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

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7.2.4.6 Considerations for Multi-Home and Commercial Wastewaters Designs of the mound system for larger flows follow the same design principles as for smaller flows. In cluster systems serving more than five homes, however, peak flow estimates can be reduced because of flow attenuation, but contributions from infiltration through the collection system must be included. Peak flow estimates should be based on the total number of people to be served (see Chapter 4). Rates of infiltration vary with the type of collection sewer used (19)(20). With commercial flows, the character of the wastewater is an important consideration. Proper pretreatment is necessary if the character is significantly different than domestic wastewater. Modifications to the design of the mound system may be desirable for larger flows on sloping sites or in slowly permeable soils. In both instances, the absorption area should be broken up into a series of trenches or smaller beds. This is beneficial on sloping sites because the beds can be tiered to reduce the amount of fill required (see Figure 7-14). Depths of fill material below beds should not exceed 4 to 5 ft (1.3 to 1.7 ml because differential settling will cause the bed to set- tle unevenly. If the system is tiered, each trench or bed must be dosed individually. This can be done by automatic valving or alternating pumps or siphons. In sites with slowly permeable soils, breaking the absorption area into smaller trenches or beds helps distribute the effluent over much wider areas. Spacing of the beds or trenches should be sufficient so that the wastewater contributed from one trench or bed is absorbed by the natural soil before it reaches the lower trench or bed (see Table 7-10). The beds or trenches should be as long as the site allows. A long bed, broken into several shorter systems, each served by a pump or siphon, is preferred over two or more short parallel beds, especially in soils where the effluent moves downslope. Flexibility in operation should also be incorporated into systems serving larger flows, since a failure can create a significant problem. Alternating bed. 'systems should be considered. A three-bed system is suggested where each bed contains 50% of the required absorption area (19). Two beds are always in operation, providing 100% of the needed infiltrative surface. The third bed is alternated into service on a yearly schedule. Thus, each field is in service for two years and "rested" for one year to rejuvenate. The third bed also acts as a standby unit in case one bed fails. The idle fields can be put into service immediately while the failed bed is rehabilitated. 256
7.2.5 Fill Systems 7.2.5.1 Description FIGURE 7-14 TIERED MOUND SYSTEM Fill systems may be used on sites with slowly permeable soils overlying sands and sandy loams where construction of a conventional system below the tight soil horizons may be ruled out. If the depth from the top surface of the underlying sand or sandy loam to the seasonally high water table or bedrock is inadequate to construct a trench or bed system, the slowly permeable soil may be stripped away and replaced with a sandy fill material to provide 2 to 4 ft (0.6 to 1.2 m) of unsaturated soil. A trench or bed system may then be constructed within the fill. Mound systems would also be suitable designs for these conditions and may be less expensive to construct, but fill systems offer some advan- tages. If the soils overlying the sands or sandy loams are very slowly permeable, the size of a fill system may be smaller than that of a mound permitting their installation in smaller areas. Also, fill systems usu- ally have less vertical relief above the natural grade than do mounds, This may be desirable for landscaping purposes. 257
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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
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e Wastewater FIGURE 6-14 IODINE SAT
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(experience with some units indicat
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directing flow through and around t
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FIGURE 6-17 TYPICAL UV STERILIZING
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Shigella TABLE 6-25 UV DOSAGE FOR S
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Cleaning of quartz glass enclosures
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the bubble diffuser units to lo-30
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TABLE 6-26 POTENTIAL ONSITE NITROGE
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Nitrification of septic tank efflue
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Influe? Effluent 0 Tank Denitrifica
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solution. It can be used to remove
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TABLE 6-27 POTENTIAL ONSITE PHOSPHO
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Anionic polyelectrolytes can be use
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component of the onsite treatment s
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7. 8. 9. 10. 11. 12. 13. 14. 15. 16
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30. 31. 32. 33. 34. 35. 36. 37. 38.
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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 240 and 241: FIGURE 7-5 TRENCH SYSTEM INSTALLED
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 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
Page 290 and 291: 7.2.8.1 Design a. Single Line . Sin
Page 292 and 293: Inlet From Pretreatment or Previous
Page 294 and 295: watertight Pipe & Joints1 FIGURE 7-
Page 296 and 297: ox networks (see Figure 7-23). Howe
Page 298 and 299: 280 s P 4
Page 300 and 301: FIGURE 7-26 LATERAL DETAIL - TEE TO
Page 302 and 303: To simplify the design of small pre
Page 304 and 305: FIGURE 7-29 RECOMMENDED MANIFOLD DI
Page 306 and 307: Step 3: Select lateral diameter. Fo
Page 308 and 309: Step 8: Select proper pump or sipho
Page 310 and 311: Friction loss in 25 ft 2. Velocity
Page 312 and 313: FIGURE 7-32 DISTRIBUTION NETWORK FO
Page 314 and 315: In summary, the final network desig
Page 316 and 317: 7.2.8.3 Construction FIGURE 7-33 SC
Page 318 and 319: Since the network is pressurized, s
Page 320 and 321: FIGURE 7-35 CROSS SECTION OF TYPICA
Page 322 and 323: 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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