On-Site Wastewater Treatment and Disposal Systems - Forced ...

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FIGURE 7-5 TRENCH SYSTEM INSTALLED TO OVERCOME A SHALLOW WATER TABLE 0~ RESTRICTIVE LAYER [AFTER (ii)] Diversion for Surface Water ---- -- Seasonally High WaterTable - or Flow R&tr&ive Layer _f d. Effluent Distribution -- -------- Ground Surface Methods of Application: To ensure that the absorption system performs satisfactorily over a reasonably long lifetime, the method of wastewater application to the infiltrative surface must be compatible with the ex- isting soil and site characteristics. Methods of wastewater application can be grouped into three categories: (1) gravity flow; (2) dosing; and (3) uniform application. For designs of distribution networks employing these methods, see Section 7.2.8) 1. Gravity flow is the simplest and most commonly employed of the distribution methods. Wastewater is allowed to flow into the absorption system directly from the treatment unit. With time, a clogging mat usually develops on the bottom surface of the absorption system and continuous ponding of the wastewater results. This may lead to more severe clogging of the soil, reducing the infiltration rate. However, this effect may be offset by the greater effective infiltrative area provided by submerging the sidewalls of the system, particularly in trench systems. The ponding also increases the hydraulic gradient 222
across the clogging mat, which can increase the infiltration rate (2)(18). If adequate treatment is to be achieved in coarse granular soils such as sands, wastewater application by gravity flow requires that a clogging mat exist at the infiltrative surfaces to prevent saturated conditions in the underlying soil and to prevent groundwater contamination. The mat develops with continued application, but groundwater contamination by pathogenic organisms and viruses can be a danger at first. 2. Dosing can be employed to provide intermittent aeration of the infiltrative surface. In this method, periods of loading are followed by periods of resting, with cycle frequencies ranging from hours to days. The resting phase should be sufficiently long to allow the system to drain and expose the infiltrative surface to air, which encourages rapid degradation of the clogging materials by aerobic bacteria. This method of operation may increase the rate of infiltration, as well as extend the life of the absorption system, because the clogging mat resistance is reduced (1)(4)(6)(15)(17). In sands or coarser textured materials, the rapid infiltration rates can lead to bacterial and viral contamination of shallow groundwater, expecially when first put into use (4). There- fore, systems constructed in these soils should be dosed with small volumes of wastewater several times a day to prevent large saturated fronts moving through the soil. In finer textured soils, absorption, rather than treatment, is the con- cern. Large, less frequent doses are more suitable in these soils to provide longer aeration times between doses (4). See Table 7-4 for suggested dosing frequencies. 3. Uniform Application means applying the wastewater in doses uni- formly over the entire bottom area of the system to minimize local-overloading and the depth of ponding fol-lowing each dose. This is usually achieved with a pressure distribution network. In this manner, the soil is more likely to remain unsaturated even during initial start-up when no clogging mat is present. The minimum depths of ponding during application permit rapid draining and maximum exposure of the bottom surface to air which reduces the clogging mat resistance. The sidewall is lost as an infiltrative surface, but this may be compensated for by the maintenance of higher infiltration rates through the bottom surface. See Table 7-4 for suggested dosing frequencies. 223
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DE SIGN MANUAL WASTEWATER TREATMENT
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FOREWORD Rural and suburban communi
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Chapter CONTENTS Page FOREWORD ACKN
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Number FIGURES Wastewater Managemen
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FIGURES Number Page ne Saturator Sa
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FIGURES Number Page Use of Metal Ho
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Number TABLES Selection of Disposal
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Number TABLES (continued) Operati o
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TABLES (continued) Number Page of D
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In many areas, onsite systems have
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2.1 Introduction CHAPTER 2 STRATEGY
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subsurface soil absorption is the p
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features of the site (See 3.3.1 and
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2.2.2 System Selection With the pot
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2.2.4 Onsite System Management Past
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determined largely by the physical
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16 - I ,
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Step Client Contact Preliminary Eva
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FIGURE 3-2 EXAMPLE OF A PORTION OF
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Property USDA Texture Flooding Dept
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TABLE 3-3 SOIL SURVEY REPORT INFORM
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found for a subsurface soil absorpt
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Instrument Supported - Abney Level:
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FIGURE 3-8 PREPARATION OF SOIL SAMP
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Sandy Loam + _. ,i . L Silt Loam Cl
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Depth (Ft.) 0 2 4 6 8 10 12 14 Text
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Grade Structureless Weak Moderate S
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Excavated Soil Material (Tamped in
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If test results agree with this tab
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Percolation test FIGURE 3-15 PERCOL
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mm..--- - --- FIGURE 3-16 COMPILATI
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FIGURE 3-16 (continued) 0 Texture S
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13. Winneberger, J. T. Correlation
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is the overall socioeconomic status
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FIGURE 4-l FREQUENCY DISTRIBUTION F
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extreme, however, minimum and maxim
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4i2.2.2 Individual Activity Contrib
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and the resultant wastewater charac
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TABLE 4-7 TYPICAL WASTEWATER FLOWS
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TABLE 4-9 FIXTURE-UNITS PER FIXTURE
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4.3.2 Wastewater Quality The qualit
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* FIGURE 4-3 STRATEGY FOR PREDICTIN
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12. Witt, M. Water Use in Rural Hom
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5.2 Water Conservation and Wastewat
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5.2.2 Water-Saving Devices, Fixture
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TABLE 5-2 (continued) Total Flo Red
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Generic Typea Description Pit Privy
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TABLE 5-4 WASTEWATER FLOW REDUCTION
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5.2.2.3 Clotheswashing Devices and
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Generic Typea Description Mixing Va
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TABLE 5-6 WASTEWATER FLOW REDUCTION
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TABLE 5-7 EXAMPLE POLLUTANT MASS RE
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FIGURE 5-l EXAMPLE STRATEGIES FOR M
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In most situations, projections of
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FIGURE 5-3 FLOW REDUCTION EFFECTS O
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5.7 References 1. 2. 3. 4. 5. 6. 7.
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6.1 Introduction CHAPTER 6 ONSITE T
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318QaQEi33aNON 01-9 3msu simaotld N
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SNOIlQ~tl9I~N03 1NQld 39QI3Qd NOIlQ
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El-9 31av1 S3ItX-US 01313 1INt-l 31
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d. Method of Aeration Oxygen is tra
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contain electrical components, they
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control that results in power savin
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TABLE 6-16 OPERATIONAL PROBLEMS--EX
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I TRICKLING FILTFR FIGURE 6-12 EXAM
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presents suggested design ranges fo
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Item Media Tank Aeration System RBC
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Observation Filter Ponding Filter F
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TABLE.6-21 HALOGEN PROPERTIES (27)
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The use of chlorine as a disinfecta
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HOC1 , would predominate. It is cle
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6.5.2.5 Construction Features a. Fe
Page 190 and 191: e Wastewater FIGURE 6-14 IODINE SAT
Page 192 and 193: (experience with some units indicat
Page 194 and 195: directing flow through and around t
Page 196 and 197: FIGURE 6-17 TYPICAL UV STERILIZING
Page 198 and 199: Shigella TABLE 6-25 UV DOSAGE FOR S
Page 200 and 201: Cleaning of quartz glass enclosures
Page 202 and 203: the bubble diffuser units to lo-30
Page 204 and 205: TABLE 6-26 POTENTIAL ONSITE NITROGE
Page 206 and 207: Nitrification of septic tank efflue
Page 208 and 209: Influe? Effluent 0 Tank Denitrifica
Page 210 and 211: solution. It can be used to remove
Page 212 and 213: TABLE 6-27 POTENTIAL ONSITE PHOSPHO
Page 214 and 215: Anionic polyelectrolytes can be use
Page 216 and 217: component of the onsite treatment s
Page 218 and 219: 7. 8. 9. 10. 11. 12. 13. 14. 15. 16
Page 220 and 221: 30. 31. 32. 33. 34. 35. 36. 37. 38.
Page 222 and 223: 58. 59. 60. 61. 62. 63. 64. 65. 66.
Page 224 and 225: 7.1 Introduction CHAPTER 7 DISPOSAL
Page 226 and 227: 7.2.1.2 System Selection The type o
Page 228 and 229: Distribution FIGURE 7-2 TYPICAL BED
Page 230 and 231: TABLE 7-l SITE CRITERIA FOR TRENCH
Page 232 and 233: TABLE 7-2 RECOMMENDED RATES OF WAST
Page 234 and 235: can slough off the sidewall. These
Page 236 and 237: FIGURE 7-3 ALTERNATING TRENCH SYSTE
Page 238 and 239: FIGURE 7-4 PROVISION OF A RESERVE A
Page 242 and 243: TABLE 7-4 DOSING FREQUENCIES FOR VA
Page 244 and 245: The depth of the porous media may v
Page 246 and 247: Distr Pipe, FIGURE 7-6 TYPICAL INSP
Page 248 and 249: against freezing and to stabilize .
Page 250 and 251: Pertodic Deternvne Cause u O&loadin
Page 252 and 253: oils, and greases, can cause failur
Page 254 and 255: 4" Inspection Pip FIGURE 7-9 SEEPAG
Page 256 and 257: The same guidelines used in locatin
Page 258 and 259: Straw, Hay or Fabric? FIGURE 7-10 T
Page 260 and 261: I tern Landscape Position Slope Typ
Page 262 and 263: The acceptable depth to an impermea
Page 264 and 265: FIGURE 7-12 PROPER ORIENTATION OF A
Page 266 and 267: Mound Height TABLE 7-9 DIMENSIONS F
Page 268 and 269: Example 7.1: Calculation of Mound D
Page 270 and 271: 1.0 + 1.4 = - t 0.75 + 1.5 1 [ = (3
Page 272 and 273: . Fill Placement Step 1: Place the
Page 274 and 275: 7.2.4.6 Considerations for Multi-Ho
Page 276 and 277: 7.2.5.2 Application a. Site Conside
Page 278 and 279: 7.2.6 Artificially Drained Systems
Page 280 and 281: ---- FIGURE 7-17 UNDERDRAINS USED T
Page 282 and 283: periods, particularly on level site
Page 284 and 285: TABLE 7-11 DRAINAGE METHODS FOR VAR
Page 286 and 287: high water table elevation. To prev
Page 288 and 289: FIGURE 7-18 TYPICAL ELECTRO-OSMOSIS
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7.2.8.1 Design a. Single Line . Sin
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Inlet From Pretreatment or Previous
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watertight Pipe & Joints1 FIGURE 7-
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ox networks (see Figure 7-23). Howe
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280 s P 4
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FIGURE 7-26 LATERAL DETAIL - TEE TO
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To simplify the design of small pre
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FIGURE 7-29 RECOMMENDED MANIFOLD DI
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Step 3: Select lateral diameter. Fo
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Step 8: Select proper pump or sipho
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Friction loss in 25 ft 2. Velocity
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FIGURE 7-32 DISTRIBUTION NETWORK FO
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In summary, the final network desig
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7.2.8.3 Construction FIGURE 7-33 SC
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Since the network is pressurized, s
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FIGURE 7-35 CROSS SECTION OF TYPICA
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The capillary rise characteristic o
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The hydraulic loading rate is deter
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during the critical months of the y
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7.3.3 Evaporation and Evaporation/I
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FIGURE 7-37 TYPICAL EVAPORATION/INF
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October November December January F
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7.3.3.7 Seasonal, Multifamily, and
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13. 14. 15. 16. 17. 18. 19. 20. 21.
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38. 39. 40. 41. 42. 43. 44. 45. 46.
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The grease traps discussed here are
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Type of Fixture Restaurant kitchen
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Removable Slab Inlet --CL Tee with
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- 8.3.3 Factors Affecting Performan
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The pumping head is calculated by a
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liquid level drops, the weights los
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8.3.5 Construction The tank must be
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Hori FIGURE 8-6 TOP VIEW OF DIVERSI
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9.1 Introduction CHAPTER 9 RESIDUAL
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Parameter TABLE 9-2 CHARACTERISTICS
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Parameter Total Coliform Fecal Coli
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9.4.1 Land Disposal Four methods ca
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TABLE 9-4 (continued) Alternative D
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W z Process Lagooning (1)(13)(14) (
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Process Description Liouid Stream S
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11. 12. 13. 14. 15. 16. 17. 18. 19.
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Some of the techniques discussed ma
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10.3.1 State Agencies Except for th
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10.3.4.1 Private Nonprofit Institut
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10.4.1.1 Standards for Site Suitabi
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Scope of Activities Perform inspect
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Scope of Activities Perform necessa
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10.4.4.1 Inspections Inspections co
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SYSTEM 1. U.S. Bureau of Reclam$t~o
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FIGURE A-2 TEXTURAL TRIANGLE DEFINI
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Class Platelike. with one dimension
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saturation may be necessary to conf
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the porosity of soils containing mo
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FIGURE A-5 SOIL MOISTURE RETENTION
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A.3.3 Flow of Water Through Layered
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GLOSSARY A horizon: The horizon for
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following chemical flocculation; wi
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floodway: A channel built to carry
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ped: A unit of soil structure such
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solids: Material in the solid state
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TECHNICAL REPORT DATA (Please read
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