Grade 4 Collection Systems Practice Questions

What does 'I&I' refer to in a collection system?

• AInspection and installation
• BInflow and infiltration
• CInterceptor and interconnection
• DInfluent and industrial waste

Before entering a manhole or wet well classified as a confined space, what must be done first?

• ANothing extra is required
• BTest and monitor the atmosphere for oxygen levels, toxic gases, and flammability, per confined-space entry procedures
• COnly wear a hard hat
• DNotify the nearest customer

A sewer line drops 2 feet in elevation over a run of 400 feet. What is the slope, expressed as a percentage?

• A0.05%
• B0.5%
• C5%
• D50%

Gravity sewers are designed to maintain a minimum 'self-cleansing' velocity primarily to:

• AReduce construction costs
• BPrevent solids from settling and accumulating in the pipe
• CIncrease water pressure
• DReduce odor complaints only

What is the purpose of high-velocity jetting (hydro-jetting) in sewer maintenance?

• ATo disinfect the pipe
• BTo use high-pressure water to dislodge and flush out grease, roots, and debris from the pipe
• CTo measure pipe slope
• DTo seal pipe joints

What is the main purpose of CCTV (closed-circuit television) inspection of sewer lines?

• ATo measure water pressure
• BTo visually identify pipe defects, blockages, root intrusion, and structural problems inside the pipe
• CTo disinfect the pipe
• DTo measure chlorine residual

A rectangular wet well is 8 ft by 6 ft. How many gallons does each 1 foot of depth hold?

• A48 gal
• B359 gal
• C2,875 gal
• D48,000 gal

What is a common reason for rehabilitating (lining or coating) an existing manhole?

• ATo increase its diameter
• BTo repair corrosion damage (often from H2S/sulfuric acid attack) and restore structural integrity without full replacement
• CTo change its location
• DTo reduce inflow only

Tree root intrusion into sanitary sewers is typically caused by roots seeking:

• AOxygen escaping from the pipe
• BMoisture and nutrients through pipe joints or cracks
• CLight entering through manhole covers
• DThe warmth of the wastewater

A one-mile segment of 8-inch sewer pipe shows measured infiltration of 6,000 gallons per day. What is the infiltration rate in gpd per inch-diameter per mile?

• A75 gpd/in-mi
• B750 gpd/in-mi
• C6,000 gpd/in-mi
• D48,000 gpd/in-mi

A wet well has 1,200 gallons of drawdown volume between pump start and stop levels. The pump discharges at 300 gpm while the average inflow while it runs is 100 gpm. What is the pump run time per cycle?

• A3 minutes
• B4 minutes
• C6 minutes
• D12 minutes

A sanitary sewer overflow (SSO) discharges untreated wastewater to a nearby creek. What is generally required of the operator?

• ANo action needed if the overflow is small
• BReport the SSO per permit/regulatory requirements and take steps to stop it and clean up
• CWait until the next scheduled inspection to report it
• DOnly report overflows that reach a river, not a creek

Manning's equation is commonly used by collection system operators to estimate what?

• AThe chlorine dose needed for disinfection
• BThe flow capacity or velocity of a gravity sewer based on its slope, roughness, and cross-section
• CThe horsepower of a lift station pump
• DThe percent strength of a chemical solution

A lift station pump moves 400 gpm against a total dynamic head of 60 feet at 70% efficiency. What brake horsepower is required?

• A4.3 bhp
• B6.1 bhp
• C8.7 bhp
• D17.3 bhp

Which of the following is a common method for controlling hydrogen sulfide odor in a collection system?

• AIncreasing detention time so solids can settle
• BChemical addition (such as iron salts or calcium nitrate) or forced-air ventilation/scrubbing at problem locations
• CRemoving all manholes
• DReducing pipe slope

A force main is 3,000 feet long with a 12-inch internal diameter. Flow through the main is 700 gpm. About how long does it take wastewater to travel the length of the main?

• A6 minutes
• B12 minutes
• C25 minutes
• D50 minutes

A force main has an internal diameter of 8 inches (cross-sectional area ≈ 0.349 ft²) and carries a flow of 500 gpm. What is the velocity in the pipe?

• A0.8 ft/s
• B1.6 ft/s
• C3.2 ft/s
• D6.4 ft/s

Hydrogen sulfide (H2S) gas in collection systems is a major safety and infrastructure concern because it is:

• AHarmless, but it smells bad
• BToxic at high concentrations, flammable, and corrosive to concrete and metal (crown corrosion)
• COnly a concern in drinking water systems
• DBeneficial for reducing odor complaints

Excessive inflow and infiltration (I&I) during wet weather is a leading cause of sanitary sewer overflows because it:

• AReduces pipe capacity
• BAdds clear water volume that can exceed the collection system's hydraulic capacity, causing surcharging and overflows
• CIncreases chlorine demand
• DHas no effect on system capacity

What is a key reason collection system operators perform routine manhole inspections even when no problem has been reported?

• AIt isn't necessary once a line has been CCTV-inspected
• BTo proactively identify deterioration, blockage risk, or I&I sources before they cause a failure or overflow
• CTo increase water pressure
• DTo measure chlorine residual