C:\WPBD\WPBD DWGS\YARINGA\YARINGA PROP.DRAINAGE

Yaringa Boat Harbour Development
Lumeah Rd Tyabb
Sholto Consulting
sholcons@bigpond.com
Yaringa Boat Harbour
Complex Expansion and
Infrastructure Upgrade
Groundwater, Earthworks
and Drainage
Version 3-2
Geology, Topography, Drainage
23/11/12 Page 1
Yaringa Boat Harbour Development
Lumeah Rd Tyabb
Yaringa Boat Harbour Upgrade
Groundwater, Earthworks and Drainage
Sholto Consulting
sholcons@bigpond.com
1 Introduction
This report seeks to demonstrate that the development an inland
marina facility accommodating 180 wet berths, connected by an
accessible lock to Western Port Bay , the construction of four blocks
of multi-level residential apartments and the construction of a multi –
level, undercover (dry) boat storage facility and six marine trades
workshops, can be achieved within the Yaringa Boat Harbour precinct
without causing environmental detriment.
Note: This version of the drainage report ( Version 3 ) addresses
the requirements identified through the preparation of the
Coastal and Acid Sulphate Soils ( ASS) Management Plan report by
Environmental and Earth Sciences ( Report No 212041) and the
EPBC Act referral process.
Specifically, the following key aspects of the construction method
proposed include;
A Sheet-piling whole inner basin and lock channel through to
underlying clay base.
B Excavation of the basin in the dry.
C Over-excavation in part to provide a "bund" for disposal of acid
sulfate soils (if any are detected) from the lock channel excavation
as recommended in the ASS Management Plan.
D Removal of coffer dam at low tide and allowing tide to fill inner
basin, then closure of lock gates for up 2 days to allow any
sediment to settle before resuming normal operations, which will
be free-flow of lock (i.e. gates open) for 5 hours each high tide
sequence. This will result in water levels rising and falling about 1
metre in the inland basin.
E Removal of all surplus spoil from site as it is excavated.
2 Objectives
a. Outline of the local topography the proposed measures to manage
stormwater drainage for the site.
b. Ground water status and likely impact of harbour development on
Soil Salinity
c. Discussion of the potential impacts on the environment associated
with the proposed development and how these can be minimised.
d. Identify any compliance issues.
e. Outline any measures to be incorporated in the design and
construction phases to minimise any impacts including ensuring
that all subcontractors engaged in works on the site are aware of
any environmental performance requirements and procedures.
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Yaringa Boat Harbour Development
Lumeah Rd Tyabb
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3 Site Description
a. Site Locality - The site encompasses an area of some 14.5 ha of
private freehold land, all of which has either been farmed for cattle
grazing or is currently used for boat storage and marine services
delivery associated with the existing marina complex.
The existing marina complex comprises and area of approximately
7ha of leased crown foreshore reserve.
The site is generally located at the eastern end of Lumeah Rd
adjacent to the Western Port Bay foreshore reserve.
b. Surrounding Land Use
The surrounding land uses include;
i. North – Farmland – Grazing
ii. East – Crown Reserve – Foreshore
iii. South – Rural Residential
iv. West – Rural Residential and caravan park.
4 Topography and Drainage
a. North of Lumeah Rd
The site is generally at the level of 5m AHD and slopes very
gradually to the east, south –east, towards Western Port Bay.
Immediately to the east and north of the Lumeah Rd road reserve,
is an area of coastal wetland that discharges into the mangrove
zone.
Drainage of the site area to the north of Lumeah Rd is to be
directed into the inland marina harbour which itself will be
connected via the access channel and lock system to the existing
main marina channel leading into Western Port. It should be noted
that during the excavation of the inland harbour area, which is to
be undertaken in “dry” conditions, overland flow arriving at the
site boundary will be intercepted and during construction, it will
be diverted south along the western site boundary to Lumeah Rd
and discharged into existing open drainage which then flows
across Lumeah Rd and into Westernport.
On completion of the harbour construction, existing overland
surface water flows arriving from the north (Lot 4 PS 336335) at
the site boundary will be accepted into a grassed open swale
drains and directed to the east towards the foreshore reserve .
In the case of water arriving at the site western boundary ( Lot 4
PS 336335), the swale will run generally from the north to the
south to intersect an easement along the southern boundary of lot
4 . At this point it will be taken across the resort service road via a
300mm dia RCP culvert which will direct water into a Primary
Treatment type, Gross Pollutant Trap to remove sediment and
then discharged into the harbour.
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Geology, Topography, Drainage
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Yaringa Boat Harbour Development
Lumeah Rd Tyabb
Sholto Consulting
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The following product, a Humeguard GPT, is an example of the
Interception trap proposed for use on the drains that service rural
or grassed areas which do not have any hydrocarbon load but may
have nutrient load bound to sediment and which emanate from or
discharge onto the site.
This will ensure that there is no ponding of water on the farmland
adjacent to the site.
Paved and Roofed areas, these will be collected and discharged
directly into the harbour basin.
The general configuration of drainage lines is as shown on the
attached layout plans.
b. Marina Public Access areas and Carparks
These areas north of Lumeah Rd and its Easterly extension, will be
collected and discharged directly into the harbour or the Main
Marina access channel. There is little, if any, expansion of these
areas so no change in runoff from the current situation is expected.
The pipe system servicing this area will be nominally 300mm dia
to facilitate periodic cleaning. It is proposed that drainage from
this section of the site will be intercepted and treated for sediment
removal using a Humeguard GPT as described above, or similar,
before discharge into the main harbour access channel.
c. South of Lumeah Rd
The site has a ridge line along its western perimeter which rises
from the Lumeah Rd boundary level of 6m AHD up to 8.6m AHD in
the south west corner but otherwise slopes from the base of this
ridge from the west to the east very gradually from about 5.9m
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Yaringa Boat Harbour Development
Lumeah Rd Tyabb
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AHD to 4.9m AHD along the Foreshore Reserve boundary.
There is no surface water entering the site from the west because
of the presence of the ridge line.
Land to the south of the site falls north-east toward an existing
grassed swale drain outside the site boundary which itself falls
towards the foreshore reserve. This drain also picks up water from
the existing site perimeter batter which is grassed and treed.
d. Open area for Trailer and Boat Storage.
This area is south of Lumeah Rd and includes the Marine Trades
area. This is an undeveloped, clear area with a grid of gravel lanes
accessing existing grassed boat storage bays.
The subject area is approximately 2ha and surface water is
currently controlled by a grid of open table drains . Other than the
dry boat storage shed, no major civil works are proposed for this
area and any water falling directly onto this section of the site will
be controlled by the re-establishment and improvement of the
existing grid of open grass swale drains servicing the open boat
storage area and gravelled service lanes. This system of open
drains grades to the north and east and leads to a primary
collection point, shown on sheet 2 ( Grid F4) which will be
connected to a Hume Guard, or similar, Gross Pollutant Trap south
of the extension of the Lumeah Rd reserve and then taken by a
pipe to be discharged into the main existing marina access
channel.
e. Marine Trades – Paved and Roofed Area
Water falling onto the roofs and paved Marine Trades workshop
complex area, where there is the possibility of it being
contaminated by trades activities, will be directed through an
Interceptor Trap with capacity to remove hydrocarbons. This pit is
to be located in the position of the current pit in the centre of the
marine trades area ( Grid B3) before being discharged via a
300mm dia pipe to the GPT / Junction pit at the primary collection
point ( Grid F5).
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Yaringa Boat Harbour Development
Lumeah Rd Tyabb
Sholto Consulting
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The following product, a HumeCeptor, Hydrodynamic Separator,
is an example of the system recommended for use.
f. Dry Boat Stacker
Water falling onto the roof of the Dry Boat Stacker will be piped via
two 50,000 litre Rainwater tanks adjacent to the eastern end of the
Stacker building ( approx. F4), then discharging into the
GPT/Junction Pit at F4.
The rainwater tank is being provided to hold water for nonpotable reuse purposes (i.e. Toilet flushing – with discharge to
sewer) within the marina and marine trades areas, landscape
watering and dust control, and can also provide supplementary
water for fire fighting.
Overflow water from this sub-catchment and roof area can
discharge into the open swale then the existing tidal/drainage
channel and into the bay.
g. Primary design flow pipe outlet – South of Lumeah Rd
Normal design flows from the GPT/Junction Pit (F4) will be taken
via pipe to the southern edge of the boat launching ramp ( J5) and
discharged into the marina main access channel. This pipe
intersects an existing pipe at Grid H4.5, which itself is fed from an
upstream open table drain and grass swale system that controls
drainage from Lumeah Rd., the public marina entry and exit
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Yaringa Boat Harbour Development
Lumeah Rd Tyabb
Sholto Consulting
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driveways and the landscaped areas west of the proposed harbour
entry (lock) channel.
5 Regional Geology and Hydrogeology
a. Geology
Based on the Western Port 1:63,360 geological mapsheet
(Geological Survey of Victoria), the following summarises the
geology beneath the site, from youngest ( shallow) to oldest
(deep).
i. Quaternary fluvial clays, silts and sands.
ii. Early Tertiary (Brighton) Sands, marine and terrestrial
sediments, sands, sandy clay and clay.
iii. Mid Tertiary (Fyansford Formation), sands, calcareous
clayey silt, marl, Shelly Sand and some gravels.
iv. Silurian mudstone, sandstone, siltstone and shale.
b. Groundwater and Salinity
The Environmental earth Sciences Report No 212041 provides the
detail information regarding the groundwater condition and level
in the locality and indicates that at present the standing water
level when last measured in 2008 was approximately 4mBGL ,
although this has been known to range from 1.8 to 4.8mBGL over
previous decades. Based on this advice it may be assumed that the
Groundwater table will be at or above Mean Sea level and thus
exhibit a variable but normally positive hydraulic gradient
towards the bay.
The saltmarsh complex is contained within the adjacent foreshore
reserve and is bounded on the seaward side by the intertidal
mangrove complex. The salt marsh area is generally 800mm to
1.5m lower than the existing natural surface levels within the site
and between 100mm and 500mm above High Water Mark (HWM).
The average surface level across the development site is 5 to 5.5m
with the High Water Mark at 3m.
Topsoil within the development site is fertile with a healthy grass
and vegetation cover, it does not demonstrate any significant
saline degradation features.
The proposed marina harbour complex is proposed to be
excavated “dry” with the basin area permanently fully sheet piled
to the underlying clay base level.
This means that the site ground water conditions surrounding the
basin development will be protected from any significant hydraulic
forces that would lead to groundwater leaching into the basin and
bay.
Because there is an existing positive groundwater gradient to the
bay and having regard to the full containment by piling of the
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Geology, Topography, Drainage
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Yaringa Boat Harbour Development
Lumeah Rd Tyabb
Sholto Consulting
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basin, there will be no potential for saltwater capillary action to
cause salination of the upper topsoil horizon.
c. Compliance
The marina facility owner will ensure compliance with
environmental control practices through the inclusion of
appropriate clauses in lease agreements and development
approval permit conditions.
d. Construction Site Induction Requirements
All contractors and sub-contractors engaged to work on the site
shall be formally inducted prior to working on the site in the
following areas;
Occupational Health and Safety Provisions
Environmental Management Plan Provisions focussing on any
spoil transmission and material stockpiling controls and no –go
zones, workers vehicle parking and access limitations, site security
controls.
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Geology, Topography, Drainage
23/11/12 Page 8
Yaringa Boat Harbour Development
Lumeah Rd Tyabb
Version 3-2
Sholto Consulting
sholcons@bigpond.com
Geology, Topography, Drainage
23/11/12 Page 9
Yaringa Boat Harbour Development
Lumeah Rd Tyabb
Sholto Consulting
sholcons@bigpond.com
Attachments – Site Plans A3 with reference Grid markup.
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