Infrastructure Assessment Report Summerset Waikanae
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Infrastructure Assessment Report
Summerset Waikanae
32 Park Avenue, Waikanae, Wellington
Summerset Villages (Waikanae) Limited
22/03/2021
For Resource Consent
Document Control
Project Number P18-320
Project Name Summerset Waikanae
Client Summerset Villages (Waikanae) Limited
Date 22/03/2021
Version V2
Issue Status For Resource Consent
Originator Wanderson Volpato – Engineer
Reviewer Manu Miskell – Senior Engineer
Approval Mark Cochran – Director
Consultant details Woods (Woods and Partners Ltd)
Level 2, Unit 4A, 48 Fitzgerald Ave, Christchurch 3011
PO Box 39102 Harewood, Christchurch 8545
E: info@woods.co.nz
P: 03-378-1773
woods.co.nz
Copyright and The concepts and information contained in this document are the property of
Limitations Woods (Wood & Partners Consultants Ltd). Use or copying of this document
in whole or in part without the written permission of Woods will constitute an
infringement of copyright.
This report has been prepared on behalf of and for the exclusive use of Woods
client and is subject to and issued relating to the provisions of the agreement
between Woods and its Client. Woods accepts no liability or responsibility
whatsoever for or in respect of any use of or reliance upon this document by
any third party.
www.woods.co.nz P18-320: 22/03/2021 : Page 2 of 20
Contents 1. Introduction 4 1.1. Proposal 4 1.2. Site Description 4 1.3. Site Geology 5 2. Earthworks 5 2.1. Proposed Earthworks Description 5 3. Infrastructure Assessment 6 3.1. Kāpiti Coast District Council District Plan 6 3.2. Roading 7 3.2.1. Roading Overview 7 3.2.2. Road Network 7 3.2.3. Geometric Design Parameters 8 3.2.4. Ferndale Drive Extension 8 3.3. Retaining Walls 9 3.4. Stormwater 9 3.5. Wastewater 10 3.5.1. Wastewater Network Overview 10 3.5.2. Proposed wastewater design 10 3.5.3. Ferndale Drive Future Residential 11 3.6. Water Supply 12 3.6.1. Water Supply Overview 12 3.6.2. Water Supply Domestic Demand 13 3.6.3. Fire Hydrant Supply 15 3.6.4. Effects on KCDC Water Supply Network 15 3.6.5. Analysis of Pressure in Peak Demand 15 3.6.6. Proposed Reticulation Layout 16 3.6.7. Assessment as required by Kāpiti Coast PDP Table 11B.3 16 3.7. Electrical and Communications 17 List of Appendices Appendix A Summerset Waikanae Village Master Plan Appendix B Woods Civil Engineering Drawings for Resource Consent – Refer to Separate Document Appendix C Stantec Water Modelling Reports www.woods.co.nz P18-320: 22/03/2021 : Page 3 of 20
1. Introduction Wood & Partners Consultants Ltd (Woods) have been engaged by Summerset Villages (Waikanae) Limited to provide an assessment of infrastructure requirements to service the proposed retirement village at 32 Park Avenue, Waikanae (Site). Woods has carried out an initial design to service the proposed Summerset Comprehensive Care Retirement Village (Village) that is reflected on the Drawings for Resource Consent provided in Appendix 1. The drawings are provided to illustrate the proposed concept to service the Village and to demonstrate that it can be adequately serviced to the requirements of Kāpiti Coast District Council (KCDC). Detailed engineering design will be provided to KCDC for approval with building consent applications following the resource consent process. As the civil infrastructure will remain a Summerset owned private asset, the design has been undertaken with consideration given to local standards (such as the Kāpiti Subdivision and Development Principles and Requirements) where possible. Where local standards cannot be met due to constraints of the Site or they are not directly applicable, the New Zealand Building Code has been used as minimum standard for design. 1.1. Proposal An 8ha portion of the Site is to be used for a retirement village comprising a mix of single and two storey villas and cottages and a central main building. The proposed Main Building would comprise of recreation, social, community, service and administration areas as well as housing assisted living suites, memory care suites and care beds. Maximum occupancy for the Village is estimated to be 401 residents, based on data obtained from Summerset. The population of residents has been estimated as 282 independent residents and 119 serviced, care and memory care residents. Figure 1 Proposed Summerset Waikanae Retirement Village 1.2. Site Description Summerset Waikanae is a proposed retirement village in Kāpiti occupying approximately 8ha of a 25.5 ha Site located at 32 Park Avenue, Waikanae about 2km northwest of Waikanae town centre. The Site consists of the following parcels SO 505441 Sections 17, 18, 19 & 20 and Lot 2 DP 27407 (28 Park Avenue). Lot 2 DP 27407 was purchased with the specific intention of using this as the main access point to the Village. The www.woods.co.nz P18-320: 22/03/2021 : Page 4 of 20
Site is bounded by the State Highway 1 (SH-1) to the north, the Waimeha Stream to the west, residential land to the south, and farmland to the east. The Site is largely undeveloped, apart from one residential dwelling and several outbuildings. The Site is presently vegetated with grass, blackberry, gorse, stands of native shrubs and trees and mature pine trees. The topography at the Site comprises rolling hills at elevations between 6.5m RL to approximately 35.0m RL, with low-lying relatively flat areas located in the west and southeast areas of the site. The Village covers only part of the Site and the balance land could potentially be used to accommodate future residential lots, however the potential future residential subdivision is not part of the Village resource consent application. For the purposes of ensuring common infrastructure is ‘future proofed’ it has been assumed that future residential development may consist of up to 5 lots off a right of way on Park Ave and up to 18 lots off the end of Ferndale Ave. In order to form the Village platforms, earthworks in areas outside of the platforms are required. These earthworks have been designed to ensure any potential future residential development on the balance land is efficient (by minimising rework) and minimises disruption to the Village. Therefore, approval to undertake bulk earthworks on the balance land, establishing lot platforms, and roads to subgrade level is sought under this application. Figure 2 Site Location Plan 1.3. Site Geology The published geological map indicates that the Site is underlain by Aeolian dune sand (Begg and Johnston, 2000). There are also areas of peat within low-lying interdune areas and beach/marine sands and gravels underlay the dunes. For further information refer to the BECA Geotechnical Investigation Reports. 2. Earthworks 2.1. Proposed Earthworks Description Summerset intends to use part of the Site as a retirement village over a bulk earth worked platform of approximately 8ha, which will comprise cuts up to 18m and fills up to 10m in height. The total earthworks volume will be approximately 300,000m3, which it is intended to balance onsite. BECA has been engaged to carry out geotechnical investigations for the Site and have concluded that the onsite soils, excluding any unsuitable materials are expected to be suitable for use as fill material. www.woods.co.nz P18-320: 22/03/2021 : Page 5 of 20
The earthworks methodology and the erosion and sediment control strategies are outlined under a separate
document (Woods (2020), Earthworks and Sediment Control Plan, Summerset Waikanae).
3. Infrastructure Assessment
3.1. Kāpiti Coast District Council District Plan
Chapter 11 of the Kāpiti Coast Proposed District Plan Appeals Version 2018 (PDP) stipulates the Policy,
Standards and Rules for Infrastructure, Services and Associated Resource Use. Table 1 provides an
assessment of the proposal against the relevant rules provided in PDP Table 11B.1 Permitted Activities.
Table 1 Assessment of proposal against PDP Table 11B.1 Permitted Activities
PDP
Proposal
Permitted PDP Standards Comment
Complies
Activities
1. All permitted 1. Development must be undertaken in accordance with Yes Infrastructure
activities in the Council's Subdivision and Development Principles design has been
all zones, and Requirements, 2012. carried out in
including network accordance
utilities. with these
standards
where relevant.
Note freeboard
to building floor
levels have
been set to
Building Code
requirements as
discussed in
section 3.4.
2. Any new and 1. All new or relocated residential No Rainwater tanks
relocated residential buildings where potable public water supply is are not
buildings on land available to a residential building must be fitted with proposed. The
where potable one of the following: water demand
public water a. rainwater storage tanks with a minimum requirements
supply is available. capacity of 10,000 litres for the supply of non- will be met
potable water for outdoor uses and indoor through an
toilets; or alternative
b. rainwater storage tanks with a minimum solution that
capacity of 4,000 litres for the supply of non- will achieve the
potable water for outdoor areas and indoor objective of this
toilets, and a greywater re-use system for rule. Refer to
outdoor irrigation. The greywater re-use Table 2.
system shall re-use all water
from bathrooms (excluding toilets) and
laundry washing machines.
2. – 7. Standards refer to the Greywater and rainwater Not No Rainwater or
system, as we are proposing an alternative system, applicable greywater
these standards are not relevant to the proposal system
proposed
3. Residential Not Not in Rural
buildings in all Applicable Zone
Rural Zones.
As the activity does not comply with Permitted Activity 2 of PDP Table 11B.1. Table 2 provides an assessment
against Table 11B.3 Restricted Discretionary Activity.
www.woods.co.nz P18-320: 22/03/2021 : Page 6 of 20
Table 2 - Assessment of proposal against PDP Table 11B.3 Restricted Discretionary Activity
PDP
Restricted Proposal
PDP Standards Comment
Discretionary Complies
Activities
1. Any new and 1. An assessment that demonstrates the Yes The proposal includes a
relocated residential system proposed will permanently reduce new bore within the
building that does not water demand associated with Site that will provide
comply with any one or the household unit(s) by at least 30% water to all irrigation
more of the permitted from Household 2007 summer average systems and outdoor
activity standards water use. pipes. No outdoor taps
under Rule 11B.1.2. will be connected to the
2. The provision of a non-potable supply for potable public water
all outdoor uses associated with the supply. An assessment
household unit, including garden irrigation. as required by Standard
1. is provided in section
3. Provision must be made to ensure that no 3.6.
outdoor taps can be connected to
the potable public water supply.
2. – 3. Are not Not
applicable as proposal applicable
is not a subdivision. to this
proposal
3.2. Roading
3.2.1. Roading Overview
The Village will be serviced by an internal network of private roads. The main access to the Village will be via
the Village approach road at 28 Park Avenue which will provide a two-way access to the Village from the
public road. A secondary access point will provide exit only for Village residents to Ferndale Drive. An
extension to Ferndale Drive is proposed for this purpose. The extension will be constructed to public road
standards to ensure the road can be vested as a road with future residential subdivision.
3.2.1.1. Basis of Design
The following references and standards have been used in the roading design.
− Summerset Master Plan Client Brief (Rev D, 2018)
− Kāpiti Coast District Council - Subdivision and Development Principles and Requirements, 2012
(SDPR)
− NZS 4404:2010 - Land Development and Subdivision Infrastructure
3.2.2. Road Network
The road layout has been set by Summerset’s Master Plan, provided in Appendix A. The layout has been
reviewed by Stantec transportation engineers who have confirmed the layout allows for appropriate vehicle
tracking.
Roads will vary in width dependant on their hierarchy and vehicle movements. The Village approach road
will have a carriageway width of 7.0m, primary boulevard 6.5m, secondary streets a width of 5.5m and
residential lanes a width of 4.5m, refer to Figure 3 road hierarchy plan.
www.woods.co.nz P18-320: 22/03/2021 : Page 7 of 20
Figure 3 Road Hierarchy Plan (Source Kamo Marsh) 3.2.3. Geometric Design Parameters In order to allow for adequate drainage gradient, a minimum longitudinal gradient of 1 in 250 (0.4%) has been adopted, while a maximum gradient of 1 in 20 (5%) was provided within the Village to meet Summerset accessibility requirements. Cross falls will typically be between 2-3%. Stormwater runoff within the road corridors will be via street sumps which will discharge directly into the stormwater reticulation system. These sumps will be located in the kerb and channels adjacent to the formed carriageway as shown in the Combined Services Layout Plans provided in Appendix B. Road corridors will be used as overland flow paths to direct stormwater runoff should there be a blockage of the sump intakes. The typical road cross-sections for the Village are illustrated in the Civil Engineering Drawings provided in Appendix B. 3.2.4. Ferndale Drive Extension It is proposed to extend Ferndale Drive from the current extents of formation at the Site boundary to the north end of the Village. The road extension will be constructed to public road standards and will terminate in a cul-de-sac head adjacent to the Village. A private exit-only road connection will be constructed from the Village to the cul-de-sac. The Ferndale Drive road extension will initially remain privately owned by Summerset, however the intention is to vest this section of road in council with a future potential residential subdivision that will be subject to a separate resource consent application. The design drawings show an indicative design that is similar to the existing Ferndale Drive formation, however this is subject to detailed design and specifications being prepared. It is intended that the retaining wall design, if required, will be submitted to KCDC for building consent prior to construction of the Ferndale Drive extension. The existing formation of Ferndale Drive has been constructed to approximately 7m from the Site boundary, however the earthworks completed with the road construction were undertaken in a manner that introduces www.woods.co.nz P18-320: 22/03/2021 : Page 8 of 20
a number of design scenarios to be able to form a connection to this road from Summerset’s boundary. In
order to extend the road with footpaths and berms at acceptable crossfalls, retaining a height of up to 3m
will be required within the road reserve or fill will need to extend into the adjacent residential lot. The key
constraint is that the ground on the north side of Ferndale Drive drops away abruptly to a low area within
the adjacent residential property. As mentioned above, Woods have included an indicative design that
confines all works to be on Summerset’s property and road reserve. For the purposes of this resource consent
application, the solution that is proposed is the construction of the retaining wall option. However, a potential
option is to pursue a fill option on the neighbouring property. That alternative approach shall be provided
for in the conditions should it be preferred.
3.3. Retaining Walls
Retaining walls will be required throughout the Site to support the cut faces that are created. A larger
retaining wall located along the northeast end of the Village platform is required to enable flat usable areas
between the main and upper platform.
Several small retaining walls will also be required in the southern part of the Site allowing flat access grades
to be achieved. The placement and height of internal retaining walls will be refined during the detailed
design.
Retaining wall heights throughout the Site will vary, but do not exceed 3.0m in height.
3.4. Stormwater
Primary and secondary stormwater flows will need to be managed, in accordance with the New Zealand
Building Code (NZBC), Kāpiti Coast District Council (through the PDP) and Greater Wellington Regional
Council requirements (through the Proposed Natural Resources Plan (PNRP).
The proposal is to:
− Control the stormwater runoff in frequent storm events by eliminating ponding within the
Village. This will be achieved by a conventional piped stormwater network that will be designed
for a 10-year ARI storm event (including allowance for climate change).
− Mitigate the increased flow rates for the Village for rainfall events exceeding the 2-year ARI up
to and including the 100-year ARI event (including allowance for climate change). This will be
achieved via two attenuation basins with staged restricted outlets.
− Control the stormwater runoff for a 100-year ARI event (including allowance for climate
change) by allowing sensible secondary overland flow paths through the Village to provide
protection against flooding of buildings.
Habitable building floors shall have a freeboard of at least 150mm above the surface water of the secondary
level of protection event in accordance with the NZBC. We note that KCDC Subdivision and Development
Principles and Requirements, 2012, require the underside of floor slabs of habitable buildings be set to
achieve 500mm freeboard above the secondary flow level. This is not achievable within the Village as the
roads, paths and driveways need to be designed to be accessible for residents with a maximum grade of
1V:20H (5%). This means the floor level of the buildings is a maximum 275mm above the level of the kerb
line (5.5m driveway at 1V:20H).
The Village catchment is relatively small and overland flows are typically minor and contained within the
kerbs, there is also limited upstream catchment which means that the flood hazard can be effectively
controlled within the Village. Therefore, the proposed floor levels provide a 150mm freeboard in accordance
with the NZBC. It is considered that the Building Code requirements provide an appropriate level of flood
protection.
The detailed stormwater management approach for the proposed Village is provided in a separate document
(Woods, Stormwater Management Plan, 2020).
www.woods.co.nz P18-320: 22/03/2021 : Page 9 of 20
3.5. Wastewater
3.5.1. Wastewater Network Overview
The proposed wastewater network for the Village consists of a gravity reticulation system, that will discharge
to the existing wastewater network at Park Avenue. The wastewater main along Park Avenue is 300mm
diameter and is 2.72m deep based on Beca topographical survey.
The proposal to discharge the Village wastewater to this location in the public network has been discussed
with John Saxton (KCDC Senior Water and Wastewater Engineer). Mr Saxton has not declared any issues with
this proposal, however he has noted that any significant new wastewater demands (such as the proposed)
need to be included in the KCDC network model to ensure that there is no capacity limitations. This modelling
was requested from KCDC’s consultant in November 2019 and we have not been made aware of any
limitations identified by the modelling at this time, therefore, for the purposes of this application, we have
assumed that the public network has the capacity for the Summerset sewer discharge at Park Avenue.
The following sections summarise the design criteria, bulk wastewater volumes and peak wastewater flow
rates.
3.5.1.1. Basis of design
The following references and standards have been used in the wastewater design.
− Kāpiti Coast District Council - Subdivision and Development Principles and Requirements, 2012
(SDPR)
− NZS 4404:2010 - Land Development and Subdivision Infrastructure
3.5.2. Proposed wastewater design
The network design is based on the following design parameters and requirements.
3.5.2.1. Wastewater Flow Calculations
To determine the specific flow demands for the site, the following design parameters were applied to
the site:
− Each independent unit on the Site will have an occupancy rate of 1.3. This rate was provided
by the client and is based on the average occupancy rate across Summerset’s 26 New Zealand
villages.
− All main building units have an average design occupancy of one person per unit.
Design per capita allowances for the Site are based on the SDPR. These are as follows:
− Average dry weather flow allowance of 250 litres per day per person
− An allowance has been made for potential future residential subdivision on parts of the site,
being 5 lots from Park Avenue and 18 lots from the end of Ferndale Drive.
www.woods.co.nz P18-320: 22/03/2021 : Page 10 of 20Based on the Summerset master plan and the proposed occupancy, the anticipated wastewater flows are
summarised in Table 3.
Table 3 – Wastewater Flow Calculations
Wastewater Flow Calculations
Village - Connection at Park Ave
Total occupancy 401
Daily flow per person 250 l/day/person
Average dry weather flow 1.16 l/s
Dry weather diurnal peaking factor 2.5
Peak dry weather flow 2.9 l/s
Dilution/infiltration factor for wet weather 2
Peak wet weather flow 5.8 l/s
Possible Subdivision - Connection at Park Ave
Number of dwellings 5
Number of people per dwelling 2.5
Average dry weather flow 250 l/p/day
Average dry weather flow 0.04 l/s
Dry weather diurnal peaking factor 2.5
Peak dry weather flow 0.09 l/s
Dilution/infiltration factor for wet weather 2
Peak wet weather flow 0.18 l/s
Possible Subdivision - Connection at Ferndale Drive
Number of dwellings 18
Number of people per dwelling 2.5
Average dry weather flow 250 l/p/day
Average dry weather flow 0.13 l/s
Dry weather diurnal peaking factor 2.5
Peak dry weather flow 0.33 l/s
Dilution/infiltration factor for wet weather 2
Peak wet weather flow 0.65 l/s
3.5.2.2. Reticulation Network
New private gravity reticulation will be designed and constructed in accordance with KCDC SDPR and NZBC
to provide each unit with a connection. The proposed layout of the wastewater reticulation is shown in the
Combined Services Layout Plans at Appendix B. The proposed design indicates that a 150mm diameter pipe
is adequate for the site. The private wastewater mains will generally be located under the Village road
carriageway with 100mm diameter laterals provided to each villa. Due to the distance between the south
corner and the northeast end of the Village, the sewer line to service the northeast end of the Village is
approximately 330m long, at minimum grades this line reaches a maximum depth of 5m at the top of the
approach road.
Full design and detailing of the wastewater system will be provided at building consent stages.
3.5.3. Ferndale Drive Future Residential
An allowance is being made for future residential lots from the extension of Ferndale Drive. The Ferndale
Drive road extension will be constructed as part of the Village to provide exit only access for Village residents,
in addition the design aims to future proof this road extension to cater for future residential subdivision off
this road (estimated at up to 18 residential lots). In terms of wastewater, there is an existing public 150mm
www.woods.co.nz P18-320: 22/03/2021 : Page 11 of 20gravity sewer line that has been constructed to the current extents of the Ferndale Drive road formation.
Unfortunately, the end of this line is shallow (approximately 1.3m deep), and therefore has very limited ability
to service an extension of Ferndale Drive under gravity. Therefore, a pressure sewer system with individual
grinder pumps and tanks for each property is proposed for these future lots.
3.6. Water Supply
3.6.1. Water Supply Overview
The Village will be fully reticulated with a new private network of watermains within the Village. The water
reticulation will consist of a potable / fire hydrant supply and a separate fire main to a sprinkler system in
the main building.
Summerset’s preference is to have a two-end domestic supply to provide resilience, the supply would be fed
from two locations:
− 150mm diameter distribution main running parallel to Park Avenue and is located on the opposite
side of this road.
− 150mm diameter distribution main running parallel to Ferndale Drive and is located on the northern
side of the road.
The fire main to the main building sprinkler system will be a separate 150mm connection from the KCDC
main in Park Avenue. Backflow prevention will be provided to meet KCDC requirements at the Site boundary
for all the connections to public mains.
The proposed location for the backflow prevention device at the Ferndale Drive end of the Site is adjacent
to the gate of the Village Exit Only Road. It is not intended to vest the Ferndale Drive extension as road with
the Village construction, but rather under a separate future subdivision. We note that KCDC requires that
backflow preventers are located within private property adjacent to road reserve, the proposed location will
meet this criteria when the road is vested under a future subdivision.
The proposed location for the backflow preventer will comply with the KCDC requirements for the site upon
completion of future subdivision (as the road will be vested in the Council as a public road). This approach
avoids having to move the backflow preventer to its final place once subdivision occurs. Good access to the
backflow preventer will be provided to KCDC staff as Ferndale Drive extension will be constructed to public
road standards (although it may not be vested immediately).
It is intended that the potable water supply will not be used for irrigation or outside taps and a separate
consent is being sought to construct a bore for the irrigation and outside tap supply.
www.woods.co.nz P18-320: 22/03/2021 : Page 12 of 20Figure 4 Existing water supply network
The following sections summarise the design criteria, peak water demands and a description of the proposed
network design and upgrades.
3.6.1.1. Basis of Design
The following references and standards have been used in the water supply design.
− Kāpiti Coast District Council – Subdivision and Development Principles and Requirements, 2012
(SDPR);
− NZS 4404:2010 – Land Development and Subdivision Infrastructure;
− SNZ PAS 4509:2008 – New Zealand Fire Service Firefighting Water Supplies Code of Practice;
and
− NZ Building Code, Clause G12 “Water Supplies”.
3.6.2. Water Supply Domestic Demand
To determine the specific flow demands for the site, the following occupancy rates were applied:
− each villa or apartment on the Site will have an occupancy rate of 1.3, this rate was provided by
Summerset and is based on the average occupancy rate across Summerset’s 26 New Zealand
villages;
− assisted living suites, memory care suites and care beds have an occupancy rate of 1;
− an allowance is made for 40 staff and 45 visitors using 50 l/p/day; and
− an allowance has been made for potential future residential subdivision on parts of the site, being
5 lots from Park Avenue and 18 lots from the end of Ferndale Drive.
www.woods.co.nz P18-320: 22/03/2021 : Page 13 of 20Table 4 Village domestic water demands
Village Domestic Supply
No of Population Peak Daily demand Total
Unit Type
units per unit Occupancy L/p/day (1) L/day
Independent Living Units 217 1.3 282 350 98,700
Assisted Living Suites 56 1 56 350 19,600
Memory Care Suites 20 1 20 350 7,000
Care Beds 43 1 43 350 15,050
Guests 45 1 45 50 2,250
Staff 40 1 40 50 2,000
Total 144,600
Average Demand (l/s) 1.67
Peak factor (1) 2.2
Peak domestic Village demand (l/s) 3.66
6.0
Peakfactor
(1) Daily demand and peak domestic village demand
as calculated (l/s) based on actual use by households in
by Stantec
6.0 peak as irrigation and outdoor taps to be supplied from
Waikanae catchment, assumes no summer
bore. Peak domestic village demand (l/s)
Table 5 Potential future subdivision water demands
Possible Future Subdivisions Within Wider Property
Possible Subdivision - Connection at Park Ave
Number of dwellings 5
Number of people per dwelling 2.5
Total Population 12.5
Daily demand (from Stantec) (1) (l/p/day) 350
Daily demand (l/day) 4,375
(1)
Peak factor (From Stantec) 2.2
Peak domestic demand - 5 lot subdivision (l/s) 0.11
Possible Subdivision - Connection at Ferndale Drive
Number of dwellings (conservative estimate) 18
Number of people per dwelling 2.5
Total Population 45
Daily demand (from Stantec) (1) (l/p/day) 350
Daily demand (l/day) 15,750
(1)
Peak factor (From Stantec) 2.2
Peak domestic demand - 18 lot subdivision (l/s) 0.40
(1) Daily demand and peak factor as calculated by Stantec based on actual use by households in
Waikanae catchment, assumes no summer peak as irrigation and outdoor taps to be supplied from
rainwater.
www.woods.co.nz P18-320: 22/03/2021 : Page 14 of 20Table 6 Firefighting demand
Firefighting Demand
Main Building Sprinkler Demand (Dedicated fire main)
Estimated from similar Summerset Buildings (l/s) 17
Residual pressure at valve house (RL 16m) (kPa) 350
Village Fire Hydrant Demand
12.5l/s from 2 x hydrants (SNZ PAS 4509 FW2) (l/s) 25
3.6.3. Fire Hydrant Supply
A preliminary fire hydrant demand of 25l/s has been determined in accordance with SNZ PAS 4509:2008 and
based on a fire classification of FW2. The required fire-fighting flow is 12.5l/s from a hydrant within 135m
with another 12.5l/s from a hydrant within 270m, residual pressure greater than 100Pa.
The main building will have a sprinkler system supplied from a separate fire main. The fire main will connect
to the KCDC network at Park Avenue with suitable backflow prevention at property boundary. The sprinkler
system demand is estimated from similar Summerset buildings at 17l/s with 350kPa residual pressure at
valve house.
3.6.4. Effects on KCDC Water Supply Network
KCDC maintain a model of their public supply network and Stantec was engaged to test the Village and
future subdivision demands in the model to identify any constraints and limitations to the supply. The model
was originally run with conservative assumptions for the Village demand, with peak demands for
Independent Living Units (ILU’s) based on NZS4404 and the main building supply using a demand based on
the number of plumbing fixtures in the building. These initial assumptions were deemed to be conservative
and perhaps not fit for purpose for investigations of a network wide scope.
The initial assessment with the conservative Village demand applied found that high head losses in parts of
the existing network resulted in loss of pressure for some downstream customers. The loss of service for
downstream customers was deemed to be outside of acceptable limits.
Stantec reported the following in their assessment:
• The significant drop in pressure observed at the critical point customers is caused by high head
losses in mains in the upstream network in Te Moana Road, between Main Road (old SH1) and
Ngarara Road. This network is responsible for delivery of water from Kakariki Reservoir to Te Moana
Road, Waikanae Beach and Peka Peka, and is already under stress.
• The high level of head loss in Te Moana Road is a known problem, and an upgrade has been
proposed to address the problem ahead of development in the Ngarara area (including Park
Avenue). This upgrade (known as the Ngarara Loop) consists of around 3km of 200mm diameter
mains from Main Road (the old SH1) right through to Field Way in Waikanae Beach.
Stage 1 of the upgrade would resolve the issues identified in the original assessment.
Following the original assessment, Stantec was requested to re-run the analysis with more realistic, less
conservative water demand assumptions for the Village and future subdivision. These values are provided
on Tables 2 – 4. The revised values were based on real water demand data for the local area on a per
population basis, on the assumption that the residents will use the same volume of water per day with a
matching daily use pattern as other residents in the catchment. We believe this is an appropriate assumption
for network wide modelling. The revised analysis showed that pressure losses for downstream customers
was at an acceptable level. Copies of the Stantec Analysis Reports are attached at Appendix C.
3.6.5. Analysis of Pressure in Peak Demand
According to Section 6.3.5.3 of NZS4404:2010, water demands vary on a regional basis depending on a
variety of climatic conditions and consumer use patterns. The Council should be able to provide historically-
www.woods.co.nz P18-320: 22/03/2021 : Page 15 of 20based demand information appropriate for design. Therefore, to assess the demand for the Village we used
KCDC water demand data instead of default figures from NZS4404.
KCDC has comprehensive data for water use in the Waikanae network and this data has been used to model
the pressure and flow demands for the Village.
The Waikanae water supply is divided into several District Metered Areas (DMAs), the Site is to be serviced
from the Te Moana DMA. KCDC has real demand data from the DMA that has been used to produce master
planning models for the network. Summerset engaged Stantec (KCDC’s water modelling consultant) to
assess the water supply system using KCDC’s master planning model KCDC WS MPL05.
Stantec ran several design scenarios using this model and the parameters and results are presented in
Appendix C.
The first model run used water demands using the default figures from NZS4404 for independent living units
and potential future subdivisions and a conservative demand estimate for the main building. The peak water
flow was then applied to the DMA profile and an assumed profile was used for the main building demand.
While the results of the model showed that complying pressure of more than 25m would be met for all
customers, the model predicted a pressure drop for some downstream customers.
With further analysis, it was clear that applying the default demands to the real demand profile was not
appropriate as it grossly overestimated the water demands for the Village when applied on a network wide
basis. For example, this methodology resulted in daily demands of 576l/p/day for ILUs and 634l/p/day for
future subdivision.
The demands for the Village were subsequently refined and real data from the peak day DMA profile was
used to predict the effects on the network. For this model run, Stantec calculated a daily demand of
350l/p/day and a peak factor of 2.2. Noting that no outdoor water uses will be supplied from the potable
supply, we believe these figures are suitably conservative and comply with NZS4404 as it uses historically
based demand information appropriate for design.
3.6.6. Proposed Reticulation Layout
The proposed water reticulation network for the Village is illustrated in the Civil Engineering Drawings
provided in Appendix B.
The Village will be provided with a fully reticulated supply to the main building and independent living units
which will include fire hydrants throughout the Village. A separate dedicated fire main will supply a sprinkler
system in the main building.
The domestic supply consists of two-end connections at Park Avenue and Ferndale Drive to provide resiliency
and security of supply and separate main building fire main connection at Park Avenue. A backflow
prevention device is proposed at the connections at each end of the Village.
The supply main reticulation within the Village consists of a 150mm diameter or 100mm diameter water main
located along primary and secondary roads, with a 63mm rider mains servicing residential lanes. Fire hydrants
will provide fire-fighting requirements of the Village and these will be installed on the 150mm and 100mm
water mains.
All internal watermains for the Village will remain privately owned and operated by Summerset.
3.6.7. Assessment as required by Kāpiti Coast PDP Table 11B.3
The proposal is to supply irrigation and outdoor taps from a private bore supply as an alternative to rainwater
tanks. As this is an alternative system to that described under PDP Table 11B.1, the proposal shall be assessed
as a Restricted Discretionary Activity under PDP Table 11B3. The first standard on this table requires the
following:
1. An assessment that demonstrates the system proposed will permanently reduce
water demand associated with the household unit(s) by at least 30% from Household
2007 summer average water use.
www.woods.co.nz P18-320: 22/03/2021 : Page 16 of 20The Household 2007 summer average water use refers to a study that was conducted by BRANZ in 2007 that
involved monitoring water use in a sample of residential homes on the Kāpiti Coast. Heinrich, Matthias. 2007.
‘Water End Use and Efficiency Project (WEEP) – Final Report’. BRANZ Study Report 159. BRANZ Ltd,
Judgeford, New Zealand. Table 7 summarises the results of this study during the summer period.
Table 7 – Summer Average volumes per end use (reproduced from Table 7 of BRANZ Study Report 159)
Percent of Total Average (l/p/d)
Tap 11.7% 23.9
Shower 22.2% 45.3
Washing Machine 20.4% 41.6
Toilet 17.0% 34.7
Dishwasher 1.3% 2.7
Bathtub 1.5% 3.1
Miscellaneous 0.0% 0.0
Total Indoor 74.22% 151.3
Outdoor 21.8% 44.5
Leaks 3.3% 6.7
Total Use 100.0% 203.9
The assessment provided on Table 8 demonstrates that the system proposed will permanently reduce the
water demand by at least 30% from Household 2007 summer average water use.
Table 8 – Village Water Demands Reductions
Item Reduction Comments
Outdoor 21.8% All outdoor taps and irrigation will be supplied from a bore and will not
be connected to the potable supply.
Leaks 3.3% The potable reticulation will be constructed of modern materials and
to modern construction standards and will be tested to ensure that it
is free of leaks when commissioned. The system will be actively
maintained by Summerset for the life of the asset and any leaks that
occur will be promptly repaired.
Bathtub 1.5% There will be no bathtubs installed in any units.
Shower 4.5% The Village will be fitted with 3 Star Water Efficiency Rated shower
heads with a specified flow of 8.5l/min, this represents a 20% reduction
in shower flow from the shower flows measured in 2007 study, or a
4.5% reduction overall.
Toilet 5.9% The Village will be fitted with 4 Star Water Efficiency Rated toilets with
flush volumes of 4.5/3L per flush. This represents a reduction of 35% of
the average flush volumes measured in 2007 study or 5.9% overall.
Total 37%
Table 8 shows that through supplying outdoor uses from a separate source, the use of modern efficient
fittings and leak free reticulation, the system will exceed the PDP requirement of 30%.
3.7. Electrical and Communications
Summerset has engaged experts to design electrical and communications reticulation for the proposed
Village.
These experts have confirmed that there is enough capacity to service the Village from the existing networks.
www.woods.co.nz P18-320: 22/03/2021 : Page 17 of 20Appendix A Summerset Waikanae Village Master Plan www.woods.co.nz P18-320: 22/03/2021 : Page 18 of 20
Back Flow Preventer
D
ROA
L Y
I T ON Ferndale Dr extension -
EX refer to civils drawings
Proposed village
B32 B31 secondary exit Gate
Village Exit Only Road
Summerset Village
Pedestrian access to B33 NOTE: Over Under Units (B27 - B30) consist of 4
KĀPITI CYCLE ROUTE -
EXPRESSWAY Idependent Living Units (ILU's).
2 ILU's are accessed from the north side on the
lower level platform. The other 2 ILU's on the first
B40 B30 floor level are accessed from the south side up on
ry B39 B34 the upper level platform.
da
o un
lB
ga
Le B41 B35
B29 Raised area of villiage
Blocks B11 to B30 inclusive
B43 B24 accessed from raised area.
B23
Refer to Over Under Unit
B42 note for other access to
blocks B27-B30
B28
B44 B38 B25
B45
77 B22
76
B37 74
75 B27 B16
73
72
70 71
67 68 69
64 65 66
61 62 63 B15
B49 B36 B17
B26
en
ng Gre
i
B48 B owl
B46
B21
Hobbies, Maintenance
and Waste B14
B50
54
53 55
52 56
51 T1 57
58 Gas Store
B20
50 59 B18
or
B53 49 60 B19 B13
at
er
B47
en
48
B52
G
Main Building
B51 47
46
45
44
43
26
B12 TOTAL BUILDING FOOTPRINT
25 16 15
B54 42 24 17 MAIN BUILDING TOTAL m² COTTAGE & VILLA TOTAL m²
29 23 20 19 18
30
22 21 3890 m² C1 = 360 m²
41 31 28
36
32
27 B10 NOTE: Louisvilles consist of 4
35 C2 = 183 m²
B57 B58 34 Idependent Living Units (ILU's).
33
B09 2 ILU's are located on the ground level C3 = 582 m²
B11 while 2 ILU's are located on the first
B56 40
C4 = 364 m²
B55 floor level.
39 37 V1 = 5670 m²
38 GENERAL LEGEND
T1
V2 = 4683 m²
TRANSFORMER 1
V3 = 2454 m²
B66 B08 T2
TRANSFORMER 2 V4 = 4135 m²
B67 LVN = 1260 m2
B07 PS
PUMP STATION
B60 B05 LVS = 903 m 2
B61 MSDB
MAIN DISTRIBUTION BOARD U1-U3 = 1016 m2
GAS STORE = 0 m²
B59 VILLAGE GREEN CORRIDOR RESIDENTS WORKSHOP,
14 13
12 PLANTING MAINTENANCE & WASTE REFUSE
B02 B06 BUILDING 184m²
TRAFFIC CALMING PAVING
T2 2 1
4 3
11 10 6 5
B63 B03 9 8
7 N
MSDB
B62 TOTAL 1.5B 2B 2B 2B 2B 3B 2B 2B 3B 2B 3B TOTAL 1B MC TOTAL CARE
Mid End End End Lwr Upr Upr Lwr Upr ILU's SUITES VILLAGE BEDS
B64 C1 C2 V1 V2 V3 V4 U1 U2 U3 L1 L2 ALS MCS CB
C3 C4
B04 W E
B01
13 6 54 44 22 34 8 0 8 14 14 217 56 20 293 43
B65 % MIX (EXCL. CA'S) 6% 3% 25% 20% 10% 16% 4% 0% 4% 6% 6% S
% COTTAGES 9%
% VILLA MID 25%
1 MASTER PLAN - UNIT TYPE & UNIT MIX % VILLA END 46%
1 : 700 % OTHER ILU's 20%
TOTAL VILLAS & COTTAGES 217 PLATFORM INFORMATION A 27/03/20 Resource Consent Issue
Rev Date Description
Approach Road from TOTAL ASSISTED LIVING SUITES 56 TOTAL SITE AREA 255,022 m 2*
Park Avenue as per Client.
sheet RC.008 TOTAL MEMORY CARE SUITES 20 TOTAL VILLAGE AREA 79876 m²
TOTAL VILLAGE 293 TOTAL BALANCE AREA 175,146 m 2
SITE COVERAGE % (SITE AREA) 10% Summerset Head Office Ph. 04 894 7320 Fax. 04 894 7319
headoffice@summerset.co.nz www.summerset.co.nz
TOTAL CARE FACILITY BEDS 43 SITE COVERAGE % (VILLAGE AREA) 32.3% Project Name.
TOTAL ROAD SURFACE AREA SUMMERSET VILLAGE
15336 m²
AP
WAIKANAE
PR
Lega
PARKING INFORMATION TOTAL DRIVEWAYS 5064 m²
OA
l Bou Project Stage. Block Number.
ndar TOTAL SITE PARKING 77 TOTAL FOOTPATHS 2500 m² RESOURCE CONSENT
C
y
H
Drawing Title.
TOTAL PARKS INCL. VILLAS & ALS/MCS 485 TOTAL SLAB COVERAGE 25795 m²
RO
(excl patio, service, entrance areas) MASTER PLAN - UNIT TYPES & MIX
AD
CYCLE PARKS 12
27/03/2020 2:51:13 p.m.
TOTAL IMPERVIOUS AREA DO NOT SCALE DRAWINGS. DATE
(incl patio, service, entrance areas) 52407 m² Original Sheet Size: A1 27/03/20
Project Number. Drawing Number. Rev
053 RC.011 A.Appendix B Woods Civil Engineering Drawings for Resource
Consent – Refer to Separate Document
www.woods.co.nz P18-320: 22/03/2021 : Page 19 of 20Appendix C Stantec Water Modelling Reports www.woods.co.nz P18-320: 22/03/2021 : Page 20 of 20
Kapiti Coast District Council (KCDC)
Park Avenue Development Report
This report has been prepared for the benefit of Kapiti Coat District Council. No liability is accepted by this
company or any employee or sub-consultant of this company with respect to its use by any other person.
Rev. Checked Reviewed Approved
Date Description Prepared By
No. By By By
0 08/01/2019 Final A Brotherston B Davies B Davies B Davies
1 Introduction
KCDC has engaged Stantec to report on the water supply available at the proposed development of a
Retirement Village at 32 Park Avenue, Waikanae. The development will consist of 217 Independent Living Units
(ILUs) and a central Main Building. This study will also assess the impact of the demand for the proposed 5 lots
near the connection point at Park Avenue, and the proposed 18 lots near the connection at Ferndale Drive.
The location of the main development and the approximate location of the additional developments are shown
in Figure 1-1.
This document describes the requirements for water supply at the development site.
Retirement Village 18 Lots
5 Lots
Figure 1-1: Location of Proposed Development
Stantec
Status – Draft │ 08 January 2020│ Project Number – 310101208 │ Park Avenue Development Report final 08.01.2020.docx
Page 11.1 Network Configuration
The proposed development lies within the Waikanae, Paraparaumu and Raumati (WPR) Network. The WPR
network is mainly fed from the Water Treatment Plant (WTP) on Waikanae River. From there, water is pumped
along separate trunk mains, north to Waikanae and south to Paraparaumu/Raumati (Figure 1-2).
Within the Waikanae network there are several District Metered Areas (DMAs), the Park Road development is
supplied from the Te Moana DMA.
Figure 1-2: WPR Network Schematic
2 Water Supply Requirements
2.1 Design Pressure
Schedule 6 of the Kapiti Coast District Councils Subdivision and Development Principles and Requirements, 2012
(SDPR), states that the design pressure (i.e. during Average Day Peak Week demand) shall be between 250kPa
and 900kPa (25m to 90m head) at the point of supply.
2.2 Available Fire Flow
Table 2 of SNZ PAS 4509:2008 New Zealand Fire Service Firefighting Water Supplies Code of Practice (Fire Code)
states the minimum firefighting water supply required for residential buildings is 12.5L/s flow within a distance of
135m of the building and a further 12.5L/s within 270m, with minimum 10m pressure at each source during 60%
of annual peak demand.
Information provided by the developer states a sprinkler system is in place for the main building, which is
estimated to require 17 l/s at 350 kPa when operating.
Stantec
Status – Draft │ 08 January 2020│ Project Number – 310101208 │ Park Avenue Development Report final 08.01.2020.docx
Page 23 Network Modelling
For reference, the modelling is based on the master planning model KCDC WS MPL05, using the 2018 and 2046
upgraded scenario. A variation named “KCDC WS MPL05 C04 Summerset Development” has been created for
this assessment.
3.1 Proposed Water Supply Network
The development at Park Road consists of a Retirement Village and two areas for residential subdivision
development. The Retirement Village will be made up a central Main Building and 217 Independent Living Units
(ILU), while the residential development will consist of 5 lots at the Park Avenue connection and up to 18 lots at
the Ferndale Drive connection. The Retirement Village will have a dedicated fire main which will supply the
sprinkler system for the Main Building.
It is proposed to create a loop main by connecting the development to the existing 150mm PE main on Ferndale
Drive and linking this to either the existing 150mm AC main on Park Avenue (Scenario 1) or the existing 200mm
AC main on Te Moana Road (Scenario 2).
3.1.1 Scenario 1 – Park Avenue Connection
The development plan (Figure 3-1) was used to add the proposed development pipe network, following the
proposed on-site road layout. The proposed size of the distribution main and the dedicated fire main is 150mm.
Hydrants are proposed at 135m intervals as per requirements of The Fire Code of Practice (described in 2.2).
Ferndale Drive
Connection
Park Avenue
Connection
Figure 3-1: Scenario 1 Development Layout
Stantec
Status – Draft │ 08 January 2020│ Project Number – 310101208 │ Park Avenue Development Report final 08.01.2020.docx
Page 33.1.2 Scenario 2 – Te Moana Road Connection
In the same way as the previous scenario, the pipe network has been added based on the developer plan
which partially follows the route of the proposed on-site road layout.
Te Moana Road
Connection
Ferndale Drive
Connection
Figure 3-2: Scenario 2 Development Layout
3.2 Demands
This development consists of four separate demands; Retirement Village Domestic, Main Building, Park Avenue
subdivision, and Ferndale Drive subdivision. Peak flow rates were provided by the developer, and the following
method was used to apply these to the model.
For the three residential parts of the development the demand was applied to the model by applying the peak
flow to the DMA_TeMoana demand profile. Discussions with the developer indicated the expected total daily
demand for the Main Building may be around 100,000 l/day. A new demand profile was therefore created for
the Main Building demand, as using the standard residential demand pattern with the peak instantaneous flow
of 10l/s would result in far higher daily demand by volume.
The figures provided by the developer and the daily demands are shown below in Table 3-1.
Stantec
Status – Draft │ 08 January 2020│ Project Number – 310101208 │ Park Avenue Development Report final 08.01.2020.docx
Page 4Table 3-1: Peak flows obtained from developer
Demand Category Peak Flow (l/s) Daily Demand (l/prop/day)
Village Domestic 4.1 748
Main Building 10 n/a
Park Ave Subdivision 0.2 1,585
Ferndale Dr Subdivision 0.7 1,541
For the three residential parts of the development the demand was applied to the model by applying the peak
flow to the DMA_TeMoana demand profile. Discussions with the developer indicated the expected total daily
demand for the Main Building may be around 100,000 l/day. A new demand profile was therefore created for
the Main Building demand, as using the standard residential demand pattern with the peak instantaneous flow
of 10l/s would result in far higher daily demand by volume.
Estimated daily demands used in the model are shown in Figure 3-3, Figure 3-4, Figure 3-5 and Error! Reference
source not found.. It is recommended that the expected flow profile of the main building is confirmed before
the design of the system is finalised.
Village Domestic Demand (l/s)
5
4
3
2
1
0
00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:00
Figure 3-3: Estimated Daily Demand for 217 ILUs (748.2l/prop/day)
Park Avenue Subdivision (l/s)
0.25
0.2
0.15
0.1
0.05
0
00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:00
Figure 3-4: Estimated Daily Demand for Park Avenue Subdivision (5 properties - 1585.3l/prop/day)
Ferndale Drive Subdivision (l/s)
0.8
0.6
0.4
0.2
0
00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:00
Figure 3-5: Estimated Daily Demand for Ferndale Drive Subdivision (18 properties - 1541.3l/prop/day)
Stantec
Status – Draft │ 08 January 2020│ Project Number – 310101208 │ Park Avenue Development Report final 08.01.2020.docx
Page 5Main Building Demand (l/s)
12
10
8
6
4
2
0
00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:00
Figure 3-6: Estimated Daily Demand for Main Building
4 System Performance
4.1 Current Peak Day (2018) – Scenario 1
In the current peak day scenario (2018) using the Scenario 1 point of connection, minimum pressure of 25m can
be met for all customers when the additional demand from the proposed development is added to the model.
Pressure at the development site is predicted to remain above 40m.
However, although modelled pressures remain well above the threshold of 25m, the addition of proposed
development has a very large impact on the pressures at existing properties in Waikanae Beach. This can be
seen in the pressure comparison graph showing an increase in the pressure drop at peak demand of between
15 and 20m(Figure 4-1).
This indicates the network is severely overloaded and any inaccuracies in the model or a small increase in the
expected demand could cause the network to drop below the 25m level of service.
To ensure the continued ability of the Waikanae network to meet the level of service for minimum pressure,
mitigation will be required to reduce the impact of the proposed development.
Proposed
Development
Area
Critical Point
(Frimley Terrace)
Figure 4-1: Minimum pressures in the Waikanae network after development
Stantec
Status – Draft │ 08 January 2020│ Project Number – 310101208 │ Park Avenue Development Report final 08.01.2020.docx
Page 6Figure 4-2: Pressure comparison at Critical Customer (Frimley Terrace)
The significant drop in pressure observed at the critical point customers is caused by high head losses in mains
in the upstream network in Te Moana Road, between Main Road (old SH1) and Ngarara Road. This network is
responsible for delivery of water from Kakariki Reservoir to all of Te Moana Road, Waikanae Beach and Peka
Peka, and is already under stress. The additional demand from the proposed development therefore results in
a significant increase in head loss in this network.
Figure 4-3 shows which mains have high headloss and are causing reduction in pressure within the network.
Proposed
development
Area with high
headloss Kakariki Reservoir
- source
Figure 4-3: Option 1 - Maximum headloss throughout network
Stantec
Status – Draft │ 08 January 2020│ Project Number – 310101208 │ Park Avenue Development Report final 08.01.2020.docx
Page 74.2 Current Peak Day (2018) – Scenario 2
In the current peak day scenario (2018) using the Scenario 2 point of connection, minimum pressure of 25m can
be met all at nodes when the additional demand from the proposed development is added to the model.
Pressure at the development is predicted to remain well above the required 25m.
The situation is identical to Scenario 1, and there is a significant impact on pressures within the network when the
development demand is added to the model (Figure 4-5).
Due to the large volume of flow at peak times and the impact this has on pressures within the Waikanae network,
mitigation will be required to reduce the impact of the proposed development.
Proposed
Development
Area
Figure 4-4: Minimum pressures in the Waikanae network after development
Figure 4-5: Pressure comparison at Critical Customer
The pressure at the critical point in Scenario 2 reacts in the same way as in Scenario 1, with a significant drop in
pressure throughout the network and observed in Figure 4-5 at the critical point. This can be explained by mains
at the start of the network which have high headloss and cause the drop in downstream pressures in the network,
shown in Figure 4-6.
Stantec
Status – Draft │ 08 January 2020│ Project Number – 310101208 │ Park Avenue Development Report final 08.01.2020.docx
Page 8Proposed
development
Area with high
headloss Kakariki Reservoir
- source
Figure 4-6: Option 2 - Maximum headloss throughout the network
4.3 Fire Flows – Scenario 1 and 2
Due to negative network performance, fire flow analysis was not conducted on the un-mitigated scenarios.
5 Mitigation Options
The results in Section 4 shows the proposed development has significant detrimental effects on the distribution
network, due to the undersized network supplying all of Te Moana Road and Waikanae Beach.
This section details four mitigation options which will allow the development to be connected while minimizing
the adverse effects on the existing network.
5.1 Option 1 – Deferment: Wait for Ngarara Loop Upgrade
The high level of head loss in Te Moana Road is a known problem, and an upgrade has been proposed to
address the problem ahead of development in the Ngarara area (including Park Avenue). This upgrade (known
as the Ngarara Loop) consists of around 3km of 200mm diameter mains from Main Road (the old SH1) right
through to Field Way in Waikanae Beach. Figure 5-1 shows the proposed upgrade.
Stantec
Status – Draft │ 08 January 2020│ Project Number – 310101208 │ Park Avenue Development Report final 08.01.2020.docx
Page 9Figure 5-1 : Ngarara Loop Upgrade (from Water Network Development Plan 2017)
The first option is to delay implementation of the development (or at least the main building) until the first stage
of this upgrade has been completed.
At this stage the upgrade is due for implementation in 2025. Discussions with the developer have indicated this
is not a viable option.
5.2 Option 2 – Temporary On-site Storage
The high level of headloss observed at peak times is due to the high peak flow from the Main Building demand.
This has been modelled as occurring during the morning peak as without restriction and connecting directly to
reticulation this flow can occur at any time during the day.
Option 2 is to install an on-site tank which is restricted from filling during periods of low network pressures and
supplies the Main Building of the Retirement Village. The peak flow of the Village domestic and subdivision
developments is relatively low and therefore continues to be supplied directly from the proposed 150mm
distribution main without the need for additional storage.
This tank would only be required until the first stage of the Ngarara Loop upgrade was complete.
5.2.1 Normal Operation
A tank size of 100m3 was tested, based on the estimated daily demand of the Main Building. The tank was
restricted from filling between 06:00 and 09:00 during the morning peak and between 17:00 and 21:00 during
the evening peak. The tank inlet flow was limited to a maximum of 5l/s during permitted filling periods. This
mitigation scenario was modelled over three days to allow the tank level to achieve a steady state. The impact
Stantec
Status – Draft │ 08 January 2020│ Project Number – 310101208 │ Park Avenue Development Report final 08.01.2020.docx
Page 10on pressure at the point of supply after the development is added is shown in Figure 5-3. The tank level and inlet
flow can be seen in Figure 5-4: Tank inlet flow (3 days) Figure 5-4Figure 5-4 and Figure 5-6.
Figure 5-5
Proposed
Development
Area
Figure 5-2: Option 2 - Minimum pressures after mitigation
Figure 5-3: Option 2 - Pressure comparison at the critical point
Figure 5-3 shows there is a much smaller impact at the point of supply than without mitigation. The drop in
pressure due to the tank filling can be observed at 09:00, when there is sufficient pressure. As a comparison, this
Stantec
Status – Draft │ 08 January 2020│ Project Number – 310101208 │ Park Avenue Development Report final 08.01.2020.docx
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