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Pretreatment quiz

Answers below

1. Pretreatment practices designed to remove solids typically remove particles larger than
   1. 5 microns
   2. 10 microns
   3. 100 microns
   4. 300 microns
2. While the particle size distribution in runoff varies widely depending on factors such as land use, a typical median particle size for urban runoff is
   1. 1 micron
   2. 10 microns
   3. 75 microns
   4. 200 microns
3. Based on the first two questions (above), is the following statement accurate? “I put in a pretreatment practice and it is removing 100 pounds of sediment annually. I can therefore claim a 100 pound credit toward my TSS Total Maximum Daily Load.”
4. True or false: Minnesota does not certify specific pretreatment practices, but strongly recommends pretreatment practices be approved through Washington State’s TAPE or New Jersey’s NJCAT programs, or has undergone modeling with SHSAM.
5. Vegetated filter strips are effective pretreatment practices but, like any practice, have limitations. Which of the following is not a limitation for filter strips.
   1. They tend to require more space than other pretreatment practices, which often limits retrofit suitability.
   2. They are not easily accessible which makes maintenance more difficult.
   3. They tend to require more space than other pretreatment practices, which often limits retrofit suitability.
   4. During winter months, they will become frozen and covered by ice and snow to some extent, which diminishes their effectiveness if flows become channelized.
6. In general, which type of device is most suitable for ultra-urban settings?
   1. Forebay
   2. Vegetated filter strip
   3. Underground settling device
   4. Above-ground screening devices
7. True or false: Screening devices are among the most effective water quality pretreatment practices
8. In order to achieve maximum sediment removal, forebays are typically designed to contain what percent of the water quality volume?
   1. 5
   2. 10
   3. 25
   4. 50

Answers

1. 100 microns
2. 75 microns
3. Not accurate. Using data from a literature review and assuming pretreatment will remove particles down to 100 microns in diameter, a device removing 100 pounds of sediment would remove about 25% of the solids in runoff captured by the device.
4. True
5. (b) Vegetated filter strips are typically easy to access.
6. (c). Underground practices, in general, are more suitable for ultra-urban settings
7. False Screening devices are primarily designed to remove gross solids, including trash.
8. b

Green infrastructure O&M quiz (September 2021)

1. True or false: Snow storage is recommended in filtration and infiltration practices as a way of treating water and enhancing infiltration
2. Which of these is not a typical annual maintenance recommendation for bioretention practices?
   1. Regenerating the soil or media
   2. Removing and replacing dead plants
   3. Checking the BMP and associated piping/conveyances for clogging
   4. Assessing performance, such as observing drawdown times and observing evidence of flooding
3. What is the maximum recommended slope on a green roof (without reinforcement)?
   1. 1:2
   2. 2:10
   3. 2:12
   4. 2:20
4. True or false: Pretreatment practices should be installed prior to constructing the permanent BMP
5. True or false: The contributing drainage area to a BMP is the total impervious and pervious area contributing runoff to the BMP
6. True or false: A green infrastructure practice always includes vegetation
7. Why are design phase O&M considerations recommended?
8. What is the recommended frequency for vacuuming of permeable pavement?
   1. Biennially
   2. Annually
   3. Biannually
   4. Quarterly
9. Mulch is generally not recommended for an infiltration or filtration practice. Why?
   1. It introduces weeds to the practice
   2. It leaches phosphorus
   3. It introduces insect pests to the practice
   4. It can clog pipes, inlets, and outlets
10. Which of the following is not a recommended component of a site-specific O&M plan?
    1. The plan should contain a maintenance agreement
    2. The plan should provide any operating procedures related to the practices
    3. The plan should provide clear maintenance expectations, activities, and schedules
    4. The plan should identify who is responsible for the maintenance and the type of expertise that will be needed for distinct O&M activities
    5. The plan should include an anticipated budget for O&M activities
    6. The plan should include an example O&M inspection checklist and an example maintenance report

Answers

1. False. Snow storage is generally not recommended in filtration and infiltration practices. The stored snow can compact the soil or media and reduce hydrologic performance. There may also be water quality concerns, particularly with chloride from road salts.
2. Regenerating the soil or media should not be needed annually. Certain practices, such as compaction or accumulation of metals and salts, may require that soil or media be regenerated.
3. 2:12. For more information, link here.
4. True. Pretreatment practices can provide protection of the post-construction practice while it is being constructed. Pretreatment practices must be regularly maintained.
5. True, the contributing drainage area includes impervious and pervious areas draining to a practice. Link here.
6. False. Permeable pavement is the best example of a green infrastructure practice that does not include vegetation. Green infrastructure is designed to mimic nature and capture rainwater where it falls. Green infrastructure reduces and treats stormwater at its source while while also providing multiple community benefits such as improvements in water quality, reduced flooding, habitat, carbon capture, etc.
7. Considering operation and maintenance in the design phase can prevent or minimize O&M issues once the practice is constructed. Design phase considerations vary with the practice. Examples include ensuring the contributing area is not too large, the proper vegetation is selected, and the proper type and amount of pretreatment is identified.
8. Biannually, in spring and fall
9. (d) A bit of a trick question. Under certain conditions, any of these four can be problematic. However, the primary reason is that mulch clogs inlets, outlets, and pipes. Answer (d) is also the only statement that is not phrased as being always true.
10. (a) A maintenance agreement is a separate component and not part of the maintenance plan