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

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7.2.1.2 System Selection The type of subsurface soil absorption system selected depends on the site characteristics encountered. Critical site factors include soil profile characteristics and. permeability, soil depth over water tables or bedrock, slope, and the size of the acceptable area. Where the soil is at least moderately permeable and remains unsaturated several feet below the system throughout the year, trenches or beds may be used. Trenches and beds are excavations of relatively large area1 extent that usually rely on the upper soil horizons to absorb the wastewater through the bottom and sidewalls of the excavation. Seepage pits are deep excavations designed primarily for lateral absorption of the wastewater through the sidewalls of the excavation; they are used only where the groundwater level is well below the bottom of the pit, and where beds and trenches are not feasible. Where the soils are relatively impermeable or remain saturated near the surface, other designs can be used to overcome some limitations. Mounds may be suitable where shallow bedrock, high water table, or slowly permeable soil conditions exist. Mounds are beds constructed above the natural soil surface in a suitable fill material. Fill systems are trench or bed systems constructed in fill material brought in to replace unsuitable soils. Fills can be used to overcome some of the same limitations as mounds. Curtain or underdrain designs sometimes can be used to artifically lower groundwater tables beneath the absorption area so trenches or beds may be constructed. Table 2-l presents the general site conditions under which the various designs discussed in this manual are best suited. For specific site criteria appropriate for each, refer to the individual design sections in this chapter. 7.2.2 Trench and Bed Systems 7.2.2.1 Description Trench and bed systems are the most commonly used method for onsite wastewater treatment and disposal. Trenches are shallow, level excavations, usually 1 to 5 ft (0.3 to 1.5 m) deep and 1 to 3 ft (0.3 to 0.9 m) wide. The bottom is filled with 6 in. (15 cm) or more of washed crushed rock or' 'gravel over which is laid a single line of perforated distribution piping. Additional rock is placed over the pipe and the rock covered with a suitable semipermeable barrier to prevent the backfill from penetrating the rock. Both the bottoms and sidewalls of the trenches are infiltrative surfaces. Beds differ from trenches in that they are wider than 3 ft (0.9 m) and may contain more than one line of distribution piping (see Figures 7-1 and 7-2). Thus, the bottoms of the beds are the principal infiltrative surfaces. 208
FIGURE 7-l TYPICAL TRENCH SYSTEM 209 Backfill 3/4 - 2-l/2 in. Rock w Water Table or Creviced Bedrock
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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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l SauJUOdtUo3 lesodsip pue JuJmeJJa
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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
Page 176 and 177: presents suggested design ranges fo
Page 178 and 179: Item Media Tank Aeration System RBC
Page 180 and 181: Observation Filter Ponding Filter F
Page 182 and 183: TABLE.6-21 HALOGEN PROPERTIES (27)
Page 184 and 185: The use of chlorine as a disinfecta
Page 186 and 187: HOC1 , would predominate. It is cle
Page 188 and 189: 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 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 274 and 275: 7.2.4.6 Considerations for Multi-Ho
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7.2.5.2 Application a. Site Conside
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7.2.6 Artificially Drained Systems
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---- FIGURE 7-17 UNDERDRAINS USED T
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periods, particularly on level site
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TABLE 7-11 DRAINAGE METHODS FOR VAR
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high water table elevation. To prev
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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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