Stormwater Management Inspector Prep
UPDATED ACTUAL Questions and
CORRECT Answers
What are the types of disconnection allowed for rooftop disconnection? - CORRECT
ANSWER - 1) simple disconnection - rooftops and/or on-lot residential impervious
surfaces are directed to pervious areas
2) disconnection leading to an alternative runoff reduction practice adjacent to the roof (ex: soil
compost amended filter path)
Why have a rooftop disconnection to an alternative practice? - CORRECT ANSWER - -lot
size too small
-filter width is too narrow
-need more water quality credit
Functions provided by simple rooftop disconnection - CORRECT ANSWER - -annual
runoff volume reduction
-total phosphorus mass load removal
-total nitrogen mass load removal
Alternative rooftop disconnection types - CORRECT ANSWER - -soil compost-amended
filter path
-dry-well or french drain
-rain-garden//front yard bioretention
-rainwater harvesting//cistern
-stormwater planter
How does sheet flow to a vegetated filter strip or conserved open space work? - CORRECT
ANSWER - Filter strips are vegetated areas that treat sheet flow delivered from adjacent
,impervious and managed turd areas by slowing runoff velocities and allowing sediment and
attached pollutants to settle and/or be filtered by the vegetation
Gravel diaphragm - CORRECT ANSWER - -pretreatment device
-maintains sheet flow
-not necessary if contributing drainage area is solely turf
-trench is 2 ft. wide and 1 ft. deep
-runs on same contour at top of filter strip
-drop at least 3 inches
-fabric between gravel and soil
Engineered level spreader - CORRECT ANSWER - -forebay: max. 3ft. deep, transition to
1 ft. at level spreader lip
-level spreader lip - concrete, wood, or prefabricated metal, with a well anchored footer, or other
accepted rigid, non-erodible material
-location: 3-6 inches above downstream natural grade to avoid turf buildup
-3ft. of VDOT #3 stone, underlain by filter fabric just below spreader
-vegetated receiving area must be stabilized
Construction sequence for conserved open space - CORRECT ANSWER - - no clearing,
grading, heavy equipment
-protect area during construction
-prevent sediment discharge
-mark limits of disturbance
-drainage area stabilized
-grade with tracked vehicles
-install gravel diaphragm and/or level spreader
-mark filter boundaries
-keep vehicles out
, -stockpile topsoil for later use
-divert construction runoff
-install gravel diaphragm and/or level spreader
-grade with tracked vehicles
-open to runoff once stabilized
Maintenance of Vegetated Filter Strips - CORRECT ANSWER - minimal; spring cleanup,
regular mowing, check dam repairs, and other methods of maintaining hydraulic efficiency
Grass channel design criteria - CORRECT ANSWER - -the bottom width of the channel
should be between 4-8 feet wide
-the channel side-slopes should be 3H:1V or flatter
-the maximum total contributing drainage area to any individual grass channel is 5 acres
-the longitudinal slope of the channel is <4%
-max flow velocity of channel must be <1ft/sec during a 1 inch storm event
-the dimensions of the channel should ensure that flow velocity is non-erosive during the 2-yr
and 10-yr design storm events and the 10-yr design flow is contained within the channel
Grass channel pretreatment - CORRECT ANSWER - -check dams
-tree check dams
-grass filter strip
-gravel or stone diaphragm
-gravel or stone flow spreaders
Check dams - CORRECT ANSWER - -Purpose: break-up slopes and increase time water
stays in channel
max desired height 12-18 in
-averaging ponding depth: 12 in
-armoring may be needed downstream
UPDATED ACTUAL Questions and
CORRECT Answers
What are the types of disconnection allowed for rooftop disconnection? - CORRECT
ANSWER - 1) simple disconnection - rooftops and/or on-lot residential impervious
surfaces are directed to pervious areas
2) disconnection leading to an alternative runoff reduction practice adjacent to the roof (ex: soil
compost amended filter path)
Why have a rooftop disconnection to an alternative practice? - CORRECT ANSWER - -lot
size too small
-filter width is too narrow
-need more water quality credit
Functions provided by simple rooftop disconnection - CORRECT ANSWER - -annual
runoff volume reduction
-total phosphorus mass load removal
-total nitrogen mass load removal
Alternative rooftop disconnection types - CORRECT ANSWER - -soil compost-amended
filter path
-dry-well or french drain
-rain-garden//front yard bioretention
-rainwater harvesting//cistern
-stormwater planter
How does sheet flow to a vegetated filter strip or conserved open space work? - CORRECT
ANSWER - Filter strips are vegetated areas that treat sheet flow delivered from adjacent
,impervious and managed turd areas by slowing runoff velocities and allowing sediment and
attached pollutants to settle and/or be filtered by the vegetation
Gravel diaphragm - CORRECT ANSWER - -pretreatment device
-maintains sheet flow
-not necessary if contributing drainage area is solely turf
-trench is 2 ft. wide and 1 ft. deep
-runs on same contour at top of filter strip
-drop at least 3 inches
-fabric between gravel and soil
Engineered level spreader - CORRECT ANSWER - -forebay: max. 3ft. deep, transition to
1 ft. at level spreader lip
-level spreader lip - concrete, wood, or prefabricated metal, with a well anchored footer, or other
accepted rigid, non-erodible material
-location: 3-6 inches above downstream natural grade to avoid turf buildup
-3ft. of VDOT #3 stone, underlain by filter fabric just below spreader
-vegetated receiving area must be stabilized
Construction sequence for conserved open space - CORRECT ANSWER - - no clearing,
grading, heavy equipment
-protect area during construction
-prevent sediment discharge
-mark limits of disturbance
-drainage area stabilized
-grade with tracked vehicles
-install gravel diaphragm and/or level spreader
-mark filter boundaries
-keep vehicles out
, -stockpile topsoil for later use
-divert construction runoff
-install gravel diaphragm and/or level spreader
-grade with tracked vehicles
-open to runoff once stabilized
Maintenance of Vegetated Filter Strips - CORRECT ANSWER - minimal; spring cleanup,
regular mowing, check dam repairs, and other methods of maintaining hydraulic efficiency
Grass channel design criteria - CORRECT ANSWER - -the bottom width of the channel
should be between 4-8 feet wide
-the channel side-slopes should be 3H:1V or flatter
-the maximum total contributing drainage area to any individual grass channel is 5 acres
-the longitudinal slope of the channel is <4%
-max flow velocity of channel must be <1ft/sec during a 1 inch storm event
-the dimensions of the channel should ensure that flow velocity is non-erosive during the 2-yr
and 10-yr design storm events and the 10-yr design flow is contained within the channel
Grass channel pretreatment - CORRECT ANSWER - -check dams
-tree check dams
-grass filter strip
-gravel or stone diaphragm
-gravel or stone flow spreaders
Check dams - CORRECT ANSWER - -Purpose: break-up slopes and increase time water
stays in channel
max desired height 12-18 in
-averaging ponding depth: 12 in
-armoring may be needed downstream
