This set of Civil Engineering Drawing Multiple Choice Questions & Answers (MCQs) focuses on “Wells”.
1. An _________ is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt) from which groundwater can be extracted using a water well.
Explanation: An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt) from which groundwater can be extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology.
2. If the impermeable area overlies the aquifer, pressure could cause it to become a confined aquifer.
Explanation: Confined aquifers are those in which an impermeable dirt/rock layer exists that prevents water from seeping into the aquifer from the ground surface located directly above.
3. Shallow or unconfined wells are completed in the uppermost saturated aquifer at that location (the upper unconfined aquifer).
Explanation: Unconfined aquifers are those into which water seeps from the ground surface directly above the aquifer.
4. Production or pumping wells, are often smaller diameter wells used to monitor the hydraulic head or sample the groundwater for chemical constituents.
Explanation: Monitoring wells or piezometers, are often smaller diameter wells used to monitor the hydraulic head or sample the groundwater for chemical constituents. Piezometers are monitoring wells completed over a very short section of aquifer. Monitoring wells can also be completed at multiple levels, allowing discrete samples or measurements to be made at different vertical elevations at the same map location.
5. Drilled wells can be excavated by simple hand drilling methods.
Explanation: (augering, sludging, jetting, driving, hand percussion) or machine drilling (rotary, percussion, down the hole hammer). Deeprock rotary drilling method is most common. Rotary can be used in 90% of formation types.
Drilled wells can get water from a much deeper level than dug wells can—often down to several hundred metres.
6. Water wells typically range from 3 to 18 metres (10–60 ft) deep, but in some areas can go deeper than 200 metre.
Explanation: Water wells typically range from 3 to 18 metres (10–60 ft) deep, but in some areas can go deeper than 900 metres (3,000 ft).
7. Well development is the process of removing fine sediment and drilling fluid from the area immediately surrounding the perforations.
Explanation: This increases the well’s ability to produce water and maximize production from the aquifer. If the aquifer formation does not naturally have any relatively coarse particles to form a filter, it may be necessary for the driller to install an artificial filter pack. This pack is placed around the screen or perforations so the well can be developed. For example, this procedure is necessary when the aquifer is composed of fine sand and the individual grains are uniform.
8. Drilled wells are smaller in diameter, usually ranging from 10-20 cm (4-8 in.).
Explanation: These are completed to much greater depths than bored wells, up to several hundred metres. The producing aquifer is generally less susceptible to pollution from surface sources because of the depth. Also, the water supply tends to be more reliable since it is less affected by seasonal weather patterns.
9. Sealing the well protects the well’s producing zone from contamination.
Explanation: The diameter of the borehole is usually slightly larger than the casing being installed. The space between the borehole and the casing is called the annulus of the well or the annular space. It must be sealed to prevent any surface contamination from migrating downward and contaminating the water supply. A properly sealed annulus also prevents any mixing of poor quality water from upper aquifers with water from the producing aquifer of the well.
10. In the following figure, Part 1 represents?
a) inlet pipe
c) drainage pipe
d) outlet pipe
Explanation: A water well is an excavation or structure created in the ground by digging, driving, boring, or drilling to access groundwater in underground aquifers. The well water is drawn by a pump, or using containers, such as buckets, that are raised mechanically or by hand.
11. In the following figure, Part 3 represents?
a) rigid wall
b) water storage tank
c) garbage tank
d) water treatment tank
Explanation: A water tank is a container for storing water. Water tanks are used to provide storage of water for use in many applications, drinking water, irrigation agriculture, fire suppression, agricultural farming, both for plants and livestock, chemical manufacturing, food preparation as well as many other uses. Water tank parameters include the general design of the tank, and choice of construction materials, linings. Various materials are used for making a water tank: plastics (polyethylene, polypropylene), fiberglass, concrete, stone, steel (welded or bolted, carbon, or stainless).
12. In the following figure, Part 2 represents?
c) jet pump with pressure switch
d) power source
Explanation: A pump-jet, hydrojet, or water jet is a marine system that creates a jet of water for propulsion. The mechanical arrangement may be a ducted propeller (axial-flow pump), a centrifugal pump, or a mixed flow pump which is a combination of both centrifugal and axial designs. The design also incorporates an intake to provide water to the pump and a nozzle to direct the flow of water out of the pump.
13. __________ wells are constructed when low yielding groundwater sources are found relatively close to the surface, usually under 30 m (100 ft.). These are constructed using a rotary bucket auger.
Explanation: They are usually completed by perforating the casing (also called cribbing) or using a sand screen with continuous slot openings (Bored Well). One advantage of bored wells is the large diameter of the casing, from 45-90 cm (18-36 in.). It provides a water storage reservoir for use during peak demand periods. A disadvantage of utilizing a shallow groundwater aquifer is that it generally relies on annual precipitation for recharge. Water shortages may occur following long dry periods in summer and extended freeze up during winter months. It can also be more susceptible to contamination from surface land-use activities.
14. There are two primary methods of drilling cable tool and ________
Explanation: Rotary drilled wells are constructed using a drill bit on the end of a rotating drillstem. Drilling fluid or air is circulated down through the drillstem in the hole and back to the surface to remove cuttings. Rotary drilling rigs operate quickly and can reach depths of over 300 m (1000 ft.), with casing diameters of 10-45 cm (4-18 in.).
Cable tool drilled wells are constructed by lifting and dropping a heavy drill bit in the bore hole. The resulting loose material, mixed with water, is removed using a bailer or sand pump. This method, also called percussion drilling, reaches depths up to 300 m (1000 ft.). Well diameters can range from 10-45 cm (4-18 in.). The drilling rate is typically much slower than for a rotary rig, but when aquifers are low yielding, they may be more easily identified using this method.
15. A commercially manufactured, vermin-proof _________ is the only type of cap designed to keep animals, insects and contaminants from entering your well.
a) animal cap
b) security cap
c) danger cap
d) well cap
Explanation: It comes equipped with rubber gaskets and screened vents to ensure vermin stay out and air can circulate through. Coverings for large diameter wells must be custom made because of their larger size. Ideally they should be made of steel, or fibreglass or plastic that is stamped for potable water use.
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