Supporting documents - Renfrewshire Council

Goodson Associates
7.5 Hydrogeology
Proposed Store Development, Wallneuk Road, Paisley - 9692
Published hydrogeological records 13,14 show the site to be underlain by the
Carboniferous Dinantian and Namurian Calciferous Sandstone Measures, in
which groundwater flow is predominantly in fissures and other discontinuities.
These rocks typically can potentially exhibit a high primary permeability or
contain other formations of similar permeabilities. Borehole yields are
generally moderate although and not greater than 10 l/s. Significant volumes
can often be encountered within disused mine workings and shafts although
the quality is often poor. It is considered that underlying solid strata are
unlikely to harbour significant ground water although may be important proving
base flow to nearby water courses. Reference to the Renfrewshire Council
Contaminated Land Inspection Strategy Document confirms that formations of
Carboniferous strata rarely provide sufficient volumes of groundwater for
potable extraction, but are an important source in maintaining surface water
(rivers) base flows.
The soils overlying the site are classed as “soils of moderate leaching
potential” with a moderate ability to attenuate diffuse source pollutants and in
which contaminants with a propensity to enter the liquid phase may percolate
rapidly. It is likely that infiltration of contaminants would be low. Given the
relatively impermeable nature of the overlying impermeable tarmac surfacing
and underlying glacial soils it is not likely that significant groundwater
resources are present under the site. Pockets of perched groundwater may
exist but are not expected to be extensive.
The area is considered a low hydrogeological risk, due to the moderate
permeability of the superficial deposits and impermeable surface made
ground (tarmac) layer. The possibility of impacted shallow groundwater cannot
be precluded given the previous industrial land uses.
7.6 Hydrology
The majority of the site is anticipated to be covered by hardstanding,
roadways and buildings, this reducing infiltration and increasing surface run
off. Adequate drainage and (if necessary) water attenuation/treatment
systems (SUDS) will mitigate any additional run off from the site. As indicated
by The Scottish Environmental Protection Agency (SEPA) website 15 ’ 16 which
enables a search of river classifications and associated water quality
indicators, the nearest classified non estuarine surface water feature is the
White Cart Water. Located approximately 300m to the southwest of the site
boundary, this is classed as B “Fair” and flows generally north through Paisley
town centre for some 250m before becoming classified as part of the Clyde
Estuary. This classified coastal stretch flows north past Glasgow Airport for
some 5 km before discharge into the River Clyde. The classification criteria
are provided on the SEPA website 17 .
The site is not indicated by the SEPA flood mapping website 18 to be at risk
from flooding. The nearest indicated flood risk zone is located 250m to the
southwest of the site adjacent to the White Cart Water. This stretch has an
estimated over 2m in 100 year flood depth.
13
Hydrogeological Map of Scotland, 1:625,000
14
Groundwater Vulnerability Map of Scotland, 1:625,000 Map Series dated 1988.
15
http://www.sepa.org.uk/wfdmap/map.asp
16
http://www.sepa.org.uk/rqc/map.asp
17
http://www.sepa.org.uk/pdf/data/classification/coastal_waters_classification.pdf
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