Low Impact Development Manual for Michigan - OSEH - University ...

• Guidance information, usually in written manual
form, for operating and maintaining filter strips,
should be provided to all facility owners and
tenants. Facility owners are encouraged to keep an
inspection log, for recording all inspection dates,
observations, and maintenance activities.
• Grass cover should be mowed to maintain a height
of 4-6 inches.
• Invasive plants should be removed on an annual
basis. Vegetative cover should be sustained at 85
percent and reestablished if damage greater than 50
percent is observed.
• If a filter strip exhibits signs of poor drainage,
periodic soil aeration or liming may help to
improve infiltration.
Winter Considerations
Filter strips often make convenient areas for snow storage.
Thus, vegetation should be salt-tolerant and the
maintenance schedule should include removing sand
buildup at the toe of the slope.
The bottom of the gravel trench (if used as the level
spreader) should be placed below the frost line to
prohibit water from freezing in the trench. The perforated
pipe in the trench should be at least eight inches in
diameter to further discourage freezing.
Other water quality options may be explored to provide
backup to filter strips during the winter, when pollutant
removal ability is reduced.
Cost
The cost of constructing filter strips includes grading,
sodding (when applicable), installing vegetation,
constructing a level spreader, and constructing a pervious
berm, if proposed. Depending on whether seed
or sod is applied, enhanced vegetation use or design
variations such as check dams, construction costs may
range anywhere from no cost (assuming the area was
to be grassed regardless of use as treatment) to $50,000
per acre. The annual cost of maintaining filter strips
(mowing, weeding, inspecting, litter removal, etc.)
generally runs from $100 to $1,400 per acre and may
overlap with standard landscape maintenance costs.
Maintenance costs are highly variable, as they are a
function of frequency and local labor rates.
Designer/Reviewer Checklist for Vegetated Filter Strips
Soil type and HSG category: __________________________________________________________________
ITEM YES NO N/A NOTES
Sheet flow provided?
Recommended slope ranges followed?
Appropriate length for soil, vegetation, and slope?
Slope of drainage area below five percent?
If not, is energy dissipation provided?
Length/area of incoming drainage appropriately limited?
Receiving vegetation considered?
Located in undisturbed virgin soil?
If not, will soil be properly compacted and stabilized?
Appropriate vegetation selected for stabilization?
Feasible construction process and sequence?
Soil compaction avoided or mitigated?
Erosion and sedimentation control provided to protect filter
strip during construction?
Maintenance accounted for and plan provided?
LID Manual for Michigan – Chapter 7 Page 298