Proposal for Northern Extension of Northolt Tunnel sift report

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INTERNAL INFORMATION 

Northern Extension of Northolt Tunnel SIFT Report  

 

 

Northern Extension of Northolt Tunnel SIFT Report  

C222-ATK-DS-REP-020-000034  

Revision – P06 

 

                         

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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

 

1.1.11 

 

Overall, the temporary construction impact on BMV 

agricultural land by Option B and C would be comparable 

to the Proposed Scheme. The three holdings affected 

would still experience comparable impacts to those 

identified for the Proposed Scheme.  

Once the land is restored to agriculture (if that is the 

intended end result) the permanent impact on 

agricultural land and the three land holdings would 

reduce. 

 

There would be minimal temporary or permanent impacts 

on forestry, and negligible impacts to the soil resource. 

Op 

No operational impacts. 

o 

No operational impacts. 

o 

As Option B. 

o 

Land quality 

Const 

 

No construction impacts. 

o 

No construction impacts. 

o 

As Option B. 

o 

Op 

No operational impacts. 

o 

No operational impacts. 

 

 

o 

As Option B. 

o 

Waste & 

material 

resources 

Const 

 

This option does not generate significant excavated 

material as the alignment is on viaduct or at or near 

grade. Sustainable placement areas are located 

within the Colne Valley area to accommodate 

surplus excavated from excavations. 

1.1.12 

 

1.1.13 

 

o 

The scale of below ground works associated with Option B 

would result in the generation of a large quantity of 

excavated material.  Since the tunnel also removes the 

need for engineering fill material and mitigation 

earthworks, this would substantially increase the total 

volume of excavated material generated.  The volume of 

surplus excavated material needing to be disposed would 

increase to 4.22 million cubic meters 

 

This assessment does not include any provision for 

additional local sustainable placement of site. 

--- 

As Option B, although the volumes would be slightly less 

as there would be no requirement to create the caverns 

to accommodate the turnouts for the Heathrow Spur. 

--- 

Op 

Not assessed at this stage 

N/A 

Not assessed at this stage 

N/A 

Not assessed at this stage 

N/A 

 Overall Rating 

Significant above ground construction and 

operational impacts have been identified for this 

option including; noise, visual and ecological 

impacts. The options will result in a number of utility 

diversions. Material derived from the Chiltern tunnel 

would be used to mitigate operational noise and 

landscape impacts, which would allow the vast 

majority of excavated material to remain on site. 

o 

This option would avoid the majority of the above ground 

impacts identified in Option A during construction and 

operation including indirect impacts as a consequence of 

utility diversions. The additional tunnelling will generate 

significant volumes of additional spoil. Spoil from the 

Chiltern tunnel that was to be used for on-site mitigation 

in Option A would no longer be retained on site as the 

requirement for mitigation would be removed in Option 

+++ 

As Option B, although there would be a slight reduction 

in spoil generated and removed from site that would 

also slightly reduce construction traffic numbers 

compared to Option B. From an environmental 

perspective this option is considered the preferred 

option. However, further detailed assessment work of 

the implications for off-site disposal would need to be 

undertaken and options to reduce the volume of 

+++ 

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