Talk:Infiltration

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Infiltration tests must be undertaken at the location, depth and with a head of water that replicates the proposed design.

Suggested safety factors to be applied to measured percolation rate when designing infiltration facilities

Catchment area	Consequence of failure
	No damage or inconvenience	Minor damage or inconvenience to external structures (e.g. ponding in parking lot)	Significant damage to buildings or infrastructure (e.g. flooding damage)
<100 m2	1.5	2	10
100 - 1000 m2	1.5	3	10

Example

Where the mean infiltration rate measured at the proposed bottom elevation of the BMP is 30 mm/hr, and the mean infiltration rate measured in an underlying soil horizon within 1.5 m of the bottom is 12 mm/h:

$ratio={\frac {q_{bottom}}{min\ q_{within1.5m}}}\ =\ {\frac {30}{12}}\ =2.5$

From the table the SCF is 3.5, and the design infiltration rate can be calculated:

$q'={\frac {q}{SCF}}\ =\ {\frac {30}{3.5}}=\ 8.6\ mm/hr$

The land draining to a single reference point (usually a structural BMP); similar to a subwatershed, but on a smaller scale.

The rate at which stormwater percolates into the subsoil measured in inches per hour.

Best management practice. State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include: source, conveyance and end-of-pipe controls.