The projects below show our infrastructure work in practice, across settings as different as a working river port, a state highway through rugged country, urban rivers and drains, a stormwater treatment train, and a century-old water race being retired. The work spans the full delivery lifecycle, from consenting strategy and design through to on-site construction oversight, and both sides of the consenting table, whether we’re inside the applicant’s project team or advising the regulator.
Whanganui River Mouth & Port – Te Pūwaha
Intertidal & subtidal ecology assessments across multiple workstreams of the iwi-led Te Pūwaha partnership – supporting repairs to the river moles, reinstatement of the Tanae Groyne, and works around the Whanganui Port wharves.
Te Pūwaha is an iwi-led partnership between Whanganui iwi, the district and regional councils, and industry, formed to revitalise the Whanganui Port and the lower Whanganui River and Estuary. EOS Ecology was commissioned across two of its workstreams: by Horizons Regional Council to assess upgrades to the river training infrastructure – repairs to the North and South Moles, reinstatement of the historic Tanae Groyne, and use of South Beach as a haul route – and by Whanganui District Council to assess proposed works around the port wharves, including pile removal and a new stormwater treatment system. Together, the works are intended to secure the long-term stability of the river mouth and restore a deteriorated working port, guided by the iwi-led ‘abundance’ model that frames the project.
Across field campaigns in 2018 and 2021 we quantified the macroinvertebrate and macroalgal communities along the moles and Port Basin Wall using epifauna quadrats, sampled the soft-sediment infauna of the estuary’s intertidal and subtidal habitats – including under the wharves and through the port basin – and surveyed the proposed South Beach haul route. The revetments were dominated by little black mussel, barnacles and periwinkles, with Ulva and Sarcothalia macroalgae widespread; subtidal soft-sediment habitats supported strong populations of pipi, particularly in the main river channel. No threatened species were recorded, and sediment contamination was below the relevant ANZG guideline values – though our surveys did identify mahinga kai species including pipi, tuatua, kūtai/green-lipped mussel and tio/rock oyster that warranted careful management during construction.
Our Assessments of Environmental Effects concluded that, with the recommended mitigation measures in place, each workstream could proceed with effects on aquatic ecology that are ‘less than minor’ under the RMA. The combined project footprint is small relative to the estuary as a whole, much of the disturbed habitat will recolonise from adjacent populations via planktonic dispersal, and the repaired moles and replaced wharf structures are likely to deliver a small net gain in rocky intertidal and subtidal habitat – supporting both the working needs of the port and the abundance outcomes Te Pūwaha is working towards.
Te Ara o Te Ata – Mt Messenger Bypass
Independent freshwater and wetland ecology advisor to Taranaki Regional Council during construction of a new section of SH3 through some of the country’s most rugged and ecologically sensitive terrain.
Te Ara o Te Ata – Mt Messenger Bypass is a new section of State Highway 3 being constructed by NZ Transport Agency Waka Kotahi through rugged, ecologically sensitive country in northern Taranaki. EOS Ecology was engaged on the regulator’s side of the project – providing expert freshwater ecology advice to Taranaki Regional Council (TRC) as it monitors the consent holder’s compliance with the conditions designed to protect the region’s freshwater ecosystems. Our role is independent: helping TRC interpret the technical detail and assess whether the project is meeting its environmental commitments on the ground.
The work spans the construction-phase compliance regime – technical reviews of annual reporting, ecological management plans, culvert design reports, water quality monitoring data, environmental incident reporting, and the additional consent applications that arise as the project progresses. We attend site visits where needed and provide TRC with targeted, plain-English advice on the freshwater ecology implications of each compliance question, so the council can make timely, defensible decisions.
Fish passage and erosion control have been the standout challenges. The mountainous topography and continually improving fish distribution data mean that culvert designs need to be reassessed and adapted as construction unfolds, and EOS Ecology has been instrumental in reviewing those design changes and overseeing compliance of both temporary and permanent fish passage solutions. With construction continuing through some of the most physically demanding terrain on the New Zealand state highway network, our ongoing involvement helps ensure that one of the country’s most significant current roading projects can coexist with the native freshwater communities that occupy these Taranaki streams.
Ōpāwaho/Heathcote River Bank Stabilisation
Embedding native fish habitat into a 6 km hard-edged bank stabilisation programme and rescuing almost 3,000 fish across two years of in-channel construction.
Christchurch City Council’s LDRP518 Bank Stabilisation Project tackled bank instability along 6 km of the mid reaches of the Ōpāwaho/Heathcote River. EOS Ecology worked alongside planners, engineers and landscape architects from BECA Christchurch as the ecology design lead – responsible for ensuring that a primarily hard-edged engineering solution still delivered ecological value. Design features we helped embed included j-hook vanes, eel pipes (‘tuna tubes’), a rougher-edged profile for the rock armouring, low-flooded riparian banks, low-flow channel narrowing, and mid-channel cobble clusters. We also prepared the ecological Assessment of Environmental Effects that supported the resource consent.
Across two construction stages from early 2018 to mid-2019, EOS Ecology provided ecological oversight of the Citycare construction crew, checking that designed habitat features were installed as intended. We worked alongside CCC’s river maintenance team to trial mid-channel cobble cluster installations before broader roll-out – making sure the new structures would not create issues for routine river maintenance. Following successful trials, cobble clusters were installed in several gravel reaches to diversify mid-channel habitat and provide spawning sites for fish and invertebrates.
Alongside the design work, EOS Ecology led the fish rescue programme that responded to in-river construction activities – 88 site visits across Stage 1 (between 77 Ashgrove Tce and Beckenham Park) and Stage 2 (between 206 Riverlaw Tce and 83 Waimea Tce), relocating 2,869 fish and waikōura in total. Methods were tailored to site conditions: electrofishing in shallow sections and Gee minnow traps and fyke nets in deeper waters, with sites isolated using Hydro Response geodesign barriers, sediment curtains or sheet piling and re-fished where heavy rain overtopped them. Species rescued included common, upland, giant and bluegill bully, shortfin and longfin eel, īnanga, whitebait, common smelt and brown trout – alongside rarer native inhabitants of the river including waikōura/freshwater crayfish and lamprey ammocoetes.
No. 1 Drain Stormwater Facility & Naturalisation
Freshwater ecology input across the full project lifecycle of a post-earthquake stream naturalisation – from concept review and gaps analysis through detailed design, assessment of environmental effects, contract documentation, and on-site construction monitoring.
No. 1 Drain – a concrete-lined urban waterway running through Shirley Golf Course in Ōtautahi/Christchurch – was damaged during the Canterbury earthquakes. As part of Christchurch City Council’s Land Drainage Recovery Programme (LDRP 512), naturalisation was selected as the preferred repair option, replacing the concrete with a realigned natural channel, a large central wet pond, and a small wetland at the downstream end. EOS Ecology was the aquatic ecology specialist within the Harrison Grierson-led design and construction-management consortium, contributing across the full project lifecycle: from a concept review and gaps analysis at the start, through detailed design input and the consenting AEE, into contract documentation and on-site construction monitoring during the build.
On the consenting side, CCC held the majority of the consents needed to construct and operate the new system, but the excavation required to create the wet pond and wetland would permanently intercept the near-surface groundwater table – an effect that fell outside the existing consents. EOS Ecology prepared the aquatic Assessment of Environmental Effects (HAR01-16109-01) supporting that additional resource consent. We characterised the existing aquatic ecology of the drain – invertebrate communities dominated by common, widespread taxa of slow-flowing, soft-bottom waterways (Potamopyrgus snails, Ostracoda, Chironomus midges, Oligochaeta worms) and a fish community comprising shortfin eel, īnanga, common bully and upland bully – and concluded the effects of the groundwater interception on stream depletion and surface water quality would be ‘less than minor’. Operational monitoring was recommended (a piezometer array and discharge water quality monitoring) to confirm the assessment in practice.
On the design and delivery side, EOS Ecology contributed ecological input into the detailed design of the channel and stormwater basins/ponds, attended design review meetings, and helped specify the planting and ecological elements of the contract documentation (edge treatments, gravel additions and similar). Through construction, we provided on-site monitoring of the ecological components – rock edging, cobble placement, fish passage features and planting – backed by site visits, documentation and H&S induction, so that the design intent embedded at concept stage actually translated into the built outcome on the ground.
Buller Stream Stormwater Facility
Freshwater and wetland ecology input across concept design, detailed design, assessment of environmental effects, and construction oversight for a Christchurch City Council stormwater treatment train that transforms an artificial drainage channel into a complex of weirs, ponds and a wetland.
The Buller Stream Stormwater Facility (BSSF) is a Christchurch City Council project on a triangle of wet pasture at 218 Queen Elizabeth II Drive, Mairehau – a treatment train of six weirs, ponds and a wetland that intercepts the lower 170 m of Topps Drain (an unlined artificial drainage channel) and routes it through a forebay, three treatment cells and a wetland before discharging to Buller Stream. EOS Ecology was engaged by GHD, who led the engineering design, to provide aquatic ecology input across the project lifecycle – from concept-stage decisions, through detailed design and the consenting AEE, into on-site oversight during construction.
EOS Ecology contributed at the design table from the start – helping shape the wet versus dry first-flush pond decision, the wetland layout and construction staging (including how to manage pukeko impacts), bringing in specialist input on plant species selection, and working with the landscape architect on the form-and-planting interface and detailed-design specifications. We also prepared the aquatic Assessment of Environmental Effects (GHD02-17010-01, October 2017) supporting the diversion consent. Field surveys of three 50 m sites in July 2017 – one in Buller Stream and two in Topps Drain (including the section to be lost) – confirmed a low-diversity invertebrate community typical of soft-bottomed urban drains (Potamopyrgus snails, Sphaeriidae pea clams, Copepod and Ostracod microcrustaceans) and a fish community comprising upland bully, shortfin eel and common bully – alongside īnanga (At Risk – Declining) recorded earlier by CCC in the adjacent reach of Buller Stream.
Applying the EIANZ (2015) value/magnitude framework, we assessed the 170 m section of Topps Drain to be filled in as low ecological value, the magnitude of construction and operational effects as low/minor, and the overall residual effects as ‘less than minor’ under the RMA – provided the recommended mitigation was implemented (a site-specific erosion and sediment control plan for ECan, offline construction with the system only ‘livened’ once bare earth was stabilised and inundated-zone planting complete, dewatering discharges to land where practical, spill kits and cured cementitious materials, and pre-construction fish rescue from the section to be filled). The new channel was designed to be a substantial improvement on what is lost: pools, logs and boulders for habitat complexity, substantial native riparian planting, and fish passage features built into the three weirs of ecological concern (embedded rocks to diffuse velocities, v-notch base-flow channels) plus a baffled pipe outlet providing resting areas for fish and a fish-friendly flap gate held open most of the time. EOS Ecology provided ecological oversight on site during construction to confirm those features were built as designed.
Ōpaki Water Race Closure Management Plan
Ecology lead for the closure management plan required by Greater Wellington Regional Council before Masterton District Council retires a 100-year-old water race scheme.
The Ōpaki Water Race (ŌWR) sits just north of Masterton and has been delivering water from the Ruamāhanga River across the landscape for over 100 years, fanning out to five discharge points – four to the Waipoua River and one to the Fifth Street Wetland, which is in turn linked to Henley Lake via the Ōpaki Stream. Masterton District Council (MDC) holds the short-term consents that expire on 30 June 2026 and intends to retire the scheme. Condition 4 of consent WAR180478 requires a Closure Management Plan to be certified by Greater Wellington Regional Council (GWRC) at least one year before closure – covering high-value habitat areas, a translocation plan for aquatic species, and the timing and method of closure. EOS Ecology was engaged by MDC to deliver the ecological components of that plan.
We started with a site visit in December 2024 followed by a desktop and GIS exercise – correcting MDC’s water race layer, mapping the overland flow paths the race intercepts, and identifying the wetlands, ponds and springheads that needed direct ecological assessment. Field work on 13 May 2025 added eDNA sampling at two further sites (with GWRC), Rapid Habitat Assessments (Clapcott 2015) at four representative reaches, and wetland condition assessments by GWRC’s wetland team at the Fifth Street Wetland and Waipoua Oxbow Wetland. The combined eDNA and trapping record identified eight fish species – including At Risk – Declining longfin eel and a 2012 record of At Risk – Declining brown mudfish at the Fifth Street Wetland (not detected in subsequent surveys) – but RHA scores of 24–29.5 out of 100 and a 2016 MCI of 74 confirmed that the water race habitat itself is of poor quality, with the wetlands carrying the bulk of the scheme’s ecological value.
The Closure Management Plan we delivered sets out a three-stage sequential shutdown across April–June 2026, with sections of the network isolated by temporary bunds before the main intake is finally removed. Fish translocation will rely chiefly on electrofishing, supplemented by baited fyke nets and Gee’s minnow traps in deeper reaches, with eels (mostly shortfin) expected to dominate captures and releases spread across pre-identified sites on the Ruamāhanga and Waipoua Rivers – with separate handling reserved for brown mudfish if any are found. Permits and authorisations under the Fisheries Act, Conservation Act and Freshwater Fisheries Regulations are mapped in the plan. The plan also flags an outcome that is easy to overlook: because the ŌWR now intercepts numerous natural overland flow paths and performs a critical drainage function for surrounding landowners, the channels need to be maintained even after the intake is shut – closure of the scheme is not the same as abandonment of the channels, and the Fifth Street and Waipoua Oxbow wetlands will continue to receive runoff, stormwater and spring inputs once their constant ŌWR inflow ceases.
Fish Rescue & Relocation
Responsive, contractor-friendly fish rescue and relocation across the full range of in-channel infrastructure works – from bank repair and bridge replacement to culvert renewal, dewatering, and river sediment removal.
Most in-channel construction work – replacing or repairing a bridge, culvert or weir, stabilising a bank, realigning a stream, building a stormwater treatment facility, dredging a channel or removing accumulated sediment – requires the fish, kōura/freshwater crayfish and kākahi/freshwater mussels to be removed from the works area before machinery moves in. EOS Ecology runs fish rescue and relocation as an ongoing service for councils, infrastructure asset owners, engineering and design consultancies, and the contractors who build their projects. We work under the relevant Ministry for Primary Industries, Department of Conservation and Fish & Game permits, and we’re set up for the full range – from a one-off dewatered culvert in a small headwater stream, through multi-stage urban river bank stabilisation programmes spanning multiple years, to tidal estuarine reaches that need non-electrical methods.
We tailor capture methods to what the site actually presents on the day. In shallow, wadeable channels and dewatered sections, electrofishing is the workhorse – backed up by stop nets and isolation barriers (Hydro Response geodesign barriers, sediment curtains or sheet piling) to keep fish from re-entering. Where water is too deep we deploy baited Gee minnow traps and fyke nets overnight. In tidal or saline reaches where electrofishing will not work, we switch to fyke nets, Gee minnow traps and drag netting (a combination that removed almost 7,000 fish from a single Heathcote dredging programme – predominantly mullet, smelt, common and giant bully, estuarine triplefin, shortfin eel, īnanga and black flounder). In long culverts that cannot be electrofished, we use spotlighting and hand-netting alongside overnight Gee minnow traps. And on river sediment-removal works – where fish are inadvertently lifted out with the spoil – we developed a stockpile-electrofishing technique that recovers juvenile eels, lamprey, bullies and even flounder from slushy sediment in the truck tip-out, well after the river itself has been left.
What clients tell us they value is the responsiveness – turning up on site at short notice when a contractor calls, coordinating with the construction crew so the rescue happens at the right point in the build, and re-fishing whenever a barrier is overtopped by rain or removed for access. Fish are identified, sized, and released to suitable habitat upstream or downstream of any permanent barriers, with on-site judgement calls about whether sediment fences should be installed before or after the fishing pass, how to handle the larger ‘tame’ eels well-known to local residents, and when conditions are simply not workable. The work also extends beyond construction-driven rescues into Department of Conservation-supported transfers of threatened species – Canterbury mudfish/kōwaro from wild populations to newly created or restored habitat – but the principle is the same throughout: protect the native species that depend on these waterways while keeping the construction programme moving.
