`Code
1 -
Accepted
Uncontrolled when printed
INTERNAL INFORMATION
Northern Extension of Northolt Tunnel SIFT Report
Northern Extension of Northolt Tunnel SIFT Report
C222-ATK-DS-REP-020-000034
Revision – P06
Page 45
Uncontrolled when printed
INTERNAL INFORMATION
Location:
Colne Valley
OPTIONS CONSIDERED:
Option A
The Proposed Scheme as submitted in the hybrid Bill
(Northolt Tunnel to West Ruislip/ Viaduct across the Colne
Valley/ Chiltern tunnel east of M25 between jnc 16 and
17)
Option B
Above ground section between Northolt and Chiltern tunnels
placed underground in bored tunnels with provision for
connection spurs to Heathrow
Option C
As per option B but with no passive provision for a connection
to Heathrow
OPTION DESCRIPTION
Key Sustainability
Issue
Topic
STAGE:
Constructio
n or
Operation
EDA
Considered
(incl. Topic
and Ref no.)
Comment
QUALITATIVE IMPACT DESCRIPTION
and/or QUANTITIVE ASSESSMENT
RATI
NG
QUALITATIVE IMPACT DESCRIPTION
and/or QUANTITIVE ASSESSMENT
RATI
NG
QUALITATIVE IMPACT DESCRIPTION
and/or QUANTITIVE ASSESSMENT
RATI
NG
Proposed Scheme during
construction.
There will be adverse landscape impacts upon all
Landscape Character Areas and visual impacts on
receptors located within the vicinity of the site
during the construction phase.
Due to the
magnitude of change and the sensitivity of these
areas there will be a moderate or major adverse
effect on the aforementioned LCAs.
Op
There will be adverse impacts on the following LCA
during operation, Harefield Farmland LCA, Colne
River Valley LCA, Colne Valley LCA, Maple Cross
Slopes LCA and Chalfont St Peter LCA. The
operational impacts will arise from newly
engineered landforms and structures cutting across
the existing landscape including a new viaduct with
associated infrastructure. This will result in effects
ranging from major to moderate at year 1. By year
15 and 60 all effects experienced by the LCAs are
deemed to be non-significant except for those in
Harefield Farmland LCA (which only become non-
significant by year 60) and Colne River Valley LCA
(which remains significantly affected in year 60).
There will be adverse visual impacts experienced by
the following (but are not limited to) residents of
South Harefield, Harefield, Denham Green,
recreational users of the Colne Valley lakes and local
footpaths. There will also be permanent land
severance, the introduction of noise fence barriers,
of highway infrastructure into the semi-rural
environment including road bridges, of overhead
power lines and the introduction of regular high
speed trains. This will result in adverse visual
impacts and significant effects.
o
With careful mitigation design of the landform
surrounding the open gap section it would be possible to
mitigate this feature within the local landscape and
screen key viewpoints.
Vent shafts can be designed to mirror the local vernacular
and screened with planting and/or landform to minimise
their long term impact. Within the base case the National
Grid pylons were diverted away from the Colne Valley
Lakes which was a beneficial with this option this would
no longer occur.
+++ As Option B.
+++
`Code
1 -
Accepted
Uncontrolled when printed
INTERNAL INFORMATION
Northern Extension of Northolt Tunnel SIFT Report
Northern Extension of Northolt Tunnel SIFT Report
C222-ATK-DS-REP-020-000034
Revision – P06
Page 46
Uncontrolled when printed
INTERNAL INFORMATION
Location:
Colne Valley
OPTIONS CONSIDERED:
Option A
The Proposed Scheme as submitted in the hybrid Bill
(Northolt Tunnel to West Ruislip/ Viaduct across the Colne
Valley/ Chiltern tunnel east of M25 between jnc 16 and
17)
Option B
Above ground section between Northolt and Chiltern tunnels
placed underground in bored tunnels with provision for
connection spurs to Heathrow
Option C
As per option B but with no passive provision for a connection
to Heathrow
OPTION DESCRIPTION
Key Sustainability
Issue
Topic
STAGE:
Constructio
n or
Operation
EDA
Considered
(incl. Topic
and Ref no.)
Comment
QUALITATIVE IMPACT DESCRIPTION
and/or QUANTITIVE ASSESSMENT
RATI
NG
QUALITATIVE IMPACT DESCRIPTION
and/or QUANTITIVE ASSESSMENT
RATI
NG
QUALITATIVE IMPACT DESCRIPTION
and/or QUANTITIVE ASSESSMENT
RATI
NG
At a number of locations, views of the Proposed
Scheme will be filtered or screened by intervening
lakeside vegetation. The retention of intervening
hedgerows, trees and the reestablishment of
lakeside vegetation will further reduce adverse
impacts over time. The proposed planting of the
approach embankments will help further screen the
proposed viaduct. However, in certain locations it is
not possible to screen or filter views of the viaduct
because of the open nature of the view as it spans
the Colne Valley Lakes. In such instances significant
effects will continue even by year 60 of operation.
Cultural
heritage
Const
CH1, CH4,
CH5
Savay Farm (an asset grouping of high value), a
scheduled monument located south of Savay Farm,
Pynchester Farm, the Grade II listed Highway
Farmhouse, St Leonards Farmhouse and
Brackenbury Farm will be temporarily impacted by
the high visibility of construction activities and
associated disturbance will impact the setting of
these assets.
The following archaeological assets will be directly
impacted by construction:
• buried archaeological remains associated
with the Mesolithic activity at Dew’s Farm
(major adverse effect);
• Palaeolithic artefacts and deposits within the
Thames Terrace deposits (moderate adverse
effect);
• prehistoric to Roman archaeological remains
at Denham Park Farm and Chenies (major
adverse effect);
• buried archaeological remains of the former
post-medieval garden at The Fisheries
(moderate adverse effect);
• approximately 1ha of ancient woodland at
Battlesford Wood(moderate adverse effect);
• archaeological remains of the former 19th
o
There is a potential to remove significant archaeological
remains during groundworks associated with the 700m
gap to the south of the Chiltern tunnel southern portal
and the Rail Head and ventilation shafts.
The sustainable placement would impact the setting of
the scheduled monument Brackenbury Farm moated site.
It would also affect the listed buildings St Leonards
Farmhouse and Copthall Farmhouse. The sustainable
placement would also have a permanent impact to the
site of a Romano British settlement.
Overall the construction impact of this option is
significantly reduced compared to Option A.
+++ As Option B.
+++