4. Corridor Design. 4.1 Overarching Principles

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1 4. Corridor Design 4.1 Overarching Principles The philosophy for the urban and landscape design as outlined in the Project Overview is to provide an integrated, safe, functional and sustainable highway corridor for the proposed WBB that will: Complement and enhance existing landscape character reflecting the fertile soils and numerous watercourses while minimising the visual and physical intrusion of the Bypass effects; Provide an overall positive environmental solution (integrating stormwater management and ecological aspects); Retain or enhance the ecological and landscape objectives of the Otukaikino Creek corridor; Provide continuity of urban design and landscape treatment along the state highway corridor (and integrating with the SH1 Groynes to Sawyers Arms 4-laning project); Become a multipurpose network (integrating the stormwater treatment, bio-diversity and recreation functions); and Encourage cost effective, low maintenance and robust design solutions. The overarching principles that will guide this philosophy are encompassed in the New Zealand Urban Design Protocol, the National Guidelines for Crime Prevention through Environmental Design (CPTED) and NZTA Guidelines for Highway Landscaping, and Bridging the Gap Each of the above are explained in Section 2. The design implications for each of these overarching principles are as follows: Bridging the Gap Designing for the context: The Bypass will relate to landscape context in terms of acknowledging the floodplain, wetland and recreational areas. Ensure the Bypass will relate to landuse context relative to increasing residential development in the broader area (Belfast Area Plan). Integrating transport and land use The Bypass landscape development will reflect its rural and peri-rural setting and seeks a balance between the need to screen the arterial verses maintaining an open setting. Ensure the integration of landscape, ecological and stormwater components and that these will combine to reflect the lower Waimakariri character. Ensure good communication, a collaborative approach and co-ordinated actions between all the decision makers and user groups to lessen the effect of the Bypass on the local social and physical landscape. Contributing to good urban form The Bypass takes the regional flow of traffic and heavy vehicles in particular, away from Main North Road, being the road that also currently provides the primary northern highway link to and from central Christchurch. This change in traffic flow will potentially have a positive effect on what is the main street of Belfast though allowing Main North Road to step back from being a state highway to main, local arterial road. As the Bypass sits within a rural landscape, the focus of the remedial and mitigating landscape works will focus on integrating the Bypass with its rural and recreational setting. Integrating all modes of movement / maintaining local connectivity The Bypass will allow people the opportunity for choice in terms of transport modes through maintaining connections to cycleways and walkways. Enhance the Bypass s contribution to wider landscape values by recognising the importance of connections to other Western Corridor projects. Supporting community cohesion The links within and between recreational areas (The Groynes and Waimairi walkway) will be maintained. 24 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

2 Respecting cultural heritage values The existing ecological systems and cultural heritage values associated with sites such as Otukaikino Creek will be protected and enhanced. The land will be managed wisely in consideration of its on-going care and maintenance in a way that avoids adverse environmental effects, provides biodiversity and reduces the resources required for the long-term management of the corridor. Iwi and Runanga will continue to be engaged with through the detailed design and construction phases. Archaeological protocols are to be promoted and adhered to. Designing with nature The Bypass will enhance the distinctive landscape elements that characterise the corridor area e.g. Otukaikino Reserve, Otukaikino Creek and The Groynes while ensuring a consistent and coherent overall product. Waterways, within the corridor, will be enhanced and highlighted where affected by the Bypass. Creating a positive road user s experience The views of the surrounding landscape will be maximised. Transitions in the character of the road will be created to alert drivers when approaching a different environment. Achieving a low maintenance design Factor ongoing maintenance into the design process. Ensure maintenance access is provided. NZTA Guidelines for Highway Landscaping Principles Maintain and improve safety: Landscape structures and planting will provide visual interest to relieve driver boredom and fatigue. Planting will ensure clear sightlines to roadside furniture (signs, marker posts) and delineation around curves. Planting will not contribute to icing and light strobing of the highway. Promote biodiversity: Plant indigenous species, ideally through the use of locally sourced seedlings, appropriate to the range of environmental conditions that will enhance integrity and protect ecological values on adjoining land. Through appropriate management and maintenance regimes ensure minimisation of the risk to biodiversity, the control of weed and plant pests and the promotion of self-sustaining plant communities. Improve visual quality: Provide visual richness, through the appropriate mix of planting, site furniture, and built structures. Integrate the Bypass with the surrounding landscape by ensuring the detailed landscape design is a best practice high quality and creative design responding to the existing natural, cultural and heritage features of the corridor. Provide high quality environments that are easy to maintain and manage over the long term. Manage stormwater runoff: Reduce erosion and manage stormwater runoff and flow paths through the use of appropriate indigenous plant material and the minor contouring and earth shaping of the Bypass slopes and drainage network. Ensure the management of peak rainfall events and the protection of highway pavement by maximising the efficient flow of stormwater. Provide best practice approaches to stormwater quality control, particularly in ecologically sensitive areas by treating or removal of contaminants. Manage pests: Ensure the plant communities proposed for the Bypass will be self-sustaining when successfully established with minimal need for synthetic herbicides. 25 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

3 Ensure the plant communities proposed minimise the need for frequent vegetation control, and reduce the opportunities for competition and invasion by weed species. Planting and its long term maintenance must recognise and reduce the potential effects of animal pests and contribute to the existing animal pest control schemes operated by ECAN and CCC. Improve NZTA s business practices: Ensure the Bypass design reflects the need to minimise the long term use of management resources and minimise future life-cycle management requirements through the optimum use of the landscape investment. Select plant species that will protect or have nil effect on the integrity and efficiency of the highway pavements and the drainage systems. 4.2 Design Proposal The existing context (Section 3 of this framework) and principles have guided the overall design concept. The concept will be achieved through the following design elements: Earthworks The earthworks involve cutting for the highway formation, stormwater systems, and at the northern and southern end embankments. The embankments comprise the bulk of the earthworks. The following principles have guided the proposed earthworks: Keep bulk of highway formation close to grade to retain the flat landscape character where practicable. Utilise appropriate cut-to-waste soils onsite where possible. Integrate the fill formations through sympathetic gentle contouring and planting of fill slopes to soften the change, where practicable. To meet the principles the design has the following features: planting of fill slopes to soften the change the slope of the swale sides will be 4:1 where mowing is required and 2:1 where swales are planted embankments will have a maximum horizontal to vertical ratio of 2:1. Figure 4.1: Cross section showing scale of earthworks - the main alignment through the mid section. 26 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

4 Figure 4.2: Cross section of embankment at the southern connection Roadscape Elements The following principles have guided the proposed highway furniture: Minimise the impact of lighting on surrounding neighbourhoods by screening glare from lights. Signage should be combined onto fewer mounting posts and into fewer sign panels wherever possible. Consistency with adjacent sections of SH1. Elements should minimise maintenance and whole of life costs including landscape treatments to median and roadside while also ensuring driver safety. Safety barriers shall be adopted as the starting point (as opposed to clear zones) in accordance with safe systems principles. To meet these principles the design has the following features: The signage, median design, lighting and barriers are based on adjacent sections of the Western Corridor. A raised (kerbed) and planted median is required at the south end of the project to tie-in to the SH1 Groynes to Sawyers Arms 4-Laning Project. A paved central median is the preferred treatment for the remainder of the WBB (refer Figure 4.4) to reduce maintenance and optimise safety. Wire rope safety barrier, with posts painted white, is the preferred roadside and median treatment to provide a more open and transparent treatment compared to alternative barrier systems Concrete barrier is required at overpass structures for safety reasons and may also be required adjacent residential areas for noise attenuation and visual screening of the bypass traffic. Fencing between the Bypass and the Dog Park will be wire mesh fencing to a height of 1.5 m to ensure consistency with existing fencing within the Dog Park. This type of fencing will also ensure dogs (and their owners) do not stray on to the Bypass. 27 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

5 4.2.3 Noise Mitigation While no specific noise mitigation measures are required, the following principles have guided the proposed approach to noise mitigation: Utilise pavements that are low noise. Ensure that where practical, noise barriers follow the highway geometry. Avoid locating noise mitigation where they will obstruct significant views, both towards and from the highway. Adopt whole-of-life principles in the selection and treatment of materials. Select durable materials and finishes. To meet the principles the design has the following: Low noise surfacing along the entire route. Figure 4.3: Signage and lighting example (Christchurch Southern Motorway) Concrete barrier along elevated sections of the WBB in the area of the new Groynes Park subdivision that is currently being developed. Figure 4.4: Median example (SH1 between Plimnerton and Pukerua Bay) Figure 4.5: Concrete barrier type (from the Southern Motorway) 28 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

6 4.2.4 Structures There are three structures associated with the Bypass. These are: (i) Main North Road On-ramp Overpass: Overpass structure carrying the Bypass over the proposed northbound on-ramp connection from Main North Road to the Northern Motorway at the northern end of the project. (ii) Dickeys Road Overpass: Overpass structure carrying the Bypass over Dickeys Road. (iii) Groynes Drive Overpass: Overpass structure carrying the Bypass over Groynes Drive at the southern end of the project. Overpass Structures Design Principles Where practicable, the following principles should guide the design of overpasses: To create a sense of place through the use of a consistent and recognisable palette of materials. To create visually-light, clean slender structures of appropriate scale, form, colour and texture. To reflect and recognise the landscape context with respect to scale of new structures. To undertake surface treatment design on MSE walls, with a profiled textured finish if they are required. To identify opportunities for the integration of art (design, components) in any built structure. To make a positive contributions to the surrounding physical environment, local communities and to the users experience. To ensure structures follow sustainability best practice, minimise unnecessary costs during construction and maximise efficiencies throughout the life cycle management of the structure. Drainage systems need to be considered to prevent flooding and ponding, and to allow for satisfactory disposal of run-off. Steep earth slopes will be planted with an indigenous shrub and tree mix to help integrate with the surrounding landscape and reduce maintenance issues associated with mowing on steep slopes. Robust, long-life, vandal-proof materials and lighting should be used to minimise maintenance. On-going maintenance costs must be factored into the design process. When applying any graffiti proof coating ensure application covers full piers/faces to minimise patchy finishes. Also use one type of product for to ensure a consistent application to all structures. 29 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

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8 Figure 4.7: Groynes Drive overpass which is typical of the design of the three structures 1 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

9 4.2.5 Pedestrian and Cycle Links Proposed pedestrian and cycle facilities include: off-road shared pedestrian and cycle path linking Clearwater Avenue with the service road south of Johns Road. cycle and pedestrian facilities along Groynes Drive (shared footpath and on-road cycle lanes). pedestrian path at the toe-of the southern interchange embankment linking the Waimairi walkway to Groynes Drive (to provide continuation of the Waimairi Walkway which is severed by the Bypass). Otukaikino Track Pedestrian underpass where the Bypass passes over the Otukaikino Track/Waimairi Walkway circuit - at the northern end of the Bypass in the vicinity of the sawmill the Waimairi walkway will need to cross Darroch Street Drain, which is being realigned by ECan. A combined pedestrian and flow structure (underpass) is proposed. No pedestrian or cyclist provision is provided along the Bypass between the southern and northern interchanges, which is to be designated as motorway. However, the existing Waimairi Walkway/Otukaikino Track and potential future extension of the Groynes Reserve to the north will (by CCC) include pedestrian facilities. There is also potential for an access to be provided off Dickeys Road, west of the Bypass, with a footbridge over the Otukaikino Creek (by CCC) linking to the extended Groynes Reserve. Pedestrian and Cycle Design Principles CCC has a preference for off road shared paths over on-road cycle lanes where practicable. Connect into the existing cycle and open space networks and utilise existing features to improve the cyclist/pedestrian experience. Ensure high amenity for pedestrian and cycleways. Consider the safety of all users. Ensure path widths cater for both pedestrians and cyclists safely without collisions. Separate the paths if required. Off road paths 3m wide to cater for pedestrians and cyclists. Existing on road connections maintained on all cross roads. Ensure that 2.5m width minimum is allowed for any combined pathway. Ensure that 2m width minimum is allowed for footpaths. Ensure that shoulder provision for cyclists is a minimum of 1.5m. Ensure lighting design (quantity, location and type) creates a safe environment for pedestrians and prevents vandalism. Locate pedestrian crossings to support pedestrian desire lines and connect with the surrounding cycle/pedestrian network. Ensure the path location achieves maximum visual surveillance (from the highway corridor) and minimise feeling entrapment between high fences or embankments. To meet the principles the design has the following features: Off road shared path (Clearwater Drive to Johns Road): 3m wide shared path Separated from the road by a wire rope barrier. Groynes Drive: Realignment and widening of the road to provide a 2.5m wide shared footpath/cycleway on northern side of Groynes Drive. 1.5m shoulders on both sides of the Groynes Drive suitable for cyclists who prefer not to use the shared footpath. Consider the visual experience for both pedestrians and highway users. 30 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

10 Waimairi walkway: Realignment of walkway along the base of the WBB embankment with a 2.0m wide sealed path to link to Groynes Drive. Otukaikino Track Pedestrian underpass: The full capacity of the pedestrian underpass will be 5m wide with at least 2.5m clearance. The walkway approaches will be straight and at-grade and follow CPTED principles so that the underpass passage is clearly visible for its full length. Landscape planting will be kept well clear of the underpass approaches. Lighting, surface and colour/paint treatments will focus on creating a pleasant underpass environment, which complements the external components. Consideration will be given to including urban art on the walls of the underpass. Figure 4.8: Example of mural, lighting and anti-graffiti coating, A&P Subway, Christchurch Southern Motorway The Darroch Street Drain will pass through the underpass and its flow channel will be formed below and parallel to the walkway formation. The channel will be 1.5m wide and approximately 1m deep with mm of natural bed material in the invert. A safety/handrail will be placed between the walkway and the flow channel. Robust, long-life, vandal-proof materials and lighting would be used to minimise maintenance. On-going maintenance costs must be factored into the design process. Figure 4.9: Example of a combined bridge and cycle/walk subway, Heathcote River Bridge, Christchurch Southern Motorway 31 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

11 4.2.6 Stormwater Stormwater Design Principles The following key principles will apply: Provide a low maintenance swale and wetland stormwater system. Stormwater network to incorporate existing natural drainage patterns. Use kerb and channel in locations where space is constrained Convey a 5% AEP rainfall event or 1% AEP rainfall event where no overland flow path or storage is available. Only minor flooding of the carriageway during a 1% AEP flood event. Full capture of the Water Quality event for treatment prior to release. Minimise or avoid downstream effects. like a linear wetland with an orifice outlet to attenuate discharges and ensure low flow velocities. Full capture of the Water Quality event and its slow release either by the outlet, or via infiltration. During low frequency events, the planted swales will either attenuate up to the 1% AEP event or be by-passed / overtopped, depending on the location. The plant species used will be both wet and dry tolerant to ensure minimal die off. Under drainage systems to prevent water logging of swale inverts and to accommodate seasonally high groundwater are allowed for where levels allow. Where under-drainage is not feasible and grades <1:250 are required, the swales will be planted with wet / dry tolerant species such as Carex secta to negate the mowing of water logged soils or grass die off. Allow for the projected impacts of climate change. To meet the principles the design has the following features: Treatment will be achieved using a combination of grassed treatment / conveyance swales and planted attenuation swales which incorporate an element of attenuation and infiltration to ground. Low intensity rainfall events or low depth events will most likely infiltrate entirely to ground through the swales topsoil lining during summer months, when the catchments soils are drier. During higher intensity / depth events and during winter months infiltration may not be sufficient to deal with runoff from the road corridor. In such events flow will occur along the swales to the various basins for storage and infiltration. The planted attenuation swales will consist of a long wide strip of land planted with wet/dry tolerant native species and will be constructed at particularly flat grades (flatter than 1:500) to ensure very low flow velocities. Figure 4.9: An example of a planted stormwater swale The planted swales will act as a rain-garden; only with an orifice outlet for larger events. During winter months, if the planted attenuation swale become waterlogged or groundwater is un-seasonally high; the swales will act more 32 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

12 Figure 4.10: Typical swale cross sections 33 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

13 4.2.6 Landscape The landscape design proposal has been guided by the following principles: Landscape Design Principles Planting will provide a varied and diverse landscape environment that enhances underlying patterns and the alignments character and reflects adjacent land use and vegetation patterns. Encourage integration with the surrounding landscape through retention of existing trees, shelterbelts and stream bank vegetation, where appropriate. Existing waterways will be a predominant theme and will provide a rhythm that contracts the open rural character. Locations for planting will be based on the following criteria: establishing or reinforcing physical and visual links to adjacent planting and land uses; areas that are difficult to mow; areas that follow drainage patterns; high visibility areas; key points along the Bypass. Protect and retain existing planting where possible and practical. Utilise exotic specimen trees along the WBB with open grassed areas to reflect the existing rural pasture and hedgerow landscape, with sections of hedgerows and clusters of specimen trees to frame views. Improve local ecology and biodiversity, reinforcing existing and future ecological proposals. Utilise indigenous planting to recreate former ecosystems, based on the ecological planting themes for areas of fill batters, waterway buffer zones, and stormwater treatment areas. Species to be selected from ecotypes appropriate to the existing site conditions and soils. Re-vegetate stream margins to emphasise landscape character, enhance habitat and improve stream water quality. Rehabilitate fill batters to merge with surrounding landscape patterns and plant batters. Create a safe user environment by ensuring that the landscape treatment does not create safety issues. The final plant species selection and placement will consider fire risk, frost zones, potential shading and clear zones to the highway edge and will comply with the NZTA Guidelines for Highway Landscaping and NZTA P39 Standard Specification for Landscape Treatment to ensure sustainable long term management. 34 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

14 To meet the principles the design has the following: The varieties proposed include: Specimen Trees Botanical name Common Name Alnus rubra Red alder Castanea sativa varieties Sweet chestnut Cordyline australis Ti kouka, Cabbage tree Dacrycarpus dacrydioides Kahikatea, White pine Elaeocarpus dentatus Hinau, Pokaka Eucalyptus viminalis Manna gum Juglans regia Walnut Liriodentron tulipifera Tulip tree Liquidamber styraciflua Sweet gum Pinus halepensis Aleppo pine Platanus x acerfolia London plane Podocarpus totara Totara Quercus palustris Pin oak Embankment planting Botanical name Common Name Austroderia richardii syn Cortaderia NZ Toe toe Coprosma crassifolia Thick-leaved mikimiki Coprosma lucida Karamu Coprosma propinqua Mingimingi Coprosma robusta Karamu Coprosma virescens Karamu Cordyline australis Ti Kouka, Cabbage tree Corokia cotoneaster Korokio, Corokia Corokia 'Red Wonder' Red-berried Corokia Dodonaea viscose Akeake Griselinia littoralis Kapuka, Broadleaf Hebe salicifolia Hoheria angustifolia Kunzea ericoides Muehlenbeckia astonii Olearia paniculata Pittosporum eugenioides Pittosporum tenuifolium Phormium tenax Plagianthus regius Pseudopanax crassifolius Low shrub planting Botanical name Anemanthele lessonia Carex comans Chionochloa flavicans Coprosma acerosa Libertia ixioides Koromiko Houhere, Narrow-leaved lacebark NZ Kanuka Shrub pohuehue Akiraho, Golden akeake Tarata, Lemonwood Kohuhu, Black matipo Harakeke, NZ flax Manatu, Lowland ribbonwood Lancewood, Horoeka Common Name Wind grass Maurea Snow tussock Sand coprosma NZ iris 35 NZ Transport Agency Western Belfast Bypass Urban and Landscape Design Framework February 2014

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