Determine percent manure pack:

Dn1 = percent reduction in TN concentration
(if < 0, Dn1 = 0)
A similar relationship was developed for channelized flow for grassed waterways functioning a
buffer areas (Young et al., 1982).
Dc2 = 15.95 + 0.033 Tc
(1.1.31)
Dp2 = 21.2 + 0.036 Tc
(1.1.32)
Dn2 = 25.5 + 0.047 Tc
(1.1.33)
Where:
Dc2 = percent reduction in COD concentration
(if 0, Dc2 = 0)
Dp2 = percent reduction in TP concentration
(if 0, Dp2 = 0)
Dn2 = percent reduction in TN concentration
TC = time of contact (sec) see equation 1.1.35
Where buffer areas are comprised of portions having overland flow through grassed
waterways, the net reduction in animal waste pollutant concentration is calculated below:
CR = CF x [1-(D1/100)] x [1-(D2/100)]
(1.1.34)
Where:
CR = net reduced pollutant concentration (mg/1)
CF = pollutant concentration at feedlot edge (mg/1)
D1 = reduction in pollutant concentration in overland flow (percent)
D2 = reduction in pollutant concentration in grassed waterway (percent)
If CR equal or exceeds 100 percent, complete attenuation of pollutant has occurred, and the
buffer strip is sufficient in removing any potential pollution hazard.
1.1-27