Pakuranga Infrastructure Auckland Application

Infrastructure Auckland Application For Pakuranga Creek Restoration and Stormwater Management - Stage 1, Opus International Consultants Ltd, 2002.

Introduction | Site Description | Proposed Works | Financial Analysis

Introduction

Infrastructure Auckland Application
Infrastructure Auckland (IA)set up to contribute funds, by way of grants, to projects in the Auckland region providing land and passenger transport and stormwater infrastructure.

This application is made pursuant to the requirements of Infrastructure Auckland's Multi Criteria Criteria Procedures Manual. IA has provided comments to a draft of this application. Their comments and the responses indicating how this application has been modified are included in Appendix J.

Overview
This proposal is to carry out Stage 1 erosion protection and environmental restoration works along a 1350m reach of upper Pakuranga Creek which is located in the 506 ha Moony's Bridge Catchment. The purpose of these works is to improve water quality, habitat and amenity values

These works have been initiallv described and conceptualised in the Pakuranga Creek Master Plan Plan (Opus, 2001) and the Pakuranga Creek Comprehensive Catchment Discharge Consent Application (GHD 2001).

This project is part of a greater series of works which are intended to improve conditions of the Tamaki Estuarv. The greater project has been designated as regionally significant and details are documented in the Regional Stormwater Project Application for the Tamaki Estuary (Meritec 2001). These regional stormwater projects include:

Installation of centrifural debris separators (CDS) and gross pollutant traps (GPT) in the Otara, Tamaki/Papatoetoe, and Pakuranga/Tamaki catchments
Development of riparian planting in the Otara and Tamaki River/Papatoe catchments
Development of wetlands and water quality ponds in the Otara catchment
Development of riparian planting, wetlands and water quality ponds in the Moonys Bridge catchment (portions of which are this project, discussed below).

Project Proposal
Figure 1 presents the Master Plan concept for the Pakuranga stream reach in the Moonys Bridge catchment and indicates the specific reach associated with Stage 1 works. As shown in this figure, these works include:

Removing a timber-walled channel and introducing planting between Casurina Road and Pakuranga Road (future work)
Development of wetland and ponds in Wm. Green Domain and adjacent to Pakuranga College in the area north of Pakuranga Road (future work)
Stage 1 riparian works (this project discussed below), and
Development of a wetland pond system at the lower end of Lloyd Elsmore Park just above Cascades Road (future work).

Figure 1 (part a)>>
Figure 1 (part b)>>

Implementation of all these projects will allow fish passage further upstream and enhance fish/bird habitat, provide a more stable stream channel, reduce the amount of sediment being discharged into the Estuary, reduce the amount of chemicals being discharged into the Estuary, integrate landscape and habitat values from Wm. Green Park downstream through Lloyd Elsmore Park and the Cascades, and provide community betterment and a variety of education and community involvement.

Figure 2 identifies the general works layout and planting scheme for Stage 1 works. The works include:

Installing headwall, streambed and channel protection at stormwater culvert discharge locations
Installing channel protection in specific areas in theform of gabions and riprap with planting integrated throughout
Easing channel side slopes to reduce the potential for bank slumping and provide a margin fo wetland and emergent planting
Installing wetland planting to improve habitat and provide filtering and uptake of sediment
Planting terrestrial riparian margins to provide furthe bank stabilisation, shading, habitat improvement
Conducting limited weed removal to facilitate native species and plant establishment

Figure 2>>

The details of these works are further discussed in Section 2.1.

Appendix A presents the project storyboard which summarises key aspects of the project that IA is concerned with. The storyboard identifies the current situation as well estimates how the aspects would be affected in the future with and without the project.

Purpose of this Report
This report includes the full IA application for this project including:

Project Questionnaire (Appendix B)
Urban Streams Water Quality Assessment (Appendix C)
Preliminary Financial Analysis (Appendix D)
Additional Supporting Documentation (Appendices E - H)
Responses to the IA draft application review (Appendix J).

Site Description

This upper portion of Pakuranga Creek lies in central Pakuranga. The upper reaches are piped through residential areas while the lower reaches pass through several reserves, including William Green Domain and Lloyd Elsmore park, before joining with the Cascades Walkway Tributary and flowing into the Tamaki Estuary. The Stage 1 works address a reach of the creek from commerical areas at Pakuranga Road, 1350 m downstream through Lloyd Eslmore Park. Figure 3 provides a general pictorial overview of the area while Figure 4 identifies residential areas, schools and community facilities.

Figure 3>>

The Creek has been highly modified from its original condition. Meanders have been straightened, channelised and/or lined to facilitiate maintenance and accomodate flood flows. Appendix E presents a 1939 aerial photo of the area which shows that approximately 1000m of highly meandering channel from Pakuranga Highway to the Historical Viallage has been straightened so that only the lower reaches retain any sinuousity. The exposure of a once buried rising main in teh channel and the elevation difference between a former ameander near the Historical Village and the present channel bed is evidence that the upper reach particularly has been downcutting to maintain equilibrium.

The Stage 1 area is generally very open wit most stream edges consisting of open grass land. Planting has generally been ad hoc, if at all, and oriented to the reserve rather than the Creek. This planting shows little consideration of habitat values or opportunities for aesthetic or other enhancement of this once natural system.

Exotic tree species include willow, oak, pine and macrocarpa and are primarily located below the historical village. Native tree species are limited and are restricted to relatively newly planted specimen trees in grass located awav from the Creek. They are generally, kahikatea, totara, and pohutukawa. The western uplands adjacent to the stream in Lloyd Elsmore Park have also been planted in native shrub species, about 10 metres from the stream edge. This native planting mix of flax, manuka, and cabbage tree is about 10m from the stream banks and the straight line of planting relates more to the fields than the stream.

Fish passage is not encouraged by this lack of shading and overhanging vegetation which results in water temperatures that are too high. However, the existing culverts do not appear to fully restrict fish passage up until Pakuranga Road.

Social Context
Lloyd Elsmore Park provides most of the active recreation opportunities in the region and includes playing fields, other broad open spaces, a swimming pool, pond, indoor sports areas and Historic Village.

The MCC Leisure Department reports that the pool had 387,000 users during the last financial year (00/01). There were also approximately 227,600 active users and 184,300 spectators at the sports fields last year. During the last winter season, Lloyd Elsmore had over 10,000 hours of use as recorded by the Parks Booking svstem which was 4,000 more than the next highest use park.

Maori and European heritage of the local area is currently recognized and expressed through displays within the Historic Village in the centre of the park, adjacent to the Creek. Buildings have been relocated to the site and include displays on Maori and European history. The Historical Village receives approximately 26,000 visitors a year, about half of which are school groups. Consultation with the Historic Village will be conducted to highlight possibilities to strengthen links between the Village and the area of the stream directly adjacent to the Village. Potential also exists to improve interpretation of the cultural value of the Creek following consultation with iwi, and other community interest groups through information boards at key points along the stream.

At present, a walkway exists fo rmost of the stream length. This offers the community the opportunity to experiencethe stream environs first hand. However, the walkway has little integration with the vegetation or the Creek. This project will include planting to integrate the walkway with the landscape (while maintaining personal safetv) and formalising a stream crossing just below Pakuranga Road. Future stages of the Master Plan project will also seek to extend linkages with other stream areas.

The Park provides direct access from residential areas to shops, schools and recreational facilities. At present, a walkway exists for most of the stream length. However, the the walkway has little integration with vegetation or the Creek and opportunities exist for enhancing this amenity to provide a fuller recreational experience.

A number of schools are located within walking distance to the creek and the park. These include St. Kentigern, Pakuranga and MacLeans colleges, Howick Intermediate and Primarv, Buckland Beach Intermediate, Botany Downs and Elm Park Primaries, Pigeon Mtn School, Waimokoia School and others (Figure 4). St. Kentigern, Macleans and Pakuranga Colleges are involved in the educational Wai Care program for the Creek (Appendix F), while Bucklands Intermediate participates in the Trees for Survival program. The project will seek participation of some of these schools in creek planting programs.

Figure 4>>

The Highland Park Communitv House is located on Aviemore Drive adjacent to the creek. This facility has 2,000 to 2,500 users per month involved in a wide variety of groups and activities including: Toastmasters, Age Concern, Phoenix, cancer support groups, a parent bereavement group, special needs groups and Special Olympics, language classes including ESL, Chinese, Japanese and Spanish, I'lunket and a creche, diabetic support, family planning, numerous church groups etc. The Community House also sponsors programmed activities, games, crafts, etc.

Commercial areas are clustered along Pakuranga and Aviemore roads. Businesses include regional grocery and shopping areas, many restaurants and movie theatres. A Metlife residential village is also located on Aberfeldy near the Community House.
In addition to sports clubs, Historical Village and Community house users, and local residents who use the park, the creek is used as a transport corridor between local businesses on either side of the creek and as a lunchtime destination for workers.

A number of local groups have an interest in PakLtranga Creek. These groups include Friends of the Cascade, the Royal Forest and Bird Protection Societv, the Tamaki River Protection Soceity. A group of people representing Wai Care, Trees for Survival, the ARC, NIWA. etc. has met to discuss various aspects of the project.

No information is presently on display about the natuer and extent of the stream. New signage will be developed to explain and highlight the features fo the area. The project includes provision for rubbish bins, tables and seating.

Additional information about the site including ecological and water quality information are provided in the project application and reference and in Appendix E which presents Wai Care data for the creek collected by local schools.

Proposed Works

Figure 2 presents the proposed stage 1 works. Appendix G provides additional information related to the prelimnary design of the proposed works including survey data for the culverts, and works details. Working downstream the proposed works are as follows:

All culverts: To various degrees culvert outlets suffer from erosion around the headwalls, on the opposite bank and around the exit point. The downstream adjacent bank also experiences erosion in some cases due to water deflecting from the opposite bank. Figures G-1 and G-2 (in Appendix G) and Tables 2 and 3 presents dimension and survey data for affected areas around the culverts. Integrating wetland and terrestrial planting, and bank and outlet protection around the culverts is proposed as shown in Figures G throughG-6.

Site A: A 1200mm diameter culvert with protection around the culvert sides and bottom. Erosion protection directly opposite the exit point protects the bank, however stormwater then deflects back onto the near bank, resulting in erosion adjacent to an informal crossing site. It is proposed to stabilise, plant and improve the stream banks at the informal crossing, provide safer steps down to the creek and stepping stones across the creek.

B - C,: Two culverts almost opposite, one 375mm and the other 450mm have resulted in erosion on opposite banks. Upstream is further erosion due to a shopping trolley becoming trapped. It is proposed to remove debris, cut back and plant the bank as shown in Figure G-7 which presents a schematic detail of the work.

E - F: Straight portion of the stream with no culverts, some localised erosion. Install very low rock check dams to reduce stream energy and scouring of the stream bed.

L - O: This is a long, straight stretch of stream with little vegetation or cover. Riparian planting will be introduced on the western bank to link with the vegetation further up the bank. Two scallop shaped pools will be excavated to develop a lower energy pool environment.

E - O, Eastern bank: A footpath runs through the narrowbank between the stream and retaining walls and foundations of adjacent residences and business. It is proposed to keep this side free from dense planting for public safety. Instead single or small groups of trees wi11 be planted to develop shading of the stream and bank stabilisation while retaining clear sites along the path.

P - Q: Extensive bank slumping and erosion laong western bank. Works include widening and reinforcing the bank with planged gabions, rock and logs keyed into the bank.

Wester Bank: Very steep and weedy. Speciment trees will be planted to develop a shade canopy. As shading of trees increases, weeds will be removed with native species being introduced.

Q - R: Menadering, relatively shady section of stream with overhanging branches and tree roots providing some bank stabilisation, although some trees are being are being undermined by bank erosion. Works include installing rip-rap, remove weed and and fallen trees and developing enrichment planting in the existing riparian zone on the on the eastern bank.

R: Large scour in in outside meander which will be reinforced with planted gabions while the inside bank will be lowered to reduce storm velocities and to improve habitat. Figures G-8 through G-10 present schematic details of the proposed work.

Survey data of existing channel cross sections has been used in HECRAS hydraulic model to compare existing flood conditions with proposed work. The reults of this analysis indicate that the proposed works will not result in increased flood conditions. Additional routing is expected to be completed as part of final design.

It is important to remember that the transition to a more sustainable, ecologically valuable condition will take time, both to implement and to establish. Therefore an integral aspect of this project is to provide ongoing care and maintenance, especially in the first years after implementation.

It is also anticipated that of the revegetation and landscaping work will be conducted by community groups with direction from appropriate professionals. (Refer to S Fisher memo, Appendix H pgs 14-16 for Parks strategy on community planting).

Financial Analysis

The financial analuysis cost sheets are included in Appendix D. These include costs for direct and indirect capital costs, initial plant establishment and long term operation and maintenance. The costs for rock, gabions and cut to waste have relied on preliminary geotechnical studies (four boreholes). However, additional geotechnical work will be required to verify, the preliminary designs. The total estimated project cost is $659,068, of which $615,468 is for water quality improvements and $43,600 for amenities, consents and consulation. Operating and maintenance costs are estimated at 53,730 per year with 5 yearly renewal costs of $13,230.

The net present value of water duality related capital costs is $599,121.

Manukau City Council is requesting 100% funding for the water quality capital cost component of the proposed works. Reasons for requesting this level of funding are as follows:

The Stage 1 works are part of the Tamaki Estuary regionally signficant project.
Benefits of the project will affect not only local residents but users of the Historical Village and sorts facilities in in Lloyd Elsmore Park and the greater Tamaki Estuary as well.
The project has support from a number of local and greater area interest groups. Appendix H includes information on previous consultation and letters of support.