The Norwood Tunnel finally collapsed in 1907. It was always regarded as the biggest obstruction to full restoration of the Chesterfield Canal. The following is an extract from Next Navigation East, 2010, by Dr Geraint Coles. It describes the issues pertaining to restoration of this stretch of canal.

© Chesterfield Canal Partnership.

 

14.4 Options for Replacing the Norwood Tunnel
14.4.1 To determine how the Norwood Tunnel could be replaced and a passage achieved under the M1 Motorway which now runs above and across the tunnel site a study was commissioned from Arup in 2007 (Arup 2008).
14.4.2 Arup examined four alternatives:
*Reconstruct and re-open the original Norwood Tunnel
*Re-use a parallel railway tunnel
*Build an entirely new tunnel
*Build a new surface route and re-use some parts of the original tunnel
14.4.3 The Arup study demonstrated that the western portion of the Norwood Tunnel cannot reasonably be restored – some sections have collapsed, others were infilled by the National Coal Board and one length was injection grouted when the M1 was built. It also confirmed that the portion of the tunnel east of Hard Lane was intact, not infilled and could reasonably be restored to use.
14.4.4 The study concluded that the full reopening of the original tunnel was not feasible and that re-excavation along the original line posed too many problems to be cost effective. Further, reconstructing an extremely long narrow bore tunnel would not be amenable to use by powered boats and would not serve the needs of a tourism orientated waterway. It did promote re-use of the eastern tunnel fragment as part of a combined route.
14.4.5 The railway tunnel was on a gradient and modification of the bore would compromise the structure with significant cost implications. Similarly, the building of an entirely new tunnel was also dismissed on the grounds of cost, unquantifiable underground risks in an area with a history of coal mining. Further, a new long tunnel would suffer from similar ventilation and poor amenity benefit as the original tunnel and, like the original, any new tunnel would be a bottle neck in operation.
14.4.6 Arup concluded that the most cost effective and sustainable option for replacing the tunnel was the construction of a new surface route incorporating the short length of surviving tunnel at the eastern end. A part surface route is possible because the tunnel lies at a very shallow depth (barely 4m or 12ft below ground surface) and there is an existing farm underpass suitable for conversion to canal channel. Arup noted that a similar conversion had been successfully carried out on the Rochdale Canal during restoration in the 1990’s.
14.4.7 Arup made recommendations for further work. The proposals here reflect the development of the Arup proposals in the light of that work.

14.5 Creating a New Surface Route
14.5.1 The proposed replacement for the Norwood Tunnel has the following elements:
*Works to stabilise the Western Portal of the Norwood Tunnel
*New channel and locks west of the M1 ridge
*Modification of the M1 Motorway underpass
*New channel, water storage ponds and locks to the east of the M1 ridge
*New cutting and locks to descend to tunnel level
*Re-use of the eastern tunnel fragment and the Eastern Portal of the Norwood Tunnel
*Access, Interpretation and display improvements
14.5.2 The works proposed are described below.

14.6 Works to stabilise the Western Portal of the Norwood Tunnel
Current Condition
14.6.1 The western portal takes the form of a simple arched opening in a vertical stone wing wall. The wall is composed of coal measure sandstone blocks laid in roughly half-overlapped mortared courses. The block heights are consistent at around 0.25 to 0.3 m and the resulting horizontal courses appear straight regular; the block lengths are less regular and vary from 0.45 to 0.25 m, leading to an irregular vertical
overlap with the blocks below. The wall is completely plain and lacks any form of ornamentation or decoration.
14.6.2 The tunnel arch consists of three rings of hard red brick sitting on a footing of sandstone blocks keyed into the wall courses. Five courses of keyed sandstone blocks are visible above water level before commencement of the brick arch which extends through eight stone courses and is capped by a single course of stone.
14.6.3 It is uncertain if this interesting composite arch is original or results from the partial replacement of an original stone arch during the raising of the tunnel roof in the 1870’s (above). It is noticeable that the projected centre and radius of the partial arch formed by the keyed stone blocks is different from the arch centre and radius of the brick arch leading to the portal having a slightly elliptical appearance. This may support the notion that the current arrangement is not original and results from the reconstruction.
14.6.4 At present the tunnel arch is infilled with a lighter soft red brick with a single rectangular opening in the middle of the blocking wall. This opening is closed with a series of vertical bars. Through the bars it is possible to see that the tunnel roof has collapsed into the passage space within approximately 5 to 10 metres of the opening.
14.6.5 The tunnel level summit pound is still in water and this runs up to foot of the blocking wall. The curtain wall is visible and in reasonable condition with no obvious indications of immanent collapse. Much of area round the wall is overgrown especially in the summer. For example, the site of the Tunnel Keepers cottage and the stables to the left and above the tunnel entrance can only be seen in the winter
when the vegetation is low.
14.6.6 The opening in the tunnel blocking has enabled the short length of tunnel before the collapse to be used as a bat roost and bats are active over the surviving water spaces. The channel leading to the portal is in water. Water-vole, although not reported in this location, are present in the upper pond immediately below this level and it is likely that are also resident here.
Proposed Treatment
14.6.7 The site will be sensitively cleared of excess vegetation and a programme of woodland management initiated to control tree growth which could damage the historic fabric.
14.6.8 Once cleared the wall and portal will be inspected and any necessary repairs undertaken to ensure the stability of the structure. This will include ground anchoring if required together with replacement of rotted / displaced stone and pointing.
14.6.9 The remaining foundation features of the Toll Cottage and Stables block will be consolidated and stabilised (not rebuilt). On-site interpretation will be used to explain the significance of the remains and their relationship to the tunnel.

14.7 New channel and locks west of the M1 ridge
14.7.1 The new surface route will commence where a new length of canal channel leaves the original line on the off-bank around 75 m west of the standing West Portal of the Norwood Tunnel. The new line will be carried in shallow cutting to the south of the tunnel entrance wing wall.
14.7.2 The towpath will be carried up and around the top of the original Norwood Tunnel mouth past the site once occupied by the Tunnel Keepers cottage and the towing horse stables. The towpath will then rejoin the north bank of the waterway.
14.7.3 After 50 m the cutting will deepen and enter the first of the new “Norwood Extension Locks”. A bridge over the lock tail will maintain connectivity between the towpath and the public right of way extending south through the Nor Wood to Killamarsh.
14.7.4 The Norwood extension locks are sited off the line of the original tunnel to avoid new construction on potentially compromised ground where long term stability cannot be assured.
14.7.5 The Norwood Extension Locks consist of two three-rise locks. The first is the Norwood High Treble Locks (No.’s 19a, 19b and 19c). At the top of this multiple lock the canal enters a short pound where the canal track turns slightly before entering the second three rise group – the Norwood Top Treble Locks (No.’s 19d, 19e and 19f). At the top of the second group the canal reaches the new summit pound and turns north-east and arrives at the west entrance to the farm underpass below the M1 Motorway.

14.8 Modification of the M1 Motorway underpass
14.8.1 There are two options for how the M1 Motorway or Poplar Farm underpass can be modified to accommodate the canal. The simplest involves foundation underpinning, excavation of the farm track surface and insertion of a new canal channel. The towpath would run beside the water channel.
14.8.2 The second option would involve deep piling beneath the underpass, excavation and the insertion of a reinforced concrete box culvert. The upper surface of the culvert box would lie at the current surface/trackway level within the underpass and would be designed to accommodate the weight of farm vehicles. The culvert box would extend beyond the ends of the existing underpass to accommodate the farm tracks on the surface.
14.8.3 The box culvert would only be large enough for a single boat and the towpath would be brought up to the surface level above the canal and then pass through the underpass. Leaving the underpass it would then drop back down to canal level.
14.8.4 This option would require longer cuttings on both east and west flanks of the ridge with consequent spoil disposal issues but it would reduce the number of locks by four (2 up and 2 down), remove the need for a footbridge at the underpass, extend the summit pound and increase water storage. It would also allow the underpass to be retained for farm traffic.
14.8.5 The second option obviously requires more complex civil engineering but the increased costs can be balanced by a reduction in lock construction costs and, by decreasing the number of locks, yield a long term saving in maintenance costs.
14.8.6 It should be noted that the two options do not affect the horizontal alignment of the canal and the track required is the same.

14.9 New channel, water storage ponds and locks to the east of the M1 ridge
14.9.1 On the eastern side of the motorway the canal would run for a short distance in a shallow cutting before running on or around the current ground surface. In option one, a foot and cycleway bridge over the canal maintains rights of way connectivity.
14.9.2 The new summit pound will be relatively short irrespective of which option is adopted. To increase water storage two new side ponds will be created on the off bank. These will also form new off-line wetland nature reserves. The ponds will link, via separate feeders, to the main canal channel to the east and west of a single flood-gate / lock gate. This will be counterbalanced to swing closed after use and
will divide the waters in the western and eastern halves of the section. This is intended to ensure separation of the waters of the Rother and Idle catchments in line with the catchment management  strategy of the Environment Agency.
14.9.3 Beyond the ponds, at the eastern end of this short summit pound, the canal will run onto a short length of low embankment before descending a two-rise staircase lock. At the tail of the lock a minor bridge will carry Coalpit Lane over the canal. The route then follows the approximate line of existing field edge drains and adopts the extant hedge line as the off-bank boundary.
14.9.4 At the western edge of the former Kiveton Colliery Tip (now reclaimed and landscaped as amenity woodlands and country park) the canal descends via a further two locks in a staircase configuration (the Wales Double Locks).
14.9.5 East of the Wales Locks and Wales Bridge the canal is at the Kiveton Waters pond level. It then skirts the north-west boundary of the former colliery tip utilising the line of an existing trackway and drain before entering the former colliery site itself.
14.9.6 The route within the Kiveton Colliery site has already been defined by the construction of a canal channel and deep cutting. This prepared and protected route was built when the landscaping of the former colliery site was undertaken by English Partnerships. At the same time three large ponds, Kiveton Waters, were constructed. These ponds were cut to a navigable depth profile with the intention
that they can be converted into a marina once the canal is restored. In the interim they are let as fishing ponds.

14.10 New cutting and locks to descend to tunnel level
14.10.1 The link to the re-usable fragment of the Norwood Tunnel will be made by excavating a cutting to the west of Hard Lane. Within the cutting a three-rise staircase lock will lower the canal to the tunnel pound level.
14.10.2 The location and land for the cutting was identified by British Waterways in the site masterplan for the development of the Kiveton Colliery site. This land now form part of their holding along with the reserved canal corridor.

14.11 Re-use of the eastern tunnel fragment and the Eastern Portal of the Norwood Tunnel
14.11.1 Once at tunnel level a concrete box culvert will take the canal beneath Hard Lane and make a junction with the intact section of the tunnel.
14.11.2 The eastern tunnel fragment was opened and inspected by British Waterways during their restoration of the section from Shireoaks to Kiveton Park in 2001-2003. British Waterways report that the first c. 420 m of the tunnel is in excellent condition with no obvious signs of structural distress or damage. The tunnel is collapsed a point roughly 420 m inside (i.e. west of) the eastern portal. This corresponds with a point circa 20 m east of Hard Lane.
14.11.3 The intention is to use this first 400 section of the tunnel and bring the canal through this short fragment and out of the existing east portal of the Norwood Tunnel into the cutting west of Kiveton Park Station. This is the current head of navigation from West Stockwith on the Canal & River Trust section.
14.11.4 The eastern portal is the twin of the western one and is no more adorned. It consists of a straight limestone retaining wall in coursed rectangular blocks. The main arch of the tunnel is roughly central to the wall and is formed of three rings of hard red brick. The entrance itself is infilled with a red brick wall. This has no openings.
14.11.5 The land corridor required for the new canal, marina and works within the former colliery site, together with the remaining tunnel fragment, are all owned by the Canal & River Trust.