Changes

It is often prudent to assume that maintenance will be intermittent and to include a clogging factor into engineering calculations to account for periods in which the debris has not been removed.  

It is often prudent to assume that maintenance will be intermittent and to include a clogging factor into engineering calculations to account for periods in which the debris has not been removed.  

A suggested value of 0.5 is often adopted. This is equivalent to 50 % of the cross-section of the structure being clogged during the flow being calculated. Note though that in the orifice equation (for example) the clogging factor goes up to indicate that 100 % of the flow can pass when factor = 1 and the factor goes down as the device clogs.  

A suggested value of 0.5 is often adopted. This is equivalent to 50 % of the cross-section of the structure being clogged during the flow being calculated. Note though that in the [[orifices|orifice]] equation (for example) the clogging factor goes up to indicate that 100 % of the flow can pass when factor = 1 and the factor goes down as the device clogs.  

e.g. In the image on the left 23 % of the grate is impassable. The clogging factor is 1.00 - 0.23 = 0.77.  

e.g. In the image on the left 23 % of the grate is impassable. The clogging factor is 1.00 - 0.23 = 0.77.  

==Geotextiles/filter fabric==

==Geotextile or filter fabric==

*Clogging of [[filter fabric]] has been observed in many field studies, e.g. ''"outflow ceases while water is still ponded above the drainage layer is most likely due to fines clogging the fabric and the need for more hydraulic head for the water to pass through the fabric"''<ref>Willard, L.L., T. Wynn-Thompson, L. H. Krometis, T. P. \ Badgley, and B. D. Neher. 2017. “Does It Pay to Be Mature? Evaluation of Bioretention Cell Performance Seven Years Postconstruction.” Journal of Environmental Engineering 143 (9).</ref>

*Clogging of [[filter fabric]] has been observed in many field studies, e.g. ''"outflow ceases while water is still ponded above the drainage layer is most likely due to fines clogging the fabric and the need for more hydraulic head for the water to pass through the fabric"''<ref>Willard, L.L., T. Wynn-Thompson, L. H. Krometis, T. P. \ Badgley, and B. D. Neher. 2017. “Does It Pay to Be Mature? Evaluation of Bioretention Cell Performance Seven Years Postconstruction.” Journal of Environmental Engineering 143 (9).</ref>

==Pipes==

==Pipes==

Some clogging of perforated [[pipes]] is likely to occur between maintenance visits. As mentioned above a clogging factor of 0.5 is often applied. See [[Flow through perforated pipe]].  

Some clogging of perforated [[pipes]] is likely to occur between maintenance visits. As mentioned above a clogging factor of 0.5 is often applied. See [[Flow through perforated pipe]].  

 

Various opinions are offered about how to mitigate the accumulation of sediment. The appropriate solution may depend on whether the water is flowing into the pipe (see [[underdrains]]), or out of the pipe as in [[exfiltration trenches]].

Various opinions are offered about how to mitigate the accumulation of sediment. The appropriate solution may depend on whether the water is flowing into the pipe (see [[underdrains]]), or out of the pipe as in [[exfiltration trenches]].