Certification Action Line — Answers — August 2014

Aug. 1, 2014

Answers from questions about groundwater.

1. d. Aquifers are the natural underground layers of porous, water-bearing materials (sand, gravel, sandstones, etc.) usually capable of yielding a large amount or supply of water. To qualify as an aquifer, an underground formation must have 1) porosity, area and thickness sufficient to store an adequate water supply; 2) adequate specific yield to allow the stored water to drain into a well; and 3) hydraulic transmissivity to permit a well to drain water from the aquifer fast enough to meet flow requirements.

2. a. Of these choices, the Earth’s groundwater comprises the greatest fresh water quantity, about 2,000 cubic miles. However, glaciers and ice caps hold about 7,000 cubic miles of fresh water. Fresh water lakes comprise about 30 cubic miles, rivers about 0.3 cubic miles and the atmosphere about 3.1 cubic miles of fresh water. The world’s oceans and seas contain about 317,000 cubic miles of saline water.

3. c. According to the 2007 U.S. Census, over 15 million U.S. households obtain their water from a private well.

4. b. Even though the number of groundwater sources of water supply far outnumber the count of surface water intakes, large water users, such as major metropolitan water utilities, and large industrial users most frequently tap a large lake, river or reservoir supply.

5. a, b, c and d. All four of these sources are common causes of groundwater contamination. Storage tanks, especially underground storage tanks, can leak contents such as gasoline. The U.S. Environmental Protection Agency has a special program to deal with leaking underground storage tanks; it is termed LUST. Abandoned wells, which were not properly plugged, serve as direct conduits for surface water drainage and sometimes intentional disposal sites to groundwater. Pumping of an aquifer beyond its ability to be recharged naturally with fresh water can induce encroachment of salt water from nearby saline aquifers or the ocean. Irrigation waters can cause extra leaching of fertilizers, pesticides and total dissolved solids to the water table.

6. d.   

7. False. Never mix calcium and sodium hypochlorite directly together. Extreme heat and an explosion could occur.

8. a. Volume of water = 3.1416 x (3 inches)² x (45 feet) x (7.48 gallons per cu. ft.) ÷ (144 sq. in./cu. ft.) = 66 gallons of water in the well. Amount of sodium hypochlorite bleach = (66 gallons) x (100 mg/L) ÷ (52,500 mg/L) x (16 cups per gallon) = two cups.

9. True. Check valves are installed on the discharge side of the well pump to act as a shutoff valve when the pump stops. This keeps pressurized water from flowing back down the pump column into the well and prevents draining of the systems or tank it’s being pumped to.

10. False. The function of each stage in a pump bowl assembly is to add pressure head; the volume capacity is almost constant for each stage and the combined assembly.

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