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Sea Wall Report
CHORD Project Helensburgh – Sea Wall & Foreshore
The aim of this report is to provide recommendations for the treatment of the sea wall and
foreshore. The CHORD project represents a large investment in community facilities on the
esplanade which will be dependent on the sea wall for protection. The CHORD project will
also run adjacent to the foreshore and will be directly affected by its appearance. Works to
the sea wall and foreshore would bring significant benefits to the CHORD proposals but were
outside the client’s original brief (18th August 2009). This brief assumed that the sea walls of
the esplanade were structurally sound and required only minor repair work and that the
foreshore was regularly maintained by ABC.
Subsequent investigation of the sea walls conducted by OCSC in March 2010 (refer to
Appendix 2) revealed that although the walls are generally sound they are being undermined
by wave action and further investigation is needed to give an accurate picture of the
structural significance of this. The OCSC report also observed that maintenance of the wall
(including grouting work) is required to maintain their structural integrity.
In addition the public consultation process also highlighted the poor condition of the
foreshore and so in May 2010 (refer to Appendix 3) OCSC investigated the options for
improving this. The report concludes that the visual quality of the foreshore can only be
maintained through a regular cleaning strategy and that even with the installation of a
coastal defence system to retain more sand and reduce wave erosion this would still be the
case.
These surveys raise enough issues about the CHORD approach to the sea wall and foreshore
for it to be prudent at this stage to review their treatment.
SEA WALL
Project Objectives
To protect and enhance the proposed CHORD work on the esplanade
To prevent damage to the existing sea wall
To improve the visual appearance of the existing sea wall
To improve public accessibility to the foreshore
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Sea Wall Report
Sea Wall Option 1 - Do minimum (£60,000 allocated)
Specific works
Localised repairs to the existing sea wall using concrete and resins
Pros
A provisional sum for this work is included in the CHORD budget
Cons
The appearance of the existing sea wall may detract from the other CHORD enhancements
Exposed wall footings and other structural issues are not addressed.
Sea Wall Option 2 – Render Existing Wall (£175,000) *cost pending confirmation from specialist
Specific works
Option 1 plus repairs to the wall foundations followed by the application of a surface render
(eg. ‘spraydeck rapid’) to unify the appearance of the wall and its footing.
Pros
Improved appearance in context of the CHORD enhancements
Cons
Durability of the surface treatment unpredictable due to the extreme conditions
Sea Wall Option 3 - Structural (£70,000 - £350,000)
Specific works
Rebuilding existing sea wall
Pros
A new wall may be more attractive than the existing one
Guaranteed long term protection for CHORD enhancements from the sea
Opportunity to provide improved accessibility to beach front
Cons
Significant cost of this work
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Sea Wall Report
FORESHORE
Project Objectives
To provide an improved setting for the proposed CHORD work on the esplanade
To improve the visual appearance and amenity of the foreshore
To reduce damage to the existing sea wall
To improve public accessibility to the foreshore
Foreshore Option 1 – Cleaning and recharging Regime (£60,000 - £90,000 per
annum)
Specific works
An initial large scale clean up of beach to remove debris then recharging of the beach with
new sand and the subsequent introduction of a regular maintenance regime to keep the
beach in good condition.
Pros
Attractive appearance of the foreshore
Increased use of the foreshore by visitors and public
Improved perception of the town
Cons
On going annual financial commitment
Foreshore Option 2 – Engineered Solution (£70,000 - £350,000)
Specific works
The use of physical barriers to allow the accumulation of sand on the foreshore e.g. artificial
reef or near shore breakwater
Pros
Attractive appearance of the foreshore
Increased use of the foreshore by visitors and public
Cons
Further investigation of the marine conditions required
May result in a visually intrusive structure depending on solution adopted
Planning permission and consent from Scottish Executive may be required
Commitment to regular cleaning of foreshore will still be necessary
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Sea Wall Report
Recommendations
Sea Walls
OCSC have carried out a preliminary review of the current condition of the sea wall and the
proposed CHORD works will help to improve the wall’s short term structural integrity.
However, this work is not sufficient to fully investigate the wall’s long term integrity and will
have limited impact on its present appearance. Option 2 is the most cost effective way of
addressing the appearance of the wall but its outcome is uncertain and the natural stone wall
(with localised enhancements and remedial repairs) may actually have more character than
would be achieved by a homogenous render that may weather poorly over time. The only
option that guarantees an improved appearance to the wall and its long term structural
integrity is Option 3 which requires a significant financial commitment.
Foreshore
OCSC have carried out a high level review of the current condition of the beach and its
maintenance regime and have provided outline proposals for improving it's quality including
beach nourishment/recharging, near shore breakwaters and artificial reefs. Further detailed
studies need to be carried out before a decision can be made on which solution best suits the
requirements of the West Bay. However, it is clear that any solution will require an ongoing
cleaning and maintenance regime and a financial commitment to Foreshore Option 1 which
will bring significant benefits to the CHORD project.
In summary, unless there are sufficient funds available to rebuild the sea wall it seems the
CHORD approach of localised repairs is the best short term option. The OCSC preliminary
report describes the condition of the wall ‘as generally sound’. However, the poor condition
of the foreshore is a concern. The success of the CHORD project could be compromised by
the condition of the adjacent foreshore. In addition to improving the appearance and useability of the beach, Foreshore Option 1 would also improve the appearance of the sea walls
and combat undermining from wave action.
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Appendix 1 –OCSC initial sketch diagrams of sea wall options
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Sea Wall Report
Appendix 2 – OCSC Visual Inspection report
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VISUAL STRUCTURAL INSPECTION REPORT
RIVER WALL ALONG THE WEST BAY ESPLANADE, HELENSBURGH
PROJECT NO. A242S
15th MARCH 2010
15th March 2010
PROJECT NO. A242S
VISUAL STRUCTURAL INSPECTION REPORT
RIVER WALL ALONG THE WEST BAY ESPLANADE, HELENSBURGH
INDEX
PAGE
1.0
INTRODUCTION
1
2.0
BRIEF
1
3.0
SCOPE
1
4.0
DESCRIPTION OF STRUCTURE
1
5.0
OBSERVATIONS
2
6.0
RECOMMENDATIONS
3
APPENDED:
Layout Drawing
Photographs
Appendix A
Appendix B
15th March 2010
PROJECT NO. A242S
VISUAL STRUCTURAL INSPECTION REPORT
RIVER WALL ALONG THE WEST BAY ESPLANADE, HELENSBURGH
1.0
INTRODUCTION
This report has been prepared at the request of Argyll & Bute Council as part of
the Redevelopment of the West Bay Esplanade project The report is based on
a visual structural inspection only carried out on the 14th March 2010 by Martin
McCrossan, Regional Manager (Scotland) with O’Connor Sutton Cronin
Consulting Engineers. Weather conditions during the inspection were generally
sunny following a period of heavy rain.
2.0
BRIEF
A visual structural inspection report was requested by Argyll & Bute Council to
assess if the sea wall along the West Bay Esplanade from William Street to
Colquhoun Street is structurally sound as had been originally reported in the
‘Helensburgh – Redeveloping the West Bay Esplanade’ project initiation
document.
3.0
SCOPE
This is a report on the general condition of the sea wall based on a non-invasive
inspection.
All dimensions noted within the report are approximate and a dimensional
survey was not carried out as part of the inspection.
Details of the design and construction of the sea wall are unknown and this
report does not comment on the overall structural capacity or stability of the wall.
No material testing has been carried out as part of the report and any comments
made on materials within the report are based solely on a visual grading of
materials.
No monitoring of the sea wall has been carried out and therefore this report
does not comment on any ongoing movement or issues which may be present,
4.0
DESCRIPTION OF STRUCTURE
The sea wall is approximately 340m in length from and varies in height from
approximately 0.9m above ground level at the Eastern end adjacent to
Colquhoun Street to approximately 2.2m high to the Western end adjacent to
William Street with a sloped face at between approximately 24 and 35 degrees.
The construction of the wall varies along its length although it is typically a
natural stone / mortar composite.
The construction of the wall between Colquhoun Street and James Street
consists of large natural stones tightly packed at the bottom of the wall and
closely packed long and thin stones to the top. To the West of the monument
adjacent to James Street a section of the sea wall appears to have had remedial
work carried out in the past, with fewer natural stones visible and larger sections
of mortar / concrete patching. Refer to section 4.0 of Appendix B. Moving
West from James Street the construction of the wall changes to that of long
narrow vertical stones on a fairly regular spacing. Approximately 20m West of
the monument the construction changes to a horizontal pattern of long narrow
natural stones in a mortar bed for approximately 7m before reverting to the
previous vertical pattern. The wall then continues on a combination of long
narrow vertical natural stone and larger natural stone sets in a mortar / concrete
bed.
Along its length the sea wall is interrupted by 3 sets of inset steps, a drainage
outflow pipe and a large culvert. Refer to Appendix A for locations.
Approximately half way between James and John Street the foundation of the
wall is exposed above the seabed level and remains exposed for approximately
85m to the West before it steps down below seabed level. The foundation is
formed in concrete and where exposed is between 300-450mm deep and
projects between 1100-1300mm from the face of the sea wall. Weep holes are
visible at mid-depth of the foundation at between 3 and 4m centres. Significant
portions of the foundation show signs of overspill concrete also exposed above
seabed level.
5.0
OBSERVATIONS
The general condition of the wall is relatively good with few significant structural
defects and no visible sign of structural instability. There is however a number of
issues which occur fairly consistently along the length of the wall as discussed in
the following sections.
5.1
Grout Loss
Along the length of the wall there are constant signs of grout loss between the
natural stones however it is particularly noticeable at the base of the sections of
wall constructed using the long narrow sections of natural stone. Refer to
section 5.1 of Appendix B.
5.2
Undermining of Foundation
The foundation is exposed above ground for approximately 85m with the full
depth of the toe being exposed for approximately 70m. There is a large section
of overspill concrete also exposed above sea bed level however there is a 10m
section where the sea bed has been washed away and the toe of the foundation
has been undermined slightly. Refer to section 5.2 of Appendix B.
5.3
Foundation Damage
There are 3 locations along the exposed section of the foundation which show
signs of cracking or where a section of the foundation toe has broken away.
These locations may relate to construction joints during the construction. On one
of the broken sections a 6mm reinforcement bar can be seen protruding. Refer
to section 5.3 of Appendix B.
5.4
Debond of Sea Wall Base from Foundation Toe
There is a 5-10m long section where the base of the sea wall and the foundation
have become debonded and a joint has opened up between the two. This
occurs to the West of John Street. Refer to section 5.4 of Appendix B.
5.5
Drainage Outfall
To the West of John Street the sea wall is penetrated by a drainage outfall pipe.
One of the hinges on the non-return flap valve has corroded and the flap valve is
hanging from the second hinge. Refer to section 5.5 of Appendix B.
5.6
Steps
There are three sets of in-set steps providing access from the esplanade to the
beach. The steps have been constructed in concrete and are showing signs of
considerable wear however they would appear to be structurally sound. The
steps between Colquhoun Street and James Street have cracks across the side
aprons. Refer to section 5.6 of Appendix B.
6.0
RECOMMENDATIONS
In general the condition of the sea wall is relatively good however as noted in
Section 5.0 there are a number of areas that require some attention.
6.1
Grout Loss
The presence of small pockets of grout loss is not considered of major structural
significance at this time however if left in it’s current state the problem will
gradually get worse as the result of both wave action creating pressure pockets
within the body of the wall and freeze-thaw action causing the mortar to be
fractured further. It is recommended that a maintenance regime is put in place to
locate the worst affected areas, which should be cleaned out to remove all
surface laitance and grouted with a high strength non-shrink grout suitable for
marine environments such as ‘Expocrete UA’ by Fosroc.
6.2
Undermining of Foundation
From the visual inspection it is unclear how much undermining of the foundation
has occurred and what / if any impact that has had on the overall stability and
function of the sea wall. Further investigation is recommended in co-ordination
with Argyll & Bute Council to determine the exact extent.
6.3
Foundation Damage
Although there are signs of damage to the foundation they would appear to have
had limited impact on the overall stability or function of the sea wall. There were
no signs of differential movement between adjacent sections of foundation or
wall. It is recommended that that the foundation is broken back locally to provide
a minimum section of 450mm and the section is then re-cast with dowel bars
drilled into both sides.
6.4
Debond of Sea Wall Base from Foundation Toe
The occurrence of a joint between the base of the wall and the foundation was
limited to one section of between 5 and 10m length. There would appear to be
no sign of slippage between the wall and foundation and it is likely this has been
caused by the ingress of water at the base of the wall being subject to freezethaw action. It is recommended that the sections of mortar between the stones
in this area are broken out, cleaned and re-grouted with ‘Expocrete UA’ by
Fosroc.
6.5
Drainage Outfall
The hinges of the flap valve should be removed and new hinges welded to the
existing outfall pipe and a new flap valve installed.
6.6
Steps
The steps between Colquhoun Street and James Street have cracks across the
side aprons and these cracks should be injected with a resin which is suitable
for marine environments to prevent the ingress of water which over time will
potentially lead to the steps themselves cracking.
This is a report for the use by Argyll & Bute Council only.
MARTIN McCROSSAN
For O’Connor Sutton Cronin
APPENDIX A
LAYOUT DRAWING
APPENDIX B
PHOTOGRAPHS
4.0 - Concrete Patching at Monument
5.1 – Grout Loss West of Colquhoun Street
5.1 – Grout Loss East of Monument
5.1 – Grout Loss West of Monument
5.1 – Grout Loss West of Monument
5.1 – Grout Loss 15m East of Culvert
5.2 – Exposed Foundation
5.2 – Exposed Foundation
5.2 – Exposed Foundation
5.2 – Exposed Foundation
5.2 – Exposed Foundation
5.2 – Exposed Foundation Undermining
5.2 – Exposed Foundation Undermining
5.3 – Exposed Foundation Damage
5.3 – Exposed Foundation Damage
5.3 – Exposed Foundation Damage
5.3 – Exposed Foundation Damage
5.3 – Exposed Foundation Damage
5.3 – Exposed Foundation Damage
5.4 – Debonding at Base of Sea Wall
5.5 – Drainage Outfall
5.6 – Steps between Colquhoun Street and James Street
5.6 – Steps between Colquhoun Street and James Street
5.6 – Steps between Colquhoun Street and James Street
5.6 – Steps between James Street and John Street
5.6 – Steps between James Street and John Street
DUBLIN OFFICE
9 Prussia Street
Dublin 7
GALWAY OFFICE
The Grainstore
Lower Abbeygate St.
Galway
CORK OFFICE
Unit C, Building 6800, Ave 6000
Cork Airport Business Park
Cork
BELFAST OFFICE
4C Weavers Court
Linfield Road
Belfast BT12 5GH
Tel. 00353 (1) 8682000
FAX 00353 (1) 8682100
Tel. 00353 (91) 560310
FAX 00353 (91) 532547
email: [email protected]
Tel. 00353 (21) 5004900
FAX 00353 (21) 4299177
email: [email protected]
Tel. 0044 (0) 2890244444
FAX 0044 (0) 2890244442
email: [email protected]
SCOTLAND OFFICE
Suite 4/4,
53 Bothwell Street,
Glasgow,
G2 6TS
ROMANIAN OFFICE
OCSC si Asociatii
Str. Ion Campineanu, no. 1,
sc. A, II-2 (second floor, unit 2), Sector 1., Bucharest
Postal code: 010031
Romania
Tel. +040 (31) 4256384
WARSAW OFFICE
OCSC Sp. z.o.o.
Ul. Targowa 43
03-728 Warszawa, Poland
FAX +040 (31) 4256387
email: [email protected]
email: [email protected]
email: [email protected]
LONDON OFFICE
40 Bowling Green Lane
London
EC1R 0NE
Tel. 0044 (0) 2074157120
FAX 0044 (0) 2074157012
email: [email protected]
ABU DHABI OFFICE
(Also serving Qatar)
P.O. box 35899
#203 Golden Falcon Tower
Hamdan St.
Abu Dhabi
UAE
Tel. +97150 8626273
email: [email protected]
Tel. +44 (0)141 404 2785
FAX +44 (0)28 9024 4442
email: [email protected]
RUSSIAN OFFICE
OOO “O’CONNOR SUTTON CRONIN”
Building 26,
Novocheryemushkinskaya,
Moscow,
117218,
Russia
Mobile (RUS) +7 916 065 4390
Mobile (INT’L) +353 86 172 4018
email: [email protected]
LIBYAN OFFICE
O'Connor Sutton Cronin - Libya
AL-Ankabout Engineering & Technical
Consulting Office
Ain-Zara, In-front of AL-Fateh UniversitySection B
Tripoli-Libya
PO.BOX 4811 Ain-Zara
Tel / FAX 00218-214623279
email: [email protected]
O’CONNOR SUTTON CRONIN
International Multi-disciplinary Engineers
Tel. 0048 (22) 7410020
FAX 0048 (22) 6183013
COSTA RICAN OFFICE
Apdo 86-1Z00
Pavas
San Jose
Costa Rica
Tel. +353 86 8198459
email: [email protected]
Argyll and Bute Council
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Sea Wall Report
Appendix 3 – OCSC Beach maintenance report
O’CONNOR SUTTON CRONIN
Consulting Engineers
Suite 4/4, Mercantile Chambers
53 Bothwell Street,
Glasgow, G2 6TS
Ph. 0141 404 2785
Fax 028 9024 4442
Job Ref: A242S
Title: Helensburgh CHORD
Client: Argyll & Bute Council
Date: May 2010
BEACH MAINTENANCE
Introduction
The current condition of the beach adjacent to the pier and West Bay Esplanade has
been raised as a key concern during the public consultation phase of the CHORD
projects in Helensburgh.
As a result O’Connor Sutton Cronin have been requested to carry out a high level
review of the current condition of the beach and provide outline proposals for
improving the quality of the beach. The beach as referred to within this paper is the
section from the Western face of the pier and running along the West Bay for
approximately 175m.
It should be noted that there have been no coastal or marine studies carried out as
part of this exercise and all options suggested would require detailed investigation
and design to determine their success.
Current Situation
At present the beach is noted as containing a large amount of coastal/marine litter
especially around the slipway adjacent to the pier. The four main sources of
coastal/marine litter are typically: public littering, the fishing industry, the shipping
industry and the sewage network. Although a full litter survey has not been carried
out, based on a number of visual inspections the main sources of litter would appear
to be timber, plastic, metal (cans etc) and paper however it is likely that under closer
inspection there will also be sewage related debris.
It is believed that the current maintenance regime for the beach includes a quarterly
clean up by means of tractor and rake and that a more regular maintenance regime
had been in place previously. It is also understood that Argyll & Bute Council have in
the past employed seasonal workers for the sole purpose of beach cleaning over a
period of 20 weeks throughout the summer period.
Beach Maintenance
Although the beach is outside the boundary of the CHORD project it is seen as a key
asset to Helensburgh and the success of the environmental improvements to the
West Bay Esplanade is likely to be undermined if the beach itself is not improved and
maintained.
In terms of improving the visual appearance of the beach as it currently stands the
options would be:



Carry out large scale clean up of the beach to remove all litter/debris
including all litter trapped in the Pierhead gabion walls.
Beach Nourishment/recharging. The initial outlay is likely to be between
£10,000-50,000 dependant upon the source of the recharging material.
Provide additional resources in the form of two council employees to
manually remove litter and debris from the beach on a weekly or bi-weekly
1
O’CONNOR SUTTON CRONIN
Consulting Engineers
Suite 4/4, Mercantile Chambers
53 Bothwell Street,
Glasgow, G2 6TS
Ph. 0141 404 2785
Fax 028 9024 4442

Job Ref: A242S
Title: Helensburgh CHORD
Client: Argyll & Bute Council
Date: May 2010
BEACH MAINTENANCE
basis as deemed necessary
Invest in a pedestrian operated beach cleaner reducing the manpower to
one person per week
An alternative to this relatively low tech approach would be to incorporate the beach
improvements into an engineered solution that would also act as a form of coastal
protection such as:

Nearshore breakwaters: Normally built of rock at the high water mark they
do not prevent some wave energy to reach further up the beach. They are
visually obtrusive and in storm conditions may allow debris to accumulate
on the upper shore. Costs are in the range of £20,000-£60,000 per 100m
(RLF to provide costs based on drawing A242S/CSK10).
Nearshore Breakwater on the upper foreshore in the Dornoch Firth

Artificial Reefs: Similar to the nearshore breakwater however they are
located further from the shoreline and will be submerged for at least part of
the tidal cycle. When submerged they may cause navigation problems for
anybody looking for access to the slipway. Costs are in the range of
£40,000-100,000 per 100m (RLF to provide costs based on drawing
A242S/CSK10).
With both schemes we would require planning consent and also it will be likely that
consent will be required from the Scottish Executive Rural Affairs Department under
the Food and Environment Protection Act 1985 and also possibly the Scottish
Executive Development Department (Transport Division) if they are deemed to
endanger navigation.
Conclusions
Essentially the visual quality of the beach can only be maintained through a regular
cleaning strategy and it is recommended that the council’s beach cleaning budget is
reviewed in line with the aspirations of the CHORD projects and the overall benefits
that are to be gained to Helensburgh as a whole. If it is decided that a form of coastal
2
O’CONNOR SUTTON CRONIN
Consulting Engineers
Suite 4/4, Mercantile Chambers
53 Bothwell Street,
Glasgow, G2 6TS
Ph. 0141 404 2785
Fax 028 9024 4442
Job Ref: A242S
Title: Helensburgh CHORD
Client: Argyll & Bute Council
Date: May 2010
BEACH MAINTENANCE
defence system should be incorporated this will not remove the requirement for
ongoing maintenance and cleaning of the beach but it will help to reduce the
resources required to do so. Further studies will be required and a marine
engineering consultant will need to be appointed to further develop the options.
3