on such soils. However, where embankments are high, stage construction is being considered, or important structures are located in a levee system, R triaxial compression tests and S direct shear tests should also be performed. 

### 3-5. Consolidation Consolidation tests are performed for those cases listed in Table 3-1. In some locations correlations of liquid limit and natural water content with coefficient of consolidation, compression index, and coefficient of secondary compression can be used satisfactorily for making estimates of consolidation of foundation clays under load. 

### 3-6. Permeability Generally there is no need for laboratory permeability tests on fine-grained fill materials, nor on surface clays overlying pervious foundation deposits. In underseepage analyses, simplifying assumptions must be made relative to thickness and soil type of fine-grained surface blankets. Furthermore, animal burrows, root channels, and other discontinuities in surface blankets can significantly affect the overall effective permeability. Therefore, an average value of the coefficient of permeability based on the dominant soil type (Appendix B) is generally of sufficient accuracy for use in underseepage analyses, and laboratory tests are not essential. 

### 3-7. Compaction Tests The type and number of compaction tests will be influenced by the method of construction and the variability of available borrow materials. The types of compaction tests required are summarized in Table 3-1.

3-7EM 1110-2-1913 30 Apr 2000

3-8 

### Section II Coarse-Grained Soils 3-8. Shear Strength When coarse-grained soils contain few fines, the consolidated drained shear strength is appropriate for use in all types of analyses. In most cases, conservative values of the angle of internal friction ( φ ) can be assumed from correlations such as those shown in Figure 3-5, and no shear tests will be needed. 3-9. Permeability To solve the problem of underseepage in levee foundations, reasonable estimates of permeability of pervious foundation deposits are required. However, because of difficulty and expense in obtaining undisturbed samples of sands and gravels, laboratory permeability tests are rarely performed on foundation sands. Instead, field pumping tests or correlations such as that of Figure 3-5 developed between a grain-size parameter (such as D ) and the coefficient of permeability, k , are generally utilized. 10 

### 3-10. Density Testing of Pervious Fill Maximum density tests on available pervious borrow materials should be performed in accordance with ASTM D 4253 so that relative compaction requirements for pervious fills may be checked in the field when required by the specification. Due to the inconsistencies in duplicating minimum densities (ASTM D 4254), relative density may not be used. Factors such as (but not limited to) site specific materials, availability of testing equipment and local practice may make it more practical to utilize methods other than ASTM D 4253 and ASTM D 4254 to control the degree of compaction of cohesionless material. The other methods used include comparison of in-place density to either the maximum Proctor density or the maximum density obtained by ASTM 4253 (if vibratory table is available).75 80 90 45 U) IZl IZl**~40** IZl 

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Figure 3-5. Example correlations for properties of coarse-grained soils

3-9EM 1110-2-1913 30 Apr 2000

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Figure 3-5. (Concluded)

3-10EM 1110-2-1913 30 Apr 2000

4-1 

### Chapter 4 Borrow Areas

4-1. General In the past borrow areas were selected largely on the basis of material types and quantities and haul distances. Today, borrow areas receive much more attention and must be carefully planned and designed, because of considerations such as environmental aspects, increasing land values, and greater recognition of the effects of borrow areas with respect to underseepage, uplift pressures, overall levee stability, and erosion. The following paragraphs discuss some factors involved in locating and using borrow areas. 4-2. Available Borrow Material a. Material type . Almost any soil is suitable for constructing levees, except very wet, fine-grained soils or highly organic soils. In some cases, though, even these soils may be considered for portions of levees. Accessibility and proximity are often controlling factors in selecting borrow areas, although the availability of better borrow materials involving somewhat longer haul distances may sometimes lead to the rejection of poorer but more readily available borrow. b. Natural water content . Where compacted levees are planned, it is necessary to obtain borrow material with water content low enough to allow placement and adequate compaction. The cost of drying borrow material to suitable water contents can be very high, in many cases exceeding the cost of longer haul distances to obtain material that can be placed without drying. Borrow soils undergo seasonal water content variations; hence water content data should be based on samples obtained from borrow areas in that season of the year when levee construction is planned. Possible variation of water contents during the construction season should also be considered. 4-3. General Layout Generally, the most economical borrow scheme is to establish pits parallel and adjacent to the levee. If a levee is adjacent to required channel excavation, levee construction can often utilize material from channel excavation. Large centralized borrow areas are normally established only for the construction of urban levees, where adjacent borrow areas are unavailable. Long, shallow borrow areas along the levee alignment are more suitable, not only because of the shorter haul distance involved, but also because they better satisfy environmental considerations. a. Location . Where possible, borrow area locations on the river side of a levee are preferable as borrow pits. Borrow area locations within the protected area are less desirable environmentally, as well as generally being more expensive. Riverside borrow locations in some areas will be filled eventually by siltation, thereby obliterating the man-made changes in the landscape. While riverside borrow is generally preferable, required landside borrow from ponding areas, ditches, and other excavations should be used wherever possible. A berm should be left in place between the levee toe and the near edge of the borrow area. The berm width depends primarily on foundation conditions, levee height, and amount of land available. Its width should be established by seepage analyses where pervious foundation material is close to the bottom of the borrow pit and by stability analyses where the excavation slope is near the levee. Minimum berm widths used frequently in the past are 12.2 m (40 ft) riverside and 30.5 m (100 ft) landside, but berm widths should be the maximum practicable since borrow areas may increase the severity of underseepage effects. In borrow area excavation, an adequate thickness of impervious cover should be left over underlyingEM 1110-2-1913 30 Apr 2000

4-2 

### pervious material. For riverside pits a minimum of 0.91 m (3 ft) of cover should be left in place, and for landside pits the cover thickness should be adequate to prevent the formation of boils under expected hydraulic heads. Topsoil from borrow and levee foundation stripping can be stockpiled and spread over the excavated area after borrow excavation has been completed. This reinforces the impervious cover and provides a good base for vegetative growth. b. Size and shape . It is generally preferable to have riverside borrow areas “wide and shallow” as opposed to “narrow and deep.” While this may require extra right-of-way and a longer haul distance, the benefits derived from improved underseepage, hydraulic, and environmental conditions usually outweigh the extra cost. In computing required fill quantities, a shrinkage factor of at least 25 percent should be applied (i.e., borrow area volumes should be at least 125 percent of the levee cross-section volume). This will allow for material shrinkage, and hauling and other losses. Right-of-way requirements should be established about 4.6 to 6.1 m (15 to 20 ft) beyond the top of the planned outer slope of the borrow pit. This extra right-of-way will allow for flattening or caving of the borrow slopes, and can provide maintenance borrow if needed later. 4-4. Design and Utilization a. Slopes . Excavation slopes of borrow areas should be designed to assure stability. This is particularly important for slopes adjacent to the levee but could also be important for any slope whose top is near the right-of-way limits. Borrow area slopes must also be flat enough to allow mowing, if required. Also, where landside pits are to be placed back into cultivation, changes in grade must be gentle enough to allow farm equipment to operate safely. The slopes of the upstream and downstream ends of riverside pits should be flat enough to avoid erosion when subjected to flow at high water stages. b. Depths . Depths to which borrow areas are excavated will depend upon factors such as (1) groundwater elevation, (2) changes at depth to undesirable material, (3) preservation of adequate thickness of riverside blanket, and (4) environmental considerations. c. Foreshore . The foreshore is that area between the riverside edge of the borrow area and the riverbank as shown in Figure 4-1. If a foreshore is specified (i.e., the borrow excavation is not to be cut into the riverbank), it should have a substantial width, say 61 m (200 ft) or more, to help prevent migration of the river channel into the borrow area. d. Traverse . A traverse is an unexcavated zone left in place at intervals across the borrow area (Figure 4-1). Traverses provide roadways across the borrow area, provide foundations for transmission towers and utility lines, prevent less than bank-full flows from coursing unchecked through the borrow area, and encourage material deposition in the borrow area during high water. Experience has shown that when traverses are overtopped or breached, severe scour damage can result unless proper measures are taken in their design. Traverse heights should be kept as low as possible above the bottom of the pit when they will be used primarily as haul roads. In all cases, flat downstream slopes (on the order of 1V and 6H to 10H) should be specified to minimize scour from overtopping. If the traverse carries a utility line or a public road, even flatter slopes and possibly stone protection should be considered. e. Drainage . Riverside borrow areas should be so located and excavated that they will fill slowly on a rising river and drain fully on a falling river. This will minimize scour in the pit when overbank river stages occur, promote the growth of vegetation, and encourage silting where reclamation is possible. The bottom of riverside pits should be sloped to drain away from the levee. Culvert pipes should be provided through traverses, and foreshore areas should be ditched through to the river as needed for proper drainage. Landside pits should be sloped to drain away from or parallel to the levee with ditches provided as necessary to outletRIVER

VARIES ---o-l BORROW AREA

BORROW

AREA VARIE.S w w EM 1110-2-1913 30 Apr 2000**f---~c:~---1** ..J

Figure 4-1. Plan of typical levee and borrow areas with traverse and foreshore
points. Gravity outlets or pump stations should be located so as to minimize lengths of flow paths within the pit area. 

## f Flow conditions. To avoid damage from confined or restricted flow through the riverside borrow areas, obstructions or impediments to smooth and uniform flow should be removed if possible, or else protective measures must be taken. Riverside borrow areas should be made as uniform in width and grade as possible, avoiding abrupt changes. Removal of obstructions that could cause concentrated flow includes degradation of old levee remnants and of narrow high ground ridges beyond the borrow area, as well as removal of timber from traverses and from foreshore areas immediately adjacent to the borrow area. Obstructions to flow that cannot be removed include transmission towers, bridge piers, and other permanent structures near the levee. In such areas, stone protection should be provided for the levee or borrow area slopes if scour damage is considered probable. 

### g. Environmental aspects. The treatment of borrow areas after excavation to satisfy aesthetic and environmental considerations has become standard practice. The extent of treatment will vary according to the type and location of a project. Generally, projects near urban areas or where recreational areas are to be developed will require more elaborate treatment than those in sparsely populated agricultural areas. Minimum treatment should include proper drainage, topographic smoothing, and the promotion of conditions conducive to vegetative growth. Insofar as practicable, borrow areas should be planted to conform to the surrounding landscape. Stands of trees should be left remaining on lands ide borrow areas if at all possible, and excavation procedures should not leave holes, trenches, or abrupt slopes. Restoration of vegetative growth is important for both landside and riverside pits as it is not only pleasing aesthetically but serves as protection against erosion. Willow trees can aid considerably in drying out boggy areas. Riverside pits should not be excavated so deep that restored grass cover will be drowned out by long submergence.
4-3EM 1110-2-1913 30 Apr 2000

4-4 

### Agencies responsible for maintenance of completed levees should be encouraged to plant and maintain vegetation, including timber, in the borrow areas. It is desirable that riverside borrow pits be filled in by natural processes, and frequent cultivation of these areas should be discouraged or prohibited, if possible, until this has been achieved. Guidelines for landscape planting are given in EM 1110-2-301. h. Clearing, grubbing, and stripping . Borrow areas should be cleared and grubbed to the extent needed to obtain fill material free of objectionable matter, such as trees, brush, vegetation, stumps, and roots. Subareas within borrow areas may be specified to remain untouched to preserve standing trees and existing vegetation. Topsoil with low vegetative cover may be stripped and stockpiled for later placement on outer landside slopes of levees and seepage berms.EM 1110-2-1913 30 Apr 2000

5-1 

### Chapter 5 Seepage Control

Section I Foundation Underseepage 5-1. General Without control, underseepage in pervious foundations beneath levees may result in (a) excessive hydrostatic p ressures beneath an impervious top stratum on the landside, (b) sand boils, and (c) piping beneath the levee itse lf. Underseepage problems are most acute where a pervious substratum underlies a levee and extend s both landward and riverward of the levee and where a relatively thin top stratum exists on the landside o f the levee. Principal seepage control measures for foundation underseepage are (a) cutoff trenches, (b) riverside impervious blankets, (c) landside seepage berms, (d) pervious toe trenches, and (e) pressure relief wells

. T hese met hods will be discussed generally in the following paragraphs. Detailed design guidance is given in Appendixes B and C. Turnbull and Mansur (1959) have proposed control measures for underseepage also. Additional information on seepage control in earth foundations including cutoffs, impervious blankets , seepage berms, relief wells and trench drains is given in EM 1110-2-1901 and EM 1110-2-1914. 5-2. Cutoffs Acutoff beneath a levee to block seepage through pervious foundation strata is the most positive means o f eliminating seepa ge problems. Positive cutoffs may consist of excavated trenches backfilled with compacted earth or slurry trenches usually located near the riverside toe. Since a cutoff must penetrate approximatel y 95 percent or more of the thickness of pervious strata to be effective, it is not economically feasible to construct cutoffs where pervious strata are of considerable thickness. For this reason cutoffs will rarely be economicalwhere they must penetrate more than 12.2 m (40 ft). Steel sheet piling is not entirely watertight due to leakage at the interlocks but can significantly reduce the possibility of piping of sand strata in th e foundation. Open trench excavations can be readily made above the water table, but if they must be mad e below the water table, well point systems will be required. Cutoffs made by the slurry trench metho d (referenceAppendix A) can be made without a dewatering system, and the cost of this type of cutoff should be favorable in many cases in comparison with costs of compacted earth cutoffs. 5-3. Riverside Blankets Levees a re frequently situated on foundations having natural covers of relatively fine-grained imperviou s to semipervi ous soils overlying pervious sands and gravels. These surface strata constitute impervious o r s emipervious blankets when considered in connection with seepage control. If these blankets are continuous andex tend riverward for a considerable distance, they can effectively reduce seepage flow and seepag e pre ssures landside of the levee. Where underseepage is a problem, riverside borrow operations should b e limit ed in depth to prevent breaching the impervious blanket. If there are limited areas where the blanket beco mesthin or pinches out entirely, the blanket can be made effective by placing impervious materials i n theseareas. The effectiveness of the blanket depends on its thickness, length, distance to the levee riverside toe, and p ermeability and can be evaluated by flow-net or approximate mathematical solutions, as show n in Appendix B. Protection of the riverside blanket against erosion is important.EM 1110-2-1913 30 Apr 2000


### 5-4. Landside Seepage Berms



### a. General. If uplift pressures in pervious deposits underlying an impervious top stratum landward of a levee become greater than the effective weight of the top stratum, heaving and rupturing of the top stratum may occur, resulting in sand boils. The construction of landside berms (where space is available) can eliminate this hazard by providing (a) the additional weight needed to counteract these upward seepage forces and (b) the additional length required to reduce uplift pressures at the toe of the berm to tolerable values. Seepage berms may reinforce an existing impervious or semipervious top stratum, or, if none exists, be placed directly on pervious deposits. A berm also affords some protection against sloughing of the landside levee slope. Berms are relatively simple to construct and require very little maintenance. They frequently improve and reclaim land as areas requiring underseepage treatment are often low and wet. Berms can also serve as a source of borrow for emergency repairs to the levee. Because they require additional fill material and space, they are used primarily with agricultural levees. Subsurface profiles must be carefully studied in selecting berm widths. For example, where a levee is founded on a thin top stratum and thicker clay deposits lie a short distance landward, as shown in Figure 5-l, the berm should extend far enough landward to lap the thick clay deposit, regardless of the computed required length. Otherwise, a concentration of seepage and high exit gradients may occur between the berm toe and the landward edge of the thick clay deposit.

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### b. Types of seepage berms. Four types of seepage berms have been used, with selection based on available fill materials, space available landside of the levee proper, and relative costs. (1) Impervious berms. A berm constructed of impervious soils restricts the pressure relief that would otherwise occur from seepage flow through the top stratum, and consequently increases uplift pressures

5-2EM 1110-2-1913 30 Apr 2000

5-3 

### beneaththe to p stratum. However, the berm can be constructed to the thickness necessary to provide an adequate factor of safety against uplift. (2) Semipervious berms. Semipervious material used in constructing this type of berm should have an in-place permeability equal to or greater t han that of the top stratum. In this type of berm, some seepage will pass through the berm and emerge on its surface. However, since the presence of this berm creates additional resistance to flow, subsurface pressures at the levee toe will be increased. (3) Sand berms. While a sand berm will offer less resistance to flow than a semipervious berm, it may also cause an increase in substratum pressures at the levee toe if it does not have the capacity to conduc t seepag e flow landward without excessive internal head losses. Material used in a sand berm should be a s pervious as possible, with a minimum permeability of 100 x 10 cm per sec. Sand berms require less material -4 

### and occupy less space than impervious or semipervious berms providing the same degree of protection. (4) Free-draining berms. A f ree-draining berm is one composed of random fill overlying horizontal sand and gravel drainage layers (with a terminal perforated collector pipe system), designed by the same methods usedfor d rainage layers in dams. Although the free-draining berm can afford protection agains t underseepa ge

pressures with less length and thickness than the other types of seepage berms, its cost i s generally much greater than the other types, and thus it is rarely specified.

c. Berm design . Design equations, criteria, and examples are presented in Appendix C for seepag e berms. d. Computer programs to use for seepage analysis. (1) If the soil can be idealized with a top blanket of uniform thickness and seepage flow is assumed to be horizontal in the foundation and vert ical in the blanket, then LEVSEEP (Brizendine, Taylor, and Gabr 1995) or LEVEEMSU (Wolff 1989; Gabr, Taylor, Brizendine, and Wolff 1995) could be used. (2) If the soil profile is characterized by a top blanket and two foundation layers of uniform thickness, and seepage flow is assumed to be horizon tal in the foundation, horizontal and vertical in the transition layer, andvertical in the blanket, then LEVEEMSU or the finite element method (CSEEP) could be use d (Biedenharn and Tracy 1987; Knowles 1992; Tracy 1994; Gabr, Brizendine, and Taylor 1995). LEVEESMU would be simpler to use. (3) If the idealized soil profile includes irregular geometry (slopes greater than 1 vertical to 100 horizontal), more than three layers and/or anisotropic permeability (k Ö k ), then only the finite element v h 

### method (CSEEP) is applicable. When using CSEEP it is recommended that FastSEEP, a graphical pre- and post-processor, be used f

or mesh generation, assigning boundary conditions and soil properties, and viewing the results (Engineering Computer Graphics Laboratory 1996). 5-5. Pervious Toe Trench a. General . Where a levee is situated on deposits of pervious material overlain by little or no impervious material, a partially penetrating toe trench, as shown in Figure 5-2, can improve seepage conditions at or near the levee toe. Where the pervious stratum is thick, a drainage trench of any practicable depth would attract onl ya small portion of the seepage flow and detrimental underseepage would bypass the trench

. Conseque ntly, the main use of a pervious toe trench is to control shallow underseepage and protect the area inth e vicinity of the levee toe. Pervious toe trenches may be used in conjunction with relief well systems ;EM 1110-2-1913 30 Apr 2000
the wells collect the deeper seepage and the trench collects the shallow seepage. Such a system is shown in Figure 5-3. The trench is frequently provided with a perforated pipe to collect the seepage. The use of a collector system is dependent on the volume of seepage and, to some degree, the general location of the levee. Collector systems are usually not required for agricultural levees but find wider use in connection with urban levees. b. Location. As seen in Figures 5-2 and 5-3, pervious drainage trenches are generally located at the levee toe, but are sometimes constructed beneath the downstream levee slope as shown in Figure 5-4. Here the trench is located at the landward quarter point of the levee, and discharge is provided through a horizontal pervious drainage layer. Unless it is deep enough, it may allow excessive seepage pressures to act at the toe. There is some advantage to a location under the levee if the trench serves also as an inspection trench and because the horizontal pervious drainage layer can help to control embankment seepage.

c. Geometry. Trench geometry will depend on the volume of expected underseepage, desired reduction in uplift pressure, construction practicalities, and the stability of the material in which it is being excavated. Trench widths varying from 0.61 to 1.83 m (2 to 6ft) have been used. Trench excavation can be expedited if a ditching machine can be used. However, narrow trench widths will require special compaction equipment. One such piece of equipment (Figure 5-5), which is a vibrating-plate type of compactor specially made to fit on the boom of a backhoe, has apparently performed satisfactorily.



### <t. WATERS tot 

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Figure 5-2. Typical partially penetrating pervious toe trench

d. Bac/ifi/1. The sand backfill for trenches must be designed as a filter material in accordance with criteria given in Appendix D. If a collector pipe is used, the pipe should be surrounded by about a 305-mm (1-ft) thickness of gravel having a gradation designed to provide a stable transition between the sand backfill and the perforations or slots in the pipe. A typical section of a pervious drainage trench with collector pipe is shown in Figure 5-6. Placement of trench backfill must be done in such a manner as to minimize segregation. Compaction ofthe backfill should be limited to prevent breakdown of material or over compaction resulting in lowered permeabilities.

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PERVIOUS STRATUM EM 1110-2-1913 30 Apr 2(100

LANDS lOt. R£l.I£F' W£/.LS

Figure 5-3. Typical pervious toe trench with collector pipe (Figure 5-6 shows trench details)

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Figure 5-4. Pervious toe trench located beneath landward slope



### 5·6. Pressure Relief Wells LANOSID£

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### a. General. Pressure relief wells may be installed along the landside toe of levees to reduce uplift pressure which may otherwise cause sand boils and piping of foundation materials. Wells accomplish this by intercepting and providing controlled outlets for seepage that would otherwise emerge uncontrolled landward of the levee. Pressure relief well systems are used where pervious strata underlying a levee are 5-5EM 1110-2-1913 30 Apr 2000

too deep or too thick to be penetrated by cutoffs or toe drains or where space for landside berms is limited. Relief wells should adequately penetrate pervious strata and be spaced sufficiently close to intercept enough seepage to reduce to safe values the hydrostatic pressures acting beyond and between the wells. The wells must offer little resistance to the discharge of water while at the same time prevent loss of any soil. They must also be capable of resisting corrosion and bacterial clogging. Relief well systems can be easily expanded if the initial installation does not provide the control needed. Also, the discharge of existing wells can be increased by pumping if the need arises. A relief well system requires a minimum of additional real estate as compared with the other seepage control measures such as berms. However, wells require periodic maintenance and frequently suffer loss in efficiency with time, probably due to clogging of well screens by muddy surface waters, bacteria growth, or carbonate incrustation. They increase seepage discharge, and means for collecting and disposing of their discharge must be provided. 

### b. Design of well systems. The design of a pressure relief well system involves determination of well spacing, size, and penetration to reduce uplift between wells to allowable values. Factors to be considered are (a) depth, stratification, and permeability of foundation soils, (b) distance to the effective source of seepage, (c) characteristics of the landside top stratum, if ;;. any, and (d) degree of pressure relief desired.

Figure 5-5. Special equipment for compacting sand in pervious toe trenches Guidance on the method used to determine well spacing, size, and penetration is contained in EM 1110-2-1914 and U.S. Army Engineer Waterways Experiment Station TM No. 3-424. Where no control measures are present, relief wells for agricultural and urban levees should be designed so that imax midway between the wells or landward from the well line should not exceed 0.50 (equivalent to FS 

### = 1.7 for an average soil saturated unit weight of 1840 kg/m 3 (115 pet)). Many combinations of well spacing and penetration will produce the desired pressure relief; hence, the final selected spacing and penetration must be based on cost comparisons of alternative combinations. After the general well spacing for a given reach oflevee has been determined, the actual location of each well should be established to ensure that the wells will be located at critical seepage points and will fit natural topographic features.

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Figure 5-6. Pervious toe trench with collector pipe EM 1110-2-1913 30 Apr 2000



### c. Design of individual wells. The design of the well involves the selection of type and length of riser pipe and screen, design of the gravel pack, and design of well appurtenances. A widely used well design that has given good service in the past is shown in Figure 5-7. (1) Riser pipe and screen. The well screen normally extends from just below the top of the pervious stratum to the bottom of the well, with solid riser pipe installed from the top of the pervious strata to the surface. In zones of very fine sand or silt, the screen is replaced by unperforated (blank) pipe. The type of material for the riser and screen should be selected only after a careful study of the corrosive properties of the water to be carried by the well. Many types of metals, alloys, fiberglass, plastics, and wood have been used in the past. At the present time, stainless steel and plastic are the most widely used, primarily because of their corrosionresistant properties. Plastic risers should be considered with caution, being susceptible to damages during mechanical treatment or chemical treatment which develop excessive heat or cold. (2) Filter. The filter that surrounds the screen must be designed in accordance with criteria given in Appendix D using the slot size of the screen and the gradation of surrounding pervious deposit as a basis of design. No matter what size screen is used, a minimum of 152.4 mm (6 in.) of filter material should surround the screen and the filter should extend a minimum of610.8 mm (2ft) above the top and 1.2 m (4 ft) below the bottom of the well screen. Above the filter to the bottom of the concrete or impervious backfill, sand backfill may be used. (3) Well appurtenances. In selecting well appurtenances, consideration must be given to ease of maintenance, protection against contamination from back flooding, damage by debris, and vandalism. To prevent wells from becoming backflooded with muddy surface water, which greatly impairs their efficiency when they are not flowing, an aluminum check valve, rubber gasket, and plastic standpipe, as shown in Figure 5-7, can be installed on each well. To safeguard against vandalism, accidental damage, and the entrance of debris, the tops of the wells should be provided with a metal screen or flap-type gate. The elevation of the top of any protective standpipes must be used in design as the well discharge elevation. 

### d. Well installation. Proper methods of drilling, backfilling, and developing a relief well must be employed or the well will be of little or no use. These procedures are described in detail in EM 1110-2-1914.

5-7EM 1110-2-1913 30 Apr 2000

PLASTIC STAND PIPE

Figure 5-7. Typical relief well

Section II Seepage Through Embankments 

### 5-7. General PIPE 

### THROUGH VERY FINE SAND OR SILT STRATA

Should through seepage in an embankment emerge on the landside slope (Figure 5-8a), it can soften finegrained fill in the vicinity of the landside toe, cause sloughing of the slope, or even lead to piping (internal erosion) of fine sand or silt materials. Seepage exiting on the landside slope would also result in high seepage forces, decreasing the stability of the slope. In many cases, high water stages do not act against the levee long enough for this to happen, but the possibility of a combination of high water and a period ofheavy precipitation may bring this about. Iflandside stability berms or berms to control underseepage are required because of foundation conditions, they may be all that is necessary to prevent seepage emergence on the
5-8RIVl:RSIDE EM 1110·2-1913 30 Apr 2000

LANDS IDE IYCT SLOP£

a. Homogeneous section on impervious foundation seepage emerging on landside slope
RIVtRSIDE T.ANDSIDE

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c. Pervious toe combined with partially penetrating toe trencn
Figure 5-8. Embankment with through seepage


### slope. On the other hand, if no berms are needed, lands ide slopes are steep, and floodstage durations and other pertinent considerations indicate a potential problem of seepage emergence on the slope, provisions should be incorporated in the levee section such as horizontal and/or inclined drainage layers or toe drains to prevent seepage from emerging on the landside slope. These require select pervious granular material and graded filter layers to ensure continued functioning, and therefore add an appreciable cost to the levee construction, unless suitable materials are available in the borrow areas with only minimal processing required. Where large quantities of pervious materials are available in the borrow areas, it may be more practicable to design a zoned embankment with a large landside pervious zone. This would provide an efficient means of through seepage control and good utilization of available materials. Additional information on seepage control in earth embankments including zoning embankments and vertical (or inclined) and horizontal drains is given in Chapter 8 of EM 1110-2-1901.
5-9EM 1110-2-1913

30 Apr 2000

5-10 

### 5-8. Pervious Toe Drain A pervious toe (Figure 5-8b) will provide a ready exit for seepage through the embankment and can lower the phreatic surface sufficiently so that noseepage will emerge on the landside slope. A pervious toe can also be combined with partially penetrating toe trenches, which have previously been discussed, as a method for controlling shallow underseepage. Such a configuration is shown in Figure 5-8c. 5-9. Horizontal Drainage Layers Horizontal drainage layers, as shown in Figure 5-9a, essentially serve the same purpose as a pervious toe but are advantageous in that they can extend further under the embankment requiring a relatively small amount of add itional material. They can also serve to protect the base of the embankment against high uplif t pressures where shallow foundation underseepage is occurring. Sometimes horizontal drainage layers serve also to carry off seepage from shallow foundation drainage trenches some distance under the embankment as shown previously in Figure 5-4. 5-10. Inclined Drainage Layers An inclined dra

inage layer as shown in Figure 5-9b is one of the more positive means of controlling internal seepageand is used extensively in earth dams. It is rarely used in levee construction because of the added cost, but might be justified for short levee reaches in important locations where landside slopes must be steep andother c ontrol measures are not considered adequate and the levee will have high water against it for prolonged periods. The effect of an inclined drainage layer is to completely intercept embankment seepage regardless o f the degree of stratification in the embankment or the material type riverward or landward o f th e drain. As a matter of fact, the use of this type of drain allows the landside portion of a levee to be built of any material of adequate strength regardless of permeability. When used between an impervious core and oute r pervious shell (Figure 5-9c), it also serves as a filter to prevent migration of impervious fines into the oute rshell. If the difference in gradation between the impervious and pervious material is great, the drai n may have t o be designed as a graded filter (Appendix D). Inclined drains must be tied into horizontal drainage layers to provide an exit for the collected seepage as shown in Figures 5-9b and 5-9c. 5-11. Design of Drainage Layers Thedesign of pervious toe drains and horizontal and inclined drainage layers must ensure that such drains have adequate thickness a

nd permeability to transmit seepage without any appreciable head loss while at the same time preventing migration of finer soil particles. The design of drainage layers must satisfy the criteria outlinedin Ap pendix D for filter design. Horizontal drainage layers should have a minimum thickness o f 457.2 mm (18 in.) for construction purposes. 5-12. Compaction of Drainage Layers Placement

and compaction of drainage layers must ensure that adequate density is attained, but should not allow segregation and contamination to occur. Vibratory rollers are probably the best type of equipment for compactionof cohesionless material although crawler tractors and rubber-tired rollers have also been used successfully. Saturation or flooding of the materi al as the roller passes over it will aid in the compaction process and in some cases has been the only way specified densities could be attained. Care must always be taken to not overcompact to prevent breakdown of materials or lowering of expected permeabilities. Load

ing, dumping, and spreading operations should be observed to ensure that segregation does not occur

. Gradation tests should be run both before and after compaction to ensur e that the material meets specifications and does not contain too many fines.EM 1110-2-1913 30 Apr 2000

-R-IV_E_R_S_I_O_E

__

# __;~-·~,'?,.~---L-A-N_D_S_I_D_E

a. Horizontal drainage layer

RIVERSIDE:

LANDS\ DE

b. Inclined drainage layer-homogeneous embankment

RIVERSIDE:

LANDS IDE

c. Inclined drainage layer-zoned embankment
Figure 5-9. Use of horizontal and inclined drainage layers to control seepage through an embankment

5-11EM 1110-2-1913 30 Apr 2000

6-1 

### Chapter 6 Slope Design and Settlement

Section I Embankment Stability 6-1. Embankment Geometry

a. S lopes . For levees of significant height or when there is concern about the adequacy of availabl e embankment materials or foundation conditions, embankment design requires detailed analysis. Low levees andl evees to be built of good material resting on proven foundations may not require extensive stability analysis. For these cases, practical considerations such as type and ease of construction, maintenance , seepage and slope protection criteria control the selection of levee slopes. ( 1) Type of construction. Fully compacted levees generally enable the use of steeper slopes than those of levees constructed by semicompacted or hydraulic means. In fact, space limitations in urban areas often dictate minimum levee sections requiring select material and proper compaction to obtain a stable section. (2) Ease of construction. A 1V on 2H slope is generally accepted as the steepest slope that can easily be constructed and ensure stability of any riprap layers. (3 ) Maintenance. A 1V on 3H slope is the steepest slope that can be conveniently traversed wit h conventional mowing equipment and walked on during inspections. (4) Seepage. For sand levees, a 1V on 5H landside slope is considered flat enough to prevent damage from seepage exiting on the landside slope. ( 5) Slope protection. Riverside slopes flatter than those required for stability may have to be specified to provide protection from damage by wave action. b. Final Le vee Grade . In the past, freeboard was used to account for hydraulic, geotechnical , construction, operation and maintenance uncertainties. The term and concept of freeboard to account for these unce rtainties is no longer used in the design of levee projects. The risk-based analysis directly accounts for hydraulic uncertainties and establishes a nominal top of protection. Deterministic analysis using physical pr operties of the foundation and embankment materials should be used to set the final levee grade to account for settlement, shrinkage, cracking, geologic subsidence, and construction tolerances.

c . Cro wn width . The width of the levee crown depends primarily on roadway requirements and future emergency needs. To provide access for normal maintenance operations and floodfighting operations , minimu m widths of 3.05 to 3.66 m (10 to 12 ft) are commonly used with wider turnaround areas provided at speci fied intervals; these widths are about the minimum feasible for construction using modern heav y earthmoving equipment and should always be used for safety concerns. Where the levee crown is to be used as a higher class road, its width is usually established by the responsible agency. 6-2. Standard Levee Sections and Minimum Levee Section

a . Many districts have established standard levee-sections for particular levee systems, which hav e proven satisf actory over the years for the general stream regime, foundation conditions prevailing in those areas, and for soils available for levee construction. For a given levee system, several different standardEM 1110-2-1913

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6-2 

### sections may be established depending on the type of construction to be used (compacted, semicompacted, unc ompacted, or hydraulic fill). The use of standard sections is generally limited to levees of moderate height(say less than 7.62 m (25 ft)) in reaches where there are no serious underseepage problems, wea k foundationsoils, or undesirable borrow materials (very wet or very organic). In many cases the standard leveesection has more than the minimum allowable factor of safety relative to slope stability, its slope s being established primarily on the bas is of construction and maintenance considerations. Where high levees or levees on foundations presenting special underseepage or stability problems are to be built, the uppermost riverside and landside slopes of the levee are often the same as those of the standard section, with the lower slopes flattened or stability berms provided as needed. b

. The adoption of standard levee sections does not imply that stability and underseepage analyses are not made. However, when borings for a new levee clearly demonstrate foundation and borrow conditions similar to those a

t existing levees, such analyses may be very simple and made only to the extent necessary to demonstrate unquestioned levee stability. In addition to being used in levee design, the standard leve e sections are applicable to initial cost estimate, emergency and maintenance repairs.

c . The minimum levee section shall have a crown width of at least 3.05 m (10 ft) and a side slope flatter than or equal to 1V on 2H, regardless of the levee height or the possibly less requirements indicated in the res ults of stability and seepage analyses. The required dimensions of the minimum levee section is to provide an access road for flood-fighting, maintenance, inspection and for general safety conditions. 6-3. Effects of Fill Characteristics and Compaction

a. Compacted fills . The types of compaction, water content control, and fill materials govern th e steepness of levee slopes from the stability aspect if foundations have adequate strength. Where foundations are weak and compressible, high quality fill con struction is not justified, since these foundations can support only levees with flat slopes. In such cases uncompacted or semicompacted fill, as defined in paragraph 1-5, is app ropriate. Semicompacted fill is also used where fine-grained borrow soils are considerably wet o f optimum or in construction of very low levees where other considerations dictate flatter levee slopes than neededfo r stability. Uncompacted fill is generally used where the only available borrow is very wet an d frequentlyhas high organic content and where rainfall is very high during the construction season. When foundations have adequate strength and where space is limited in urban areas both with respect to quantity of borrow and levee geometry, compacted levee fill construction by earth dam procedures is frequently selected. This involves the use of select material, water content control, and compaction procedures a s described in paragraph 1-5. b . Hydraulic Fill

. Hydraulic fill consists mostly of pervious sands built with one or two end-discharge or bottom-discharging pipes. Tracked or rubber-tired dozers or front-end loaders are used to move the sand to shape the embankment slopes. Because a levee constructed of hydraulic fill would be very pervious and have a low dens ity, it would require a large levee footprint and would be susceptible to soil liquefaction

. Hydraulic fill would als o quickly erode upon overtopping or where an impervious covering was penetrated. For these reasons, hydraulic fill may be used for stability berms, pit fills and seepage berms but shall not normal lybe used in constructing levee embankments. However, hydraulic fill may be used for levee s protecting agricultural a

reas whose failure would not endanger human life and for zoned embankments that include impervious seepage barriers.EM 1110-2-1913 30 Apr 2000

6-3 

### Section II Stability Analyses 6-4. Methods of Analysis The principal methods used to analyze levee embankments for stability against shear failure assume either (a) a sliding surface having the shape of a circular arc within the foundation and/or the embankment or (b) a composite failure surface composed of a long horizontal plane in a relatively weak foundation or thi n foundation st

ratum connecting with diagonal plane surfaces up through the foundation and embankment to the ground surface. Various methods of analysis are described in EM 1110-2-1902, and can be chosen for use where determined appropriate by the designer. Computer programs are available for these analyses, with the vario us loading cases described in EM 1110-2-1902, so the effort of making such analyses is greatl y reduced, and primary attention can be devoted to the more important problems of defining the shear strengths, unit weights, geometry, and limits of possible sliding surfaces. 6-5. Conditions Requiring Analysis Thevarious loading conditions to which a levee and its foundation may be subjected and which should be considered

in analyses are designated as follows: Case I, end of construction; Case II, sudden drawdown from full flood stage; Case III, steady seepage from full flood stage, fully developed phreatic surface ; Case IV, earthquake. Each case is discussed briefly in the following paragraphs and the applicable type of designshear strength is given. For more detailed information on applicable shear strengths, methods o f analysis, and assumptions made for each case refer to EM 1110-2-1902.

a . Case I - End of construction . Thiscase represents undrained conditions for impervious embankment and foundation soils; i.e., excess pore water pressure is present because the soil has not had time to drain since being loaded. Results from laboratory Q (unconsolidated-undrained) tests are applicable to fine-grained soils loaded under this condition while results of S (c onsolidated-drained) tests can be used for pervious soils thatdrain fastenough during loading so that no excess pore water pressure is present at the en d of construction. The end of construction condition is applicable to both the riverside and landside slopes. b. Case II - Sudden drawdown . This case represents the condition whereby a prolonged flood stag e saturates at

least the major part of the upstream embankment portion and then falls faster than the soil can drain. This causes the development of excess pore water pressure which may result in the upstream slope becoming unstable. For the selection of the shear strengths see Table 6-1a.

c. Case III - Steady seepage from full flood stage (fully developed phreatic surface) . This condition occurs when the water remains at or near full flood stage long enough so that the embankment becomes fully saturated and a condition of steady seepage occurs. This condition may be critical for landside slop e stability. Design shear strengths should be based on Table 6-1a. d. Case IV - Earthquake . Earthquake loadings are not normally considered in analyzing the stability of leveesbecause of the low probability of earthquake coinciding with periods of high water. Levees con

structe d of loose cohesionless materials or founded on loose cohesionless materials are particularl y susceptibl e

to failure due to liquefaction during earthquakes. Depending on the severity of the expecte d ear thquakeand the importance of the levee, seismic analyses to determine liquefaction susceptibility may be required.EM 1110-2-1913

30 Apr 2000

6-4 Table 6-1a Summary of Design Conditions Analysis Condition Shear Strength Pore Water Pressure a During and End-of- Free draining soils - use effective Free draining soils - Pore water pressures can be estimated using Construction stresses analytical techniques such as hydrostatic pressure computations for no flow or steady seepage analysis techniques (flow nets, finite element analyses or finite difference analyses). Low permeability soils - use Low permeability soils - Total stresses are used; pore water undrained strengths and total pressures are set to zero in the slope stability computations. stresses b Steady State Use effective stresses. Residual Estimated from field measurements of pore water pressures, Seepage Conditions strengths should be used where hydrostatic pressure computations for no flow conditions, or steady previous shear deformation or seepage analysis techniques (flow nets, finite element analyses or sliding has occurred. finite difference analyses). Sudden Drawdown Free draining soils - use effective Free draining soils - First stage computations (before drawdown) - Conditions stresses steady-state seepage pore pressures as described for steady state seepage condition. Second and third stage computations (after drawdown) - pore water pressures estimated using same techniques as for steady seepage, except with lowered water levels. Low permeability soils - Three stage Low permeability soils - First stage computations - steady-state computations: First stage use seepage pore pressures as described for steady state seepage effective stresses; second stage condition. use undrained shear strengths and Second stage computations - Total stresses are used pore water total stresses; third stage use pressures are set to zero. drained strengths (effective Third stage computations - Use same pore pressures as free stresses) or undrained strengths draining soils if drained strengths are being used; where undrained (total stresses) depending on which strengths are used pore water pressures are set to zero. strength is lower - this will vary along the assumed shear surface. Effective stress parameters can be obtained from consolidated-drained (CD, S) tests (either direct shear or triaxial) or consolidated
a undr ained (CU, R) triaxial tests on saturated specimens with pore water pressure measurements. Direct shear or Bromhead ring shear tests should be used to measur e residual strengths. Undrained strengths can be obtained from unconsolidated-undrained (UU, Q) tests. Undrained shea r strengths can also be estimated using consolidated-undrained (CU, R) tests on specimens consolidated to appropriate stress cond itions representative of field conditions; however, the “R” or “total stress” envelope and associated c and ö , from CU, R tests should not be used. For saturated soils use ö = 0; total stress envelope with ö > 0 is only applicable to partially saturated soils. b


### 6-6. Minimum Acceptable Factors of Safety The minimum re quired safety factors for the preceding design conditions along with the portion of th e embankment for which analyses are required and applicable shear test data are shown in Table 6-1b. 6-7. Measures to Increase Stability Means for improving weak and compressible foundations to enable stable embankments to be constructed thereon are discussed in Chapter 7. Methods of improving embankment stability by changes in embankment section are presented in the following paragraphs.

a. Flatten embankment slopes . Flattening embankment slopes will usually increase the stability of an embankmentagainst a shallow foundation type failure that takes place entirely within the embankment

. Fla tteningembankment slopes reduces gravity forces tending to cause failure, and increases the length o f potential failure surfaces (and therefore increases resistance to sliding).EM 1110-2-1913 30 Apr 2000

6-5 Table 6-1b Minimum Factors of Safety - Levee Slope Stability Applicable Stability Conditions and Required Factors of Safety End-of- Long-Term Type of Slope Construction (Steady Seepage) Rapid Drawdown Earthquake a b New Levees 1.3 1.4 1.0 to 1.2 (see below) Existing Levees -- 1.4 1.0 to 1.2 (see below) c Other Embankments and dikes 1.3 1.4 1.0 to 1.2 (see below) d e,f c,f f Sudden drawdown analyses. F. S. = 1.0 applies to pool levels prior to drawdown for conditions where these water levels are a unlikely to persist for long periods preceding drawdown. F. S. = 1.2 applies to pool level, likely to persist for long periods prior to drawdown. See ER 1110-2-1806 for guidance. An EM for seismic stability analysis is under preparation. b For existing slopes where either sliding or large deformation have occurred previously and back analyses have been performed to c establish design shear strengths lower factors of safety may be used. In such cases probabilistic analyses may be useful in supporting the use of lower factors of safety for design. Includes slopes which are part of cofferdams, retention dikes, stockpiles, navigation channels, breakwater, river banks, and d excavation slopes. Temporary excavated slopes are sometimes designed for only short-term stability with the knowledge that long-term stability is e not adequate. In such cases higher factors of safety may be required for end-of-construction to ensure stability during the time the excavation is to remain open. Special care is required in design of temporary slopes, which do not have adequate stability for the long-term (steady seepage) condition. Lower factors of safety may be appropriate when the consequences of failure in terms of safety, environmental damage and f economic losses are small.


### b. Stability berms . Berms essent ially provide the same effect as flattening embankment slopes but are generally mor

e effective because of concentrating additional weight where it is needed most and by forcing a substantial increase in the failure path. Thus, be rms can be an effective means of stabilization not only for shallow foundation and embankment type failures but for more deep-seated foundation failures as well

. Berm thickness and width should be determined from stability analyses and the length should be great enoughto enc ompass the entire problem area, the extent of which is determined from the soil profile

. Foundation failur

es are normally preceded by lateral displacement of material beneath the embankment toe and by noticeable heave of material just beyond the toe. When such a condition is noticed, berms are often used as an emergency measure to stabilize the embankment and prevent further movement. 6-8. Surface Slides Experi ence

indicates that shallow slides may occur in levee slopes after heavy rainfall. Failure generall y occurs in very plastic clay slopes. They are probably the result of sh rinkage during dry weather and moisture gainduring wet weather with a resulting loss in shear strength due to a net increase in water content, plus addit ional driving force from water in cracks. These failures require maintenance and could be eliminated or reduced in frequency by using les s plastic soils near the surface of the slopes or by chemical stabilization of the surface soils.EM 1110-2-1913

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6-6 

### Section III Settlement 6-9. General Evaluatio n

of the amount of postconstruction settlement that can occur from consolidation of bot h embankment and foundation may be important if the settlement would result in loss of freeboard of the levee or damage to structures in the embankment. Many distr icts overbuild a levee by a given percent of its height totake into account anticipated settlement both of the foundation and within the levee fill itself. Common allo wances are 0 to 5 percent for compacted fill, 5 to 10 percent for semicompacted fill, 15 percent fo r un compacted

fill, and 5 to 10 percent for hydraulic fill. Overbuilding does however increase the severity of stability problems and may be impracticable or undesirable for some foundations. 6-10. Settlement Analyses Settlemen testimates can be made by theoretical analysis as set forth in EM 1110-1-1904. Detaile d settleme nt analyses should be made when significant consolidation is expected, as under high embankment loads, embankments of highly compressible soil, embankments on compressible foundations, and beneath steel and concrete structures in levee systems founded on compressible soils. Where foundation an d embankment soils are pe

rvious or semipervious, most of the settlement will occur during construction. For impervious soils it is usually conservatively assumed that all the calculated settlement of a levee built by a normal sequence of construction operations will occur after construction. Where analyses indicate that more foundation settlement would occur than can be tolerated, partial or complete removal of compressibl e fou ndationmaterial may be necessary from both stability and settlement viewpoints. When the depth o f excava tionrequired to accomplish this is too great for economical construction, other methods of contro l such as stag e construction or vertical sand drains may have to be employed, although they seldom are justified for this purpose.EM 1110-2-1913 30 Apr 2000

7-1 

### Chapter 7 Levee Construction
Section I Levee Construction Methods 7-1. Classification of Methods

a . Levee e mbankments classified according to construction methods used are listed in Table 7-1 for levees co mposed of impervious and semipervious materials (i.e., those materials whose compactio n c haracteristics are such as to produce a well-defined maximum density at a specific optimum water content). While the central portion of the embankment may be Category I (compacted ) or II (semicompacted), riverside andlan dside berms (for seepage or stability purposes) may be constructed by Category II or II I (uncompacted) methods. b . Pervious levee fill consisting of sands or sands and gravels may be placed either in the dry with normal earthmovi ngequipment or by hydraulic fill methods. Except in seismically active areas or other area s r equiring a high degree of compaction, compaction by vibratory means other than that afforded by tracked b ulldozers is not generally necessary . Where underwater placement is required, it can best be accomplished withperviou s fill using end-dumping, dragline, or hydraulic means, although fine-grained fill can be s o placed if due consideration is given to the low density and strength obtained using such materials. Section II Foundations 7-2. Foundation Preparation and Treatment

a. General . Minimum foundation preparation for levees consists of clearing and grubbing, and mos t levees will also require some degree of stripping. Clearing, grubbing, stripping, the disposal of product s therefrom, and final preparation are discussed in the following paragraphs. b. Clearing . Clearing consists of c omplete removal of all objectional and/or obstructional matter above the ground surface. This includes all trees, fallen timber, brush, vegetation, loose stone, abandone d st ructures, fencing, and similar debris. The entire foundation area under the levee and berms should b e cleared well ahead of any following construction operations. c. Gru bbing . Grubbing consists of the removal, within the levee foundation area, of all stumps, roots, b uried logs, old piling, old paving, drains, and other objectional matter. Grubbing is usually not necessary beneath stability berms. Roots or other intrusions over 38.1 mm (1-1/2 in.) in diameter within the leve e foundationarea should be removed to a depth of 0.91 m (3 ft) below natural ground surface. Shallow tile d

rains somet imes found in agricultural areas should be removed from the levee foundation area. The sides o f all holes and depression s caused by grubbing operations should be flattened before backfilling. Backfill, c onsisting or material similar to adjoining soils, should be placed in layers up to the final foundation grade a nd compacted to a density equal to the adjoining undisturbed material. This will avoid “soft spots” under the levee and maintain the continuity of the natural blanket. d. Stripping . After founda tion clearing and grubbing operations are complete, stripping is commenced. The purpose of stripping is to remove low growing vegetation and organic topsoil. The depth of strippingEM 1110-2-1913

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7-2Table 7-1Classification According to Construction Method of Levees Composed of Impervious and Semipervious MaterialsCategoryConstruction MethodUseI. CompactedSpecification of:Provides embankment section occupying minimum space. Providesstrong embankments of low compressibility needed adjacent toa. Water content range with respect to standardconcrete structures or forming parts of highway systems.effort optimum water contentb. Loose lift thickness (152.4 mm to 228.6 mm(6-9 in.))c. Compaction equipment (sheepsfoot or rubber-Requires strong foundation of low compressibility and availability oftired rollers)borrow materials with natural water contents reasonably close tospecified ranges.d. Number of passes to attain a given percentcompaction based on standard maximum densitye. Minimum required densityUsed where field inspection is not constant throughout the project.II. SemicompactedCompaction of fill materials at their natural waterThe most common type of levee construction used in reachescontent (i.e., no water content control). Borrowwhere:materials known to be too wet would require somedrying before placement. Placed in thicker lifts thana. There are no severe space limitations and steep-slopedCategory I (about 304.8 mm (12 in.)) and compactedCategory I embankments are not required.either by controlled movement of hauling and spreadingequip ment or by fewer passes of sheepsfoot or rubber-b.Relatively weak foundations could not support steep-slopedtired rollers. Compaction evaluated relative to 15-blowCategory I embankments.compaction test.c. Underseepage conditions are such as to required widerembankment base than is provided by Category I construction.d.Water content of borrow materials or amount of rainfall duringconstruction season is such as not to justify Category Icompaction.III. Uncompacteda. Fill cast or dumped in place in thick layers withLevees infrequently constructed today using methodaexcept forlittle or no spreading or compaction.temporary emergency. Both methods are used for constructionof stability berms, pit fills and seepage berms.b. Hydraulic fill by dredge, often from channelexcavation.EM 1110-2-1913 30 Apr 2000

7-3 

### is determin ed by local conditions and normally varies from 152.4 to 304.8 mm (6 to 12 in.) Stripping i s usually li mited to the foundation of the levee embankment proper, not being required under berms. Al l stripped material suitable for use as topsoil should be stockpiled for later use on the slopes of th e embankment and berms. Unsuitable material must be disposed of by methods described in the next paragraph. e. Disposal of debris . Debris from clearing, grubbing, and stripping operations can be disposed of by burning in areas where this is permitted. When burning is prohibited by local regulations, it needs to b e disposed of in an environmentally approved manner. f. E xploration trench . An exploration trench (often termed “inspection trench”) should be excavate d u nder all levees unless special conditions asdiscussed later warrant its omission. The purpose of this trench is to expose or intercept any undesirable underground features such as old drain tile, water or sewer lines, a nimal burrows, buried logs, pockets of unsuitable material, or other debris. The trench should be located at or near the centerline of hauled fill levees or at or near the riverside toe of sand levees so as to connec t with waterside impervious facings. Dimensions of the trench will vary with soil conditions and embankment configurations. Backfill should be placed only after a careful inspection of the excavated trench to ensure that seepage channels or undesirable materia l are not present; if they are, they should be dug out with a base o f sufficient width to allow backf ill compaction with regular compaction equipment. To backfill narrower trenches properly, special comp action procedures and/or equipment will be required. Trenches should have aminimum depth of 1.83 m (6 ft) except for embankment heights less than 1.83 m (6 ft), in which case the m inim um depth should equal the embankment height. Exploration trenches can be omitted where landside t oe drains beneath the levee proper constructed to comparable depths are employed (toe drains are discussed in more detail later in this chapter). g. Dewatering . Dewatering levee foundations for the purpose of excavation and back filling in the dry is e xpensive if more than simple ditches and sumps are required, and is usually avoided if at all possible

. Thecost factor may be an overriding consideration in choosing seepage control measures other than a compact ed

cutoff trench, such as berms, blankets, or relief wells. Where a compacted cutoff trenc h i nvolving excavation below the water table m ust be provided, dewatering is essential. TM 5-818-5 provides guidance in dewatering system design. h. Final foundation preparation . Soft or organic spots in the levee foundation should be removed and r eplaced with compacted material. Except in special cases where foundation surfaces are adversely affected b y remolding (soft foundations for instance), the foundation surface upon or against which fill is to be placed s hould be thoroughly broken up to a depth of at least 152.4 mm (6 in.) prior to the placement of the first lift o f fill. This helps to ensure g ood bond between the foundation and fill and to eliminate a plane of weakness at the interface. The foundation surface should be kept drained and not scarified until just prior to fil l placement in order to avoid saturation from rainfall. 7-3. Methods of Improving Stability

a. General . Levees located on foundation soils that cannot support the levee embankment because of i nadequate shear strength require some type of foundation treatment if the levee is to be built. Foundation deposits that are prone to cause problem s are broadly classified as follows: (1) very soft clays, (2) sensitive cla ys, (3) loose sands, (4) natural organic deposits, and (5) debris deposited by man. Very soft clays are susce ptibleto shear failure, failure by spreading, and excessive settlement. Sometimes soft clay deposit s h ave a zone of stronger clay at the surface, caused by dessication, which if strong enough may eliminate the need for expensive treatment. Sensitive clays are brittle and even though possessing considerable strength in the undisturbed state, are subject to partial or complete loss of strength upon disturbance. Fortunately,EM 1110-2-1913

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7-4 

### extremelysensitive clays are rare. Loose sands are also sensitive to disturbance and can liquefy and flow when subjected to shock or even shear strains caused by erosion at the toe of slopes. Most organic soils are very c ompressible and exhibit low shear strength. The physical characteristics and behavior of organi c deposits such as peat can sometimes be predicted with some degree of accuracy. Highly fibrous organic soils with water contents of 500 percent or more generally consolidate and gain strength rapidly. The behavior of debris deposited by man, such as industrial and urban refuse, is so varied in character that its physical b ehavior is difficult, if not impossible, to predict. The following paragraphs discuss methods of dealing with foundations that are inadequate for construction of proposed levees. b. Exc avation and replacement . The most positive method of dealing with excessively compressibl e a nd/or weak foundation soils is to remove them and backfill the excavation with suitable compacted material. T his procedure isfeasible only where deposits of unsuitable material are not excessively deep. Excavation and replacement should be used wherever economically feasible. c. Displacement by end dumping. (l) Frequently low levees must be constructed acrosssloughs and stream channels whose bottoms consist o f very soft fine-grained soils (often having high orga nic content). Although the depths of such deposits may not be large, the cost of removing t hem may not be justified, as a levee of adequate stability can be obtained b y end-dumping fill from one side of the slough or channel, pushing the fill over onto the soft materials, and c ontinually building up the fill until its weight displaces the foundation soils to the sides and front. By continuing this operation, the levee can finally be brought to grade . The fill should be advanced with a V-shaped l eading edge so that the center of the fill is most advanced, thereby displacing the soft material to both sides. A wave of displaced

foundation material will develop (usually visible) along the sides of the fill and should not be removed. A disadvantage of this method is that all soft material may not be displaced which could r esult in slides as the embankmen t is brought up and/or differential settlement after construction. Since this typeof construction produces essentially uncompacted fill, the design of the levee section should take this into account. (2) When this method of foundation treatment isbeing considered for a long reach of levee over unstable areas such as swamps, the possibility of facilitating displacement by blasting methods should be evaluated. Blas ters’ Handbook (1966) (Appendix A-2) presents general information on methods of blasting used to displace soft materials. (3) The end-dumping method is also used to provide a working platform on soft foundation soils upon which construction equipment can operate to construct a low levee. In this case, only enough fill material i s hauled in and dozed onto the foundation to build a working platform or pad upon which the levee proper c an be built by conventional equipment and methods. Material forming the working platform should not be st ockpiled on the platform or a shear failure may result. Only small dozers should be used to spread an d work the material. Where the foundation is extremely weak, it may be necessary to use a small clamshell to spread the material by casting it over the area. d. Stage construction. (1) General. Stage construction refers to the building of an embankment in stages or intervals of time. T his method is used where the strength of the foundation material is inadequate to support the entire weight o f the embankment, if built c ontinuously at a pace faster than the foundation material can drain. Using this m ethod, the embankment is built to intermediate grades and allowed to rest for a time before-placing more f ill. Such re st periods permit dissipation of pore water pressures which results in a gain in strength so that hi gher embankment loadings may be supported. Obviously this method is appropriate when pore waterEM 1110-2-1913 30 Apr 2000

7-5 

### pre ssuredissipation is reasonably rapid because of foundation stratification resulting in shorter drainag e paths. This pr ocedure works well for clay deposits interspersed with highly pervious silt or sand seams

. However, such seams must have exits for the escaping water otherwise they themselves will become seats of high po re water pressure and low strengths (pressure relief wells can be installed on the landside to i ncrease the ef

ficiency of pervious layers in foundation clays). Initial estimates of the time required for the needed strength gain can be made from results of consolidation tests and study of boring data. Piezometers s hould be installed during construction t o monitor the rate of pore water dissipation, and the resumption and rat e of fill placement should be based on these observations, together with direct observations of fill an d f oundation behavior. Disadvantages of this met hod are the delays in construction operation, and uncertainty as to its scheduling and efficiency. (2)Prefabricated vertical (wick) drains. If the expected rate of consolidation under stage construction i s unacceptably slow, it may be increased by the use of prefabricated vertical (wick) drains. Such drains are g eotextile wrapped plastic cores that provide open flowa ge areas in the compressible stratum. Their purpose i s to reduce the length of drainage paths, thus speeding up primary consolidation. The wick drains are very thin and about 101.6 mm (4 in.) wide. They can be pushed into place through soft soils over 30.5 m (100 ft) deep. Bef ore the drains are installed, a sand drainage blanket is placed on the foundation which serves not o nly to tie the drains together and provide an exit for es caping pore water, but as a working platform as well. This drainage blanket should not continue across the entire base width of the embankment, but should b e interrupted beneath the center.

e. Densifi cation of loose sands . The possibility of liquefaction of loose sand deposits in leve e foundations may have to be considered. Since methods for densifying sands, such as vibroflotation, are costly, they are generally not considered except in locations of important structures in a levee system

. T herefor e, defensive design features in the levee section should be provided, such as wider levee crest, and flatter slopes. Section III Embankments 7-4. Embankment Construction Control

a . Construction con

trol of levees may present somewhat different problems from that of dams because: (1) Construction operations may be carried on concurrently along many miles of levee, whereas th e majority of dams are less than about 0.8 km (0.5 mile) in lengt h and only in a few cases are dams longer than 4.8 km (3 miles). This means that more time is needed to cover the operations on many levee jobs. (2) Whi le inspection staff and testing facilities are located at the damsite, levee inspection personne l generally operate out of an area office which may be a considerable distance from the levee project. (3) There are frequently fiscal restraints which prevent assigning an optimum number of inspectors on levee work or even one full-time inspector on small projects. Under these conditions, the inspectors use d m ust be well-trained to observe construction operations, m inimizing the number of field density tests in favor o f devoting more time to visua l observations, simple measurements, and expedient techniques of classifying s oils, evalu ating the suitability of their water content, observing behavior of construction equipment on the fill, and indirectly assessing compacted field densities. b

. Althoughit has previously been stated that only limited foundation exploration and embankment design studies are generally need ed in areas where levee heights are low and foundation conditions adequateEM 1110-2-1913

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7-6 

### ( i.e., no question of levee stability), the need for careful construction control by competent inspection exists a s well as at those reaches where comprehensive investigations and analyses have been made. Some of the things that can happen during construction that can cause failure or distress of even low embankments on good foundations are given in Table 7-2.

Table 7-2 Embankment Construction Deficiencies Deficiency Possible Consequences Organic material not stripped from foundation Differential settlements; shear failure; internal erosion caused by through seepage Highly organic or excessively wet or dry fill Excessive settlements; inadequate strength Placement of pervious layers extending completely through Allows unimpeded through seepage which may lead the embankment to internal erosion and failure Inadequate compaction of embankment (lifts too thick, Excessive settlements; inadequate strength; through haphazard coverage by compacting equipment, etc.) seepage Inadequate compaction of backfill around structures in embankment Excessive settlements; inadequate strength; provides seepage path between structure and material which may lead to internal erosion and failure by piping


### 7-5. Embankment Zoning As a g eneral rule levee embankments are constructed as homogeneous sections because zoning is usually neither necessary nor practicable. However, where materials of varying permeabilities are encountered in b orrow areas, the more impervious materials should be placed toward the riverside of the embankment and the more pervious material t oward the landside slope. Where required to improve underseepage conditions, l andside berms should be constructed of the most pervious mater ial available and riverside berms of the more impervious materials. Where impervious materials are scarce, and the major portion of the embankment m ust be built of pe

rvious material, a central impervious core can be specified or, as is more often done, the riversideslope of the embankment can be covered with a thick layer of impervious material. The latter is generally more economical than a central impervious core and, in most cases, is entirely adequate. 7-6. Protection of Riverside Slopes

a . The protection needed on a riverside slope to withstand the erosional forces of waves and stream currents will vary, depending on a number of factors: ( 1) The length of time that floodwaters are expected to act against a levee. If this period is brief, with w ater levels against

the levee continually changing, grass protection may be adequate, but better protection may be required if currents or waves act against the levee over a longer period. (2) The rela tive susceptibility of the embankment materials to erosion. Fine-grained soils of lo w plasticity (or silts) are most erodible, while fat clays are the least erodible. ( 3) The riverside slope may be shielded from severe wave attack and currents by timber stands and wide space between the riverbank and the levee.EM 1110-2-1913 30 Apr 2000

7-7 

### ( 4) Structures riverside of the levee . Bridge abutments and piers, gate structures, ramps, and drainage outlets may constrict flow and cause turbulence with resultant scour. ( 5) Turbulence and susceptibilit y to scour may result if levee alignment includes short-radius bends or if smooth transitions are not provided where levees meet high ground or structures. ( 6) Requirem

ents for slope protection are reduced when riverside levee slopes are very flat as may be the case for levees on soft foundations. Several types of slope protection have been used including gras s cover, gravel, sand-asphalt paving, concrete paving, articulated concrete mat, and riprap, the choic e depending upon the degree of protection needed and relat ive costs of the types providing adequate protection. b

. Performance data on existing slopes under expected conditions as discussed above are invaluabl e in providing guidance for the selection of the type of slope protection to be used.

c . Sometimes it may be concluded that low cost protection, such as grass cover, will be adequate i n generalfor a levee reach, but with a realization that there may be limited areas where the need for greater protection may develop under infrequent circumstances. If the chances of serious damage to the levee i n s uch areas are remote, good engineering practice would be to provide such increased protection only if and when actual problems develop. Of course, it must be possible to accomplish this expeditiously so that the s ituation will not get out of hand. In any event, high-class slope protection, such as riprap, articulated mat, or paving should be provided on riverside slopes at the following locations: ( 1) Beneath bridges, since adequate turf cannot be generally established because of inadequate sunlight. (2) Adjacent to structures passing through levee embankments. d

. Riprap is more commonly used than other types of revetments when greater protection than that afforded by grass cover is required because of the relative ease of handling, stockpiling, placement, an d maintenanc e. Guidance on the design of riprap revetment to protect slopes against currents is presented in EM 1110-2-1601. Where slopes are composed of erodible granular soils or fine-grained soils of lo w p lasticity, a bedding layer of sand and gravel or spalls, or plastic filter cloth should be provided beneath the riprap.

e . W hen suitable rock is not available within economical haul distances, soil cement may provide the most economical slope protection (see Appendix G).EM 1110-2-1913 30 Apr 2000

8-1 

### Chapter 8 Special Features

Section I Pipelines and Other Utility Lines Crossing Levees 8-1. General Considerations

a . Serious damage to levees can be caused by inadequately designed or constructed pipelines, utilit y c onduits, or culverts (all hereafter referred to as “pipes”) beneath or within levees. Each pipe crossing should be evaluated for its potential damage which would negatively impact the integrity of the flood protectio n system and could ultimately lead to catastrophic failure. During high water, seepage tends to concentrate a long the outer surface of pi pes resulting in piping of fill or foundation material. High water also results in u plift pr essures that may cause buoyancy of some structures. Seepage may also occur because of leakage f rom the pipe. In the case of pipes crossing over levees, le akage can cause erosion in the slopes. In addition, l oss of fill or foundation material into the pipe can occur if joints are open. The methods of pipe installation shouldb e understood by the designer to anticipate problems that may occur. Some of the principal inadequacies that are to be avoided or corrected are as follows: (1) Pipes having inadequate strength to withstand loads of overlying fill or stresses applied by traffic. (2) Pipe joints unable to accommodate movements resulting from foundation or fill settlement. (3) Unsuitable backfill materials or inadequately compacted backfill. (4) Highpres sures from directional drilling that could result in hydro-fracturing the surroundin g materials. b . Some stat e and local laws prohibit pipes from passing through or under certain categories of levees. A s a general rule, this should not be done anyway , particularly in the case of pressure lines. However, since eachinstallation is unique, pipes in some instances may be allowed within the levee or foundation. Major factors to be considered in deciding if an existing pipe can remain in place under a new levee or must b e rerouted over the levee, or if a new pipe should be laid through or over the levee are as follows: (1) The height of the levee. (2) The duration and frequency of high water stages against the levee. (3) The susceptibility to piping and settlement of levee and foundation soils. (4) The type of pipeline (low or high pressure line, or gravity drainage line). (5) T he structural adequacy of existing pipe and pipe joints, and the adequa cy of the backfill compaction. (6) T he f easibility of providing closure in event of ruptured pressure lines, or in the event of failure of flap valves in gravity lines during high water. (7) The ease and frequency of required maintenance.EM 1110-2-1913

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8-2 

### (8) The cost of acceptable alternative systems. (9) Possible consequences of piping or failure of the pipe. (10) Previous experience with the owner in constructing and maintaining pipelines. General criteria for pipes crossing levees are given in Table 8-1.

Table 8-1 Criteria for Pipelines Crossing Levees Leaving Existing Pipeline in Foundations of New Pipeline Installation Pipelines Proposed Levees Pipes Through Levees Pipes Over Levee s Must be known to be in good condition XMust have adequate strength to withstand levee loading X X Must have adequate cover as needed to prevent damage by vehicular traffic or heavy equipment X Must have adequate cover for frost protection X Must have sufficient flexibility in joints to adjust under expected settlement and stretching of pipe X X X Pressure lines must have provisions for rapid closure in event of leakage or rupture X X X Gravity discharge pipes must have provisions for emergency closure in event of inoperative flap valves on riverside end X X Must have pervious backfill under landside third of levee where: a. Foundation materials are susceptible to piping X b. Levee materials are susceptible to piping X


### 8-2. General Considerations for Pipelines Crossing Through or Under Levees

a. G eneral . As has been noted previously, it is pref erable for all pipes to cross over a levee rather than p enetrate the embankment or foundation materials. This is particularly true for pipes carrying gas or fluid u nder pressure. Before considerati on is given to allowing a pressure pipe (and possibly other types of pipe) toextend through or beneath the levee, the pipe owner should provide an engineering study to support his r equest for such installation . The owner, regardless of the type of pipe, should show adequate capability to properly construct and/or maintain the pipe. Future maintenance of pipe by the owner must be carefull yEM 1110-2-1913 30 Apr 2000

8-3 

### evaluated. It may be necessary to form an agreement to the effect that should repairs to a pipe in the levee become necessary, the pipe will be abandoned, sealed, and relocated over the levee. b. Existing pipes (1) All existing pipelines must be located prior to initiation of embankment construction. As previously noted, in spection trenches may reveal abandoned pipes not on record. It is preferable that all abandone d pip es be removed during grubbing operations and the voids backfilled. Any existing pipe should meet or be made to meet the criteria given in Table 8-1. If this is not feasible and removal is not practical, the y shouldbe sealed, preferably by completely filling them with concrete. Sealed pipes must also meet th e criteria given in Table 8-1 relating to prevention of seepage problems. (2) Ingeneral, existing pressure pipes should be relocated over the proposed new levee. Rupture o r l eakage from such pipes beneath a levee produces extremely high gradients that can have devastating effects o n the in tegrity of the foundation. Therefore, as indicated by the criteria in Table 8-1, it is imperative that p ressure pipes be fitted with rapid closure valves or devices to prevent escaping gas or fluid from damaging the foundation. (3) Although

gravity drainage lines may be allowed or even required after the levee is completed, it is likely that existing pipes will not have sufficient strength to support the additional load induced by th e embankment. Therefore, existing pipes must be carefully evaluated to determine their supporting capacity before allowing their use in conjunction with the new levee.

c. New Pipelines . Generally, the only new pipelines allowed to penetrate the foundation or embank ment of the levee are gravity drainage lines. The number of gravity drainage structures should be keptto an absolu te minimum. The number and size of drainage pipes can be reduced by using suc h techniques as ponding to reduce the required pipe capacity. 8-3. General Considerations for Pipelines Crossing Over Levees I n the past the term and concept of freeboard was used to account for hydraulic, geotechnical, construction, operatio n and maintenance uncertainties. Pipelines crossing over the levee were encouraged to be withi n thefreeboard zone to reduce or eliminate many of the dangers that are inherent with pipelines crossin g through the embankment or foundation. The term and concept of fr eeboard to account for these uncertainties is no longer u sed in the design of levee projects. Therefore, since freeboard no longer exists, pipes mus t c ross over the completed levee cross section. Problems do exist, however, with pipelines crossing over the le vee. These pipes must be properly designed and constructed to prevent (a) flotation if submerged , (b) sco uring or erosion of the embankment slopes from leakage or currents, and (c) damage from debri s carriedby currents, etc. In some areas climatic conditions will require special design features. Guidance on design methods and construction practices will be given later in this chapter. 8-4. Pipe Selection

a . E M 1110-2-2902 contains a discussion of the advantage s and disadvantages of various types of pipe (i.e., corrugate d metal, concrete, cast iron, steel, clay, etc.). The selection of a type of pipe is largel y dependentupon the substance it is to carry, its performance under the given loading, including expecte d deflec tions or settlement, and economy. Although economy must certainly be considered, the overridin g factor must be safety, particularly where urban levees are concerned.EM 1110-2-1913

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8-4 

### b

. T he earth load acting on a pipe should be determined as outlined in EM 1110-2-2902. Consideration m ust also be given to live load s imposed from equipment during construction and the loads from traffic and maintenance equipment after t he levee is completed. The respective pipe manufacturers organizations have r ecommended procedures for accounting for such live loads. These recommended procedures should be followed unless the pipe or roadway owners have more stringent requirements.

c . R e quired strengths for standard commercially available pipe should be determined by the methods re commended

by the respective pipe manufacturers organizations. Where cast-in-place pipes are used , design proceduresoutlined in EM 1110-2-2902 should be followed. Abrasion and corrosion of corrugated s teel pipe should be accounted for in design using the method given in Federal Specification WW-P-405B(1) ( Appendix A) for the desired design life. The design life of a pipe is the length of time it will be in service without requiring repairs. The term does not imply the pipe will fail at the end of that time. Normally, a design life of 50 years can be economically justified. Corrugated pipe should always be galvanized an d p rotected by a bituminous or other acceptable coating as outlined in EM 1110-2-2902. Protective coatings may be considered in determining the design life of a pipe. d

. Leakagefrom or infiltration into any pipe crossing over, through, or beneath a levee must be prev ented. Theref

ore, the pipe joints as well as the pipe itself must be watertight. For pipes located within or beneaththe embankment, the expected settlement and outward movement of the soil mass must b e c onsidered. Where considerable settlement is likely to occur the pipe should be cambered (para 8-7). General ly, flexible corrugated metal pipes are preferable for gravity lines where considerable settlement i s expected. Corrugated metal pipe sections should be joined by exterior coupling bands with a gasket to assure w atertightness. Where a concrete pipe is required and considerable settlement is anticipated, a pressure-type jointwith concrete alignment collars should be used. The collars must be designed either to resist o r a ccommodate differential movement without losing watertight integrity. Where settlement is not significant, p ressure-type joints capable of accommodating minor differential movement are sufficient. Design details f or concrete collarsare shown in EM 1110-2-2902. Cast iron and steel pipes should be fitted with flexible b olted joints. St

eel pipe sections may be welded together to form a continuous conduit. All pressure pipes should be pressure tested at the maximum anticipated pressure before they are covered and put into use.

e . Duringthe design, the potential for electrochemical or chemical reactions between the substratum materials or groundwater and construction materi als should be determined. If it is determined that there will b e a reaction, then the pipe and/or pipe couplings should be protected. The protective measures to be taken may include the use of cathodic protection, coating of the pipe, or use of a corrosion-resistant pipe material. 8-5. Antiseepage Devices

a . Antiseepage devices have been employed in the past to prevent piping or erosion along the outside wa llof the pipe. The term “antiseepage devices” usually referred to metal diaphragms (seepage fins) o r concrete col lars that extended from the pipe into the backfill material. The diaphragms and collars were o ften referred to as “seepage rings.” However, many piping failures have occurred in the past where seepage rings were used. Assessment of these failures indicated that the presence of seepage rings often results in poorly compacted backfill at its contact with the structure. b

. Where pipes or conduits are to be constructed through new or existing levees: (1) Seepage rin gs or collars should not be provided for the purpose of increasing seepage resistance

. E xcept as provided herein,such features should only be included as necessary for coupling of pipe sections or to accommodate differential movement on yielding foundations. When needed for these purposes, collars with a minimum projection from the pipe surface should be used.EM 111-0-2-1913 30 Apr 2000 (2) A 0.45-m (18-in.) annular thickness of drainage fill should be provided around the landside third of the pipe, regardless of the size and type of pipe to be used, where lands ide levee zoning does not provide for such drainage fill. For pipe installations within the levee foundation, the 0.45-m (18-in.) annular thickness of drainage fill shall also be provided, to include a landside outlet through a blind drain to ground surface at the levee toe, connection with pervious underseepage features, or through an annular drainage fill outlet to ground surface around a manhole structure. Figure 8-1 shows typical sections of drainage structures through levees. Figure 8-2 shows typical precast conduits through the levee.

L.ANDSIDE

Dralna9e Fill

Inlet structure for concrete pipe**~** of Levee

Reinforced concrete pipe

elnforced concrete pipe RNERSIDE

Reinforced concrete outlet structure ,

0/sclxirQe pipes from pump/nQ plants rrey terminate In Qatewe/ls Outlet structure

Flap 9ate required for fast-rlslnQ streams
Figure 8-1. Typical sections, drainage structures through levees



### 8-6. Closure Devices



### a. All pipes allowed to penetrate the embankment or foundation of a levee must be provided with devices to assure positive closure. Gravity lines should be provided with flap-type or slide-type service gates on the riverside of the levee. Automatic flap-type gates are usually used where the water is likely to rise to the "Gate Closing Stage" rather suddenly and where the water stage is likely to fluctuate within a few feet above and below the "Gate Closing Stage" for prolonged periods of time during flood season. Automatic gates are also required on slower rising streams or bodies of water where frequent visits from operating personnel are not practical. 

### b. Slide-type gates are usually preferred as service gates where the rate ofrise of the water during major floods is slow, enough (minimum of 12-hr flood prediction time) to give ample time for safe operation. The principal advantages of the slide gate in comparison with automatic flap gates are greater reliability of operation and the ease with which emergency closure can be made in event obstructions prevent closure of the gate. Usually emergency closure can be made by filling the manhole with sandbags. The obvious

8-5EM 1110-2-1913 30 Apr 2000

Inlet Structure for Pipe lANDSIDE

\__Reinforced precast

concrete
Figure 8-2. Typical precast conduit (levees) LS 

## i of Levee Floor Stand RIVERSIDE

disadvantage of slide type gates is that personnel must be on hand for their operation. Also their initial cost is generally greater than that for a flap-type gate.



### c. A slide-type gate with a flap-type gate attachment is often used and affords the advantages of automatic flap gate operation with the added safety of the slide-type gate. Such installations usually eliminate the need for a supplemental emergency gate as described below. d. Experience has shown that service gates occasionally fail to close completely during critical flood periods because of clogging by debris, mechanical malfunctions, or other causes. This, of course, can cause flooding of, the protected areas. Supplemental emergency gates are intended to minimize these risks insofar as necessary and economically practical. For an emergency gate to be effective it must be located so that its controls are accessible during flood stage. Provisions required for emergency protection of other areas should be consistent with the risks and cost involved.



### e. Pressure pipes should be fitted with valves at various stations that can be closed rapidly to prevent gas or fluid from escaping within or beneath a levee should the pipe rupture within these areas. Provisions for closure of pressure pipes on the water side must also be provided to prevent backflow of floodwater into the protected area should the pipe rupture. These requirements should generally be followed in other areas, but may be relaxed to be consistent with the risks and costs involved. 

### 8-7. Camber The alignment of a gravity structure must be such as to provide for a continuous slope toward the outlet. Settlement of the embankment and foundation can significantly alter the initial grade line of a pipe. Therefore, the expected settlement of the levee must be considered in establishing the initial grade line. If the settlement will result in an upward gradient in the direction of flow or not allow the desired gradient to be maintained, the pipe should be cambered. The amount of camber required can usually be taken as the mirror image of the settlement curve along a line established by the final required grade. The camber should then be laid out, preferably as a vertical curve, on a grade such that all parts of the pipe will slope toward the outlet when installed. If the gradient of the pipe is limited and the camber will initially result in a slope away from the outlet, the portion of the pipe from the inlet up to the point of greatest load may be installed level. The remaining portion of the pipe is then installed on a vertical curve tangent to the first portion of the pipe.

8-6EM 1110-2-1913 30 Apr 2000

8-7 

### Regardless of the type of pipe selected, movements at the joints must be considered as discussed i n paragraph 8-4d. 8-8. Installation Requirements

a. General

. The installation of pipes or other structures within the levee or foundation probabl y requires th e greatest care and the closest supervision and inspection of any aspect of levee construction

. Most failures of levee systems have initiated at the soil-structure interface and therefore every effort must bemade to ensure that these areas are not susceptible to piping. Of overriding importance is goo d compactionof the backfill material along the structure. Pipes installed by open trench excavation shoul d be insta lled in the dry and a dewatering system should be used where necessary. Pipes installed b y directional drilling, microtunneling, or other trenchless methods require special consideration. b

. Pipes crossing through or beneath levees (1) Th e preferred method of installing pipes within the embankment or foundation of a levee ha s historical lybeen by the open cut method. Preferably, new levees should be brought to a grade about 610.8 m m (2 ft) above the crown of the pipe. This allows the soil to be preconsolidated before excavating the trench. The trench should be excavated to a depth of about 610.8 mm (2 ft) below the bottom of the pipe and at least 1.2 m (4 ft) wider than the pip e. The excavated material should be selectively stockpiled so that it can be replaced in a manner that will not alter the embankment zoning if there is some or will result in the more impervious soils on the riverside of the levee. (2) Afterthe trench has been excavated, it should be backfilled to the pipe invert elevation. In impervious zones, the backfill material should be compacted with mechanical compactors to 95 percent standard density at about optimum water content. (3) First-cla ss bedding should be used for concrete pipe and other rigid pipe, as shown in EM 1110-2- 2902 except no granular bedding should be used in impervious zones. For flexible pipe, the trench bottom shouldbe fla t to permit thorough tamping of backfill under the haunches of the pipe. Backfill should b e compacted to 95 perc ent standard density at about optimum water content. The backfill should be brought up evenly on both sides of the pipe to avoid unequal side loads that could fail or move the pipe. Special care must be taken in the vicinity of any protrusions such as joint collars to ensure proper compaction. Where granular filter material is required, it should be compacted to a minimum of 80 percent relative density. In areas where backfill compaction is difficult to achieve, flowable, low strength concrete fill has been use d to encapsulate pipes in narrow trenches. (4) In existing levees, the excavation slopes should be stable, meet OSHA criteria, but in no case b e steeper than 1V on 1H. The excavated material should be selectively stockpiled as was described for new levees. The pipe is installed as described in the previous paragraphs. Impervious material within 0.61 m (2 ft) of the pip e walls should be compacted to 95 percent standard density at optimum water content, with the remainder of the backfill placed at the density and water content of the existing embankment. (5) Installationof pipes in existing levees by directional drilling, microtunneling, tunneling or jacking may be considered. It is recognized, that in some instances, installation by the open cut method is no t feasible or cannot be economically justified. Where trenchless methods are allowed, special considerations are required. (6) Pipes under levees.EM 1110-2-1913

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8-8 

### (a) General. Pipes crossing beneath levees also require special considerations. Such crossing s sh ould be designed by qualified geotechnical engineers. Pipes constructed with open excavation method s should proceed in accordance wit h the requirements stated in the above paragraph, Pipes Crossing Through or Beneath Levees. If directional drilling or other trenchless methods are used, seepage conditions may be aggravatedby the collapse of levee foundation material into the annular void between the bore and pipe

. Penetration through the top stratum of fine-grained materials may concentrate seepage at those locations

. Pipes constructed with trenchless methods should proceed only after a comprehensive evaluation of th e following: comprehensive understanding of the subsurface soil and groundwater conditions to a minimum depthof 6.1 m (20 ft) below the lowest pipe elevation, locations of the pipe penetration entry and exit , construction procedure, allowable uplift pressures, on-site quality control and quality assurance monitoring during construction operation, grouting of the pipe annulus, backfilling of any excavated areas, and repair and reinstatement of the construction-staging areas. Guidance for construction of pipelines beneath levees using directional drilling is provided in Appendix A of WES CPAR- GL-98-1 (Staheli, et al. 1998). Guidance f o r construction of pipelines using microtunneling methods is provided in WES CPAR-GL-95-2 (Bennett, et al. 1995). (b) Pipes ins talled by directional drilling. The pipe entry or exit location, when located on th e protected(land) side, should be set back sufficiently from the land side levee toe to ensure that the pip e penetrate s some depth of a pervious sand stratum but is no less than 91.5 m (300 ft) from the centerline of the le vee crest. The pipe entry or exit location, when located on the unprotected (river) side, should b e located at least 6.1 m (20 ft) riverward of the levee stability control line. This is the distance between the riverside levee toe and an eroding bank line which will maintain the minimum design criteria for slop e stability. I f directiona

l drilling is to be used, the depth of the pipe under the levee should be at a level to maintain anadequate factor of safety against uplift from the pressurized drilling fluid during the drilling operation. A positive means of maintaining an open ven t to the surface should be required whether through bored holes or downhole means while installing the drill pipe. T he drilling fluid should consist of a noncolloidal lubricating admixture to ensure suspension and removal of drilling cuttings. The pilot hole should be advanced at a rate to maintain a continuous return flow. The annularspace should be sufficient to ensure that no blockage occurs with the drilling cuttings. Th e prereamer boring diameter should be of sufficient size to ensure that the production pipe can be advanced without delay and undue stress to the surrounding soils. The prereamer boring operation should b e contin uous for the down-slope and up-slope cutting segments. Excessive drilling fluid pressures can hydraulically fracture the levee foundation and levee embankment and should be avoided. Whereeconomically feasible, the pipeline should be bored through rock where the pipeline crosses the levee centerline. The m aximum allowable mud pressure acting against the borehole wall should be evaluated using th e Delftequa tion presented in the Appendix A of WES CPAR-GL-98-1 (Staehli, et al., 1998). Durin g construction, the actual mud pressure existing in the borehole must be measured by a pressure measuring deviceloc ated on the outside of the drill string no more than 5 ft from the drill bit. The drilling operato r should be required to monitor these pressures and adjust the drilling mud pressure so as not to exceed the maximum pressure determined by Delft equation. Wherethe casing pipe is carrying multiple fibre optic cables and each cable is installed within its own HDPEinner duct, the detail shown in Figure 8-3a should be used to prevent preferred seepage path (both external and internal). The casing pipe must end in the encasements.EM 1110-2-1913 30 Apr 2000

8-9 

### Thedirectional drilling contract should be required to show proof that all of his pressure sensors an d readout devices have been calibrated by a national standard within the last 6 months. A full time inspector, not on directional drilling contractor’s payroll, should be required to observe the construction. The dri lling fluid should be processed through an active drilling mud conditioning unit to remove th e cuttings from the drill fluid and maintain its viscosity.

c. Pipes crossing over levees . Pipe crossings on the surface of the levee should be designed to counteract uplift of the empty pipe at the design high water stage. Th is may be accomplished by soil cover, anchors, headwalls, etc. All pipes on the riverside of the levee should have a minimum of 305 mm (1 ft) of soil cover for protection from debris during high water. It is desirable for pipe on the landward side to also be covered withsoil. P ipes crossing beneath the levee crown should be provided with sufficient cover to withstan d vehicular traffic as outlined in paragraph 8-4b. Depth of cover should also be at least the depth of local frost protection. Where mounding of soil over the pipe is required, the slope should be gentle to allow mowing equipment or other maintenance equipment to operate safely on the slopes. The approach ramps on the levee crownshould not exceed 1V on 10H in order to allow traffic to move safely on the crown. The trenching details for pipelines cross-up and over-levees are shown in Figure 8-3b and Figure 8-3c. Section II Access Roads and Ramps 8-9. Access Roads

a. Access road to levee . Access roads should be provided to levees at reasonably close intervals i n cooperation with state and loc al authorities. These roads should be all-weather roads that will allow access for the purpose of inspection, maintenance, and flood-fighting operations. b. Access road on levee . Access roads, sometimes referred to as patrol roads, should be provided also on top of the levees for the general purpose of inspection, maintenance, and flood-fighting operations. This type of road should be surfaced with a suitable gravel or crushed stone base course that will permit vehicle access during wet weather without causing detrimental effects to the levee or presenting safety hazards to the levee inspection and maintenance personnel. The width of the road surfacing will depend upon the crown width of the levee, where roadway additions to the crown are not being used, and upon the function of the roadway in accommodating either one- or two-way traffic. On levees where county or state highways will occupy the crown, the type of surfacing and surfacing width should be in accordance with applicable county or state standards. The decision as to whether the access road is to be opened to public use is to be made by the local levee agency which owns and maintains the levee. (1) Turnouts. Turnouts should be used to provide a means for the passing of two motor vehicles on a one-lane access road on the levee. Turnouts should be provided at intervals of approximately 762 m (2500 ft), provided there are no ramps within the reach. The exact locations of the turnouts will b e dependen t upon various factors such as sight distance, property lines, levee alignment, and desires of local interests. An example turnout for a levee with a 3.65 m (12-ft) levee crown is shown in Figure 8-4. (2) Turna rounds. Turnarounds should be provided to allow vehicles to reverse their direction on al l levees where the levee dead ends, and no ramp exists in the vicinity of the deadend. An example turnaround for a levee with a 3.65-m (12-ft) crown is shown in Figure 8-5.EM 1110-2-1913 30 Apr 2000

TO MANHOLE



### ----------------- CONCRETE ENCASEMENT

# ~ OVERLYING GLAY

# B~

COARSE GRAlN AQUIFER/
a. Detail of end casing (for pipe lines beneath the levees)

VERTICAL TRENCH WALLS

BACKFILL, COMPACTED IN 6-INCH LIFTS

BEDDING

b. On riverside, within 50 ft of levee (for pipe lines cross-up and over-levees)

BACKFILL, COMPACTED IN 6-INCH LIFTS

c. On landside (for pipelines cross-up and over-levees)
Figure 8-3. Details of pipeline levee crossing 8-10Figure 8-4. Example of levee turnout LAND SIDE



## a**~...,.** 

### --+---r-:

.32m 24' 15.24-m 50' RIVERSIDE

LANDSIDE

RIVERSIDE
Figure 8-5. Example of levee turnaround



### 8-10. Ramps 7.32m 24-' EM 1110-2-1913 30 Apr 2000



### a. Ramps should be provided at sufficient locations to permit vehicular traffic to access onto and from the levee. Ramps may be located on both the landside and the riverside of the levee. Ramps on the landside ofthe levee are provided to connect access roads leading to a levee with access roads on top of a levee and
8-11EM 1110-2-1913

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8-12 

### atother convenient locations to serve landowners who have property bordering the levee. Ramps are also provided on some occasions on the riverside of the levee to connect the access road on top of the levee with existing levee traverses where necessary. The actual locations of the ramps should have the approval of the local levee agency which owns and maintains the levee. When used on the riverside of the levee, they should be oriented to minimize turbulence during high water. b

. Ramps are classified as public or private in accordance with their function. Public ramps are designed to satisfy the requirements of the levee owner: state, county, township, or road district. Private ramps are usually designed with less stringent requi rements and maximum economy in mind. Side-approach ramps should be used instead of right angle road ramps because of significant savings in embankment. The width of the ramp will depend upon the intended function. Some widening of the crown of the levee at its junctu re with the ramp may be required to provide adequate turning radius. The grade of the ramp should beno steeper than 10 percent. Side slopes on the ramp should not be less than 1V on 3H to allow grass

c utting equipment to operate. The ramp should be surfaced with a suitable gravel or crushed stone. Consideratio n should be given to extending the gravel or crushed stone surfacing to the levee embankment to minimize erosion in the gutter. In general, private ramps should not be constructed unless they are essential and there is assurance that the ramps will be used. Unused ramps lead to maintenance neglect.

c . Both public and private ramps should be constructed only by adding material to the levee crown and slopes. The levee section should never be reduced to accommodate a ramp. Section III Levee Enlargements 8-11. General Theterm levee enlargement pertains to that addition to an existing levee which raises the grade. A higher levee grade may be required for several reasons after a levee has been constructed. Additional statistical information gathered from recent floodings or recent hurricanes may establish a higher project floo d elevation on a river system or a higher elevation for protection from incoming tidal waves produced b y hu rricaneforces in low-lying coastal areas. The most economical and practical plan that will provid e additional protection is normally a levee enlargement. Levee enlargements are constructed either by adding additional earth fill or by constructing a flood-wall, “I”-type or “inverted T”-type, on the crown. 8-12. Earth-Levee Enlargement

a . The earth-levee enlargement is normally preferred when possible, since it is usually more economical. This type of enlargement is used on both agricultural and urban levees where borrow sites exist nearb y and sufficient right-of-way is available to accommodate a wider levee section. b

. An earth-levee enlargement is accomplished by one of three different methods: riverside, straddle, or landside enlargem

ent. A riverside enlargement is accomplished by increasing the levee section generally at the crown and on the riverside of the levee as shown in Figure 8-6a. A straddle enlargement i s accomplished by increasing the levee section on the riverside, at the crown, and on the landside of the leveeas shown in Figure 8-6b. A landside enlargement is accomplished by increasing the levee section, generally at the crownand on the landside of the levee as shown in Figure 8-6c. There are advantages an d disa dvantages to each enlargement method that will have to be looked at for each project. The riverside enlargement

would be more costly if the riverside slope has riprap protection and it could also be an encroachment for nar

row floodways that would impact top of levee designs. Landside enlargements would require additional right-of-way and larger fill quantities for levees with flatter landside slopes. The strattleEM 1110-2-1913 30 Apr 2000 enlargement would require the whole levee system to be stripped with work being done on both sides of the levee.

RIVERSIDE:

a. Riverside levee enlargement

RIVERSIDE

b. Straddle levee enlargement

RIVERSIOE



### c. Landside levee enlargement

Figure 8-6. Enlargements 

### It 

# I**~** 

# I l.AWDSIOE

LANDSIDE OfUGINAI. &ROIJNO SURI'ACE



### c. The modified levee section should be checked for through seepage and underseepage as discussed in Chapter 5 and for foundation and embankment stability as discussed in Chapter 6. Sufficient soil borings should be taken to determine the in situ soil properties ofthe existing levee embankment for design purposes. d. An earth-levee enlargement should be made integral with the existing levee. Every effort should be made such that the enlargement has at least the same degree of compaction as the existing levee on which it is constructed. Preparation of the interface along the existing levee surface and upon the foundation should be made to ensure good bond between the enlargement and the surfaces on which it rests. The foundation surface should be cleared, grubbed, and stripped as described in Chapter 6. The existing levee surface upon which the levee enlargement is placed should also be stripped of all low-growing vegetation and organic
8-13EM 1110-2-1913

30 Apr 2000

Structural design of crest walls is given in ETL 1110-2-341. 1
8-14 

### topsoil. The

topsoil that is removed should be stockpiled for reuse as topsoil for the enlargement. Prior to constructingthe enlargement, the stripped surfaces of the foundation and existing levee should be scarified before the first lifts of the enlargements are placed. 8-13. Floodwall-Levee Enlargement

a . A floodwall-levee enlargement is used, when additional right-of way is not available or is too expensive or if the foundation conditions will not permit an increase in the levee section. Economic justification of floodwall-levee enlargement cannot usually be attained except in urban areas. Two common types o f floodwalls that are used to raise levee grades are the I wall and the inverted T wall. 1 

### b

. The I floodwall is a vertical wall partially embedded in the levee crown. The stability of such walls depends upon the development of passive resistance from the soil. For stability reasons, I floodwalls rarely exceed 2.13 m (7 ft) above the ground surface. One common method of constructing an I floodwall is by combiningsheet pile with a concrete cap as shown in Figure 8-7. The lower part of the wall consists of a row of st eel sheet pile that is driven into the levee embankment, and the upper part is a reinforced concrete section capping the steel piling.

c . An inverted T floodwall is a reinforced concrete wall whose members act as wide cantilever beams in resisting hydrostatic pressures acting against the wall. A typical wall of this type is shown in Figure 8-8. The inverted T floodwall is used to make floodwall levee enlargements when walls higher than 2.13 m (7 ft) are required. d

. The floodwall should possess adequate stability to resist all forces which may act upon it. An I floodwall is considered stable if sufficient pass ive earth resistance can be developed for a given penetration of the wallinto the levee to yield an ample factor of safety against overturning. The depth of penetration of the I wall should be such that adequate seepage control is provided. Normally the penetration depth of the I wall required for stability is sufficient t o satisfy the seepage requirements. For the inverted T floodwall, the wall sh ould have overall dimensions to satisfy the stability criteria and seepage control as presented i n EM 1110-2-2502.

e . The existing levee section should be checked for through seepage and underseepage as discussed in Chapter 5 and for embankment and foundation stability as discussed in Chapter 6 under the additional hydrostaticforces expected. If unsafe seepage forces or inadequate embankment stability result from the higher heads, seepa

ge control methods as described in Chapter 5 and methods of improving embankment stability as described i n Chapter 6 may be used. However, some of these methods of controlling seepage an d improving embankment stability may require additional right-of-way for construction which could eliminate the economic advantages of the floodwall in comparison with an earth levee enlargement. As in earth levee enlargeme nts, a sufficient number of soil borings should be taken to determine the in situ soil properties of the existing levee embankment for design purposes.

# -<' FLOODWALL, SEE

- -... DETAIL "A"

# ~·~~

Figure 8-7. 1-type floodwall-levee enlargement

/FLODDWALL, SEE \ DETAIL"A"

Figure 8-8. Inverted T-type floodwall-levee enlargement 

# -

DETAIL "A"

DETAIL "A" EM 1110-2-1913 30 Apr 2000

8-15EM 1110-2-1913

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8-16 

### Section IV Junction with Concrete Closure Structures 8-14. General In some areas, a flood prot

ection system may be composed of levees, floodwalls, and drainage control structures (gated structures, pumping plants, etc.). In such a system, a closure must be made between the levee and the concrete struct

ure to complete the flood protection. One closure situation occurs when the levee ties into a concrete floodwall or a cutoff wall. In this closure situation the wall itself is usually embedded in the leve e embankment. In EM 1110-2-2502 a method of making a junction between a concrete floodwall an d leveeis d iscussed and illustrated. Another closure situation occurs when the levee ties into a drainag e contr olstructure by abutting directly against the structure as shown in Figure 8-9. In this situation th e abutting end walls of the concrete structure should be battered 10V on 1H to ensure a firm contact with the fill. 8-15. Design Considerations Whenjo ining a levee embankment with a concrete structure, items that should be considered in the desig n of the junction are differential settlement, compaction, and embankment slope protection.

a. D i fferential settlement . Differential settlement caused by unequal consolidation of the foundation soilat the junction between a relatively heavy levee embankment and a relatively light concrete closure struct urecan be serious if foundation conditions are poor and the juncture is improperly designed

. Preloading has been used successfully to minimize differential settlements at these locations. In EM 1110-2- 2502 a transiti oning procedure for a junction between a levee embankment and a floodwall is presented that minimizes the effect of differential settlement. b. Compaction . Thorough compaction of the levee embankment at the junction of the concrete structure and levee is essential. Good compaction decreases the permeability of the embankment material and ensures a fir m contact with the structure. Heavy compaction equipment such as pneumatic or sheepsfoot roller s should be used where possible. In confined areas such as those immediately adjacent to concrete walls, compaction should be by hand tampers in thin loose lifts as described in EM 1110-2-1911.

c. Seepage . Seepage needs to be analyzed to determine the embedment length of the structure-leve e junction. Zoning of the embankment materials needs to be maintained through the junction unless analysis indicates different zoning is required. d. Slope pro tection . Slope protection should be considered for the levee embankment at all junctions of levees with concrete closure structures. Turbulence may result at the junction due to changes in th e geometry between t

he levee and the structure. This turbulence will cause scouring of the levee embankment if slope protection is not provided. Slope protection for areas where scouring is anticipated is discussed in paragraph 7-6.

## -

.... - 

## f"**~**

# tl~**~** / 

## 7

........................... 

# -1**~**

# ~~~**~**

# ~~~ ;J 

# MR GATES 

### \ 

## \ '--' 

### € LEVEE 

# >.t:::: ,___)><
fEJ 

# wL1HJJ Br**~** 

# y?

BATTERED 10v ON 1h

# -~

.............

## ~~~ 7

......... 

## PLAN SCALES 30m 0 60FT 0

- M M I



## SECTION A-A SCALES 10m 0 10m

# ~~**~~**

# ~f

30m

60FT

I

40FT 0 40FT 

# --I I

Figure 8-9. Junction of levee and drainage structure I



# v I

....... EM 1110-2-1913 30 Apr 2000

.........

### ~

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## _..,.lL /

8-17EM 1110-2-1913

30 Apr 2000

8-18 

### Section V Other Special Features 8-16. Construction of Ditches Landside of Levee Sometimes requests are made to locate irrigation and/or drainage ditches in close proximity to the landside levee toe. Such ditches ma y lead to serious seepage and/or slope stability problems. The location and depth of pr oposed ditches should be established by seepage and stability analyses. This requires information o n foundation soil conditions, river stages and geometry of the proposed ditch. Drainage dit

ches should be located such that the exit gradient in the bottom of the ditch does not exceed 0.5 at the landside levee toe and does not exceed 0.8 at a distance 45.72 m (150 ft) landward of the landside levee toe and beyond. Between the landside levee toe and 45.72 m (150 ft) landward of the landside leve e toe, the maximum allowable exit gradient in the bottom of the ditch should increase linearly from 0.5 to 0.8. The exit gradient should be computed assuming the water level in the ditch is at the bottom of the ditch. 8-17. Levee Vegetation Management To protect or enhance esthetic values and natural resources, vegetation on a levee and its surrounding areas (trees, bushes and grasses) is an important part of design considerations. Vegetation can be incorporated in the p roject as long as it will not diminish the integrity and the functionality of the embankment system or imped e ongoing operations, maintenance and floodfighting capability. A multidiscipline team includin g structural and geotechnical engineers, biologists and planners should evaluate the vegetation design or proposal. Coordination with local governments, states and Native American tribes may be needed during th e design process. EM 1110-2-301 and ER 500-1-1 are two documents covering the vegetation polic y applicable to both federal levees and non-federal levees under the PL-84-99 program.EM 1110-2-1913 30 Apr 2000

A-1 

### Appendix A References
A-1. Required Publications TM 5-818-5 Dewatering and Groundwater Control for Deep Excavations ER 500-1-1 Natural Disaster Procedures ER 1110-2-1806 Earthquake Design and Evaluation for Civil Works Projects EM 1110-2-301 Guidelines for Landscape Planting at Floodwalls, Levees, and Embankment Dams EM 1110-2-1601 Hydraulic Design of Flood Control Channels EM 1110-2-1614 Design of Coastal Revetments, Seawall, and Bulkheads EM 1110-1-1802 Geophysical Explorations for Engineering and Environmental Investigations EM 1110-2-1901 Seepage Analysis and Control for Dams EM 1110-1-1904 Settlement Analysis EM 1110-1-1906 Soils Sampling EM 1110-2-1902 Stability of Earth and Rock-Fill DamsEM 1110-2-1913

30 Apr 2000

A-2 

### EM 1110-2-1906 Laboratory Soils Testing EM 1110-2-1908 Instrumentation of Embankment Dams and Levees EM 1110-2-1911 Construction Control for Earth and Rock-Fill Dams EM 1110-2-1914 Design, Construction, and Maintenance of Relief Wells EM 1110-2-2300 Earth and Rock-Fill Dams General Design and Construction Considerations EM 1110-2-2502 Retaining and Flood Walls EM 1110-2-2902 Conduits, Culverts, and Pipes Federal Specification WW-P-405B(1) Corrugated Steel Pipe U .S. Army Engineer Waterways Experiment Station, CE, “Soil Mechanics Design, Stability of Slopes and Foundations,” Technical Memorandum No. 3-777, Feb 1952, P.O. Box 631, Vicksburg, Miss. 39180 U .S. Army Engineer Waterways Experiment Station, CE, “Underseepa ge and Its Control, Lower Mississippi R iver Levees,” Technical Memorandum No. 3-424, Vol I, Oct 1956 , P.O. Box 631, Vicksburg, Miss. 39180 U .S. Army Engineer Division, Lower Mississippi Valley, CE, “Design Procedures for Design of Landside Seepage Berms for Mississippi River Levees,” P.O. Box 80, Vicksburg, Miss. 39180 U .S. Army Engineer District, Rock Island, CE, “Engineering and Design Studies for Underseepage Control (Slurry Trench Cutoff) for Saylorville Dam, Des Moines River, Iowa,” Design Memorandum, Nov 1965, Clock Tower Bldg., Rock Island, Ill. 61201 U.S. Army Engineer District, Savannah, CE, “West Point Project, Chatahoochee River, Alabama an d Georgia, Construction of Slurry Trench Cutoff,” May 1968, P.O. Box 889, Savannah, Ga., 31402EM 1110-2-1913 30 Apr 2000

A-3 

### Tuck and Torrey 1993 T uck, G. F. and Torrey, V. H., III, Upper Mississippi River Basin Flood of 1993 Flood-Fight Reconnaissance a nd Survey of Expedient Methods Employed , December 1993, U.S. Army Engineer Waterways Experiment Station, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199 NAVF AC, Soil Mechanics Foundations and Earth Structures, Design Manual 7, Mar 1971. U.S. Naval Publications and Forms Center, 5801 Tabor Avenue, Philadelphia, Pennsylvania 19120 A-2. Related Publications Bennett, Guice, Khan, and Staheli 1995 Bennett, R. D., Guice, L. K., Khan, S., and Staheli, K., 1995, “Guidelines for Trenchless Technology : C ured-in Place Pipe (CIPP), Fold and Formed Pipe (FFP) Mini-Horizontal Directional Drilling (mini-HDD) M icrotunneling,” Construction Productivity Advancement Research (CPAR) Program, GL-95-2, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. Bhowmik 1994 Bhowmik, N. G., et al., The 1993 Flood on the Mississippi River in Illinois , January 1994, Illinois State Water Survey Miscellaneous Publication 151, 2204 Griffith Drive, Champaign, IL 61820 Biedenharn and Tracy 1987 Bieden harn, D. G., and Tracy, F. T., 1987, “Finite Element Method Package for Solving Steady-State SeepageProblems,” Technical Report ITL-87-6, U.S. Army Engineer Waterways Experiment Station , Vicksburg, MS Bjerrum 1972 B jerrum, L., ”Embankments on Soft Ground,” Proceedings, Specialty Conference on Performance of Earth a nd Earth-Supported Structures, Vol II, 11-14 June 1972. ASCE, 345 East 47th St., New York, New York 10017 Blasters’’ 1966 B lasters’’ Handbook, 15th ed., E. 1 . Dupont de Nemours and Co., Inc., 1966, Wilmington, Delaware 19898 Brizendine, Taylor, and Gabr 1995 Brizendi ne, A. L., Taylor, H. M., Jr., and Gabr, M. A., 1995. “LEVSEEP: Analysis Software for Leve e Underseepage and Rehabilitation,” Technical Report GL-9 5-10, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS Butler and Llopis B utler , Dwain K., and Llopis, Jose L., “Assessment of Anomalous Seepage Conditions,” Geotechnical and E n vironmental Geophysics, Vol. II, pp. 153-173, Environmental and Groundwater, Society of Exploration Geophysicists, P.O. Box 702740, Tulsa, OK 74170-2740. Dobrin 1960 D obrin, M. B., Geophysical Prospecting, 1960, McGraw Hill Publis hing Co., 1221 Avenue of The Americas, New York, New York, 10020 Engineering Computer Graphics Laboratory 1996 EngineeringComputer Graphics Laboratory, 1996, “FastSEEP Automated Seepage Analysis Referenc e Manual,” Brigham Young University, Provo, UTEM 1110-2-1913

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A-4 

### Gabr, Brizendine, and Taylor 1995 G abr, M . A., Brizendine, A. L., and Taylor, H. M., Jr., 1995, “Comparison Between Finite Element Study andS implified Analysis of Levee Underseepage,” Technical Report GL-95-11, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS Gabr, Taylor, Brizendine, and Wolff 1995 G abr, M. A., Taylor, H. M., Jr., Brizendine, A. L., and Wolff, T. F., 199 5, “LEVEEMSU: Analysis Software for Levee Underseepage and Rehabilitation,” Technical Report GL-95-9, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS General Accounting Office 1995 G eneral Accounting Office, Midwest Flood: Information on the Performance, Effects, and Control of Levees , A ugust 1995, GAO/RCED-95-125, Resources, Community , and Economic Development Division, P.O. Box 6015, Gaithersburg, MD 20884-6015 Interagency Floodplain Management Review Committee 1994 In teragencyFloodplain Management Review Committee, Sharing the Challenge: Floodplain Management In tothe 21st Century , June 1994, Report to the Administration Floodplain Management Task Force , G overnment P

rinting Office, Superintendent of Documents, P.O. Box 371954, Pittsburgh, PA 15250-7954 Johnson 1970 Johnson, S. J., “Foundation Precompression with Vertical Sand Drains,” Journal, Soil Mechanics an d F oundations Division, American Society of Civil Engineers, Jan 1970, ASCE, 345 East 47th St., New York, New York 10017 Kapp, York, Aronowitz, and Sitomer 1966 K app, M. S., York, D. L., Aronowitz, A., and Sitomer, H., “Construct ion on Marshland Deposits: Treatment a nd Results,” Utilization of Sites of Soft Foundations Highway Research Record No. 133, pp 1-22, 1966, Transportation Research Board, 2101 Constitution Avenue, N. W., Washington, D. C. 20418 Knowles 1992 Knowles, V. R., 1992, “Applications of the Finite Element Seepage Analysis Corps Program CSEEP ( X8202),” Technical Report ITL-92-6, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS Ladd and Foott 1974 Ladd, C harles C., and Foott, Roger, 1974, “New Design Procedure for Stability of Soft Clays, Vol. 10 0 No. GT7, Journal of the Geotechnical Engineering Division. Sherard 1979 Sherard, J. L., 1979, “Sinkholes in Dams of Coarse, Broadly Graded Soils,” Transaction of the 13th International Congress on Large Dams , New Delhi, India, Vol. 11, pp 25-35. Staheli, Bennett, O’Donnell, and Hurley 1998 S taheli, K., Bennett, D., O’Donnell, H. W., and Hurley, T. J., 199 8, “Installation of Pipelines Beneath Levees U sing Horizontal Directional Drilling,” Const ruction Productivity Advancement Research (CPAR) Program, GL-98-1,U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.EM 1110-2-1913 30 Apr 2000

A-5 

### Telford, Geldart, Sheriff, and Keys 1990 Te lford, W. M., Geldart, L. P., Sheriff, R. E., and Keys, D. A., 1990, “Applied Geophysics,” Cambridg e University Press, New York. Tobin 1995 T obin, G. A., “The Levee Love Affair: A Stormy Relationship,” Water Resources Bulletin , Vol 31, No. 3, 1995, American Water Resources Association, 950 Herndon Parkway, Herndon, VA 22070-5531 Tracy 1994 Tracy, F. T., 1994, “Seepage Package,” CSEEP Micro Version, X8202, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS Turnbull and Mansur 1959 Turnbull, W. J . and Mansur, C. I., “Design of Underseepage Control Measures for Dams and Levees, ” J ournal, Soil Mechanics and Founda tions Division, American Society of Civil Engineers, Oct. 1959, ASCE, 345 East 47th St., New York, New York 10017 Turnbull and Mansur 1959 Turnbull, W. J. and Mansur, C. I., “Construction and Maintenance of Underseepage Control Measures, ” J ournal, Soil Mechanics and Foundations Division, American Society of Civil Engineers, Dec. 1959, ASCE, 345 East 47th St., New York, New York 10017 Wolff 1989 Wolff, T. F., 1989, “LEVEEMSU: A Software Package Designed for Levee Underseepage Analysis, ” Technical Report GL-89-13, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS ASTM D 1056 American Society for Testing and Materials, 1916 Race Street, Philadelphia, Pennsylvania 19103 ASTM D 2573 American Society for Testing and Materials, 1916 Race Street, Philadelphia, Pennsylvania 19103. AASHTO M 243-73 American Association of State Highway and Transportation Officials , 341 National Press Bldg., Washington, DC. 20004EM 1110-2-1913 30 Apr 2000

B-1 

### Appendix B Mathematical Analysis of Underseepage and Substratum Pressure B-1. General The design of seepage control measures for levees often requires an underseepage analysis without the use o f piezome tric data and seepage measurements. Contained within this appendix are equations by which an estimate of seepage flow and substratum pressures can be made, provided soil conditions at the site are reasonablywell defined. The equations contained herein were developed during a study (reported i n U.S. Army Engineer Waterways Experiment Station TM 3-424 (Appendix A) of piezometric data an d seepage measurements along the Lower Mississippi River and confirmed by model studies. It should b e emphasized that the accuracy obtained from the use of equations is dependent upon the applicability of the equation to the condition being analyzed, the uniformity of soil conditions, and evaluation of the variou s f actors involved. As is normally the case, sound engineering judgment must be exercised in determining soil profiles and soil input parameters for these analyses. B-2. Assumptions I t is necessary to make certain simplifying as sumptions before making any theoretical seepage analysis. The following is a list of such assumptions and criteria necessary to the analysis set forth in this appendix.

a . S eepage may enter the pervious substratum a t any point in the foreshore (usually at riverside borrow pits) and/or through the riverside top stratum. b

. Flow through the top stratum is vertical.

c . Flow through the pervious substratum is horizontal. d

. The levee (in cluding impervious or thick berms) and the portion of the top stratum beneath it i s impervious.

e . All seepage is laminar. I n addition to the above, it is also required that the foundation be generalized into a pervious sand or gravel stratum witha uniform thickness and permeability and a semipervious or impervious top stratum with a uniformthickness and permeability (although the thickness and permeability of the riverside and landsid e top stratum may be different). B-3. Factors Involved in Seepage Analyses T he volume of seepage (Q ) that will pass beneath a levee and the artesian pressure that can develop under s 

### and landward of a levee during a sustained high water are related to the basic factors given and defined in TableB-1 and shown graphically in Figure B-1. Other values used in the analyses are defined as they are discussed in subsequent paragraphs.EM 1110-2-1913

30 Apr 2000

B-2 

### B-4. Determination of Factors Involved in Seepage Analyses T able B-2 contains a brief summary of method s normally used to determine the factors necessary to perform a seepage analysis. The determination of these factors is discussed in more detail in the followin g paragraphs. Many of the methods given, such as exploration and testing, have previously been mentioned i n the text; however, they will be discussed herein in more detail as they apply to each specific factor. The u se of piezometric data, although rarely available on new projects, is mentioned primarily because it is not infrequent for seepage analyses to be performed as a part of remedial measures to existing levees in which case piezometric data often are available.

Table B-1 Factors Involved in Seepage Analyses Factor Definition H Net head on levee M Slope of hydraulic grade line (at middepth of pervious stratum) beneath levee i Critical gradient for landside top stratum c L Distance from river to riverside levee toe 1 L Base width of levee and berm 2 L Length of foundation and top stratum beyond landside levee toe 3 L Distance from effective seepage entry to effective seepage exit
s Distance from effective seepage entry to landside toe of levee or berm X Distance from effective seepage entry to riverside levee toe 1 X Distance from landside levee toe to effective seepage exit 3 d Thickness of pervious substratum
z Thickness of top stratum
z Transformed thickness of top stratum b z Transformed thickness of landside top stratum bl z Transformed thickness of riverside top stratum br z Thickness of individual layers comprising top stratum (n = layer number) n z Transformed thickness of landside top stratum for uplift computation t k Vertical permeability of top stratum b k Vertical permeability of landside top stratum bl k Vertical permeability of riverside top stratum br k Horizontal permeability of pervious substratum f k Vertical permeability of individual layers comprising top stratum (n = layer number) n Q Total amount of seepage passing beneath the levee s h Head beneath top stratum at landside levee toe o h Head beneath top stratum at distance x from landside levee toe xEM 1110-2-1913 30 Apr 2000

B-3 Table B-2 Methods for Determination of Design Parameters Factor Method of Determination H From design flood stage or net levee grade k , k From laboratory tests, estimations, and transformations bl br k Field pump tests, correlations f z Foundation exploration, knowledge of depth and locations of borrow pits, ditches, etc. b z , z From transformations bl br d Foundation exploration i From equation B-9 c M From piezometers or from determining effective entrance and exit points of seepage L From maps 1 L From preliminary or existing levee section 2 L From foundation exploration and knowledge of location of levee 3 s From piezometric data or estimated from equations
x From knowing M or from equation B-7 or B-8 1 x From knowing M or from equation B-3, B-3A, B-4, B-5, or B-6 3 Q From equation B-11 or B-12 s h From piezometric data or estimated from equations o h From piezometric data or estimated from equations x



### a. Net

head, H . The net head on a levee is the height of water on the riverside above the tailwater or n aturalground surface on the landside of the levee. H is usually based on the design or project flood stage but is sometimes based on the net levee grade. b. Thickness, z and vertical permeability, k , of top stratum

. b 

### (1) Exploration. The thickness of the top stratum, both riverward and landward of the levee, is extremely important in a seepage analysis. Exploration to determine this thickness usually consists of auger borings with samples taken at 0.91- to 1.52-m (3- to 5-ft) intervals and at every change of material. Boring spacing will depend on the pote

ntial severity of the underseepage problem but should be laid out so as to sample the b asic geologic features with inte rmediate borings for check purposes. Landside borings should be sufficient t o delineate any significant geological features as far as 152.4 m (500 ft) away from the levee toe. The effect of ditches and borrow areas must be considered. (2) Tran sformation. The top stratum in most areas is seldom composed of one uniform material bu t r ather usually consists of several layers of different soils. If the in situ vertical permeability of each soil (k ) n 

### is known , it is possible to transform an overall effective thickness and permeability. However, if goo d judgment is exercised in selection of these values, a reasonably accurate seepage analysis can be made by u sing a simplified procedur e. Basically this procedure consists of assuming a uniform vertical permeabilityEM 1110-2-1913 30 Apr 2000

for the generalized top stratum equal to the permeability of the most impervious strata and then using the transformation factor given in equation B-1 to determine a corresponding thickness for the entire top stratum.


### A POINT OF EFFECTIVE SEEPAGE ENTRY B - POINT OF EFFECTIVE SEEPAGE EXIT**~ ~r---------------~s~------------------~4---~X**  L
Figure B-1. Illustration of symbols used in Appendix B

kb F =-

I k II where F 1 = transformation factor. (B-1)

If the in situ thickness of each soil layer (z 0 ) is known, the value of corresponding transformed thickness (z 1) can be expressed as kb 

### z, = Z 11 F 1 

### = Z 11 

## k
II The total in situ thickness (z) and total transformed can be expressed as

II z = 

# L zll

II zb = 

# L z, 1 Some examples using this procedure are given in Table B-3 and in Figure B-2.

B-4 (B-la)

(B-lb)

(B-lc)F t ' K b K n

k f ' Q s M · d EM 1110-2-1913 30 Apr 2000

B-5 Table B-3 Examples of Transformation Procedure Actual Actual Transformed Thickness, Thickness Permeability z , m (ft) t Strata z , m (ft) cm/sec (k = 1x 10 cm/sec) n b -4 Clay 1.52 (5) 1 x 10 1 1.52 (5.0) -4 Sandy silt 2.44 (8) 2 x 10 1/2 1.22 (4.0) -4 Silty sand 1.52 (5) 10 x 10 1/10 0.15 (0.5) -4 z = 5.48 (18) z = 2.90 (9.5) b



### A generalized top stratum having a uniform permeability of 1 x10 cm/sec and 2.9 m (9.5 ft) thick would -4 

### then be used in the seepage analysis for computation of the length to the effective seepage exit. However, the thickness z may or may not be the effective thickness of the landside top stratum z that should be used

b t 

### i n determining the allowable pressure beneath the top stratum. The transformed thickness of the top stratum forestimating allowable uplift z equals the in situ thicknesses of all strata above the base of the leas t t 

### pervious stratum plus the transformed thicknesses of the underlying more pervious top strata. This means that z will equal z only when the least pervious stratum is at the ground surface. Several examples of this b t 

### transformationare given in Figure B-2. In making the final determination of the effective thicknesses and p ermeabilities of t

he top stratum, the characteristics of the top stratum at least 61 to 91.4 m (200 to 300 ft) l andward of the levee must be considered. In addition, certain averaging assumptions are almost always re quired where soil conditions are reasonably similar. Thin or critical areas should be given considerabl e weight in arriving at such averages.

c. Thickness d and permeability k of pervious substratum . The thickness of the pervious substratum f 

### is defined as the thickness of the principal seepage-carrying stratum below the top stratum and above rock or other impervious base stratum. It is usually determined by means of deep borings although a combination o f shallow borings and sei smic or electrical resistivity surveys may also be employed. The thickness of any i nd ividual pervious strata within the principal seepage carrying stratum must be obtained by deep borings. The average hor izontal permeability k of the pervious substratum can be determined by means of a fiel d f 

### p ump test on a fully penetrating well or by the us e of correlations as shown in Figure 3-5(b) in the main text. Fora reas where such correlations exist their use will usually result in a more accurate permeability deter mination

than that from laboratory permeability tests. In addition to the methods above, if the total a mount of seepa

ge per unit length passing beneath the levee (Q ), the hydraulic grade line beneath the levee s 

### (M) and the thickness of pervious stratum (d) are known, k can be estimated from f (B-2)


### d. Di stance from riverside levee toe to river, L . This distance can usually be estimated fro m 1 

### topographic and stratigraphic maps. e. Base width of levee and berm, L . L can be determined from anticipated dimensions of new levees 2 2 

### or by measurement in the case of existing levees. f. Length o

f top stratum landward of levee toe, L . This distance can usually be determined fro m 3 

### b orings, topographic maps, and/or field reconnaissance. In determining this distance careful considerationCASE ACTUAL STRATA TRANSFORMED STRATA FOR COMPUTATION OF SEEPAGE 1c;,(CM) AND SUBSTRATUM PRESSURE SEC 

## t

1/2 c....._**~ g~**  :z, 1 =1.52m (5')CLAY lx1o-• 

## C\ie 

# -4------**~** :Z,:r=__1_22m (4') SANDY SILT**-~---** 

### 4 :z, 3 J.15m

## ~ SILTY SAND 1/10 :z,, =.15m (.5') ,SILTY SAND 

### • t / 

# , 1/10

1/2

1

GS
1/2

1/10

Figure B-2. Transformation of top strata 

## t TRANSFORMED STRATA FOR COMPUTATION OF MAXIMUM ALLOWABLE UPLIFT

c....._**~ g~** **~** =1.52m(5') CLAY ·m 

# I C\l'-'"
- - - - - - -**~ ~**  =1,22m(4') SANDY SILT

-- 

### --......---- 4**~ ~**  Z:! =.15m(.5') SILTY SAND



### f z,.

# =1~52m(5') SILTY SAND 

# gc- -;------ -.;:j<CXl ( ')**~.::::;_ ~**  =2t4m B SANDY SILT 

# r -I------ Z:! =1 j52m(5') CLAY 

# t t S::;;'**~** =2.44m(B') SANDY SILT 

# ....... . !

..--<C'J

### ~-=- 

# ------- 

# r**~** =1.52m(5') CLAY

# -·--~-- Z:! J.15m(.5') SILTY SAND wm 03: )>_. "0

... 

# .. ... No 0• 

### oN o.!.. CD 

# ... wx 3 ' 1 c ' k

f z bl d k bl

c ' k bl k f z bl d

x 3 ' 1 c tanh ( cL 3 )

x 3 ' tanh ( cL 3 )

c

x 3 ' ( 0

. 1 d ) x 3 N EM 1110-2-1913 30 Apr 2000

B-7 

### mustbe give n to any geological feature that may affect the seepage analysis. Of special importance are deposits of impe

rvious materials such as clay plugs which can serve as seepage barriers and if located near the landside toe could force the emergence of seepage at their near edge, thus having a pronounced effect on the seepage analysis.
g. Distance from landside levee toe to effective seepage exit, x . The effective seepage exit (point B, 3 

### Figure B-1) is defined as that point where a hypothetical open drainage face would result in the same hydrostat ic pressure at the landside levee toe and would cause the same amount of seepage to pass beneath thelevee as would occur for actual conditions. This point is also defined as the point where the hydraulic gradeline beneath the levee projected landward with a slope M intersects the groundwater or tailwater. If the length of foundation and top stratum beyond the landside levee toe L is known, x can be estimated from 3 3 

### the following equations: (1) For L = 4

3 (B-3)


### where
(B-3A) 

### (2) For L = finite distance to a seepage block

3 (B-4) 

### (3) For L = finite distance to an open seepage exit

3 (B-5) 

### (4) T he relation ship between z and x where L is infinite in landward extent has been computed from bl 3 3 

### equati on B-3 and plotted in Figure B-3 for various values of k /k and assuming d = 100 m or 100 ft. The f bl 

### x value corresponding to values of d other than 100 m or 100 ft can be computed from equation B-6 below: 3 (B-6) 

### where

x N is the value of x for d = 100 m or 100 ft 3 3EM 1110-2-1913 30 Apr 2000

to.ooo

.:::: 0**~** 0 E 0 0 

## - I 

### " <:<: 0 u. £ .to: <:<: 0 E**~** I 1- (.J z w --' 1- 

### x w w > 

## 6 w u. u. w sooo AOOO

3000

2000

1000

500
.coo

roo I FOR La • oo X3= I VALUES OF x 1 SHOWN ARE FOR d .100 FOR VALUES OF •'d" OrnER rnAN d=l00 x, • 0 • 1 

## -fd xu• • 1oo1.

3 .( 5 10 20 EFFECTIVE THICKNESS OF TOP STRATUM IN m OR ft (zb,)
Figure B-3. Effective seepage exit length for L 3 = oo and d =100m or ft 30



### k Example: Using Figure B-3, find x 3 

### for soil with 

### ....L = 200,

### ~~ = 3.05 m (10ft), and d = 45.7 m (150ft) kbl 

### k Solution: 1 -From Figure B-3 the value x 3 

### for 

### ....L = 200, zb 1 

### = 3.05 m (I 

### 0 ft). Then for zbL 

### = 3.05 m and d = kbl 

### 100m, x/ =246m; or zbL 

### = 10ft and d = 100ft, x/ =450ft

B-8x 3 ' 0

. 1 45

. 7 x 3 N

x 3 ' ( 0

. 1 ) ( 6

. 76 ) ( 246 ) ' 167 m

x 3 ' 0

. 1 d ( 450 ) ' 0

. 1 150 ( 450 ) ' 551 ft

x 1 ' tanh cL 1

c

x 1 ' 1 c tanh cL 1

i c ' ã r ã w ' G S & 1 1 % e EM 1110-2-1913 30 Apr 2000

B-9 

### 2 - Apply Equation B-6 to determine x for d = 45.7 m (150 ft) 3



### or
(5) If L is a finite

distance either to a seepage block or an open seepage exit, the effective exit length x 3 3 

### canbe computed by using equation B-4 or B-5 or by multiplying x (for L = 4 ) by a factor obtained from 3 3 

### Figure B-4. h. Distance from effective source seepage entry to riverside levee toe, x . The effective source o f 1 

### seepage e ntry into the pervious substratum (point A in Figure B-1) is defined as that line riverward of th e le vee where a hypothetical open seepage entry face fully penetrating the pervious substratum and with an impervious top stratum between this line and t he levee would produce the same flow and hydrostatic pressure beneath and landward of the levee as will occur for the actual conditions riverward of the levee. It is als o defined as that line or point where the hydraulic grade line beneath the levee projected riverward with a slope M intersects the river stage. (1) If the dis tance to the river from the riverside levee toe L is known and no riverside borrow pits o r l 

### seepage blocks exist, x can be estimated from the following equation: 1 (B-7) 

### (2) If a seepage block (usually a wide, thick deposit of clay) exists between the riverside levee toe and the river so as to prevent any seepage entrance into the pervious foundation beyond that point, x can be estimated 1 

### from the following equation:
(B-8)



### where L equals distance from riverside levee toe to seepage block and c is from equation B-3A.

1 

### i. Critical gradient for landside top stratum, i . The critical gradient is defined as the gradient required c 

### to cause boils or hea

ving (flotation) of the landside top stratum and is taken as the ratio of the submerged or buoyant unit weight of soil ã r comprising the top stratum and the unit weight of water ã or w (B-9)EM 1110-2-1913 30 Apr 2000**~** 

### ... w 8 !: 

### • 

# .. z 

### ...



### ... "' 

### "'**~** 0 

### ...**~** ><
.... 

### "


# ..

... ... w 1- z



### ... a: 0 

## ...


## ... >< 

# .. z

.... :::0 L**~** u 

### "' 0 

### ... a: 0

.... u < 

### ... 4.0

s.o

2.0 FOR BLOCKED EXITS WHERE rl FOR L 1 • 00 > 4 • I r 1 FOR fiNITE L 1 G r 1**fO~** L 1 •"' lHE ·FACTOR, r 1 fOR Ll • " I VALUES OF r 1 FOR L 1 • " CAN BE OBTAINED FROM FIG. B-3

0.3 0.5
RATIO s 

## •

Figure B-4. Ratio between x 3 for blocked or open exits and x 3 for L 3 

### = ""

where G 5 

### = specific gravity of soil solids

e = void ratio to

j. Slope of hydraulic grade line beneath levee, M. The slope of the hydraulic grade line in the pervious substratum beneath a levee can best be determined from readings of piezometers located beneath the levee where the seepage flow lines are essentially horizontal and the equipotential lines vertical. If such readings during high water are available, M can be determined from the following relation: B-10M ' Ä h R

M ' H x 1 % L2 % x 3

Q s ' S / k f H



### Q s 

### ' Mk

f 

### d EM 1110-2-1913 30 Apr 2000

B-11 (B-10a)


### where Ä h = the difference in piezometer readings R = the horizontal distance between piezometers This relationship is not valid, however, until artesian flow conditions have developed beneath the levee. If no piezometer readings are available, as in the case for new levee design, M must be determined by exit points and first establishing the effective seepage entrance and then connecting these points with a straight line, the slope of which is M. For new levees M is expressed as
(B-10b) 

### B-5. Computation of Seepage Flow and Substratum Hydrostatic Pressures

a. General (1) Seepage. For a levee underlain by a pervious foundation, the natural seepage per unit length of levee, Q , can be expressed by the general equation B-11. S (B-11) 

### where S / = shape factor This equation is valid provided the assumpt ions upon which Darcy's law is based are met. The mathematical expressions for the shape factor S / (subsequently given in this appendix) depend upon the dimensions of the generalized cross section of the levee and foundation, the characteristics of the top stratum both riverward and landwardof the levee, and the pervious substratum. Where the hydraulic grade line M is known fro m piezometer readings, the quantity of underseepage per unit length of the levee can be determined from equation B-12 as (B-12) 

### (2) Excess hydrostatic head beneath the landside top stratum. (a) The excess hydrostatic head h beneath the top stratum at the landside levee toe is related to the net o 

### headon the levee, the dimensions of the levee and foundation, permeability of the foundation, and th e character of the top stratum both riverward and landward of the levee. The head h can be expressed as a o 

### function of the net head H and the geometry of the piezometric line as subsequently shown. (b) The hea d h beneath the top stratum at a distance x landward from the landside levee toe can b e x 

### expressed as a function of the net head H and the distance x although it is more conveniently related to the hea d h at the levee toe. When h is expressed in terms of h it depends only upon the type and thickness of o x oS

/ ' d L2 % 0

. 86 d

S / ' d L 1 % L2 % L 3

h o ' H L 3

L 1 % L2 % L 3

h x ' h o L 3 & x

L 3 for x # L 3
h x ' 0 for x $ L 3 EM 1110-2-1913 30 Apr 2000

B-12 

### the top stratum and pervious foundation landward of the levee; the ratio h /h is thus independent of riverward x o 

### conditions. (c) Expressions for S

/ , h , and h are discussed in the following paragraphs. o x 

### b. Various underseepage flow and top substratum conditions. Case 1 - No Top Stratum . Where a levee is founded directly on pervious materials and no top stratum exists either riverward or la

ndward of the levee (Figure B-5a), the seepage Q can be obtained from equation B-11 S 

### in which
(B-13)


### The e xcess hydrostatic head landward of the levee is zero and h = h = 0. The severity of such a condition o x 

### in nature is governed by the exit gradient and seepage velocity that develop at the landside levee toe which can be estimated from a flow net compatible with the value of S / computed from Equation B-13. The maximum allowable exit gradient should be 0.5. Case 2 - Impervious Top Stratum Both Riverside and Land side . This case is found in nature where the levee is founded on thick (z > 4.58 m (15 ft)) deposits of clay or silts with clay strata. For such a condition little bl 

### or no seepage can occur through the landside top stratum.

a . If the pervious substratum is blocked landward of the levee, no seepage occurs beneath the levee and Q = 0. The head beneath the levee and the landside top stratum is equal to the net head at all points so that s 

### H = h = h

. o x 

### b . If the top stratum is impervious between the levee and river a nd has a length L , and if an open seepage 1 

### exit exists in the impervious top stratum at some distance L from the landside toe (i.e., L is not infinite as 3 3 

### shown in Figure B-5b), the distance from the landside toe of the levee to the effective seepage entry (river, borrow pit, etc.) is S = L + L and 1 2 (B-14)


### The heads h and h can be computed from

o x (B-15)

(B-16)S

/ ' d L 1 % L2 % 0

. 43 d

S / ' d 0

. 43 d % L2 % L 3

h o ' H L 3

0

. 43 d % L2 % L 3

h x ' h o L 3 & x

L 3

S / ' d x 1 % L2 % 0

. 43 d

S / ' d 0

. 43 d % L2 % x 3

h o ' H x 3

0

. 43 d % L2 % x 3 EM 1110-2-1913 30 Apr 2000

B-13 

### Case 3 - Impervious Riverside Top Stratum and No Landside Top Stratum . This condition may occur naturally or where extensive lands ide borrowing has taken place resulting in removal of all impervious material landward of the levee for a conside rable distance. Seepage can be computed utilizing Equation B-11 and the following shape factor
(B-17) 

### The excess head at the top of the sand landward of the levee is zero and the danger from piping must be evaluated from the upward gradient obtained from a flow net. This case is shown in Figure B-5c. Case 4 - Impervious Landside Top Stratum and No Riverside Top Stratum . This is a more common case than Case 3, occurring when extensive riverside borrowing has resulted in removal of the riverside impervious top stratum (Figure B-5d). For this condition the seepage is computed from Equation B-11 utilizing the shape factor given in Equation B-18 below; the heads h and h can be computed from Equations B-19 and B-20, o x 

### respectively.
(B-18)

(B-19)

(B-20)


### Case 5 - Semipervious Riverside Top Stratum and No Landside Top Stratum . The same equation for the shape factor as was used in Case 3 can be applied to this condition provided x is substituted for L as follows: 1 1 (B-21) 

### Since no landside top stratum exists, h = h = 0. This case is illustrated in Figure B-6a. o x 

### Case6 - Semipervious Landside Top Stratum and No Riverside Top Stratum . The same equations for the sha pe factor and heads beneath the landside top stratum that are used for Case 4 are applicable to this case provided x is substituted for L (Figure B-6b). These equations are as follows:

3 3 (B-22)

(B-23)EM 1110-2-1913 30 Apr 2000**~·** CASE 1 - No top stratum**~·** CASE 2 - Impervious topstrat\Jll both riverside and: lands.fde



### J = 

### A L 2 + 0.86d h .::; h**~** 0

0 X

.£.· CASE 3 - Impervious riverside top: stratunt & no landstde- top stratum d. CASE 4.

-**Imperv~us** landsfde-**t~** s**tr~tum** &**n~** rfversJde: tap stratt.R:



### $ d**~** 

### L 1**~** 

### L 

### 2 + 

### o.43d h = h

.. 0

0 . X

BASIC OEFIHITIONS ANU EQUATIONS HEAO.BENEATH TOP STRATUM AT LANDSIDE LEVEE TOE .•. HEAD BENEATH TOP STRATUM AT DISTANCE x FROH UUIDSIDE LEVEE TOE SHAPE· FACTOR FOR USE 

### m SEEPAGE EQUATION SEEPAGE PER UNIT. LENGTH OF LEVEE

.... Q • s

Figure B-5. Equations for computation of underseepage flow and substratum pressures for cases 1 through 4

B-14**~·** 

### CASE 5 - Semipervious riverside top stratum and no landside top stratum EM 1110-2-1913 30 Apr 2000

H
---- I! •**d~·.** 

### '..**~** 

### • :' • .. , : '• •**~** 

### : •' '•• ' :- :• :**~** 

### • 

### $ • xl + [2 + 

### o.43d h • h • 0

0 X d**~** •• •• t ,. ••• .... •• •• • • •• • ,_......**~·** 

### CASE 6 - Semipervious landside top stratum and no riverside top stratum

Figure B-6. Equations for computation of underseepage flow and substratum pressures for cases 5 and 6

(B-24)

Case 7- Semipervious Top Strata Both Riverside and Landside. Where both the riverside and 1andside top strata exist and are semipervious (Figure B-7), the quantity ofunderseepage can be computed from equation B-11 where Sis defined in Equation B-25. d 9=----

The head beneath the top stratum at the 1andside toe of the levee is expressed by (B-25)

(B-26)

The equations above are valid for all conditions where the landside top stratum is semipervious. However, the head**~** beneath the semipervious top stratum depends not only on the head h 0 but also on conditions landward of the levee. Expressions are given below for typical conditions encountered landward oflevees.

B-15EM 1110-2-1913 30 Apr 2000

a. L3 

## = oo

# ~~'! ,,

# '~**~-h.;"l~ :~''''k'.**  [),,,, :·· ''}--·

. . ' '

. . . b

. .. (X) ' ·, '**~** '

.... ., ' ) ' 

### . . ' ' ' :: ··, x, 

## =-!-
hx =ho e-cr

x, c tanh(cL, )

cos h c(L 3**~x)** h.= ho cosh cL 3
h. (for x=L, )= coshh cL
b. L3 is finite to a seepage block

X, L 2 L 3 tan h(cL ) X = 3

3 c h =h sinh c(L 3**~x)**

• o sin h cL 3 h, (for x=L 3 )=0

c. L 3 is finite to an open seepage exit
BASIC DEFINITIONS AND EQUATIONS 

### $kH = 1 

### x+L+x I 2 3 SEEPAGE PER UNIT LENGTH OF LEVEE........................................ 

## Q, = 

### Hx 3 HEAD BENEATH TOP STRATUM AT LANDSIDE LEVEE TOE............ 

### h 

### = __ ___::. __ 0 XI + 

### L + X 2 3

Figure B-7. Equations for computation of underseepage and substratum pressures for Case 7

B-16 3h x ' h o e & cx

h x ' h o cosh c (L 3 & x )

cosh cL 3

h x ( at x ' L 3 ) ' h o

cosh cL 3

h x ' h o sinh c (L 3 & x )

sinh cL 3

h x ( at x ' L 3 ) ' 0

c ' k bl k f z bl d , h o ' H x 3

x 1 % L2 % x 3 EM 1110-2-1913 30 Apr 2000

B-17 

### (1) For L = 4

3 (B-27) 

### where e = 2.718 (2) For L = a finite distance to a seepage block

3 (B-28)


### and
(B-29) 

### (3) For L = a finite distance to an open seepage exit

3 (B-30)


### and (B-31) 

### (4) Values of c and h in Equations B-27 through B-30 are as follows: o (B-32) 

### (5) In order to simplify the determination of h for various values of x, the relationship between h /h and x x o 

### x/x is plotted in Figu

re B-8 for L = 4 and for various values of x /L for both a seepage block and an open 3 3 3 3 

### seepage exit. The procedure for determining h using Figure B-8 can be summarized as follows: x


### a . Determine x , L , x and the head h at the landside toe of the levee. 1 2 3 o 

### b . For t he given distance x where h needs to be determined find the ratios x/x and x /L , then enter the x 3 3 3 

### appropriate graph in Figure B-8 to read the corresponding value of h /h

. x o


### c . Knowing the ratio h /h and the value of h compute h

. x o o x 

### (6) Values of h and h resulting from the equations above are actually hydrostatic heads at the middle o x 

### of the pe rvious substratum; where the ratio k /k is less than 100 to 500, values of h and h immediately f b o xEM 1110-2-1913 30 Apr 2000
beneath the top stratum will be slightly less than those computed because of the head loss resulting from upward seepage through the sand stratum.

1(1 0 J:..S::.

0

## ~

RATIO .21.. 1<:3 Figure B-8. Ratio between head landward of levee and head at landside toe of levee for levees founded on semipervious top stratum underlain by a pervious substratum

B-18EM 1110-2-1913 30 Apr 2000

C-1 

### Appendix C Design of Seepage Berms C-1. General This appendix presents design factors, equations, criteria, and exam ples of designing landside seepage berms. A discussion of the four major types of landside seepage berms is presented in the main text of this manual. The design equations presented are taken from U.S. Army Engineer Waterways Experiment Statio n TM 3-424 and EM 1110-2-1901 (Appendix A). Design procedures are taken from TM 3-424 and fro m procedures developed by the Lower Mississippi Valley Division (Appendix A). C-2. Design Factors

a . Se epage records, if available, should be studied to determine the severity of the underseepag e conditions dur ing high water. A projection based upon these records of underseepage during high water to the design flood should be made based on experience and judgment. Aerial photographs and borings should beused to evaluate geologic and soil conditions. The location of drainage ditches and borrow pits should be noted and considered in design. Additional borings should be made where required to determine in situ soil and geological data needed for design. b . The distance s from the l andside toe of the levee to the point of effective seepage entry is equal to the base width of the levee L plus the effective length of blanket x on the riverside of the levee. The effective 2 1 

### length of blanket x can be determined by using blanket equations presented in Appendix B. The effect of 1 

### riverside borro w pits or natural low areas such as oxbows, must be considered in determining x . Th e 1 

### effective length of blanket x should be the lesser of the distance based on the blanket thickness outside the 1 

### riverside borrow pit and the distance based on the blanket thickness inside the riverside borrow pit plus the dista nce from the riverside toe of the levee to the borrow pit. The blanket equations assume an infinite blanket length. However, this assumption ma y not be valid if the river is close to the levee. If the computed valueof x is greater than L (distance from riverside toe of levee to the river), then x should equal L

. 1 1 1 1 

### Distances to effective sources of seepage, effective lengths of riverside blankets, and vertical permeabilities of riverside blanket materials at different sites along the Mississippi River at the crest of the 1950 high water period are given in Table C-1. The values of x are observed values adjusted to an assumed condition of a 1 

### riversideblanket of infinite length with the same thickness as that of the borrow pit. The adjustment was made by use of blanket equations presented in Appendix B to partially eliminate the effect of different top strata riverward of the borrow pits and different distances between the levee and river at various sites.

c . The thickness d and permeability k of the pervious materials between the bottom of the blanket and f 

### the entrenched valley must be determined before designing a seepage berm. In Appendix B, paragraph B-4c, methods are described for determining d and k

. f 

### d

. The permeability k and effective thickness z of the landside blanket must be determined before the bl bl 

### seepage exit length x can be computed. If the blanket is composed of more than one stratum and the vertical 3 

### permeability of each stratum is known, the thickness of each stratum of the blanket can be transformed into an equivalent thickness of material having the same permeability as for one of the strata. A procedure and example for transforming the actual thickness of a stratified blanket into an effective thickness z with a bl 

### uniform vertical per meability is described in Appendix B, paragraph B-4b(2). The critical thickness of the landsidetop stratum z that should be used to determine if uplift pressure is within safe limits may or may t 

### not be equal to z for stratified layers. The procedur e and examples for computing z for different conditions bl t 

### of soil stratification are also presented in Appendix B, paragraph B-4b(2).EM 1110-2-1913 30 Apr 2000

C-2Table C-1aSummary of Distances to Effective Source of Seepage, Effective Lengths of Riverside Blankets, and Vertical Permeability of Riverside Blanket Materials at the Crest of1950 High Water (Metric Units)Blanket in Riverside Number ofBorrow PitPiezometer Lines SuggestedThickness from Which Data S, mxmkx 10 cm/secDesign Values1 bra -4Soil Type in m Were Obtained Max Min Avg Max Min Avg Max Min Avg kx , mbr 1Sand -- 3 304.8 243.8 292.6 146.3 61 112.8 – – – – 76.2Silty sand <1.52 3 243.8 170.7 204.2 97.5 70.1 85.3 14.2 1.6 7.0 7.0 91.4b1.52 to 3.05 1 170.7 170.7 170.7 85.3 85.3 85.3 1.8 1.8 1.82.5 182.95.7cSilt and sandy <1.52 4 457.2 182.9 320 371.8 83.3 204.2 7.4 0.24 2.2 2.0 121.9silt 1.52 to 3.05 2 487.7 277.4 384 362.7 155.4 259.1 5.0 0.33 2.71.5 243.8365.8>3.052.4 1.0cClay <1.52 6 390.1 185.9 310.9 228.6 33.6 210.3 1.7 0.34 0.79 0.8 182.91.52 to 3.04 2 524.3 463.3 493.8 387.1 326.1 356.6 1.3 0.86 1.08 0.5 396.2d d d3.05 to 4.58 2 – – – – – – – – – 0.2 762.0>4.58 3 960.1 243.8 487.74 4 40.0 0.00 0.000.05 1219.2e0.4 or Lc,f1Values of x computed from observed values of x and adjusted to a condition where L =4.a1 1 1Does not include Hole-in-the-Wall where values of S and xmay not be reliable because artesian flow conditions did not develop until near the crest of the 1950 high water.b1Averages of all values of k for a given soil type without regard to thickness.cbrValues are considered to be too high as at these piezometer lines (Upper Francis) seepage could enter the pervious substratum through a silty blanket riverward of the borrow pitdas well as through the clay in the borrow pit.Use the smaller of the two values.eAverage does not include k for blanket thickness between 1.52 and 3.05 m.fbrEM 1110-2-1913 30 Apr 2000

C-3Table C-1bSummary of Distances to Effective Source of Seepage, Effective Lengths of Riverside Blankets, and Vertical Permeability of Riverside Blanket Materials at the Crest of1950 High Water (English Units)Blanket in RiversideBorrow PitNumer of PiezometerThickness Lines from Which Data S, ftxftkx 10 cm/secSuggested Design Values1 bra -4Soil Type in ft Were Obtained Max Min Avg Max Min Avg Max Min Avg k x (ft)br 1Sand -- 3 1080 800 960 480 200 370 -- -- -- -- 250Silty sand <5 3 800 560 670 320 230 280 14.2 1.6 7.0 7.0 300b5 to 10 1 560 560 560 280 280 280 1.8 1.8 1.82.5 6005.7cSilt and sandy <5 4 1500 600 1050 1220 270 670 7.4 0.24 2.2 2.0 400silt 5 to 10 2 1600 910 1260 1190 510 850 5.0 0.33 2.71.5 8001200>102.4 1.0cClay <5 6 1280 610 1020 750 110 690 1.7 0.34 0.79 0.8 6005 to 10 2 1720 1520 1620 1270 1070 1170 1.3 0.86 1.08 0.5 1300d10 to 15 0 -- -- -- -- -- -- -- -- -- 0.2 2500>15 3 3150 800 16004440.0 0.00 0.000.05 4000 or L1e0.4c,fValues of x computed from observed values of x and adjusted to a condition where L =4.a1 1 1Does not include Hole-in-the-Wall where values of S and xmay not be reliable because artesian flow conditions did not develop until near the crest of the 1950 high water.b1Averages of all values of k for a given soil type without regard to thickness.cbrValues are considered to be too high as at these piezometer lines (Upper Francis) seepage could enter the pervious substratum through a silty blanket riverward of the borrow pitdas well as through the clay in the borrow pit.Use the smaller of the two values.eAverage does not include k for blanket thickness between 5 and 10 ft.fbrEM 1110-2-1913 30 Apr 2000



### e. The seepage exit length x 3 

### can be calculated from equations presented in Appendix B, paragraph B-4g. These equations are applicable to conditions where the length of the landside blanket L 3 

### is either infinite or finite. C-3. Design Equations and Criteria

a. Design equations. Equations for the design oflandside seepage berms for the four major berm types are presented in Figure C-1. These equations are valid when a lands ide blanket of infinite length exists. A discussion of the four major landside seepage berms is presented in paragraph 5-4.**y~** 

### •**:~~:;':!r:~** 

### vd,bt

Yi •**~~::!cl** unit vd,ht
Tv • un..lt**vei~tht** ot ...-..ter B • tot&l Df:t. bf:a.d on leTt:t:

h' • H**(~x**

## '::--:• ':---,--)
_o •+x 3 +x

### ·~- 't

### (~) t - y' 1 +**~v** USET!_2.,8 PERVIOUS SUBSTRATUM

b • bc&.d &l land.dde t.o. Of lt"YCe 0 Kx vithoul kr1l • ....::1..- • +X) h'

- bc&.d &t. l&.ndslde t.oe or lnce vltb 0

...... 1 0 •**~!:"';:!e ~~:ep-L41~t**  &t 1&:)4- 11 •**:~:'"r!,h** upvu-d 'radlcat &t t..oe

vhere:

A • 6 + Jsd r • 1)
r • 1 0 /1 1**h~** 

## • "• [1 • or**·(~)(ex** 

### )']

b' - l l. 0 0 t t•--- 1 + 10 h • a..Uovable hc-.4 &t toe

.. or bent • 1 1 · &t X • requirN bc-r. vldth t • required thlcbu:u of bcr-. a.t toe of lu·cc kt •**~=~lca..l** per-.u.b111ty of
r • ra.ct.or or aa.tcty &.«;&lnat uplift at**t~** or leTcc

X • l (X + 2:X: ) I ) p IP

Figure C-1. Design of landside seepage berms on impervious top stratum



### b. Design criteria**~** • flov into kra per foot of levee 1 • diatancc fro- la.Nhlde toe or levee to crre-ctlvc**aaur~c** or &ecpe..&e entry

x 3 •**:~·~::~: ~(~:::~;~•**  toe source of seepe.c:e exit. d

- etreett.ve tbt.ck.ne•• or perr1ou• •ub•t.rat.UII.

Perrloul Bera vi t.h Collector



### ( 1) Where a levee overlies a top stratum creating a landside blanket and the upward gradient through the blanket at the landside toe of the levee is greater than 0.8, a seepage berm should be designed with an allowable upward gradient of 0.3 through the blanket and berm at the landside toe of the levee. For a C-4h o N ' H ( X % 0

. 43 D )
x 1 % L2 % X % 0

. 43 D 

### d kh 

### /kv

Q s ' k f Hd
x 1 % L2 % X % 0

. 43 D EM 1110-2-1913 30 Apr 2000

C-5 

### saturated unit soil weight of 1840 kg/m (115 pcf), this is equivalent to a factor of safety of 2.8. The factor 3 

### of safety of 2.8 applies only to new construction, not to existing projects. A factor of safety lower than 2.8 may be used, based on sufficient soil data and past performance in the area. The berm width should be based on an allowable upward gradient of 0.8 through the top stratum at the landside toe of the berm, subject to thelimitations in the paragraphs which follow. The thickness of the berm should be increased 25 percent to all ow for shrinkage, foundation settlements and variations in design factors. Where field observation s during lesser floods indica

te severe seepage problems would occur at the design flood, the berm dimensions should be extended. ( 2) All berms should

have minimum thickness of 1.52 m (5 ft) at the levee toe, a minimum thickness of 0.61 m (2 ft) at the berm crown, and a minimum width of 45.7 m (150 ft). (3) For conditions where the computed upward gradient at the landside toe of the levee is between 0.5 and 0.8 without

a berm, a berm with minimum dimensions as specified in (2) above should be constructed. Also for conditions where the computed gradient is less than 0. 5, but either severe seepage has been observed orse epage is expected to become severe and soften the landside portion of the levee, the minimum ber m should be constructed. ( 4) The width of the berm is usually limited to about 91.4 to 12 1.9 m (300 to 400 ft), although the design calculations may indicate that a greater berm width is required. When the selected width of the berm is less tha n the calculated width, using berm design equations of Figure C-1, the head h N and berm thickness t at o 

### the leveetoe will be less than for the computed width. For the selected berm, h N should be recompute d o 

### assumingan i of 0.8 at the toe of the new berm and a linear piezometric grade line between the toe of the

1 

### newberm and the point of effective seepage entry. The design thickness of the selected berm at the toe of the levee and the estimated seepage flow under the levee will be based on the value of h N corresponding to o 

### the selected berm. (5) For conditions where no landside blanket exists, the necessity for a landside seepage berm will b e based on the exit gradient and seepage velocity as discussed in paragraph B-5b. The berm thickness at the lands ide toe should be of such magnitude that the upward gradient i does not exceed 0.3. The desig n o 

### thickness of the berm should be increased by 25 percent to allow for shrinkage, foundation settlements, and variations in design factors. The head h N beneath the berm at the landside toe of the levee can be determined o 

### from Equation C-1.
(C-1)



### In the above equation D

& is the transformed thickness of the pervious stratum which is equal to , L is the base width of the levee, H is the total net hea d on levee, X is the berm width, and x , is the effective 2 1 

### length of impervious blanket rive rside of the levee. If no riverside blanket exists, the value of x is assumed 1 

### to be 0.43 D

& . The rate of seepage Q below the levee per unit length of levee can be determined usin g s 

### Equation C-2.
(C-2)EM 1110-2-1913

30 Apr 2000

C-6 

### Inthe equation above, k is the permeability of the pervious substratum and d is the effective thickness of f 

### the pervio us substratum. H , x , L , X , and D & are as previously defined. If Q exceeds 757.1 R /mi n 1 2 s 

### (200 gal/min) pe r 30.5 m (100 ft) of levee, a riverside blanket should be designed to reduce the seepage

. Riverside blankets are discussed in paragraph 5-3. (6) The slope of berms should be generally 1V on 50H or steeper to ensure drainage. If the berm i s constructed after the levee has caused the foundation to consolidate fully, a slope of 1V on 75H can be used. Where wide, thick berms are required, consideration may be given to using a berm with a broken surfac e slope to more closely simulate the theoretical thickness and consequently reduce the cost of the berm. Where this is done, the steeper riverward slope of the berm should be no flatter than 1V on 75H and the landward slope of the berm should be no flatter than 1V on 100H. ( 7) In short reaches where computations indicate no berm is necessary, but berms are required in adjacent reaches, it may be advisable to cont inue the berm construction through such reaches due to concentration of seepagein these areas. Also, in areas where entrance conditions in adjacent reaches are highly variable , potential adverse effects of close entry in adjacent reaches should be taken in to consideration. C-4. Design Example Anexample design problem with solution is presented in Table C-2 illustrating the design of impervious , semipervious, sand, and free draining landside seepage berms overlaying a thin landside top stratum. Each berm is de signed for the same conditions using the design equations and design criteria as presented in this appendix.(") I

....... Table C-2a Examples of Design of Seepage Berms (Metric Units) Designs based on following conditions: H 7.6m z, 

### = 1.83 m 1,000 x 10· 4 em/sec 0.30

d 30.5 m 0.80 3 X 1 0- 4 em/SeC y' 840.5 kg/m 3

s 304.8 m 137.2 m

Suggested Design Dimensions Reguired Berm Thickness Berm Approximate Width Thicknessa h lb 0 at Berm Width Berm Thickness Type Berm X,m t, m m Crown m X,m Slope Levee Toe m Impervious 268.2 2.22 4.33 0.61 243.8 9 1 on 75 3.87 1.49 3.23 0.61 121.9 1 on 75 2.22 Semi pervious 85.34 1.16 2.62 0.61 83.82 1 on 75 1.74 Sand 79.20 1.0 2.53 0.61 76.20 1 on 75 1.61 Pervious with 65.53 0.88 2.35 0.61 60.96 1 on 75 1.43 collector

a At toe of levee. b Head at toe of levee with berm, measured above surface of natural ground. c Thickness increased 25 percent for shrinkage, foundation settlements, and variations in design factors. d Calculations based on suggested construction dimensions. y' y'

F 840.5 kg/m 3 for impervious berms 920.6 kg/m 3 for sand berm or pervious berm with collector, F 

### = 1.6 1.6 for impervious berm

Approximated Suggested Construction Dimensions Material Thicknessc Berm Thicknessc Required at Berm Width at Levee m 3 per 100m Crown m X,m Toem of Levee

0.76 243.8 4.85 73,266 0.76 121.9 2.77 23,312 0.76 83.82 2.16 13,321 0.76 76.20 2.01 11,528 0.76 60.96 1.80 8,454 1

e Berm width considered longer than necessary. If boils developed 121.9 m or farther landward of the toe of the levee, the levee probably would not be endangered. Therefore, an alternate design for an impervious berm with a width of 121.9 m is also given. ' Sand and gravel blankets and collector system are also required. m 

## s: (,) ...... 0 ......
...... l>o**~r\,** I 1\)
...... 0<0 0 ...... owEM 1110-2-1913

30 Apr 2000

C-8Table C-2bExamples of Design of Seepage Berms (English Units)Designs based on following conditions:H=25 ftz=z= 6.0 ftãN=52.5 pcf for impervious bermsbltk=1,000 × 10cm/seci=0.30ãN=57.5 pcf for sand berm or perviousfo-4berm with collector,F = 1.6d=100 fti=0.80F=1.6 for impervious berm1k=3 × 10cm/secãN=52.5 pcfL=4bl3-4s=1,000 ftx=450 ft3ApproximatedSuggested Design DimensionsSuggested Construction DimensionsMaterialRequired BermThicknessBermApproximateThicknessBermThicknessRequiredcWidthThicknesshNat BermWidthBermThicknessat BermWidthat Leveeydper 100 ftaboType BermX, ftt, ftftCrown ftX, ftSlopeLevee Toe ftCrown ftX, ftToe ftof LeveeImpervious8807.314.22.08001 on 7512.72.580015.928,600e4.910.62.04001 on 757.32.54009.19,100Semipervious2803.88.62.02751 on 755.72.52757.15,200Sand2603.38.32.02501 on 755.32.52506.64,500Pervious with2152.97.72.02001 on 754.72.52005.93,300fcollectorAt toe of levee.aHead at toe of levee with berm, measured above surface of natural ground.bThickness increased 25 percent for shrinkage, foundation settlements, and variations in design factors.cCalculations based on suggested construction dimensions.dBerm width considered longer than necessary. If boils developed 400 ft or farther landward of the toe of the levee, the levee probably would not be endangered. Therefore, anealternate design for an impervious berm with a width of 400 ft is also given.Sand and gravel blankets and collector system are also required.fEM 1110-2-1913 30 Apr 2000

In paragraphs D-2 and D-3 the criteria apply to drains and filters; for brevity, only the word filter will be used. 1 In practice, it is normal for a small amount of protected soil to move into the filter upon initiation of seepage. This action should quickly stop and 2 may not be observed when seepage first occurs. This is one reason that initial operation of embankment seepage control measures should be closely observed by qualified personnel.

3 Guide for Determining the Gradation of Sand and Gravel Filters, Soil Mechanics Note No. 1, U.S. Department of Agriculture Soil Conservatio n Services, Engineering Division, January 1986. D-1 

### Appendix D Filter Design D-1. General The objective of filters and drains used as seepage control measures for embankments is to efficiently control the movement of water within and about the embankment. In order to meet this objective, filters and drains must, for the project life and with minimum main tenance, retain the protected materials, allow relatively free movement of water, and have sufficient discharge capacity. For design, these three necessities are termed, respe ctively, piping or stability requirement, permeability requirement, and discharge capacity. Thi s appendix will explain how these requirements are met for cohesionless and cohesive materials, and provide general construction guidance for installation of filters and drains. The terms filters and drains are sometimes used interchangeably. Some definitions classify filters and drains by function. In this case, filters must retain the protected soils and have a permeability greater than the protected soil but do not need to have a particular flow or drainage capacity since flow will be perpendicular to the interface between the protected soil and filter. Drains, howeve r, while meeting the requirements of filters, must have an adequate discharge capacity sinc e drains collect seepage and conduct it to a discharge point or area. In practice, the critical element is not def inition, but recognition, by the designer, when a drain must collect and conduct water. In this case the drain must be properly designed for the expected flows. Where it is not possible to meet the criteria of this appendix, the design must be cautiously done and based on carefully controlled laboratory filter tests. D-2. Stability Filters and drains allow seepage to move out of a protected soil more quickly than the seepage moves within 1 

### the protected soil. Thus, the filter material must be more op en and have a larger grain size than the protected soil. Seepage f rom the finer soil to the filter can cause movement of the finer soil particles from th e protected soil into and through the filter. This movement will endanger the embankment. Destruction of 2 

### the protected s oil structure may occur due to the loss of material. Also, clogging of the filter may occur causing loss of the filter’s ability to remove wat er from the protected soil. Criteria developed by many years of experience are used to design filters a nd drains which will prevent the movement of protected soil into the filter. This criterion, called piping or stability criterion, is based on the grain-size relationship between the protected s oil and the filter. In the following, the small character “d” is used to represent the grain size for the protected (or base) material and the large character “D” the grain size for the filter material. Determine filter gradation limits using the following steps: 3 

### 1. Det ermine the gradation curve (grain-size distribution) of the base soil material. Use enough sample s to define the range of grain sizes for the base soil or soils and design the filter gradation based on the base soil that requires the smallest D size. 15EM 1110-2-1913

30 Apr 2000

D-2 

### 2. Proceed to step 4 if the base soils contains no gravel (materials larger than No. 4 sieve). 3. Prepare adjusted gradation curves for base soils with particles larger than the No. 4 (4.75 mm ) sieve.

a . Obtain a correction factor dividing 100 by the percent passing the No. 4 (4.75 mm) sieve. b

. Multiply the percentage passing each sieve size of the base soil smaller than No. 4 (4.75 mm) by the correction factor from step 3a.

c . Plot these adjusted percentages to obtain a new gradation curve. d

. Use the adjusted curve to determine the percent passing the No. 200 (0.075 mm) sieve in step 4. 4. P lace the base soil in a category based on the percent passing the No. 200 (0.075 mm) sieve in accordance with Table D-1.

Table D-1 Categories of Base Soil Materials Percent Finer Than the No. 200 Category (0.075 mm) Sieve 1 >85 2 40-85 3 15-39 4 <15



### 5. Determinethe maximum D size for the filter in accordance with Table D-2. Note that the maximum 15 

### D is not required to be smaller than 0.20 mm. 15 

### 6. To ensure efficient permeability, set the minimum D greater than or equal to 3 to 5 × maximum d of 15 15 

### the base soil before regrading but no less than 0.1 mm. 7. Set the maximum particle size at 75 mm (3 in.) and the maximum passing the No. 200 (0.075 mm) sieve at 5 perc ent. The portion of the filter material passing the No. 40 (0.425 mm) sieve must have a plasticity index (PI) of zero when tested in accordance with EM 1110-2-1906, “Laboratory Soils Testing.” 8. Designt he filter limits within the maximum and minimum values determined in steps 5, 6, and 7

. Standard gr adations may be used if desired. Plot the limit values, and connect all the minimum an d maximumpo ints with straight lines. To minimize segregation and related effects, filters should hav e relatively uniform grain-size distribution curves, without “gap-grading”—sharp breaks in curvature indicati ngabsence of certain particle sizes. This may require setting limits that reduce the broadness o f fil ters within the maximum and minimum values determined. Sand filters with D less than about 20 mm 90 

### generallydo not need limitations on filter broadness to prevent segregation. For coarser filters and gravel zones that serve both as filters and drains, the ratio D /D should decrease rapidly with increasing D size. 90 10 10 

### The limits in Table D-3 are suggested for preventing segregation during construction of these coarser filters.40

& A 40

& 15

15 percent size of filter material 15 percent of the protected soil $ 3 to 5 EM 1110-2-1913 30 Apr 2000

D-3 Table D-2 Criteria for Filters Base Soil Base Soil Description and Category Percent Finer Than the No. 200 (0.075 mm) Sieve (a) 1 Fine silts and clays; more than 85 percent finer (c) D # 9 × d 15 85 2 Sands, silts, clays and silty and clayey sands; 40 to 85 percent finer D # 0.7 mm 15 3 Silty and clayey sands and gravels; 15 to 39 percent finer (d), (e) D # 15 [(4 × d ) - 0.7 mm] + 0.7

85 mm 4 Sands and gravels; less than 15 percent finer (f) D # 4 to 5 × d 15 85 (a) Category designation for soil containing particles larger than 4.75 mm is determined from a gradation curve of the base soil which has been adjusted to 100 percent passing the No. 4 (4.75 mm) sieve. (b) Filters are to have a maximum particle size of 75 mm (3 in.) and a maximum of 5 percent passing the No. 200 (0.075 mm) sieve with the plasticity index (PI) of the fines equal to zero. PI is determined on the material passing the No. 40 (0.425 mm) sieve in accordance with EM 1110-2-1906, “Laboratory Soils Testing.” To ensure sufficient permeability, filters are to have a D size equal to or greater than 4 × d but no smaller than 0.1 mm. 15 15 (c) When 9 × d is less than 0.2 mm, use 0.2 mm. 85 (d) A = percent passing the No. 200 (0.075 mm) sieve after any regrading. (e) When 4 × d is less than 0.7 mm, use 0.7 mm. 85 (f) In category 4, the D # 4 × d criterion should be used in the case of filters beneath riprap subject to wave action and drains 15 85 which may be subject to violent surging and/or vibration.

Table D-3 D and D Limits for Preventing Segregation 10 90 Minimum D Maximum D

10 90 (mm) (mm) < 0.5 20 0.5 - 1.0 25 1.0 - 2.0 30 2.0 - 5.0 40 5.0 - 10 50 10 - 50 60


### D-3. Permeability Therequirement that seepage move more quickly through the filter than through the protected soil (called the permeability criterion) is again met by a grain-size relationship criterion based on experience: Permeability
(D-1)Minimum 50 percent size of filter material hole diameter or slot width $ 1

. 0 EM 1110-2-1913 30 Apr 2000

1Sherard, J. L., Dunnigan, L. P., “Fil ters and Leakage Control in Embankment Dams,” Proceeding of the Symposium on Seepage and Leakage from Dams and Impoundments , ASCE National Convention, Denver, Colorado, 1985.

2 EM 1110-2-23 00 states, “Collector pipe should not be placed within the embankment, except at the downstream toe, because of the danger of either breakage or separation of joints, resulting from fill placement and compaction operations, or settlement, which might result in either clogging and/or piping.” D-4 

### Permea bility of a granular soil is roughly proportional to the square of the 10- to 15-percent size material. Thus, the permeability criterion ensures that filter materials have approximately 9 to 25 or more times the permeability of the protected soil. Generally, a permeability ratio of at least 5 is preferred; however, in the case of a wide band of uniform base material gradations, a permeability ratio as low as 3 may be used with respect to the maximum 15-percent size of the base material. There may be situations, particularly where the filter is not part of a

drain, where the permeability of the filter is not important. In those situations, this criterion may be ignored. D-4. Applicability The previously given filter criteria in Table D-2 and Equation D-1 are applicable for all soils (cohesionless or cohesive soils) including dispersive soils. However, laboratory filter tests for dispersive soils, very fine 1 

### silt, and very fine cohesive soils with high plastic limits are recommended. D-5. Perforated Pipe 2 

### The following criteria are applicable for preventing infiltration of filter material into perforated pipe, screens, etc.: (D-2) 

### In many instances a filt

er material meeting the criteria given by Table D-2 and Equation D-1 relative to the material being drained is too fine to meet the criteria given by Equation D-2. In these instances, multilayered or “graded” filters are required. In a graded filter each layer meets the requirements given by Table D-2 and Equation D-1 with resp ect to the pervious layer with the final layer in which a collector pipe is bedded also meeting t he requirements given by Equation D-2. Graded filter systems may also be needed whe n transitioning from fine to coarse materials in a zoned embankment or where coarse material is required for improving the water-carrying capacity of the system. D-6. Gap-Graded Base The preceding criteri a cannot, in most instances, be applied directly to protect severely gap- or skip-graded soils. In a gap-graded soil such as that shown in Figure D-1. The coarse material simply floats in the matrix of fines. Consequently, the scattered coarse particles will not deter the migration of fines as they do in a well-graded material. For such gap-graded soils, the filter should be designed to protect the fine matri x rather than the total range of particle sizes. This is illustrated in Figure D-1. The 85-percent size of the total sample is 5.2 mm. Considering only the matrix material, the 85-percent size would be 0.1 mm resulting in a much finer filter material being required. This procedure may also be followed in some instances where the material being drained has a very wide ra nge of particle sizes (e.g., materials graded from coarse gravels to significant percentages of silt or clay). For major structures such a design should be checked with filter tests.. I U S. STANDARD SIEVE OPENING IH INCHES U S. STANDARD SIEVE NUMBERS 6 4 3**~** 

## ,,.. I f 

### t 3 4 6 I 10 1416 20 30 40 50 70 100 140 I 

### f'\:-t I II 

# ·' I I I 

### .....**~---** I**--1--~** 

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. 

# - . 

# - 80

### ~ 

# - .

. TOTAL MATERIAL· 

## v "70



# .. .. 

# -

.



# - - ·- 

# - ·-·- . 

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## - -·f- 

# -- - 30


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# - 

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# - 0. -I20 ,



## - - 

# -- - - ..
. . 0 1-'- 1- 

# -- .. 

# --- c 500 100 50 10 5 I 05 0.1 GAAIN SitE IN MllLIMttUS COBBLES SAND

Figure D-1. Analysis of a gap-graded material 20o



# -

. o, l'o**~ -~**  

## [; 

# -, -

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# I' 1-1-

### ~ 

# ·- 1\.



# . 

# '

0



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# - 1-**M~TRIX** MATERIAL

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## ..

1-r- 

# - -- 0.01 11.005 SILT OR aAT 10
I...

30

40

50

60



# ·-- 70

'90



# - 0.01

w-" o-"



## .... l>O '01

.. N I 

### ...., 

## .... OCD 0-> 

### owEM 1110-2-1913

30 Apr 2000

Sherard, J. L., “Sinkholes in Dams of Coarse, Broadly-Graded Soils,” Transactions of the 13th International Congress on Large Dams , New 1 Delhi, India, Vol. II, 1979, pp 25-35. D-6 

### D-7. Gap-Graded Filter Aga p-graded filter material must never be specified or allowed since it will consist of either the coars e particles floating in the finer material or the fine material having no stability within the voids produced by the coarse material. In the former case the material may not be permeable enough to provide adequate drainage. The latter case is particularly dangerous since piping of the protected material can easily occur through the relatively large, loosely filled voids provided by the coarse material. D-8. Broadly Graded Base One of the more common soils used for embankment dams is a broadly graded material with particle sizes ranging from clay sizes to coarse gravels and including all intermediate sizes. These soils may be of glacial, alluvial-colluvial, or weathered rock origin. As noted by Sherard (1979) , since the 85-percent size of the 1 

### soilis commonly on the order of 20 to 30 mm, a direct application of the stability criteria D /d # 4 to 5 15 85 

### wouldal low very coarse uniform gravel without sand sizes as a downstream filter, which would not b e satisfact ory. The typical broadly graded soils fall in Soil Category 2 in Table D-2 and require a sand o r gravelly filter with D # 0.7 mm. 15 

### D-9. Example of Graded Filter Design for Drain Seldom, i f ever, is a single gradation curve representative of a given material. A material is generall y represe nted

by a gradation band which encompasses all the individual gradation curves. Likewise, th e required gradation for

the filter material is also given as a band. The design of a graded filter which shows the application of the filter criteria where the gradations are represented by bands is illustrated in Figure D-2. A typical two-layer filter for protecting an impervious core of a dam is illustrated. The impervious core is a fat clay (CH) with a trace of sand which falls in Category 1 soil in Table D-2. The criterion D # 9 × d 15 85 

### is ap plied and a “point a” is established in Figure D-2. Filter material graded within a band such as that shown for Filter A in Figure D-2 is acceptable based on the stability criteria. The fine limit of the band was arbitrarily drawn, and in t

his example, is intended to represent the gradation of a readily available material. A check is then

made to ensure that the 15-percent size of the fine limit of the filter material band (point b) is equal to or greater than 3 to 5 times the 15-percent size of the coarse limit of the drained material band (pointc). Filter A has a minimum D size and a maximum D size such that, based on Table D-3 , 10 90 

### se gregationduring placement can be prevented. Filter A meets both the stability and permeability requirements and is a suitable filter material for protecting the impervious core material. The second filter, Filt er B, usually is needed to transition from a fine filter (Filter A) to coarse materials in a zone d embankment dam. Filter B must meet the criteria given by Table D-2 with respect to Filter A. For stability, the 15-percent size of the coarselimit of the gradation band for the second filter (point d) cannot be greater than 4 to 5 times the 85-percent size of the finelimit of the gradation bank for Filter A (point e). Fo r permeability, the 15-percent size of the finelimit (point f) must be at least 3 to 5 times greater than th e 15-percent size of the coarse limit for Filter

A (point a). With points d and f established, the fine and coarse limi ts for Filter B may be established by drawing curves through the points approximately parallel to th e respective limits for Filter A. A check is then made to see that the ratio of maximum D /minimum D size 90 10 

### Filter B is approximately in the range as indicated in Table D-3. A well-graded filter which usually would notmeet the requirements in Table D-3 may be used if segregation can be controlled during placement

. Figure D-2 is intended to show only the principles of filter design. The design of thickness of a filter for sufficient seepage discharge capacity is done by applying Darcy’s Law, Q = kia.

## ... 

# - .iJ.S. STA!IDARD SIEVE OPEHIHQ IH IHCHES · U.S. ITIJIDAIID SIEVE NUMBERS

tOO 11tStzt01 I 4.**~** 2**1~·** 1**·~ ~** **~** :1 4 I I tO t4tl 20 3D 40 ·sa ·70 tOO t40 200 I I I 

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## \..,('!**,~~** Q 

# ' ' 

# ' I'**b~3** to 5c"

too sa 10 I D.l 0.1 0.05 0.01 0.005 ORJJH SIZE IN MIWMETERI

Figure D-2. Illustration of the design of a graded filter 

# ' I'. D

1



# ' 70 

### '\. 

## C"\

100

.0.001

m 

# s: w-" o-" _. )>O "C' -. N I N-" 0<0 0-> 

### owEM 1110-2-1913

30 Apr 2000

D-8 

### D-10. Construction EM 1110-2- 1911 and EM 1110-2-2300 provide guidance for construction. Major concerns durin g construction include:

a . Prevention of contamination of drains and filters by runoff containing sediment, dust, constructio n traffic, and mixing with nearby fine-grained materials during placement and compaction. Drain and filter material may be kept at a

n elevation higher than the surrounding fine-grained materials during construction to prevent contamination by sediment-carrying runoff. b . Prevention of segregation, particularly well-graded filters, during handling and placement.

c . Proper in-place density is usually required to be no less than 80-percent relative density. Granular mater ials containing little or no fines should be saturated during compaction to prevent “bulking” (lo w density) which can result in settlement when overburden materials are placed and the drain is subsequently saturated by seepage flows. d . Gradation should be monitored closely so that designed filter criteria are met.

e . Thicknes s of layers should be monitored to ensure designed discharge capacity and continuity of the filter. Thus, qualit

y control/assurance is very important during filter construction because of the critical function of this relatively small part of the embankment. D-11. Monitoring Monitoring of seepage quantity and quality (see Chapter 13 of EM 1110-2-1901 for method of monitoring seepage) once the filter is functioning is very important to the safety of the embankment. An increase i n seepage flow may be due to a higher reservoir level or may be caused by cracking or piping. The source of the additional seepage should be determined and action taken as required (see Chapters 12, 13, and 14 of EM 1110-2-1901). Decreases in seepage flows may also signal dangers such as clogging of the drain(s) with piped material, iron oxide, calcareous material, and effects of remedial grouting. Again, the cause should be determined and appropriate remedial measures taken. Drain outlets should be kept free of sediment and vegetation. In cold climates, design or maintenance measures should be taken to prevent clogging of drain outlets by ice.k N f ' k h k v d N ' d k h /k v EM 1110-2-1913 30 Apr 2000

E-1 

### Appendix E Drainage Trench

E-1. General This appendix presents the design and analysis of drainage trenches. The design criteria and the example presented are taken from U.S. Army Engineer Waterways Experiment Station TM 3-424 (Appendix A). E-2. Applicability A

drainage trench can be used to control underseepage where the top stratum is thin and the perviou s f oundation is relatively shallow so that the trench substantially penetrates the aquifer. Where the pervious found ationis deep, a drainage trench of moderate depth would attract only a small portion of th e u nderseepage. The drainage trench method is known to be effective where the ratio of the thickness of the landside blanke t, z , to the depth of the pervious foundation, d, is greater than 25 percent. While only bl 

### substan tialpenetration by the drainage trench provides significant landside relief, a trench with limite d penetration may be used in conjunction with a landside blanket to contain seepage pressures. E-3. Design Criteria T he design criteria and graphs are applicable only for homogeneous, isotropic pervious foundations having a n impervious top stratum l andward of the drainage trench. The distance from the source of seepage to the l andside toe of the levee, S, to be used in the design may be estimated by a procedure outlined in Appendix B. Seepag e into a drainage trench, Q , and the maximum head landside of the levee, h , where the blanket st 4 

### l andside of the levee consistsof impervious or relatively impervious soil, can be computed using the graphs presented in Figure E-1. The analysis and design procedure is as follows:

a . Whe re k > k transform the in situ pervious stratum into a homogeneous, isotropic formation using h v 

### k N and d N for k and d, respectively, as follows:

f f (E-1) (E-2) 

### where d = thickness of the pervious foundation k = coefficient of horizontal permeability h 

### k = coefficient of vertical permeability v 

### k N = transformed coefficient of permeability of the foundation f 

### d N = transformed depth of the pervious foundation b . From the geometry of the drainage trench, Figure E-1, find the ratio of r /d, (Case I) or b /d (Case II) d d 

### where:

r = radius of the circular sector of the trench for Case I

b 

### b = width of the rectangular trench section for Case II dm I N 

### 2.4 2.2 r\. 

### 2.0 

# ' 1.8 

### '\ 1.6 

### '\ 1.4 "'\ 

# '**~** 

### 1.2 

## z <r: 0 "l?'U>

':c!>**~7**

!'-

0 fLa 

### a-: r-----------"s'-------t__::=----!.-UPLIFT BENEATH TOP STRATUM

SHAPE FACTOR S = S+ EL .:::__:_!A_+=

d d MAXIMUM NET UPLIFT RATIO UNDER TOP IMPERVIOUS BLANKET LANDSIDE OF DRAIN IN h 

### {{=S, A., 

## fJ/"d 1. 

### 0**~U>** 

# t.--**~** CASE I 

### 0.8 

# ' '**~** 

### 0.6 0.4 i'**~** 

### .....**~** 

## ... At**~Aa** """ 

# ' 0.2 0.0 -0.2 NOT : "lllll**~** '- CURVES SHOWN ARE BASED

## '~**~ON** THE RATIO s IJL 1'1 

### ..... <r>l 

# r - 

# ' I \ 

### -0.4 

### I

0.001 0.01 0.1 0.2 0.30.4 0.60.81.0

NOTE:**~I.!._** d ' d SHAPE FACTORS = EL 

### _s- + -.::::=

d d MAXIMUM NET UPLIFT RATIO UNDER TOP IMPERVIOUS BLANKET LANDSIDE OF DRAIN IN h 

### {{= 

### s. "· CASE II SEEPAGE PER UNIT LENGTH OF STRUCTURE IS A Q=k, HS

WHERE K" > K., TRANSFORM_ PERVIUS SUBSTRATUM TO A HOMOGENEOUS, ISOTROPIC FOUNDATION AND USE "K, FOR k, AND d FOR d IN ABOVE FORMAULAS. k, = 

### }k::k. AND d=dJF

Figure E-1. Formulas and design curves for drainage trenches (ref. EM 1110-2-1601) wm 

## os: )>_. "C _. 

## ... _. NO 0• 

### oN 

## o..:.. CD _. 

### wS

/ 1 ' d S % r d % EL 1
S / 2 ' d S % EL 2

Q st ' S / k N f H
h 4 ' H S / ë EM 1110-2-1913 30 Apr 2000

E-3 

### c . Use the computed ratio of r /d or b /d to enter the appropriate graph of Figure E-1 to determine the d d 

### c orresponding value of EL/d and ë . The factor EL is the extra length of pervious substratums corresponding t o the increased resistance to flow into a drainage trench as compared to a fully penetrated open trench, and ë is a n uplift factor. The values of EL /d and ë , are related to Case I, while EL /d and ë are related to 1 2 2 

### Case II. d

. Once the magnitude of EL is determined, the value of the shape factor S / which is equivalent to th e r atio in the flow net of the number of flow channels to the number of equipotential drops, can be determined as: Case I : (E-3) 

### Case II : (E-4)



### e . Calculate the quantity of discharge per unit length of the levee, Q , and the maximum head landside st 

### of the trench, h , using the following expressions:

4 (E-5) (E-6) 

### where H = total head acting on the levee, or the height of flood stage above the average low-ground surface or tail water Wherethere is no top stratum landside of the levee, seepage flow into the drainage trench and beyond can be estimated from the flow net analysis. E-4. Limitations of the Method The method of controlling underseepage using the trench drain method has several limitations:

a . If the top stratum landside of the drainage trench has a certain degree of perviousness, seepage into thetrench and the maximum head landward of the levee will be somewhat less than those computed from F igure E-1. Therefore, design based on Figure E-1 will be sligh tly on the conservative side if the top stratum landside of the drain trench is semipervious. b . If the pervious founda

tion is highly stratified, seepage may bypass the drain and emerge landward of the drain thereby defeating its purpose. For such cas es, other methods of seepage control are more effective.

c . If the trench is underlain by either impervious or semipervious strata of either clay, silt, or fine sand, the formulas presented in Part E-3 are no longer applicable.EM 1110-2-1913

30 Apr 2000

E-4 

### E-5. Design Example Figure E-2 ill ustrates the design of a drainage trench in a thin impervious blanket overlying a shallo w pervio us stratum. The trench drain (Case II) is designed using equations presented in Part E-3 of thi s appendix.m I U1 

# {

.. I 0**~** 243.em eoo·

.:-:. .**-~** '·. 

# }t

Lki!c;-,**-- co:::O-xi~O**  4 om/oea

.. ;·c" k'r •**~** •COOxlo- 4 om/ooe(.03m/mln).': 

# > .... d'•d" kH/kV •.Slm**(200~)** , • .

., . ,_. :·.**-~** ··. :.-
.... ::
.. :. : .**~** .' : :**·--~** ..'
.. 

### : · ..... :·

... :
....**~-** . :·
CROSS SECTION OF LEVEE, FOUNDATION AND DRAINAGE TRENCH bd/d =7.em(25')/61m(200') =0.125; EL2jd•=0.80 and'- 2 =0.75 ,£ 1 1 1 :1' =**S/d'+E~/d'** = 243.8m(800')/61m(200')+0.B • 4.l! =.208
SEEPAGE FLOW PER UNIT LENGTH OF LEVEE, Q 0 : Q 0 - 

## # k H = 0.208x.03m(.1')/mln x 7.6m(25') -.04?4m3 /mpm OF LEVEE or 1.445ni'pm/30.5m(100') OF LEVEE MAX!Ytm HEAD BENEATH LANDSIDE BLANKET, h"' : hoo/H = 

## # .208x.75=.156 OR 15.8,; hoo= 1.56xH=.156x7.6m(25')= 1.17m(3.9')

Figure E-2. Example of design of a drainage trench .. /
DETAILS OF DRAINAGE TRENCH m 

## s: w::::: 0_. )>O 'C' -. N 

## I\).:.. O<D 0-> 

### owEM 1110-2-1913 30 Apr 2000

F-1 

### Appendix F Emergency Flood Protection

F-1. Introduction a. Flood fighting . Flood fighting can be defined as those eme rgency operations that are taken in advance of

and during a flood to prevent or minimize damages to public and private property. As defined herein , flo od fighting includes the hasty construction of emergency levees; the overbuilding of existing levees or n atural river banks; ring and U-shaped levees constructed around facilities or areas of high property value; prese rvationof vital facilities including water treatment plants and wells; power and communicatio n f acilities; protection of sanitary and storm sewer sys tems; and provisions for interior drainage treatment during flood stages. Flood fighting plans should acknowledge that it may not be feasible to protect entire c ommunities based on economic or time and equipment considerations; therefore, evacuation of certain areas may be a necessary facet of an emergency operation. b. Recommen ded local organization . Each community with a flood history should establish an organization and written plans for the purpose of conducting flood fighting operations. These plans should i nclude identification of flood-prone areas and previous high wat er marks; flood fighting or evacuation plans; delegation of responsibilities; lists of important suppliers of materials and special equipment; lists of local contr actors; and establishment of earth borrow sites, etc. The plan should further provide for th e e stablishment of an emergency operation center and list various assi stance programs available, either through the State or Federal government. Further assistance in developing these plans can be provided by the State or local Civil Defense Director in the area. F-2. Flood Barrier Construction a. Introduction . The two basic features of an emergency levee system include the flood barrier, generally c onstructed of earth fill, and t he related interior drainage treatment. It is desirable that individuals assigned to a flood-fight situation have prior knowledge of flood barrier construction, interior drainage, and related flood-fightproblems which they may encounter. They should also be acquainted with the past floo d emergenc yefforts, historical flood stages, and forecasted stages for the community. The followin g i nformation will provide personnel with guidelines based on actual experience. However, it cannot be over emphasized that individual resourcefulness is a key element in a successful flood fight. b. Preliminary work

. (1) Alignment. A complete alignment for the barrier should be established promptly and, if possible, in coopera tionwith State or local floodplain management officials. The alignment should be the shortes t pract icalroute, provide the maximum practical protection, and take advantage of any high ground where practicable

. The flood barrier should be kept as far landward of the river as possible to prevent en croachment on the floodway and to provide maximum space for overbank flows. This is especiall y i mportant for smaller floodways where encroachment would di rectly impact the water surface profile. Sharp bends should be avoided. Topographic, plat, or city street maps may be useful in selecting alignment. In choosing t he alignment, consideration should be given as to whether sufficient time remains to complete con structionbefore the flood crest arrival. Potentially unstable river banks should be avoided. Keep a s many trees and brush between the levee and river as possible to help deflect current, ice, and debris. However, in constricted areas of the river, 1.52 m (5 ft), and preferably 3.05 m (10 ft), should be allowed between the levee toe and vertical obstructions such as tree s. In urban areas, many communities within a flood proneEM 1110-2-1913

30 Apr 2000

F-2 

### area already have some levees in-place. These communities typically fight the flood along this primary line of defense. Moving the alignment farther landward creates problems in determining methods to stop f loodwater backup through storm and sanitary sewer lines. It could a lso leave storm and sanitary lift stations onthe riversi de of the flood barrier. Leaving some homes outside the line of protection also exposes th e w atermains to f

loodwater infiltration. Right-of-way considerations may also influence the final alignment. G enerally, the city or county engineer will assist in laying out the line and grade for the barrier, or a professional surveyo r may be available. However, if help is not available, a hand-level along with a know n elevationcan be used to lay out rough grade. As soon as the alignment is firm, quantities of earthwor k should be estimated for establishing equipment and borrow requirements. (2) Draina ge. In laying out a flood barrier, the problem of interior drainage from snowmelt, rain, o r s ewer backup should be considered. A certain amount of ponding, if valuable property will not be damaged, i s not detrimental and may be allowed. The excess inte rior water can be pumped out over the levee if pumps are available. (3) Borro w area and haul road. The two prime requisites for a borrow area are that adequate material b e available and that the s ite be accessible at all times. The quantity estimate plus an additional 50 percent shouldprovi de the basis for the area requirement. The area must be located so that it will not become is olated from the project by high water. The borrow area should also be located where the present water t able, if known, and the water table levels caused by high water will not hinder or stop its use. If possible, a bo rrow area should be selected which will provide suitable materials for levee construction as covere d below. Local contractors and local officials are the best source of information on available borrow areas. I f undeveloped, the area should b e cleared of brush, trees, and debris, with topsoil and surface humus being s tripped. In cold regions in early spring, it will probably be neces sary to rip the area to remove frozen material. An effortshould be made to borrow from the area in such a manner that the area will be relativel y s mooth and free-dra

ining when the operation is complete. The haul road may be an existing road or street, or it may have to be constructed. To mitigate da mages it is highly desirable to use unpaved trails and roads, orto construct a road if the haul distance is short. In any case, the road should be maintained to avoi d u nnecessary traffic delays. The use of flagmen and warning signs is mandatory at major crossings such as highways, near schools, and at major pedestrian crossings. A borrow area, or source of sand for sandbags, s hould also be located promptly. This can become a critical item of supply in some areas due to long haul, project isolation, etc. It may become necessary to stockpile material near anticipated trouble areas. (4) Equipment. One of the important considerations in earthwork construction is the selection of proper equipment to do the work. Unde r emergency conditions, obtaining normally specified earthwork equipment will be difficult and the work will generally be done with locally available equipment. It may be wise to call fortechnical assistance in the early contract stage to insure that proper and efficient equipment use i s p roposed. If possible, compaction equipment should be used in f lood-barrier construction. This may involve sheepsfoot, rubber-tired, or vibratory rollers. Scrapers should be used for hauling when possible because o f speed (on short haul) and larg e capacity. Truck haul, however, has been the most widely used. A ripper will be necessary for opening borrow areas in the early spring if the ground is frozen. A bulldozer of some size is mandatory on the job to help spread dumped fill and provide minimum compaction. (5) Construction contra

ct. The initiation of a construction contract under emergency conditions is very u nique in that sole judgment as to the competence and capabilities of the contractor lies with field personnel. F ield personnel, therefore, must be somewhat knowledgeable in construction operations. The initial contract is very important in that it delineates what equipment must be accounted for on the project and what i s available for construction. During construction, if it becomes obvious that the equipment provided by the initialcontract is inadequate to provide reasonably good construction or timely completion, a new or supp lemen tal contract may be required. Procedures are the same as in the initial contract. Flexibility may beEM 1110-2-1913 30 Apr 2000

F-3 

### built into the original contract if it can be foreseen that additional pieces of equipment will ultimately b e used. (6) Supplies. Early anticipation of floodfight problems will aid greatly in providing necessary an d s ufficient supplies on hand. These include sandbags, polyeth ylene, pumps, etc. The importance of initiative, resourcef ulness, and foresight of the individual on the project cannot be over emphasized. Technical a ssistance may be invaluable in locating potential pr oblem areas which, with proper materials at hand, could be alleviated early. c. Earth fill levees

. (1) Foundation preparation. Prior to embankment construction, the foundation area along the levee alignme nt should be prepared. This is particularly important if the levee is to be left in place. Since sprin g floodin gis the only condition providing much advance warning, the first item of work in cold region s p robably will be snow removal. The snow should be pushed riverward so as to decrease ponding when the s now melts. Trees should be cut and the stum ps removed. All obstructions above the ground surface should be r emoved, if possible. This will include brush, structures, snags, and similar debris. The foundatio n shou ld then be stripped of topsoils and surface humus. (Clearing and grubbing, structure removal, an d stripping should be performed only if time permits.) Stripping may be impossible if the ground is frozen. I n this case, the foundation should be ripped or scarified, if possible, to provide a rough surface for bond with theembankment. Every effort should be made to remove all ice or soil containing many ice lenses. Frost or frozen ground can give a false sense of security in the early stages of a flood fight. It can act as a rigid b oundary and support the levee; but on thawing, soil strength may be reduced sufficiently for cracks or slides to develop. It also forms an impervious barrier to prevent seepage. This may result in a considerabl e buildupin pressure under the soils landward of the levee, and upon thawing pressure may be sufficient to c ause sudden blowouts. If this condition exists it must be monitored, and one must be prepared to act quickly if sliding orsand boils develop. If stripping is possible, the material should be pushed landward an d r iver ward of the toe of levee and windrowed. After the flood, this material may be spread on the slopes to provide topsoil for vegetation. (2) Materials. Earth fill material s for emergency levees will usually come from local borrow areas. An a ttempt should be made to utilize materials which are c ompatible with the foundation materials. Due to time limitations, however, any local materials may be used if reasonable construction procedures are followed. T he mater ial should be relatively clean (free of debris) and should not contain large frozen pieces of earth. (a) Clay. Clay is preferred because the section can be made smaller (steeper side slopes). Clay is also r elatively impervious (will not readily permit passing of water) and has relatively high resistance to erosion i n a compacted state. A disadvantage in using clay is that adequate compaction is difficult to obtain without p roper equipment and when the material is wet. Another disadvantage is if the clay is wet and sub-freezing t emperatures occur, this may cause the material to freeze in the borrow pit and hauling equipment. Weather could cause delays and should definitely be considered in the overall construction effort. (b) Sand. If sand is used, the section should comply as closely as possible with recommendations i n paragraph F-2.C.(3)(b) below. Steep slopes without poly coverage on the riverside slope will result i n s eepage through the levee that exits on the landward slope causing sl umping of the slope and potential overall failure if it occurs over an extended period of time. (c) Silt. Material which is primarily silt should be avoided. If used, poly facing must be applied to the riverslope. In addition to being very erodible, silt, upon wetting, tends to collapse if not properl y compacted.EM 1110-2-1913

30 Apr 2000

F-4 

### (3) Levee section. (a) Gener al. In standard levee design the configuration of the levee is generally dictated by th e f oundation soils and the materials available for construction. Therefore, even under emergency conditions, an attemptshould be made to make the embankment compatible with the foundation. Information o n f oundation soils may be available from local officials or engineers, and it should be utilized. The two levee se ctions cited below are classical and idealized, and usual field conditions depart from them to variou s degrees. Howe ver, if they are used as a guide, possible serious flood-fight problems could be lessene d d uring high wate

r. In determining the top width of any type of section, consideration should be given as to whether a revised forecast will require additional fill to be placed. A top width adequate for construction eq uipment will facilitate raising the levee. Finally, actual dike construction will, in most cases, depend on time, materials, and right-of-way available. (b) Sandsection. Use 1 V (Vertical) on 3 H (Horizontal) toward a river, 1 V on 5 H landward slope, and 3.05-m (10-ft) top width. (c) Clay section. Generally 1 V on 2 1/2 H slopes are used but for low height levees 1 V on 2 H slopes h ave been used successfully. It is important t o always use a 3.05 m (10 ft) top width. When clay levees are cons tructedon pervious foundations, the bottom width may not be adequate to reduce the potential fo r foundat ion

piping. This can be accomplished by using berms either landward or riverward of the levee

. Ber m thickness will be site specific. Berms reduce the potential for foundation piping, but do not reduc e foundation seepage. (4) Placement and compaction. As stated above, obtaining pr oper compaction equipment for a given soil type will be difficult. It is expected in most cases that the only compaction will be from that due to th e h auling and spreading equipment; i.e., construction traffic routed over the fill. Levee height should provide 0 .61 m (2 ft) of freeboard above forecast floo d crest. In urban areas, the upstream end of the project should use a larger freeboard than the downstream end. (5) Slope protection. (a) General. Methods of protecting levee slopes from current scour, wave wash, seepage, and debri s d amage are numerous and

varied. However, during a flood emergency, time, availability of materials, cost and construction capability preclude the use of all accepted methods of permanent slope protection. Field personnel m

ust decide the type and extent of slope protection the emergency levee will need. Several methods of protection have been established which prove highly effective in an emergency. Again , resourcefulness on the part of the field personnel may be necessary for success. (b) Polyethylene and sandbags. Experience has shown that a combination of polyethylene (poly) and sandbags is one of the most expedient, effective, and economical methods of combating slope attack in a flood situation. Poly and sandbags can be used in a variety of combinations, and time becomes the factor that may determine which combination to use. Ideally, poly and sandbag protection should be placed in the dry. However, many cases of unexpected slope attack will occur during high water, and a method fo r placement in the wet is covered below. See Figures F-1 to F-4 for suggested methods of laying poly an d sandbags

. Since each flood fight project is generally unique (river, personnel available, materials, etc.) , specif icdetails of placement and materials handling will not be covered. Personnel must be aware o f resources available when using poly and sandbags.

### SECTION

NOTE: Alternate direction of socks with bottom layer par.ollel to flow, nex-t Ioyer perpendicular to flow, etc. Lap unfilled portion under: next · EM 1110-2-1913 30 Apr 2000

sack. Tyino or sewino liocka not nece"ary.

## ~t Ta.mp thoroughly In place. s.acks &houtd be approximately V2 

### METHOD OF LAPPING SACKS lull of sand.

Figure F-1. Sandbag barrier
(c) Toe anchorage and poly placement. Anchoring the poly along the riverward toe is important for a successful job. It may be done in three different ways: ( 1) After completion of the levee, a trench excavated along the toe, poly placed in the trench, and the trench backfilled; (2) Poly placed flat-out away from the toe, and earth pushed over the flap; and (3) Poly placed flat-out from the toe and one or more rows of sandbags placed over the flap. The poly should then be unrolled up the slope and over the top enough to allow for anchoring with sandbags. Poly should be placed from downstream to upstream along the slopes and overlapped at least 0.61 m (2ft). The poly is now ready for the "hold-down" sandbags.

F-5EM 1110-2-1913 30 Apr 2000



# TYPES OF WOOD AND EARTH LEVEES

RIVERSIDE LANDS IDE

(I' Material to be tamped CI against bottom board 

# li\ 50x1 00mm(2x4in)Approx1.5m(5ft)long .6m{2ft)Min. penetratration 50x100 OR 100x200mm {2x4 OR 4x4in) Posts 25x304.8mm(lx12in) Boarding



# CD BASE WIDTH TWO TIMES HEIGHT 

## ® FLASH BOARD LEVEE BOX LEVEE

Figure F-2. Flash board and box levee RIVERSIDE

(d) Slope anchorage. It is mandatory that poly placed on levee slopes be held down. An effective method of anchoring poly is a grid system of sandbags, unless extremely high velocities, heavy debris, or a large amount of ice is anticipated. Then a solid blanket of bags over the poly should be used. A grid system can be constructed faster and requires fewer bags and much less labor than a total covering. Various grid systems include vertical rows oflapped bags, two-by- four lumber held down by attached bags, and rows

F-6EM 1110-2-1913 30 Apr 2000

1 BAG EVERY 1.82m(6ft)

SAND BAGS STAGGERED TO PROTECT POLYETHYLENE FROM DEBRIS & ICE



# -- EXCESS POLYETHYLENE ROLLED FOR FUTURE DIKE RAISE

GROUND UNE

PLACE EDG.E OF POLYETHYLENE IN 152mm(16in) DEEP TRENCH (DEEPER TRENCH IS DESfRABLE) OR LAYOUT FROM TOE LACE .15m(6mil) POLYETHYLENE LOOSELY WITH SLACK) ON THE SMOOTH SURFACE 

## SECTION

5

## dV~9 SC1f1
- 

## METHODS OF ANCHORING POLYETHYLENE .15rnm(6mil) BLACK POLYETHYLENE IS THE MOST DESIRABLE .15mm(6mil) CLEAR SECOND .10mm(4mil) BLACK**THIRJ2~** .10mm(4mil) CLEAR FOURTH & .Oomm(2mil)**POLYETHYLE~E** SHOULD**O~LY** BE USED AS A LAST RESORT.

Figure F-3. Placement of polyethylene sheeting on temporary levee F-7EM 1110-2-1913 30 Apr 2000



# ;'

I

'· '· 

## -

Figure F-4. Placement of polyethylene sheeting in the wet

of bags held by a continuous rope tied to each bag. Poly can also be held down by a system using two bags tied with rope and the rope saddled over the levee crown with a bag on each slope. (e) Placement in the wet. In many situations during high water, poly and sandbags placed in the wet must provide the emergency protection. Wet placement may also be required to replace or maintain damaged poly or poly displaced by current action. Figure F-4 shows a typical section oflevee covered in the wet. Sandbag anchors are formed at the bottom edge and ends of the poly by bunching the poly around
F-8EM 1110-2-1913 30 Apr 2000

F-9 

### afistful of hand

or rock and tying the sandbags to this fist-sized ball. Counterweights consisting of two or moresandbags connected by a length of 6.35-mm (1/4-in.) rope are used to hold the center portion of the poly down. T he number of counterweights will depend on the uniformity of the levee slope and current v elocity. Placement of the pol y consists of first casting out the poly sheet with the bottom weights and then adding cou nterweights to slowly sink the poly sheet into place. The poly, in most cases, will continue to move down slope until the bottom edge reaches the toe of the slope. Sufficient counterweights should b e a dded to insure that no air voids exist between the poly and the levee face and to keep the poly from flapping or being carried away in the current. For this reason, it is im portant to have enough counterweights prepared prior to the placement of the sheet. (f) Overuse of poly. In past floods there has been a tendency to overuse and in some cases misuse poly o n slopes. For example, on well compacted clay embankments, in areas of relatively low velocities, use of poly wouldbe unnecessary. Also, placement of poly on landward slopes to prevent seepage must not b e done. It will only force seepage to another exit and may prove detrimental. Poly has been used on th e la ndsideslope of levees to prevent rainwater from entering a crack where slope movement has occurred , p articularly in fat clay soils. Keeping water out of the cracks resulting from slope movements is desirable to prevent lubrication and additional hydrostatic pressure on the slip surface. (g) R iprap. Riprap is a positive means of providing slope protection and has been used in a few cases where erosive forces were too large to effectively control by other means. Objections to using riprap when f lood fighting are: (1) rather costly; (2)large amount necessary to protect a given area; (3) availability; and (4) little control over its placement, particularly in the wet. (h) Groins. In the past, small groins, extending 3.05 m (10 ft) or more into the channel were effective i n deflecting current away from the levee s. Groins can be constructed by using sandbags, snow fence, rock, c om pacted earth, or any other substantial materials that are available. Preferably groins should be placed in the dry and at locations where severe scour may be anticipated. Consideration of the hydraulic aspects of placing groins should be given, because haphazard placement may be detrimental. Hydraulic technical assistanceshould be sought if doubts arise in the use of groins. Construction of groins during high water will be ve ry difficult and results will generally be minimal. If something other than compacted fill is used, s ome form of anchorage or bonding should be provided. (For example, snow fence anchored to a tree beyond the toe of the levee.) (i) Log booms. Log booms have been used to protect levee slopes from debris or ice attack. Logs are c abled together and anchored with a dead man in the levee. The boom will float out in the current and, depending on log size, will deflect floating objects. (j) Misc ellaneous measures. Several other methods of slope protection have been used. Straw bale s pegged into the slope may be successful against wave action, as is straw spread on the slope and overlain with snow fence. (6) Sandbag dikes. The sandbag dike should not be considered as a primary-flood barrier. The main objection s to their use are that the materials (bags and sand) are quite costly; they require a tremendou s a mount of manpower; and are time consum ing to construct. They are also very difficult to raise if the flood f orecasts are revised. Sandbag dikes should be used wher e a very low and relatively short barrier is required a nd earth fill would not be practicable, such as in the freeboard range along an arterial street. They are very usefulin constricted areas such as around or very close to buildings, where rights-of-way would preclude u sing earth fill. They are also useful where tempora ry closure is required, such as roads and railroad tracks. A polyethylene seepage barrier should be incorporated into the sandbag structure. The poly must be on the riverward slope and brought up immediately behind the outermost layer of bags. The poly should b eEM 1110-2-1913

30 Apr 2000

F-10 

### keyed-into a t rench at the toe and anchored, or, at best, lapped under the sandbags for anchorage. Se e F igure F-1 for recommended practices in sandbag dike constr uction. A few points to be aware of in sandbag c onstruction are: (1)sand, or predominantly sandy or gravelly material should be used; (2) extremely fine, c lean sand, such as washed mortar sand, should be avoided; (3) bags should be 1/2 full; (4) bags should be lappedwhenplacing; (5) bags should be tamped tightly in place; and (6) the base width should be wide enough to resist the head at high water. Sandbagging is also practical for raising a narrow levee, or when construction equipment cannot be used. Sandbag raises should be limited to 0.91 m (3 ft), if possible. (7)Miscellaneous flood barriers. In addition to earth fill and sandbag levees, two other types of flood barriers should be mentioned. They are the flashboard and the box levees, both of which are constructe d u sing lumber and eart

h fill (see Figure F-2). They may be used for capping a levee or as a barrier in highly c onstricted areas. Two disadvantages in using these barriers are the long construction time involved and very high cost. Therefore, these barriers are not recommended, unle ss a very unusual situation warrants their use. F-3. Emergency Interior Drainage Treatment

a. General . High river stages often disrupt the normal drainage of sanitary and storm sewer systems, render sewage treatment plants inoperative, and cause backup in sewers and the discharge of untreate d sewage directly into the river. When the river recedes, some of the sewage may be trapped in low lyin g p ockets to remain as a possible source of contamination. Hastily constructed dikes intended to keep out river w aters may als o seal off normal outlet channels for local runoff, creating large ponds on the landward side of the dikes, making the levees vulnerable from both sides. If the ponding is excessive, it may nullify th e p rotection a

fforded by the dikes even if they are not overtopped. Sewers may also back up because of this ponding. b. Preliminary work. In order to arrive at a reasonable plan for interior drainage treatment, several items of information must be obtained by field personnel. These are: (1) Size of drainage area. (2) Pumping capacity and/or ponding required. (3) Basic plan for treatment. (4) Storm and sanitary sewer and water line maps, if available. (5) Location of sewer outfalls (abandoned or in use). (6) Inventory of available local pumping facilities. (7) Probable location of pumping equipment. (8) Whether

additional ditching is necessary to drain surface runoff to ponding and/or pump locations. (9) Location of septic tanks and drain fields (abandoned or in use).5000 per × 0

. 378 m 3 /person/ day 24 hr × 60 min ' 1

. 314 m 3 /min 5000 persons × 100 gal/person/ day 24 hr × 60 min/hr ' 347 gpm EM 1110-2-1913 30 Apr 2000

F-11 

### c. Pumps, types, sizes, and capacities

. (1) Storm sewer pumps. Table F-1 indicates the size of pump needed to handle the full flow discharge f rom sewer pipes up to 610 mm (24 in.) in diameter. Table F-2 shows sizes and capacities of agricultural-- type pumps which may be useful in ponding areas.

Table F-1 Matching Pipe Size to Pump Size Sewer Pipe Size, mm (in.) Probable Required Pump Size, mm (in.) 152.4 (6) 50.8 (2) 203.2 (8) 50.8 to 76.2 (2 to 3) 254.0 (10) 76.2 to 101.6 (3 to 4) 304.8 (12) 101.6 to 152.4 (4 to 6) 381.0 (15) 152.4 to 203.2 (6 to 8) 457.2 (18) 152.4 to 254 (6 to 10) 533.4 (21) 203.2 to 254 (8 to 10) 609.6 (24) 254 to 304.8 (10 to 12)



### (2) Fire engi ne pumps. The ordinary fire pumper has a 101.6 mm (4-in.) suction connection and a pumping capacity of about 2838.75 R 

### /min (750 gpm). Use only if absolutely necessary. ( 3) Pump discharge piping. The Crisafulli pumps are generally supplied with 15.24-m (50-ft) lengths o f butyl rubber hose. Care must be taken to prevent damage to the hose. Irrigation pipe or small diameter c ulverts will also serve as discharge piping. Care should be taken to extend pump discharge lines riverward farenough to not cause erosion of the levee. On 304.8 mm (12-in.) or larger lines, substantial anchorage is required. These pumps must not be operated on slopes greater than 20 degrees from horizontal. (4) Sanitary sewage pumping. During high water, increased infiltration into sanitary sewers may necessitate increased pumping at the sewage treatment plant or at manholes at various locations to keep the syste m functioning. To estimate the quantity of sewage, allow 0.378 m (100 gal) per capita per day fo r 3 

### s anitary sewage and an infiltration allowance of 35.28 m per km-day (15,000 g/mile-day) of sewer per day. 3 

### I n some cas es, it will be necessary to pump the entire amount of sewage, and in other cases only the added infiltration will have to be pumped to keep a system in operation. E xample: Estimate pumping capacity required at an emerg ency pumping station to be set up at the first manho le above the sewage treatment plant for a city of 5,000 population and approximately 48.24 km ( 30 miles) of sewer (estimated from map of city). In this case, it is assumed that the treatment plant will not operate at all. Required capacity = (infiltration) + (sewage)
Sewage demand:35

. 31 m 3 km × 48

. 24 km 1

24 hr × 60 min ' 1

. 18 m 3 /min 15000 gal/mile/ day × 30 miles 24 hr × 60 min/hr ' 312 gpm EM 1110-2-1913 30 Apr 2000

F-12 Table F-2 Crisafulli Pumps - Model CP 2 in. to 24 in. Size m /min Head Elec. Gas or Diesel 3 a mm (in.) (gal/min) m (ft) kW (hp) kW (hp) 50.8 (2) 0.56 (150) 0.745 (1) 101.6 (4) 1.88 (500) 5.59 (7.5) 11 .18 (15) 152.4 (6) 3.76 (1000) 7.45 (10) 14. 9(20) 203.2 (8) 11.27 (3000) 3.04 (10) 11.18 (15) 18 .62 (25) 304.8 (12) 18.79 (5000) 18.62 (25) 29. 8 (40) 406.4 (16) 35.70 (9500) 29.8 (40) 48. 4 (65) 609.6 (24) 93.95 (25000) 55.88 (75) 104 .3 (140) 50.8 (2) 0.49 (130) 0.745 (1) 101.6 (4) 1.84 (490) 7.45 (10) 14. 9(20) 152.4 (6) 3.19 (850) 11.18 (15) 18 .62 (25) 203.2 (8) 9.21 (2450) 6.1 (20) 14.9 (20) 26 .08 (35) 304.8 (12) 14.09 (3750) 22.35 (30) 37. 2(50) 406.4 (16) 30.06 (8000) 33.52 (45) 63. 3 (85) 609.6 (24) 71.4 (19000) 74.5 (100) 141 .6 (190) 50.8 (2) 0.45 (120) 0.745 (1) 101.6 (4) 1.79 (475) 8.94 (12) 18 .62 (25) 152.4 (6) 2.99 (795) 14.9 (20) 26 .08 (35) 203.2 (8) 8.08 (2150) 9.84 (30) 18.62 (25) 33 .52 (45) 304.8 (12) 12.96 (3450) 26.08 (35) 52 .15 (70) 406.4 (16) 26.68 (7100) 44.70 (60) 93 .12 (125 ) 609.6 (24) 62.38 (16600) 93.12 (125) 186 .24 (250 ) Use high head pumps for heads over 6.1 m or 59.71 KPa (20 ft). a



### Infiltration:

Required pumping capacity: 2.49 m /min (659 gpm). From Table F-3, use one 101.6 mm (4-in.) pump 3 

### or its equivalent.

Table F-3 Marlow Self Priming Centrifugal Pumps Size Capacity Horsepower b mm (in.) AGC Rating m /min (gal/min) kW (hp) a 3 38.1 (1.5) 4M 0.25 (67) 1.34 (1.8) 50.8 (2) 7-10M 0.44-0.63 (117-167) 1.71-3.66(2.3-4.9) 76.2 (3) 20-30M 1.26-1.89 (334-500) 3.66-8.36 (4.9- 11.2) 101.6 (4) 30-40M 1.89-2.51 (500-665) 14.92-28.94 (20- 38.8) 152.4 (6) 90M 5.67 (1500) 32.46 (43.5) 203.2 (8) 125M 7.87 (2080) 46.25 (62) 254.0 (10) 12.6 (3330) 46.25 (62) Gallons per hour, thousands. aAt 75 kPa (7.67-m, 25-ft) head. bEM 1110-2-1913 30 Apr 2000

F-13 

### d. Metal culverts

. (1) P umping of ponded water is usually preferable to draining the water through a culvert since th e t ailwater (drainage end of culvert) could increase in elevation t o a point higher than the inlet, and water could bac k up into the area being protected. Installation of a flapgate at the outlet end may be desirable to minimize backup. (2) Table F-4 sh ows the capacity of corrugated pipe culverts on a flat slope, with H factor (head ) representing the difference between the headwater level and tailwater level, assuming the outlet i s s ubmerged. If the outlet is not submer ged the head equals the difference in elevation between the headwater l evel and 0.6 of the diameter of the pipe measured from the bottom of the pipe upward. The capacity would change for smooth pipe, pipe laid on a slope, or if headwalls or wingwalls are used. (3) If a culvert is desired to pass water from a creek through a levee, a computation of the drainag e basin by an engineer is required to determine pipe size. e. Preventing backflow in sewer lines

. ( 1) Watertight sluice gates or flap gates are one answer. Emergency stoppers may be constructed of lu mber, sandbags, or other materials, using poly as a seal, preferably placed on the discharge end of th e outfall pipe. ( 2) Figures F-5 and F -6 contain manufacturer's literature on prefabricated rubber pipe stoppers which can be placed in the outlet opening of a manhole. ( 3) Figures F-7 to F-11 illustrate metho ds of sealing off the outlet openings of a manhole with standard materials which are

normally available so that the manhole may be used as an emergency pumping station. F-4. Flood Fight Problems

a. General . Pr oblem situations which arise during a flood fight are varied and innumerable. Th e problems covered below and in “Emergency Interior Drainage Treatment” are those which are considered mostcritical to t he integrity of the flood barrier system. It would be impossible to enumerate all of th e p roblems, such as supplies, personnel, communication, etc., which field personnel must handle. The most valuableasset of field personnel under emergency conditions is their common sense. Many problems can b e solved instantly and with less effort through the application of good common sense and human relations. Problems, such as those below, can be identified early only if a well organized levee patrol system with a g ood commun

ication system exists. The problems are presented with the assumption that high water is on the levee slopes. b. Overto

pping . Overtopping of a levee is the flowing of water over the levee crown. Since mos t emergencylevees are of an urban nature, overtopping should be prevented at any cost. Overtopping wil l general lybe caused by: (1) unusual hydrologic phenomena, including unexpected rainfall, faster than expected rainfall , faster than expected snowmelt, and ice and debris blockages, which cause a much higher stage tha n anticipated; (2) insufficient time in which to complete the flood barrier; or (3) unexpecte d settlementof

the barrier. Generally, the flood barriers are constructed 0.61 m (2 ft) above the crest pre

diction. If the cr

est prediction is raised during construction, additional height must be added to the barrier. Cappin gshould be done with earth fill or sandbags, using normal construction procedures. For leve e construction, the 3.05 m (10 ft) top width allows the barrier to be raised relatively quickly with regula rEM 1110-2-1913

30 Apr 2000

F-14 Table F-4a Capacity of Corrugated Metal Pipe Culverts Without Headwalls and With Outlet Submerged (outlet control-full flow) (Circular) (metric Units)

Dia. In mm 0.003 0.006 0.008 0.011 0.014 0.017 0.023 0.028 0.034 0.040 0.045 0.050 0.056 0.071 0.085 0.1 0.113 CUBIC METERS PER SECOND Pipe Pressure in kPa
304.2 2.98 4.17 5.07 5.96 6.6 7.15 8.34 9.23 10.1 11 11.9 12.5 13.1 14.9 16.1 17.3 18.5Length = 61 m 381 5.07 7.15 8.64 10.13 11.3 12.2 14.3 15.8 17.3 18.8 20.3 21.2 22.4 25 27.4 29.5 32.8 457.2 7.75 10.73 13.11 15.5 17 18.5 21.5 23.8 26.2 28.3 29.8 32.8 32.8 38.7 41.7 44.7 47.7 533.4 10.7 15.2 18.5 21.4 23.8 26.2 29.8 32.8 35.8 38.7 41.7 44.7 47.7 53.6 56.6 62.6 65.6 609.6 14.6 20.3 25 28.6 32.8 35.8 41.7 44.7 50.7 53.6 56.6 59.6 62.6 71.5 77.5 83.4 89.4 685.8 18.5 26.2 32.8 35.8 41.7 44.7 53.6 60 62.6 68.5 74.5 77.5 83.1 92.3 101 107 116 762.0 23.2 32.8 41.7 47.7 50.7 56.6 65.6 74.5 80.5 86.4 95.4 98.3 98 116 125 137 146 914.4 35.8 47.7 59.6 68.5 77.5 83.4 98.3 110 119.2 128.1 137 146 155 170 188 203 215 1066.8 47.7 68.5 83.4 95.4 107.2 116.2 134.1 152 164 178.8 191 203 212 235 256 277 298 1238.4 65.6 89.4 110 128 143 155 179 203 221 238.4 253 268 280 316 349 373 399 1371.6 83.4 116.2 143 164 181.8 200 232 260 289 304 325 346 361 405 444 477 510 1524 101 143 175 203 226.5 247 286 319 352 375 400 423 447 498 542 587 626

Dia. In mm 0.003 0.006 0.008 0.011 0.014 0.017 0.023 0.028 0.034 0.040 0.045 0.050 0.056 0.071 0.085 0.100 0.113 CUBIC METERS PER SECOND Pipe Pressure in kPa
304.2 2.38 3.27 4.17 4.8 5.4 6 6.9 7.5 8.3 8.9 9.5 10.1 10.7 11.9 13.1 14.3 15.2Length = 122 m 381 4.17 5.66 7.15 8.05 9.24 10.1 11.6 12.8 14.3 15.5 16.4 17.6 18.5 20.6 22.6 24.4 26.2 457.2 6.26 8.94 11 12.8 14.3 15.5 17.9 20.3 22 23.8 25.6 26.8 28.6 32.8 35.7 38.7 41.7 533.4 8.94 12.8 15.8 18.2 20.3 22.1 25.6 28.6 32.8 35.8 35.8 38.7 42 44.7 50.7 536 56.6 609.6 12.5 17.6 21.5 25 28 29.8 35.8 38.7 44.7 47.7 51 53.6 57 62.6 68.5 74.5 80.5 685.8 16.4 23.2 28.6 32.8 35.8 41.7 47.7 51 56.6 62.6 66 68.6 74.5 83 89.4 98.3 104 762.0 20.9 29.2 35.8 41.7 47.7 50.7 60 66 71.5 77.5 83 89.4 92 104 113 125 131 914.4 29.8 44.7 53.6 62.6 71.5 77.5 89.4 98 107 116 125 134 140 158 173 185 197 1066.8 44.7 62.6 77.5 89.4 98.3 107 125 140 152 164 175 185 197 221 238 262 277 1238.4 59.6 83.4 104.3 119.2 134 146 167 188 206 220 238 250 265 295 25 352 378 1371.6 77.5 107.3 134.1 152 170 188 215 241 265 286 307 325 343 381 417 453 486 1524 95 134.1 164 191 215 232 268 298 328 358 381 405 426 477 522 566 602

Dia. In mm 0.003 0.006 0.008 0.011 0.014 0.017 0.023 0.028 0.034 0.040 0.045 0.050 0.056 0.071 0.085 0.100 0.113 CUBIC METERS PER SECOND Pipe Pressure in kPa
304.2 2.09 2.98 3.6 4.17 4.77 5.07 5.96 6.56 7.15 7.75 8.12 8.64 9.24 10.4 11.3 12.2 13.11Length = 197 m 381 3.58 5.07 6.3 7.15 8.05 8.94 10.1 11.3 12.5 13.4 14.3 15.2 16.1 17.9 19.7 21.2 22.6 457.2 5.66 8.05 9.8 11.3 12.5 13.7 15.8 17.6 19.4 20.9 22.3 23.8 25 27.7 29.8 32.8 35.8 533.4 8.05 11.6 14.3 16.4 18.2 19.7 22.9 25.9 28.3 29.8 32.8 35.8 35.8 41.7 44.7 47.7 50.7 609.6 11.3 16.1 19.7 22.6 25 27.4 32.8 35.8 38.7 41.7 44.7 47.7 50.7 56.6 65.6 65.6 71.5 685.8 14.9 21.1 25.9 29.8 33 35.8 41.7 47.7 50.7 56.6 59.6 62.6 65.6 74.5 80.5 86.4 92.4 762.0 19.1 26.8 32.8 38.7 42 47.7 53.6 59.6 66 68.5 74.5 80.5 83.4 95.4 104 110 119 914.4 28.9 41.7 50.7 56.6 65.6 71.5 80.5 92.4 98.3 107 113 122 128 143 155 167 179 1066.8 41.7 56.6 72 83.4 92.3 101 116 131 143 152 164 173 182 203 221 238 256 1238.4 56.6 80.5 95 113 125 137 158 176 191 206 221 232 244 274 298 322 346 1371.6 71.5 101 125 143 161 175 203 229 247 268 286 304 322 358 390 423 453 1524 92.3 128 158 182 203 221 256 289 313 337 358 381 402 447 495 530 566EM 1110-2-1913 30 Apr 2000

F-15 Table F-4b Capacity of Corrugated Metal Pipe Culverts Without Headwalls and With Outlet Submerged (outlet control-full flow) (Circular) (Metric Units)
Dia. m PER SECOND In m 3 Head on Pipe in m 0.003 0.006 0.008 0.011 0.014 0.017 0.023 0.028 0.034 0.040 0.045 0.051 0.057 0.071 0.085 0.099 0.113 0.305 0.3 0.43 0.53 0.61 0.67 0.73 0.85 0.94 1.04 1.13 1.22 1.28 1.34 1.52 1.64 1.77 1.88Length = 6.10 m 0.381 0.52 0.73 0.88 1.04 1.16 1.25 1.46 1.61 1.77 1.92 2.07 2.16 2.29 2.56 2.8 3.02 3.35 0.457 0.79 1.1 1.34 1.58 1.74 1.89 2.19 2.44 2.68 2.9 3.05 3.35 3.35 3.96 4.27 4.57 4.88 0.533 1.10 1.55 1.89 2.19 2.44 2.68 3.05 3.35 3.66 3.96 4.27 4.57 4.88 5.49 5.79 6.4 6.71 0.610 1.49 2.07 2.56 2.93 3.35 3.66 4.27 4.57 5.18 5.49 5.79 6.1 6.4 7.32 7.92 8.53 9.14 0.686 1.89 2.68 3.35 3.66 4.27 4.57 5.49 6.1 6.4 7.01 7.62 7.92 8.53 9.45 10.36 10.79 11.89 0.762 2.38 3.35 4.27 4.88 5.18 5.79 6.7 7.62 8.23 8.84 9.75 10.06 10.7 11.89 12.8 14.02 14.94 0.914 3.66 4.88 6.1 7.01 7.92 8.53 10.06 11.28 12.19 13.11 14.02 14.94 15.85 17.37 19.2 20.72 21.95 1.067 4.88 7.01 8.53 9.77 10.79 11.89 13.72 15.54 16.76 18.29 19.5 20.73 21.64 24.07 26.21 28.35 30.48 1.219 6.71 9.14 11.28 13.11 14.63 15.84 18.29 20.73 22.56 24.38 25.9 27.42 28.65 32.31 35.66 38.1 40.84 1.372 8.53 11.89 14.63 16.76 18.59 20.42 23.72 26.52 29.52 31.09 33.22 35.36 36.88 41.45 45.41 48.77 52.12 1.524 10.36 14.63 17.98 20.73 23.16 25.30 24.26 32.61 35.97 38.4 40.89 3.28 45.72 50.9 55.47 60.04 64.0

Dia. m PER SECOND In m 3 Head on Pipe in m 0.003 0.006 0.008 0.011 0.014 0.017 0.023 0.028 0.034 0.040 0.045 0.051 0.057 0.071 0.085 0.099 0.113 0.305 0.26 0.34 0.43 0.49 0.55 0.61 0.70 0.76 0.85 0.91 0.97 1.04 1.1 1.22 1.34 1.46 1.55Length = 12.19 m 0.381 0.43 0.58 0.73 0.82 0.94 1.04 1.19 1.31 1.46 1.58 1.68 1.8 1.89 2.10 2.32 2.5 2.68 0.457 0.64 0.91 1.13 1.31 1.46 1.58 1.83 2.07 2.26 2.44 2.62 2.74 2.93 3.35 3.66 3.96 4.27 0.533 0.91 1.31 .61 1.86 2.07 2.26 2.62 2.93 3.35 3.66 3.66 3.96 4.27 4.57 5.18 5.49 5.79 0.610 1.28 1.8 2.19 2.56 2.86 3.05 3.66 3.96 4.57 4.88 5.18 5.49 5.79 6.4 7.01 7.62 8.23 0.686 1.68 2.38 2.93 3.35 3.66 4.27 4.88 5.18 5.79 6.4 6.71 7.01 7.62 8.53 9.14 10.1 10.67 0.762 2.13 2.99 3.66 4.27 4.88 5.18 6.1 6.71 7.32 7.92 8.53 9.14 9.45 10.7 11.58 12.8 13.41 0.914 3.05 4.57 5.49 6.4 7.32 7.92 9.14 10.1 10.79 11.89 12.8 13.72 14.32 16.15 17.68 18.9 20.11 1.067 4.57 6.4 7.92 9.14 10.1 10.97 12.8 14.32 15.54 16.76 17.98 18.9 20.11 22.56 24.36 26.82 28.35 1.219 6.1 8.53 10.69 12.19 13.72 14.94 17.07 18.20 14.69 22.56 24.38 25.6 27.13 30.17 33.22 36.0 38.71 1.372 7.92 10.87 13.72 15.54 17.37 19.20 21.95 24.69 27.13 29.26 31.39 33.22 35.06 39.01 42.67 46.32 49.7 1.524 9.75 13.72 16.76 19.51 21.95 23.77 27.43 30.48 33.53 36.58 39.01 41.45 43.59 48.77 53.34 57.91 61.6

Dia. m PER SECOND In m 3 Head on Pipe in m 0.003 0.006 0.008 0.011 0.014 0.017 0.023 0.028 0.034 0.040 0.045 0.051 0.057 0.071 0.085 0.099 0.113 0.305 0.21 0.3 0.36 0.43 0.49 0.52 0.61 0.67 0.73 0.79 0.85 0.88 0.94 1.07 1.16 1.25 1.34Length = 18.29 m 0.381 0.37 0.52 0.64 0.73 0.82 0.91 1.04 1.16 1.28 1.37 1.46 1.55 1.64 1.83 2.0 2.16 2.32 0.457 0.58 0.82 1.0 1.16 1.28 1.4 1.61 1.8 1.98 2.13 2.29 2.44 2.56 2.83 3.05 3.35 3.66 0.533 0.82 1.19 1.46 1.68 1.86 2.01 2.35 2.65 2.9 3.05 3.35 3.66 3.66 4.27 4.57 4.88 5.18 0.610 1.16 1.65 2.01 2.32 2.56 2.8 3.35 3.66 3.96 4.27 4.57 4.88 5.18 5.79 6.4 6.71 7.32 0.686 1.52 2.16 2.66 3.05 3.35 3.66 4.27 4.88 5.18 5.74 6.1 6.4 6.7 7.62 8.23 8.84 9.45 0.762 1.95 2.74 3.35 3.96 4.26 4.88 5.49 6.1 6.71 7.01 7.62 8.23 8.53 9.75 10.67 11.28 12.14 0.914 2.96 4.27 5.18 5.79 6.7 7.32 8.23 9.45 10.1 10.70 11.58 12.5 13.11 14.63 15.85 17.07 18.29 1.067 4.26 5.79 7.32 8.53 9.45 10.36 11.89 13.41 14.6 15.54 16.76 17.68 18.59 20.73 22.56 24.38 26.21 1.219 5.79 8.23 9.75 11.58 12.8 14.02 16.15 17.98 19.51 14.63 22.56 23.77 25.0 28.04 30.48 32.92 35.36 1.372 7.32 10.36 12.8 14.63 16.45 17.98 20.73 23.47 25.3 27.43 29.26 31.09 32.92 36.58 39.93 43.28 46.33 1.524 9.44 13.11 16.15 18.59 20.73 22.56 26.21 29.57 32.0 34.44 36.58 39.01 41.15 45.72 50.6 54.25 57.91EM 1110-2-1913 30 Apr 2000

Figure F-5. Prefabricated rubber pipe stoppers for outlet opening of a manhole



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construction equipment. However, if the flood barrier consists of poly and sandbags having a minimum top width and limited base width, raising the barrier is very time consuming and labor intensive. Experience has shown that sandbag barriers over 0.91 m (3 ft) in height do not perform well for prolonged floods; underseepage becomes a real problem and failures have occurred as the water approaches the top of protection.



### c. Seepage. Seepage is percolation of water through or under a levee, generally appearing first at the landside toe. Seepage through the levee is applicable only to a relatively pervious section. Seepage, as such, is generally not a problem unless (1) the landward levee slope becomes saturated over a large area; (2) seepage water is carrying material from the levee; or (3) pumping capacity is exceeded. Seepage which causes severe sand boils and piping is covered below. Seepage is difficult to eliminate, and attempts to do so may create a much more severe condition. Pumping of seepage should be held to a minimum, based on the maximum ponding elevation without damages. Seepage should be permitted if no apparent ill-effects are observed, and if adequate pumping capacity is available. If seepage causes sloughing of the landward slope, it should be flattened to 1 Von 4H or flatter. Material for flattening should be at least as pervious as the embankment material.

F-17EM 1110-2-1913 30 Apr 2000

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d. Sand boils. ( 1) Description. A sand boil is the rupture of the top foundation stratum landward of a levee caused by excess hydrostatic head in the substratum. Even when a levee is properly constructed and of such mass to resist the destructive action of floodwater, water may seep through a sand or gravel stratum under the levee and break through the ground surface on the lands ide in the form of bubbling springs. When such eruptions occur, a stream of water bursts through the ground surface, carrying with it a volume of sand or silt which is distributed around the hole. A sand boil may eventually discharge relatively clear water, or the discharge may contain quantities of sand and silt, depending upon the magnitude of pressure and the size of the boil. They usually occur within 3.05 m to 91.4 m (10 to 300ft) from the landside toe of the levee, and in some instances have occurred up to 304.8 m (1,000 ft) away. (2) Destructive action. Sand boils can produce three distinctly different effects on a levee, depending upon the condition of flow under the levee.

F-18

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Figure F-9. Sealing top of manhole with wood EM 1110-2-1913 30 Apr 2000

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(a) Piping flow. Piping is the active erosion of subsurface material as a result of substratum pressure and concentration of seepage in the localized channels. The flow breaks out at the landside toe in the form of one or more large sand boils. Unless checked, this flow causes the development of a cavern under the levee, resulting in the subsidence of the levee and possible overtopping. This case can be easily recognized by the slumping of the levee crown. (b) Non-piping flow. In this case, the water flows under pressure beneath the levee without following a defined path, as in the case above. This flow results in one or more boils outcropping at or near the landside toe. The flow from these boils tends to undercut and ravel the landside toe, resulting in sloughing

F-19EM 1110-2-1913 30 Apr 2000



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F-21EM 1110-2-1913

30 Apr 2000

F-22 

### o f the landward slope. Evidence of this type of failure is found in undercutting and ravelling at the landside toe. ( c) Saturating flow. In this case, numerous sma ll boils, many of which are scarcely noticeable, outcrop a t or near the landside toe. While no boil may appear to be dangerous in itself, the consequence of the group o f boils may cause flotation ( “quickness”) of the soil, thereby reducing the shearing strength of the material a t the toe, where maximum shearing stress occurs, to such an extent that failure of the slope through sliding may result. (3) Combating sand boils. All sand boils should be watched closely, especially those within 30.5 m ( 100 ft) of the

toe of the levee. All boils should be conspicuously marked with flagging so that patrols can locatethem without difficulty and observe changes in their condition. A sand boil which discharges clear waterin a steady flow is usually not dangerous to the safety of the levee. However, if the flow of water i ncreases and the sand boil begins to discharge material, corrective action should be undertaken immediately. Theaccepted method of treating sand boils is to construct a ring of sandbags around the boil, building up ahead of water within the ring sufficient to check the velocity of flow, thereby preventing further movement of sand and silt. See Figure F-12 for technique in ringing a boil. Actual conditions at each sand boil will determinethe exact dimensions of the ring. The diameter and height of the ring depend on the size of th e boil and the flow of water from it. In general, the following considerations should control: (1) the bas e width of the sandbag section should be no less than 1 1/2 time s the contemplated height; (2) encompass weak s oils near the boil within the ring of sandbags, thereby preventing a potential failure later; and (3) the ring s hould be of sufficient size to permit sacking operations to keep ahead of the flow of water. The height of the ring should only be that necessary to stop movement of soil, and not as high as to completely eliminate seepage. The practice of carrying the ring to the river elevation is not necessary and may be dangerous in high stages. If seep age flow is completely stopped, a new boil will likely develop beyond the ring; this boil c ould then sudd

enly erupt and cause considerable damage. Where many boils are found to exist in a given area, a r ing levee of sandbags should be constructed around the entire area and, if necessary, water should be pumped into the area to provide sufficient weight to counterbalance the upward pressure.

e . Erosion . Erosion of the riverside slope is one of the most severe problems which will be encountered during a floo d fight. Emergency operations to control erosion have been presented earlier under “Slop e Protection.” f. Storm and sanitary sewers

. ( 1) Prob lems. Existing sewers in the protected area may cause problems because of seepage into the lines, leakage through block ed outlets to the river, manhole pumps not spread throughout the sewer system, andold or abandoned sewer locations which were not found during preflood preparations. Any of thes e conditions can cause high pressures in parts of the sewer system and lead to the collapse of lines at wea k points and blowing off of manhole covers. ( 2) Solutions. During the flood fight, continued surveillance of possible sewer problems is necessary. I f the water level in a manhole approaches the top, additional pumps in manholes may alleviate the problem. Insan itary sewers, additional pumping may be required at various locations in the system to provid e c ontinued service to the homes in the protected area. When pumps are not available, manholes may have to beringed with sandbags or by some other method which allows the water to head up above the top of the manhole. To eliminate the problem of disposing of this leakage from manholes the ring dike would hav e t o be raised above the river water surface elevation. This creates high pressures on the sewer and should not b e done. As with sand boils, it is best to ring the manhole part way to reduce the head and dispose of what l eakage occurs. Directly

weighing down manhole covers with sandbags or other-items is not recommendedL"ANOSIOE

NOTE Bottom to**b~** no less than Tie into levee if boil is near toe

PLAN

Figure F-12. Ringing sand boils El-EVATION EM 1110-2-1913 30 Apr 2000

RIVERSIDE

SECTIONAL ELEVATION

NOTE• En!ire base to· be cleared of debris and scarified. Loos·e earth to be used belw«n all socks. All joints to be staggered.

where high heads are possible. A 30-kPa (10-ft) head on a manhole cover 0.61 m (2ft) in diameter would exert a force of9.16 kN (2,060 lb-force). Thus, a counterweight of more than a ton would have to be placed directly on the cover.

F-23EM 1110-2-1913

30 Apr 2000

F-24 

### g. Slope stability on weak foundations. In areas that have very weak foundation soils it may not be possible to construct full height flood barriers in preferred locations because of inadequate slope stability. H owever, if flood wat

ers are slow to rise and fall, it is possible to use the rising floodwater as a restraining l oad on the riverside slope to meet stability criteria. This is usually used for closure structures or for staged construct ion

where the flood barrier is only constructed after the river reaches an established level. Thi s procedure woul d also require that the flood barrier be removed before the river went down below th e established level. h . Causes of levee failures . In addition to the problems covered above, the following conditions could contribute to failure: ( 1) Joining of a levee to a solid w all, such as concrete or piling. Flood barriers consisting of sandbags great er than 0.91 m (3 ft) in height and joining a solid wall have performed poorly in the past due to excessive underseepage and instability of the sandbag prism. (2) Structures projecting from the riverside of levee. (3) A utility line crossing or a drain pipe through the fill. (4) Tops of stoplogs on roads or railroad tracks at a lower elevation than the levee. ( 5) Joining a sandbag barrier to a levee. Seepage problems at the junctur e with the levee fill have caused very poor performance.EM 1110-2-1913 30 Apr 2000

G-1 

### Appendix G Use of Soil Cement for Levee Protection
G-1. Purpose The pur pose of this appendix is to provide guidance on the design and construction of soil cement slop e p rotection for levees and embankments. This includes soil cement, materials, mixture proportioning, design of slope protection, construction, quality control, inspection, and testing. G-2. General Considerations

a. Soil Cement . The American Concrete Institute defines soil cement as a mixture of soil and measured a mounts of portland cement and water compacted to a high density. Soil cement can be further defined as a m aterial produced by blending, compacting, and curing a mixture of soil/aggregate, portland cement , possibly admixtures including pozzolans, and water to form a hardened material with specific engineering properties. b. Appli cation

. Although riprap has historically been used for slope protection for levees, dams , c hannels, et c.,there are situations when suitable rock is not available within economical haul distances and soil cement slope protection may be the most economical and appropriate selection.

c. History. T he use of soil cement for slope protection has increased considerably over the pas t 30 years. The main focus of this effort has come from the U.S. Bureau of Reclamation (USBR) in th e construction o f dams. The first experimental use of soil-cement for slope protection was a test sectio n c onstructed by USBR at Bonny reservoir in eastern Colorado in 1951. Observation of the performance of this test section for the first 10-year period of service indicated excellent performance of the soil cement whi ch was subject to harsh wave action and repeated cycles of freezing and thawing. This lead to th e conclusionthat use of soil cement for slope protection was feasible based on both economical and service life considerations. d. Economi cs. The decision to use soil cement instead of riprap is primarily an economic one

. However, not every soil is suitable for producing soil cement for this application. Therefore, the designer must compare the availability of suitable soil for soil cement versus the availability of suitable rock fo r r iprap. The designer must prepare a cost an alysis in arriving at a decision. Factors that must be considered f or

soil cement include cost of cement, location of suitable soil, special processing requirements if needed, h aul distance, dimensions and configuration of the slope protection and mixing and placement methods. For ri prap, considerations include cost and availability of rock, size and availability of rock, haul distance , spe cialprocessing requirements, configuration of placement and placement effort. Cost estimates of th e alternative methods provide the basis for the economic analysis. G-3. Materials

a. Soils

. In general most soils of medium to low plasticity (Plasticity Index (PI) equal to or less than 12) can be usedfor soil cement. However for levee protection, better quality granular materials are r ecommended since the soil cement may be subjected to repeated cycles of wetting-drying, freezing-thawing andwave action. It is recommended that the soil should not contain any material retained on a 2-in

. ( 50.8 mm ) sieve, nor more than 45 percent retained on a No. 4 (4.75-mm) sieve, nor more than 35 percent or less than 5 percent passing the No. 200 (0.075-mm) sieve. The PI should be equal to or less than 12 andEM 1110-2-1913

30 Apr 2000

G-2 

### the organics content should be less than 2 percent. It should be noted that clay balls (nodules of clay and silt mixedwithsand materials) can form when the PI is as low as 8. Clay balls can be detrimental when soi l cement is exposed to weathering and the clay tends to wash out leaving voids in the soil cement structure. C lay balls greater than 25.4mm (1-in.) should be removed and the minus 25.4-mm (1-in.) clay ball content s hould be limited to 10 percent. For economic reas ons, the soil should be obtained from a borrow area close tothe construction site. Samples from borrow sources must be evaluated for gradation and PI. If in-situ soils are not suitable it may be necessary to blend materials from several borrow sources. b. Cement. Portland cements meeting specifications of ASTM C 150 are suitable. Generally, Type I i s used for soil cement. However, soil cement can be subject to sulfate attack and it is the lime in the cement thatis i nvolved in the reaction. Therefore, sulfate bearing soils or water should be avoided. There is n o definitive test to determine the threshold sulfate content at which a soil is deemed to be potentially reactive however experience has shown that soils with a sulfate content as low as low as 0.3 percent have developed reactions. If expo sure to sulfates is not avoidable, Type II cement is recommended. Use of fly ash as a replacement

for portland cement is not recommended in that experience has indicated that fly ash reduces early age compressive strength and durability when used in soil cement.

c. W ater. Most water is acc eptable for soil-cement. The primary requirement is that water should be free f rom substances deleterious to hardening of the soil cement. Specifically, water should be free fro m objectionablequantities of organic matter, alkali, salts, and other impurities. Presence of soluble sulfates sho uld be of concern. Seawater has been used satisfactorily. The presence of chlorides in seawater may in creaseearly strength. The quality of water for soil cement should be similar to that used for mixin g concrete. Guidance on water quality may be found in Corps of Engineers CRD-C 400. G-4. Proportioning Soil Cement Mixtures

a. G eneral. One of the key factors that acc ounts for the successful use of soil cement is careful predet ermination of engineering control factors in the laboratory and their application during construction. The c omposition of soils varies considerably and t hese variations affect the manner in which the soils react when c ombined with portland cement and water. The way a given soil reacts with cement is determined by simple l aboratory tests conducted on m ixtures of cement, soil, and water. These tests determine three fundamental r equirements for soil cement: t he minimum cement content needed to harden the soil adequately; the proper m oisture content; and t

he density to which the soil cement must be compacted. Generally, the procedure to dete rminethe mixture cement content consists of the following steps: soil classification test to determin e a n appropriate soil type; moisture density tests at a selected initial cement content to determine target density and water content values; durability tests at a range of cement content values including the initial cement c on tent; unconfined compressive strength tests; and selection of final cement content based on test results. b. S election of soils. The d esign of a soil cement mixture begins with selection of a suitable soil type, The object ive is to select a soil that can be stabilized with the minimum cement content and that will b e s uitably durable for the range of service condition s to which it will be subjected. Guidance on specifications forgradin g and plasticity of soils were given previously. Generally, soil cement made with granula r materials requires less cement than soil cement made with sands and fine grained soils. The latter materials are als o less durable. If the soils available in the immediate area of construction do not meet desire d s pecifications it may be necessary to blend s everal soil types to obtain the desired characteristics. However, before blendin g is specified, the increased costs of processing and monitoring should be compared to th e i ncreased cost of additional cement required for the natural material. Occasionally the designer may encounte rsoils that are unreactive or are marginally reactive requiring apparently excessive amounts of cement

. Often such soils contain acidic organic materials that affect the reaction.EM 1110-2-1913 30 Apr 2000

G-3 

### c. Cement content general. A series of laboratory tests must be conducted to determine cement content. Inherentin th ese tests is also the determination of design soil density and water content. If the project i s l arge and more than one candidate soil is available , it may be appropriate to conduct the entire series of tests o n each soil to determine the most economical mixture for the project. Also, if several borrow areas having significantlydifferent soils are involved it may be necessary to conduct laboratory tests on soil from each b orrow a rea to determine the appropriate mixture for each soil. The tests involved in this process include: moisturedensity tests (ASTM D 558) to determine initial design density and moisture content based on a selected initial cement content and durability tests (ASTM D 559 and D560) to determine resistance to repeatedcyc les of wetting and drying and freezing and thawing which might be expected under natural climatic changes. Compressive strength tests (ASTM D 1632 and D 1633) should be conducted o n l aboratory prepared specimens. Tests are conducted at several cement content values and the final cement content is that which produces the required durability and strength at the lowest practical cement content. S trength and rate of strength gain are important factors in performa nce of the soil cement. Adequate strength is required to resist forces of wave action and uplift pressures. d. Moisture density tests. Moisture density tests are conducted to determine values of density and water c ontent for molding soil cement durability samples and for field control of compaction during construction. The ceme nt content for moisture density tests is selected based on soil classification. Soils should b e c lassified following procedures indicated in ASTM D 2487, Standard Test Method of Classification of Soils f or Engineering Purposes. Initial cement contents for different soil classifications are indicated in Table G-1. Theappropriate value of cement content for moisture-density tests may be selected from this table. Only coarse grained soil symbols are shown as these are the soil types preferred for soil cement for slop e p rotection. Represen

tative soil samples should be collected and moisture density tests conducted following pr ocedures indicated in ASTM D 558, Standard Test Methods for Moisture Density Relations of Soi l C ement Mixtures. Results of the tests are plotted as shown in Figure G-1 from which values of dry density a nd moisture cont

ent are selected for molding durability specimens. The dry density may be the maximum or a percentage of the maximum density indicated on the plot. Past experience has indicated that a minimum densityof 98 percent of the maximum ASTM D 558 density is adequate. The water content is the valu e associatedwith the selected density. The water content at maximum dry density is termed the “Optimum Water Content” (OWC).

Table G-1 Initial Cement Content for Moisture Density Tests Soil Classification Initial Cement Content (ASTM D 2487) (percent dry weight of soil) GW, GP SW, SP 7 GM, SM 8 GC, SC 9 SP 11



### e. D urability tests. Two types of durability tests are conducted: ASTM D 559, Standard Test Methods f or Wetting and Drying of Compa cted Soil Cement Mixtures and ASTM D 560, Standard Test Methods of F reezing and Thawing of C ompacted Soil Cement Mixtures. These tests were designed to reproduce in the l aboratory the moisture and temperature changes expected under field conditions. These tests measure the effect of internal volume changes produced by changes in moisture and temperature. From these tests the m inimum cement content required to p roduce a structural material that will resist volume changes produced by chan ges in moisture and temperature can be determined. Wet dry tests should be conducted in al l geographicareas. Freeze-thaw tests should be conducted in all areas that experience at least one cycle of f reezing and thawing per year since levee protection is expected to be subjected to this condition over a longEM 1110-2-1913 30 Apr 2000**~** 

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period of time. Ifthere is absolutely no expectancy of freeze thaw cycles in the geographic area this test may be omitted. Each type oftest consists of twelve two-day cycles ofwetting/drying or freezing/thawing as appropriate and thus requires 24 days to complete. For each type of test, duplicate specimens of soil cement should be prepared at cement contents equal to the cement content used for the moisture density test and at cement contents 2 percent above and 2 percent below that used for the moisture density test. For example, if the cement content for moisture density tests is 7 percent, samples for durability tests should be molded at 5, 7, and 9 percent cement. Ideally, a moisturedensity test should be conducted for each cement content to determine maximum density and optimum moisture water content for that particular design mixture since these values vary with cement content. If this is not possible the density and moisture content determined from the initial tests may be used. After each cycle (of either the wet-dry or freeze-thaw) the specimen is scrubbed with a wire brush to remove soil cement that becomes loosened or unbonded as a result of exposure to the test environment. After the twelve cycles are completed, the total weight loss is calculated and this value is compared to established criteria. The weight loss criteria are shown in Table G-2. Assuming both tests are conducted, specimens must meet both criteria. If specimens do not meet both criteria, adjustments must be made in the soil gradation and/or cement content based on engineering judgment and at least one set of tests should be rerun. Adjustments may include blending of aggregate to the soil and/or increasing the cement content.

Table G-2 Durability Test Weight Loss Criteria Type of Durability Test Wet Dry (ASTM D 558) Freeze Thaw (ASTM D 559)

G-4 Maximum Weight Loss After 12 Cycles (percent) 6 8EM 1110-2-1913 30 Apr 2000

G-5 

### f. U nconfined compressive strength tests. The next step is to conduct unconfined compressive strength tests (ASTM D 1632 Making and Curing Soil Cement Compression and Flexure Test Specimens in th e L aboratory, and ASTM D 1633 Compressive Strength of Molded Soil Cement Cylinders). Strength of the s oil cement is important in slope protection to provide resistance to wave action and uplift pressures. In fact, s trength may be the determining factor in arriving at the final design cement content. Experience has shown thatofte n the cement content of specimens meeting compressive strength criteria is higher than that ne cessaryto meet durability requirements. The cement content for specimens for initial compressiv e s trength tests will be the minimum cement content of the specimens that met durability criteria. The water c ontent and dry density will be that used to mold durability specimens. Duplicate specimens should be prepared and tested as indicated according to the ASTM procedures previously indicated. Minimu m c ompressive strength criteria are indicated in Table G-3. If strengt hs of specimens tested at the initial cement c ontent do not m

eet minimum criteria, then the cement content should be increased in two percentage point increments and compressive strength tests rerun until criteria are met or it is determined that another mi x design approach mu st be undertaken. If time constraints do not permit conduct of unconfined compressive stren gthtests until the durability tests have been completed, it may be necessary to conduct these test s si multaneously. If this is necessary, the unconfined compressive strength tests should be conducted o n specimens prepared at all of the cement contents used in the durability tests. This approach obviousl y requires that many more specimens be prepared and tested however the savings in time may be more economical than conducting the tests in sequence.

Table G-3 Unconfined Compressive Strength Criteria (ASTM D 1633) Cure Time (days) Minimum Compressive Strength, kPa (psi) 7 4138 (600) 28 6034 (875)



### g. Final cement content. The final cement content is the minimum cement content used in specimens that met or exceeded both the durability and compressive strength criteria. Some designers have added one or t wo percentage points to t

his cement content to account for variability in the field cement content where the p roposed method of construction ismixed in place. Where central plant mix procedures are used control of cement content is generally accurate. G-5. Design of Slope Protection

a. General

considerations. Design of slope protection with soil cement is somewhat similar to design withriprap i n that protection must be provided against erosional forces from wave action and stream c urrents. Soil cement slope prot ection can be provided in two configurations: stair step or plating. In stair s tep slope protection the soil cement is usually placed in successive horizontal layers adjacent to the slope. This method is preferred for slopes exposed to moderate to severe wave action or debris carrying, rapidly flowing wa ter. The plating method consists of placing one or more layers of soil cement parallel to, i.e. , directly on, the slope. This method is used where less severe exposure is expected. b. Stairstep me thod. The stair step method consists of constructing successive horizontal lifts o f c ompacted soil cement up

the slope to the desired height of protection (Figure G-2). Each successive lift is set back by an amount equal to the compacted lift thickness times the cotangent of the slope which results i n a stair step pa

ttern approximately parallel to the embankment slope. Layer thickness can be from 152.4 t o 304.8 mm (6 to 12 in.) depending on the typeof compaction equipment used. Historically, stair step cons truction has been accomplished with 152.4 mm (6 in.) compacted lifts. However, thicker lifts require lessEM 1110-2-1913 30 Apr 2000



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construction effort and result in fewer bond surfaces. The disadvantage of thicker lifts is more loss of soil cement at the exposed edge during construction and additional effort is required to obtain desired density throughout the lift. The width of the layer also is a function of type and size of construction equipment. Experience has shown that a layer width of about 2.4 m (8 ft) is generally most convenient. Since stair step protection is indicated for more severe environmental conditions, a thicker covering over the slope is generally specified. Experience has indicated that the total thickness of soil cement measured perpendicular to the slope should be 0.61 to 0.92 m (2 to 3 ft). The relationships between slope, facing thickness, layer thickness and horizontal layer width are shown in Figure G-3.



### c. Plating method. The plating method consists oflifts placed parallel to, i.e., directly on, the slope and is used in areas where a thinner facing is required. Generally two 152.4 mm (6-in.) lifts or one 203.2-mm (8-in.) lift are used for plating. One of the primary considerations in plating protection is providing resistance to high flow especially with debris. To date there are no definitive design criteria to determine lift thickness based on abrasion, however, since the plating method is applicable for areas subjected to less harsh environments, experience has shown 304.8 mm (12 in.) of protection is adequate. In the plating method, lifts can be constructed so that the resulting construction joints are either parallel or perpendicular to the flow of water. If placement and compaction of the soil cement are up and down the slope, the construction joint will be perpendicular to the water flow. If placement and compaction are along the slope, the construction joints will be parallel to the flow of water. For the plating method of construction, the slope should be 3H:IV or flatter in order to properly spread and compact the soil cement. Construction on steeper slopes may be accomplished if special compaction equipment is used. 

### d. Freeboard and wave runup. Freeboard is the vertical distance from the top of the levee to the water surface. The freeboard should be sufficient to prevent waves from overtopping the levee or damaging the crest. Slope protection should be provided in the freeboard area to prevent erosion. When a wave contacts the face of the levee it will run up the slope. Wave run up is the vertical height above the still-water level to which the uprush from a wave will rise on a structure. It is not the distance measured along the inclined surface. To calculate the wave run up for soil cement slope protection, the wave run up value based on riprap protection is first calculated and this value is multiplied by a factor based on the type and condition of the soil cement slope protection. For calculation of wave run up for riprap, designers should consult the following references: EM 1110-2-1614, Design of Coastal Revetments, Seawall, and Bulkheads, dated 30 June 1995; and the Automated Coastal Engineering System (ACES) computer program. For stair step construction with vertical faces on the layers the run up factor 1.2. Where the faces have become rounded due to weathering and erosion the run up factor is 1.3. For plating slope protection the run up factor is 1.4.

G-60:: ILl >- j ""- 0 0.. 0EE- < A ILl 0:: ::J 1'/) < ILl ::::;;**~** ""- ci ILl >- j ""- 0 :r:EA 

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Figure G-3. Relationship of slope, facing thickness, layer thickness, and horizontal layer width EM 1110-2-1913 30 Apr 2000



### e. Transitions. Transitions between soil cement and earth or other structures should be addressed. Tiebacks similar to riprap emplacements can be designed to avoid flanking of the structure. An alternative is to use a riprap section at either end of the soil cement structure. Where soil cement joins other structures and compaction is difficult it may be appropriate to use lean concrete. 

## f Drainage and seepage. Although no distress to soil cement slope protection due to rapid drawdown has been reported and the current thinking is that drainage is not required unless severe drawn down is anticipated, the designer should be aware of the preventative measures can be used. Three concepts are presented. One is design of the levee so that the least permeable zone is adjacent to the soil cement. This will provide protection against build up of excess pore water pressure. A second method is to determine that the weight of the facing is sufficient to resist uplift pressures. Here, there may be some pore pressure relief through shrinkage cracks in the soil cement. Obviously, some estimate must be made of the gross hydraulic conductivity of the soil cement. A third measure is to provide deliberate drainage conduits through the soil cement. This approach was used by the Bureau of Reclamation at Merrit Dam. Three rows of 76.2- to G-7EM 1110-2-1913

30 Apr 2000

G-8 

### 127-mm- (3- to 5-in.-) diameter weep holes were drilled into the facing after construction and include d 118 holes on 3.05 m (10 ft) centers. In such arrangements, a filter is placed in the area of weep hole before soil cement construction. G-6. Construction

a. G eneral . There are two general methods in common u se for constructing soil-cement: mixed-in-place and central mix plant. Regardless of the equipment and methods used the goal is to obtain thoroughly mixed andadequ ately compacted and cured soil-cement. The central mix method involves mixing of a borro w material with cement and water, at a centrally located pla nt. The mixture is then transported to the site. The mixed -in-placemethod involves mixing of cement and water with the in-place soil at the site, and i s infrequently used for embankment soil cement applications. The most common method of soil-cement construction for bank protection is central mix plant. For soil-- cement us ed as bank protection, particularly where banks experience higher flow velocity forces, adequate strength and durability, and consistent quality, are primary requirements. It is harder to achieve thes e objectives using mixed-in-place construction than central mix plant. Two methods are used for placement and compaction of soil cement for embankments: stair step or pl ating. Design for these methods was discussed earlier in this document. The stair step method is th e predominant method used, although con struction using both methods is discussed in the subsequent sections on spreading and compaction. Soil cement should not be mixed or placed when the soil or subgra de is frozen or when the air temperature is below 9 E 

### C (45 E 

### F). Specifications may allow soil cement construction to proceed if the air temperature is at least 4 E 

### C (40 E 

### F) and rising . Hot weather poses a few problems for soil cement construction, requiring sometimes additional moisture application to the materials, faster placement and compaction operations, and additional curing effort. b. Centralmix plant construction. There are two basic types of central mix plants: pugmill mixer s either continuous or batch type, and rotary drum mixers (also a batch type of mixer). The uniformity of soil cement produced by these plant types is generally roughly equivalent, provided they have been properly calibrated. Continuous mix pugmill plants have higher production rates, while batch plants are often easier to cali brate, and require less frequent calibration. Batch-type pugmill plants have been used, bu t infrequently. Production rates between 76.4 and 152. 9 m (100 and 200 cu yd/hr) are common for stair-step 3 

### soil ce ment construction. The basic steps of central mix plant construction of soil cement are: subgrad e pre paration, borrow materials, mixing, transporting, spreading, compacting, bonding lifts, finishing , construction joints, and curing and protection. (1) Subgrade preparation . A firm su bgrade is necessary to compact the overlying layers of soil cement to the r equired density. The subgrade is prepared by removing and replacing, or stabilizing, soft or we t areas, removing deleterious materia ls, and grading and compaction to construction plans and specifications. Most overly wet subgrade areas can be corrected by aerating and recompacting, or some type of chemical stabilization. Dry subgrades are surface moistened immediately prior to soil-cement placement. (2) Borrow m aterials . Soil borrow sources are usually near the construction site and may consis t partially or wholly of excavated bed and/or bank material. Native borrow materials are naturally variable incomposit ion. Excavation, blending and stockpiling methods for borrow material should be selected to minimize this variation, a

nd produce as consistent a material as possible. Horizontally stratified soil layers can be blended by deep excavation using full face cuts, insuring all layers are cut with each equipment pass.EM 1110-2-1913 30 Apr 2000

G-9 

### If m aterials vary laterally across the borrow areas, loads from different locations should be blended in a systematicfashion. Further blending can also be done as materials are brought to the plant stockpile area. Alternat ing the loads from different parts of the plant stockpiles, or even using a front-end loader to take a vertical cut of the stockpiles, also helps blend materials as they are fed to the mixing plant. Screening the borrow material through a 25-mm (1-in.) to 38.1-mm (1-1/2-in.) mesh at the pit or at the plantcan he lp remove oversize clay balls and other oversize materials. Selective excavation may b e necessary to avoid excessive clay balls or clay content in the borrow area. Stockpiles should be separated from each other and all plant equipment by at least 15.2 m (50 ft). Where the soil contains coarse aggregate, stockpiling is done in layers to minimize segregation. (3) Mixing

. Central mixing plants with rated capacities of 227 to 907 metric tons (250 to 1,000 tons) per hour (about 95.56 to 382.3 m (125 to 500 cu yd)) are used commonly. Special blending requirements 3 

### may require several stockpiles and s eparate storage feeder bins. Prior to mixing and placing, it is necessary to measure the quantities and proportions of material supplied by the plant. The plant should be accurately calibrated. (a) Pug millmixers . The most common continuous mixing plants contain a twin shaft pugmill

. Figure G-4 shows a diagram of a typical pugmill central mix pla nt. USBR recommends a twin-shaft pugmill with a rated capacity of at least 152.9 m (200 cu yd)/hr. A pugmill mixing chamber contains twin shafts 3 

### rotati ngin opposite directions, with paddles (see Figure G-5) that force mix the soil cement and move i t through the chamber by the pitch of the paddles. Material feeds (by adjusting gate openings and belt speed) and pugmill feature s (such as pugmill tilt and paddle pitch) may be adjusted to optimize the mixing actions and production. Thoroughness of blending is partly determined by the length of mixing time. A mixing time of 30 s ec is commonly specified, although shorter times have also been shown to be adequate, dependin g on the mixer efficiency. Batch type pugmill mixers, where the materials a re delivered to a pugmill mixer in a discrete batch rather thanas a continuous ribbon of material, can provide effective mixing of soil cement, but are seldom used, largely due to lower production capacity and lack of availability. (b) Rotary drum mixers

. Although rotary drum (also called tilt drum) mixers are sometimes used, they are generally lower in production capacity than pugmill mixers. These plants are typically converted central mix concrete p lants, and function in the same manner. Mixing times for these plants are typically abou t 60 sec. (4) Transporting . Haul trucks can be of the end or bottom dump variety, although many types are used. Where condi tions are extremely hot and/or windy or where sudden showers are a possibility, soil cement should be protected by using canvas covers on haul vehicles. Equipment should be clean. The elapsed time betw een mixing and compacting should be kept to a minimum. Sixty minutes is usually the maximum

. Therefore, most specifications require haul times to be kept below a maximum of thirty minutes. In s tair step construction, temporary ramps are constructed at intervals along the bank to enable trucks to reach the layer to be pla

ced. These temporary ramps should have a minimum 0.457 m (18-in.) thickness of material to p rotect the edge of the previous lift from truck traffic. There is also a requirement, where streambeds are dry, for ramps to be spaced to allow egress from the channel in case of a flood. These are constructed at 45 E 

### angles, with a minimum of 0.61 m (2 ft) of cover over the soil cement, and spaced about 91.4 to 121.9 m (300 to 400 ft) apart.EM 1110-2-1913 30 Apr 2000



### CEMENT STORAGE SILO

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Figure G-4. Typical pug mill central plant

Figure G-5. Mixing paddles of a twin-shaft, continuousFigure G-6 shows a typical step-construction sequence. Frequently time and cost savings have been realized by using conveyor systems to deliver the soil cement to the spreader. This removes the necessity for ramp construction and truck maneuvering and provides a cleaner end product. Narrower layers and plating applications can also be placed using a conveyor system. The soil cement can be delivered from above or below directly to a spreader box. (5) 

### Spreading. Soil cement must be spread in a manner that will provide a compacted layer of uniform thickness and density, conforming to the design grade and cross section.
flow central mixing plant (a) 

### Stair step method. There are a wide variety of spreading devices and methods for stair step construction. One of the most common is the spreader box attached to a dozer or grader. An
G-10PNEUMATIC TIRED ROLLER SHEEPSFOOT ROLLER

Figure G-6. Typical construction sequence SPREADER EM 1110-2-1913 30 Apr 2000

alternate method is to place material in windrows to be spread by a grader. Care must be taken with the windrow operation not to over manipulate the material which may cause separation and premature drying. Layers are spread 15 to 30 percent greater than the required compacted thickness. Experimentation may be necessary to determine the appropriate spread thickness since different combinations of equipment and soil type may produce different amounts of precompaction. Spreading may also be done with asphalt-type or RCC pavers. Some of these pavers are equipped with one or more tamping bars which provide some initial compaction. Placement of stair-step sections may need to be limited to a maximum of 1.22 m (4ft) height in a single shift to avoid instability producing bulging in the outer face from the surcharge weight of material and equipment above. (b) Plating method. A variety of methods may be used for spreading of soil cement for plating applications. On relatively level surfaces, the methods are the same as for stair step placement. Plating construction on steeper slopes requires different procedures than stair step construction. Dozers are commonly used to spread soil cement on steeper slopes. USBR has reported best results in terms of producing uniform thickness and minimum waste when soil cement was spread from the top to the bottom, rather than from bottom to top. Whatever method is used, careful attention needs to be paid to achieving uniform thickness. (6) Compaction. Minimum compaction to be achieved in the field is normally specified as a percentage of maximum density determined by ASTM D 558 or ASTM D 1557, typically requiring 98 percent of maximum density. Moisture content of the soil cement mixture must be controlled within tight limits to ensure consistent optimum conditions for compaction. USBR practice has been to place soil cement at water contents at or slightly dry of optimum. This can help avoid excessively wet mixes that may cause traffic and compaction difficulties, as well as lift distortion and increased cracking due to shrinkage. Compaction should begin as soon as possible and be completed within about one hour after initial mixing. No section of soil cement should be left unworked for longer than 30 min. Climatic conditions at some sites, such as very cool, humid weather, may allow relaxation of this guidance. Moisture loss by evaporation during hot weather compaction should be replaced by light applications of water. Compaction is done by various types of rollers. For fine grained soils, a sheepsfoot roller is generally used for initial compaction, followed by a pneumatic-tire roller for final compaction. USBR practice has often been to compact the lower portion of the lift with a towed sheepsfoot roller, using the vibratory steel-wheeled roller for the upper portion of the lift. Some problems have been encountered with vibratory roller compactors when used for finer grained materials. Vibratory rollers may create fine transverse cracks in the soil cement surface, requiring a G-11EM 1110-2-1913 30 Apr 2000

rubber-tired roller for final compaction to close most of the cracks. Compacting soil cement at or above optimum moisture can produce rutting from pneumatic tire rolling. For coarse grained soils, vibratory steelwheeled or heavy pneumatic rollers are generally used. Compacted layer thickness is typically from 152.4 to 228.6 mm (6 in. to 9 in.), although greater thicknesses of coarse grained soils can be compacted with heavy equipment designed for thicker lifts. The specified minimum density must be achieved throughout the lift thickness, regardless of the lift thickness and compaction equipment used. Compactor weight, and vibration amplitude and frequency must be adjusted during construction to obtain the best compaction. Test sections are a valuable aid in determining the optimum compaction equipment characteristics and procedures. (a) 

### Stair step method. Compaction of the outer edge of the layer is usually not necessary from the standpoint of structural integrity. However, uniform edges provide a better appearance and allow for easier emergency egress from streambeds. Sharp edges reduce wave runup but increase roughness. Edge compaction can be accomplished by hand tampers or through the use of some type of edge support during compaction. (b) 

### Plating method. Compaction is done with various roller types. Construction on near horizontal surfaces is similar to layered construction. Compaction on steeper side-slopes requires different procedures. A rolling deadman (Figure G- 7) has been used to winch the roller up and down slope. Adequate compaction has been achieved using bulldozers, although their use is not recommended. Multiple overlapping passes are usually required. Surface tearing can be minimized by using cut grousers or street pads. Compaction from bottom to top has been most successful.

Figure G-7. "Deadman" pulling vibratory sheepsfoot roller up the slope the layer which would reduce bond. (7) 

### Bonding lifts. The bond between soil cement layers is generally weak. No definite criteria is available on the most effective methods ofbonding between layers; however, bonding may be considered if layer separation is anticipated. Layer separation may be a concern from strong wave action, or at the upper lift of some sections, where there is little weight above the lift to mobilize shear resistance. The most significant factor in bond strength is time delay between lifts. The shorter the time between lifts the better the bond. Long placements may be broken up into shorter segments, enabling subsequent lifts to be placed more rapidly. Moist curing increases the bond strength but excess water tends to decrease it. Most specifications require temporarily exposed surfaces to be kept moist and clean. Care must be taken to avoid tracking clay or other materials onto

Power brooms should be used for lift surface cleaning to remove loose and unhanded material. USBR studies have suggested that roughening the lift surface with steel power brooming does not significantly contribute to increased bond strength. Brooming is not permitted prior to 1 hr after compaction to allow adequate set of the soil cement. Both dry cement and cement slurry lift bonding have been used and evaluated in USBR test sections, with encouraging results. A slurry mix should have a water/cement ratio of about 0. 70 to 0.80 and an application
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G-13 

### the latter rate. Dry cement applications have a disadvantage of being susceptible to wind, while cement slurry i s susceptible to rapid drying. Whichever method may be used, the material should be applied immediately before placement of the next lift. (8) Fi nishing. As compaction nears completion the entire layer should be shaped to specified lines , grades, and cros s sections. Edge shaping can be done with a modified blade or a curved attachment on the rol ler. The lift may require scarification to take out imprints left by equipment or to remove thin surfac e compactionplanes. Scarification can be done with a variety of spring tooth or spike toothed harrows, o r similarequipment. Soils containing gravel may not require scarification. Final surface compactio n fo llowingscarification is performed with a steel-wheeled roller in nonvibratory mode, or a rubber-tire d r oller. A smooth “table top” finish is not requi red and may be detrimental to lift joint shear strength. Wheel marks are acceptable, although they may make lift joint cleanup more difficult The edges on stair-stepped s oil cement applications have been finished by cutting back the uncompacted edges, by u sing special rounded attachments on compaction equipment, and by leaving sacrificial uncompacted edge material in place to be eroded later. (9) Construction joints . Construction joints a re required at the completion of each day’s work or when workmust be s topped for time periods longer than allowed for placement and compaction of fresh soi l c ement. They are made by cutting back into the finished work to proper crown and grade. The joint must b e vertical, full depth, and transverse to the layer direction and is usually done with the toe of a grader blade orbulldoz er blade. Care must be taken that no debris is present on the joint edge, and that new material placedagains t the joint adheres to the previous work. Joints should be staggered to inhibit crackin g throughout the structure (10) Curing and protection. Proper curing is essential, because strength gain and durability is dependent upon time, temperature and the presence of moisture. All permanently exposed surfaces should be mois t c ured for a period of seven days. Traffic should be kept off the soil cement during the curing period. Light traffic is sometimes allowed on the completed soil cement, provided the curing is not disrupted. Soilcement must be protected from freezing during the curing period. Insulation blankets, straw, or a s oil cover are commonly used. Light rainfall should not interrupt construction. However, a heavy rain prior t o compaction ca

n be detrimental. For mixed-in-place operations, if rain falls during the cement spreading operation, the cement already spread must be quickly mixed with the soil, and compaction must procee d immediately. After soil cement has been compacted, rain will seldom have detrimental effects. (a) M oist curing. Water curing may be done with fog spraying, or with weighted and secured plastic sheetingif wind is not a problem. Wet burlap can also be used if a moist condition can be maintained. A minimum of 152.4 mm (6 in.) of moist earth can be specified as an alternative. The earth cover may also inhibit freezing should colder temperatures be expected. (b) B ituminous membrane curing. Membrane curing using some types of bituminous mater ial (generally an emulsified a sphalt) can be used as an option to water curing where no succeeding layers will come i n contactwith the membrane. However, the black color may be objectionable to owners. Bituminou s membrane curing should not be used for levees, ponds or reservoirs which will have water frequently i n c onta ct with the membrane, without evaluation of environmental effects of the bituminous membrane. An application rate of 0.68 to 1.4 R

### /m (0.15 to 0.30 gal/s q yd) is required. The soil cement should be moistened 2 

### just prior to the membrane application. Sand can be spread over the bituminous membrane curing if light traffic is necessary, to prevent tracking of the bituminous material.EM 111 0-2-1913 30 Apr 2000

c. Mixed-in-place construction. In-place mixing is generally not used nor recommended for multi -layer construction. Plating type embankment applications are possible with the mixed-in-place method of soil cement, although again are not recommended. The basic steps in mixed-in-place construction are: soil preparation, cement addition, pulverization and mixing, compaction, finishing, curing, and protection. Following mixing, the construction techniques are essentially identical to central plant soil cement and are not further discussed under the mixed-in-place method. Although windrow type mobile pugmill mixers are used for pavement mixed-in-place construction, they are seldom used for embankment applications. Mix-inplace operations are generally performed using transverse single or multiple-shaft rotary mixers (see Figure G-8). In-place strength of the soil cement using mixed-in-place construction may be only 60 to 80 percent of the laboratory values, due partly to less efficient mixing compared to central mixing. Adding one to two percent cement is common practice to compensate for the higher variation in strength using mixed-in-place construction. (1) Soil preparation and pulverization. The soil is prepared by removing and replacing, or stabilizing, soft or wet areas, removing deleterious materials such as stumps, large roots, organic soils, and aggregate greater than 76.2 mm (3 in.) in size, and grading to the approximate final design profile. Most overly wet areas can be corrected by aerating and recompacting, or some type of chemical stabilization. Proper moisture content is essential for unimpeded construction traffic and for satisfactory pulverization and mixing. Dry soils may be disced and wetted by spray trucks until moisture content is near optimum for the soil cement. A moisture content near optimum may be Figure G-8. Transverse single-shaft rotary mixer necessary for pulverizing fine grained soils. Pulverization of soil prior to cementitious materials spreading is generally necessary to insure uniform cement mixing. Pulverization of soils with higher fines content or higher plasticity may be difficult without proper moisture control and proper equipment. (2) Cementitious materials application. Cementitious materials are distributed on the soil surface using a bulk mechanical spreader (see Figure G-9), or for smaller projects, by hand placing cement bags. Mechanical spreaders must be operated at uniform speed with a relatively constant level of cement in the hopper to produce a uniform spread of cement. Mechanical spreaders also require sufficient traction for proper distribution, sometimes requiring wetting and rolling the soil prior to spreading. Some spreaders are directly attached behind a bulk cement truck, where cement is pneumatically moved into the spreader hopper for distribution. PCA (1995) has convenient tables to convert the required cement content as a percentage by weight of oven-dry soil into a cement spread quantity in terms of weight of cement per square foot of soil surface. Cement spreading can be performed only when wind is absent and may require environmental permits. Although cement slurry spray applicators, including admixture capability, are available, they have not been widely used as yet. (3) Pulverization and mixing. Most soils must be pulverized prior to mixing operations, using the rotary mixers. For mixing, single-shaft mixers require at least two passes; one to mix the soil and cement, and the second to add water. Multiple-shaft mixers handle these functions in one pass. Agricultural equipment does not generally give adequate results. In-place mixing efficiency is generally poorer than central mixed soil cement.

G-14Figure G-9. Bulk mechanical spreader EM 111 0-2-1913 30 Apr 2000
(4) 

### Compaction, finishing, curing, and protection. These construction techniques for mixed-in-place construction are essentially identical to those for central plant soil cement. 

### G-7. Quality Control, Inspection, and Testing Adequate quality control and inspection procedures are important factors in successful soilcement construction. Construction control procedures for soil-cement are fairly standardized. The quality of the two basic operations (soil-cement mixing and actual construction) are insured through control of four basic factors: cement content, moisture content, compaction, and curing. These factors can be controlled easily by organizing the inspection steps into a routine that fits in with the sequence ofconstruction steps. These steps are slightly different for central-plant construction and mixed-inplace construction.



### a. Central-plant construction. The inspector checks on the following items. (1) 

### Construction site and equipment. Equipment must be clean, appropriate for the soil type, adjusted properly, and designed to preclude contamination introduction. Hauling vehicles must have protective covers where appropriate. The site should be set up to meet production and timing requirements and provide efficient traffic flow and proper separation distances for material stockpiles. (2) 

### Soil. Soil must match identification data given in the laboratory report. The inspector should check for uniformity of color, texture, and moisture. The soil should be monitored as it is stockpiled. Upon completion of the stockpile it is sampled and tested for acceptance. Gradation, specific gravity, and Atterberg limits should be tested regularly. (3) 

### Cement application. The amount of cement is specified either as a percentage of cement by weight of oven-dry soil material, or in pounds of cement per cubic foot of compact soil-cement. Pre-construction plant calibration and daily calibration checks insure an accurate mix. Different types of calibration procedures are applicable depending on the type of mixing plant used. In addition to plant calibration and daily checks ofmix proportions, freshly mixed soil-cement cement content can be tested using a titration test and hardened soil-cement cement content can be tested using ASTM D 806. (4) 

### Water Application. Water is added at the central mixing plant in quantities sufficient to bring the mixture to the optimum moisture content as determined by a laboratory moisture-density test. Generally the moisture content should not be more than two percentage points below or above the specified optimum moisture. To estimate mixing water requirements stockpile moisture content is determined and additional water requirements calculated. Experienced inspectors can determine, in a qualitative way, the moisture requirements just prior to compaction by squeezing the mixture in the palm of the hand. A mixture near optimum moisture content is just moist enough to dampen the hands when packed tightly and can be broken in two with little or no crumbling. During compaction the surface of the material may dry out (indicated by a graying of the surface). Moisture is brought back to optimum by fog spraying.

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Reference available through American Society for Testing and Materials, 1916 Race Street, Philadephia, PA 19103. 1 G-16 

### (5) Mix uniformity. Uniformity is checked visually by noting color uniformity either at the plant or by digging a hole in the loosely placed material in the layer. If, due to lightness of soil material color, it i s difficultto determine mixing, a 2 percent solution of phenolphthalein can be sprayed on a cut face of th e material to determine if any cement is present. The cement in the mixture will turn treated material pinkishred while untreated soil will retain its natural color. (6) T ransporting and spreading. Specified timing requirements for transporting and spreading should b e monitored. Traffic patterns and possible material contamination (especially near layer edges and ramps) s hould be checked. Layer offset distances and layer thickness and uniformity should also be checked. The spreader should not be allowed to empty, but should be stopped while there is still mix left in the hopper. This insures uniform spreader operation. (7) Compac tion. Samples of the soil-cement are taken from the batch and prepared for laboratory m oisture-density testing at the same time compaction is taking place. This accounts for timing parameters. In-place dens ity testing is conducted as soon as possible after compaction in a spot where the laboratory material has been taken. Field and laboratory densities are then compared. (8) C uring. Curing specifications and placement procedures should be closely monitored by the inspector. I f water curing is used, the equipment must be capable of fog, rather than pressure, spraying. Th e s urface mus t be kept continuously moist. Exposed surfaces should be cured for seven days. Curing times m ust be satisfied as well as provisions made in the case of freezing temperatures. Membrane cures must be of sufficient thickness to hold in moisture. G-8. References American Society for Testing and Materials 1999 1 

### American Society for Testing and Materials. (1993). 1993 Annual Book of Standards, Philadelphia, PA. ASTM C-150-98 1 

### American Society for Testing and Materials. 1998. “Specification for Portland Cement.” ASTM D-558-96 1 

### American Society for Testing and Materials. 1996a. “Test Methods for Moisture-density Relations of Soilcement Mixtures.” ASTM D-559-96 1 

### AmericanSociety for Testing and Materials. 1996b. “Test Methods for Wetting and Drying Compacted Soil-cement Mixtures.” ASTM D-560-96 1 

### American Society for Testing and Mater ials. 1996c. “Test Methods for Freezing and Thawing Compacted Soil-cement Mixtures.” ASTM D-806-96 1 

### AmericanSociety for Testing and Materials. 1996d. “Test Method for Cement Content of Soil-cement Mixtures.”EM 1110-2-1913 30 Apr 2000

G-17 

### ASTM D-1557-91 1 

### American Society for Testing and Materials. 1991. “Test Method for Laboratory Compaction Characteristics of Soil Using Modified Effort.” ASTM D-1632-96 1 

### AmericanSociety for Testing and Materials. 1996e. “Practice for Making and Curing Soil Cement Compression and Flexure Test Specimens in the Laboratory.” ASTM D-1633-96 1 

### AmericanSociety for Testing and Materials. 1996f. “Test Method for Compressive Strength of Molded Soil Cement Cylinders.” ASTM D-2487-93 1 

### American Society for Testing and Materials. 1993. “Classification of Soils for Engineering Purposes.” CRD-C-400 Corps of Engineers Portland Cement Association 1995 Portland Cement Association. 1995. “Soil Cement Construction Handbook.”where c ' k bl k f z bl d EM 1110-2-1913 30 Apr 2000

H-1 

### Appendix H Notation

The symbols that follow are used throughout this manual and correspond wherever possible to thos e recommended by the American Society of Civil Engineers.

Symbol Term c Cohesion per unit area; a constant for natural top stratum

c N Effective cohesion in terms of effective stress
c Coefficient of consolidation v C Compression index

c C Coefficient of secondary compression

á d Effective thickness of pervious substratum
e Void ratio F Transformation factor for permeability

t h Excess hydrostatic head o h N Hydrostatic head beneath landside toe of levee

o h Hydrostatic head beneath top stratum x H Net head i Critical gradient for landside top stratum c i Upward gradient at landside toe of berm 1 i Upward gradient at landside toe of levee o k Coefficient of permeability k Coefficient of permeability (top stratum) b k Average horizontal coefficient of permeability f k Coefficient of permeability (vertical) n k Permeability of landside stratum bl k Permeability of riverside stratum br L Distance from riverside levee toe to river

1 L Base width of levee and berm 2 L Length of top stratum landward of levee toe 3 M Slope of hydraulic grade line

d (Continued)EM 1110-2-1913

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H-2 Symbol Term Q Shear test for specimen tested at constant water content (unconsolidated-undrained) Q Total amount of seepage passing beneath levee S R Shear test for specimen consolidated and then sheared at constant water content (consolidated-undrained)
s (a) distance from the landside toe of the levee to the point of effective seepage entry

(b) shear test for specimen consolidated and sheared without restriction of change in water content (consolidated-drained)

x Effective length of riverside blanket 1 x Distance from landside levee toe to effective seepage exit 3 z Effective thickness of stratum b z Transformed thickness of top stratum t z Effective thickness of landside top stratum bl z Effective thickness of riverside top stratum br z Effective thickness of top stratum bt ã W et unit weight of soil t ã Unit weight of water w ã N Submerged or buoyant unit weight of soil ö N Angle of internal friction based on effective stresses S / Shape factor to generalized cross section of the levee and foundation