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Primary Piping System Installation <br /> TRENCHING AND BACKFILLING Compact backfill carefully over and around the piping <br /> system. When using tamping equipment, take care to <br /> Proper construction of trenches is important. They prevent vibration from driving small stones into the <br /> should be wide and deep enough to accommodate the pipe wall. The amount of <br /> piping and backfill material. See Table 5 for recommended compaction and the type <br /> minimum burial depths. of soil determines the soil <br /> modulus. Forexample,pea �S'• <br /> • Typically, all piping should slope at least 1/8"(3 mm)per gravel has a typical <br /> foot toward the tank. Support pipe properly to prevent modulus of 1,000 psi with <br /> low points. no compaction,while sand Backfill must O <br /> • The piping should be separated by a distance of at requires slight compaction be tamped into <br /> least four to six inches (100 mm-150 mm). For double- (85% Proctor density) t0 shaded areas. <br /> wall secondary containment piping installations, refer to achieve a modulus of 1,000 psi. Refer to ASTM D3839 <br /> Table 11 on page 18 for proper distances. or AWWA C950 for further details. <br /> • Cover the pipe as soon as possible after successful <br /> I-�f-y f-�;f-y f-y((f,,aa- f- testing to eliminate the chance of damage to the pipe, <br /> t 3- c ..l,J• �J• `�J• •'�,J•' ' Table 5 floating of the pipe due to flooding, or shifting of the line <br /> �1SA�1,AM,A�,1,A�.1,A�.1,��.1'A�1_ due to Cavin in of the — <br /> _ - .� �r- g <br /> ( [ 4•(min _1trench walls. If damage is <br /> i7 Ay 100 mm I�l ,Table 5 suspected, the lines <br /> A 2 should be retested. <br /> ��'A�,• Frozen earth will eventually <br /> t �y c' • thaw, leaving the pipe with <br /> -l%A�-i"' V_ '_,_ 6°tmin.l insufficient support and YES NO <br /> >J-�t= -" -� • >• (,+Mmm voids around the pipe. <br /> Take care to remove frozen <br /> N-H lumps from all backfill materials before backfilling. <br /> 6" <br /> 150 mm <br /> The pipe must be completely surrounded with select In all cases, the pipe must be completely surrounded with <br /> backfill sand,pea 2ravel or washed crushed stone). select backfill (sand, 1/8" to 3/4'1 pea gravel, Or 1/8" to 1/2" <br /> washed,crushed stone). There should never be voids under <br /> or around the pipe. Six inches (150 mm) of the fill must be <br /> placed under the pipe as bedding material. Native backfill <br /> materials should never be used. <br /> TABLE 5. Recommended Minimum Burial Depths Based on Soil Modulus of 1,000 psi or Higher <br /> (Refer to ASTM D3839 or AWWA C950 for Method/Theory) <br /> Minimum Min.Amount of Sand, Pea Gravel, <br /> Pipe Size Burial Depth Washed Stone Above Top of Pipe <br /> In. mm Surface Condition In. mm In. mm <br /> 2 50 Unpaved 17 432 12 305 <br /> Paved,min.4"(100 mm)asphalt 12 305 8 203 <br /> Paved,min.4"(100 mm)concrete 9 229 5 127 <br /> Paved,min.6"(150 mm)concrete 9 229 3 76 <br /> 3 75 Unpaved 20 508 14 356 <br /> Paved,min.4"(100 mm)asphalt 13 330 9 229 <br /> Paved,min.4"(100 mm)concrete 11 279 7 178 <br /> Paved,min.6"(150 mm)concrete 10 254 4 102 <br /> 4 100 Unpaved 20 508 14 356 <br /> Paved,min.4"(100 mm)asphalt 14 356 10 254 <br /> Paved,min.4"(100 mm)concrete 11 279 7 178 <br /> Paved,min.6"(150 mm)concrete 10 254 1 4 102 <br /> 6 150 Unpaved 36 914 14 356 <br /> Paved,min.4"(100 mm)asphalt 24 610 10 254 <br /> Paved,min.4"(100 mm)concrete 20 508 7 178 <br /> Paved,min.6"(150 mm)concrete 16 406 4 102 <br />