Full Report - Sustainable Aggregates

CR/07/042N
The borehole revealed a succession of glacial till at the surface to 4.8m, with a band of clayey
sand within it, with a dense sand and gravel beneath it to a depth of 12.9m. Between 8.8-9.6m
there was a bed of stiff clay within the sand and gravel. Considered as one unit, the overburden
to mineral ratio of this deposit is 0.6:1. The PSA demonstrates that although the deposit varies
from clayey sand to sandy gravel there is no distinct difference between the deposit above and
below the stiff clay band. Silt/clay content varies from 3% to 25%, except for the 12.6m sample
which shows a high silt/clay content of 46%.
• BH24 [482221 228824]
The geological maps show that BH24 was drilled on an outcrop of glacial sand and gravel,
surrounded by overlying glacial till. There was no reliable existing PSA data for the deposit;
however some records suggest it has relatively high silt/clay content.
The borehole revealed a thin deposit of sand and gravel at surface, an underlying till, beneath
which was a thick (6.10-13.9m) deposit of sand and gravel. Till was recorded to the total depth
of 18.5m. PSA data shows that the upper sand and gravel is very gravelly sand with 20%
silt/clay. The lower thicker deposit is clayey sandy gravel, with an average silt/clay content of
15%, with a minimum of 13% and a maximum of 16%, increasing with depth. The overburden to
mineral ratio for this lower sand is 0.8:1.
• BH29 (and redrill 29a) [486437 226987 and 486207 226850]
Borehole 29 was drilled on glacial till with glacial sand and gravel mapped beneath it. BH29a
was drilled approximately 300m southwest of BH29, a location mapped as glacial sand and
gravel with no overlying till. This location has chosen as there was very little existing borehole
data for the sand and gravel unit.
Borehole 29 encountered an upper till above the sand and gravel deposit. This was not found in
BH29a, supporting the geological mapping. Beneath the sand and gravel unit in BH29a was a
lower till. Chalk clasts were identified within the BH29 sand and gravel unit. The PSA data
demonstrated that in both boreholes the deposit was consistently clayey very sandy GRAVEL to
a depth of 13.3m. Below 13.3m in BH29a the deposit changed to consistent clayey SAND. The
units highest silt/clay content is 21%, at the 1m depth in BH29a, however, elsewhere it varies
between 11-1%. The overburden mineral ratio for the sand in BH29a is 0.2:1.
• BH30 (and redrill 30a) [489256 224939]
BH30a was a redrill of 30a due to problems concerning inadequate casing diameter during
BH30. Because of this the boreholes were drilled only a few metres apart. The location within
the regional stratigraphy is identical to BH29, drilled through the overlying till to investigate the
potential resource beneath.
The till contains two beds of sand and gravel. The upper one is 180cm thick at a depth of ~4m,
and identified in both boreholes, the lower one only found in BH30a, with a thickness of 70cm.
PSA analysis demonstrates that the upper bed is very clayey (26%) very gravelly SAND. The
main body of sand and gravel, identified in both boreholes, is from a depth of around 14m,
directly beneath the till. PSA has shown that this varies between very clayey very gravelly
SAND to gravelly clayey SAND. Throughout the deposit, the silt/clay content never rises above
22%. The overburden to mineral ratio for this lower deposit is around 1.3:1.
18.3 GLACIOFLUVIAL SANDS AND GRAVELS IN THE WEST OF THE PROJECT
AREA
• BH31 [462338 244008]
Borehole 31 was drilled to investigate the potential of a sand and gravel deposit beneath the
glacial till mapped at the surface. A channel of sand and gravel is suggested by the geological
map, but there were very few existing boreholes and no PSA data.
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