A 300 mm diameter well with a screen length 20 m is to be placed in an aquifer of thickness 40 m. a) Calculate the specific capacity of this well as percent of the maximum (full penetration). b) If you wanted to improve the design in order to reach 98% of the maximum specific capacity, how many screened sections and of what length would you need to install

Explanation:

Diameter of well = 300 mm = 0.03 m

Radius, r = 0.03/2 = 0.015 m, Length, h = 20 m

a) Volume of well, V = πr²h, where π = 22/7

∴ V = 22/7 X (0.03)² X 20 = 0.0566 m³

Hence, capacity of the well = 0.0566 X 1,000 = 56.6 Liters

b)  To improve the design by 98%, it can be calculated as follow:

The design wiil increase to 198%, that is: 56.6 Liters X 198%/100% = 112 Liters

c) The number of screen sections = Specific capacity of tank/Surface area of well

Surface area = 2πrh = 2 X 22/7 X 0.03 X 20 = 3.77 m²

= 56.6/3.77 = 15 

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