Another method utilizes a pipe split in half lengthwise forming a semi-circular trough, laying it level across the filter width, and allowing liquid to fill and overflow this trough uniformly across the filter. Sections of level gated pipe across the filter width can also be used. The size of the overland flow area depends on soil characteristics and generally ranges from 1 to 2 times the feedlot area draining into the filter. The second type of vegetative filter is a channelized flow or grassed infiltration terrace. Successful channel filter treatment lengths in North Carolina have been at least 4 feet per cow.
Dual channels allow alternate dosing and drying.
These channels should not outlet directly into a stream or drainageway. Construction Extreme care should be taken during construction of a vegetative filter. Since infiltration is most important, every effort should be made to maintain soil integrity and permeability. Clay soils, in particular, should not be worked or compacted when wet. If it is impossible to use these precautions during construction, then a subsoiler should be used to break up hardpans or impermeable layers followed by seeding with a grass that has a deep root system.