Hydrogeology hub

The Conservation Authorities Geoscience Group have prepared a guidance document which attempts to standardize the hydrogeological study requirements for development applications made to Conservation Authorities. It is a helpful guide for all low impact development applications which include infiltration.

It is provided with the caveat that not all sections or content are necessary or appropriate for every case. Pre-consultation with your Conservation Authority and municipality is strongly recommended in all cases.

Hydrogeological Assessment Submissions Conservation Authority Guidelines for Development Applications

Infiltration

The Ministry of the Environment are preparing advice on where and when to infiltrate rainwater and stormwater. Things to be mindful of are:

Karst

Diagram illustrating characteristics of karst formations and topography

Locations of karst topography in southern Ontario, Red = Known Karst; Orange = Inferred Karst; Yellow = Potential Karst

LID facilities designed to drain primarily by infiltration should not be located on karst formations or topographic features. Karst formations and topography are found in areas along the Niagara Escarpment, including the Bruce Peninsula, the Guelph/Rockwood/Elora area of Wellington County and in portions of eastern Ontario.

Karst formations that feature undetected sinkholes, trenches and caverns, can be dangerous

There is no one formula for defining a hazardous area associated with karst formations. Defining the “area of provincial interest” is a site-specific process. The size, extent and severity of the hazards depend on local conditions. Karst formation character and size depends on the pH of the infiltrating water, the rate at which the rock dissolves, number of fractures and fissures in the rock, distance the water will percolate from surface to water table and the presence of impermeable layers above or below the limestone/dolomite layers.

Karst formations can also be significant recharge zones for municipal supply aquifers

For example, the City of Guelph, whose drinking water supply is wholly groundwater, is known to be a direct recipient of significant recharge through the areas karst formations.

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 slow movement of water into or through a soil or drainage system.

Penetration of water through the ground surface.

Refers to the conditions in which an organism lives and survives or the conditions in which an organism resides. These conditions can be described as aspects of a “physical”, “social” or an “economic” environment, depending on the perspective perceived by the observer.

Surface runoff from at-grade surfaces, resulting from rain or snowmelt events.

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 upper surface of the zone of saturation, except where the surface is formed by an impermeable body.

Subsurface water level which is defined by the level below which all the spaces in the soil are filled with water; The entire region below the water table is called the saturated zone.

The addition of water to ground water by natural or artificial processes.

The infiltration and movement of surface water into the soil, past the vegetation root zone, to the zone of saturation or water table.

Layer of rock or soil that holds or transmits water.