STREAM MILL BRIDGE

STREAM MILL BRIDGE AT CHIDDINGLY

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Report on condition of Chiddingly Stream Mill Bridge on behalf of Chiddingly Parish Council. February 20 2007.

Background

Stuart Page Architects was appointed by Chiddingly Parish Council to undertake a survey, prepare an assessment of building works and costs for the repair of the bridge.

Our experience of the conservation of historic buildings includes Ightham Mote, Old Soar Manor, Mediaeval Dovecotes at Charleston Manor and Alciston, Spillway and sluices at Ashburnham Furnace.

The terms of appointment asked for the cost of stabilisation works and full repairs. These could only be properly assessed following a survey and measured drawing and the preparation of a draft Schedule of Works. Although the survey was only restricted by water flow, the construction work will be affected by water flow, temperature and by the Environment Agency, English Nature and perhaps Defra.

The Parish Council confirmed the terms of appointment in October 2006.

The Council organised the site to be cleared of damaging tree and ivy growth.

Terms of Reference

2.01 The survey included the standing remains of Chiddingly Stream Mill Bridge.

2.02 The survey had the following priorities:

(i) to report on the general condition of the structure

(ii) to advise whether additional investigations are needed to produce a balanced report

(iii) to advise whether additional investigations by specialist consultants or contractors are necessary

(iv) to provide a description of the bridge in drawn, written and photographic form

(v) to provide budget estimate of the building costs

2.03 External elevations were viewed from ground level with the use of binoculars where appropriate,

2.04 Access to the soffit of the arch and spillway was from a distance and close access was not possible.

2.05 We were not asked to open up the structure or excavate the bridleway.

2.06 On a structure of this age and condition defects can materialise very quickly. The report can only be taken as describing those faults visible at the time of inspection.

2.07 We have not inspected foundations or other parts of the structure which were covered, unexposed or inaccessible at the time of the survey, and we are therefore unable to report that any such part of the bridge is free from defect.

2.08 In view of the general condition of the bridge the possibility of faults existing within the structure should be acknowledged and accepted.

2.09 The survey and report have been undertaken on behalf of The Chiddingly Parish Council and no liability is accepted to any third party.

Acknowledgements:

Kirsten Roberts - Present Clerk to the Council

Robin Symington - Past Clerk to the Council

Rik Fox - Morton Partnership - Structural Engineers

Jon Tilley - Stone Mason

Helen Lucking - Corylus Ecology

The Environment Agency

The Survey
We visited the Bridge on five occasions, 17th December 2005 to prepare our fee proposal, 16th September 2006 to begin survey and brief specialist surveyors and 4th November 2006 to complete the survey. The fifth visit in January 2007 was accompanied by Jon Tilley Stonemason, who had worked with us at Ashburnham Furnace and other projects.

The weather was dry and bright for all visits and the days were chosen to avoid high water levels, apart from the final visit on 20th January 2007 which followed very heavy rain.

The specialist levels survey by ACAD sets the Bridge in context and provides a framework for the architectural and structural report.

Tree clearance was undertaken prior to the visit in September and improved access and reduced the risk to the structure.

Rik Fox, Structural Engineer of the Morton Partnership, visited site to offer advice on the structure of the bridge and its repair.

Listing
Chiddingly Stream Mill Bridge is Listed Grade II of Historic and Architectural Interest.
The grid reference is TQ 555155.

History
The following text is taken from the Chiddingly Parish Council website and includes the English Heritage assessment.

STREAM MILL BRIDGE AT CHIDDINGLY

English Heritage assessment October 2005

The bridge at Chiddingly in its present form dates from the late C18 or early C19. However, its historical significance goes back to the C15 and C16 when a bridge on this site, possibly with elements remaining in the present bridge, was associated with a forge and cannon boring ironworks at the nearby mill. The bridge and mill are integrally linked, and the grooves for sluice gates to control the flow of water from the millpond are visible on the north bridge supports.

The bridge has some repair in the C19 to its supports, visible as inserted brick courses, but is essentially intact. The bridge has group value with the nearby listed C17 or earlier Stream Farmhouse and Barn, which has C16 and C17 elements. The Old Bridge at Steam Mill is considered to be of sufficient architectural or historic interest to merit listing.

DESCRIPTION: The keystone and arch is of ashlar. Parapet of wooden posts. Brick buttresses of probable early C19 type bonding. The deck of the bridge is of slag with stone protruding from the surface. Spillway on south side constructed of stone and brick. The bridge is closely associated with the operation of the nearby mill and has the grooves of a sluice gate on the stone blocks of its north side, by which it regulated the water flow from the mill pond. The track over the bridge is the major bridle way through the village with links to the Weald and the Vanguard Way.

HISTORY: The Bridge is closely associated with a mill which lies about 100m to its south east. On the north side of the bridge supports are the slots for sluice gates to control the flow of water from the mill pond, showing that the bridge dates at least from the time of the working mill. The mill, in turn, is associated with iron working on the site. It is first mentioned in the Doomsday Book. and iron working on the site dates from C15, when it was controlled by the Elphic family who were listed in documentary sources as 'iron masters'. In the mid 1500s the iron works passed to the French family, who were also 'iron masters', and is again mentioned in early C17 in the ownership of James Lullham. Canon boring took place in the Tudor period south of the bay near the mill. The mill was originally a hammer mill for the iron works, but by the early 1800s the iron working had ceased, and the mill became a corn mill

SUMMARY OF IMPORTANCE: The Bridge is significant as a well preserved late C18 - early C19 Bridge, with an intact spillway, and as an integral part of the working of the nearby corn mill. Potential earlier fabric in the Bridge gives it additional interest, as it ties the Bridge to earlier uses of mill for iron working. The Bridge also has group value with the nearby listed, C17 or earlier. Stream Farmhouse, and Barn, which has C16 and C17 elements.

SOURCES: H Cleere and D Crossley, The Iron Industry of the Weald (1985).

Architect's Report
Chiddingly Stream Mill Bridge carries a public bridleway approximately 3.5 metres in width on a single span arch of 3.75 metres over a brick paved, stepped spillway (or weir).

The spillway falls approximately 2.5 metres north to south while the bridleway is approximately 3 metres at its highest point above the upper most step in the spillway.

The bridge has revetments built of Wealden stone and brick to the north and brickwork to the south.

The surface of the bridge appears to be paved with sandstone slabs, largely concealed by mud and grass.

The mill stream runs north easterly and turns a right angle to pass under the bridge to the millpond from which it flows to the south west.

The site is wooded with mature trees around the pond and neglected coppice lining the bridlepath.

Trees and ivy were cleared in 2005, to reduce damage to the masonry, which has suffered from settlement and possible historic 'robbing'.

The well pointed brickwork lower revetments suggest a 19th or early 20th Century repair to an early masonry structure.

The arch soffit, voussoirs and parts of the revetment walls are all Wealden sandstone.

A keystone on the southern face is dated 1752 and initialled CC (the year when England changed from the Julian to Gregorian calendar).

The northern revetments and the arch have suffered badly from plant growth which must not be allowed to regenerate.

A temporary "Heras" barrier has been erected to block the bridge but the eastern barrier has been broken down.

A four rail timber balustrade provides limited security but could be pushed over fairly easily.

The excavation or driving in of the uprights has not helped the stability of the remaining 'parapet'.

It is not clear from the surviving masonry if the bridge had a parapet or a kerb coping. The unmetalled bridleway runs out to the edge of the stone to the north but there is a very low upstand on the southern side of the bridge.

The Arch
The bridge soffit is built from large Wealden sandstone blocks laid in 300-400 mm courses. The facing voussoirs are up to 300 mm in thickness as are the quoins.

There is a centre panel of brickwork at the apex and underside of the arch that suggests a repair although this cannot be proven until there is scaffolding access.

The bricks used for revetments are well burnt heavy red bricks without frogs. They resemble Ashburnham bricks in colour and texture although there must have been closer brickfields.

The bricks are neat and square but vary in size:

230-220 in length

110-115 wide

60-65 thickness

The apex of the arch appears to have spread outwards to the north and south and an iron/steel rod runs along the soffit. It has bolted ends attached to a vertical bar. If this is acting as a strap the upper fixing should run through the bridleway base or there should be a hooked end, embedded in the roadway.

Any repair would have to consider the effectiveness of this strap and whether or not it should be retained.

The soffit of the arch appears to be in good condition although open joints would have a natural tendency to close and fill.

There is evidence of spalling stone and cavities at water level, particularly to the north.

South Arch
The outer stones forming the ashlar, voussoirs and springing are moving outwards, allowing the arch to flatten. A consequence is that the spandrel between coping and voussoirs has dropped on the south east.

The south west spandrel and quoin has moved considerably and is now over 200mm out of vertical over 2 metres in height.

There is an open crack through this spandrel, up to 100mm in width. This movement has allowed seven voussoirs, from springing to keystone to move. Two have dropped by 50mm.

There are open joints within the arch at springing level.

North Arch
Both spandrels have moved as a consequence of plant growth and possible structural movement.

The north west springing is badly displaced although a historic brickwork repair suggests the movement is old. The twist in the voussoirs results in compression at the corner of the brickwork and probable damage to the adjoining masonry block.

The metal tie plate is offset from the arch apex and is as precarious as the southern tie.

The northern arch has brick rebates to the east and west. We assume these were part of the sluice gate housing used to regulate the flow of water. They are in fair condition with some cracking, spalling and open joints.

North West Revetment
This revetment has good sandstone blocks that have been displaced by plant growth, water movement and settlement of the causeway.

Loss of ground level ashlar on the face has been made good with brickwork that is in very poor condition while some stones are 150mm out of alignment.

The displacement to the north east face is severe with outward movement of masonry and failure of 15-20 courses of bricks.

North East Revetment
The north east revetment has been heavily patched with brickwork so that only half the masonry survives. There is evidence of undermining and continuing loss of masonry at water level. Tree roots are deeply embedded in this face.

The north east face is also poor despite the bank offering protection from the water. One cavity is over 1.4 metres in length, 450mm in height and 450mm in depth. This has resulted in collapse of brickwork retaining the bridleway and displacement of the wall by 180mm.

A vertical joint in the brickwork suggests a late repair but the bricks match. The brickwork here appears to be 225mm in thickness laid in English bond (alternating) courses of headers and stretchers.

To the east this wall has failed, whether due to the structure or robbing it is not entirely clear.

The Weir
When the water flow is slow it is possible to see remnants of paving or a structure in the silt. The depth of the silt and the nature of the remains are not known.

The Spillway
The stepped spillway begins approximately 1 metre below the bridge and consists of twenty equal steps 360mm in going and 125mm in height.

The survey did not include access to the spillway but from binocular inspection, and by observing the flow of water, the brickwork appears to be in good condition.

Although there may be undermining at the foot of the spillway there is no evidence of subsidence or failure of the lower step.

The depth of water down stream of the spillway is not known but it varies according to weather conditions.

Buttresses
The south elevation is marked by two earth filled brick faced buttresses in very good condition. Some repointing and protective weathering of the upper surfaces is needed.

There is damage and some undermining to the east and west sides. This has been caused by tree roots and soil erosion.

Conclusions
The masonry is generally in fair condition and capable of reuse with additional new stone to complete remaining sections. Brick patching could also be used.

Wherever possible masonry can be left in position and tied back into the made up ground. However some masonry has moved too far to allow this and will have to be dismantled.

Specialist advice from a structural engineer is has been sought to support decisions on the parapet and the degree to which the masonry can be allowed to be out of vertical.

The bridge does not seem to be in immediate risk of collapse but ancient structures in poor condition can deteriorate rapidly.

Regeneration of trees and ivy must be prevented.

Ecology & Bats
The Bridge is set in relatively undisturbed countryside and appears to be a perfect location for bats. It is possible that the crevices in the soffit could be used as a roost. The presence of bats and their use of the Bridge should be established before work starts.

Ecologists have carried out a survey of a barn within the neighbourhood and found several species of bats including Natterer's bats. There is also evidence of Daubenton's bats in the area and this species is particularly associated with water and bridges. Based on the level of risk involved we recommend that a bat survey is undertaken.

The initial assessment could be during the winter period and this would determine the potential of the site as a whole and the potential of the whole structure or individual areas of masonry.

Depending on what is found, a licence may be required from Natural England (used to be Defra licence) and/or further surveys in summer of 2007 may be needed.

It is important that we know whether bats are present before we start on site when delays can be very expensive. Roosting cavities can be provided as part of the building works.

Our practice has worked closely with ecologists and the local agencies to minimise disturbance and provide long term solutions to roost sites.

The area is of importance to wildlife and the environment. We recommend that an assessment of the site is undertaken and an estimated cost is included as Appendix 4.

Archaeology
We recommend that an Archaeologist be appointed to monitor the work and this may be a condition of any approval or grant aid. We would suggest that South East Archaeology be an appropriate choice. Any Antiquities, fossils and other objects of interest or value which may be found on site or during excavation would become the property of the Employer. On discovery of such objects a Contractor would cease work immediately advise the Architect and Archaeologist and await further instructions

The Contractor would allow for attendance on site by an Archaeologist appointed by the Employer during the course of the project and would be allowed to inspect and record newly exposed elements of the bridge as work proceeds.

On discovery of elements of the structure that are unexpected or have not been recorded then the Contractor will advise the Architect immediately and await further instruction.

Schedule of Works
This draft schedule of works has been prepared on behalf of Chiddingly Parish Council, to whom it is addressed.

It is not a specification, although it follows the sequence of a specification that will allow

it to be developed into one at a later date.

Preliminary Schedule of Works
This schedule has been prepared to recommend a sequence of works, the nature of repairs and to provide a means of preparing a budget estimate. It is not a specification nor is it a contract document.

The nature of the site cannot be fully ascertained before it has been opened up but the following risks will be present:

(i) unstable masonry

(ii) unstable foundations and stream beds

(iii) soft stream beds and banks

(iv) fast running and variable depth of water

A Pre-contract Health & Safety plan will be required although it will not be a complex document.

Site clearance of trees will be completed by others but the Contractor must allow for removing stumps, roots and vegetation that place the structure at risk.

The Employer must give adequate notice to Southern Water and to the Environment Agency before commencing work.

The Contractor will have to provide assurance that access to all banks and to the bridge path has been agreed with adjacent owners and tenants before placing constraints.

The Contractor will allow for specialist attendance that might interfere with the progress of work such as the Archaeologist and the Ecologist.

Contingencies
The Schedule and Specification will include provisional sums for types of work where the quantities cannot be accurately foreseen before access is available and opening up has begun.

Building Works
Provide Heras fencing site enclosure and security/safety notices.

Photograph and record site and access before starting construction.

Divert water flow temporarily to permit scaffolding to be erected, and work to be undertaken.

Support the soffit of the arch to enable repairs to take place without the voussoirs being displaced or the arch moving during building works.

Scrape surface of bridle path to remove mud and vegetation.

Photograph and record the surface and pass records to Architect.

Lift pavings, mark each stone with crayon (on underside) or chalk and record on drawings.

Mark any stone to be removed or repaired in cooperation with the Architects and record on the drawing.

Excavate by hand to agreed level (3 x ashlar courses below existing parapet) and remove waste and debris.

Set aside materials for inspection by Archaeologist and remove from site on completion.

'Taking down' shall include removal of old mortar and roots and extraction of roots.

Take down three ashlar courses on south elevation, east and west sides. Rebuild using existing sandstone in the same location and orientation.

Remove existing wrought metal tie.

Take down north west abutment and rebuild using existing brickwork and sandstone in the same location and orientation.

Take down north east abutment and rebuild using existing brickwork and sandstone in the same location and orientation.

Backfill using compacted road stone - Dtp type 1.

Incorporate open weave geotextile membrane if required by Engineer.

Resurface roadway using existing pavings.

Make up paved surface using crushed stone Dtp type 1 and brushed insitu concrete for carriageway or reinstate existing stone pavings where salvaged.

Increase height of north parapet to match south using salvaged "Ashburnham" bricks from site.

Allow for installing masonry bat roosts to Architect's detail.

Grout cavities before piecing in.

Reface spalling stone using Wealden Sandstone.

Piece in cavities on face of existing masonry using bricks or Wealden sandstone, in areas where the masonry is predominant, or clay tiles where coursing permits and directed.

Provisional allowances may be included in the specification for piecing in, grouting and re-facing.

Check spillway and weir and allow for grout/brick patching as a provisional sum.

Provide new English oak balustrade with pedestrian/horse rider stiles at east and west approaches.

Install site notice board provided by Client.

The specification for undertaking the works will include provisional sums and allowances, contractor's overheads and profit and a contingency sum.

Appendix 1

Temporary Barriers
The Morton Partnership (Structural Engineers) has advised that the Bridge could be reopened as a temporary measure.

This is conditional upon temporary barriers being provided to restrict the width of the bridleway.

A timber post and rail fence, braced to railway sleepers could be erected on the centre of the bridge.

The width would have to be restricted to a single file horse and rider.

The 'open' ends each side of the rail would have to be closed at a point that prevents anyone walking close to the edge of the Bridge.

Vehicles would have to be prohibited from using the Bridge.

Sleepers are suggested because they can be spiked to the ground.

Traditional post holes would damage the Bridge.

Appendix 2

The Environment Agency
The Environment Agency will have to be notified of the proposed works in advance of the Contract being let

The structure is situated on the Little London Stream, a classified main river under the jurisdiction of the Agency. Any works in, over, or under the channel of the watercourse or in its banks within 8 metres from the top of the channel will require the prior consent of the Agency under Section 109 of the Water Resources Act 1991 and/or Byelaws.

The works will require an "Application for works affecting watercourses and/or flood defences" to be submitted to and approved by the Agency, prior to the commencement of work. A 2 month determination period applies and a 50 fee will have to accompany the application.

3 sets of appropriate drawings will be required to support any application (site location map, detailed structure layout plans and cross sections), all indicating clearly the type and extent of the repair works and how they may affect the river channel. All relevant dimension/levels must be included.

Temporary works that will be required within the river channel (or within the structure itself) - for example the erection of scaffolding or similar "safe working platforms, will require temporary works approval prior to the commencement.

As with any works affecting river channels the extent of both permanent and temporary works should be minimized so as not to adversely affect the channel flow/capacity or structural integrity etc. Due regard should also be taken to limit any general environmental impact, pollution control measures and fishery interests.

The timing of the works could be an issue to avoid the bird breeding time and the works should avoid impeding fish movements. The Agency encourages applicants to seek the independent advice of an Ecologist on such issues and any recommended mitigation works/procedures. If a diversion of the river is essential and cannot be avoided then this will usually impose further restrictions (avoid the winter months when high flows are expected etc). A suitably experienced Water Engineer would advise on such matters, although this should not be necessary on this project.

With any temporary works consideration should be given to the following:-

1. The maximum river and flood opening width restriction

2. The top level of any cofferdams

3. The dimensions if any diversion channels

4. The minimum temporary support spacing

5. The time of year

6. The duration of the works

7. The consequences of flooding during the life of the works

8. The requirements for reinstatement on completion of the temporary works

9. Views on the temporary or permanent impact on the environment

The Agency has provided Stuart Page Architects the application form and guidance notes and a copy of their Pollution Prevention Guidelines (PPG5).

A preliminary meeting with the Agency will be an important precursor to an application for works on site and will prevent unnecessary delays.

Appendix 3

Approximate Costs

Since this report may be used for tendering and similar, the details of estimated costs have been withheld but may be requested. 

Appendix 4

Ecology Survey

Corylus and Dolphin Ecology were asked to submit budgets but Dolphin were unable to submit a proposal for this work due to prior commitments.

Corylus Ecology and Stuart Page Architects have worked together on other sites where historic structures and the natural environment are involved.

We believe that local practices offer a good, specialist service, combined with local knowledge.

Corylus would investigate the structure using an endoscope to check cavities in the masonry for the presence of bats.

If suitable features exist then two emergence surveys would need to be undertaken during May and July. This would involve two surveyors and echo-location and recording equipment.

The bridge inspection would cost 225.00. Two emergence surveys would cost 422.00.

If bats are found to be using the site then Defra/Natural England will have to be informed and a license obtained for undertaking the work. This is not included in the estimate and would have to be negotiated separately.

An initial inspection of the site, included in the above fees will indicate what other species might be significant on the site.

A search of biodiversity records plus the analysis of records as a desk-top survey would cost 480.00.

This is based on the Environment Agency Defra and Natural England recognizing that the works to the bridge have a limited effect on the water course and landscape.

Stuart Page February 20 2007