Wells

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Monitoring wells are frequently installed on infiltrating systems such as bioretention, bioswales, infiltration trenches and hybrids thereof. The two questions most frequently addressed are:

  1. How quickly is surface ponding being infiltrated beneath the surface?
  2. How quickly is the facility draining through exfiltration to native soils and/or through an underdrain?

Shallow wells[edit]

To measure the depth of ponding and the rate at which the ponding water infiltrates, install a shallow well with a water level logger:

  • Use a perforated pipe (a piezometer) that will allow surface water to enter the well but will help prevent sediment from accumulating within it.
  • Locate the well where ponding occurs first - near the inlet or the lowest point in the feature.
  • Measure where the ground surface is relative to where you will be taking your water level measurements.
  • Ensure there is a small reservoir in the well to keep your level probe submerged in dry conditions. This practice will also help with calibration.

Deeper wells[edit]

Some LID features which are designed to retain water during precipitation events store stored within the media that makes up the LID feature (e.g. permeable pavement will be on top of a gravel bed where water can be stored). To measure the amount of water retention in a monitoring well, install a water level logger:

  • Install the well while the feature is being constructed or undergoing major maintenance.
  • If there is an underdrain in the feature, make sure the bottom of the well reaches below it.
  • Install the well so that surface water will not impact the water level within the well. A standard monitoring well casing over the well pipe should be sufficient.
  • If possible, measure the depth of the underdrain. Having this measurement helps determine when water is percolating into the underdrain.
  • Ensure there is a small reservoir in the well to keep your level probe submerged in dry conditions.
  • Where possible, wells for measuring water levels within permeable pavement systems should be outside of trafficked areas.