PRINCIPAL INSPECTION
OF
GRAND UNION CANAL – AYLESBURY ARM
Lock 12
Functional Location: GA-005-001
Chainage Code: GA-00416
Date: 12 January 2006
PRINCIPAL INSPECTION - MMS SUMMARY AND SIGNING OFF SHEET
Note: Only recommended changes to the existing MMS record need be completed
General Asset Details
Functional Location
GA-005-001
Chainage Code
GA-00416
Lower Chainage of Asset
Location
Buckland
Parish, District Name
Grid Reference
487732, 213924
Centre of Asset
Grid Reference (Landranger)
SP 877 139
Centre of Asset
Property Reference
Cross Ref to PMS
Name/Local Name
Buckland. Lock 12
Engineering, Local Name
Business Unit
7100
BU Code Number
Canal Code
GA
MMS Standard Canal Code
Asset Type
10
Asset Type (1-25)
Budget Centre
CODA Budget Centre
Owner
BW
BW if wholly or partly owned
Heritage Reference
Details of Heritage Status
Year of (Re)Construction
If known
Interested Parties
Any 3rd Party Interest
Impairment Date
Vul or Imp Date (dd/mm/yy)
Vul/Impairment Score
0% to100%
Condition Grade
D
A,B,C,D or E
Condition Date
12/01/2007
Date of PI (dd/mm/yy)
Serviceability
1
Fitness for Purpose
Consequence of Failure
2
1, 2, 3, 4,5
Full length off lock
24.4m
See AIP2005 Appendix 14
Maximum depth (coping to invert)
3.86m
See AIP2005 Appendix 14
Minimum width (at coping level)
2.40m
See AIP2005 Appendix 14
Type of Lock
SN
See AIP2005 Appendix 14
Number of ground paddles
2
See AIP2005 Appendix 14
Capacity of lock
100m3
See AIP2005 Appendix 14
How is the lock operated
User
See AIP2005 Appendix 14
Level Difference
1.705m
See AIP2005 Appendix 14
Certified Inspector: Jim Cowles
Signature:
________________________________ Date 12 Jan 2007
Regional Engineering / Commercial Manager _________________________________________
Signature:
________________________________ Date: ______________________
Regional Engineer / Other Chartered Engineer _______________________________________________
Signature:
________________________________ Date: _____________________________
SAP updated by: Wouter Nijland
Signature:
________________________________ Date: 22/01/07
Executive Summary
Lock 12 is a narrow lock on the Grand Union Canal Aylesbury Arm approximately 2 kilometres North
of Aston Clinton
The lock head gate has a significant leak at the cill and its balance beam handrail needs securely
fixing. There is a vertical crack in the south lock wall and the north west quadrant has significant
cracking and is subsiding. Some brickwork repairs are required in the medium term.
Introduction
A Principal Inspection of the above structure was undertaken on 12 January 2007, by J.Cowles. The
weather on the day was damp and 8°C. A previous Technical Services Structures Report dated 17
January 1997 was consulted prior to the inspection. PM Notifications in 2004 and 2006 reported
leaks from the chamber and damage to the NW quadrant and brickwork cracks.
General Description
Lock 12 is a brick built narrow lock with two mitred gates at the bottom and a single gate at the top,
located on the Grand Union Aylesbury Arm north of the village of Buckland. The pound above the
lock is approximately 1.2 kilometres long. The canal at this point runs from E to W. The lock is
approximately 24.40m long between quoins with a chamber depth of 3.86m, width of 2.4m and a
drop of 1.705m.
The lock is not within an area of particular environmental sensitivity. The area is a Non-Statutory
Wildlife Site.
Observations
Lock Gates
The single head gate is of steel construction. The tail gate is a double mitre gate constructed from
timber.
The head gate has significant leakage at cill level, and small leak at the north side at high level.. The
handrail is loose. This is fixed to a timber beam which in turn is bolted on to the side of the balance
beam. This latter fixing is not secure. There are ground paddles on either side.
The tail gates are in generally good condition, having been replaced in 1993. There is a leak
between the gates at low level There are paddles on each gate. No leaks were observed from the
paddles.
Both gates have timber balance beams which have suffered from loss of protective paint. Splits and
shakes contain moss growth to horizontal surfaces. The moss should be raked out and new paint
applied to protect the balance beams from further decay.
Chamber Walls
The chamber walls are brick with stone copings.
The North wall is generally sound and well pointed, except at the bedding of the copings at the West
end (where some vegetation is establishing) and within the tail gate recess where there is also
missing bricks and damage to brick faces. Water is seeping through the wall 6m from the head gate,
at 525mm above low water level.
The South (towpath side) chamber wall is inscribed “1911” and is wel pointed except at the bedding
of all the copings (where some vegetation is establishing) and within the tail gate recess, where brick
faces are damaged. Almost all of the copings are badly spalled at the edge.
There is a vertical crack in centre of the South wall, extending the full depth of the chamber. This is
approx. 3mm wide. There is no discernable lateral displacement. The crack was not reported in the
previous PI.
The vertical crack was reported in a PM Notification Summary in 2004, when leaks down the
embankments on both sides of the canal were observed as soon as the lock is filled. The Notification
also reports, on 06.10.2006, “large offside leak and towpath leak” requiring urgent attention.
Lock Sides
The offside lock landing is grass. It is tidy, level and in reasonable condition. The offside ladder
handrail is loose in its top sockets. A sign “Buckland No.12” is damaged and the BW logo is faded.
The towpath side lock landing is grass and has two mooring bollards. There is no surfacing to define
the towpath. Generally the lock side is well maintained and even with a gentle grass slope down to
the lower level.
Gate Quadrants
The head gate quadrant is a concrete slab (small horizontal crack), with brick upstands. It is in fair
condition.
The South tail gate quadrant is concrete, with bricks at the SE corner, some of which are loose and
require re-pointing.
The North tail gate quadrant is badly damaged. The brick retaining wall has a large crack (40mm
vertically, 20mm horizontally), to the west face. This crack was reported in the previous PI,
photographs showing it to be about 15mm vertically at that time. The concrete quadrant slab has
cracked and subsided at the retaining wall, loosening many of the upstand bricks (one missing). The
quadrant has moved away from the lock structure (25mm at South East corner). The lock structure
appears unaffected by the quadrant damage. This quadrant damage was reported in a PM
Notification Summary on 15.08.2006.
Approach Walls
The upstream approach walls appeared in fair condition. Some of the stone copings have spalled
faces.
The Western approach walls are both brick with stone copings. Some repointing is required,
especially below some of the copings, and beneath the gate collar on the north side.
Side Ponds
N/A
Stop Plank Grooves
There are top plank grooves 3 metres upstream of the head gate. There are no stop plank grooves
at the downstream end of the lock.
Approach mooring
There are 2 No. mooring bollards upstream on the towpath side and 2 No. mooring bollards on the
downstream towpath side The towpath is unsurfaced.
Operation
There were no problems with operation of the lock.
Access
Access by road is to Bridge No 9 (Red House Bridge) 2km north of Aston Clinton, where parking and
turning is possible. The lock is 540m East along the towpath. Access from Bridge 8, North of
Buckland has no parking (verges very soft in wet) and limited turning and is not recommended.
Discussion
The lock requires repairs to stem the leaks at the gates. The North West quadrant needs rebuilding
before further erosion and damage renders the quadrant unusable. The upstream gate handrail
requires firmly securing. General vegetation clearance and pointing will avoid further deterioration of
brick and stone walls. Balance beams require clearing of moss, and repainting
Assessment
No load assessment calculations were carried out as part of this inspection.
Grades
Condition Grade
D
Structure is functioning but with some repairs
required.
Serviceability
1
May be operated without restriction
Consequence of Failure
2
Farmland and possibly dwellings would be
affected by structural collapse.
Inspection Requirements
Next scheduled Principal Inspection 2017.
length inspection requirements:
Monitor leakage from lock chamber, head gate and tail gate
Monitor continuing movement of North West quadrant.
Works Recommendations
The lock is in useable condition but repairs should be carried out to stem chamber and gate leaks,
rebuild the NW quadrant and prevent deterioration to the lock walls.
Securely fix head gate handrail to balance beam.
The following works should be undertaken: -
Recommendation
Cost Estimate
Priority
Notification No.
1. Investigate
leaks
to £20,000
5: 1 year
10441928
chamber walls. Repair
2. Repair leaks to head gate
£5,000
5: 1 year
10441930
3. Repair leaks to tail gate
£2,500
5: 1 year
10441931
4. Rebuild NW quadrant
£5,000
6: 5 years
10441932
5. Repoint brick/stone walls
£1,000
5: 1 year
10441933
6. Seal pisser at North wall
£500
6: 5 years
10441935
7. Seal vertical crack to south £500
5: 1 year
10441936
wall to prevent ingress of
water
8. Secure head gate handrail
£200
5: 1 year
10441939
9. Clear vegetation (include 0
5: 1 year
10441940
within annual contract)
Total
£34,700
Photographs
Plate 1 - General view, from the East
Plate 2 - Head Gate, showing loose handrail
Plate 3 - Head Gate, showing leaks at sill
Plate 4 - Head Gate, showing leak below collar
Plate 5 - Tail gates
Plate 6 – Tail gate leak
Plate 7 - Tail gate recess on North wall, showing eroded pointing and missing bricks
Plate 8 - Vertical crack – South lock wall
Plate 9 - Vertical crack – South lock wall – close-up
Plate 10 - Pisser in north lock wall
Plate 11 - North west quadrant showing subsided concrete slab
Plate 12 - North West quadrant retaining wall
Plate 1 - General view, from the East
Plate 2 - Head Gate, showing loose handrail
Plate 3 - Head Gate, showing leaks at sill
Plate 4 - Head Gate, showing leak below collar
Plate 5 - Tail gates
Plate 6 – Tail gate leak
Plate 7 - Tail gate recess on North wall, showing eroded pointing and missing bricks
Plate 8 - Vertical crack – South lock wall
Plate 9 - Vertical crack – South lock wall – close-up
Plate 10 - Pisser in north lock wall
Plate 11 - North west quadrant showing subsided concrete slab
Plate 12 - North West quadrant retaining wall
Appendices
Location Plan
Bridge 9
Red House Bridge
Lock 12 (Buckland Lock)
Sketch of Structure: GA-005-001