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Before the Environment Court at Auckland ENV-2013-AKL-000174
In the Matter of the Resource Management Act 1991
And
In the Matter of Notice of Motion under Section 87G requesting the granting of resource consents to Waiheke Marinas Limited to establish a Marina at Matiatia Bay, Waiheke Island, in the Hauraki Gulf
Evidence of John Michael Leman on behalf of Waiheke Marinas Ltd
Dated 30 April 2014
Richard Brabant/Jeremy Brabant Barristers
Broker House, Level 2, 14 Vulcan Lane PO Box 1502, Shortland St
Auckland City Ph: 09 309 6665 Fax: 09 309 6667
Introduction 1. My full name is John Michael Leman. I am a Consulting Engineer and hold a
Bachelor of Engineering (University of Auckland). I am a Member of the Institute
of Professional Engineers New Zealand.
2. I have 32 years experience as an Engineer. My professional services have
predominantly comprised marine works, and in particular, marina facilities
design.
3. I have been involved in the design of marina developments in New Zealand,
Australia, the Pacific, South-East Asia, China and the Middle East. New Zealand
projects within the Auckland region include Gulf Harbour and Pine Harbour.
4. My involvement with the Matiatia Marina project commenced in May 2012. My
commission was to review the design of the April 2011 marina proposal as a result
of submissions, particularly those in relation to the wave climate in the bay, ferry
wakes and movements, wave protection, recreational/commercial vessel
navigation and safety.
5. To further consider wave aspects, a programme of wind and ferry wave
measurements was undertaken by MetOcean Solutions1 and further wave
modelling by Cardno2. These studies, in conjunction with a more in-depth review
of acceptable marina wave climate criteria by my consultancy (International
Marina Consultants), formed the basis for refinement and finalisation of the
marina facilities proposal.
6. I have visited the site on several occasions including March 2014 where I visited
other possible marina sites around Waiheke Island that were raised as potential
alternative marina development locations.
7. I have read and agree to abide by the Environment Court’s Code of Conduct
for Expert Witnesses as specified in the Environment Court’s Consolidated
1 MetOcean Solutions report P0099-01 dated March 2012 entitled “Matiatia Bay Measured Wind and Ferry Wakes”. 2 Cardno Report LJ3020/R2781dated 23 October 2012 entitled “Matiatia Wave Climate and Preliminary Marina Design”.
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Practice Note 2011. This evidence is within my area of expertise, except where I
state that I rely upon the evidence of other expert information as presented to
this hearing. I have not omitted to consider any material facts known to me that
might alter or detract from the opinions expressed by me.
Scope of Evidence 8. My evidence covers the following matters:
A. Marina Location
B. Matiatia Site Conditions
C. Marina Design including:
- General Design Requirements - Wave Height Limit Criteria - Review of Ferry Wake Waves - Marina Wave Protection - Marina Entrance - Marina Berths - Public Facilities - Reclamation - Dredging
D. Alternative Locations Review
A. Marina Location 9. The proposed marina facilities are located within the North-East portion of
Matiatia Bay as depicted on Figure 1.
10. The proposed marina berths are north of the existing wharves to avoid conflict
with existing ferry, wharf and boat ramp activities (refer Figure 2). Similarly, the
small associated reclamation area is also to the north of the existing wharves and
boat ramp facilities.
11. Road access to the site is well established and by sea it is a gateway to the
island from Auckland. The site has existing depths suitable for a marina with
minimal dredging and is a designated vessel mooring area. Services
infrastructure to the Bay already exists.
12. Matiatia has therefore been selected as the preferred site for a marina facility.
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B. Matiatia Site Conditions
B(i) Seabed Levels 13. Within the context of a marina proposal, relevant site conditions are summarised
as follows:
14. The embayment within the proposed marina berths location has existing seabed
levels typically between 2 metres to 4 metres below Chart Datum, with a
comparatively small area of shallower water requiring dredging on its eastern
extremity.
15. The marina is located sufficiently south to avoid the shallow area to the north
(refer Figure 3).
B(ii) Wind and Wave Conditions
16. As depicted on the attached Cardno Figure 2.1, wind data from the Manukau
Airport highlights a predominance of higher wind strengths from the South-West
quadrant for the region.
17. Matiatia Bay is exposed to winds and waves from this direction, albeit with a
limited fetch across to Motutapu Island.
18. As detailed in the Cardno wave study, wave heights for various storm events
have been determined as follows:
Average
Recurrence Interval (Years)
Wave Height Hs (m)
Wave Period Tp (s)
Mean Wave Direction (oTN)
1 0.56 2.3 255 10 0.67 2.5 254 50 0.76 2.5 254
19. MetOcean Solutions two weeks of wind and ferry wave measurements at the site
depicted mean significant wave height for wind and ferry wave ambient
conditions was 0.1 metres and largest significant wave height at 0.39 metres.
Mean periods for these wind waves were within the range of 1.5 seconds to
2.5 seconds.
20. Regular ferry services operate from the terminal just to the south of the marina
site. Ferries entering and leaving the bay regularly create wake waves that will
propagate to the site.
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21. The largest wake wave measured was 0.344 metres. The highest events (waves
larger than 0.25 metres) typically had wave periods in the range of 4.5 seconds
to 9.0 seconds.
22. The mean wake wave height towards the western end of the site was 0.193
metres and 0.142 metres at the eastern end.
23. Wake waves were predominantly transverse wake waves (travelling in the same
direction as the ferry) from ferries entering Matiatia.
B(iii) Tides and Currents
24. Typically, as you go further up a harbour, the tidal range increases. As expected,
the Matiatia tidal range is therefore less than Auckland’s (by about half a metre).
25. As detailed in the Cardno report, the Tidal Plane at Matiatia Bay is characterised
as follows (relative to Chart Datum):
MHWS 2.8 metres MHWN 2.4 metres MSL 1.6 metres MLWN 0.6 metres MLSW 0.3 metres
26. Highest Astronomical Tide is predicted at 3.1 metres. There are no significant
tidal currents within the bay.
27. Long-term tidal data from Auckland shows that sea level rise to 2050 may be 0.1
metres (excluding recent climate change projections). NIWA and Ministry of
Environment (2008) recommend a sea level rise to 2100 of between 0.18m and
0.59m. I consider a 50 year time horizon allowance of 0.4m satisfactory for
infrastructure design.
B(iv) Infrastructure and Facilities
28. Road and services to the bay and public amenities are already established.
There is a significant amount of established car parking. However, convenient
additional dedicated marina parking is necessary.
29. There are some 52 moorings within the proposed marina area that will be
accommodated within the marina development or relocated.
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30. Extension to the marina site of power and telecommunications will be
undertaken.
C. Marina Design
C(i) General Design Requirements 31. General marina design requirements for safety, usability, navigation, services
requirements, marina berths configurations and depth requirements are set out
in the relevant Code “Guidelines for Design of Marinas” AS3962-2001, which is
adhered to for design of this marina proposal.
32. It is of paramount importance to provide a safe all-weather haven for vessels
and marina patrons. To this end satisfactory wind wave height limit criteria need
to be achieved for predicted storm conditions. For the Matiatia location,
satisfactory ferry wake limit criteria also need to be achieved.
33. The following section outlines the determination of those limit criteria.
C(ii) “Satisfactory” Wave Height Limit Criteria
34. For the analysis of any wave protection solutions it is necessary to establish an
acceptable set of criteria from which a judgement can be reached on
achievement of a satisfactory wave climate.
Wind Waves:
35. The determination of a set of (wave height limit) criteria is somewhat subjective,
ranging from what is the limit to be reasonably sure a vessel won’t get damaged,
to what is regarded as ideal for berth users (flat calm).
36. The criteria for acceptable limits in storm conditions has been researched and
referenced in appropriate marina design codes. However, extrapolating this
data has been seen as potentially problematic or inappropriate, particularly with
regard to regular vessel wake situations.
37. The primary point of reference in New Zealand and Australia is the Australian
Standard AS3962 Guidelines for Design of Marinas, Table 4.2, Criteria for a ‘Good’
Wave Climate in Small Craft Harbours.
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TABLE C(ii)
CRITERIA FOR A ‘GOOD’ WAVE CLIMATE IN SMALL CRAFT HARBOURS
Direction and peak period of design harbour wave
Significant Wave Height (Hs) Wave event exceeded once
in 50 years Wave event exceeded
once a year Head seas less than 2s Conditions not likely to occur
during this event Less than 0.3m wave height
Head seas greater than 2s Less than 0.6m wave height Less than 0.3m wave height Oblique seas greater than 2s Less than 0.4m Less than 0.3m wave height Beam seas less than 2s Conditions not likely to occur
during this event Less than 0.3m wave height
Beam seas greater than 2s Less than 0.25m wave height Less than 0.15m wave height
NOTE: For criteria for an ‘excellent’ wave climate multiply wave height by 0.75, and for a ‘moderate’ wave climate multiply wave height by 1.25. For vessels of less than 20m in length, the most severe wave climate should satisfy moderate conditions. For vessels larger than 20m in length, the wave climate may be more severe.
38. The source of the above criteria was a paper presented at a Coastal
Engineering Conference in Cape Town in 1982.
39. As this is contained within the Code, it is still regarded somewhat as a benchmark
and is also quoted within the Matiatia Marina reports. However, although IMC
was significantly involved in the formulation of the overall Code, we also
recognise the limitations of some criteria.
40. Table C(ii) is oriented towards wind generated wave criteria with reference to
50 year and ‘once a year’ events and does not specifically address frequent
wake wave scenarios.
41. It should also be noted that Table C(ii) specifies Significant Wave Height (Hs).
Maximum wave heights can be up to 1.84 Hs as pointed out in the 2011 proposal
– see the A.J. Raudkivi3 report.
42. If you wish to justify a wave height as being acceptable within the Code
parameters you could then look at an extreme case of multiplying the 0.6m
significant wave height for head seas by 1.25 for the ‘moderate’ wave climate
and then by 1.84 to determine a maximum height that could be experienced
within a ‘Code Satisfactory’ marina:
0.6m x 1.25 x 1.84 = 1.38m, which is definitely not acceptable in any marina situation.
3 Raudkivi 2011 Proposal Report
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Wake Waves: 43. By the same token, I do not think it is advisable to try to justify a satisfactory wake
wave criteria by picking or multiplying a number from Table C(ii), particularly if
you try to apply once a year storm wave criteria to regular daily wake waves.
44. I consider there are four primary criteria that need to be addressed when
assessing satisfactory wake criteria. These are user comfort, safety, facility
longevity and maintenance. The latter two are very dependent on the detailed
design of the chosen marina system so cannot be dealt with in any detail at this
stage.
45. As discussed, the choice of acceptable criterion is somewhat subjective, and
complaint-based assessment is obviously a primary source for acceptance
criteria. Marinas (such as Bayswater in Auckland, marinas on the Brisbane River
and around Sydney Harbour) that regularly experience (wake) waves of as low
as 150mm, produce complaints.
46. The primary comfort sensitivity for people in boats is roll, pitch, surge and sway
that can easily fall within the typical sensitive frequencies of marina sized vessel
motion. Experience suggests that any waves within these typical vessel motion
frequencies should be avoided (refer Attachment 1).
47. As evidenced by the Code criteria, head seas are far less problematic and wave
heights around twice that of the beam seas are required to be categorised as
outside the required comfort criteria.
48. Safety typically equates to situations of personal instability onboard due to vessel
rolling and pitching motion, transfer from vessel to dock and potential injury from
limbs between vessel and dock. Instability criteria are typically towards the
upper bounds of the comfort criteria.
49. The US Navy has limits on the maximum amount of acceleration and roll (or
pitch) acceptable on the bridges of vessels.
• Maximum horizontal acceleration: 0.2g • Maximum vertical acceleration: 0.4g • Maximum roll: 8 degrees • Maximum pitch: 3 degrees
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50. These limits reflect survival of equipment and a well prepared crew so are
considered too severe for the casual environment of a marina.
51. Research in the Netherlands reviewed stability criterion for response of the body
to acceleration for various body orientations. A ‘surprise’ stability coefficient was
recommended at 55% of maximum acceleration. Assuming an initial casual
stance, a surprised or disabled body will topple if the acceleration exceeds 0.09g
(0.9m/s2).
52. Comfort criteria research for tall building sway found that walking becomes
difficult when building accelerations exceed 0.04g (0.4m/s2).
53. This is consistent with allowable/tolerable accelerations computed for docks and
the premise that safety criteria are typically twice that of comfort limit criteria.
54. Having established some benchmark criteria, the challenge is then to translate
this to a reasonable form of wave limit criteria (to cross check against the all
important complaint based criteria).
55. The Australian Marine and Offshore Group undertook a study to review
acceptability of pontoon movement. Two pontoons were modelled, Type A,
being a 9m x 3m with Ai having a 6 tonne displacement and Aii 12.7 tonnes and
Type B, a 12m x 4m pontoon with Bi having a 9.9 tonne displacement and Bii 19.8
tonnes. Results are tabulated in Attachment 2.
56. The B type pontoon is considered to reasonably resemble a 40 to 45 foot power
boat and the A type a 30 to 36 foot power boat. As can be seen from the
results, at Hs = 0.1m the horizontal accelerations for head seas have gone above
the abovementioned limit criteria.
57. Attachment 1 depicts results from a Canadian Government Report “Study to
Determine Acceptable Wave Climate in Small Craft Harbours”. As can be seen
from the response graphs, resonance for pitch, heave and roll for wave periods
between 1 to 3 seconds is particularly problematic with sway dominating at
longer periods. Horizontal accelerations due to sway in longer periods therefore
needs due consideration also.
58. It is noted that roll criteria for horizontal acceleration of a body standing on a
floating pontoon is not included within the pontoon and vessel response results.
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59. Analysis of roll for various wave heights and periods has been carried out with
results as follows:
Wave Period Wave Height Body Acceleration *
3 seconds 0.15m 0.04g 3 seconds 0.3m 0.08g 5 seconds 0.15m 0.005g 5 seconds 0.3m 0.001g 7 seconds 0.15m 0.0013g 7 seconds 0.3m 0.0026g
* Body acceleration calculated at body centre of gravity
2.0m above still water level. 60. It is noted that the shorter 3 second wave period results for 0.3m wave height
and 0.15m wave height roughly coincides with the earlier derived casual stance
surprised or disabled body topple acceleration of 0.09g and 0.04g for the
comfort limit. This also correlates with Marina Code ‘Good’ once-a-year wave
climate criteria for the 0.3m and marina complaint feedback for the 0.15m.
61. The conclusion to the above research and analysis, considering complaints at
0.15m, pontoon dynamic results for horizontal acceleration limits at 0.1m and
body topple acceleration comfort limit at 0.15m, is that regular vessel wake limits
of less than 0.15m must be achieved and that 0.1m is a satisfactory outcome
objective.
62. Similarly the wind wave maximum of 0.3m must also be achieved for a
satisfactory outcome.
C(iii) Review of Ferry Wake Results
General:
63. I note that the MetOcean report measurements are for current ferry vessels.
Although this provides a good data source for appropriate wave protection
strategies review, the question is raised as to flexibility to accommodate future
vessel characteristics.
64. Studies (and problems) throughout the world have clearly identified that
catamaran ferries cause the most trouble. The critical wakes recorded in this
case are from catamaran ferries so any future change to more mono-hulls would
not increase wave protection requirements.
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Wake Results: 65. The largest catamaran ferry, as expected, created the largest measured waves.
As outlined in the MetOcean report, the largest wake heights were 307mm to
344mm. The corresponding wake period of the highest events is typically in the
range of 4.5 to 9.0 seconds.
66. Catamaran ferry wake results, for a situation where they are slowing to arrive at a
terminal, are dominated by their transverse waves which are orientated more
perpendicular to the direction of travel (refer Figure 2.1 of the MetOcean report
and photos 1 to 6 in Attachment 3 from the Ade Consultants letter of 10 June
2011 for the 2011 proposal).
67. Mono-hull vessels will display the same broad characteristics, but the persistence
of the transverse wave (in the direction of ferry travel) by catamarans is more
pronounced.
68. Although the results do not provide wave direction data, experience suggests
that the wake wave direction will be roughly in the direction of ferry travel to the
Matiatia Ferry Terminal (refer Attachment 3, Photo 6).
69. The statement in the 2011 proposal Christian4 report that the wake waves
are more likely to be beam-on to marina vessels is not therefore valid.
However, the comment that the long wave length of these waves will pass
through the floating attenuator almost un-attenuated is valid.
Wind Generated Waves:
70. As discussed in the Cardno report, the storm wind generated waves are of much
lesser wave length but have a greater height. During the two week wave data
collection period, significant westerly sector wind wave events were recorded
which suggests the ambient wave conditions are relatively mild but extreme
event wave height protection is required.
71. As tabulated in Section B(ii), the One Year ARI storm wave height is 0.56 metres
and 50 year is 0.76 metres.
72. Wind wave energy combined with regular wake waves on marina comfort,
safety and marina structure longevity and maintenance is far more concerning
4 C D Christian 2011 Proposal Report
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when the embayment exposure direction is also from this direction, which is the
case at Matiatia.
C(iv) Marina Wave Protection
73. As outlined in the Cardno wave study report, the marina primarily requires
protection from West through to South-West waves. Particular attention needs to
be given to marina protection considering that the predominant strong winds
come from this direction as does the potentially troublesome regular ferry wake
waves.
74. There are three basic options for providing such protection, namely rock
breakwaters, panel breakwaters or floating attenuator structures.
75. From previous analysis and observations in Auckland, 30 plus knots from the W-
SW is not uncommon (436 observations from 1970 to 2008). The 1970 to 2008
records analysis determined that a 1-year return period Westerly 10 minute wind
speed was 17.94 m/s (34.9 knots).
76. The use of a wave attenuator design, which allows a significant amount of
energy through, should therefore be approached with caution, considering
comfort, potential marina structures maintenance and longevity.
77. The fact that ferry wakes have been measured regularly over 0.3m within a two
week period (MetOcean’s measurements) is also cause for concern when these
waves will not be significantly reduced by a wave attenuator design and
research suggests that they should be kept to well under half this value.
78. In my opinion the required wave height objective of 0.1m within the marina for
regular ferry wake waves and absolute maximum of 0.15m cannot be achieved
for longer period transverse waves using floating wave attenuator structures
along the South-west perimeter.
79. MetOcean highest wake heights measurements depict wake periods typically in
the range of 4.5 to 9 seconds. Largest wake heights were 307mm to 344mm.
80. For an 0.3m transverse wake with a 4.5 second period the required width of a
double skirted floating attenuator structure would need to be in the order of 9m
to achieve a 0.1m wave height on the lee side of the structure. For wave period
of 7 seconds (the approximate mean of the abovementioned range) the
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attenuator width would need to be over twice this width. This is clearly
impractical and this is the reason attenuators are not considered a viable
solution with wave periods significantly above 4 seconds.
81. A panel breakwater or rock breakwater therefore needs to be considered.
Either of these solutions, if acceptable from a planning, aesthetic and
environmental perspective, are satisfactory in terms of being able to achieve the
necessary marina wind/wave climate.
C(v) Breakwater Protection Solutions
82. As discussed above and within the Cardno report, the main exposure for wind
and wake waves is from the South-west. Satisfactory wave protection requires
either fixed panel or rock breakwaters for this direction.
Fixed Panel Option:
83. We have determined a (vertical) fixed panel option would need to go from the
sea bed to around 4 metres above mean high water to ensure there was
significant wave energy cut-off, no significant wave crest overtopping in severe
storms with high surge levels and allowance for potential sea level rise.
84. This would obviously be a substantial visual issue. It is also a comparatively high
cost structure with potentially high longer-term maintenance and replacement
costs.
85. This long vertical panel structure would also create a high degree of reflected
wave energy back into the bay with a potentially very confused sea state in
front of the marina.
Rock Breakwater Option:
86. With less wave build-up against a rock slope, the rock breakwater provides a
lower structure top height solution. I have estimated that it can be as much as 1
meter lower than the panel option.
87. It is also more conducive to providing public/recreational access with rock slope
to the water rather than a vertical wall. A footpath with berms each side can be
provided (as proposed) rather than a safety barriered platform on top of the
vertical wall for the panel option. It should also be noted that if someone were
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to fall into the water, they cannot be readily retrieved with a vertical wall
scenario.
88. In light of the above, and the understandable longevity and low maintenance of
rock structures, the rock breakwater option has been adopted and modelled by
Cardno. A satisfactory wave climate to all parts of the marina is achieved with
the double breakwater option as depicted in Figure 3.
Floating Attenuators:
89. As discussed previously, a floating wave attenuator is not a satisfactory solution
for the long period transverse ferry wake waves which will regularly approach the
site from the South-west. However, as with the 2011 proposal, a floating
attenuator structure is appropriate for providing wave energy protection from
the South.
90. This southern fetch across the bay to the site is approximately 300 metres.
Potential wind generated waves from this direction would be in the order of 0.3m
with an associated wave period less than 1.5 seconds.
91. The proposed 4 metre wide Southern Access Pier floating attenuator structure
(refer Figures 3 and 5) has a transmission coefficient of approximately 0.1 for such
short period waves and therefore easily achieves the marina wave climate
criteria.
92. The diverging bow wake waves from ferries approaching the wharf (at slow sub-
critical speeds as they are preparing to berth) will be low height (less than 0.2m)
with a typical angle of approach of around 35 degrees. The transmission
coefficient for such waves would be in the order of 0.4 resulting in a wave height
of less then 0.1m on the marina berths side of the floating attenuator.
C(vi) Marina Entrance
The 2011 proposal configured the marina entrance at the Southwest corner.
93. Concerns were raised with respect to ferry activity conflicts. The entry has now
been configured to the North-west to minimise such conflict.
94. To avoid entrance channel capital and maintenance dredging and provide a
satisfactory navigable entrance width, the primary breakwater finishes
approximately 75 metres from the shore. However, to achieve the satisfactory
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marina wave climate criteria, a secondary breakwater, as depicted on Figure 3
is required.
C(vii) Marina Berths
95. As depicted on Figure 4, the marina berths are orientated in a south-west
orientation in keeping with the bay’s exposure and predominant strong wind
direction.
96. Berths are configured with fairways based on 1.75 times the berth length as
recommended by the Marina Code and in keeping with a good international
standard facility.
97. Pier (A, B, C and D) walkways are configured at a width of 2 metres and the
Southern Access Pier at 4 metres width. This South Access Pier walkway has a
double skirt underwater configuration (refer Figure 5) to provide attenuation of
wave energy that diffracts around the southern end of the primary breakwater
and locally generated wind waves and boat wakes approaching from the south
across the bay.
98. Marina berths services will comprise power and low-level lighting via services
pedestals. Firefighting services will also be included. A sewage pump out facility
will be available on the floating pontoon to the south of the marina. Power
outlets are proposed to be metered to deter over-use.
99. It is proposed that the floating marina system would be a high mass, low
maintenance, concrete deck system in keeping with the philosophy of
constructing a high international standard facility.
100. The mix of berth sizes has been proposed in keeping with current marina market
demand and trends and expressions of interest received during feedback for the
proposal.
101. The proposed size mix is depicted on Figure 3 with 160 berths ranging from
10.5 metres to 20 metres with the ability to accommodate vessels above 20
metres, if required, on the ends of Piers B and C.
102. A floating marina office is located at the start of the marina walkway. This office
has been configured on the basis of keeping it to an efficient minimum area
requirement.
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C(viii) Public Facilities
103. As depicted on Figure 4, public access continuity is provided around the
proposed reclamation (and around the deck option) which includes a
boardwalk from the north to the footpath around the parking area and the
viewing platform.
104. Public access is provided along the primary breakwater which includes a
footpath and viewing platform at its southern end. The Southern Access Pier is
also available to the public, which includes a viewing platform at its western end
and gangway access to the breakwater.
105. Dinghy racks are included near the start of the Pier adjacent to the marina office
with a berth for the Coast Guard on the pier’s southern side. The new floating
dinghy racks will be similar to those in place at south-west end of Westhaven
Marina (Pier X). A total of 17 rack spaces are proposed for the pile moorings.
106. Seventeen pile moorings have been included within the proposal as part of
implementing suitable swing mooring relocation arrangements. The proposed
vessel size mix for these are 2x8m, 6x10.5m, 7x12m, 1x14m and 1x15m with water
depths between 1m and 2m below lowest tide (refer Figure 3). They are within
the protected waters of the marina and conveniently located for access from
the marina or from the adjacent beach area.
107. The existing four mooring holder and two disabled parking spaces have been
retained in the area adjacent to the existing boat ramp.
C(ix) Reclamation
108. As discussed previously, a small reclamation is proposed adjacent to the marina
berths.
109. Locating the marina management office on a floating structure within the
marina is consistent with the philosophy of keeping the reclamation to an
unobtrusive minimum.
110. The proposed reclamation area seaward of Mean High Water Springs is
approximately 0.3 hectares.
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111. As discussed in Section C(vi), public access is maintained around this area via a
footpath around its seaward perimeter and access promoted by inclusion of a
boardwalk connection to the north and incorporation of a viewing platform
within the north-west corner.
112. The area so created is sized to provide 55 car parking spaces including short-
term and long-term zones.
113. The reclamation finished level is +4.5m above chart datum. With an allowance
of 0.4m for sea level rise and 0.5m for storm effects (refer Christian report), the
extreme water level for MHWS + 0.4 + 0.5m = 3.7m is still well below the +4.5m
proposed pavement level.
C(x) Dredging
114. The marina has been sized, located and configured to reasonably minimise the
amount of dredging without pushing the marina too far off-shore. Whilst locating
the marina and its entry sufficiently north to avoid potential conflict with ferry
activities, the northern extent has been limited to provide all-tide navigable
access to Piers B, C and D without the need to dredge the bay on the northern
side.
115. The smallest berths with least navigation depth requirements have been located
within the near-shore pier (Pier A) to also minimise dredging requirements.
116. In accordance with the above, the proposed marina dredging volume is 5,023
cubic metres with a dredge seaward slope profile from -2m to -2.5m to minimise
siltation.
117. Water depth requirements as outlined in the marina code (AS3962) are as
follows:
Vessel Size Draft Keel Clearance Design Depth
10.5m 1.8m 0.3m 2.1m 12m 2.0m 0.3m 2.3m
13.5m 2.2m 0.3m 2.5m 14m 2.3m 0.3m 2.6m 15m 2.5m 0.3m 2.8m 16m 2.6m 0.3m 2.9m 20m 2.9m 0.3m 3.2m
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118. As depicted on Figure 6 the only dredging required to achieve satisfactory all-
tide navigation depths is within Pier A and the associated adjacent navigation
channel.
119. Any smaller sized vessels that could be accommodated within Pier A that have
abnormally deep drafts requiring deeper water would be allocated to a larger
berth further seaward, thus keeping the proposed dredge depths to a minimum.
120. As depicted in Figure 3 the remainder of the marina has existing depths typically
between 3m to 4m below chart datum, which is more than sufficient for their
vessel/berth size category.
121. As detailed in the 2011 Raudkivi report, expected siltation inputs are so low that
their overall effect is less than the predicted sea level rise. With such low siltation
potential the effect of the breakwaters on such insignificant siltation is
correspondingly also not going to have any significant effects.
C (xi) Suspended Car Park Deck Option
122. WML has been given advice that there may be a planning requirement to avoid
reclamation. IMC has therefore been instructed to review this.
123. Figure 9 depicts a suspended car park deck option which is based on the same
car park layout as for the reclamation proposal. The suspended deck is
designed as a precast reinforced concrete deck to minimise over water site
works and is supported by driven reinforced concrete piles.
124. The viewing platform is proposed as a pile supported timber deck structure.
D. Alternative Locations Review 125. Having been advised of submissions suggesting a number of alternative marina
locations, a review of these sites has been carried out. The alternative sites
review included an inspection of each site by boat in March 2014.
126. These alternative sites are (refer Figure 7):
• Owhanake • Church Bay • Rocky Bay • Huruhi Bay • Putiki Bay • Kennedy Point
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D(i) Owhanake
127. This site has significant exposure to wave energy (including ocean swells) from
the North-West.
128. As such, extensive breakwaters would be required across the bay, which would
significantly close off the upper portion of the bay.
D(ii) Church Bay
129. Notwithstanding there is no public road access, this site has a very wide window
of wave energy exposure from the South through to the North-East. As such,
extensive breakwater protection would be required.
D(ii) Rocky Bay
130. Rocky Bay is exposed to the South-West (predominant) strong wind direction. It
also has extensive shallows and numerous navigational obstructions when
entering the bay.
131. Extensive breakwaters would be required and the practicality of constructing
these on the expected soft mud sea bed is questionable.
D(iv) Huruhi
132. Again, this location has exposure to the South-West requiring significant
breakwater protection and questionable breakwater construction practicality
due to expected soft seabed materials.
D(v) Putiki Bay
133. This bay has extensive shallows requiring extensive dredging to achieve
satisfactory all-tide water depths. It is also expected that the dredging
requirement would create an on-going maintenance dredging issue.
134. As with the other South-West facing locations, extensive breakwaters would be
required and soft sea-bed materials would make breakwater construction
practicality questionable.
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D(vi) Kennedy Point 135. This site is less exposed to the South-Westerlies but still would require rock
breakwater protection works.
D(vii) Alternative Sites Conclusion
136. On review of the sites, Kennedy Point was the only one considered worthy of a
further review. Figure 8 depicts an indicative concept of similar size to that
proposed for Matiatia.
137. Although not as directly exposed to the South-West as most other sites reviewed,
there are significant breakwater construction requirements and associated
reclamation to address access and parking demand issues. It is also expected
that soft seabed materials are likely to hinder breakwater construction
practicalities.
138. All of the above suggests that Matiatia is a more favourable solution.
John Leman Date: 30 April 2014
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