How to Calculate the Volume of a Well

Introduction

• Discuss which dimensions are needed.

• How to obtaining the dimensions.

• Example

• Alternative method

Goals of this Presentation

• Establish the importance of properly calculating the volume of a well.

• Describe the dimensions that are needed for the calculation and how to obtain them.

• Create a clear understanding of the calculations through an example problem.

• Describe alternate methods to completing the calculations.

Why is this important?

• The volume of the well is used to determine the amount of plugging material needed.

• The volume is also used to determine the needed amount of disinfectant.

• Assuming the wrong volume of the well could lead to many future problems.

According to the video what dimensions are needed in order to accurately calculate the volume of

a well?• Well diameter

• Total depth

• Depth of the water

Obtaining Well Dimensions

• Diameter of the well – measured distance across the inner lip of the well

• Total well depth – measured distance from top to bottom of well.

• Water depth – measured distance of depth of water in the well. (Tie a weight to some string and drop it to the bottom of the well. Retrieve the string and measure the portion of the string that is wet.)

Hand Dug Well Example

• You have large hand dug well that is 3 feet in diameter and is 45 feet deep. The depth of water in the well is 10 feet.

Hand Dug Well Example

• The volume of the well is calculated by the formula.

V = ((Π * D2)/ 4)* d

Where :

Π= 3.1416

D=diameter of well (feet)

d= depth of well (feet)

Hand Dug Well Example

• The volume of the well is

V= ((3.416* 32)/4) *45

V= 318.53 ft3

1 yd3 = 27 ft3

V= 11.79 yd3

Example

• An abandoned well is 6 inches in diameter, 100 feet in depth, and the water level is 40 feet.

Example

• The volume of the well is

D= 6in/ 12in/ft = 0.5 ft

V= ((3.416* 0.52)/4) *100

V= 19.62 ft3

Alternate Method

• Use Table 1 Plugging Material Calculation Sheet.

• And the diameter of the well.

Well or Hole Diameter

Cement Bentonite Chips

Inches Linear Feet Linear Feet

2 50.3 31.3

3 28.8 13.9

4 16.2 1.9

5 10.4 5

6 7.2 3.5

7 5.3 2.6

8 4 2

9 3.2 1.5

10 2.6 1.3

12 1.8 0.86

14 1.3 0.63

16 1 0.48

18 0.8 0.38

20 0.6 0.31

24 0.4 0.21

36 0.2 0.097

40 0.16 0.078

44 0.13 0.065

48 0.11 0.054

Alternative Method

• Bags of cement needed (94 lb per sack)

100 feet / 7.2 feet = 13.8 sacks

• Bags of Bentonite needed (50 lb per sack)

100 feet / 3.5 feet = 28.5 sacks

Conclusion

• Well depth, diameter, and depth of the water are all needed in calculating the volume of the well.

• How to obtain these dimensions.

• There are several ways to calculate the amount of plugging material that is needed.