Chapter 9: Road drainage and the water environment

Memorandum
(Continued)
Page 2 of 6
Lower Lias Clay
The solid geology comprises Lower Lias Clay of varying strength from stiff to hard. This material is likely
to comprise of closely fissured bluish grey clay with fossil fragments. Within this strata, bands of
mudstone and limestone bands are common.
4. Groundwater Data
River Terrace Deposits and Alluvium
The River Terrace Deposits and Alluvium are classified as minor aquifers usually only of local importance
for supporting abstractions or providing baseflow to surface waters.
Lower Lias Clay and Glacial Till
The Lower Lias strata and Glacial Till deposits are generally classified as non aquifers, however, there is
potential for groundwater flow through fissures and rock inclusions within the solid deposits. Also, specific
units within the Lower Lias Clay can have minor aquifer status as some of the thin limestones within the
strata can yield significant quantities of water.
The proportion of water bearing limestones increases towards the base of the Lower Lias Group, forming
the Blue Lias or Scunthorpe Mudstone Formation, which is classified as a minor aquifer.
On the basis of interpretation of the published geological map, the strata below the proposed scheme are
towards the top of the Lower Lias Group sequence, and therefore would indicate non-aquifer status.
Correspondence from the EA (2003) indicates that the underlying geology is a minor aquifer, but it is not
specific with respect to the various geological formations being referred to. An earlier EA /National River
Authority publication classifies the Lias Group as a non-aquifer which is also in accordance with the
Envirocheck report and published groundwater vulnerability mapping.
The geological memoir notes a cutting for the M1 located approximately 30 m south of the proposed A14-
M6 Link at NGR [56137858], where 1.5 m of Glacial Till is underlain by 3m of Lower Lias Clay overlying 6
m of Mudstone. At the foot of the cutting a 15 m limestone band was encountered, described as yielding
large quantities of water.
Groundwater Abstractions
Abstractions below 20 m 3 /day (with a number of exceptions) do not require a licence from the EA; these
private supplies are registered with the relevant Local Authority. There is one private well (NGR SP 5610
7775), located at Station House, Lilbourne, approximately 1 km south of the A14-M6 Link. No other
information is available. On the basis of location, it would appear to be sourced by groundwater within the
river terrace gravels /alluvial deposits.
There is one licensed abstraction for 2 wells (NGR SP 5621 798) located approximately 1 km northeast of
the A14-M6 Link at Swinford Lodge. The license is for general farming and domestic use all year round
but for a relatively small annual volume of 1637 m 3 (and maximum daily rate of 5.5 m 3 ).
Groundwater Monitoring
Exploratory holes relevant to the Swinford Road Cutting and A14-M6 Link are listed in Table 4.1, including
groundwater strikes and other pertinent information. Monthly groundwater monitoring data collected
between April 2004 and August 2006 is summarised in Figures 4.1 and 4.2 with average groundwater
levels recorded in Table 4.1.
Jacobs Engineering U.K. Limited
Jacobs_MemoA4.doc