Littoral sands

Hydrogeological Context

Version Metadata
0ea68738-1bd5-4755-9ed6-ce341fd5f47c
Project
Portneuf

Datasets

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Littoral sands unit description

Update:2014-01-29
The territory sections, where littoral sands are present count three aquifers: Precambrian bedrock aquifer, sedimentary formations aquifer and surficial littoral sands aquifer. The Precambrian bedrock is massive and little fractured, showing an unproductive aquifer. Sedimentary formations are highly fractured and shales are very brittle, demonstrating good potential aquifer. These units are covered by till layer. The till is overlain by a thick Sea Champlain marine silts and clays unit, followed by littoral sands. The littoral sands aquifer is located along the deltaic sand and gravel deposits. The littoral sands have a high permeability, giving a high aquifer potential. However, the thickness of the littoral sand deposits is thin, thus limiting the amount of usable water. This type of aquifer is exploited for private wells, mostly shallow wells or wellpoint. The water table is under unconfined conditions, thus the aquifer is vulnerable to surface contamination. The groundwater type is calcic bicarbonate/calcic sulfate, showing low mineralization.
Physiography
Hydrogeological regionSt. Lawrence Platform
Hydrogeological context
ReliefThe littoral sands aquifer is mainly located at low altitudes between Sainte-Anne River and the St. Lawrence River. Some northeast sections between Sainte-Anne and Jacques-Cartier rivers have higher elevations. The terrain is fairly flat.
Area238.00 km2
Lithology
DescriptionThe rock formations underlying littoral sands belong to the Precambrian bedrock or sedimentary formations. The sections of the Precambrian bedrock considered are mainly composed of gneiss and gabbro. The granodiorite gneiss is the dominant unit. Sedimentary formations include limestones of the Trenton Group and shales of the Utica Group. The rock formations are covered by a till, overlain by marine silts and clays of the Champlain Sea followed by littoral sands.
Source
Aquifer
AquifersList of aquifers surficial littoral sand aquifer

Unit properties

Surficial aquifer media
Typical value:porous
Description littoral sands
Bedrock aquifer media
Typical value:karst - fractured
Description The igneous metamorphic rocks and the sedimentary rocks are the hydrogeological units underlying littoral sands. The Precambrian rocks don't represent productive aquifer. The limestones of the sectors of Pont-Rouge, Saint-Casimir and Saint-Marc-des-Carrieres show a beginning of karstification.
Confinement
Typical value:unconfined
Surficial sediment thickness
Description The littoral sands unit is thin. The thickness is mostly around 0-2.5 m, but locally there are some deposits that have a thickness of 5-10 m.
Methode Universal kriging interpolation of 179 borehole data
Hydrogeological unit thickness
Description The littoral sands unit is thin. The thickness is mostly around 0-2.5 m, but locally there are some deposits that have a thickness of 5-10 m.
Methode Universal kriging interpolation of 179 borehole data
Well depth
25.45 m Range: [0 to 121.9] m
Groundwater depth
0.75 m Range: [0 to 6.86] m
Surficial unit hydraulic conductivity
0.000073 m/s
Description The hydraulic conductivity is 7.3E-5 m/s
Methode Hazen formula, based on 44 samples
Regional precipitation
1121.5 mm/y Range: [1063.1 to 1168.2] mm/y
Methode Precipitation data are from Environment Canada. The value represents the average of the climate normals (1981-2010) measured on the stations distributed in or near the hydrogeological unit. The stations were selected so the average precipitation is as representative as possible of the whole hydrogeological unit.
Hydrogeological unit potential
Description The aquifer potential is good, but it's limited because of the small thickness of the sediments.
Groundwater usage
Typical value:domestic
Description Residents who live in this area get their drinking water from shallow wells or wellpoint.
Aquifer vulnerability
5 Range: [0 to 6]
Groundwater Quality
Description The water type is calcic bicarbonate / calcic sulfate, showing low mineralization.