Well Drilling and Inspection Techniques

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Questions and Answers

What is the maximum depth at which a drilled pipe can be utilized?

50 feet

130 feet

4000 feet (correct)

15 feet

What is the function of caissons in the context presented?

To collect excess water

To facilitate horizontal drilling

To support adjacent structures (correct)

To transport heavy machinery

What type of structure is typically jacked through the ports near the bottom of water bodies?

Drilled wells

Radial pipes (correct)

Concrete barriers

Caisson foundations

How deep can caissons reach when sunk into the aquifer?

Up to 130 feet Signup and view all the answers

What is a useful application for bored pipes?

Pumping loose sand Signup and view all the answers

What is the maximum size of a bored pipe mentioned?

36 inches Signup and view all the answers

In which formation are radial pipes typically installed?

In sandy formations Signup and view all the answers

What is a primary reason for using pumps with single metal types?

To prevent corrosion Signup and view all the answers

What type of equipment is used for Down Hole Inspections?

Special television equipment Signup and view all the answers

What is an essential feature of a rotating earth auger?

It helps to excavate loose soil Signup and view all the answers

What depth can wells be inspected using special television equipment?

Up to 900 m Signup and view all the answers

What is another term for periodic well cleaning?

Well rehabilitation Signup and view all the answers

Why is effective sealing important after the abandonment of wells?

To prevent pollution of ground water Signup and view all the answers

Which organization’s guidelines must be followed for the abandonment of wells?

AWWA Signup and view all the answers

What type of data is included in pre-design checklists for well locations?

Geological and groundwater resource reports Signup and view all the answers

What information is gathered from existing wells to assess treatment requirements?

Chemical, physical, and bacteriological analyses Signup and view all the answers

What is the primary reason for selecting the northeast flatland site for test drilling?

It has good potential for recharge from surface drainage. Signup and view all the answers

What is indicated by the records regarding the flooding risk at the chosen drilling site?

The site has a 100-year flood level of approximately 675 feet. Signup and view all the answers

What is a primary characteristic of an aquifer?

It yields water in sufficient quantity to be economical. Signup and view all the answers

What does the water table represent?

The level of saturated soil below ground. Signup and view all the answers

Which statement about the situation of the site is accurate?

The site is bordered by a large river on the west. Signup and view all the answers

What is the required yield for the well in gallons per minute (gpm)?

350 gpm Signup and view all the answers

Which condition allows water in a well to rise above the top of the aquifer?

The water being under artesian conditions. Signup and view all the answers

Which feature was not included in Figure B-1 for clarity?

Vegetation Signup and view all the answers

What factors can cause the water table to fall?

Periods of drought. Signup and view all the answers

Which of the following describes the surrounding land use of the site?

Undeveloped land primarily. Signup and view all the answers

What is a characteristic of confined aquifers?

They are located directly beneath an impermeable bed. Signup and view all the answers

What type of well was specifically mentioned in the test drilling?

Pumping well. Signup and view all the answers

What type of materials are typically targeted for well location?

Coarse sand and gravel with interconnecting pore spaces. Signup and view all the answers

What is the depth to the static water level as indicated by the pumping test?

100 ft Signup and view all the answers

How is unconfined water in aquifers typically described?

It is directly influenced by atmospheric conditions. Signup and view all the answers

What best describes groundwater infiltration?

Water percolating down through soil and rock layers. Signup and view all the answers

What is the minimum casing diameter required for the pump specified?

8 inches Signup and view all the answers

What is one of the main purposes of grouting in well construction?

To prevent contamination from the surface Signup and view all the answers

What pressure must the distribution system maintain at the maximum ground elevation of 820 ft?

40 psi Signup and view all the answers

What component is included in the calculation of Total Dynamic Head (TDH) that is NOT influenced by elevation?

Friction head Signup and view all the answers

When should grout be completely placed in the well creation process?

Before the initial set occurs Signup and view all the answers

What factor is considered when determining the location for well installation?

Future facility expansion Signup and view all the answers

Where should grout ideally be introduced in the well construction process?

At the bottom of the space to be grouted Signup and view all the answers

What standard practice is mentioned for water treatment at the well site?

Chlorine disinfection Signup and view all the answers

What should be ensured to prevent subsurface contamination?

Sealing off poor quality water formations Signup and view all the answers

How should the well location be selected to protect water quality?

On elevated ground away from pollution sources Signup and view all the answers

What is the required action before selecting a pump for the system?

Review manufacturer's literature Signup and view all the answers

What is the purpose of analyzing water samples according to Standard Methods?

To ensure no treatment is necessary Signup and view all the answers

What additional feature is recommended to protect well water quality?

Construction of a concrete slab Signup and view all the answers

What is the minimum spacing required for the installation of the additional well?

250 ft Signup and view all the answers

What is the minimum thickness for the concrete slab surrounding the well casing?

100 mm (4 in) Signup and view all the answers

How far should the top of the well casing extend above the concrete surface slab?

300 mm (12 in) Signup and view all the answers

Study Notes

Bong County Technical College - Course Information

Location: Gbarnga City, Bong County
Department: Engineering
Course Title: Water supply and environmental Engineering
Lecturer: Eng. Cooper B. Saysay
Qualifications: BSc, MSc in Civil Engineering
Email: [email protected]
Contact: +231-770-299-886/+231-880-538-294

Sources of Water

Rain water
Surface water
Ground water
Water obtained from reclamation

Water Supply Systems

Objective: to take water from the best available source and process to ensure good physical quality, free from unpleasant taste/odour and free from anything detrimental to health
Involves: additions to, subtractions from, or chemical changes in the raw water
Components: Collection works, Transmission works, Purification works, and Distribution works

Hydrology

The science dealing with the occurrence, distribution, and movement of water on Earth, including the atmosphere and below the surface.
Water exists in vapour form, on the surface as water, snow or ice and below the surface as ground water.

Computation of Average Rainfall

Arithmetic Average Method: used when rainfall is uniformly distributed, involves calculating the simple average of the recorded values
Thiessen Polygon Method: more common, involves weighting the rain-gauge observations according to the area they represent
Isohyetal Method: involves drawing lines connecting points with equal rainfall amounts

Infiltration

Defined as the movement of water from the soil surface into the soil
Infiltration capacity: maximum rate of water entry into soil
Infiltration rate: rate at which water enters the soil

Infiltration Index

Represents the average rate of loss of water
Two types:
- Average infiltration rate (W-index)
- K-index

Chapter 1 - Introduction

Purpose and Scope: Introduction to selecting water sources and determining water requirements for water supplies.
Applicability: Guidelines are applicable to selecting water sources and planning/designing water supply systems.
References: Many professional references are available in literature.
Definitions: General Definitions: Water works, supply works, supply line, treatment work, distribution system, feeder mains, distribution mains, service line. Also addresses effective population, capacity factor, and required daily demand, peak domestic demand, fire flow, and fire demand, rated capacity and cross-connections, definitions of several terms relating to wells and ground water such as specific capacity and vertical line shaft turbine pump and submersible turbine pump

Other Water Quality Considerations

Total Dissolved Solids (TDS): Solids should not exceed 500 or 1000 mg/L
Chloride and Sulphate: concentration not to exceed 250 mg/L
Other Constituents: Presence of toxic heavy metals, fluoride, pesticides, and radioactivity with concentrations exceeding recognized standards

Well Hydraulics

Definitions: Static water level, Pumping level, Drawdown, Cone of depression, Radius of influence, Permeability, Hydraulic Conductivity
Well Discharge Formulas: Formulas for aquifer calculations (Eq 5.1-5.3)

Water Quality Evaluation

Selection of well sites: criteria such as local hydrogeology, terrain, soil type, depth, thickness, water bearing zone, proximity to sewage and industrial facilities etc.
History of water, oil, and gas wells
Direction and rate of travel of groundwater
Minimum distances from pollution sources

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Description

This quiz covers various aspects of well drilling and inspection techniques, including the use of caissons, bored pipes, and inspection equipment. Test your knowledge on the maximum depths of drilled pipes, well abandonment guidelines, and essential features of drilling equipment.