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SECTION 6 <br /> SMITH <br /> INSTALLATION <br /> 1.6.1 Piping layout properly to prevent traps or 1/8-inch to 3/4-inch pea gravel). <br /> Advance planning of the piping sumps. 3. Compact backfill carefully over <br /> layout is essential.It will make ser- 2. The piping should be separated and around the piping system. <br /> vicing the system easier and can by a distance of at least four to (See Figure 1.6.1). When using <br /> reduce the quantities of material six inches (102-152 mm); the tamping equipment, take care <br /> required. pipe and trench wall should be to prevent vibration from driving <br /> 1. Using the shortest practical separated by at least six inches small stones into the pipe wall. <br /> route, run pipe in a single 052 mm).See Figure 1.6.3.For The amount of compaction and <br /> double-wall secondary contain- <br /> trench from the tanks to the ent piping installations, refer the type of soil determines the <br /> m <br /> dispensers and from the tanks mart Two, Section 3, Figure soil modulus. For example, pea <br /> to the vent risers. to Part <br /> for proper distances. gravel has a typical modulus of <br /> 2. Pipe should run parallel to the 2. 1,000 psi with no compaction, <br /> tanks and dispensers. Note: In all cases, the pipe while sand requires slight com- <br /> should be completely surround- paction (85% Proctor density) <br /> 3. Avoid piping across the tanks. ed with select backfill (sand or to achieve a modulus of 1,000 <br /> 1.6.2 Trenching and backfilling <br /> Proper construction of trenches is <br /> important. They should be wide <br /> and deep enough to accommodate <br /> the piping and backfill material. <br /> See Table 1.6.1 for recommended 0 O , O <br /> minimum burial depths. <br /> 1. Typically,all piping should slope 0 :'�' YES NO <br /> at least 1/8 inch (3 mm) per foot <br /> toward the tank. Support pipe Figure 1.6.1 Figure 1.6.2 <br /> TABLE 1.6.1 <br /> 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 /> Min.Amount of Sand <br /> Minimum or Pea Gravel above <br /> Pipe Size Surface Condition Burial Depth the top of the pipe <br /> (in.) .,,,:(mm) (in.) (mm) (in.) (mm) <br /> 2 51 Unpaved 17 432 12 305 <br /> Paved,min.4"(102 mm)asphalt 12 305 8 203 <br /> Paved,min.4"(102 mm)concrete 9 229 5 127 <br /> 3 76 Unpaved 20 508 14 356 <br /> Paved,min.4"(102 mm)asphalt 13 330 9 229 <br /> Paved,min.4"(102 mm)concrete 11 279 7 178 <br /> 4 102 Unpaved 20 508 14 356 <br /> Paved,min.4"(102 mm)asphalt 14 356 10 254 <br /> Paved,min.4"(102 mm)concrete 11 279 7 178 <br /> 9 <br />