Wells

This article gives tips on the design and installation of monitoring wells into LID practices. It does not address the much deeper wells used to monitor groundwater levels. Monitoring wells are frequently installed on infiltrating systems such as bioretention, bioswales, infiltration trenches and hybrids thereof. The two questions most frequently addressed are:

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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

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

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.

Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

The downward movement of water through the soil, the downward flow of runoff from the bottom of an infiltration BMP into the soil.

Loss of water from a drainage system as a result of percolation or absorption into the surrounding medium (e.g., the infiltration of water into the native soil through a perforated pipe wall as it is conveyed).

Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

Any form of rain or snow.

A perforated pipe used to assist the draining of soils.

An alternative practice to traditional impervious pavement, prevents the generation of runoff by allowing precipitation falling on the surface to infiltrate through the surface course into an underlying stone reservoir and, where suitable conditions exist, into the native soil.