IN THE MATTER of the Resource Management Act 1991

Transcription

1 BEFORE THE NORTHLAND REGIONAL COUNCIL IN THE MATTER of the Resource Management Act 1991 AND IN THE MATTER APPLICATION of a resource consent application by The New Zealand Refining Company Limited under section 88 of the RMA to deepen and realign of the Whangarei Harbour entrance and its approaches APP COMMENTARY ON PROPOSED TURBIDITY MONITORING RICHARD GRIFFTHS NRC MARINE RESEARCH SPECIALIST REGULATORY SERVICES 1.0 INTRODUCTION 1.1 This written statement has been prepared by Richard Griffiths, Marine Research Specialist Regulatory Services for the Northland Regional Council in response to the proposed turbidity monitoring conditions for the Refining NZ Crude Shipping Project. 1.2 I am a Marine Research Specialist, with Northland Regional Council (Council). I have been employed by Council since January I am responsible for Council s coastal State of the Environment Monitoring programmes, including water quality programmes in Whangarei Harbour, Bay of Islands, Kaipara Harbour and Mangawhai Harbour, and sediment monitoring programmes in Whangarei Harbour and Bay of Islands. I have also implemented an estuarine monitoring programme to assess the ecosystem health of Northland s estuaries. I am responsible for Council s investigation of sediment accumulation rates in Northland estuaries. I also carry out consent compliance monitoring and investigate coastal incidents. 1.3 I have previously worked for Auckland University Services, where I conducted estuary monitoring programmes for Auckland Regional Council (now Auckland Council) and undertook shellfish stock assessments for the Ministry of Fisheries (now Ministry of Primary industries). 1.4 I have previously worked in inshore fisheries management in the UK, and in London for as an environmental consultant. 1.5 I hold a Masters degree in Marine Environmental Protection, from the University of Wales, Bangor, UK. Purpose and Scope of Statement 1.6 Mr Mortimer, NRC s42a Reporting Officer, has advised me that the Hearing Commissioners wish to hear my opinions on the following: the appropriateness of NTU management trigger levels in proposed Condition 81 when compared with background levels derived from NRC monitoring records for the harbour entrance sites; the calculated 80 th, 90 th and 95 th percentile values from the NRC data which might be used to replace the proposed Level 1, 2 and 3 values; 1

2 the usefulness of control/reference site(s), and where this (these) might be located, to allow direct comparison of dredging/spoil disposal activity with background levels; 1.7 This statement also comments on the need for water clarity standards (turbidity, total suspended solids and secchi depth) at the edge of the mixing zone for dredging (condition 84) and for the disposal of dredged material (conditions 90-94). I also recommend that a closed season for dredging activity be included in as per other recent resource consents issued by NRC for dredging activity. Code of Conduct 1.8 I confirm that I have read the Code of Conduct for Expert Witnesses contained in the Environment Court Practice Note (2014) and have sought to comply with it in the production of this written statement. 2.0 Water quality in the vicinity of the proposed activity 2.1 Northland Regional Council has been collecting routine State of the Environment (SOE) data at 16 sites in the Whangarei Harbour every two months (in January, March May, July, September and November) since March Sampling is conducted on a predetermined date to co-inside with Council s River Water Quality Monitoring Network. Since I have worked at Council, the Whangarei run has to my knowledge only been cancelled once due to high winds. Samples are collected from the top 50 cm of the water column (surface samples). 2.2 There are a number of sites in the vicinity of the proposed activity. The closest sites to the proposed activity are Mair Bank, Marsden Point, and Snake Bank. Three different measures of water clarity have been collected (turbidity, total suspended solids and secchi depth). Turbidity and secchi depth have been collected since March Total suspended solids has been collected since in November Results from the three closest monitoring sites indicate that water clarity in the vicinity of the proposed activity is very good (Griffiths, 2015). The median turbidity reported at Mair Bank between was 0.6 NTU. The maximum turbidity recorded was 2.7 NTU. 2.4 The local flora and fauna will be adapted to good water clarity (and low levels of suspended solids) and may therefore be more vulnerable to poor water clarity. Increased suspended sediment concentrations can restrict light transmission in the water column and thus affect the amount of photosynthesis (primary production) of aquatic plants. Seaweeds and seagrass, typically require more light for photosynthesis than phytoplankton and are particularly susceptible to increased concentrations of suspended sediments by nature of being attached to the seabed (Thrush et al., 2004). Increased concentrations of suspended sediments can also have negative impacts on suspension feeding animals, by clogging feeding structures, interfering with particle selection and requiring the use of energy to clear away unwanted particles (Thrush et al., 2004). Increased concentrations of suspended sediments can also negatively impact the abundance and diversity of fish assemblages by clogging gills and reducing feeding efficiency. 2.5 I do not know how the values in proposed condition 81 were derived, so I cannot comment on the methodology used. However, Council s state of the environment data suggests that the values proposed in condition 81 are significantly higher than those typically encountered in the vicinity of the proposed activity. As previously stated, the median turbidity at Mair Bank was 0.6 NTU and the maximum value was 2.7 NTU (Griffiths, 2015). 2

3 2.6 Furthermore analysis of all of council s SOE data from other sites in the Whangarei Harbour, Bay of Islands, Kaipara Harbour and Mangawhai, including sites in more turbid tidal creek environments, indicates that turbidity values of >15 NTU are extremely rare. For example, turbidity at a site in the Town Basin in the upper Hātea River, only exceeded 15 NTU on two occasions between March 2008 and January 2018 (62 sampling events). 3.0 Options to develop exceedance values 3.1 As there is an existing scientifically robust long term water quality data set in the vicinity of the proposed activity, one option is to develop trigger values from that data. 3.2 The ANZECC 2000 guideline document (Australian and New Zealand Environment and Conservation Council 2000) outlines the preferred approach to deriving trigger values as follows: 1) use of biological effects data, 2) then local reference data (mainly physical and chemical stressors) and finally (least preferred) 3) the tables of default values provided in the guideline document (Griffiths 2016). The ANZECC 2000 guidelines recommend that trigger values for physical and chemical stressors for Condition 2 ecosystems be defined in terms of the 80 th percentile. 3.3 Between March 2008 and March 2012 the majority of turbidity values were censored (i.e. they were below the laboratory detection limits <2 NTU) so I have omitted these from the analysis. To avoid any potential bias from seasonality, I have only included complete calendar years for analysis. The analysis was therefore performed on data collected between January 2013 and December 2017 (five complete years of data). I performed this analysis on data from just the site at Mair Bank and then repeated it using data from Mair Bank, Marsden Point and Snake Bank. The results are presented in Table 1. Table 1: The 80 th, 90 th 95th percentiles derived from reference data for turbidity (NTU). Site Samples 80 th 90 th 95 th Mair Bank Mair Bank, Marsden Point and Snake Bank Total suspended solids has only been collected since November Again, to avoid any bias from seasonality I have only included complete calendar years for analysis. The analysis was therefore performed on data collected between January 2015 and December 2017 (three complete years of data). I performed this analysis on data from just the site at Mair Bank and then repeated it using data from Mair Bank, Marsden Point and Snake Bank. The results are presented in Table 2. Table 2: The 80 th, 90 th 95th percentiles derived from reference data for suspended solids (mg/l). Site Samples 80 th 90 th 95 th Mair Bank Mair Bank, Marsden Point and Snake Bank The results suggest that there is very little difference in turbidity or total suspended solids between the three locations. For simplicity, I therefore recommend one set of values for the six locations in condition 81. If three different exceedance values are required, I recommend that the values in Table 3 be utilised. 3

4 Table 3: Recommended exceedance values based on reference data. Parameter Level 1 Level 2 Level 3 Turbidity (NTU) Total suspended Solids mg/l As the turbidity values are very similar for each exceedance level, a simpler approach would be to have just one exceedance level (i.e. turbidity 2.7 NTU and total suspended solids 14.7 mg/l). In the event of an exceedance, dredging should cease in the current dredging area (as per plan 4782/1). Dredging could continue in a different dredging area with the permission of the council s Compliance Manager. 3.7 Another approach would be to install an additional turbidity sensor at a control/reference site and base an exceedance value on a percentage change relative to the reference site. This is the approach recommended by Morrisey and Barter (2015) in their review of Northland Regional Council s consent conditions for dredging. This is also the approach adopted in all other recent dredging consents issues by Council. They recommended: The suggested guideline for the middle and lower harbour is no more than 33% relative to background clarity at the time of monitoring to protect aesthetic, water quality for contact recreation, and habitats and organisms sensitive to elevated suspended solids and reduced clarity (seagrass and shellfish beds, encrusting biota of rocky reef). and added that: The possible exception to the previous guideline for the lower harbour is Motukaroro Marine Reserve. This area protects a diverse and abundant fish fauna, macro algal beds and assemblages of filter-feeding organisms) including anemones, sponges and ascidians). These organisms are likely to be sensitive to suspended solids and the site is popular with divers, for whom water clarity is an important feature. For this area, a maximum reduction in clarity of 20% relative to background clarity at the time of monitoring may be appropriate. If this approach was adopted, I recommended utilising the exceedance values in Table 4. Table 4: Recommended exceedance values based on relative change from a reference site. Location Motukaroro Island Marine Reserve M1MA** Calliope Bank M1MA* Mair Bank M1MA* Home Point M1MA** Bream Bay including Three Mile Reef* Disposal Site 1.2* Exceedance level 20% change from background 33% change from background 3.8 A suitable reference site could be located in the southern portion of Bream Bay towards Waipu Cove or within the Whangarei Harbour at Snake Bank. 4

5 4.0 Conditions In addition to my concerns about the proposed turbidity values, as it is currently written conditions 81 and 82 are not enforceable consent conditions. In the event of a Level 3 exceedance, condition 82 states that dredging activity within 300m of the relevant turbidity sensor shall cease. Taken literally, the dredge only has to move 300m away from the sensor to comply with this condition, even if the sensor continues to show a Level 3 exceedance. I recommend that the wording or condition 82 be altered to read: (c) Level 3: dredging activity shall cease in the current dredging area (Plan number 4782/1). Dredging may continue in a different dredging area, with the permission of the council s Compliance Manager. 4.2 In addition, condition 84 should include standards for turbidity, total suspended solids or secchi depth in order to protect ecological values at the edge of the mixing zone. All of Council s recent dredging consents stipulate standards for secchi depth, turbidity and suspended solids at the edge of the mixing zone. 4.3 I also recommend that these standards are included within the condition itself rather than as a Schedule. I suggest that the standards reflect the recommendations made by Morrisey and Barter (2015) and mimic recent dredging consents issued by Council. I recommend that the following standards be included in the condition. 84 The exercise of these consents shall not result in any of the following effects on coastal water quality, as measured at or beyond a 300 metre radius from the dredger: (a) (b) (c) (d) (e) (f) (g) (h) The visual clarity, as measured using a Secchi disk, shall not be reduced by more than 33% of the background visual clarity at the time of measurement; and The turbidity of the water (Nephelometric Turbidity Units (NTU)) to be increased by more than 33% of the background turbidity at the time of measurement; The Total Suspended Solids shall not exceed 40 grams per cubic metre above the background measurement; and The natural water temperature shall not be changed by more than 3 degrees Celsius; and The natural ph of the waters shall not be changed by more than 0.2 units; and The dissolved oxygen content in solution in the waters shall not be reduced below 5 grams per cubic metre; and The production of any conspicuous oil or grease film, scums or foams, or floatable or suspended materials, or emissions of objectionable odour; and There shall be no destruction of natural aquatic life by reason of a concentration of toxic substances 4.4 There are currently no water quality standards associated with the disposal of dredged material (AUT , AUT , AUT and AUT Marine Dredging Spoil Disposal - Conditions 90-94). In my opinion, there is a much higher risk of elevated turbidity and suspended solids at the dredge disposal site that at the dredging site so it is imperative that the standards recommended above for condition 84 implicitly relate to the disposal of dredged material. If necessary these standards could be repeated as an additional condition for dredging spoil disposal. 5

6 5.0 Closed seasons 5.1 Finally, I recommend that the consent include temporal restrictions on dredging activity. This was a key recommendation of the Cawthron Institute s report to Council on dredging conditions for resource consents (Morrisey and Barter, 2015) and closed seasons have been included in all other dredging consents issued after this report was published, including a dredging consent recently issued to the New Zealand Refining Company LTD. Morrisey and Barter (2015) recommend a closed season from October to January (inclusive) for areas in the vicinity of Snake Bank, Blacksmith Creek, NZRC Jetty (Marsden Point) and Mair Bank. 5.2 I strongly recommend that a condition for a closed season be included in the consent, to protect the values identified by Morrisey and Barter (2015) and to be consistent with other consents issued by Council. The recommended closed season of October to January also co-insides with a period of high recreation use where expectations for aesthetic values are at their highest. 5.3 Consents including a closed season include: AUT (Whangarei District Council - Hātea River Dredging) issued June 2015 AUT (McRaes Hātea River dredging) issued March 2016 AUT (New Zealand Refining Company Ltd Capital Dredging Dolphin A7) issued November 2017 AUT (New Zealand Refining Company Ltd Maintenance Dredging Dolphin A7) issued November 2017 AUT (Oceania Marine Ltd) issued December New Zealand Refining Company Sonde data 6.1 I only received this data late on Tuesday and I have been in the field sampling this week so I have only had chance to do some preliminary analysis of the data. 6.2 I cannot comment on the calibration or validation methods used, as I have not seen these. I will note however that validation samples are essential to ensure the quality of the data collected and to establish whether there has been any instrument drift or interference from biofouling organisms. When Council deploys SONDEs we collect a validation sample when we deploy the SONDE and another when we retrieve the SONDE. If the SONDE is deployed for more than one month s we will also collect an additional validation sample. 6.3 I do not know the depth of the sensors on the Sonde. Normally it is necessary to position the sensors relatively deep in the water column due to interference from waves and currents with the buoy structure. Because of this, the sensors on Council s Sonde are positioned at a depth of 80cm. 6.4 There appear to have been three deployments. The first deployment was made between 10/05/2017 and the 11/07/2017. The second deployment was made between 10/08/2017 and 09/09/2017 and the third deployment was between 15/09/ /10/2017. There were no deployments during the summer months so there is likely to be some seasonal bias in the data. 6

7 6.5 The turbidity data from the second deployment appears to be elevated relative to the first and third deployments. I would question whether the instrument was calibrated correctly before deployment, so I have ignored this data set. 6.6 The first deployment lasted 62 days. A total of 5926 measurements were made. The median turbidity was 2.69 NTU. Only 160 of the 5926 measurements exceeded a turbidity of 15 NTU (2.7% of measurements). The 80 th 90 th and 95 th percentiles from this deployment are presented in Table 5. Table 5: The 80 th, 90 th 95th percentiles derived from SONDE data between 10/05/2017 and 11/07/2017 for turbidity (NTU). Site Measurements 80 th 90 th 95 th New Zealand Refinery Ltd SONDE The last deployment lasted 33 days. A total of 2669 measurements were made. The median turbidity was 0.5 NTU. Only 26 of the 2669 measurements exceeded a turbidity of 15 NTU (0.8 % of measurements). The 80 th 90 th and 95 th percentiles from this deployment are presented in Table 6. Table 6: The 80 th, 90 th 95th percentiles derived from SONDE data between 15/09/2017 and 19/10/2017 for turbidity (NTU). Site Measurements 80 th 90 th 95 th New Zealand Refinery Ltd SONDE Results from New Zealand Refining Company LTD Sonde data also indicates that water clarity in the vicinity of the proposed activity is very good and that turbidity values >15 NTU are rare. 6.9 The 80 th, 90 th and 9 5th percentiles from the last deployment in autumn 2017 are very similar to the values derived from Council s long term data set (Table 1). The 80 th 90 th and 95 th percentiles from the first deployment (spring) are noticeably higher than both the last deployment and Council s long term data set. It is unfortunate that the data from the second deployment (winter) is not useable and that a deployment during the summer was not undertaken. Richard Griffiths BSc, MSc 23 rd March

8 References Australian and New Zealand Environment and Conservation Council (1992). Australian water quality guidelines for fresh and marine waters. National Water Quality Management Strategy Paper No 4, Australian and New Zealand Environment and Conservation Council, Canberra. Griffiths R. (2015). Coastal water quality in Northland: results. Northland Regional Council, Whangārei. 60p. Griffiths R. (2016). Recommended Coastal Water Quality Standards for Northland. Northland Regional Council, Whangārei. 68p. Morrisey, D. and Barter, P. (2015). Review of Northland Regional Council s consent conditions for dredging. Prepared for Northland Regional Council. Cawthron Institute Report No p. Thrush, S.F., Hewitt, J.E., Cummings, V.J Muddy waters: elevating sediment input to coastal and estuarine habitats. Front Ecological Environment 2 (6):