Page 187 - Water and wastewater engineering

4-42 WATER AND WASTEWATER ENGINEERING

4. Explain the purpose of a removable roof, auxilary heat, and ventilation in a well house.
5. Sketch a piezometric profile for a single well pumping at a high rate, and sketch a pro-
file for the same well pumping at a low rate.
6. Sketch a piezometric profile for two or more wells located close enough together to
interfere with one another.
7. Sketch a well-pumping test curve which shows ( a ) the interception of a barrier and ( b )
the interception of a recharge area.
With the use of this text, you should be able to do the following:

8. Select the correct isolation distances for a well based on a description of the users.
9. Calculate the appropriate amount of disinfectant for a well given the diameter, depth of
water in the well, and the reagent to be used.

10. Calculate the drawdown at a pumped well or observation well if you are given the
proper input data.
11. Calculate the transmissivity and storage coefficient for an aquifer if you are provided
with the results of a pumping test.
12. Calculate the interference effects of two or more wells.
13. Determine the number of wells for a small community’s well field.

14. Select an appropriate type of pump and the required discharge capacity to meet demand.
15. Select and check the appropriate diameter for a well casing.
16. Determine the required depth of a well.

17. Determine the appropriate length of well screen for a given aquifer formation.
18. Select the appropriate slot size given a grain size distribution.
19. Determine the appropriate screen diameter given the hydraulic conductivity of the aqui-
fer and the slot size.
20. Select an appropriate pump and specify the number of stages based on a TDH calcula-
tion you have performed.

4-6 PROBLEMS

4-1. A 0.30 m diameter well fully penetrates a confined aquifer that is 28.0 m thick. The
aquifer material is fractured rock. If the drawdown in the pumped well is 6.21 m after
3
pumping for 48 hours at a rate of 0.0075 m /s, what will the drawdown be at the end
of 48 days of pumping at this rate?
4-2. An aquifer yields the following results from pumping a 0.61 m diameter well at
3
0.0303 m /s: s 0.98 m in 8 min; s 3.87 m in 24 h. Determine its transmissivity.
Report your answer to three significant figures.