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NCEES-PE-Civil-WRE : NCEES PE Civil Engineering: Water Resources and Environmental Exam

NCEES NCEES-PE-Civil-WRE Questions & Answers
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NCEES PE Civil: Water Resources and Environmental
NCEES - PE Civil Engineering - Water Resources and Environmental 2024
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Question 386:
A. 51,840 kg/day
B. 21,880 kg/day
C. 45,320 kg/day
D. 65,000 kg/day
Answer: A
Explanation: The BOD load can be calculated as:
BOD Load = Concentration × Flow Rate × Time
Convert mg/L to kg/m³:
Concentration = 200 mg/L = 0.2 kg/m3
Thus,
BOD Load = 0.2 kg/m3 × 3 m3/s × 86, 400 s = 51, 840 kg/day
An environmental engineer is assessing the impact of a sewage treatment plant on a nearby stream. If the plant discharges effluent with a biochemical oxygen demand (BOD) of 200 mg/L and the stream's flow is 3 m³/s, what is the total BOD load entering the stream from the plant in kilograms per day?
Question 387: A groundwater engineer is evaluating the effects of a contaminant plume in a confined aquifer. If the hydraulic conductivity is 20 m/day and the contaminant concentration decreases from 1,000 µg/L to 100 µg/L over a distance of 50 m, what is the attenuation factor? 0.1 0.5 0.7 10.0 C1 1000 μg/L Attenuation Factor = = = 10 C2 100 μg/L A civil engineer is assessing the effect of urban runoff on a stream's DO levels. If the stream's DO was 8 mg/L before the runoff event and dropped to 5 mg/L after, what is the percentage change in DO? A. 20% B. 25% C. 37% D. 35% Initial DO − Final DO Percentage Change = × 100 Thus, Percentage Change = 8 − 5 × 100 = 37.5% An environmental scientist is evaluating the impact of nutrients on a lake's water quality. If the lake has a volume of 1,000,000 m³ and the total phosphorus concentration is 0.2 mg/L, what is the total phosphorus load in kilograms? 0.2 kg C. 20 kg D. 200 kg Load = Concentration × Volume Convert concentration to kg/m³: Concentration = 0.2 mg/L = 0.0002 kg/m3 Thus, Load = 0.0002 kg/m3 × 1, 000, 000 m3 = 200 kg A groundwater model indicates that a well is experiencing a drawdown of 5 m after 12 hours of continuous pumping. If the well has a radius of 0.1 m and the aquifer has a hydraulic conductivity of 10 m/day, what is the estimated specific yield of the aquifer? 0.01 0.05 0.1 0.15 Specific Yield = Drawdown Thus, 5 m 1 Specific Yield = × = 0.05 12 × 3600 s 10 m/day A hydrogeologist is evaluating a confined aquifer that has a hydraulic conductivity of 25 m/day and a thickness of 30 m. If the aquifer is being recharged at a rate of 0.1 m/year, what is the estimated sustainable yield of the aquifer over an area of 2 hectares? A. 2000 m³/yr B. 1500 m³/yr C. 1600 m³/yr D. 1700 m³/yr Time 1 Sustainable Yield = Recharge Rate × Area Convert the recharge rate to meters: Recharge Rate = 0.1 m/yr Convert area to square meters: Area = 2 hectares = 20, 000 m2 Thus, Sustainable Yield = 0.1 m/yr × 20, 000 m2 = 2, 000 m³/yr An engineer is analyzing groundwater flow through a heterogeneous aquifer. The hydraulic gradient in one section of the aquifer is measured at 0.03, and the hydraulic conductivity is 12 m/day. What is the groundwater flow velocity in that section? A. 0.36 m/day B. 0.48 m/day C. 0.56 m/day D. 0.72 m/day v = K ⋅ i Where K is hydraulic conductivity and i is hydraulic gradient. Thus, v = 12 m/day × 0.03 = 0.36 m/day A well in an unconfined aquifer is pumped at a rate of 100 L/s. After 48 hours of continuous pumping, the water level in the well has dropped from 15 m to 10 m. What is the total drawdown experienced by the well? 2 m 3 m 4 m 5 m Drawdown = Initial Water Level − Final Water Level Thus, Drawdown = 15 m − 10 m = 5 m A civil engineer is studying the impact of a wastewater discharge on a river’s dissolved oxygen (DO) levels. If the river has a flow rate of 4 m³/s and the DO concentration downstream of the discharge is 5 mg/L, while the upstream concentration is 8 mg/L, what is the total mass of oxygen depleted over a 24-hour period? A. 1288 kg B. 1576 kg C. 1036 kg D. 1296 kg Mass Loss = (Upstream DO − Downstream DO) × Flow Rate × Tim Where: Mass Loss = (8 mg/L − 5 mg/L) × 4 m3/s × 86, 400 s Convert mg/L to kg/m³: Mass Loss = 3 mg/L × 4 × 86, 400 = 1036.8 kg Reduction = An environmental scientist is calculating the Total Maximum Daily Load (TMDL) for nitrogen in a river. The current nitrogen load is 2,200 kg/year, and the TMDL is set at 1,500 kg/year. What is the percentage reduction needed to meet the TMDL? A. 25% B. 32% C. 40% D. 50% Current Load − TMDL Reduction = × 100 Current Load Thus, 2200 − 1500 × 100 ≈ 31.82% A lake has a total phosphorus concentration of 0.15 mg/L. If the lake has a volume of 500,000 m³, what is the total phosphorus load in kilograms? A. 10.75 kg B. 11.25 kg C. 15.00 kg Load = Concentration × Volume Convert concentration to kg/m³: Load = 0.15 mg/L × 500, 000 m3 = 75 kg In a groundwater contamination study, a monitoring well shows a concentration of benzene at 5 µg/L. If the well extracts water at a rate of 10 L/min, what is the total mass of benzene extracted in a 30-minute sampling period? A. 0.15 mg B. 0.25 mg C. 0.50 mg D. 1.50 mg D. 75.0 kg Mass = Concentration × Flow Rate × Time Convert flow rate to L/h: Mass = 5 μg/L × 10 L/min × 30 min = 1, 500 μg = 1.5 mg pollutant influx is measured at 12 mg/L, what is the increase in BOD due to the pollutants? A. 4 mg/L B. 6 mg/L C. 8 mg/L D. 10 mg/L Increase in BOD = Post-Pollution BOD − Natural BOD Thus, Increase in BOD = 12 mg/L − 4 mg/L = 8 mg/L A groundwater model reveals that a well has a drawdown of 3 m after 24 hours of A civil engineer is evaluating a stream's health by assessing its biological oxygen demand (BOD). If the natural BOD of the stream is 4 mg/L and the BOD after a pumping at a rate of 80 L/s. If the well has a radius of 0.15 m, what is the specific capacity of the well in L/s/m? 15.33 L/s/m 26.67 L/s/m 10.00 L/s/m 12.00 L/s/m Discharge Rate Specific Capacity = Thus, 80 L/s Specific Capacity = ≈ 26.67 L/s/m 3 m An environmental engineer is assessing the impact of nutrient runoff on a pond. If the pond has a surface area of 1 hectare and receives 15 kg of phosphorus from runoff annually, what is the concentration of phosphorus in mg/L, assuming an average depth of 2 m? A. 0.15 mg/L B. 0.75 mg/L C. 91.00 mg/L D. 750 mg/L Area = 1 hectare = 10, 000 m2 The volume of the pond is: Volume = Area × Depth = 10, 000 m2 × 2 m = 20, 000 m3 Convert kg to mg: Concentration = 15 kg × 1, 000, 000 mg/kg = 750 mg/L discharge from a wastewater treatment plant, what is the total mass of oxygen lost in kilograms over 24 hours? A. 518.4 kg B. 288 kg C. 864 kg D. 1,728 kg Mass Loss = (Upstream DO − Downstream DO) × Flow Rate × Tim Thus, Mass Loss = (9 mg/L − 5 mg/L) × 1.5 m3/s × 86, 400 s Convert mg/L to kg/m³: Mass Loss = 4 mg/L × 1.5 m3/s × 86, 400s = 518, 400 mg = 518.4kg e In a water quality assessment, a river's total nitrogen concentration is measured at 12 mg/L. If the river has a flow rate of 2.5 m³/s, what is the total nitrogen load in kilograms per day? A. 1250 kg/day B. 1300 kg/day C. 1036 kg/day D. 1600 kg/day Load = Concentration × Flow Rate × Time Thus, Load = 12 mg/L × 2.5 m3/s × 86, 400 s = 1, 036, 800 mg = 1, 036.8 kgAnswer: D
Explanation: The attenuation factor is calculated as:
Question 388:
Answer: C
Explanation: The percentage change in DO is calculated as:
Question 389:
Answer: D
Explanation: The total phosphorus load can be calculated as:
Question 390:
Answer: B
Explanation: The specific yield can be calculated using the relationship:
Question 391:
Answer: A
Explanation: The sustainable yield can be estimated using:
Question 392:
Answer: A
Explanation: Groundwater flow velocity can be calculated using Darcy's law:
Question 393:
Explanation: The drawdown is calculated as:
Question 394:
Answer: D
Answer: C
Explanation: The mass of oxygen lost can be calculated as:
Question 395:
Answer: B
Explanation: The percentage reduction can be calculated as:
Question 396:
Answer: D
Explanation: The total phosphorus load can be calculated as:
Question 397:
Answer: D
Explanation: The total mass can be calculated as:
Question 398:
Answer: C
Explanation: The increase in BOD is calculated as:
Question 399:
Answer: B
Explanation: Specific capacity can be calculated using:
Question 400:
Answer: D
Explanation: Convert area to square meters:
Question 401:
Answer: A
Explanation: The mass of oxygen lost can be calculated as:
Question 402:
Explanation: The nitrogen load can be calculated as:
Answer: C
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