A = land average slope. B = required pond width.

C = cut section area required to level the platform. D = soil volume for platform construction. E = total soil volume = platform bund.

F = bund landfill volume, compensated (f = 1.43, where f = expansion factor for loose soil). G = number of hours of Caterpillar tractor use (86 HP) needed for construction.

H = number of hours of scraper tractor + number of hours of Caterpillar tractor needed for construction.

If levels and soils are suitable, they can be excavated directly into the soil using planers or bucket excavators. According to Wolf (1994), a triangular channel section can be made using a scraper, with an output of 450 to 700 m/h. With a bucket excavator, channels are built from 0.3 to 0.5 m width, in rectangular or trapezoidal section, with output ranging from 21 to 46 m/h for dry soils and 12 to 28 m/h for wet soils. To avoid seepage, channels can be covered with plastic or with a soil-cement mixture of approximately 3 to 6 parts soil to 1 part cement. Alternatively, less permeable soils can be layered over the inside of the channel. Smaller and shorter channels can also be built with lateral bunds of brick or cement block, on a concrete base, typically 0.1 m over a gravel/rock base of 0.2 m. This is a relatively high-cost structure but lasts longer and can carry higher flows for its size. Sivalingham (1974), Wheaton (1977) and FAO (1992) provided information relating channel dimensions according to water requirements.

Pipes are considerably more expensive, but occupy less space and can be used more conveniently in changing gradients. With sufficient care, and the use of air vents, they may also be used as siphon devices. However, they need to be sized correctly, selected for the appropriate pressure grade, and installed properly. Pipe flow and technical specifications are normally available from reliable pipe suppliers. It is important to ensure that pipes are properly protected. If installed below ground, they should be laid in a trench, normally cut using a narrow bucket excavator, in which at least 0.1 m of graded sand/gravel bedding material is placed. Joints should be cleanly and securely made, and the pipes filled around with additional material, then graded small rock and, finally, a cover of top soil. Where heavier surface loads are likely (e.g. due to the passage of vehicles), a concrete or concrete slab protection should be provided. Where pipes are surface mounted, they should be securely positioned (e.g. using wooden stakes, clamps or concrete

Table 8.3 Earth moving and machine yields for pond construction under different conditions, area and bund internal slope. (Modified from Wolf 1994, copyright 1994 with permission.)

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How To Have A Perfect Boating Experience

How To Have A Perfect Boating Experience

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