Supporting documents

Geotechnical Laboratory Testing
Atterberg Limits
7.11 Atterberg limit determinations were carried out on 4 samples of natural cohesive soil
at depths of between 0.5 and 1.0m with plasticity indices recorded at between 19% and 34%,
corresponding to an intermediate to high plasticity. Modified plasticity indices, as defined
within NHBC Chapter 4.2 ‘Building Near Trees’, indicate values of between 14% and 30%,
with the natural clay soils assessed as having a low to medium volume change. Overall the
cohesive soils should be considered as having a medium shrinkage potential.
Sulphate and pH Determinations
7.12 Within the made ground water soluble sulphate concentrations ranged between
11mg/l and 91mg/l with pH values between 7.1 and 8.7. Within the natural soils water
soluble sulphate concentrations ranged between 15mg/l and 69mg/l with pH values between
6.7 and 7.4. The results from both the made ground and natural soils indicate a BRE Special
Digest 1:2005 Design Sulphate Class DS-1 with an ACEC site classification AC-1.
Gas Monitoring
7.13 The results of the ground gas monitoring carried out to date (2 occasions) are
summarised in the following table:
Location
CH 4
(% v/v)
CO 2
(% v/v)
O 2
(% v/v)
Flow
(l/hr)
Barometric
Pressure
(mb)
Maximum GSV*
WS1 0.0 0.0 19.6 – 19.7 0.0 1019 – 1039