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 Consider the reduced effectiveness of snow and frozen ground
Consider slope (e.g. is there enough distance available to accommodate design length based on
slope, is slope too severe)
Consider if VFS will work properly for large fields with natural drainageways and grassed
waterways
VFS should not be installed above a source area they are designed to protect
Installation
VFS should be installed on the contour of the lowest elevation of the source area to prevent
concentrated flow
Some grading may be necessary to alter natural drainages both above and below the VFS
A level spreader formed of material resistant to erosion can be used to disperse concentrated
flow into more shallow overland flow
Berms or diversions may be needed at 15 or 30m intervals to intercept and divert flow over the
VFS where flow along or parallel to the VFS is significant
Maintenance
Vegetation should be mowed and removed from the site to decrease nutrient export form the
VFS outlet
Carefully controlled grazing of the VFS may be considered to remove vegetation, especially if
conditions and effects are known
The effects of herbicides on adjacent fields or the VFS should be considered
Herbicide sprayers should be turned off when crossing the VFS or source areas
Changes in flow patterns or damage to the VFS by plows or equipment for site preparation
should be avoided.
Selected BMPs are described in Appendix 4.2A.
4.2-21
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