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Quiz & test questions Grade 10 Careers & CTE

Wrackley Stormwater Inspector: Runoff, Basins, and Outfalls

A grade 10 careers quiz on the municipal stormwater inspector role, covering the rational method, detention basin sizing, roof runoff, and illicit discharge response.

Objectives

  1. Students will describe what a municipal stormwater inspector checks at construction sites and outfalls.
  2. Students will apply the rational method to compare peak runoff before and after paving.
  3. Students will compute detention storage and roof runoff volumes in gallons.

Vocabulary

Detention basin
A detention basin is a dug-out area that fills with stormwater during a storm and then slowly drains empty over hours or days. It holds the water back so streets and streams downstream do not flood.

Also: runoff coefficient, rational method, illicit discharge, outfall

Teacher overview

This 40-minute quiz is worth 30 points and checks whether students understand the work of a municipal stormwater compliance inspector. It mixes multiple-choice recall, short-answer judgment items, and five computation items on the rational method, detention storage, and roof runoff. The scenario is set in the town of Wrackley, a fictional community with a construction site under an active permit. One point is worth establishing before students begin. Storm drains and sanitary sewers are separate systems in most American communities, and the storm drain discharges to a creek or river without passing through a treatment plant. That is why an inspector watches outfalls for sediment plumes and soapy flows. Items 1 and 8 both depend on the distinction.

Wrackley Stormwater Inspector: Runoff, Basins, and Outfalls — Grade 10 Careers & CTE
Name: ____________________________ Date: ______________

Assessment

  1. (2 points) What does a municipal stormwater compliance inspector mainly do?
    • A) Runs the disinfection process at the wastewater treatment plant
    • B) Inspects construction sites and storm drain outfalls for sediment control and illegal discharges
    • C) Repairs broken water mains in the street
    • D) Reads the rain gauge at the airport for the weather service
  2. (2 points) Sediment is the most common pollutant an inspector writes up. Why is soil in runoff treated as pollution?
    • A) Soil dissolves and raises the hardness of drinking water
    • B) Suspended soil blocks light, smothers stream bottoms, and carries phosphorus and metals with it
    • C) Soil neutralizes chlorine in the drinking water system
    • D) Soil has no effect on streams but looks unpleasant
  3. (4 points) A fictional Wrackley construction site covers 4.2 acres of graded bare soil with an assumed runoff coefficient of 0.35. Using the rational method, which is Q equals C times i times A, find the peak runoff for a design storm intensity of 2.4 inches per hour. Give the answer in cubic feet per second, rounded to the nearest tenth.
  4. (4 points) When the same fictional site is finished, 1.8 acres of it will be parking lot with a runoff coefficient of 0.90. Using the rational method with the same storm intensity of 2.4 inches per hour, find the peak runoff from the parking lot alone, in cubic feet per second, rounded to the nearest tenth.
  5. (3 points) The site's detention basin is a rectangle 120 feet long and 60 feet wide, holding water to a depth of 4.0 feet. The fictional Wrackley permit requires at least 200,000 gallons of storage. Find the basin's volume in gallons, using 7.48 gallons per cubic foot.
  6. (3 points) The finished building will have an 18,000 square foot roof. Using the rainwater conversion of 0.623 gallons per square foot per inch of rain, find the runoff from that roof during a 1.2-inch storm. Round to the nearest gallon.
  7. (4 points) A sample taken entering the basin reads 320 mg/L of total suspended solids, and a sample leaving the basin reads 48 mg/L. Using the removal efficiency formula, which is influent minus effluent, divided by influent, times 100, find the basin's removal efficiency as a percent.
  8. (2 points) On a dry Tuesday with no rain for six days, the inspector finds gray, soapy water running from a storm drain outfall. What is the correct first action?
    • A) Ignore it, because soap is biodegradable
    • B) Record and sample the discharge, then trace the pipe upstream to find the source
    • C) Wait for the next rainstorm to dilute it
    • D) Report it to the drinking water plant operator for treatment
  9. (3 points) The inspector arrives after a storm and finds a silt fence knocked flat along the downhill edge of the site, with mud tracked into the street. Describe two things the inspector must document and one correction the inspector should require.
  10. (3 points) Name two different education or training routes into stormwater inspection work, and state one thing each route provides.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: B. The inspector checks construction sites and outfalls for sediment control and illegal discharges; plant operation, main repair, and weather observation belong to other roles.
  2. Answer: B. Suspended soil blocks light, smothers the gravel where insects and fish eggs live, and carries phosphorus and metals attached to the particles, so it is a pollutant rather than a nuisance.
  3. Answer: 3.5 cfs. Working the rational method, 0.35 times 2.4 equals 0.84, and 0.84 times 4.2 acres equals 3.528, which rounds to 3.5 cubic feet per second.
  4. Answer: 3.9 cfs. Working the rational method again, 0.90 times 2.4 equals 2.16, and 2.16 times 1.8 acres equals 3.888, which rounds to 3.9 cubic feet per second. The paved area is less than half the size of the original site yet sheds more water, because the coefficient rose from 0.35 to 0.90.
  5. Answer: 215,424 gallons. The basin holds 120 times 60 times 4.0, or 28,800 cubic feet, and 28,800 times 7.48 equals 215,424 gallons, which satisfies the permit's 200,000-gallon requirement.
  6. Answer: 13,457 gallons. Multiplying gives 18,000 times 1.2 times 0.623, which equals 13,456.8, rounding to 13,457 gallons.
  7. Answer: 85 percent. Subtracting gives 320 minus 48, or 272 mg/L removed, and 272 divided by 320 equals 0.85, which is 85 percent removal.
  8. Answer: B. A dry-weather flow with suds is a classic illicit discharge, so the inspector documents and samples it, then works upstream through the pipe network to find the connection that produced it.
  9. Answer: The inspector documents the failed control with photographs, the location and length of fence down, the date and time, the rainfall that preceded the visit, and the sediment tracked into the street. The required correction is to reinstall or replace the silt fence with the fabric trenched in and staked, and to sweep the tracked sediment out of the street rather than washing it into the drain. Accept any two documentation items with one sound correction.
  10. Answer: Accept any two distinct routes with a matching benefit. Reasonable answers include a two-year environmental technology or civil technology degree, which provides the hydrology and sampling coursework; a four-year degree in environmental science or civil engineering, which opens permit-writing and program-management roles; a certified erosion and sediment control inspector credential earned by exam and field experience; and moving over from construction or landscaping work, which provides direct knowledge of how sites are built.

Differentiation

Support

Provide a formula card with the rational method, the rectangular volume formula, the rainwater conversion, and the removal efficiency formula, each with one worked example from a different fictional site. Allow a calculator throughout, and let students answer item 9 with a labeled sketch plus short phrases.

Extension

Ask students to combine items 3 and 4 into a single argument: does finishing the fictional site make runoff better or worse, and what would the developer have to add to hold the difference on site? A strong answer notes that the runoff coefficient rises from 0.35 to 0.90 on the paved portion, so the basin is what holds the added volume back from the creek.

ELL supports

Pre-teach "runoff coefficient," "detention basin," "outfall," "illicit discharge," and "silt fence" with a labeled site drawing showing the graded area, the fence line, the basin, and the pipe to the creek. Provide a sentence frame for item 8: "This is an illicit discharge because ___, so the inspector should first ___."

Extensions

Have students walk the school grounds and sketch where rain leaves the property, marking every inlet and the direction water flows, then estimate the roof runoff from one building using the same conversion as item 6. Students can also read their own municipality's published stormwater permit, which nearly every city posts online, and list the inspection frequencies it requires. Comparing those real requirements with the fictional Wrackley permit shows how much local variation exists in an inspector's workload.