Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Application for Resource Consent and Assessment of Effects on the Environment
Prepared by Waimakariri District Council under Section 88 of the Resource Management Act 1991
13 April 2018
Prepared by: Janet Fraser Utilities Planner (WDC)
Reviewed by: Duncan Roxburgh Regeneration Project Manager
PDU Project Number: PD000501 Author: Project Delivery Unit, Waimakariri District Council Published: February 2018 File / Record Number: DRA-07/ TRIM
1. Executive Summary
1.1 Application for Resource Consent
To: Consents North Team Environment Canterbury PO Box 345 CHRISTCHURCH
The Waimakariri District Council applies for resource consent as described below:
1. The name and address of the owner and occupier of the land to which the application relates is:
Environment Canterbury, on behalf of the Crown, managed by Land Information New Zealand.
2. The location to which the application relates is:
The Kaiapoi River bed at the Kaiapoi Wharf as defined in Appendix C, proposed for targeted dredging to enable placement in the river bed of floating pontoons, and enable vessel docking at pontoons
3. The types of resource consent sought are:
• Water take permit for abstraction and non-consumptive return of water to the Kaiapoi River • Discharge of contaminants permit for Waimakariri River tributaries • Works in the beds of rivers • Discharge to air of dust or odour
4. A description of the activity to which the application relates is:
• Excavation and piling within the bed of the Kaiapoi River • Non consumptive abstraction of water from Kaiapoi River (40-60 L/s) • Discharge water into the Kaiapoi River following dewatering of spoil • Storage of spoil on land adjoining the river, and transport of spoil to final disposal location • Future maintenance dredging around base of pontoons
A detailed description of the proposal is included in the attached plans and Assessment of Environmental Effects (AEE) which forms part of this application.
5. The following separate resource consents will also be sought for the following:
• Use of land for the stockpile and treatment of dredged material (from Waimakariri District Council) • Building consent for floating pontoons from Waimakariri District Council
6. Duration of the consent:
• A 35 year term is sought for all consents
7. An assessment of any effects that the proposed activities may have on the environment in accordance with the fourth schedule to the Resource Management Act 1991 is attached.
8. Address for service of applicant:
Waimakariri District Council Private Bag 1005
Consent Application Rangiora Wastewater Upgrade i Status: FINAL Rangiora 7440
Attention: Janet Fraser
Telephone: 0800 965 468 ext. 8867 Email: [email protected]
Consent Application Rangiora Wastewater Upgrade ii Status: FINAL Table of Contents
1. Executive Summary ...... i 1. Introduction ...... 5 1.1. Project Description ...... 5 1.2 Executive Summary ...... 5 1.3 Background ...... 6 2. Description of the Environment ...... 6 2.1. Location and Source ...... 7 2.2 Formation of the Modified Kaiapoi River Channel ...... 8 2.3 Sediment Characteristics and Fingerprinting ...... 9 2.4 Sediment Quality ...... 10 2.5 Kaiapoi River Ecology ...... 11 2.6 Surface Water Quality ...... 14 2.7 Culture and Heritage Values ...... 19 2.8 Kaiapoi River Flow Regimes ...... 20 2.9 Groundwater Environment and Hydrogeological Setting ...... 21 2.10 Existing Land Use ...... 22 3 Description of the Activity ...... 22 3.1 Proposed Pontoon Design Features and Constraints ...... 22 3.2 Proposed Dredging Excavation Spoil Quantities ...... 23 3.3 Historic Dredging of the Kaiapoi River ...... 23 3.4 Proposed Dredging Method ...... 24 3.5 Timing of Dredging and Piling Activities ...... 27 3.6 Contaminant Management ...... 28 3.7 Dewatering of Spoil ...... 28 3.8 Cultural Input ...... 31 3.9 Ongoing Maintenance Dredging ...... 32 3.10 Proposed Sediment Management ...... 33 4 Reasons for Application ...... 34 4.1 Resource Management Act 1991 ...... 34 4.2 Waimakariri River Regional Plan Requirements ...... 39 4.3 Canterbury Land and Water Regional Plan ...... 45 4.4 Canterbury Air Regional Plan ...... 48 4.5 Overall status ...... 50 5 Description of Actual and Potential Environmental Effects ...... 51 5.1 Positive Effects ...... 51 5.2 Effects on Water Quantity ...... 51 5.3 Effects on Surface Water Quality...... 53
Consent Application Rangiora Wastewater Upgrade iii Status: FINAL 5.4 Effects on Aquatic Ecology and Habitat ...... 55 5.5 Effects on Groundwater Quality ...... 57 5.6 Effects on Lower Bank/ Stop bank Stability ...... 58 5.6 Effects on Air Quality ...... 59 5.7 Effects on Human Health ...... 59 5.8 Heritage Effects ...... 60 5.9 Cultural and Tangata Whenua Effects ...... 60 5.10 Consideration of Alternatives ...... 61 6.0 Recommendations for Mitigation ...... 63 7. Applicable Regulatory Framework ...... 64 7.1 National Policy Statement for Freshwater Management (2014) ...... 64 7.2 Regional Policy Statement ...... 64 7.3 Mahaanui Iwi Management Plan 2013 ...... 65 7.4 Waimakariri River Regional Plan ...... 66 7.5 Canterbury Land and Water Regional Plan ...... 68 8. Description of Consultation Undertaken ...... 69 8.1 Consultation with Residents ...... 69 SILENT FILE AREAS ...... 73 Indicative Location Plan Kaiapoi River ...... 74 APPENDIX C: Proposed Dredging at Wharf Location Plans ...... 76 APPENDIX D: INDICATIVE SPOIL DEWATERING PLANS ...... 78 APPENDIX E: FISH MIGRATON CALENDAR ...... 80
Consent Application Rangiora Wastewater Upgrade iv Status: FINAL 1. Introduction
1.1. Project Description
The Waimakariri District Council (WDC) is applying for resource consent from Canterbury Regional Council (ECan) to dredge an area of and undertake works within the bed of the Kaiapoi River, for the purposes of creating an even bed substrate to enable installation (including piles in the river bed) and berthing of vessels at two proposed new floating pontoons adjacent to the Kaiapoi River wharf. This application is for a 35 year term of consent to provide for some further maintenance dredging of the river bed as required around the base of the facility, to ensure effective operation of the pontoons and continued access to and around the pontoon area for vessels when docking.
The proposed dredging for the pontoon establishment will provide new and improved recreational facilities for boats navigating in the river. The proposed dredging area will extend into the channel to enable berthing of vessels at the new floating pontoons.
1.2 Executive Summary The Council is seeking to coordinate, in conjunction and with the approval of Environment Canterbury, the excavation of approximately 5,000 – 6,000 m3 of sediment and underlying bed material adjacent to the proposed new river wall on the north bank of the river immediately downstream of the Williams Street Bridge, and dredging at the western end of the Coastguard launch ramp, to create a level base and sufficient depth in the river bed to support installation of floating pontoons and mooring of vessels alongside.
A separate application is being prepared for navigation channel dredging but due to programme constraints, priority is being given to pontoon dredging, which is currently programmed for the period June/July 2018.
The proposed 35 year term of consent sought would enable the Council to complete the floating pontoon installation at the redeveloped wharf (including the installation of piles in the river bed), and provide for further years of consecutive maintenance dredging over the 35 year term of consent, if required.
The excavation calculations are based on rough order volume estimates and there is considerable uncertainty in actual volumes which will be extracted.
Sediment contamination testing in the Kaiapoi River bed at the site of floating pontoon 1 has indicated that the risk of environmental impact from dredging activities would be low, in terms of the potential release of chemical contamination into the river. These findings are discussed further in “description of the environment”.
On the basis of these results, the excavated sediment may be appropriate for application to land at locations other than an authorised landfill. The saline content of the spoil will also influence the proposed final disposal locations, with, for each location, the future “inert” or non-productive potential land uses to be required to be considered alongside productive future land use options, in case saline content in spoil remains, following dewatering.
Spoil reuse options include use of land within the Regeneration Area. The Council proposes locations to dewater spoil on the riverbanks on the outside of the stopbanks at the Corcoran Reserve and Askeaton Reserve, and final re-use of spoil in the Regeneration Area.
The re-use of excavated spoil within the Regeneration Area will be addressed in a separate consent application.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 5 Status: FINAL 1.3 Background
The proposal for dredging the Kaiapoi River bed to establish floating pontoons is a part of the Council’s Kaiapoi Regeneration Project. The pontoons would be located in the town centre immediately adjoining the planned new Kaiapoi town centre precinct, where new restaurants and shops are proposed to be developed over the next few years, as a part of the town centre redevelopment.
The proposed floating pontoons are a part of the master-planned redevelopment of the Kaiapoi River Wharf and Marine Precinct, which is a multi-year project. The pontoons are a part of the current phase of works, including:
• Further stopbank repairs and reconstruction (by Environment Canterbury) • River wall (north bank) upgrades • Riverview terraces and boardwalk • Floating pontoons and dredging
The two floating pontoons proposed (which both require piles in the river bed and dredging as discussed in this application) are: • The ‘Riverview’ pontoon (located between the wharf and Williams Street bridge); • The Boat Ramp pontoon (located adjacent to the Coastguard slipway).
In conjunction with this work, a development company are privately developing the Riverview development on the former Bridge Tavern and Hansens Mall site. This facility is planned by the developer to open to the public in November 2018. There are also private groups proposing re-establishment of marine-based tourism ventures on the Kaiapoi River, who would utilise the pontoons.
An outline configuration and conceptual level of service was agreed at a series of meetings of the Regeneration Steering Group during 2017, which informed and evolved the various concept and detailed design stages for the pontoons. Input to the pontoon designs was also provided by the Riverbanks Steering Group during its meetings in 2016 & 2017, which included ECan representation.
A separate resource consent application is being simultaneously prepared to create a minimum 1.5m depth navigation channel at low tide from the Williams Street Bridge to the confluence of the Kaiapoi River with the Waimakariri River. That separate project would involve dredging several “high points” from the bed of the river which have been identified by the Coastguard as impeding their navigation at low tide.
When considered together, all of the above works will enable berthing at the proposed new pontoons whilst improving safety of navigation for vessels in the river and for the Coastguard navigating at low tide. Improvements to the navigation channel may also enable larger vessels to navigate the river in future at low tide and increase use of the new pontoons and redeveloped wharf. However the establishment of the floating pontoons is a high priority project and is the focus of this application.
2. Description of the Environment
This application proposes dredging in the Kaiapoi River at the Kaiapoi wharf area. This section highlights the following:
• The location of the Kaiapoi River • Historic formation of the river channel • River sediment characteristics and “source fingerprinting” • Sediment quality • Kaiapoi River ecology • Surface water quality • Cultural and heritage values • Kaiapoi climate data Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 6 Status: FINAL • Kaiapoi River flow regimes • Groundwater environment and hydrogeological setting • Existing land uses
2.1. Location and Source
Greer and Meredith 2016 (p.1) explain that “The Kaiapoi River is a spring-fed stream that arises on the northern side of the Waimakariri River stop-bank, approximately 2 km east of where the Eyre Diversion discharges to the Waimakariri.
The upper Kaiapoi River receives flow from the Eyre Main Drain and Englefield Stream before meeting the Cust River/Main Drain and Ohoka River at the three streams confluence, just west of Kaiapoi township. Although the Cust River receives some run off from the eastern faces of the hills between Ashley Gorge and Oxford township, and has a hill- fed form throughout its length…it is predominantly a spring fed river. The Ohoka River is also spring-fed and has a catchment that drains the area east of Mandeville North between Tram and Mill Roads. Below the three streams confluence, the Kaiapoi is met by the Cam River/Ruataniwha, which receives spring fed flows from the North, Middle and South Brooks. Downstream of the confluence with the Cam River the Kaiapoi River has a tidal influence”.
The Kaiapoi River proposed dredging reaches are within the Kaiapoi urban town centre. Kaiapoi had a population of about 11,000 people as at 2015.
The following location plan indicates the spring fed source and lower major tributaries of the Kaiapoi River. The highlighted circle is the area within which the targeted dredging reaches are located.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 7 Status: FINAL Proposed dredging area
Figure 1: Kaiapoi River site and proposed dredging location (source: Hudson and Tonkin & Taylor 2015, p.8; based on Google Earth 2015).
2.2 Formation of the Modified Kaiapoi River Channel
The Kaiapoi River is a modified channel which was part of the north branch of the Waimakariri River prior to European development of the area. Large swamps surrounding the “north branch” were dewatered during creation of an extensive drainage network in the area that is now urban Kaiapoi and surrounds.
Providing details of this process, Hudson and Tonkin & Taylor (2015), on page 8 state that “Swamp drainage began in the 1950’s, and in 1929 the Eyre River was diverted to the Waimakariri River (then called the Courtenay) and the Cust River into the Cust Main Drain which now flows into the Kaiapoi River. The Waimakariri River was channelized in the 1930’s, removing a complex of islands and channels. Extensive stopbanks, over the lower 40km of the Waimakariri River
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 8 Status: FINAL cut off the Waimakariri South Branch and the North Branch which became the Kaiapoi River, thus establishing the present drainage pattern”.
“With the realignment of the lower Waimakariri River into a single channel, the remnant secondary channels were isolated to form the present day Kaikanui and Courtenay Streams. The historic island near the present day Kaiapoi mouth become the right bank of the Kaiapoi River” (Hudson and Tonkin & Taylor (2015), page 8).
“The historical legacy of the Kaiapoi River once being part of the Waimakariri River North Branch has resulted in a channel size that is significantly larger than that which would have formed naturally from contemporary streamflow. When considered in conjunction with the strong tidal influence (formal a tailwater controlled river), relatively flat river grade and catchment flood flows, the flood conveyance capacity of the current Kaiapoi River appears to be substantially in excess of the catchment flood flows” Hudson and Tonkin & Taylor (2015), page 18.
“It is further noted that the primary purpose of Kaiapoi River stopbanks is to prevent flooding of the Kaiapoi township due to floods on the Waimakariri River (with a pre earthquake capacity understood to be up to 1 in 450 year design flood), where the high tailwater results in a backwater effect up the Kaiapoi River, and not flooding of the Kaiapoi River catchment (Ashley River breakout excluded)”(Hudson and Tonkin & Taylor (2015), page 18).
2.3 Sediment Characteristics and Fingerprinting
The Kaiapoi River is a tidal river with suspended sediment carried up and downstream within the tidal flows. The tidal effects are described in Hudson and Tonkin & Taylor (2015, p.8) as occurring as far upstream along the Kaiapoi River and into the Cam River to near Bramleys Road (6.5km upstream of the Kaiapoi confluence with the Waimakariri).
Hudson (1999) found that over a tidal cycle at the Cam River mouth, about 4.9 tonnes of suspended sediment moved downstream and 1.2 tonnes moved upstream on the incoming tide. Sediment “fingerprinting” suggested that backwash from the Waimakariri River and Kaiapoi River (with some lower Cam and Kaiapoi River bank erosion) are major sources, providing up to 60 or 70% of the suspended sediment at the Cam River mouth.
Hudson and Tonkin & Taylor 2015 (p.16) stated that “Underlying bed material composition in the lower Kaiapoi River is complex. The area is broadly divisible into a western alluvium fan zone, and an eastern zone with estuarine and marine (coastal) sediments that were deposited over glacial outwash gravels. The wedge of fine grained coastal sediments were deposited as the sea level rose to its present level of the last 6,500 years. River sediments have continued to build up extending the coastline eastwards (Brown & Weeber 1992). In the case of the Waimakariri, contemporary coastal build up is sand, not gravel”.
“On the Kaiapoi River the transition between the Waimakariri and Ashley derived gravels and the coastal sediments is around the present day Cam River mouth. Upstream of the Cam River mouth gravels are near the floodplain surface and gravel is exposed in the river bed (Hudson 2011); whereas downstream some gravel is exposed on the bed, but gravel deposits are reported in bore holes at a depth ranging from -3m to -11m below the floodplain surface. Based on the available river cross sections (with thalweg depth shown in blue relative to floodplain levels) it is likely that gravel may be intersected by the present day channel. However, the gravel in the deepest part of the channel and edges may be masked by fine sediment deposits (Hudson 2011). It is also possible, that lenses of gravel may have built up over the coastal sand deposits from the historic North Branch of the Waimakariri River” (Hudson and Tonkin & Taylor 2015 (p.16)).
“It is interesting to note that the gravel lobe of the Waimakariri River extends over coastal sand deposits, but does not reach the sea. As discussed in Hudson (2005), the tongue of gravel in the Waimakariri River extends downstream to near the Kaiapoi confluence (i.e. river km 2.5). In 1927 the gravel tongue was around 5.5km from the coast, in 1930 around 4.9km from the coast, and in 1960 about 3.0km from the coast. This downstream progression of a lense of gravel is unlikely to have occurred in the Kaiapoi River after it was isolated from the Waimakariri with the Hays No.2 scheme of 1928, when the Waimakariri lobe was about 5km from the sea. The equivalent position in the Kaiapoi River is in the Motorway Bridge to Cam mouth reach” (Hudson and Tonkin & Taylor 2015 (p.17)).
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 9 Status: FINAL
2.4 Sediment Quality
The river bed sediment in the proposed dredging area has been sampled to provide an indication of its general characteristics and to identify any contaminants within the sediment.
A report prepared for the “Kaiapoi Wharf and Marine Precinct Project: Kaiapoi River Sediment Investigation” by Opus in June 2017 (attached to this application) shows results of sediment sampling in the area adjacent to Pontoon 1 (next to the redeveloped Kaiapoi wharf). There were 14 sediment samples collected from 3 boreholes at a depth of up to 2m below the surface of the sediment, with each sample taken at 400mm increments. The samples tested for contamination associated with current and historical land uses and were considered to represent a wide range of contaminants most likely to be associated with local industry and agricultural activities.
The following contaminants were analysed:
Volatile and Semi-Volatile organic compounds (VOC’s), (SVOC’s) including petroleum hydrocarbons (e.g. PAH’s, BTEX), Phenols and OCP pesticides. pH values Heavy metals (including chromium, mercury, tin, lead, zinc, copper, boron, arsenic)
The findings of the investigation were:
• VOC and SVOC results were below laboratory detection limits and adopted criteria in all samples.
• pH values were all between 6 and 8 and considered neutral and not a constraint.
• The heavy metal results are all less than the NES soil contaminant standards for protection of human health under all land use scenarios
• One sample returned a lead concentration that marginally exceeded the adopted sediment quality criteria for ecological protection
• Background soil concentrations were taken from a point on the river bank adjacent to the proposed Pontoon 1 area and are the relevant comparator for assessment of suitability of spoil disposal to either cleanfill or to other land.
• All but three heavy metal samples returned results less than reported background soil concentrations. Background soil concentrations are the adopted criteria for clean-fill disposal.
• These three samples showed marginal exceedance of the reported back ground concentrations for Chromium, Lead or Zinc.
• In this case, a clean-fill operator could be approached to determine acceptability of the sediment for disposal based on averaged results.
• Material will almost certainly need to be dewatered prior to any re-use.
• There is no apparent link between the results obtained and the depth or location from which the sample was taken. There was no apparent difference in results when comparing samples taken from sediment and those taken from gravel (although only 2 samples were taken from gravel)
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 10 Status: FINAL The overall findings are that the risk of environmental impact from piling and dredging activities would be low, in terms of the potential release of chemical contamination at/from this site. As the proposed dredging area for the Pontoon 1 is in a deep deposition area in the centre of urban Kaiapoi within the town centre and immediately adjacent to the wharf, it is considered likely to be representative of sediment contamination levels likely to be found at the other proposed dredging sites intended for Stage 2 and Stage 3. All other targeted dredging sites are further downstream of the Kaiapoi town centre, moving into more naturalised reaches of the river.
On the basis of the results, the report concluded that the sediment may be appropriate for application to land at locations other than an authorised landfill.
Previous testing of sediment in 2008 was to a depth of only 750mm which was required prior to dredging at the previous MV Tuhoe berth. This earlier sediment contaminant testing was at a distance of about 100m from the eastern end of Pontoon 1.
With regards the outcomes of this testing, as reported by Opus in 2017 in the attached report “Kaiapoi River Sediment Investigation”, page 7: “Six river sediment samples were collected in September 2008 by ECan’s Contaminated Sites Team at locations near to and extending several hundred metres upstream and downstream of Williams Street bridge. Samples were analysed for pesticides, semi-volatile compounds (SVOCs), total petroleum hydrocarbons and metals including tin and mercury. The investigation found that:
• Five of six samples exhibited results below laboratory detection limits for all organic compounds analysed. The remaining sample only exhibited a low level of petroleum hydrocarbon compounds. • While many of the inorganic (metals) results were above the Regional Background Concentrations for those elements for the area of Kaiapoi, none of the metals results exceeded concentrations that would place restrictions on the disposal of the river sediments, if dredged.
ECan concluded that the sediment collected at the MV Tuhoe therefore did not warrant any special handling or disposal requirements other than standard dredging methods as required by the Regional Council”.
2.5 Kaiapoi River Ecology This section contrasts ecological values in the upper Kaiapoi River and some of its tributaries with those in the proposed dredging reaches.
The applicant has reviewed fish survey and macro-invertebrate studies in and upstream of the proposed dredging reaches in order to understand the ecological values and functions of each reach of the river.
There has been recent evidence in Kaiapoi that increasing salt intrusion into the Kaiapoi River has caused a “die back” of some aquatic plants including water weeds (macrophytes) which previously extensively covering the mud flats, together with willows and some fish species in the period 2012 to 2015. It is possible that the “die back” could have been caused by a combination of effects from the Canterbury earthquake sequence and/or changes in the river aquatic flora and fauna from increasing saline intrusion. Climate change and recent unusual weather patterns may also be a factor. There have been anecdotal comments that salmon fishing is increasing in the lower Kaiapoi River and trout fishing is possibly experiencing a sharper decline than previously understood.
2.5.1 Fish Surveys Fish sampling in the Kaiapoi River has been undertaken at various locations within several studies. Results are compiled in the table below to indicate fish species likely to be present upstream of and within and the proposed dredging reach. The Kaiapoi River at Neeves Road and Courtenay Stream sampling results were provided by Golder in 2009. The Silverstream results were provided by Kingett Mitchell in 2006. The Neeves Road site is about 5km upstream of the proposed dredging reach. The Silverstream is about 3km upstream of the dredging reach and Courtenay Stream intercepts the Kaiapoi River downstream of the dredging reach. Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 11 Status: FINAL
Species Threat Status Upper Upper Kaiapoi Courtenay Mid Kaiapoi Lower Kaiapoi Kaiapoi River Stream River River River (Silverstream)* (urban town (downstream of (Neeves centre)** Courtenay Road) (Mill Road to Confluence)** Courtenay Confluence) Common Common native 3 Present bully Shortfin eel Common native 1 Present Present Brown trout Introduced 1 Present 1 Long fin eel Gradual decline 1 Present Black Common native 2 flounder Giant bully Common native 2 1 Rainbow Introduced 1 trout Common Common native 1 Present smelt Chinook Introduced Present salmon Koura Gradual decline - 1 Inanga Spawning Two spawning Two spawning spawning site sites sites habitat identified*** identified*** identified**
Table 1: Fish Species Surveyed in the Kaiapoi River
*Silverstream sampling undertaken by Kingett Mitchell in the report “Aquatic Values of the Kaiapoi River in Relation to the Proposed West Kaiapoi Development”, 2006, p.13.
** Mid and Lower Kaiapoi River sites from AEL survey in 2012 (inanga spawning site, AEL 2012 p.26).
*** Spawning sites observed by AEL in 2017 (pages 11 and 12).
The table shows two species in gradual decline (long fin eel and koura) are present in the upper Kaiapoi River. Kingett Mitchell (2006) also comment “it is likely that a number of whitebait species also exist in the river but have not been recorded during surveys. The diversity of the fish community reflects the quality of the fish habitat that the river provides and the proximity of the river to the sea and its high level of accessibility to diadromous species” (p.13).
A report by Golder Associates titled “Minimum Flows and Aquatic Ecological Values of Lower Waimakariri River Tributaries” published June 2009 states “Recent national angler survey results of Unwin (2009) indicate that the Kaiapoi River is the most heavily fished lowland river in Canterbury, with the lower reaches of the Kaiapoi River being particularly popular for salmon fishing. One of the reasons for the abundance of salmon in the Kaiapoi River is that there is a salmon hatchery in its upper reaches (known as Silverstream)” (p.16).
Over a longer term trend “In a study of angler perceptions of the quality of lowland trout fisheries throughout New Zealand, Jellyman et al. (2003) found “ a strong consensus that angling quality had declined over up to 70 years of record, with two-thirds of the assessments indicating that angling had become generally or markedly worse. Changes in angling quality appeared to reflect changes in fish abundance rather than fish size, suggesting that for lowland river fisheries availability of fish rather than fish size was the main determinant of angling quality.” “The study also found that …. In the Waimakariri River tributaries, declining water quality, rather than flow was considered by anglers as the cause of reduced angling quality and catch rates”, Golder 2009, p.16.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 12 Status: FINAL All of the sites, including Kaiapoi River at Neeves Road, are considered to “provide significant habitat for eel, other native fish and trout ….and significant whitebait habitat” (Golder 2009, p.14).
“In general, the upper section of the Kaiapoi River within the West Kaiapoi Development Block [e.g Silverstream subdivision reaches] is shallower, narrower, has swifter velocities and has coarser bed sediments than the lower section. Thus, the upper section of the river would potentially provide better habitat for fish (especially salmonids) spawning, while the lower reach would provide better habitat for adult salmonids and angling”(Kingett Mitchell 2006, p.8).
The effects of the ongoing sediment deposition on the Kaiapoi River bed over time have included reduction of trout spawning habitat and a degraded habitat for native fish and some pollution sensitive invertebrates. The lower Kaiapoi River does not have heavy macrophyte growth due to the combination of shading of large reaches of the river by willows and potentially, the salt water wedge. Many dangerous or overhanging willows (some of which may have been recently damaged by salt intrusion) have been removed by Environment Canterbury in the summer of 2017/18 to protect the stability of the stopbanks. This has recently exposed larger areas of the channel bed to additional light, particularly within the shallow margins above the dredging reaches. It remains to be seen whether this will have any effect on future macrophyte growth in the river, given the extent of salt intrusion which is understood to extend inland to about as far as the Railway Bridge.
There are no regionally rare native fish species known in the Kaiapoi River. Canterbury mudfish, a nationally endangered species, is not known to be present in the Kaiapoi River. Mudfish are only known in the Waimakariri River catchment in the upper reaches of the Eyre River (Greer & Meredith 2016, p42).
2.5.2 Spawning Locations
Studies show current and historic spawning habitat for whitebait (inanga) is available near the proposed dredging reach. For trout, spawning habitat is available in reaches of the upper Kaiapoi River several kilometres above the proposed dredging (and some Kaiapoi River tributaries) in less heavily sedimented reaches. For salmon, spawning reaches are available in the upper Kaiapoi River and, as with trout, favour areas of cobble, with riffles.
Current and historic whitebait spawning sites were investigated by AEL in 2017 in the Kaiapoi River. Two historic sites were known in the lower Kaiapoi River between the Courtenay and Waimakariri confluences (this is within the proposed dredging reaches with one site inferred to be opposite the Askeaton Boat Ramp – see AEL 2012 for discussion of site locations). More recently in 2017 a further inanga spawning survey found “One habitat was one on the sun-exposed true right bank upstream of Raven Quay while the other was on the true left bank, about 20m upstream of the confluence with the Cam River” (AEL 2017, p.12) (both of these are upstream of the proposed dredging reaches). “The Kaiapoi River … spawning sites located during this survey were both further upstream than their pre-earthquake counterparts” (AEL 2017, p12). A further current site was found in the Courtenay Stream (AEL 2017. p.12).
AEL in 2012 explain that very early inanga spawning is possible in January, with February an early spawning period. March and April are the peak inanga spawning periods. In April early fry are hatching and going to sea. In May, most fish are in their post-spawned state, with fry hatching and going to sea on the ebbing tide. From June, spawning is not known to occur and most eggs would have hatched.
The 2017 AEL inanga spawning survey, and historical survey comparison found a range of inanga spawning sites in different locations at various times both within, upstream of and in tributaries flowing into the proposed dredging reaches.
AEL in 2012 report trout spawning reaches in a plan of the upper Kaiapoi River (p.30). Trout spawning is however not thought to occur in the dredging reaches in and downstream of the Kaiapoi town centre, due to the heavy sedimentation in these areas.
The report also notes “Riffle habitat is favoured by many native fish species and spawning salmonids…. and is known to occur in at least some reaches elsewhere within Kaiapoi River.”(Golder 2009, p.11) The proposed dredging reach is
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 13 Status: FINAL clearly gentle “run” habitat, without obvious riffles, although riffles are available for salmon spawning in the upper Kaiapoi River upstream of the dredging areas.
The Golder 2009 report states “significant Chinook Salmon gravel bed spawning habitat is considered to occur in the Kaiapoi River, Greigs Drain, Courtenay Stream and the Cam River” (Golder 2009, p.14), which are all tributaries of the Kaiapoi River.
2.5.3 Macro-Invertebrate Habitat
The urban reaches of the Kaiapoi River within the dredging reaches are highly modified and unlikely to provide suitable habitat for pollution sensitive invertebrate species. For instance, Golder 2009, p.13 comments “at most sites sampled for this study, the invertebrate fauna was dominated by amphipod crustaceans, reflecting the stable, spring-fed source of flow and ample macrophyte cover. Other common invertebrate groups included snails (mollusca), oligochaete worms and dipterans”. Although referring to the sample site on the Kaiapoi River at Neeves Road, the findings are also likely to similarly apply to other urban more modified reaches of the Kaiapoi River within the proposed dredge areas, similar to other lowland streams within urban environments.
Further, from Kingett Mitchell (2006, pages 11 and 12) “the mid and lower Kaiapoi River sites were dominated almost entirely by crustaceans. Mayflies and caddisflies together comprised less than 13% of the total fauna present at either of the Kaiapoi River sites samples [Silverstream reach, about 3km upstream of the proposed dredging reach]. “Amphipods were the most abundant crustaceans at all sites sampled. The dominance of amphipods at the two Kaiapoi River sites reflects the habitat that is provided in this stretch of river. Amphipods can be particularly abundant at stream sites with sluggish flow, silt dominated stream beds, and a high proportion of macrophyte cover as is the case at the mid and lower Kaiapoi River sites”.
Greer and Meredith in 2016 (p.42) state that “invertebrate communities are generally in a degraded state in spring-fed rivers in the Kaiapoi River catchment…. Recorded QMCI scores for the Kaiapoi and Cust Rivers vary markedly both within and between sites. While sites in the lower Kaiapoi River … at Island Road [about 2.4km upstream of the proposed dredging reaches] did not meet the LWRP QMCI outcomes in the last five years, upstream sites in these rivers regularly did”. The Kaiapoi River at Island Road QMCI results, with a mean score of 4.0, failed to reach LWRP outcomes over the years 2012 to 2015 in any year. However complying QMCI results were achieved for the upper Kaiapoi River at Heywards Road between 2011 and 2015, indicating preferred habitat for pollution sensitive species in the upper Kaiapoi River.
2.6 Surface Water Quality
Surface water quality in the Kaiapoi River in the dredging reaches is described in several existing reports. For instance:
In a report by Kingett Mitchell titled “Aquatic Values of the Kaiapoi River in Relation to the Proposed West Kaiapoi Development” published September 2006, p.6 “Water quality in the Kaiapoi River degrades downstream, within Kaiapoi township and downstream of the confluence with the Cust Drain and Cam River, to the confluence with the Waimakariri River (Daly 2004). The Cam River and its tributaries receive stormwater and historically received treated sewage from Rangiora township. Downstream of Kaiapoi township, stormwater and industrial wastes are discharged into the Kaiapoi River and its tributaries. These discharges contribute to a general decline in water quality in lower reaches of the river. Data is mainly restricted to indicator bacteria and suspended solids and indicates that the Kaiapoi River becomes more turbid, with higher suspended solids concentrations and higher indicator bacteria levels.
The lower reaches of the Kaiapoi River are tidally influenced, which, combined with the river’s soft and easily suspendable bed sediments, is a likely reason for elevated turbidity. Indicator bacteria in the lower reaches of the river have regularly exceeded recreational water quality guidelines (MfE 2003) and stock watering guidelines (ANZECC 2000), restricting the use of the river in this section. A few historic data points suggest high ammoniacal-n concentrations, which may have Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 14 Status: FINAL been related to sewer overflows from Kaiapoi, but were below guidelines for toxicity to aquatic ecosystems (e.g. ANZECC 2000)”.
“More recent data for the Kaiapoi River was collected in July 2006 from three sites within the stretch of the river adjacent to the proposed development [this refers to the Silverstream upstream of proposed dredging reaches]. Water quality at the three Kaiapoi River sites was generally similar, with a slight decrease in clarity downstream. All sites had high Dissolved Oxygen, neutral pH, low DRP and low metal concentrations. Dissolved oxygen saturation exceeded 80% at all sites, which is the standard required in the Waimakariri River Regional Plan. Low metal concentrations reflect the current lack of stormwater or industrial wastewaters being discharged into the upper reaches of the Kaiapoi River” [note: this analysis refers to sites in the Silverstream approximately 3km upstream of the proposed dredging areas and were taken prior to the Silverstream residential development].
“Nitrate-N was elevated at around 4.4gm3 at each of the Kaiapoi River sites and was the predominant form of nitrogen in the river”. “Overall, the water quality of the upper Kaiapoi River is high for a lowland waterway and its quality reflects its spring – fed source”(p.7).
It is noted that nitrogen and phosphorous, although known to be present in quantities exceeding LWRP standards in the Kaiapoi River, are predominantly agricultural source contaminants. The mitigation of these is managed by rural property owners in conjunction with Environment Canterbury and is outside the scope of this application. The dredging activities proposed are not understood to have any impact on, or could in any way be impacted by these agricultural source contaminants present in the river.
The Council in 2016 undertook baseline water quality monitoring for Kaiapoi. One of the sample sites was downstream of the proposed dredging area, within the Kaiapoi River channel adjacent to Hall Street. For comparison, data from another sample site south of the Motorway Bridge is also reviewed in this application, just downstream of the Silverstream subdivision and about 1.5km above the upper end of the proposed dredging reach.
The attached baseline water quality data spreadsheet shows that many of the other Kaiapoi River tributary waterways, including the Silverstream and Cam River had Total Suspended Solids (TSS) concentrations below the detectable limit (3mg/L) or at relatively low levels in each sampling event, whilst the lower Kaiapoi River (and sometimes also the Kaikanui Stream) had higher levels of suspended sediment.
The sample site in the lower Kaiapoi River adjacent to Hall Street had the highest suspended sediment of all sample locations in and around the Kaiapoi waterways. This is shown in the water quality data spreadsheet provided attached to this application. Results of baseline sampling within the proposed dredging reaches (Hall Street) and about 1.5km upstream (south of Motorway Bridge) are summarised in the table below to characterise usual water quality in the Kaiapoi River upstream of, and within the dredging reaches. Sample results which exceeded CLWRP standards are highlighted in red, for quick reference.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 15 Status: FINAL
Table 2: Lower Kaiapoi River (Hall Street -within Dredging Reaches) Suspended Sediment, Bacteria and Dissolved Metals
Sample Location Time and TSS (gm3) E.coli Dissolved Dissolved Dissolved Site Date Zinc Copper Lead
GV 50mg/L GV 550 0.015mg/L 0.0018mg/L 0.0056mg/L E.coli /100ml LWRP LWRP 95% ANZECC 90% species protection level Protection Level
KAKR005 Lower Kaiapoi 4/08/16 31 180 <0.0010 <0.0005 <0.00010 River (Hall 14:10 Street) KAKROO5 Lower Kaiapoi 19/09/16 10 210 <0.0010 <0.0005 <0.00010 River (Hall 14:15 Street) KAKROO5 Lower Kaiapoi 13/10/16 12 17 <0.0010 <0.0005 <0.00010 River (Hall 13:35 Street) KAKROO5 Lower Kaiapoi 12/12/16 30 900 <0.0010 <0.0005 <0.00010 River (Hall 14:15 Street)
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Table 3: Kaiapoi River at Motorway Bridge (about 1.5 km upstream of Dredging Reaches) Suspended Sediment, Bacteria and Dissolved Metals
Sample Location Time and TSS (gm3) E.coli Dissolved Dissolved Dissolved Site Date Zinc Copper Lead
GV 50mg/L GV 550 0.015mg/L 0.0018mg/L 0.0056mg/L E.coli /100ml LWRP LWRP 95% ANZECC 90% species protection level Protection Level
KAKR037 Kaiapoi River 4/08/16 6 200 <0.0010 <0.0005 <0.00010 (South of 11:50 Motorway Bridge) KAKRO37 Kaiapoi River 19/09/16 4 510 <0.0010 <0.0005 <0.00010 (South of 12:25 Motorway Bridge) KAKRO37 Kaiapoi River 13/10/16 <3 150 <0.0010 <0.0005 <0.00010 (South of 11:55 Motorway Bridge) KAKRO37 Kaiapoi River 12/12/16 4 2800 0.0026 0.0008 <0.00010 (South of 13:35 Motorway Bridge)
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 17 Status: FINAL
Figure 2: Sampling Site Locations Baseline Water Quality Sampling Kaiapoi River 2016
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 18 Status: FINAL The above summary tables show higher levels of suspended sediment in the lower Kaiapoi River within the dredging reaches, and occasional likely spikes of indicator bacteria level samples. In comparison, relatively low suspended sediment and relatively higher indicator bacteria is recorded in the Kaiapoi River at around the Motorway Bridge.
The laboratory was not able to detect any dissolved copper, lead or zinc in any of the surface water samples in the lower Kaiapoi River during any of the sampling events. Although in the upper Kaiapoi River on one occasion the laboratory detected dissolved zinc and copper in one sample, the levels detected did not exceed the LWRP Schedule 5 Guideline Value for ecological protection at the 90% protection level.
Levels of Dissolved Oxygen in the Kaiapoi River are included in the study by Greer and Meredith (2016) who note that, for the study sites at the Kaiapoi River at Harpers Road, Heywards Road and Island Road (upstream of the proposed dredging reaches) the recorded minimum dissolved oxygen saturation exceeds the LWRP outcome (of 70%) consistently over the monitoring period from 2011 to 2015, other than for only one single sample at Harpers Road. This indicates usual dissolved oxygen levels in the Kaiapoi River (upstream of dredging areas) meet the LWRP outcome on most occasions.
Several factors affect the amount of oxygen dissolved in the water in waterways. Colder water usually has more oxygen, because gasses dissolve better in cold temperatures. Water motion also helps mix oxygen into the water. Eutrophication can deplete the oxygen concentration in the waterways.
2.7 Culture and Heritage Values The Cultural Impact Assessment (CIA) lodged with this application was prepared in May 2017 as a part of the consultation with Ngai Tuahuriri on the proposed river dredging and other river rehabilitation proposals for the Kaiapoi River.
This application recognises and provides for the relationship of Te Ngai Tuahuriri Runanga and their culture and traditions with their ancestral lands, water, sites, wahi tapu and other taonga including freshwater resources, by requesting Ngai Tuahuriri input on the proposals for river dredging together with some other associated proposals for the Kaiapoi River which will help to mitigate some of the effects of the dredging. The consultation has been provided both through the Cultural Impact Assessment preparation, and via the involvement of Ngai Tuahuriri and Mahaanui Kurataiao Ltd representatives in the Kaiapoi River Rehabilitation Working Party as it developed its concept designs for the river rehabilitation works which complement the proposals in this application.
The CIA explains the existing Ngai Tuahuriri values of the Kaiapoi River and relates these to potential effects of river dredging. It recognises the valued relationship of Ngai Tuahuriri with the river as the mana whenua of/for this rohe (area). It identifies the role of Ngai Tuahuriri as kaitiaki (guardians) and rangatira (decision makers) in terms of protecting values of the Kaiapoi River.
The CIA notes that “water and the resources its supports determine the location of their Kainga (villages), their identity and the rhythm of their lives. The traditional values and controls regarding water are included in Ngai Tahu spiritual beliefs and practices. This recognises and reinforces the absolute importance of water quality in relation to both mahinga kai and hygiene” (p.26).
The CIA recommends potential mitigations during the dredging activities to protect these values, which are described further in the “Description of the Activity” Section. The CIA recognises the ecology, habitat and biodiversity functions of the river and notes the desire of Ngai Tuahuriri to protect their mahinga kai interests. This is particularly recognised in the desire to avoid any dredging activities during the Whitebaiting season from 15 August to 30 November in any year.
The CIA notes that the Kaiapoi River has a long history of use as an “industrial site” and has been identified as having Hazardous Activities and Industries List (HAIL) past usage associated with the former Kaiapoi Wharf. The Council notes that the sediment testing undertaken at the Kaiapoi Wharf indicates a low risk of environmental contamination associated with dredging of the river at this central site. Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 19 Status: FINAL
The CIA describes the key mahinga kai species currently and traditionally consumed from the Kaiapoi River are tuna (eels), inaka (inanga or whitebait), and patiki (flounders) (page 21). Various native bird species present in wetland areas in proximity to the river were also historically eaten or otherwise harvested as they provided other resources of use for Ngai Tuahuriri. These birds (e.g. Pukeko, Putangitangi, Parera and weka) were found in the wetlands around the lower Kaiapoi River.
The mahinga kai habitat within the river requires protection to ensure the abundance and health of these species being harvested. The dredging is considered unlikely to affect any bird habitat on the river margins due to its being undertaken within the river bed, from a barge with dredging of the bed at around or below the low tide line. It will however potentially affect fish habitat.
The CIA notes that the “instream sediment and habitat disturbance will be the largest impacts on habitat during any potential dredging phase of the Kaiapoi River” (p.25). It notes that “suspended sediment can alter water chemistry, increase turbidity and decrease light penetration of the water column, thus reducing primary productivity and affecting the feeding efficiency of some fish species. Tonkin & Taylor’s Kaiapoi River Rehabilitation Stage 1 a report identified sediment mobilisation as an issue that could be managed with the use of appropriate sediment control measures” (p.25). These measures are described further in the “Description of the Activity”.
The CIA states in its discussion about Wahi Taonga (p.17) that “currently there are no previously recorded archaeological sites recorded within the proposed project area”. However it notes the possibility of discovery of new sites. It discusses this in terms of any earthworks that could be undertaken at the 90degree elbow bend, upstream of the proposed dredging reaches. The CIA therefore indicates no particular concern about any of the proposed targeted dredging sites in terms of disturbance of archaeological sites. It does however register a concern about another river rehabilitation project at the elbow bend upstream of the Mandeville footbridge which, if progressed, would be subject to a separate consent application at a later date.
2.8 Kaiapoi River Flow Regimes The Kaiapoi River, within the proposed dredging reaches, is an oversized channel that is significantly larger than that which would be required to convey the design flood flows. Details of the channel characteristics, flood conveyance potential and flow regimes are provided in a number of reports which are summarised in this section.
For instance, a report by Tonkin & Taylor and Dr Henry Hudson, titled “Kaiapoi River Rehabilitation Concept Development Stage 1” states in the Executive Summary that “Hydraulic modelling was undertaken to assess the potential effects of rehabilitation options on the flood routing capacity and sediment mobilisation. The hydraulic modelling (which was undertaken in co-operation with ECan) revealed the following:
• the water level and hydraulic conveyance of the Kaiapoi River is tidally controlled; and
• the existing main channel is significantly larger than required to convey the design flood flows (as a legacy of being the old north branch of the Waimakariri River and river works);”
Although this “Stage 1” report refers to the river reaches above the Mandeville Bridge, the comments are relevant to the dredging reaches downstream of the Stage 1, which are similarly oversized. That report assessed three options which were:
Option 1: Alternate planting of the river banks to meander the channel and direct flow into a low flow channel, without any dredging or physical channel works;
Option 2: Excavating a meandering low flow channel and depositing the dredged material by alternatively building out, stabilising and planting of the banks to meander the channel; or
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 20 Status: FINAL Option 3: Developing a multi-stage channel with options to include sediment traps, treatment and linear wetlands, bank reshaping and riparian enhancement in the mainstem as a part of the concept design.
The analysis of these options is discussed in the Section on “Consideration of Alternatives”. This explains the approach adopted to rehabilitate the upper Kaiapoi River. It identifies how these concepts can also be applied, in part, to the proposals for dredging in the lower river.
The report from Greer and Meredith 2016 state that (p.56) “today the Kaiapoi River is an oversized channel, with a tidal zone that passes through the middle of Kaiapoi, a town that prides itself on the title of “River Town”.
“Kaiapoi has a long history of both utilising the river for transport and storm water, and addressing environmental issues associated with industry…. The current emphasis is on understanding the river system and improving both the habitat and water quality to enhance its value as a ‘selling point’ for the town of Kaiapoi.
The challenge in managing and improving the Kaiapoi River is that it behaves like a tidal coastal lagoon, or lake, with long water residence time and interactions with the Waimakariri River, both in terms of tidal inundation from the sea and inundation with backflows of Waimakariri River floodwater”.
2.9 Groundwater Environment and Hydrogeological Setting The Kaiapoi township adjacent to the river to the north is generally situated at about 1m to 2m (RL) (e.g. above sea level) as shown by LIDAR recordings through the town centre adjacent to the river. To the south, the land generally sits at around 1.5m to 2.5m above sea level. The stop bank top elevation as shown by the LIDAR appears to sit at about 3.5m RL. Moving inland (to the west) the ground elevation gradually increases to about 3.5 to 4m above sea level at the Silverstream subdivision.
The town is protected by the Kaiapoi River stopbanks from flooding from both the Waimakariri River back-flow and from rainfall entering the Kaiapoi River tributaries from its upstream catchment.
Groundwater through the centre of the town is found at about 1m below the ground surface.
The Kaiapoi groundwater is part of the coastal confined gravel aquifer system, in the area of the proposed dredging. Ground conditions beneath the river and surrounding land indicate grey river alluvium comprising gravel, sand and silt. Opus, during its contaminated soil investigation in 2017 drilled two boreholes as part of its geotechnical investigations and 3 boreholes as a part of its contamination investigation, at the proposed pontoon dredging site. All five bores encountered very soft organic clayey silt that is likely to be from siltation in the river channel. The thickness of the siltation encountered in the five bore holes ranged from 600mm to 1400mm beyond which were interbedded layers of gravel and sand (Opus 2017, p.4).
The river bed was also surveyed in four locations as part of the contamination and geotechnical investigations undertaken by Opus in May 2017. The cross sections indicate that there is a consistent amount of sediment deposited on the river bed over the entire width of the river. The silt level was found to be in the order of 0.82 m to -2.34m elevation (Opus 2017, p. 4).
The groundwater levels beneath Kaiapoi are illustrated on the Environment Canterbury online GIS (Canterbury map viewer) which shows groundwater depth contour lines and shows that the area of the dredging application overlies a Coastal Confined Gravel Aquifer System.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 21 Status: FINAL 2.10 Existing Land Use
The area adjoining the proposed dredging reaches in Kaiapoi downstream of the Williams Street bridge comprises a Business 1 zone around the William Street bridge wharf and pontoon development area. Within the Business 1 Zone, commercial premises are established or are being redeveloped following the earthquake sequence.
There is also a Regeneration Zone in place of the former Residential 2 zone, which comprises the previously classified “Red Zone” land in Kaiapoi which was significantly damaged in the 2010/ 2011 Canterbury earthquake sequence.
A foreshore reserve immediately adjoins the proposed dredging areas on both banks between the Williams Street Bridge and the Courtenay Confluence. From the Courtenay confluence downstream the river surrounds become more naturalised with wetland areas along both banks extending to the confluence with the Waimakariri River.
Work has been progressing at the Kaiapoi Marine Precinct and wharf area since March 2016. Works completed to date include the deconstruction of the old wharf, wharf shed, railway platform and MV Tuhoe wharf, and strengthening of the remaining wharf. New rock revetments (embankments) have also been constructed in place of the removed structures, along with repairs and realignment of the stopbanks by ECan (Opus 2017, p.6).
3 Description of the Activity
3.1 Proposed Pontoon Design Features and Constraints
The Riverview Pontoon (Pontoon 1) is a nominal 110 m long, providing short to long term berthing of vessels in the town centre. This pontoon has a nominal 2m wide deck, with jetty/bank-seat and ramped gangway access at each end, with kick rails and service pillars for moored vessels, along with low level deck lighting for wayfinding. The berthing basin/pocket depth varies along the upstream length of the pontoon, due to its proximity to the Williams Street Bridge, as agreed in the feasibility stage definition. This is to avoid deep dredging from undermining the bridge piers and abutments, both of which have relatively shallow foundations.
The pontoon position is set off the wall, with the berthing face approximately 4m off the new river wall face. This is done to maximise the pontoon length whilst allowing the gangways to move up and down with the expected tidal and flood height range without clashing with the pontoon. This also allows for the optimal placement of the gangway access in the centre of the Riverview Terraces where the main stairs terminate and where the deck is widest, providing the best access.
The Boat Ramp Pontoon (Pontoon 2) provides short term parking only, for launching and retrieval of boats up to 6 metres, and is un-serviced. Area lighting is provided only via spill-lighting from the adjacent wharf area lighting.
Both pontoons will accommodate mooring cleats, fender rails, and safety devices and signage. Both pontoons would be permanently open to the public, with no gated access. Safety access ladders will be included at the Riverview Pontoon, on both sides of the Pontoon.
Both pontoons are proposed to have timber decks, with supporting structures on top of the floating modules. Options for floating modules vary and may include many types of proprietary plastic pontoon modules, plastic pipe and mussel buoy options, concrete modules, steel or aluminium (actual pontoon construction details will be confirmed through the detailed design).
The Riverview Pontoon and associated dredging allows for berthed vessels with up to 1.8m draught to avoid touching the bottom of the dredged basin, for the majority of the pontoon berthing length.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 22 Status: FINAL Both the Riverview Pontoon and Boat Ramp pontoon will be anchored to steel piles in the river bed. Approximately 17 piles will be required (14 for the Riverview Pontoon and three for the Boat Ramp Pontoon). The piles will be driven into the riverbed approximately 2m from the seawall, to a nominal depth of 8m (below the existing riverbed). The piles will extend up to 4m above the existing river bed. The pontoons will be attached to the piles via fixings which enable them to move up and down the pile in response to the expected tidal and flood height range. The pontoons will be anchored to the piles to avoid them detaching in up to a 1 in 450 year flood event.
Debris deflectors are proposed to be included in the pontoon design, to limit chances for debris washed down the river during flood events from snagging on the pontoons or accumulating behind them. It will not be possible to completely eliminate the risk of debris accumulation, which will be an ongoing routine maintenance requirement.
The design basis for the pontoons and associated dredging is based on guidelines from the applicable normative design standard which is AS 3962 – 2001: Guidelines for design of marinas, and other relevant standards.
It is considered that the proposed pontoons will provide much improved public access to the river for those berthing small vessels and significantly improve the amenity and appearance of the river channel in the town centre.
3.2 Proposed Dredging Excavation Spoil Quantities
Rough order excavation estimates have been provided for establishment of the floating pontoons to indicate likely spoil volumes to be abstracted.
The table indicates rough excavation estimates could be between 5,000 – 6,000m3 of spoil from the area around the wharf. An additional 2-3,000 m3 could also be required in future years to provide for some maintenance dredging.
It is noted there is considerable uncertainty in actual volumes which will be extracted.
Table 4: Floating Pontoons Berthing and Docking Space
Site Average Depth of Average Width to Length of Excavated Estimated Spoil Excavation (m) Excavate (m) Area (m) Volume (m3) Pontoon 1 0.98 32 162 5100 Riverview Pontoon (Williams St Bridge to wharf)
Pontoon 2 0.32 33 85 900 Boat Ramp Pontoon (wharf to Coastguard Launch Ramp)
Total Estimated 6,000 Spoil Volume
3.3 Historic Dredging of the Kaiapoi River The Kaiapoi River was previously dredged in the 1970’s using a dragline dredge owned by Environment Canterbury. This is further referenced in the report by Jacobs “Dredging Feasibility Report: Heathcote River Floodplain Management Plan”, October 2017, which stated “early dredging operations used a pneumatic sweeper. This disturbed silt on the bed of the river and the flow of water would then carry the sediment downstream. The CDB also owned and operated dragline dredges which were rotated around the main rivers. These were used up until 1989. Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 23 Status: FINAL
The dragline is a versatile machine that has the longest reach of any member of the crane-shovel family. It can dig in soft to medium-hard material. The bucket teeth and weight of the bucket produce the digging action as the drag cable pulls the bucket across the river bottom.
Issues with the drag line include lack of lateral control and it does not have a positive digging action. As a result the bucket may bounce or move sideways during dredging. Also the bucket is more likely to spill material and create larger sediment plumes…” (Jacobs 2017, Appendix C).
From this description it is clear that the dragline method is not a preferred environmental dredging method and its use now appears to be discontinued. The Environment Canterbury dragline is currently broken and no replacement is intended. The most recent recorded dredging in the Kaiapoi River was the dredging of the former MV Tuhoe berth in 2008, which used dragline/clamshell method, and disposed of the dredge arisings on the Corcoran Reserve. Prior to these dredging activities, it is likely that the volumes of vessel movements in the wharf area when this was an operating port would have had the effect of regularly suspending and mobilising/dispersing the soft sediments in the lower reaches of the river.
3.4 Proposed Dredging Method
There are three available dredging methods which could be used in the Kaiapoi River. The first option is use of a long reach digger (backhoe dredge) operated from the river banks. The second option is a long reach digger operated from a barge. The third is the use of a suction dredge on a barge. All three options are discussed further in this section, with risks and benefits considered.
3.4.1 Long Reach Digger (Backhoe Dredge) from River Banks
The long reach digger (backhoe dredge) being operated from the stopbanks is not recommended by Environment Canterbury due to the risk of damaging the stopbanks or lower banks due to the heavy weight of a digger damaging the bank structure and integrity.
The stopbank integrity is vital to the flood protection provided for Kaiapoi township. These structures are known to be extremely susceptible to damage from heavy track laying machinery such as draglines or diggers. Use of a digger on any stopbank has therefore been discounted due to the risks to stopbank stability.
However, in the case of the proposed pontoon dredging operation, there remains at the current time, potential to locate a long reach digger on the river bank immediately in front of the section of stop bank that still requires reconstruction. Care would need to be taken to ensure the concrete retaining wall along the river bank is not damaged during dredging or load-out operations by excavator track frames exerting extreme point loading on the concrete or directional weight thrust toward the river.
This option has therefore been discounted due to its risks to the stability of the concrete retaining wall and the very limited timeframe which would be available to use this area prior to stop bank reconstruction works commencing.
3.4.2 Long Reach Digger (Backhoe Dredge) from Barge
The backhoe dredge is able to be operated on a barge, directly digging spoil from the river bed and depositing it on the nearby river banks or on the barge for dewatering. This is considered to be a cost effective dredging option and was therefore investigated further as a part of this application.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 24 Status: FINAL This option has some associated health and safety concerns and requirement to stabilise the barge in the river channel. The health and safety concerns involve ensuring the barge is seaworthy and “fit for purpose” and operated by trained and experienced operators. The barge would also need to have adequate capacity to convey the excavated spoil to the dewatering location. Barge stability issues would need to be managed so as to accommodate the changing excavator swing radius.
The barge also creates a risk of wave lap damage to the lower banks due to the plunging motion of the excavator bucket and possible barge movement during spoil loading.
Other factors are whether the river bank anchor points provide adequate strength needed to anchor the barge. There is also a requirement to maintain adequate clearance from trees and other structures on the banks whilst dredging, particularly in the town centre area.
It is considered that these factors would be able to be addressed by the contractor’s health and safety provisions for barge operations, including use of spuds to stabilise the barge within the river bed, reducing any rolling risk and reducing potential wave lap damage.
This option has not been selected in this application primarily due to the risk of ripping up the river bed and releasing large volumes of sediment into the water column whilst dredging, which is considered to have more adverse environmental impacts than the alternative suction dredge method.
3.4.3 Suction Dredge
The selected excavation method for use in the Kaiapoi River is hydraulic suction dredge with pump, mounted on pontoon. The feasibility of this method depends on the success of spoil dewatering and ability to reuse spoil within the Regeneration Zone and / or on other nearby sites.
An option proposed in this application is use of hydraulic cutterhead pipeline dredge, with the cutterhead option proposed due to the possibility that gravel will be encountered during dredging to establish the pontoons.
Suction dredges work by sucking a mixture of dredged material and water from the channel bottom. The amount of water “sucked up” with the material is controlled to make the best mixture for efficient option of the dredge. The suction dredge enables excavation and removal of material hydraulically, direct to the spoil dewatering area, without requiring any rehandling.
A cutterhead is a mechanical device that has rotating blades or teeth to break up or loosen the bottom material so that it can be sucked through the dredge. This means that if gravel is encountered during dredging then the dredge will be able to break apart and loosen the material without damage or clogging of the suction head.
Some cutterheads are rugged enough than they can break up rock for removal. Pipeline dredges are mounted (fastened) to barges and are not usually self-powered, but are towed to the dredging site and secured in place by special anchor piling, called “spuds”. Cutterhead pipeline dredges work best in large areas with deep shoals, where the cutterhead is buried in the bottom sediment. Water pumped with the dredged material must be contained in the disposal site (spoil dewatering) until the solids settle out. Abstracted water is then usually discharged back into the waterway.
This method of dredging is not suitable in areas where sediments are contaminated with chemicals that would dissolve in the dredging water and be spread in the environment during discharge. However, Kaiapoi River bed sediment has been tested and shown to not be contaminated (see section 2 description of the Environment for the results of sediment contaminant testing).
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 25 Status: FINAL Because the discharge line for pipeline dredges is usually floated on top of the water the operation requires a still water surface (i.e. minimal wave action) which is the case for the Kaiapoi River. Navigation between the barge and shore will be prevented during dredging operation so that vessels on the river do not interfere with the discharge line.
If there is a lot of debris in the dredging site, the pumps can clog and impair efficiency. During dredging operations the Council will request the on-site support of the Coastguard or other river maintenance contractor, who will be requested to assist to identify and remove any large debris (e.g. logs captured on the river bed) immediately prior to dredging of each site, if required.
The cutter head system incorporates rotation of the shaft and cutter, which agitates soft or loose material and cuts through hard material, which is then collected by the suction. The suction hose is attached to a ladder which is supported by an “A” frame with hoisting equipment to raise and lower the ladder to the targeted dredging location on the river bed. Adaption of the hull, ladder and spud extensions for various digging depths provide for flexible dredging at a range of depths and tidal environments.
If the dredging operation encounters gravel or rock these materials may be able to be removed by the cutter suction dredge and deposited with the spoil for final disposal. Cutter-suction dredges are most often used in geological areas consisting of hard surface materials (for example gravel deposits) where a standard suction dredger would be ineffective. This means the cutter suction dredge may be able to remove any gravel or rock in addition to the soft sediments encountered on the river bed.
However, the dredge pump may not be sufficient to convey heavy gravels with the dewatering water to the dewatering area over a long distance. Any large area of river bed gravels may need to be separately abstracted by use of a digger on a barge.
The below diagram indicates the general form of a cutterhead suction dredge.
Source: https://www.google.co.nz/search?q=cutter+head+dredge&tbm=isch&source=iu&ictx=1&fir=POxdiYPAUOGzRM%253 A%252CGB- KrApRJmK_gM%252C_&usg=__zX67tq0tIHFJWDgoVVBBtnz8_4g%3D&sa=X&ved=0ahUKEwjK8ce178TZAhVKE7wKHQa _DOUQ9QEINDAA#imgrc=QK9uWfNtOR_lhM:&spf=1519692525316
Reference: google images search (see above link).
Spoil is conveyed via the suction hose, together with large volumes of river water, into the intake pipe, and then pushed out through the discharge pipeline directly to the disposal site. Because pipeline dredges can pump directly to the disposal site (e.g. for spoil dewatering), they operate continuously and can be very cost efficient.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 26 Status: FINAL A suction dredge is considered a good environmental method of dredging, for the following reasons:
• The suction dredge would lift sediment from the bed onto land and release minimal sediment into the river water column, unlike the backhoe dredge (digger bucket).
• A suction pump has more control than the dragline or long reach digger methods in terms of precise sediment relocation
• Creates a smoother profile and channel finish in the river bed, which fits with the intent of the project to create a smooth river bed base upon which to float pontoons and smoothing out existing river bed high points
• This method is likely to enable precise sediment removal that would reduce damage to fish and invertebrate habitat, in comparison with the backhoe dredge.
It is understood that the long reach digger (backhoe dredge) option could cause more contaminant disturbance due to the continual motion of the excavator bucket in and out of the water. However, the cutterhead dredge will produce turbidity because of the cutterhead motion of breaking down the material before it is pumped. The cutterhead dredging option also abstracts more water than other options, requiring more dewatering during dredging.
The “Dredging Feasibility Report for the Heathcote River Floodplain Management Plan”, October 2017, prepared by Jacobs for the Christchurch City Council” states: “The cutter head dredge is a hydraulic suction pipeline with a rotating cutter head attached to the suction intake to mechanically assist in the excavation of consolidated material. Cutter head blades are designed to direct loosened material efficiently toward the suction intake. Efficient operation of a cutter head dredge and minimisation of sediment resuspension can be achieved by proper dredge design and operation. The intake velocity of the suction mouth must be sufficient to remove all of the material excavated by the cutter head blades, or the excess material will enter the water column.
The issue with this type of dredging is that the rotating cutter head re-suspends sediment which can be an issue when dredging contaminated sediment. Further, it increases the amount of dewatering of extracted sediment required, when compared with other methods. Cutterhead suction dredges can be expensive to operate and are mainly used in areas when large quantities of sediment need to be dredged”.
It is understood to be unlikely that fish would enter the dredge suction pipe mouth due to the noise, vibration and disturbance of the river bed during the dredging activity. The disturbance of the river bed will provide an early warning system for fish present in the dredging reaches of the pending disturbance and trigger the “flight” response. This should ensure minimum impact on fish present in the river from the dredging. However eels inhabiting the river bed sediments may not be able to escape the suction dredge mouth action. This is discussed further in the AEE.
3.5 Timing of Dredging and Piling Activities
The dredging activities proposed in this consent would ideally be undertaken any year in the period from 1 June to 15 August or in December of any year. Due to known inanga spawning in the lower Kaiapoi River, this will avoid interference with any inanga spawning sites and hatched fish re-entering the channel during the spawning period. Inanga are understood to spawn within vegetation on the lower river margins from the period 1 January to 1 June.
It is also proposed to avoid interference with whitebaiting, as requested in the Cultural Impact Assessment, by avoiding dredging during the fishing season between 15 August and 30 November.
AEL in 2017 (p.24) note that “in the autumn, inanga eggs are deposited, and settle, in the grassy intertidal zone during the spring tide sequence”…. “Inanga rely on rank vegetation to maintain a layer of humid air around the eggs so they can develop”. The dredging will be of the permanently wetted river bed below the low tide mark, adjacent to a concrete wall or rock revetment. It will not directly disturb any inanga spawning site as the dredging area has no riparian vegetation and is highly modified. In addition, any spawning sites are located above the dredging area on the intertidal, Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 27 Status: FINAL grassed edges of the river. Inanga spawning areas are understood to be located above the low tide and so will not be disturbed by the dredging.
The dredging activity is proposed to be undertaken in the June-August period, or alternately the December period. Dredging operations will need to take account of seasonal fluctuations in the salinity levels of the water in the Kaiapoi River. Research to date suggests that river salinity is likely to be highest during the summer months. Further research is required in order to validate these suspected patterns (i.e. over more than one year); however given the advice to date the preference if possible is to dredge in winter, with December to provide a potential reserve option for dredging.
The piling activity (for the pontoons) proposed in this consent would be undertaken between 1 June and 15 August 2018 to avoid interference with inanga spawning. It is proposed to undertake the installation of the pontoon piles immediately following the river wall (north bank) upgrades currently underway.
3.6 Contaminant Management
The wharf pontoon placement requires deep dredging to approximately 2.3m below the current bed surface. The sediment in this area has been comprehensively tested and is known to carry a low environmental risk of contamination as shown by the 2017 comprehensive sediment testing. Therefore the environmental risks from dredging at this site should be low.
3.7 Dewatering of Spoil The cutterhead section dredge method enables excavation and removal of material hydraulically to identified spoil dewatering areas on the river bank adjacent to the barge/dredge operations. This can potentially be undertaken without requiring any spoil rehandling if spoil is pumped directly to the final disposal site. However, it is understood that the suction dredge method requires dewatering of spoil as closely as possible to the dredging abstraction location in order to minimise pumping distances and potential blockages in the discharge line.
3.7.1 Spoil Dewatering and Disposal to Land
Spoil dewatering is intended to be undertaken with the intent to dispose of spoil to land. The preferred method is to deposit spoil into sediment control ponds or geotextile dewatering bags so that spoil is contained whilst it is being dewatered. The separation of spoil and water may require addition of a flocculent.
The site/s identified for the first stage of spoil dewatering would involve a settlement facility/s and treatment process. A second stage storage and temporary stockpile area is also envisaged, which may also achieve additional drying of material prior to final disposal. The method for spoil dewatering and stockpiling is described in outline form in this application. Details, including actual sizing, form and configuration of the settlement and treatment facility/s will need to be developed through discussion with the contractor at the detailed design stage in coming weeks and can be confirmed through the consent conditions, prior to the issue of the consent. This approach enables an indicative dewatering and stockpiling method to be consented to meet specified performance standards, whilst allowing the actual settlement pond and treatment sizing dimensions to be designed to fit the pumping and sizing specifications of the rig to be deployed in the river.
Dewatering would be likely undertaken in two stages, described as follows:
Stage 1:
A first stage containment area / settlement pond would be intended to fit within the contour of the existing ground levels at either/both of the Corcoran and Askeaton Reserves. The containment area would be constrained by the
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 28 Status: FINAL stopbank on one side (at the Corcoran Reserve) and surrounded by a raised bund on other sides (for both reserves). The dewatering areas would be sized and constructed as required to contain the settlement and treatment processes, which may include geotextile dewatering bags and potentially, addition of a flocculent to aid settlement. Most of the dewatering of spoil would be undertaken within Stage 1 so that spoil is ready for final disposal, as far as is practicable at completion of the process, although some additional drying of material may also be required in Stage 2.
Any surrounding bund will likely be raised to be a minimum of 1m in height, lined with a 1.5mm HDPE Liner. The liner will be seam sealed and cover the raised bunded sides of the excavated, lay down containment area to ensure all dewatering water is conveyed to the dewatering pond collection point. Water will be returned to the river using a collection point and pump.
The lay down area will provide a fully contained spoil dewatering system, including a fully sealed dewatering pond with liner and sealed pipes/ conveyance channels that will prevent leakage of dewatering water onto the surrounding land.
This method should reduce the risk of any saline content entrained in the dewatering water from affecting surrounding land.
The base of the dewatering basin will be sealed with a layer of geotextile cloth and be layered with drainage metal. This stops the bags moving (if geotextile dewatering bags are used) whilst they are filling, and lets the underside of the bag decant properly which helps with the dewatering process.
The discharge pipe (from the barge) will float along the surface of the water and be placed over the stopbank (at Corcoran Reserve) or over the lower river bank (at the Askeaton Reserve) to discharge to the dewatering site/s. The pipe on any land surface will be protected with appropriate erosion control material to reduce friction from movement against the land surface and reduce the likelihood of pipe bursts.
Dewatered, filtered water is then discharged via a pipe system back to the river by being passed through a specially built pumping chamber fitted with submersible pump on an automatic stop/start system, at the collection point.
In addition, erosion control geotextile mats will be placed around the dewatering area and around the collection point, to avoid erosion of the lower banks and mud flats if any water should escape from the collection point drainage system during dewatering.
At the commencement of dredging at any new location, a clean river water test will be completed to test all pipework for leaks and possible problems before any spoil is transferred to the dewatering area. The spoil and water is conveyed to a “distribution manifold” which allows the operator to change bags or discharge point at the dewatering area without the need to stop dredging. If using geotextile bags, this approach will improve efficiency toward the end of dredging when multiple bags need topping up. Each bag is then filled with spoil and water through one of the filling ports, then left to drain down whilst filling another bag.
If geotextile bags are utilised, complete dewatering of each bag could take up to 1 year to complete. Following the Stage 1 dewatering, the dewatering bags can be cut open to enable final disposal of dewatering spoil at another location. The geotextile bags will in any case break down over time.
The pumping rate of dewatering during dredging is estimated to be within a range of 40-60 L/s. It is anticipated that the discharge of dewatering water back to the river will be initially at a somewhat reduced rate (approximately 20- 40L/s), with the dewatering discharge rate gradually reducing following the initial stages, but continuing over a period of time of up to 1 year.
Stage 2:
Following initial dewatering, spoil from the sediment control ponds will be excavated out, or if geotextile bags are used, these will be ripped open and spoil conveyed to a longer term drying and storage site, likely to be located within the Regeneration Zone. Alternately spoil may be used to build up slumped land at the Askeaton Reserve and retained at this site in the long term. At this stage, spoil will be retested for saline content and other contaminants to determine its handling and suitable potential final uses. Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 29 Status: FINAL
The second stage drying and storage site may need to provide long term storage of spoil, prior to any decisions on final use. Excavation of the site is not likely to be required and spoil, depending on its condition, may be spread out across the land and left open to air to aid evaporation and complete the drying process. Spoil may be hydroseeded for erosion control and amenity purposes until a final reuse option is determined.
The indicative location of the initial contained dewatering pond and longer term open dewatering and storage area for the proposed dredging to establish the floating pontoon base is included in Appendix D.
3.7.2 Potential Spoil Dewatering Locations
The preferred dewatering sites currently being investigated for use for the pontoon dredging are on the river banks on the outside of the stopbanks within the Corcoran Reserve or alternatively, on the Askeaton Reserve where slumped land requires lifting (locations shown in Appendix D).
These two preferred dewatering sites are indicative, and will be confirmed subject to the ability to develop a feasible dewatering and treatment option with the contractor, given the anticipated water volumes, available land and timetable and programme constraints.
Pumping from the initial (stage 1) dewatering area/s will be designed to convey dewatering water from the collection point and return it to the river, following filtration through sediment control ponds with added treatment, or geotextile bags.
The potential Stage 1 spoil dewatering locations (see Appendix D) are: • Corcoran reserve – the eastern end by the old Charles St pumping station near the end of Jollie St / Charles St. This area was built up many years ago by dredge spoil, and also had wastewater overflows immediately after the earthquakes. Use of this site could possibly make use of an existing stormwater pump-station and outfall. • Askeaton reserve – land that slumped during the earthquakes can be built up using dredged spoil.
Alternative spoil dewatering options are: • Kaiapoi East Regeneration Area – close to the potential end-use of the material, but further from the river. Use of this site would create potential risks of the dredge discharge pipe blocking or bursting as spoil would be required to be pumped for long distances. The site could be viable provided a large enough clear area is available to build bunds/ponds, and pump back to the river (both Stage 1 dewatering and Stage 2 final drying, storage and then final disposal would be provided at the one site). • Kaiapoi South Regeneration Area – low lying – has existing drainage, no planned regeneration works there for a while – but is remote from the area where we need the immediate fill, and would require transport via the town centre (potential dewatering and long term disposal site). For these reasons this is not currently a preferred option.
3.7.3 Spoil Reuse Constraints
There is a net requirement for earth fill in the planned development of the adjacent regeneration areas; so beneficial re-use of the dredge spoil is the preferred approach. Potential uses of fill in general include filling of low points (e.g. where roads will soon be removed) or other areas needing raising due to current drainage issues. Fill is also required in order to re-counter the land to achieve the new drainage principles in the proposed sports and recreation areas, and the rural areas in Kaiapoi East. There is also potential need for fill in later stages of regeneration area development for creation of natural amphitheatres and spectator embankments.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 30 Status: FINAL The final disposal of spoil to land will need to consider a number of constraints. These include engineering properties of the spoil, any contamination (though shown in this application to be unlikely), and effect of salinity entrained within spoil on proposed future landuse. These issues are being considered further in the detailed dewatering of spoil design.
Spoil may be able to be used as capping or fill layers where the spoil is encapsulated deep under other fill to enable use of topsoil for future productive land use purposes, if required. There is an alternative view that spoil with a saline content will minimise long term weed growth and could be desirable fill at a number of locations in the Regeneration Zone, including for the sports field or BMX construction.
3.8 Cultural Input
The CIA lodged with this application recognises the aspiration of Ngai Tuahuriri to find methods to avoid discharge of contaminants into the river water and avoid damage to habitat whilst dredging within the river.
The CIA noted specific concern with operation of long reach excavators during dredging which potentially result in contaminants such as oil, grease and fuel being deposited within the intertidal zone and mobilised in runoff to enter the Kaiapoi River (p.25). This application addresses that concern by proposing use of a suction dredge in the river which should have less disturbance of sediment and effect on habitat than would a long reach excavator. It also notes the sediment contamination testing described in Section 2, which indicates a low risk of environmental contamination associated with the works.
The CIA notes that, to prevent silt and sediment from disbursing through the river during dredging, best practice sediment control measures need to be followed. These include a suitable Erosion and Sediment Control Plan and Environmental Management Plan (e.g. a Silt and Sediment Control Plan) to be prepared that are consistent with the objectives and policies contained in Section 5.3 of the Mahaanui Iwi Management Plan. The CIA recommends these would be developed by the contractor and approved by Environment Canterbury and the Waimakariri District Council.
These best practice measures should include:
• All vehicle refuelling and maintenance should occur in areas away from the waterways and a spill response protocol should be compiled. • The use of floating sediment curtains, silt screens or other suitable containment methods to prevent suspended silt or sediments that are disturbed during dredging activities being released into the Kaiapoi River. • To prevent sediment entering waterways, all areas within the project area that are subject to disturbance need to be re-vegetated as soon as possible once construction has ceased to reduce the time bare earth is exposed to the elements • For sloping areas near waterways, use of suitable ground and soil erosion cover options to reduce erosion and sediment input while vegetation is becoming established.
The CIA recommends Council deploy a number of specific sediment control measures during dredging of the proposed sediment trap upstream of the proposed dredging reaches. Although this is a different project not covered in this application, some of the proposed methods would also usefully be applied to the proposed dredging reaches for floating pontoons. These could include a combination of the following actions and considerations (with some staff comments added to explain how these actions would be applied):
• Screening of any sensitive habitats on the river margins with a boom and silt control fence • Screening in the channel around the barge to contain any sediment within the area being excavated (which can be subsequently released during a period of high flows when there is higher background turbidity in the river and therefore less localised impact of releasing a sediment plume) Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 31 Status: FINAL • The dewatering stockpile area will have a staked silt fence, weighted with sediment bags, around the base to prevent flux of dirty water back to the river • The stockpile site, and onsite fill areas, will be levelled and hydro-seeded as soon as works are complete
The CIA also proposes dredging avoid the whitebait fishing season from 15 August to 30 November in any year.
It proposes that a suitably qualified archaeologist approved by Pouhere Taonga Heritage New Zealand be onsite to monitor earthworks and the removal of soil down to a level considered by the archaeologist to be below the ground level present during pre-European occupation. This archaeologist would be supported by a Cultural Monitor to monitor disturbance of topsoil.
Notwithstanding this CIA recommendation, this application takes the view that, as the current Kaiapoi River bed was channelised in the 1930’s (during European occupation) the river bed itself is not considered an archaeological site in terms of the proposed dredging activities or in terms of any other Heritage New Zealand requirement. It is suggested that providing a Cultural Monitor rather than an Archaeologist to monitor works is a more suitable mitigation to manage any cultural impacts of the dredging. For instance, any impacts are more likely to be associated with disturbance of habitat than disturbance of archaeological sites (with regards to the proposed in–channel river bed dredging components of the wider river rehabilitation work programme).
Nonetheless, if a new archaeological site was discovered during dredging in the river bed then the Accidental Discovery Protocol would apply. However, the Protocol would not be able to applied when suction dredging as there will be no clear view of the riverbed during the activity.
The CIA proposes “adoption and implementation of a planting plan that enhances bio-diversity and in stream values utilising those taonga plant species that would naturally occur within the project area”. This is being undertaken through the aquatic intertidal planting programme which is an ongoing project of the Kaiapoi River Rehabilitation Working Party and is undertaken as an activity to complement the dredging. The planting will improve habitat on the river margins and consequently will assist to offset potential adverse effects of the proposed dredging. The planting is also intended to narrow, constrain and meander the river channel, trapping and treating suspended sediment in the water column within linear wetlands on the margins.
The Council is proposing sediment control measures for use in the river which are generally in line with the CIA recommendations in the section on “Proposed Sediment Management”. These measures also include discussion on options to identify and avoid saline intrusion of the water column during the dredging operation, which is not specifically discussed in the CIA.
It is proposed to invite Ngai Tuahuriri to provide a Cultural Monitor to oversee the commencement of dredging at each targeted dredging location. The Cultural Monitor would be invited to be present to observe operations for at least the first two hours of dredging at each separate location, following commencement. The Cultural Monitor could have input into the set-up of sediment control measures undertaken during the dredging.
3.9 Ongoing Maintenance Dredging The Council proposes to continually monitor the condition of the river bed around the floating pontoons and vessel docking areas in conjunction with the Coastguard. As a part of the consent, it will undertake further maintenance dredging around the base of the pontoons, as and when required to maintain access for docking.
There is potential for the dewatering area to be used a number of times over for ongoing maintenance dredging, depending on the required frequency/interval of maintenance dredging.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 32 Status: FINAL 3.10 Proposed Sediment Management As the tide will convey sediment both up and downstream of the dredging operation within 6 hours of commencement of dredging (at any point in time), usual methods of sediment control that provide protection at just either an upstream or downstream direction may not be effective in the Kaiapoi River.
Erosion and Sediment Control methods will need to be closely managed at the suction pipe head to ensure it can effectively extract sediment with minimal release into the current. Some cutterhead dredges are equipped with a mud protection shield or turbidity shroud surrounding the rotating guard which limits any chance of sediment being released into the water column at the cutterhead. This will be investigated through the dredge detailed design and be considered in the Erosion and Sediment Control Plan required from the selected contractor.
The dredging contractor will be required to prepare an Erosion and Sediment Control Plan which will detail the methods to manage the extraction, dewatering and transport of sediment to minimise release back into the river or surrounding land. This will be required to be certified by Environment Canterbury prior to the commencement of the dredging and dewatering in accordance with the Erosion and Sediment Control Toolbox for Canterbury.
Measures which could also be deployed include using silt fences or other similar sediment control devices in the channel around the suction dredge, to contain sediment within the area being excavated. In line with the recommendations of the CIA, any sediment constrained within the silt fence during dredging could be released at a time of higher flows so that any residual sediment plume would be released into the river at a time when higher background plumes are also occurring.
It is also possible that silt fences could be placed to screen off any sensitive habitats near the dredging areas, to provide more site specific protection.
The silt fence/s and other devices are proposed to be located at the commencement of the dredging works in consultation with the Environment Canterbury compliance officer/s, Department of Conservation observer or any Cultural Monitor appointed to observe the dredging by Mahaanui Kurataiao on behalf of Ngai Tuahuriri.
The Council will use a combination of quick visual turbidity reference sampling and clarity tube sampling to investigate any effect of sediment release within the water column immediately following commencement of the dredging operation.
For the turbidity sample a container of river water will be collected prior to dredging and a spare container maintained on the barge for use at commencement. Following commencement the empty container will be filled with river water in any area of visible turbidity and suspended sediment levels will be compared and may be reviewed by any observer on site from Environment Canterbury, Department of Conservation or Ngai Tuahuriri. Photographs can also be sent to the compliance officer.
The Contractor will be requested to assess any turbidity release within the river by measuring the visual clarity with a clarity tube both immediately upstream and 10 metres downstream of the pontoon, in relation to the tidal direction at the time of dredging. The two samples shall be compared and the absolute percentage change in clarity between the two samples will be recorded.
If the reduction in water clarity (from comparing two clarity tube samples) is greater than 20%, this would be a trigger to temporarily cease operation, if requested by the Environment Canterbury compliance officer, and review suction dredge “cutter head” operation and method of placement of the suction pipe on the river bed. The 20% standard may not be achievable at all times and discretion will be sought to continue operations, if during the dredging, no further best practice methods are able to be implemented.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 33 Status: FINAL 4 Reasons for Application
4.1 Resource Management Act 1991 The Resource Management Act 1991 (RMA) provides the framework for all resource use in New Zealand. The overriding purpose of the RMA is “to promote the sustainable management of natural and physical resources” (s.5, RMA). The broader principles (s.6 to s.8) are a guide to considerations of any resource consent, development or protection. Of particular relevance to this application:
Section 5 sets out the overall purpose of the RMA which is to promote the sustainable management of natural and physical resources. Sustainable management is defined in section 5(2) and includes managing the development of natural and physical resources in a way that enables people and communities to provide for their economic, social and cultural well-being and for their health and safety while inter alia avoiding, remedying or mitigating adverse effects.
The proposal is considered to meet the purpose of the RMA as it enables the WDC to achieve economic and social development in Kaiapoi town by increasing use of the redeveloped wharf through providing new floating pontoons to facilitate easy, safe public access to the river.
Section 6 states that:
In achieving the purpose of this Act, all persons exercising functions and powers under it, in relation to managing the use, development, and protection of natural and physical resources, shall recognise and provide for the following matters of national importance:
(a) the preservation of the natural character of … rivers and their margins, and the protection of them from inappropriate subdivision, use and development: (b) the protection of outstanding natural features and landscapes for inappropriate subdivision, use and development: (c) the protection of areas of significant indigenous vegetation and significant habitats of indigenous fauna. (d) the maintenance and enhancement of public access to and along the coastal marine area, lakes and rivers: (e) the relationship of Maori and their culture and traditions with their ancestral lands, water, sites, waahi tapu and other taonga: (f) the protection of historic heritage from inappropriate subdivision, use and development: (g) the protection of protected customary rights: (h) the management of significant risks from natural hazards.
The Kaiapoi River dredging consent application provides for these matters of national importance as follows. For instance:
Preservation of natural character of rivers and margins: This application does not propose any activity that would adversely interfere with the character of the Kaiapoi River or its margins. The establishment of the pontoons will be the only permanent visible change associated with the dredging and these will be established in already highly modified reaches of the river, where an existing concrete structural wall will be replaced with a new rock revetment and adjoining the redeveloped wharf structure.
Outstanding natural features and landscapes: There are no recognised outstanding natural features or landscapes within the proposed dredging areas on the Kaiapoi River bed.
Significant fauna and indigenous vegetation habitat: The bed and channel of the Kaiapoi River could be considered to currently provide significant habitat in terms of salmon, inanga, eels and (prior to observations of increasing saline intrusion), trout. The dredging is proposed to be undertaken in the period 1 June to 15 August or in December of any year to minimise effects on inanga which are thought to spawn in, and be harvested from areas near the dredging reaches. It is understood that both trout and salmon spawning sites are present in the upper Kaiapoi River, some Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 34 Status: FINAL distance upstream of the proposed dredging reaches. The spawning of these fish is not considered likely to be affected by this application. The habitat of eels resident in the river sediment will be temporarily disturbed during dredging. It is proposed to offset these temporary effects with ongoing intertidal planting to establish new, improved habitat for eels on the river margins.
Public access to rivers: The application provides for continued public access to all areas of the Kaiapoi River following dredging, and during the activities as far as practicable. During dredging some river navigation will be temporarily restricted in vicinity of the barge and the associated sediment control features whilst the pontoons base and surrounding berthing area is deepened. Access will continue to the river as designated, away from these activities.
Maori access to ancestral lands and water: The application protects access of Ngai Tuahuriri to the Kaiapoi River as a mahinga kai resource. In particular, access to fishing for whitebait, eels and other species will be maintained as far as practicable, and enhanced by the aquatic planting programme which is also a part of the river rehabilitation project.
Protection of historic heritage: There are no designated heritage or archaeological sites within the proposed dredging reaches. The dredging is anticipated to have no material effect on any aspect of historic heritage of or within the Kaiapoi River.
Protection of customary rights: these are protected in terms of customary mahinga kai areas for which continued access is maintained in the Kaiapoi River, as noted above. The Cultural Impact Assessment lodged with this application notes customary food gathering activities including harvesting whitebait, eels and flounder. The dredging will potentially temporarily affect the habitat of these species in the river (in particular eels living in the river sediment that may be less able to avoid the dredge suction mouth than the other species). The effects of this are being offset by the intertidal aquatic, point and side bar planting of raupo, schoenoplectus and other aquatic species and complementary terrestrial native planting on the lower river banks including in and around the proposed dredge areas, to improve habitat for fish and birds.
Management of Significant Risks from Natural Hazards:
The application will slightly deepen the Kaiapoi River in a few locations and so have, potentially, a marginal slightly positive effect on flood capacity in the river.
Section 7 states that “In achieving the purpose of this Act, all persons exercising functions and powers under it, in relation to managing the use, development, and protection of natural and physical resources, shall have particular regard to-
(a) Kaitiakitanga: (aa) the ethic of stewardship: (b) the efficient use and development of natural and physical resources: (c) the maintenance and enhancement of amenity values: (d) intrinsic values of ecosystems: (f) maintenance and enhancement of the quality of the environment: (g) any finite characteristics of natural and physical resources: (h) the protection of the habitat of trout and salmon: (i) the effects of climate change:
The Kaiapoi dredging consent application provides for these other matters as follows:
Kaitiakitanga and stewardship:
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 35 Status: FINAL The Cultural Impact Assessment lodged with this application seeks recognition of kaitiakitanga and the interest of Ngai Tuahuriri in the stewardship of natural resources which may be affected by the proposed excavations in the Kaiapoi River. The application meets these aspirations by providing for a cultural monitor to review activities on site at the start of dredging each area which will provide them with input into the use of sediment control measures within the river.
Efficient Use and Development of Natural and Physical Resources
The application will have only temporary effects on the use or development of natural and physical resources. For instance, it does not seek to abstract any groundwater, and proposes a non-consumptive take and return of surface water to the Kaiapoi River during dewatering of dredging spoil. Spoil from the river bed may be able to be reused within the Regeneration Zone as inert material.
Maintain and enhance amenity and quality of environment: This application includes installation of floating pontoons which will improve amenity and environment of the Kaiapoi River, improving appearance of the town centre area adjacent to the wharf and providing an environment more conducive to public access. It notes the planting of the Kaiapoi River margins through the river rehabilitation project which will improve habitat in the river for those species which are temporarily displaced during the dredging.
Intrinsic values of ecosystems:
Within this application the Council will protect the intrinsic values of ecosystems within the Kaiapoi River by adopting a high environmental standard for dredging (using a suction dredge method to minimise discharge of a sediment plume) and deployment of sediment control measures within the river during dredging to protect sensitive habitats as identified by key stakeholders including any Cultural Monitor present during the dredging.
Protect the habitat of trout and salmon:
The Council acknowledges the harmful effect of suspended sediment in the Kaiapoi River in reducing rates of trout spawning in the bed of the river, and potentially affecting the habitat of salmon. This is being addressed by the ongoing aquatic intertidal planting programme, which hopes to establish linear wetlands on the river margins (using salt tolerant plants) which will provide a sediment trapping function as the channel is constrained by the increased margin roughness.
Effects of climate change:
The effects of climate change include sea level rise and potential increased intensity of flood events. Both these may be mitigated to a small extent by the proposed dredging which will marginally increase the river flood carrying capacity (e.g.in the dredging area in the town centre), slightly offsetting higher tidal flows from future sea level rise and catchment flows from more severe, frequent flood events.
Sea level rise will also likely cause future increased saline intrusion in the water column. The intertidal planting programme which is being undertaken as a river rehabilitation project in conjunction with the proposed dredging is seeking to adapt to the saline intrusion by establishing salt tolerant plants on the margins in place of the fresh water macrophytes which have disappeared with the recent increasing salinity.
Section 8 states that:
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 36 Status: FINAL “In achieving the purpose of this Act, all persons exercising functions and powers under it, in relation to managing the use, development, and protection of natural and physical resources, shall take into account the principles of the Treaty of Waitangi (Te Tiriti o Waitangi)”.
The application takes account of the principles of the Treaty of Waitangi through considering and where appropriate and practicable, implementing recommendations which Ngai Tuahuriri made within its Cultural Impact Assessment. The CIA recommendations and Council’s resulting approach are outlined in the attached Description of the Activity, which includes a section on the sediment management recommendations for dredging as recommended in the CIA, and the associated Sediment Management Proposals of staff, which take account of these recommendations and align them with the detailed design methods provided for dredging by the contractor.
In addition, Section 9(2) states that:
(2) No person may use land in a manner than contravenes a regional rule unless the use is: (a) Expressly allowed by a resource consent; or (b) is an activity allowed by section 20A
The application requests consent is issued for the proposed dredging activity to meet the various requirements of the Land and Water Regional Plan and Waimakariri River Regional Plan.
Section 15(1) of the RMA states that:
“No person may discharge any –
(a) contaminant or water into water; or
(b) contaminant onto or into land in circumstances which may result in that contaminant entering water;
unless the discharge is expressly allowed by a rule in a regional plan …”.
The discharge of “water into water” as proposed within this consent, must therefore be expressly allowed by a rule in a regional plan and any relevant proposed plan or resource consent. This application requests approval of the take and discharge of dewatering water from and back into the Kaiapoi River. The proposed dredging may also release contaminants (e.g. sediment) into the Kaiapoi River or onto adjoining land, therefore the package of activities associated with dredging, including spoil dewatering, are assessed through this activity.
Section 104:
Section 104 requires the consent authority to, when processing the consent application, have regard to the following:
• Actual and potential effects on the environment
• Any proposals or measures agreed to offset or compensate for adverse effects
• Provisions of plans and national or regional policy statements
The WDC has identified actual and potential adverse effects of the activity on the environment. These particularly relate to the potential discharge of sediment into the water column during dredging and disturbance of fish habitat within the river bed. The adverse effects of dewatering spoil are also assessed: effects include whether to avoid periods of saline intrusion during dredging to avoid application of salt entrained within sediment to land; or conversely, using salt to provide permanent weed control on land during development of the Regeneration Areas. Options and mitigations within the application are proposed which seek to address each of the identified issues.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 37 Status: FINAL The application notes the aquatic intertidal planting as a potential “offset” which, although noted in this application, is nonetheless already underway and intended to be continued to improve the health and habitat of aquatic species in the river that are likely to be affected by the proposed dredging. This planting is primarily intended to assist trap and treat suspended sediment in the river water column and improve river habitat. It is intended to be continued regardless of whether or not the dredging projects proposed in this application are approved.
Section 105:
Section 105 provides, for applications for a discharge permit that contravenes section 15 the consent authority must have regards to the following:
• the sensitivity of the receiving environment to adverse effects
• the applicants reasons for the proposed choice
• any possible alternative methods of discharge, including discharge into any other receiving environment
The Council within the application describes the sensitivity of the Kaiapoi River, including the aquatic ecosystem characteristics and habitat values. This includes results of previous fish and invertebrate surveys, stream health index summaries, macrophyte information and sedimentation levels (both suspended and legacy sediment) and other waterway health characteristics. It then assesses the proposed dredging activity in terms of their effects on each aquatic species and stream characteristic.
The application also includes a separate section on alternative dredging and associated dewatering methods. The preferred method and option is described and reasons provided where alternatives have not been considered practicable.
Section 107:
Section 107 provides constraints for the consent authority on issuing discharge permits that contravene Section 15 of the RMA. The consent authority will consider certain criteria when deciding whether to approve activities which result in a variety of identified adverse effects, including significant adverse effects on aquatic life. Consents may only be granted if:
• there are exceptional circumstances which justify the granting of the permit; or
• the discharge is of a temporary nature; or
• the discharge is associated with necessary maintenance work.
The consent holder may also be required to undertake works in stages through the term of the permit that will ensure upon the expiry of the consent that any relevant regional rules will be met and adverse effects will be addressed.
The legislation requires the Council to make improvements in time that will avoid any ongoing significant adverse effects of its activities.
Council has proposed a series of mitigations that it will undertake during the dredging to mitigate the adverse effects, which are temporary. The pontoon dredging project will create a temporary adverse effect in order to establish a new facility to provide easy, safe public access into the river in the town centre.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 38 Status: FINAL 4.2 Waimakariri River Regional Plan Requirements The Waimakariri River Regional Plan (WRRP) became operative on 23 October 2004. As it contains the provisions for the Waimakariri River catchment, it is applicable to the proposal.
Rule 5.1 Taking of Water from Surface Water of a Waimakariri River Tributary
Within the area of the Waimakariri River Catchment “below Woodstock”, the taking of water from any surface waters of the Waimakariri River or its tributaries is a discretionary activity for which the Canterbury Regional Council has restricted its discretion.
Condition Compliance
a. Fish shall be prevented from entering the water intakes Does not comply It is considered that trout, salmon, smelt or other fish usually present in the river at the time of dredging would be able to avoid the suction cutter dredge operation due to the natural fish “flight” response. However eels present in the river bed sediment may not be able to avoid the hose mouth and may be conveyed into the dredge and on into the dewatering area. Options to avoid conveying eels into the dredge will be discussed further with the contractor. Alternatively, options to electrofish and relocate eels could be further investigated. b. The taking of water shall cease for periods of up to 48 Complies hours upon notice by the Canterbury Regional Council, The dredging operation is likely to abstract to allow measurement of the natural water flow, or an estimated 40-60 L/s from the lower groundwater levels Kaiapoi River downstream of the Williams Street Bridge, and return this water to the river as a non-consumptive take, following abstraction, settlement and treatment. It is noted that there is uncertainty in actual pumping volumes, though on average these are not likely to exceed 60 L/s. The take of water is incidental to the dredging operation and all abstracted water is intended to be returned to the river as soon as practicable following dredging. The take of water will cease if requested at any time by the Regional Council.
(c) to (e) Conditions (c) to (e) address “AA”, “A” and “B” permit Complies abstractions for taking of water from the Waimakariri River or The take is proposed to be a non-consumptive, tributaries from the area downstream of Woodstock. temporary water take abstracted in the winter season. It is proposed to return diverted water back to the river. The rules for permitted water takes seem to apply for ongoing takes which include consumptive use of the water off-site, rather than temporary non-consumptive takes.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 39 Status: FINAL
Rule 5.2 Use of Water from Waimakariri River Tributary
Within the area of the Waimakariri River catchment “below Woodstock” the use of any water in tributaries of the Waimakariri River; the diversion of water from, or the discharge of water into the Waimakariri River or its tributaries is a discretionary activity in accordance with Rule 5.2 of the WRRP. Financial Contribution: A financial contribution, in the form of money, land, or any combination thereof, may be required as a condition of resource consent granted under Rule 5.2. The financial contribution shall be made for the purpose of:
(a) Restoring, to pre-activity conditions at the same location or in close proximity, any natural or physical resources which suffer damage or loss as a result of the activity; or (b) Ensuring that there are positive effects on the environment, at the same or any other location within the Waimakariri River catchment, to offset any adverse effects of the activity on natural or physical resources.
The “use” of water for take and discharge during dewatering does not fit the definition of water use under Rule 5.2. This is because the purpose of the activities in this application are not of exclusive value for the Council as applicant, but rather provide wide benefit to the whole community from the proposed pontoon installation which will benefit all those using small vessels in the river.
Nonetheless, the balance of the Kaiapoi River Rehabilitation Project (apart from dredging) provides an offset for the proposed “take” or “use” of river water for dredging and dewatering, as it provides for constraining the channel with intertidal aquatic plantings to trap and treat suspended sediment, creation of a major sediment trap and gravel beach wetland at the elbow bend which will all provide habitat improvements and greater habitat diversity in the river.
Rule 6.1 Discharge of contaminants to land and surface water in Waimakariri River catchment Rule 6.1 states “The discharge of contaminants into surface water bodies in the Waimakariri River Catchment, or onto or into land within 20 metres of surface water bodies, or onto or into land in circumstances which may result in that contaminant entering surface water bodies, is a discretionary activity.
Rule 6.1 of the WRRP applies to the discharge of stockpiled dewatering water into the Kaiapoi River (as a Waimakariri River tributary) and is considered a discretionary activity.
Rule 6.1 (iii) Class WAIM-TRIM Water (being water managed for drinking water for animals, fisheries, fish spawning, aquatic eco-systems, and aesthetic purposes). Rule 6.1 “water quality standards apply to the tributaries of the Waimakariri River”, in accordance with the following standards.
Condition Compliance
1. There shall be no production of conspicuous oil or Complies grease films, scums or foams, or floatable or suspended The use of cutterhead suction dredge in the materials. Kaiapoi River bed will lift sediment from the bed and deposit it for dewatering at a nearby location on the banks or adjoining land. No oil or grease or other foreign substances will be generated during the works. Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 40 Status: FINAL Condition Compliance
2. There shall be no conspicuous change to the colour or Does not comply visual clarity. A conspicuous change in colour shall be The Kaiapoi River is heavily sedimented, defined as a change greater than 5 points on the with suspended sediment present in the Munsell scale. A conspicuous change in visual clarity water column conveyed up and shall be defined as a change greater than 20%, as downstream with the tide. measured by black disc. The Council does not propose to use black disc or Munsell scale measures to measure change in clarity or colour during dredging in the Kaiapoi River. The black disc method would require the operator to be submerged in the river water which is considered unsafe given depth of water and tidal flows, presenting a drowning and health (infection) risk. Instead, this application proposes use of clarity tube together with a quick field visual reference method to check and verify changes in clarity. It proposes use of clarity tube sampling comparison of >20% clarity difference during dredging as the trigger/s for further investigation and remediation, if additional best practice measures are able to be identified and implemented. Discretion will be sought for the dredging operation to continue however, if the clarity measure exceeds 20%, provided that the contractor can demonstrate all practicable sediment control measures are being utilised in the river. For quick visual reference in the field it is proposed that a sample of river water is taken from the water column immediately prior to dredging on any day, for comparison with additional sample/s taken during active dredging. Visual differences can be photographed and provided to compliance officers as required. 3. There shall be no emission of objectionable odour Complies The dredging within the river will involve movement of sediment and dewatering of river water. No additional substances will be released into the river that would generate any odour. The river bed sediment has been shown to not be contaminated with odorous substances (see description of the environment section for details of sediment contamination testing). 4. The maximum cover of stream or river beds by Complies (e.g. algae, slime, detritus) periphyton as filamentous growths or mats greater than The dredging of the river bed will not 3 millimetres thick, shall not exceed 40%. introduce additional nutrients into the water column that would provide the enrichment which leads to increased Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 41 Status: FINAL Condition Compliance
periphyton growth. The dredging operation will have no impact on existing periphyton growth in the river, other than very small scale possible temporary disturbance of existing growths or mats. 5. Bacterial or fungal slime growth (also known as Complies heterotrophic growths or sewage fungus) shall not be Aquatic ecology studies for the Kaiapoi visible to the naked eye as plumose growths or mats. River presented in Section 2 of this application do not indicate presence of any bacterial or fungal slime growth in the river. Dredging will not introduce any new bacteria or other new substances into the river and therefore would have no effect on any bacterial growths present at the time of dredging. 6 The BOD5 of GF/C filtered water shall not exceed 2 Complies grams per cubic metre. The Council has not monitored the BOD5 levels in the Kaiapoi River and no laboratory results are available. However, presence of salmon, smelt, adult trout and eels in the river indicate fair water quality with sufficient oxygen available for these species in the proposed dredging reaches. The proposed dredging will not have any effect on dissolved oxygen levels or oxygen demand of aquatic species present in the Kaiapoi River, or any corresponding other effect on river habitat other than at the immediate dredging sites, noting the activity is temporary in nature. 7 The concentration of dissolved oxygen shall exceed 80% Complies of saturation concentration. The dredging will not have any effect on dissolved oxygen levels within the Kaiapoi Note: the comparative measure in the Land and Water River. Regional Plan Table 1A (freshwater outcomes) is 70% minimum saturation for both spring fed plains rural and urban streams.
8 Fish and other aquatic organisms shall not be rendered Complies unsuitable for human consumption. Fish and mahinga kai collected from the Kaiapoi River are generally unlikely to be impacted by the proposed dredging, as individual fish present in the dredging reaches will be able to avoid the dredging operations due to the noise and disturbance in these areas. The activity is considered likely to provide sufficient warning for fish to ensure a flight response, meaning that fish in the area will avoid the dredging activities. The exception are eels present in
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 42 Status: FINAL Condition Compliance
the river bed sediment which may not be able to avoid the suction mouth during dredging. This risk will be discussed further with the contractor. 9 There shall be no statistically measurable impairment of Complies the reproductive ability of fish or of the food of fish. Spawning surveys of the upper Kaiapoi River have indicated in previous years AND that trout and salmon spawning occurs in the upper reaches. There is no trout
or salmon spawning in the lower Kaiapoi River in any of the proposed dredging reaches, due to the heavily sedimented river bed at these locations. The lower river sedimentation is predominantly
understood to be from previous release of legacy sediment during historic urban and rural development in and around Kaiapoi and from discharges from upstream waterways occurring over a
number of decades. The dredging activity will not affect any trout or salmon spawning in the Kaiapoi River as these sites are not present within the proposed dredging reaches. Inanga
spawning sites are however present near the proposed dredging reach and the timing of dredging will be arranged to occur outside of the inanga spawning period (no dredging from 1 January to 1
June) to avoid any effects on whitebait spawning. The food of fish would potentially be impacted in the dredging sites but fish would usually not be present in these areas during dredging.
It is anticipated the river system and ecology including food of fish will recover quickly following dredging as the activity will have only short term, temporary effects. In any case, the upper reaches of the river and tributaries provide other areas to maintain food of fish.
There shall be no toxic effect on fish or on the food of Complies fish. For the purpose of this standard, fish, and the food The dredging activity will not have any of fish, does not include any organism specified as a toxic effect on fish or the food of fish. pest in a pest management strategy under the This is because the sediment within the Biosecurity Act 1993. dredging areas has been sampled and is shown in this application to have a low risk of releasing environmental contamination during dredging, noting the results indicate that dredging will Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 43 Status: FINAL Condition Compliance
not release any contaminants into the water column that could have a toxic effect on fish or the food of fish.
10 The natural temperature of the water shall not be Complies changed by more than 3 degrees Celsius, and shall not The proposed dredging will not change the exceed 25 degrees Celsius at any time, and the water temperature within the Kaiapoi River. temperature of the water shall not adversely affect the spawning of trout or salmon during the spawning season.
Note: In comparison, the Land and Water Regional Plan states in Table 1A “Freshwater Outcomes for Canterbury Rivers” that the natural temperature of the water shall not exceed a maximum of 20 degrees Celsius and any temperature change [as a result of a discharge]shall not exceed 2 degrees Celsius. 11 The water shall not be rendered unsuitable for Complies consumption by farm animals. The water in the Kaiapoi River is not currently accessed by farm animals and the river is required to be fenced to prevent direct stock access. The saline content in the river water is also likely to render the water unsuitable for farm animal consumption. The Kaiapoi River is therefore not considered a relevant source of drinking water for farm animal consumption.
Section 7: Works in the beds of rivers
The proposed dredging and piling activities are not permitted activities under Rules 7.1, 7.2 or 7.3 of the Waimakariri River Regional Plan, as they do not fit with the description of permitted activities under any of these rules.
The disturbance of the bed of the Kaiapoi River is therefore a discretionary activity under Rule 7.4 of the Waimakariri River Regional Plan.
Financial Contribution: A financial contribution, in the form of money, land, or any combination thereof, may be required as a condition of resource consent granted under Rule 7.4. The financial contribution shall be made for the purpose of:
(a) Restoring, to pre-activity conditions at the same location or in close proximity, any natural or physical resources which suffer damage or loss as a result of the activity; or (b) Ensuring that there are positive effects on the environment, at the same or any other location within the Waimakariri River catchment, to offset any adverse effects of the activity on natural or physical resources.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 44 Status: FINAL This application notes the balance of the Kaiapoi River Rehabilitation Project (apart from the proposed dredging activities) provides a general, long term programme which will help address any adverse impacts from the proposed “take”, “use” of river water and “works in beds of rivers” required during dredging and dewatering. The river rehabilitation project provides for constraining the river channel with intertidal aquatic plantings to trap and treat suspended sediment, creation of a major sediment trap upstream of Mafeking Bridge, and gravel beach wetland development at the elbow bend in the river. These will all provide habitat improvements, greater habitat diversity and enhance amenity and mahinga kai resources in the river.
4.3 Canterbury Land and Water Regional Plan The LWRP was made partially operative on 1 September 2015 and 1 December 2015. The LWRP must be considered in terms of the rules controlling excavation of land above groundwater and in proximity to a river, and take of water from and discharge of water into a river.
Water for Construction Maintenance
Condition Compliance
5.116 The taking and using of water from a river, lake or an Not applicable artificial watercourse for infrastructure construction, maintenance and repair is a permitted activity, This rule applies to taking and using water provided the following conditions are met: from a river, and is therefore not 1. The take and use does not exceed 15 L/s and considered applicable to assessment of 100m3 per day; and the proposed dredging activity, for which 2. The take and use is for no longer than 2 the water take is both non-consumptive months; and and incidental to the dredging activity.
3. The take does not an any time exceed 10% of the flow at the point of take; and
4. Where the take is from a water body with a minimum flow set in Section 6 to 15, the take or diversion ceases when the flow is at or below the minimum flow, as estimated by the Canterbury Regional Council; and 5. The take is not from a wetland; and 6. Fish are prevented from entering the water intake as set out in Schedule 2; and 7. Where the take is form a water race, irrigation or hydro-electricity canal or storage facility, the abstractor holds a current written agreement with the holder of the resource consents for the taking or diversion of water into the canal or storage facility; and 8. The take is not from any river or part of a river that is subject to a Water Conservation Order.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 45 Status: FINAL
Take and Use Surface Water (non-consumptive)
Condition Compliance
5.126 The non-consumptive taking and use of water from a Not applicable lake, river or artificial watercourse and discharge of the The proposed dredging activity is covered same water to the same lake, river or artificial under applicable Rules of the Waimakariri watercourse is a restricted discretionary activity, River Regional Plan. provided the following conditions are met: In addition, the non-consumptive take and 1. Limits have been set for that surface water use of water from a river is incidental to body in Sections 6 to 15 or the lake or river is the proposed dredging activity with no subject to a Water Conservation Order; and purpose for taking water other than that 2. The taking of water and subsequent discharge which is abstracted and returned whilst does not result in any exceedance of any limit dredging. set for that waterbody in Sections 6 to 15 or flow and allocation regime set out in the
Water Conservation Order; and
3. Other than for the replacement of existing consents for activities provided for under Policy 4.51, the maximum distance from the point of take to the point of discharge is not more than 250m; and 4. Other than for the replacement of existing consents for activities provided for under Policy 4.51, the take is not from a wetland, hapua or a high naturalness lake or river that is listed in Sections 6 to 15.
Refuelling in the Bed of a River
Condition Compliance
5.145 The use of land for the refuelling of vehicles or Permitted equipment in the bed of a lake or river is a permitted activity, provided the following conditions are met: The refuelling of the suction dredge will 1. The refuelling of machinery does not take place not be undertaken whilst the dredge is in over the wet bed of a river or lake, or in any the Kaiapoi River. area where spills may enter surface water ;
and Refuelling of the dredge (whilst not in the 2. All refuelling and bulk deliveries are directly river), will be directly supervised by the supervised by the equipment operator; and equipment operator; and
3. Refuelling occurs on an impermeable surface or When refuelling is required it will be drip trays are used, or other effective spill- undertaken on an impermeable surface, containment equipment is installed. or over drip tray or using other spill containment procedures.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 46 Status: FINAL Condition Compliance
The dredge refuelling procedures and associated spill procedures (for operating the pump) will be required to be detailed in the Site Management Plan to be provided by the Contractor and approved by the Council and Environment Canterbury prior to works commencing.
Excavation over an Aquifer
Rule 5.175 states that “The use of land to excavate material is a permitted activity, provided the following conditions are met:
The proposed dredging reaches and spoil dewatering treatment and storage facilities will be located above an unconfined or semi-confined aquifer, as shown on the Canterbury Planning Maps.
Condition Compliance
2. Over an unconfined or semi-confined aquifer: Permitted (a) The volume of material excavated is less than This rule is not intended to apply to river 100m3; or dredging works which are already (b) The volume of material excavated is more addressed under the WRRP. The rule than 100m3 and: therefore does not apply to the dredging activity. (i) There is more than 1m of undisturbed material between the deepest part of the excavation and The construction of the proposed the seasonal high water table level; dewatering settlement facility on the and Corcoran and Askeaton Reserves are (ii) The excavation does not occur within intended to be built above the existing 50m of any surface water body. ground level largely using the existing ground contours. Excavation of the settlement ponds is not envisaged, though if determined to be necessary through the detailed design stage to be developed in conjunction with the contractor, then a separate consent for these excavations would need to be sought. It is not anticipated that any excavations below the natural ground level for this activity would be required on the river banks in any area.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 47 Status: FINAL 4.4 Canterbury Air Regional Plan
Condition Compliance
Rule 7.3 The discharge of odour, dust or smoke into air that is Permitted not managed by any other rule in this Plan is a permitted activity provided the following conditions are See analysis of Rules 7.32, 7.35, 7.36 and met: Schedule 2. 1. The discharge does not cause or is not likely to cause
an adverse effect beyond the boundary of the property of origin; and
2 . The discharge does not cause an offensive or objectionable effect beyond the boundary of the property or origin when assessed in accordance with Schedule 2:
Rule 7.32 The discharge of dust to air beyond the boundary of the Permitted property of origin from unconsolidated land, is a The area used for storage of spoil will be permitted activity provided the following conditions are greater than 1000m2. met: A Dust Management Plan will be prepared The area of unconsolidated land is less than 1000m2, or by the contractor/Council as required once where the area is …greater than 1000m2 a dust the spoil has dried, to provide adequate management plan is prepared in accordance with containment measures for dust on site and Schedule 2 and implemented by the person responsible prevent its disbursal via wind from off the for the discharge into air; and site. The discharge does not cause an offensive or Water carts will also be used to dampen objectionable effect beyond the boundary of the any exposed, fully dried material if required property of origin, when assessed in accordance with during periods of high wind, prior to final Schedule 2. disposal. The discharge of dust will be contained within the spoil drying and stockpiling area by the contractor/Council, through use of aggregate, roading metal, silt fences or hydroseeding as appropriate, once the material has fully dried and prior to final disposal. Rule 7.35 The discharge of contaminants into air from the Does not comply handling of bulk solid materials is a permitted activity provided the following conditions are met: The Council will require the contractor 1 The discharge of dust does not cause an undertaking any handling of spoil, including offensive or objectionable effect beyond the transfer of spoil following dewatering to boundary of the property or origin, when any spoil drying and storage area or final assessed in accordance with Schedule 2; and disposal location to prepare a Dust Management Plan and submit this to the 4. Where the handling occurs outdoors and the Council for approval prior to the rate of handling exceeds 20t per hour, a dust commencement of the handling. The management plan is prepared in accordance DMP will contain measures to ensure the with Schedule 2 and implemented by the discharge of dust does not create any Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 48 Status: FINAL Condition Compliance
person responsible for the discharge into air; offensive or objectionable effect beyond and the boundary of the site. The dust management plan will be 5. The dust management plan is supplied to the submitted to the CRC on request. CRC on request; and The handling of bulk solid materials will
occur within 200m of sensitive activities 6. The discharge does not occur within 200m of a (e.g. the Kaiapoi River stopbank walkway, sensitive activity, wahi tapu, wahi taonga or an existing Regeneration Zone dwelling at place of significance to Ngai Tahu that is 65A Cass Street (110m from nearest part of identified in an Iwi Management Plan; and storage transfer handling area) and within 200m of place of significance to Ngai Tahu (being the area of riparian plants and river margin adjacent to the Courtenay confluence).
Rule 7.36 The discharge of contaminants into air from the Does not comply outdoor storage of bulk solid materials is a permitted The Council will prepare and implement a activity provided the following conditions are met: Dust Management Plan prior to the 1 The discharge of dust does not cause an offensive or establishment of the outdoor storage area objectionable effect beyond the boundary of the for the spoil. property of origin, when assessed in accordance The DMP will contain measures (as noted with Schedule 2; and above) to ensure the discharge of dust does 2 The amount of material stored does not exceed not create any offensive or objectionable 1000t when it has an average particle size of less effect beyond the boundary of the site. than 3.5mm; and The spoil stored at the Stage 2 drying and 3. Where the storage exceeds 200t, a dust storage areas will be spread across the management plan is prepared in accordance with available ground area to facilitate rapid Schedule 2 and implemented by the person drying. responsible for the discharge into air; and The discharge occurs within 100m of 4. The dust management plan is supplied to the CRC sensitive activities (e.g. the walking track on request; and on the Kaiapoi River stopbank, use of public 5. The discharge does not occur within 100m of a boat ramp at the Askeaton Reserve) and sensitive activity, wahi tapu, wahi taonga, or place place of significance to Ngai Tahu within of significance to Ngai Tahu that is identified in an 100m of the site being the riparian plant Iwi Management Plan. area on the river margins. Schedule 2 Criteria for assessing offensive or objectionable dust The Council will establish a dust / odour Resource consent applicants…will have regard to the complaints register relating to the dredge following matters when determining whether or not a dewatering and storage sites and will dust discharge/ discharge of odour has caused an monitor and investigate any complaints objectionable or offensive effect: that are received. 1. The frequency of dust/odour events; and 2. The intensity of dust/odour events, as It will adjust operations on site to avoid or indicated by dust quantity and the degree of manage complaints or address any effect (or with odour, degree of strength, complaints that arise with the following taking account of character or quality) ; and measures proposed: 3. The duration of each event;
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 49 Status: FINAL Condition Compliance
4. The offensiveness of the discharge having • Use of water carts to dampen regard to the nature of the dust including exposed materials when required soiling of materials or structures and any prior to final disposal potential health effects; or character of the • Use of aggregate, roading metal, odour including reference to hedonic tone; hydroseeding or silt fences as and relevant to stabilise exposed 5. The location of the event, having regard to the surfaces sensitivity of the receiving environment, • Odour mitigation measures may including taking account the relevant zone(s) require expertise of SQEP, whom and provisions in the relevant District Plan. can be engaged to assist the Council develop a suitable response if complaints are received. This may depend on bacterial content of the spoil and length of time taken for dewatering. Definition of Sensitive Activity means an activity undertaken at a sensitive place or in an area where a person or persons are activity present and have a reasonable expectation that their enjoyment of the amenity values of that place or area will not be materially impaired by the effects of a discharge of odour, dust or smoke; and may include places where people gather for recreation, education, worship, culture or similar purposes, or where they reside, including outdoor living areas.
The discharge of contaminants into air do not meet the requirements of Rule 7.35 and 7.36 and are therefore a discretionary activity under the provisions of the Canterbury Air Regional Plan.
4.5 Overall status Overall, the following resource consents are required:
• The abstraction of surface water requires a resource consent as a discretionary activity in accordance with Rule 5.2 of the Waimakariri River Regional Plan (WRRP).
• The discharge of contaminants into surface water bodies in the Waimakariri River Catchment, or onto or into land within 20 metres of surface water bodies, or onto or into land in circumstances which may result in that contaminant entering surface water bodies, is a non-complying activity under Rule 6.1 of the Waimakariri River Regional Plan (WRRP).
• Works in the bed of the Kaiapoi River is a discretionary activity under Rule 7.4 of the Waimakariri River Regional Plan (WRRP).
• The discharge of contaminants (dust / odour) to air do not meet Rules 7.35 and 7.36 of the Canterbury Air Regional Plan and are discretionary activities.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 50 Status: FINAL 5 Description of Actual and Potential Environmental Effects
The proposal has been assessed against provisions of the Land and Water Regional Plan and the Waimakariri River Regional Plan to determine consent requirements.
The following assessment identifies and assesses the types of effects that may arise from the proposed works. This assessment also outlines the measures that the applicant proposes to implement in order to avoid, remedy or mitigate any potential adverse effects on the environment.
Actual and potential effects on the environment have been identified as including:
• Positive effects • Effects on water quantity • Effects on surface water quality • Effects on aquatic ecology and habitat • Effects on groundwater quality • Effects on lower bank and stop bank stability • Effects on air quality • Human health effects • Heritage effects • Cultural and tangata whenua effects
5.1 Positive Effects The proposed piling and dredging of the Kaiapoi River will have the benefit of establishing new recreational facilities in the river. These will increase opportunities for boating access in the river and provide additional safe locations for docking of small vessels. The anticipated result is increased use of the river by small vessels and ability of river users to more safely and easily access the river from within the town centre.
5.2 Effects on Water Quantity
5.2.1 Overview Excavation of the Kaiapoi River bed has the potential to marginally lower water levels in the river and increase its flood conveyance capacity to a small extent. The Kaiapoi River is currently already oversized in terms of its design flood conveyance capacity. It is considered that the proposed dredging will slightly improve the flood management level of service in this already oversized channel by very marginally increasing its current flood conveyance at the dredging area.
5.2.2 Pontoon Placement Effect on Flood Conveyance The pontoons guide pile heights are proposed to be set above the spring high tide level and at a sufficient level to accommodate the local flooding scenario of water level RL 2.6m. This water level is approximately 800mm above the existing river wall near the bridge.
The pontoons will be able to float up to this design flood level without de-coupling. In this localised flood scenario the pontoons would be unusable, however, due to the gangways and other safety risks.
In the 1 in 450 year scenario – the pontoons would float off the top of the guide piles, and then be restrained by anchor chains attached to the pile bases to prevent them from being taken away by the flood current. In this scenario the gangways would become de-coupled and could be damaged. This approach reduces the piling costs (due to length, and also to structural loading and geotechnical considerations) and avoids having the guide piles protruding a long way out of the water and above the adjacent banks and terraces. Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 51 Status: FINAL 5.2.3 Non consumptive Abstraction and Dewatering During the dredging operations, a mix of spoil and water will be abstracted from the river bed area and conveyed through the dredge pipe immediately to shore via the discharge pipe, into the dewatering area. Dewatering of spoil will therefore commence within a short period from when the spoil was abstracted. The water will be returned to the river from near the point of abstraction, meaning that the dredging will have a non-consumptive, temporary effect on water volume in the river as a result of the proposed “take of water” for dredging purposes.
5.2.4 Conveyance A report by Tony Boyle from Environment Canterbury titled “Kaiapoi River Flood Capacity Investigation” (April 2016, pi) “assessed effects of sea level rise projections, because of Climate Change on the flood carrying capacity of the Kaiapoi River to inform riverside redevelopment initiatives, and to enable the Kaiapoi River Rehabilitation Project proposals to be assessed in relation to the flood hazard…”.
It concluded that the current recently re-constructed stop banks are adequate for foreseeable sea level rises, and the Kaiapoi River Rehabilitation Project proposals can proceed as planned. The report found that “there is likely to be ample opportunity for channel modifications to improve water quality, navigability, amenity and recreation, which would not be expected to have significant adverse effect on flood capacity” (Boyle, p.17).
Modelling of the Kaiapoi River by Environment Canterbury (as also summarised in Tony Boyle’s report) has verified that the river will not be adversely impacted by the river rehabilitation proposals. The report primarily assessed, for river rehabilitation, the proposal to narrow and constrain the channel with side bar and point bar intertidal planting which would add roughness to the river margins, assisting to trap and treat suspended sediment in the river. The report shows the modelled capacity of the river is such that the rehabilitation proposals for increased channel “roughness” would not have any adverse effect on flood conveyance capacity and can “proceed as planned”.
It is acknowledged that the report did not directly consider the impact of dredging in conjunction with the proposal to constrain the channel with intertidal planting. However, the combination of effects of the two activities (dredging and planting) would in any case marginally increase the flood capacity of the river as dredging increases capacity and planting does not reduce it (although planting does potentially constrain channel flow paths within the existing channel margins). Therefore this application concludes that the proposed dredging activity, undertaken in conjunction with river margin intertidal planting will not have any adverse effect on river capacity.
The proposed dredging will likely lower water levels marginally at some areas, potentially exposing larger areas of mud- flats at low tide. This will be mitigated by the placement of the proposed new pontoons and deep surrounding dredging for berthing purposes, in conjunction with the ongoing aquatic wetland planting programme which is being undertaken by the Kaiapoi River Rehabilitation Working Party in nearby areas on the river banks, in parallel with the floating pontoon and wharf redevelopment projects. The planting is intended to continue provided that the existing trial plantings are proven viable when reviewed again in the summer of 2018/19.
5.2.5 Recent Flooding Recent flooding in Kaiapoi occurred in June 2014. This flooding was a result of the inability of the Kaiapoi urban stormwater network, as modelled, to convey a 50 year flood event without any flooding of dwellings. On this occasion a significant rainfall event, estimated at a 1 in 67 year ARI event, coincident with a proceeding period of high rainfall causing elevated groundwater in rural areas surrounding the town, which reduced the rates of discharge to ground and increased surface runoff. During this event a number of Kaiapoi properties were flooded.
The proposed dredging within the river will have no material effect on the potential for further flooding of dwellings in Kaiapoi. This is because this risk is associated with the performance of the urban stormwater network and the capacity of the Kaiapoi River tributaries, which will remain unchanged as a result of the activities proposed in this consent. The flooding of Kaiapoi dwellings is being addressed instead through the Kaiapoi Stormwater Network Discharge Consent.
5.2.6 Water Quantity Conclusion
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 52 Status: FINAL
Based on the above information, the assessment of effects of installing pontoons and managing the dredging activity on water quantity (flows) in the Kaiapoi River are assessed as being less than minor.
5.3 Effects on Surface Water Quality 5.3.1 Surface Water Effects Introduction During the dredging operation it is possible that water quality could be affected by bed excavation that releases sediment into the water column. If sediment was contaminated it is also possible that contaminants could be disbursed through the water column during excavations and released into the wider river system. It is possible that removal of spoil could disturb and release sediment that is contaminated with zinc, lead, chromium or other heavy metals into the water column where these metals could be suspended with sediment or dissolved in the water and disbursed around the river system with the tide.
5.3.2 Release of Contaminants The Kaiapoi River water column contains relatively high levels of suspended sediment in normal flow conditions, as discussed in Section 2- Description of the Environment. The river bed itself is also heavily sedimented. The dredging and piling activities are likely to temporarily add additional sediment to the water column in the area around the dredging reaches and piles, which will be disbursed with the tide prior to eventual settlement.
Section 2 includes river bed sediment contaminant testing results which indicate a low risk of contamination from dredging and piling at the sampling site near the wharf. The heavy metals noted above (chromium, lead and zinc) in a few instances exceeded background soil concentrations at the wharf sampling site. Therefore the risks and potential effects of these entering the river system are discussed further here.
The sediment sampling indicates a low risk that heavy metals within the excavated sediment could be released during dredging and piling within the sediment plume and disburse via suspended sediment or in dissolved form through the river system. Due to tidal action, flow volumes in the lower Kaiapoi River and interaction with the salt water wedge, it is likely that any metals released into the river system would be rapidly diluted, neutralised by contact with salt water and/or dispersed by the tide. It is considered unlikely that any adverse effect on fish or invertebrates would occur from any heavy metal contaminants released into the river system within any sediment plume which is generated, due to the low anticipated concentrations and rapid dilution/disbursal, as indicated by the sediment testing.
The cutter head suction dredge method has been selected in this application as it is understood to carry the lowest environmental risk of release of sediment into the river water, of the available dredging options. The Contractor will be requested to prepare an Erosion and Sediment Control Plan which will need to be approved by the Council and Environment Canterbury prior to the commencement of dredging at each site. This will detail the methods best suited to Erosion and Sediment Control (including sediment management) associated with the specifications of the actual suction dredge machine engaged to be deployed at each dredging location. This will enable a responsive and flexible approach to best manage sediment abstraction and avoid or reduce disbursal and turbidity using features of the available equipment, wherever practicable.
The dredge equipment used in the river will also be cleaned of any organic residue, soil or any other attached material prior to use. Therefore the dredge will not introduce any significant new volume of any substance, chemical, hydrocarbon or other contaminant into the river, beyond any trace substances including dust or soil that is attached to the dredge at commencement. The dredging is considered chemically neutral to the river environment, not introducing any new substance into the river which was not already present prior to the dredging.
This application considers the water quality contaminant of greatest concern during dredging to be bacterial contamination of the waterway. Greer and Meredith (2016) explain that “most spring fed rivers in the Kaiapoi River
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 53 Status: FINAL catchment are unsuitable for contact recreation due to significant faecal contamination” (p.52). It is considered likely that high bacterial contamination will be present in the proposed dredging reaches at the time of dredging (as indicated by the Council’s baseline sampling of the Kaiapoi River water and its tributaries in 2016 (refer Section 2).
It could be argued that removal of sediment from deposition areas which contains heavy metals that slightly exceed background concentrations, and placement of this sediment on other areas of land which do not provide habitat for sensitive aquatic organisms could be a net benefit to the environment, providing metals are not released into the river water during dredging. For instance, the river bed sediment to be excavated is proposed to be moved to form a base for future infrastructure, including potentially for BMX track construction or other nearby non-productive or productive land uses, depending on spoil quality and characteristics.
5.3.3 Dewatering Discharge This application proposes to return any river water that is abstracted during dredging back into the river at a location close to the dredge operation, where practicable. A number of spoil dewatering and final disposal locations are currently being investigated, with the indicative preferred options identified in Appendix D. It is intended that the operation will be non-consumptive in terms of take and discharge of water, although the length of time required for dewatering means the return of water to the river will not be immediate. The discharge of dewatering water back into the river will not involve conveyance of any contaminant that was not already present within the surface water prior to dredging.
The dewatering water is likely to contain indicator bacteria concentrations and suspended sediment. There is a risk of a bacteria spike from a concentrated discharge of dewatering water back to the river, given the shallow nature and likely warmer water temperatures of the dewatering pond/s. Any such spike would be only temporary, with the risk mitigated by the significant flow volumes (and dilution) into the Kaiapoi River and eventual interaction with salt water as the discharge moves downstream on the outgoing tide to the sea.
The dewatering water is unlikely to contain other urban source contaminants (e.g. dissolved heavy metals) – as these were generally not found, or found only at low levels in the surface water or in the sediment within the dredging reach. This is indicated in the surface water quality sampling results (attached) provided by the Council during its 2016 baseline sampling which found either low (complying) or non-detectable levels of dissolved metals in the proposed dredging reaches. However this sampling found higher suspended sediment in the lower Kaiapoi River than in most of its tributary sites, and high indicator bacteria presence in some locations, with spikes during some of the sampling events.
The dewatering water is likely to contain agricultural source contaminants including ammoniacal nitrogen or Dissolved Reactive Phosphorous, as indicated in the 2016 baseline water quality sampling results. These agricultural contaminants are likely to be present in the river water prior to dredging and would be released back into the river immediately following dredging. The dredging would have no impact, or would not be affected by the presence of rural source contaminants in the river water.
5.3.4 Water Quality Effects Conclusion Overall it is considered that the potential adverse effects of the dredging and piling on river water quality in the Kaiapoi River in terms of potential disturbance and release of contaminants will be less than minor, as the river bed sediment contamination testing indicated a low risk of environmental contamination from dredging.
The proposed effects of the dredging on suspended sediment discharges are anticipated to be no more than minor. This is a likely effect of suction dredging within the river releasing a short term sediment plume which may be considered similar in nature to other periods of high sedimentation occurring within the river during storm events.
This can be mitigated through the use of silt fences within the water column, which can be deployed in the channel to protect any sensitive habitat areas identified by the Department of Conservation, Environment Canterbury or Ngai Tuahuriri prior to and during the dredging activities. Alternatively silt fences can be deployed to surround and contain
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 54 Status: FINAL suspended sediment near the barge, to be released during periods of higher background turbidity, as agreed with any parties observing the activity. These options will be discussed with the contractor and included in the Erosion and Sediment Control Plan to be approved by the Council prior to commencement.
The Council proposes to contact each of these parties prior to commencement and invite further comment on any requested protection of sensitive habitats near the dredging activity area.
5.4 Effects on Aquatic Ecology and Habitat
5.4.1 Overview
Stream habitat and ecology can be adversely affected by dredging and piling activities in the river. This may occur during disturbance of river bed sediment and associated temporary disturbance of the water column, which may have a temporary effect on native and introduced fish and macro-invertebrates. Other temporary effects on habitat include noise and an increased sediment plume beneath the surface which may affect fish flight responses. This may expose prey species to additional temporary predation during dredging.
The application attaches sediment contamination testing results which indicates the sediment in the proposed dredging and piling areas is unlikely to be contaminated. Therefore there is no anticipated harmful redistribution of any contaminant within the river system as a result of the dredging. The permanent habitat quality of species in the river will remain unchanged other than in the immediately dredged areas.
5.4.2 Effect on Fish and Invertebrate Species
Dredging will cause permanent change of fish and invertebrate habitat at the actual dredged locations. This will require fish and invertebrate communities present at these locations to re-establish themselves within the new habitat established at completion, or within other more suitable habitat within the river. These changes will be species specific, subject to the final bed profile established at each area.
The short term loss and disruption of habitat during dredging is balanced by the potential to deepen the river bed in the dredging areas, which will provide new habitat for those fish species which prefer deeper water. These changes will be as a result of the new river bed profile established following the dredging.
However, water levels at the margins may be slightly lowered at these same dredging locations. The lowering of water levels will be balanced by the ongoing intertidal aquatic planting programme in other areas up and downstream of the dredging reach, which is establishing salt tolerant plants which occur naturally in the Kaiapoi River at new locations on the side and point bars. The plantings, which include raupo and schoenoplectus, are being placed in the intertidal margins with the intent of narrowing, meandering and constraining the river channel flows so as to trap and treat suspended sediment as part of a long term programme to improve the river water quality and habitat.
The trout spawning exclusion period is between 1 May to 31 October each year. However, trout spawning in the lower Kaiapoi River proposed dredging reaches is not known to occur, as the river bed in these areas is too heavily sedimented. It is understood trout require course cobble or gravel for spawning, rather than fine sediment. Trout spawning is known to occur in the upper reaches of the river in a number of locations several kilometres upstream of the dredging reaches, as indicated in the reports by AEL 2012 and 2016.
A report by AEL in 2012 includes the fish migratory calendar for common freshwater fish in the Waimakariri. These migratory fish cycles across the fish species represented in the upper Kaiapoi River occur throughout much of the year. (page 4). A table on page 21 of the 2012 report indicates that key species present in the Kaiapoi River, including Chinook Salmon, short and long fin eel, common smelt and inanga / whitebait are all sea migratory species. It is therefore
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 55 Status: FINAL important that the dredging activities ensure continuing fish passage during the dredging and minimise disturbance of the river environment.
A report from Golder Associates “Waimakariri Plains Tributaries Aquatic Ecology Report” 2009 notes “the Kaiapoi River is a nationally significant spawning site for salmon. In the opinion of the aquatic ecologist, the protection of salmon passage is considered high priority, given the significance of this river for salmon fishing and the presence of the hatchery in Silverstream”.
“Adult brown trout and large eels require greater depths and habitat availability is likely to decline with flow….The aquatic ecology report recommends a minimum flow of 1,000L/s to protect the habitat of salmon, adult brown trout, large eels and other native fish” (page 19).
The use of cutter head suction dredge is understood to be detrimental only to the eel population resident in the river within the river bed sediment. Eels are the only fish species that may not be able to avoid the dredge suction cutterhead movement on the river bed. Fish passage for salmon, trout and smelt will be retained around the dredge operation and these fish will be aware of the dredging on the river bed and will be able to avoid it.
The contractor will be asked to consider options to reduce likelihood of eels entering the suction head hose mouth during dredging and report these within the Environmental Management Plan required to be approved by the Council prior to commencement.
Also considered is the presence of invertebrates within the lower river as an indicator of general habitat health. Quantitative invertebrate survey information is provided by Greer and Meredith (2016, p.2) who explain “invertebrate communities with a QMCI score below 4 are indicative of poor water quality, communities with a score between 4 and 5 are indicative of fair water quality, communities with a score between 5 and 6 are indicative of good water quality …”.
This application in Section 2 shows the invertebrate community in the lower Kaiapoi River within the proposed dredging reaches, particularly in the urban reaches of the river, is considered to be fairly degraded. Invertebrate scores in these reaches are commonly less than 5 and sometimes less than 4 (indicating poor to fair habitat quality). The dredging activity will damage invertebrate habitat in the short term. However, as noted above, the intertidal aquatic planting programme will balance this damage through creation of new invertebrate habitat within the shallow intertidal zone on the river margins near the dredging area.
This commentary concludes that dredging in the Kaiapoi River bed will create temporary disturbance of some fish passage and loss of habitat for fish and invertebrates in the immediate dredging reaches. These short term, temporary issues will be offset by the longer term benefits of providing new, more diverse habitats including establishing greater depth in the river bed, and newly planted riparian wetland areas on intertidal point and side bars. The areas of greater bed depth will benefit species that utilise the deeper water including adult brown trout, large eels and salmon. The margin planting will provide improved habitat for both fish and invertebrates.
There are understood to be freshwater mussels present in parts the lower Kaiapoi River, although any populations present have not been surveyed. Due to recent increasing salt water intrusion the presence of freshwater mussels may be less than previously known in the proposed dredging reaches. Due to the water depths, tidal flows and danger for the public of harvesting these from the lower river, it is not proposed to survey or provide any relocation of these (if present) prior to the dredging activity. The CIA did not identify any mussel harvesting in the lower Kaiapoi River in or around the propose dredging areas.
To mitigate the risks of aquatic species mortality during dredging, an Environment Management Plan will be required to be submitted to the Council and will be required to be implemented prior to and during dredging.
Generally accepted best practice to minimise the impact on fish is to isolate a reach with fish proof nets and deploy electric fishing teams to catch and relocate fish out of the reach being dredged. This option may be workable in shallow, narrow water bodies but is not recommended for the Kaiapoi River for safety reasons. Risks would likely be considerable for personnel required to establish nets in the Kaiapoi River with its tidal current, likely 1-1.5m working
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 56 Status: FINAL depths at low tide (at least) and deep mud base. It is preferred that a fish management method is identified which minimises immersion of contractors within the river water for health and safety reasons.
In the Kaiapoi River, it will be feasible to install silt controls for identified sensitive habitat areas whilst simultaneously providing fish passage around the dredging equipment due to the width of the channel. The contractor will be asked to consider methods to prevent eels entering the suction dredge head and report any options identified in the Environment Management Plan for the consideration of the Council.
5.4.3 Effects of Heavy Metal Contamination
A NIWA report on “Copper and Zinc Aquatic Toxicity” May 2017 (attached) states that “at high concentrations, zinc reduces calcium uptake, leading to hypocalcaemia, reducing the ability of an organism to grow, reproduce and survive. Copper toxicity alters brain function, enzyme activity, blood chemistry and metabolism, leading to adverse effects on growth, reproduction and survival. At an ecosystem level, higher concentrations of copper and zinc can change the diversity of an ecosystem…” (p.12).
“Unlike other contaminants, metals do not breakdown over time. So all metals released in stormwater discharges will end up somewhere in the receiving environment. Various proportions will remain in the water column, accumulate in bottom sediments of streams and estuaries, build-up within organisms themselves. Copper and zinc can bioaccumulate over time in aquatic organisms (fish, shellfish, algae etc.), particularly filter feeders such as oysters and mussels. Although this does not usually cause problems for people consuming shellfish (because humans can tolerate relatively high concentrations of copper and zinc), such accumulation can cause chronic toxicity for those shellfish.” (p.12).
As discussed in previous sections, there is a low risk of the dredging and piling disbursing sediment containing heavy metals into the river system via a sediment plume or in dissolved form. There is a low risk of environmental contamination demonstrated by the river bed sediment sampling undertaken.
Any such dispersal of heavy metals that was within the suspended sediment or in dissolved form is likely to be rapidly diluted and disbursed by the tide. There would be unlikely to be any significant adverse effect on river habitat or aquatic species present due to the large flows in the lower Kaiapoi River, tidal action disbursing any contaminants, and interaction of contaminants with the salt water in this reach of the river which is likely to have a neutralising effect.
5.4.4 Overview of Effects on Aquatic Flora, Fauna and Habitat
The effects of the dredging operation in the lower Kaiapoi River area considered in this section to be no more than minor, due to: 1) the use of the cutterhead suction dredge method which has a lower likelihood of creating a sediment plume in the river channel than other available dredging methods; 2) existing width of the proposed dredging areas providing sufficient space around the dredging equipment for fish passage and fish escape; 3) the proposed sediment control methods in this application; and 4) the low risk of the river bed sediment being contaminated. The risks to aquatic fauna and habitat are therefore assessed as no more than minor.
5.5 Effects on Groundwater Quality
5.5.1 Protection of Groundwater whilst Dewatering Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 57 Status: FINAL
Dredging of sediment requires dewatering of dredged spoil with a return of dewatering water to the Kaiapoi River. These is a risk during the dredging that dewatered water could escape from the settlement pond and be conveyed and drained into land where it could enter and interact with groundwater.
Groundwater contamination during dewatering is not considered to be a significant risk. This is because the spoil contaminant testing has indicated there is a low environmental risk of contamination associated with the river bed sediment being used offsite at other locations.
Dewatering is proposed to be undertaken within a pond, lined with an HDPE liner which will be seam sealed and prevent leakage to surrounding land. This method will also protect against saline water entering land at the dewatering area.
Suction dredging requires large volumes of water to be abstracted and returned to the river, following water filtration provided by passing the abstracted water through a sediment detention pond during the initial stage of dewatering, prior to discharge. All dewatering will occur within confines of a temporary bund and pond at each site. The operation will involve routine checks of hoses and dewatering equipment to ensure any leaks or pumping problems are identified and promptly addressed.
The dredging may be required to be programmed during a period when there is no, or less, saline intrusion in the water column, coincident therefore with higher flows (during winter) in the Waimakariri River and Kaiapoi River catchments. Dredging may also occur in December if there is no saline intrusion evident at time of dredging. The dewatering water will be returned following treatment to the river, meaning that any salt content in the water will not affect the surrounding land.
At completion of dewatering, spoil will be retested for salt and other contaminants including metals, to determine its final use options. The retention of saline content in spoil may be desirable for fill used in some of the final spoil disposal locations and undesirable at some other locations as considered relevant for both proposed productive or non- productive land uses. This is due to the need to find long term land management options that do not require future herbicide use near waterways, which is an issue currently being consulted by Waimakariri District Council with the wider community through its Long Term Plan in March and April 2018.
5.5.2 Protection of the Shallow Gravel Aquifer whilst Piling and Dredging
Another risk is that deep dredging and piling into the riverbed sediments may intercept gravel and thereby intercept the shallow gravel aquifer, possibly causing an aquifer saline intrusion. The dredging may open up the river bed gravels and encourage saline waters to interact with the shallow gravel aquifer. Opening up those gravels would make a permeable sediment that salt could freely interact with or move through compared to river silts.
The dredging for the proposed floating pontoons may intercept gravels and could possibly intercept the shallow gravel aquifer.
Expert advice on this issue has been requested from Tonkin & Taylor, which will be provided shortly to support this application.
5.6 Effects on Lower Bank/ Stop bank Stability It is possible that deep dredging adjacent to structural features in and alongside the river including stopbanks, rock revetments, or adjacent to the wharf could undermine this infrastructure or undercut the lower river banks or stopbanks.
The recently completed river structural rock revetment adjacent to the wharf, and the proposed new sheet-piled river wall adjacent to the William Street Bridge (Pontoon 1) have been, or will be designed with bracing sufficient to ensure that lowering of the river bed during dredging will not adversely affect the stability of these structures. Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 58 Status: FINAL
No heavy machinery will be placed on the stopbanks during dredging, protecting them from damage during operations.
5.6 Effects on Air Quality This application identifies a risk of possible discharge to air of dust or odour.
It is noted sediment may become airborne during dewatering of stockpiles on the river bank, if these are left for a period long enough for the material to fully dry and then disburse from the site in dry or windy conditions. Airborne sediment can later settle onto surrounding ground or be conveyed back into the river through run off.
This risk is managed by proposing a dewatering method which would contain spoil and water during dewatering in sediment control ponds. As spoil dries and is transferred to storage, it would then be contained using an appropriate method. Spoil can be hydroseeded or contained with roading metal, aggregate or silt fences at any long term spoil storage site to ensure sediment is stabilised during windy conditions. There should be no impact on air quality and no discharge to air of dust during the activity.
Dust management methods associated with the stockpiling dewatering will be addressed in the Erosion and Sediment Control Plan which is to be developed by any contractor prior to undertaking the dredging and dewatering. This will be required to be submitted to the Council and/or Environment Canterbury as part of the contractor tender or other approval process.
Following establishment of the spoil storage site there is potential for a discharge of odour to occur. The Council will establish a complaints register associated with the operation of the spoil storage site. Complaints will be monitored and, if received, a Suitably Qualified and Experienced Person will be engaged to examine the nature and intensity of the odour and recommend mitigations.
On the basis of the mitigation proposed, the effects of dust or other odour nuisance is assessed as less than minor.
5.7 Effects on Human Health
Discharges or release of contaminated or hazardous substances or pollutants into the river during dredging can create a health risk to people harvesting mahinga kai or using any part of the river for recreational purposes. This application shows the river sediment, which has been tested for a range of environmental contaminants, is unlikely to pose any contamination risk and no specific human health risk associated with the extraction or handling of spoil has been identified.
However, the application includes surface water quality testing results, which shows bacterial contamination is present within the Kaiapoi River water.
The presence of high levels of bacteria in the river water should be taken into account in considering dredging designs that require any human contact with surface water. This application seeks to minimise human contact with the river water during dredging, to avoid risk of bacterial infection.
Any contractor undertaking piling and dredging excavations approved through this consent will be required to provide comprehensive health and safety procedures to be followed by staff. These are to include personal protective equipment, avoiding contact wherever possible with the Kaiapoi River water, and hazard minimisation procedures such as avoiding dermal contact or ingestion of water or spoil.
There is a drowning risk associated with undertaking activities within the river channel. This is due to the water depth at the proposed piling and dredging locations (1.5m depth or greater at each location), tidal currents and deep sediment on the river bed surface. Therefore this application does not recommend any activity that would require a person to
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 59 Status: FINAL wade into the channel and all interactions will if possible be undertaken from a barge surface or any other vessel/s supporting the dredging activity.
It is proposed to request the Coastguard support the piling and dredging operation and provide a safety response in the event of personnel falling into the river. They, or another contractor may be asked to assist to remove any debris from the bed of the river at the dredging area, if needed, immediately prior to commencement.
Spoil dewatering will involve large areas of land adjoining the river. Spoil is likely to be stockpiled in contained areas within sediment detention pond(s) to provide filtration of dewatering water, conveyed through a bunded dewatering pond to the collection point for discharge back to the river. It is recommended that these dewatering sites be fenced off during the dewatering operation to prevent public entry.
The design of the pontoons will also include elements to protect public safety. For instance, kick-rails will be included on each side of the Riverview pontoon. This will stop objects rolling off the deck, help to delineate the pontoon edge, prevent wheelchairs of other wheeled items from rolling off, and avoids trip hazards by accommodating deck hardware including mooring cleats. The kick rails will also help to strengthen the edge of the deck.
A gap will be maintained between the Riverview pontoon and new riverwall to reduce the risk of persons attempting to jump from the wall across to the pontoon at high tide. This gap will be wide enough to prevent entrapment, and is intended to reduce the likelihood and difficulty of removing debris that could accumulate in the gap, though debris accumulation should be mitigated by the debris deflector.
The inside edge of the pontoon could be potentially made available for additional storage of small dinghies or kayaks, though balanced against safety risks of pulling the vessels out of the gap at changed tidal levels.
The internal fairway/channel clearance in the river between the existing swing moorings and boats moored at the pontoon will be approximately 9 metres. This is based on two vessels of 5m beam (width) berthed parallel to each other, and includes allowance for vessels at the fore and aft mooring in the river centre to displace at mid to high tide levels.
The mitigations provided are considered suitable to protect human health during use of the pontoons, during dredging and during spoil dewatering. Therefore, effects on human health from the dredging activity are shown to be less than minor.
5.8 Heritage Effects
The proposed dredging activity will not have any effect on any heritage aspects or infrastructure of the Kaiapoi River. There are no heritage sites which would be affected by the dredging. The activity is also not within a Silent File area (see Appendix A, Plan of Silent File Areas).
However Council in all of its contracts requires that Contractors observe an Accidental Discovery Protocol through any excavation works.
Effects of the proposed dredging activity are therefore anticipated to be less than minor on historic heritage.
5.9 Cultural and Tangata Whenua Effects
No part of the proposed piling and dredging areas are located within a Silent File Area, as demonstrated in plan in Appendix A. The CIA also notes that there are no Archaeological Sites that are in vicinity of the proposed piling and dredging reaches.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 60 Status: FINAL It is proposed that the Accidental Discovery Protocol will be applied during all activities approved through this consent. In addition, a Cultural Monitor will be invited to be present at the commencement of the dredging at each site and will be able to work with the contractor to set up suitable sediment control measures in the river at the start of dredging at each targeted site.
Ngai Tuahuriri and Mahaanui Kurataiao Ltd representatives Bob Cox and Tui Maree Falwasser were both involved in developing the Kaiapoi River Rehabilitation concepts through their participation in the Kaiapoi River Rehabilitation Working Party from 2014 to 2016. They were both replaced in 2016/2017 by Amy Beran who now represents both organisations on the Working Party. Joseph Hullen prepared the Cultural Impact Assessment for the Kaiapoi River Rehabilitation Project, with assistance from Amy Beran from the Working Party.
The CIA lodged with the application describes cultural values associated with the Kaiapoi River (see Section 2, Description of the Environment) and mitigations including recommended sediment management measures which have informed the design of the activity (see Section 3, Description of the Activity). The effects of the proposed dredging on Ngai Tuahuriri values are described in the CIA and its recommendations included in the activity description section.
Effects on mahinga kai associated with the activity include the temporary possible disturbance of habitat during dredging. As it is proposed to undertake dredging outside of the Whitebaiting season and also avoid inanga (whitebait) spawning periods, it is considered that effects on values of Ngai Tuahuriri from the dredging activity will be no more than minor.
5.10 Consideration of Alternatives
5.10.1 Rationale for Dredging Areas of the lower Kaiapoi River downstream of the Williams Street Bridge to the Coastguard ramp will require dredging to enable establishment of pontoons and to establish a new deep area to enable berthing at the pontoons. The facility will enable easy public access to the river in the town centre for those using small vessels and provide a new area for short and longer term berthing.
The new floating pontoons will improve the appearance (amenity) and recreational values of the river in the town centre by concealing the currently exposed mudflats beneath the new pontoons and dredging the river bed to provide a deep docking and turning area.
The proposed floating pontoons are intended to complement the existing mooring and berthing options in the marine precinct. The design of the pontoons is intended to share some design features with the Riverview Terraces.
Potential alternative locations for the pontoons have been considered during 2017 within a series of meetings of the Kaiapoi Regeneration and Riverbanks Steering Groups. These meetings included consultation with key stakeholders and considered a number of scenarios for pontoon placement and dredging options. Other options for siting pontoons in downstream reaches of the river would not align with the riverbank terrace area development or provide access from the town centre precinct.
The proposed option has the broad political support of the Kaiapoi Community Board and wider community as indicated through ongoing project consultation. The option of not including floating pontoons in the river between the Coastguard ramp and the Williams Street Bridge would therefore maintain a status quo limited public access to the river which is currently monopolised by existing large vessels. The status quo option does not enable future access by other vessels than those already using the wharf or central moorings. Therefore the status quo option is not considered to have the support of the Kaiapoi community.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 61 Status: FINAL 5.10.2 Selection of Dredging Method
As indicated in the “Description of the Activity” section, options for dredging include:
• Long reach digger operated from the stopbanks • Long reach digger operated from a barge in the channel • Suction dredge operated from a barge in the channel.
In the Kaiapoi River the use of the long reach digger method from the stop banks has been discounted due to the risk of bank destabilisation.
The long reach digger method, whether operated form the banks or from a barge in the channel, is considered likely to release high suspended sediment concentrations in the vicinity of the digger bucket during dredging. This may however be able to be managed by use of sediment control fences within the water column around the dredge operation. The use of a long reach digger on a barge could possibly be carefully managed to avoid any associated safety and stability risks noted in Section 3 of this application. This method was not selected primarily due to the higher risks associated with the safety of dredging operations and of greater potential direct damage to river habitat, although it is noted these safety risks are able to be mitigated. The habitat risks may also be minor in context of the overall scale of dredging activity for the pontoons, and in relation to the background concentrations of sediment and turbidity in the lower river.
The recommendation for use of a “suction dredge” to undertake dredging in the Kaiapoi River has been developed in consultation with the Environment Canterbury River Engineering Department, whom have also been involved in developing engineering aspects of the application. The “suction dredge” method was also indicated to be preferred over the use of a long reach digger for dredging during preliminary discussions with an Aquatic Ecology expert Mark Taylor, whom has previously been engaged on various occasions to provide aquatic ecology and sensitive habitat advice to the Council. The Cultural Impact Assessment also specifically noted concerns with use of the long reach digger method.
The selected method of dredging identified for the proposed dredging in the Kaiapoi River is use of a pontoon with suction dredge and pump. Spoil would be piped onto adjoining land and dewatered, then collected for final disposal into the Kaiapoi Regeneration Zone. A suction pump has more control than the dragline or long reach digger methods in terms of precise sediment relocation and has reduced sediment discharge into the water column.
The Council, in preparing this application, has reviewed a recent Jacobs consulting report released on 16 October 2017, which considered feasibility of dredging work proposed by Christchurch City Council within the Heathcote River. The proposed dredging in this river is for the purposes of floodplain management rather than for a recreation use, but has provided useful information about dredging methods and options which have informed the “consideration of alternatives” within this application.
A suction dredge is considered a practicable, effective (from a river engineering perspective) and preferred environmental method of dredging. The suction dredge would lift sediment from the bed onto land and release much less sediment into the river water column in comparison with the use of a long reach digger. The suction dredge is proposed to be used in conjunction with a silt fence/s which could be deployed at locations up or downstream of the dredging where desired to protect sensitive habitats. The application of a silt fence is proposed to be used in consultation with the Environment Canterbury compliance staff and any Cultural Monitor appointed to observe the dredging by Mahaanui Kurataiao on behalf of Ngai Tuahuriri.
Options that would have been available in smaller streams such as creation of flumes (e.g. river water directed through a pipe to keep it separate from the dredging works) are not practicable in the Kaiapoi River due to its significant flow conveyance.
Other options such as coffer dams or aqua dams (temporary barriers around works to create a dry working area) are also not practicable due to water volumes in the river.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 62 Status: FINAL The Council will continue, if practicable, to seek opportunities to combine dredging works for the river navigation channel “high points” and pontoons as one project / contract, to improve operating efficiencies and minimise adverse effects on the river.
6.0 Recommendations for Mitigation
The proposed mitigations that are recommended to be included within the consent are outlined within the following table:
Potential Adverse Effect Proposed Mitigation Potential Outcome of Mitigation Release of sediment within the Silt fences in the river used to fence off TSS levels during dredging will be no river channel during dredging sensitive habitats greater than 150gm3 and less where possible, and only affect the river on Floating boom with silt fence around a temporary basis barge operation to contain suspended sediment Contractor to trial use of mud guard around suction hose mouth, if practicable Provide for a cultural monitor and other observers from DoC / other ecologists to provide advice prior to commencement of sediment control measures in the river Discharge of saline water to land Lining laydown area with seam sealed No saline material is inadvertently during dewatering HDPE liner, surrounded by a bund of at deposited on land; saline material is least 1m height during dewatering, to only deposited onto predetermined contain dewatering water and prevent suitable sites, for weed control disbursal to surrounding land purposes or for inert future Testing of salinity during dredging to infrastructure land use dredge in periods of fresh water as far as practicable
Disturbance of spawning sites Dredging and piling between 1 June to 15 Disturbance of fish habitat during and fish passage during August, to minimise overall disturbance dredging is kept at a minimum dredging of fish habitat Suction dredging method to be used, with lower likely impact on fish and habitat than the alternative long reach digger (backhoe dredge) option Consider with the contractor methods to prevent eels from being conveyed by suction into the dredge hose mouth and on into the dewatering area Health and Safety Any contractor will be required to provide No harm to human health will result comprehensive health and safety from any of the works. procedures to be followed by staff when undertaking works. These are to include specifications for encountering any contaminated materials, personal protective equipment, and hazard minimisation procedures such as minimising contact with river water.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 63 Status: FINAL Table 5: Summary of Proposed Mitigations
7. Applicable Regulatory Framework
7.1 National Policy Statement for Freshwater Management (2014) The National Policy Statement for Freshwater Management (2014) (NPSFM) sets out the objectives and policies for Freshwater Management in under the RMA.
The NPSFM provides guidance to local government about improving the management of the freshwater resource, as a matter of national significance. The NPSFM requires that regional Councils set limits for water quantity and quality in every catchment. Environment Canterbury, in order to implement these requirements within the Waimakariri District, is working with the Waimakariri Water Management Strategy Zone Committee to set nutrient and other contaminant limits which will be applied to the management of discharges into the Waimakariri District Council surface water bodies.
Of particular relevance to this application, the NPSFM (via regional councils) sets limits on resource use (e.g. how much of any particular contaminant can be discharged) to meet limits over time and ensure these continue to be met. The NPSFM requires these steps to be taken in order to protect the objectives of Section A of the NPFSM: the life-supporting capacity, ecosystem processes and indigenous species of freshwater and to safeguard the health of people who come into contact with water through recreation.
This application seeks to manage release of sediment plume into the Kaiapoi River and deploy sediment control measures in the river to manage disbursal of sediment and protect sensitive habitats, in order to meet requirements of the NPS for Freshwater Management. The application intends to undertake sediment control measures to keep TSS discharging into the river during dredging to levels of less than 150gm3, if practicable. It intends to contain any such sediment plumes where possible around the dredging operation, to be released in periods of greater background turbidity during higher flow periods. Any sediment plumes which are released into the river will be of short duration, similar to the sediment plumes released during other localised storm events.
This application intends to achieve the key purposes of the NPSFM - in terms of maintenance of life supporting capacity, ecosystem processes and indigenous species and health of people who come into contact with water through recreation.
The Kaiapoi River hosts a potentially significant salmon and whitebait habitat. It is important that the life-supporting capacity of the river is maintained. The proposed use of suction dredge for dredging in the river will have a lower environmental impact than other options for dredging and will minimise damage to the habitat of these fish.
Section B of the NPSFM contains provisions relating to water quantity, including the setting of flow and allocation regimes and ensuring that no decision will result in future over-allocation of the water resource. It is noted that the intended take of river water from the Kaiapoi River is non-consumptive as it is intended to return river water back to the river and is therefore consistent with the NPSFM water quantity objectives.
The RPS and LWRP are also consistent with the objectives and policies of the NPSFM, and are discussed in the sections below.
7.2 Regional Policy Statement
The Canterbury Regional Policy Statement sets out regional issues, objectives and policies for the management of freshwater resources which are relevant to the works proposed in this application.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 64 Status: FINAL
For instance, the Regional Policy Statement, Chapter 7, Policy 7.3.1 seeks to avoid “adverse effects of activities on the natural character of fresh water…”, including a need to “maintain natural character values where they are modified but highly valued”.
The proposal assists to achieve this policy by managing dredging so as to control and mitigate release of sediment into the river water, and proposes sediment control measures be used in the river to avoid release of a sediment plume, as far as practicable.
During spoil dewatering, clean, filtered river water will be discharged back into the river. The project is intended to be undertaken to have a minimal impact on the natural character values of this waterway.
Further, the Regional Policy Statement, Chapter 7, Policy 7.3.3 – Enhancing Freshwater Environments and biodiversity, requires that the Council and others “promote, and where appropriate require the protection, restoration and improvement of rivers, wetlands… to require the maintenance and promote the enhancement of indigenous biodiversity.”
The proposal assists to give effect to this policy by complementing the dredging activities with an aquatic intertidal planting programme which will provide benefits for habitat and indigenous biodiversity on the river margins.
7.3 Mahaanui Iwi Management Plan 2013
The Mahaanui Iwi Management Plan 2013 (IMP) sets out policies and objectives for managing natural waterways and avoiding contamination that are relevant to this application.
This application notes general opposition throughout the IMP to discharge of contaminants to water including discharge of contaminants to streams, rivers and the ocean.
Section 5.3 of the IMP, about “Wai Maori, has the objective (8) of “the practice of using water as a receiving environment for the discharge of contaminants is discontinued, and all existing direct discharges of contaminants to water are eliminated”.
More specifically with regard to sediment control measures during dredging, Policy WM12.8 “requires that all river works activity, including vegetation clearance and silt removal, are undertaken in a manner that protects the bed and margins of the waterway from disturbance, and that mahinga kai values are not compromised as a result of the activity”.
Sediment control methods will be undertaken during dredging to screen off any sensitive habitats identified by Ngai Tuahuriri and to seek to contain the sediment during dredging to a confined area within the river, to be released during peak flows when background sediment concentrations are higher.
The IMP also includes WM12.10: “to require the appropriate disposal of spoil (silt or weed) with a preference for the use of spoil as compost”. This is considered in the application in the planning to seek to re-use spoil in the Regeneration Zone for either non-productive uses (if salt is found to be present in the spoil) or for productive uses or planting and landscaping (if no salt is found).
The Council is also undertaking to work with Ngai Tuahuriri representatives, as recommended in the Cultural Impact Assessment (attached to this application), to also provide salt tolerant indigenous aquatic plant species in revegetating the margins of the lower Kaiapoi River through an ongoing planting programme. This is increasingly required as willows are removed (following damage from periods of saline intrusion) which have provided larger light wells in the river bed where indigenous species are now newly able to regenerate and repopulate exposed bare mud flats.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 65 Status: FINAL This will help to improve aquatic habitat in the river and is likely to increase abundance of mahinga kai by providing additional improved habitat for fish.
7.4 Waimakariri River Regional Plan The relevant objectives and policies of the WRRP are summarised below and an assessment of how the proposal is consistent with these policies and objectives is provided.
Objective or Policy How objective/policy will be met
Objectives 5.1 and Objective 6.1 Enable present and future generations to gain cultural, social, recreational, economic, health and other benefits The proposed activities will not discharge or release any from the rivers, lakes and wetlands in the Waimakariri saline water or contaminants to groundwater in the River Catchment while: Waimakariri River catchment. It will therefore not affect (a) Safeguarding their existing value for efficiently any human or stock drinking water supplies. providing sources of drinking water for people The dredging will be undertaken in a way that and their animals; safeguards the life supporting capacity, habitat, and (b) Safeguarding the life supporting capacity of the indigenous vegetation within the Kaiapoi River by using water, including its associated: aquatic suction dredge method and complementary sediment ecosystems, significant habitats of indigenous control measures in the river. fauna, and areas of significant indigenous Mahinga kai is safeguarded by avoiding dredging during vegetation; the inanga spawning and harvesting seasons. (c) Safeguarding their existing value for providing There will be no impact from the activities on wahi tapu mahinga kai for Tangata Whenua; or wahi taonga of value to Tangata Whenua, as (d) Protecting wahi tapu and other wahi taonga of identified in the Cultural Impact Assessment attached to value to Tangata Whenua; this application. (e) Preserving the natural character of rivers, lakes and wetlands and protecting them from The proposed activities will not change the natural inappropriate use and development; character of the river and there are no outstanding (f) Protecting outstanding natural features and landscapes or features which would be affected by the landscapes from inappropriate use and activities. subdivision. Amenity values will be impacted temporarily by the (g) Maintaining and enhancing amenity values presence of dredge in the river, but there will be no (h) Protecting the significant habitat of trout and effect beyond the immediate activity and improvement salmon in amenity at completion, once floating pontoons are established which will cover the exposed river bed and improve appearance of the river within the town centre. The activities will not be undertaken in any trout or salmon spawning area and significant habitat for these species is provided in the upper Kaiapoi River upstream of the dredging areas. Fish passage to the sea will be maintained during the period of dredging and any sensitive habitat areas on the river margins can be protected using silt fences.
Policy 6.1 Set and maintain water quality standards for, and The proposed activities will not release any control the discharge of contaminants into, surface contaminants into river water or hydraulically water bodies in the Waimakariri River Catchment….. to: connected groundwater. It will avoid affecting any fish Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 66 Status: FINAL Objective or Policy How objective/policy will be met
(c) ensure water quality is suitable for drinking water for spawning habitat and will maintain fish passage in the animals, fisheries, fish spawning, aquatic ecosystems river. It will not cause salination of any water source and is not altered in those characteristics that have a used as drinking water by animals. direct bearing upon the aesthetic values of water, in the Kaiapoi River …. and tributaries; Objective 7.1 The proposed activities will safeguard the life- Enable present/future generations to gain cultural, supporting capabilities of the Kaiapoi River by use of social, recreational, economic, health and other benefits suction dredge method that minimises effects on from river beds in the Waimakariri River catchment habitat in the river bed. while: (a) safeguarding the existing value of rivers and There are no identified archaeological sites as indicated lakes for efficiently providing sources of in the Cultural Impact Assessment of importance to drinking water for people and their animals; Ngai Tuahuriri that would be affected by the proposed (b) safeguarding the life-supporting capacity of the activities. water in the beds of rivers…, including its associated: aquatic ecosystems, significant Wahi tapu and wahi taonga, if identified in the river habitats of indigenous fauna, and areas of during dredging will be protected by application of the significant indigenous vegetation. Accidental Discovery Protocol. (c) Safeguarding the existing value of rivers and Mahinga kai values will be protected by avoiding lakes for providing mahinga kai for Tangata excavations within the whitebaiting season from 15 Whenua; August to 30 November. (d) Protecting wahi tapu and other wahi taonga of value to Tangata Whenua; There will be no effect on natural features or (e) Preserving the natural character or rivers….and landscapes within the river. protecting them from inappropriate use and
development; The placement of pontoons and continuation of (f) Protecting outstanding natural features and intertidal aquatic plantings will both improve amenity landscapes from inappropriate use and values of the Kaiapoi River. development;
(g) Maintaining and enhancing amenity values; The dredging will marginally deepen the channel which (h) Protecting and where appropriate enhancing will slightly improve flood conveyance capacity. the habitat and heritage value of river beds; The dredging as proposed will minimise risk of erosion (i) Protecting and where appropriate enhancing the of the river banks by avoiding any intrusion into or flood carrying capacity of rivers; placement of heavy equipment on the river banks. (j) Protecting the banks of rivers…and the stability The spawning habitat of trout and salmon in the upper and performance of essential structures in their Kaiapoi River will not be affected by the proposals. beds; (k) Protecting the significant habitat of trout and salmon. Policy 7.1 Control in the bed of any river … in the Waimakariri River Catchment: (a) The use, erection, reconstruction, placement, The proposed excavation of the river bed and alteration, extension, removal or demolition of placement of pontoons on the bed will be controlled any structure or part of any structure in, on, through the consent process in order to meet objective under or over the bed; 7.1, noting the activity will marginally improve flood (b) The excavation, drilling, tunnelling, or other conveyance capacity in the river, protecting against disturbance of the bed; flood hazard to adjacent land, whilst using suction dredge on the river bed to minimise potential
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 67 Status: FINAL Objective or Policy How objective/policy will be met
(c) The introduction or planting of any plant or disturbance to wildlife, breeding habitats or indigenous any part of any plant (whether exotic or vegetation. indigenous) in, on, or under the bed;
So that (a) to (k) of objective 7.1 are achieved and in particular: (i) The flood hazard to adjacent land is not increased; (ii) Disturbance to protected wildlife and their breeding habitat, and indigenous vegetation is minimised;
7.5 Canterbury Land and Water Regional Plan The Canterbury Land and Water Regional Plan (LWRP) contains a number of policies relevant to the abstraction of surface water and discharge of contaminants into the receiving environment. The LWRP gives effect to the RPS.
The relevant objectives and policies of the Canterbury Land and Water Regional Plan (LWRP) are summarised below and an assessment of how the proposal is consistent with these policies and objectives is provided.
Strategic Policies
The following table includes extracts for reported parameters for freshwater outcomes for urban spring fed plains streams provided in the Land and Water Regional Plan.
Table 1a Freshwater Outcomes for Canterbury Rivers
Condition Rural / Urban Spring Fed Stream Compliance
Total Macrophytes Rural 50 % / Urban 60% Complies Maximum bed coverage The proposed dredging is not in areas with any current macrophyte coverage in the river bed. Siltation Fine sediment <2mm diameter Does not comply There is heavy fine sediment coverage of Maximum cover of bed the bed of the lower Kaiapoi River. The Rural 20% / Urban 30% limited areas of sediment removal will reduce depth to gravel at the dredge locations. However turbidity in the river is expected to temporarily increase during the dredging period. Dissolved oxygen Minimum saturation of 70% Complies The proposed activities will not affect dissolved oxygen saturations in the river water.
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 68 Status: FINAL Condition Rural / Urban Spring Fed Stream Compliance
Temperature Maximum temperatures of Complies 20degrees Celsius The proposed activities will not affect temperatures in the river water. Periphyton Filamentous algae >20mm Complies Maximum cover of bed of 30% The proposed activities will have no effect on any present filamentous algae in the Kaiapoi River. Cyanobacteria mat cover <50%
QMCI* QMCI Minimum score Complies The Quantitative Macroinvertebrate Rural = 5 Community Index (QMCI) shows poor Urban = 3.5 invertebrate health in the lower Kaiapoi River (see description of the environment section). The dredging will have a temporary adverse effect on invertebrate habitat in the lower river. This will be mitigated by the creation of new habitat for invertebrates in the river at completion, due to new deeper water areas and associated intertidal planting on the river margins.
8. Description of Consultation Undertaken
8.1 Consultation with Residents
This application has been developed taking account of public feedback on the condition of the Kaiapoi River within the town centre, and associated navigation and public access improvement options and opportunities over a number of years.
Consultation for the floating pontoons installation and associated river dredging was undertaken through the Regeneration Zone and Kaiapoi Riverbanks Steering Groups from November 2015. Floating pontoons were included conceptually in the overall masterplan for the wharf and marine precinct project area and presented initially to the Riverbanks Steering Group in November 2015, where significant support for the project was indicated.
The proposed floating pontoons are intended to complement the existing mooring and berthing options in the marine precinct. It is hoped they will invite people into the marine precinct area and make it more user friendly. The pontoons would be primarily designed to be used by boats up to 10 metres in length. This would not preclude larger vessels from also berthing, depending on their specific dimensions, but the new pontoons would have a clear benefit in providing new berthing and mooring options for smaller vessels in the town centre. The concept has received growing support of both Steering Groups since 2015 and has continued to be developed into the current detailed design phase.
The Kaiapoi River Rehabilitation Working Party also has, since 2014, been investigating proposals for improving water quality, navigability, flood hazard management, amenity and recreation in the Kaiapoi River. All of its proposals, including providing a minimum 1.5m depth navigation channel were widely publicly consulted within the Kaiapoi community, during the period April to May 2017. The proposals were consulted with a Centrespread in the Kaiapoi Advocate newspaper on 7 and 21 April 2017, with brochures widely circulated around community facilities and on Open Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 69 Status: FINAL Day held on 27 April 2017. The public consultation for the proposed minimum 1.5m depth navigation channel also included the areas where it was proposed to dredge the river at the wharf to allow berthing for proposed new floating pontoons and consulted all of these dredging options and locations which would provide some form of navigability improvements in the river as one “wider” navigation dredging project.
Environment Canterbury: The Council consulted Environment Canterbury on its approach for preparing the consent applications to dredge the river bed in order to provide a berthing area for vessels using the proposed new pontoons and the minimum depth navigation channel through involvement of Environment Canterbury Commissioners and staff in the Kaiapoi River Rehabilitation Working Party. Commissioners involved in scoping the project were Rex Williams and Claire McKay.
Environment Canterbury staff involved in scoping the project and providing ongoing advice in terms of dredging methods and options include Brian McIndoe, John Ellis (River Engineers), Jim Dilley (Harbour Master), Adrian Meredith (surface water scientist) and Andrew Arps (Zone Manager).
Fish and Game:
Fish and Game were contacted about proposed dredging timeframes during the application drafting period. No response has been received at the time of application lodgement.
Department of Conservation:
Department of Conservation made the following comments in an email received on 28 March 2018.
The District Council asks:
Dredging is likely to be proposed to occur during the period from June to 15 August in any year, which avoids the inanga spawning and harvesting seasons Can you advise of any other periods of the year when dredging would be considered more suitable/less damaging to fish species and spawning sites Feedback about possible effects on fish or invertebrate species in the river Feedback on other activities in and around the river which could be affected by the proposal
Department of Conservation Responds:
1. The areas are right in the middle of ECAN Inanga Spawning Habitats and near known inanga spawning sites as included in plan change 4 to the Land and Water Regional Plan (Map attached). Impacts will not be avoided just by not doing works at specific times as pointed out with ECAN’s request for non-notified consent to do river engineering works within the Plan’s Inanga Spawning Habitats. There are significant areas of river bed and banks being removed. These will have been providing fish and bird habitat and altering flow and tidal inundation (i.e. high tides critical for inanga spawning) patterns upstream and downstream.
2. Refer to the attached table done for Canterbury rivers. We have traditionally concentrated our efforts around avoiding peak whitebait migration times and spawning period of Inanga with a month post spawning to protect eggs as they incubate.
3. Large removal of fish, invertebrate and bird habitat in an area of high diversity (probably a lot of marine migrants using area too which aren’t often sampled) and high numbers of migrating fish (some recorded in NZFFD (map attached) but not an area of rivers that is well sampled though). Majority of invertebrate and fish habitat is on littoral margins of
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 70 Status: FINAL rivers which will be removed as the river is made into a simple U shaped channel best for navigation (and as dogma goes flood passage). It would be expected that an AEE will be done detailing existing fish and Benthic Macroinvertebrates, including kakahi and koura and quantity of their habitat that will be lost and how this will be mitigated.
4. Recreational access to the river is aided by gravel bars and natural gently sloping banks that will be removed by proposed works.
5. Natural character will be impacted i.e. River Natural Character Index (Innovative River Solutions Centre, Massey). Mahinga kai.
6. Around the mouth of the Kaipoi River is prime BITTERN habitat so avoiding the breeding season of Sept to Dec is also needed.
7. Attached are the Fish Salvage BP via CCC to strengthen the obligations for people to take more care to ensure fish kill or removal is avoided and seems to have an emphasis on indigenous fish. It combines all relevant legislation including the Fisheries Regulations 2003, Fisheries Act 1996 , RMA and Conservation Act 1987.
This application notes that the area of proposed dredging for the pontoons (as opposed to the navigation channel which is to be covered in a separate application) is within a highly modified area around the wharf, adjacent to an existing concrete wall and rock revetment structure. No area of natural character, spawning site or spawning habitat will be impacted by the pontoon area dredging as no riparian margin vegetation is present around the area to be dredged.
The habitat areas and spawning site implications noted in the DoC response email will be discussed in the separate resource consent application regarding the proposed navigation channel dredging, which includes proposed dredging adjacent to areas with established riparian vegetation which is more likely to provide the habitat for spawning referred to in the email. There is no natural, gradual recreational access into the river at the pontoon site as there are no sloping gravel bars at the dredging location for the pontoons.
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Indicative Location Plan Kaiapoi River
Source: AEL 2012, p.31
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Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 75 Status: FINAL APPENDIX C: Proposed Dredging at Wharf Location Plans
Pontoon 1
Pontoon 2
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 76 Status: FINAL Plan of Proposed Pontoons Dredging with River Bed Levels
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 77 Status: FINAL APPENDIX D: INDICATIVE SPOIL DEWATERING PLANS
Stage 2: Longer Term Dewatering Area: Open for Evaporation (liner may be required – subject to saturation level of sediment)
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Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 79 Status: FINAL APPENDIX E: FISH MIGRATON CALENDAR
Kaiapoi River Dredging Consent Application: Berthing at Floating Pontoons Page 80 Status: FINAL Annual Fish Migration Calendar (Source AEL 2012, p.4)
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