10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
These 10 free MGWC questions are organized by exam domain, so you can see how each part of the Master Ground Water Contractor blueprint is tested. Reveal the answer and explanation under each question.
An engineered filter-pack specification requires the largest available screen slot that retains at least 90% of the pack by mass. Sieve analysis reports 3% passing a 0.015-inch opening, 7% passing 0.020 inch, 14% passing 0.025 inch, and 23% passing 0.030 inch. The available screens otherwise have identical construction. Which slot size should be specified?
Correct answer: B - 0.020 inch
During mud-rotary drilling, Marsh funnel time rises from 42 to 58 seconds per quart at the same sample temperature. Properly taken mud-balance readings remain 9.0 lb/gal. With circulation stopped, the fluid column has the same vertical height and uniform density as before. A helper says the thicker mud must now exert more fluid-column hydrostatic pressure at the bottom. Which response is accurate?
Correct answer: A - Hydrostatic pressure is unchanged because fluid density and vertical column height are unchanged.
A submersible pump must deliver 20 gpm at 50 psig to a tank connection 10 ft above the wellhead. Water stands 50 ft below the wellhead at rest and 90 ft below it while pumping at 20 gpm. The pump intake is set at 180 ft. Total pipe and fitting losses at the required flow are 19.5 ft. Neglect velocity-head differences and use 2.31 ft of water per psi. Which duty point should be used for pump selection?
Correct answer: C - 20 gpm at 235 ft of total dynamic head
Testing of yield and usable borehole storage shows that a rural household's well can meet total daily demand but cannot deliver the short morning peak. Between peaks, the well can refill a suitably sized reservoir. The existing pressure tank cannot cover the deficit anywhere within its permitted pressure range. Select the design that addresses both water availability and household pressure.
Correct answer: D - Use sanitary atmospheric storage with level-controlled filling and a booster pump for household pressure.
Before submitting a well-construction bid, the owner reviews $27,000 in direct job costs and $3,000 in allocated overhead. Neither figure includes profit, and no other costs apply. The estimator proposes $36,000, calling it a 20% margin. The owner requires profit equal to 20% of the selling price after both cost categories. What selling price is required?
Correct answer: D - $37,500
At 240 ft, a new well has not reached the agreed yield. The signed contract expressly authorizes drilling to 300 ft at the stated unit rate when yield is inadequate; only work beyond 300 ft requires another written approval. The hole is stable, the permit allows this depth, and the work remains within the approved budget. The owner cannot be reached. What instruction should the superintendent give now?
Correct answer: C - Continue under the existing written authorization and document the additional work.
A contractor is reporting higher accrual-accounting profit but repeatedly struggles to fund payroll. Completed, accepted jobs have been invoiced, yet overdue receivables are increasing. Inventory, debt payments, and equipment purchases have not increased. Suppliers are still paid on schedule. Which change most directly targets the recurring operating cash shortage?
Correct answer: B - Pursue overdue collections and negotiate progress billings for future projects.
An irrigation customer reports weak pressure. At 20 gpm, verified gauges read 62 psig immediately before a cartridge filter and 36 psig immediately after it. The clean filter previously lost 3 psi at that same flow. Pump performance and pumping water level match the commissioning records. Where should corrective work begin?
Correct answer: B - Service the filter element and repeat the pressure measurements at 20 gpm.
A three-phase submersible delivered normally before its starter was replaced. Immediately afterward, flow and developed pressure were substantially lower. No piping or valve settings changed, submergence is adequate, and all three supply voltages and currents are balanced. The motor runs without tripping. The investigation should first test for:
Correct answer: A - Reversed motor rotation caused by the phase sequence after reconnection.
A family uses a private well to prepare formula for a two-month-old infant. A laboratory reports nitrate at 16 mg/L as nitrogen; the bacterial sample is negative. The family asks whether boiling the water will make it suitable for formula. Which advice addresses the actual hazard?
Correct answer: D - Use verified nitrate-safe water for formula while arranging appropriate treatment and follow-up testing.
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