Geoscience Reference
In-Depth Information
where
C = Circumference.
π = pi = 3.1416.
D = Diameter.
Use this calculation if, for example, the circumference of a circular tank must be determined.
EXAMPLE 2.43
Problem: Find the circumference of a circle that has a diameter of 25 feet (π = 3.14)
Solution:
C = π × 25 ft
C = 3.14 × 25 ft = 78.5 ft
EXAMPLE 2.44
Problem: A circular chemical holding tank has a diameter of 18 m. What is the circumference of
this tank?
Solution:
C = π × 18 m
C = 3.14 × 18 m = 56.52 m
EXAMPLE 2.45
Problem: An influent pipe inlet opening has a diameter of 6 ft. What is the circumference of the
inlet opening in inches?
Solution:
C = π × 6 ft
C = 3.14 × 6 ft = 18.84 ft
2.11. 3.2 Area
For area measurements in water/wastewater operations, three basic shapes are particularly impor-
tant—namely, circles, rectangles, and triangles. Area is the amount of surface an object contains or
the amount of material it takes to cover the surface. The area on top of a chemical tank is called the
surface area. The area of the end of a ventilation duct is called the cross-sectional area (the area
at right angles to the length of ducting). Area is usually expressed in square units, such as square
inches (in. 2 ) or square feet (ft 2 ). Land may also be expressed in terms of square miles (sections) or
acres (43,560 ft 2 ) or in the metric system as hectares. In fisheries operations, pond stocking rates,
limiting rates, and other important management decisions are based on surface area (Masser and
Jensen, 1991).
If contractor's measurements or country field offices of the U.S Department of Agricultural
Soil Conservation Service do not have records on basin, lake, or pond measurements, then survey-
ing basins, tanks, lagoons, and ponds using a transit is the most accurate way to determine area.
Less accurate but acceptable methods of measuring basin or pond area are chaining and pacing.
Inaccuracies in these methods come from mismeasurements and measurement over uneven or slop-
ing terrain. Measurements made on flat or level areas are the most accurate.
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