Blenheim Sewage Treatment Plant Annual Consent Compliance Report - April February 2014

Transcription

1 Report Blenheim Sewage Treatment Plant Annual Consent Compliance Report - April February 2014 Prepared for Marlborough District Council (Client) By CH2M Beca Limited 5 May 2014 CH2M Beca 2014 (unless CH2M Beca has expressly agreed otherwise with the Client in writing). This report has been prepared by CH2M Beca on the specific instructions of our Client. It is solely for our Client s use for the purpose for which it is intended in accordance with the agreed scope of work. Any use or reliance by any person contrary to the above, to which CH2M Beca has not given its prior written consent, is at that person's own risk.

2 Revision History Revision Nº Prepared By Description Date A Jen Johnstone Draft for MDC review 11 April 2014 B Jen Johnstone Final 5 May 2014 Document Acceptance Action Name Signed Date Prepared by Jen Johnstone 5 May 2014 Reviewed by Bridget O'Brien 5 May 2014 Approved by Bridget O'Brien 5 May 2014 on behalf of CH2M Beca Limited CH2M Beca // 5 May 2014 // Page i

3 Table of Contents 1 Introduction Purpose of Report Background Consent U Domestic Ponds Discharge to Opawa River Consent Purpose Condition 37 Effluent Quality Monitoring Condition 38 Effluent Quality Requirements Condition 39 Receiving Environment Monitoring Condition 40 Receiving Environment Quality Condition 41 Reporting Consent U Industrial Ponds Discharge to Wairau River Estuary Consent Purpose Condition 4 Annual Monitoring Report Condition 8 Effluent Quality Condition 9 Effluent Quality Limits Condition 11 and 12 Effects of the Discharge Condition 13 Exceedances of Consent Limits Discussion and Conclusions Overview Domestic STP - Consent U Industrial Ponds - Consent U Appendices Appendix A - Site Plan and Outfall Monitoring Location Appendix B - Monitoring Results CH2M Beca // 5 May 2014 // Page ii

4 1 Introduction 1.1 Purpose of Report The purpose of this report is to compare the discharges from the Blenheim Sewage Treatment Plant (BSTP) with the conditions of the following consents for the period 1 April 2013 to 5 February 2014: Consent U authorises the continued discharge of treated wastewater to the Opawa River (from the Domestic System ) until 4 October Consent U071181, Condition 47 of Specific Conditions (Part III) states: The conditions of consent U as shown in Appendix 2 to these conditions of consent will remain in force and will apply to this consent until the wetland is established and the new outfall pipeline is completed so that the Opawa outfall is able to be decommissioned. The discharge to the Opawa River ceased on 5 February 2014, when the discharge was changed to utilise the new wetlands and outfall to the Wairau Estuary. Consent U permits the continued discharge of treated effluent into the Wairau Estuary (the Industrial System ) until 1 October 2013 or until the new wetland and outfall are commissioned, whichever is the earlier. Consent U allows the discharge of treated industrial wastewater to land. This consent expired on 1 October 2011, and has not been used in the reporting period. Therefore compliance with this consent will not be assessed in this report. The BSTP and outfall sampling locations are shown in Appendix A. Some of the consent conditions do not have on-going monitoring requirements, and are not covered in this report. Only those conditions that have numerical or qualitative monitoring requirements are assessed. For clarity, consent conditions are quoted in italics, with other commentary in normal font. 1.2 Background Existing Treatment Systems Marlborough District Council (MDC) owns and operates the BSTP at Hardings Road, which treats wastewater from the residential and commercial premises (termed domestic flows), from within the Blenheim urban area, as well as industrial flows and tankered wastes. The BSTP consists of two separate treatment systems. A fine screen, as well as facultative and maturation ponds, are used to treat domestic flows while the industrial stream is treated using fine screening and mechanically aerated and facultative ponds. During vintage, industrial wastewater is redirected through twin DAF units for solids separation and recycling to create an activated sludge process. Schematics of the treatment systems are shown in Figures 1.1 and 1.2. CH2M Beca // 5 May 2014 // Page 1

5 Figure Domestic Wastewater Flow Schematic Industrial Wastewater Inlet Screen Float Sludge Recycle Aerated Pond I2 45,800 m³ 1401 kw aeration Non-vintage bypass Facultative Pond 6 18 ha 223,000m³ 35 kw aeration To Wairau Estuary on ebb tide DAF DAF Feed Pumps Aerated Pond I1 28,700 m³ 366 kw aeration Overflow for sludge wasting DAF Subnatant Figure Industrial Wastewater Flow Schematic On 5 February 2014, discharge of treated effluent from the domestic system to the Opawa River was ceased. The effluent from Domestic Pond 5 and Industrial Pond 6 are now combined and receive further treatment in the new wetland before discharging to the Wairau Estuary via a new larger capacity outfall (adjacent to the old one), as shown in Figure 1.3. The completed upgrade also includes land application of treated effluent, when soil and groundwater conditions allow, via K- CH2M Beca // 5 May 2014 // Page 2

6 line irrigation and drip lines. It is understand that some irrigation has occurred. Pond 14 Figure Wastewater Flow Schematic as of February 2014 Prior to February 2014, treated effluent from the domestic system was continuously discharged to the Opawa River, and treated industrial flows were discharged to the Wairau Estuary on the ebb tide. Historically, some industrial effluent from the now-closed PPCS Meat Processing Plant was applied to land during the summer months Upgrading History Prior to 2002, the BSTP consisted of a number of treatment ponds used to treat domestic wastewater from Blenheim and industrial flows from Canterbury Meat Packers and the Riverlands Industrial Estate. The industrial ponds were formerly owned by the PPCS Meat Processing Plant, but were purchased by MDC in 2002, after the PPCS operation closed. The former PPCS factory site was subdivided and is now known as Cloudy Bay Business Park. Various new industries, including two wineries, have moved onto this site and the The number of wineries in the Riverlands Industrial Estate has also increased. CH2M Beca // 5 May 2014 // Page 3

7 In 2003/04, the domestic treatment ponds were overloaded in terms of oxygen demand and their performance deteriorated. This overloading occurred during the wine vintage when wastewater with high BOD was received at the plant. As a result, MDC changed the pond system, diverting major industrial flows from the domestic to the industrial ponds, and increasing the aeration capacity of the industrial ponds in order to treat the increased load. Small trade waste discharges in Blenheim continue to contribute about 15% of the domestic flow. MDC was granted consents in late 2010 to upgrade the BSTP effluent discharge system. This upgrading (now completed) included the construction of a series of wetland cells which convey the combined treated flows from both the domestic and industrial pond systems, before discharging to a new outfall in the Wairau Estuary. The wetland system provides some further polishing treatment of the combined flows. The domestic effluent discharge to the Opawa River ceased and up to 190ha of MDC-owned land around the BSTP can be irrigated during the summer months. CH2M Beca // 5 May 2014 // Page 4

8 2 Consent U Domestic Ponds Discharge to Opawa River 2.1 Consent Purpose This consent allows discharge of up to 52,000m 3 /day of treated effluent from the BSTP domestic treatment ponds to the Opawa River. 2.2 Condition 37 Effluent Quality Monitoring That monitoring of the effluent shall be carried out as follows: Effluent monitoring requirements are summarised in Table 2.1. The full set of monitoring data is included in Appendix B. Table Effluent Monitoring Requirements Condition # Frequency Parameters monthly Dissolved Oxygen Conductivity Faecal coliforms Enterococci Total Suspended Solids BOD 5 Total Nitrogen Ammonia-N Nitrate-N Nitrite-N Total Phosphorus Dissolved Reactive Phosphorus 37.2 Annually Metals: As, Cd, Cr, Cu, Pb, Hg, Ni, Zn ph Temperature Figures show the results of monitoring effluent nitrogen, phosphorus compounds and dissolved oxygen and temperature in the period. Note that conductivity was not measured during this period. As shown in Figure 2.1, the mixture of nitrogen species present in the domestic effluent showed a seasonal pattern, with ammonia concentrations increasing from very low concentrations in summer and autumn to higher concentrations in winter. CH2M Beca // 5 May 2014 // Page 5

9 Figure 2.1 Nitrogen Compound Concentrations in Pond 5 Effluent Figure 2.2 shows that the concentration of phosphorus compounds also followed a seasonal pattern, with higher concentrations in summer and lower concentrations in winter. These patterns are as expected for a pond-based biological treatment facility. Figure 2.2 Phosphorus Compound Concentrations in Pond 5 Effluent Figure 2.3 shows the variation of dissolved oxygen (DO) concentrations and temperature in the Pond 5 effluent. Between August 2013 and January 2014, the DO levels have been higher than those observed previously. CH2M Beca // 5 May 2014 // Page 6

10 Figure 2.3 Dissolved Oxygen Concentrations in Pond 5 Effluent Figure 2.4 shows the results of effluent heavy metals monitoring in January 2014 compared with previous years. There has been an increase in the measured concentrations of zinc, copper, arsenic, chromium and lead since January Mercury was not measured in January 2014, and the concentration of nickel remained constant. Figure 2.4 Heavy Metal Concentrations in Pond 5 Effluent The Australian and New Zealand Environment and Conservation Council (ANZECC) Guidelines for Fresh and Marine Water Quality (2000) provide trigger values for toxicants in receiving waters, at alternative levels of protection of species. Two of the measured metal concentrations exceed the ANZECC (2000) trigger values for 90% protection of species in freshwater, as shown in Table 2.2. Those numbers highlighted green are below the trigger values, and those highlighted red are above the trigger values. CH2M Beca // 5 May 2014 // Page 7

11 Table Heavy Metal Concentrations in Pond 5 Effluent Metal January 2014 Arsenic Cadmium Chromium Copper Lead Silver Nickel Zinc ANZECC 90 th %ile Trigger Value The levels of Copper and Zinc measured exceeded the ANZECC trigger values. Copper is approximately 9 times higher than the trigger value and zinc is 1.5 times higher than the trigger value. While the ANZECC (2000) trigger values are for protection of freshwater, it is noted that the Opawa River is tidally influenced at the point of discharge and provides minimal dilution under low flow conditions. The outfall is no longer used as the BSTP upgrade is complete. The monitoring parameters, with limits set in Condition 38 (BOD 5, total suspended solids, ph, faecal coliforms and enterococci), are discussed in Section Condition 38 Effluent Quality Requirements That following commissioning of the plant, as defined in Condition 12 of this consent, and for the duration of this discharge permit, the following effluent quality criteria and sampling requirements shall also apply to the discharge at the sample point provided in Condition 36: Effluent quality requirements and consent limits are set out in Table 2.3. Table Effluent Quality Requirements and Consent Limits Condition # Sample Type & Frequency Parameters Consent limit 38.1 At least 12 flow-proportioned composites per year Carbonaceous Geometric mean of 28 g/m³ BOD 5 Total Suspended Geometric mean of 60 g/m³ Solids ph Between 6.0 and At least 12 grab samples per year, taken between 10:00 am and 5:00 pm Faecal coliforms Geometric mean of 10,000 MPN/100ml Enterococci Geometric mean of 1,000 MPN/100ml A comparison of these consent limits with the data is set out in Table 2.4. All parameters were within the specified range. CH2M Beca // 5 May 2014 // Page 8

12 Table Effluent Quality Limit Comparison Parameter Consent Limit Monitored Value Carbonaceous BOD 5 (g/m³) 28 (geometric mean) 23 Total Suspended Solids (g/m³) 60 (geometric mean) 54 ph Faecal Coliforms (MPN/100ml) 10,000 (geometric mean) 3,030 Enterococci (MPN/100ml) 1,000 (geometric mean) Condition 39 Receiving Environment Monitoring That the discharge shall not cause any of the following effects in the Opawa River following reasonable mixing after the date of commissioning (as defined in Condition 12 of this consent): 1. Outside a mixing zone set at 100 m upstream and downstream of the discharge point (points C and D on Drawing attached): The production of any conspicuous oil or grease films, scums or foams or floatable or suspended material Any emission of objectionable odour Any significant adverse effects on aquatic life. 2. Outside a mixing zone set at 250 metres upstream and 850 metres downstream of the discharge point (points B and E on Drawing attached): Any conspicuous change in water colour The rendering of freshwater unsuitable for consumption by farm animals None of the effects listed above were noted outside of the mixing zone during the monitoring period. 2.5 Condition 40 Receiving Environment Quality Consent Requirements That the consent holder shall monitor the Opawa River environment each year for the impacts of the effluent discharge on the water quality and shellfish quality of the receiving waters. 1. The Council shall monitor water quality in the Opawa River in accordance with the following programme: Collection of water samples at the two sites identified as points A and E on Drawing Water samples shall be collected immediately below the water surface. Samples shall be collected monthly or three monthly before low tide as follows: Sampling parameters are summarised in Table 2.5. CH2M Beca // 5 May 2014 // Page 9

13 Table Opawa River Receiving Water Monitoring Condition Number Sample Location Frequency Parameters Surface water appearance Faecal coliforms and Enterococci Total Suspended Solids Secchi depth Surface Water Three monthly Total Nitrogen Ammonia Nitrogen Nitrate Nitrogen Total Phosphorus Surface Water Monthly Shellfish, from two locations specified on Drawing Microbiological Contaminants Three replicates annually Dissolved Reactive Phosphorus Not specified Plots of faecal coliform and enterococci concentrations at both monitoring sites are summarised in Figure 2.5. The concentration of faecal coliforms found in the downstream samples increased in the winter months, but there were no particular trends in any of the other indicators. Concentrations of both faecal coliforms and enterococci were generally higher than in the previous year. Enterococci are used as indicator bacteria for faecal contamination in coastal contact recreation waters, as outlined in the Ministry for Environment (MfE) Bacteriological Water Quality Guidelines for Marine and Freshwater Recreational Areas (2003). During the monitoring period, upstream enterococci exceeded the MfE Surveillance Guideline of 140 organisms/100ml twice, and downstream enterococci exceeded the guideline on five occasions (refer Figure 2.5). Faecal coliforms are recommended in the MfE guidelines as the microbiological indicator for faecal contamination in shellfish gathering waters. From Figure 2.5, it can be seen that results at both upstream and downstream sites generally did not meet the MfE guideline median of less than 14MPN (Most Probable Number)/100ml and 90th percentile of less than 43MPN/100ml. The river is not a known shellfish gathering site and the gathering of shellfish from the wider estuarine area, downstream of the BSTP discharge, is actively discouraged by MDC through signage warning of the risk to health. CH2M Beca // 5 May 2014 // Page 10

14 Figure 2.5 Microbiological Monitoring Results for Receiving Water Receiving Water Physical and Chemical Parameters Plots of total suspended solids, total nitrogen, ammonia nitrogen, nitrate nitrogen, dissolved reactive phosphorus and total phosphorus concentrations for , are shown in Figures 2.6 to 2.8. The nitrogen and phosphorus parameters are plant nutrients and are commonly used to monitor the potential for eutrophication (excessive algae growth) in receiving waters. Ammonia can also be toxic to aquatic life. A Secchi Disk is used to measure water in receiving waters. As in previous years, Secchi depths were not measured in due to issues with weed in the Opawa River, making measurements impractical. The ANZECC (2000) Guidelines advise a toxicant trigger value of 1.20g/m 3 for ammonia for 90% species protection, which is considered appropriate for slightly to moderately disturbed systems. All monitoring results in the Opawa River for are below this ammonia trigger value. ANZECC (2000) also describes trigger values for physical and chemical stressors, for slightly to moderately disturbed freshwater ecosystems in New Zealand. For total nitrogen, the trigger value is 0.614g/m³. This trigger value was exceeded in July and October 2013 by both the upstream and downstream total nitrogen. In January 2014, the trigger value was exceeded by only the downstream measurement. The only month where both upstream and downstream measurements did not reach the trigger value was April. For total phosphorus, the ANZECC (2000) guideline value is 0.033g/m³, which is met at the upstream monitoring site, but this limit is exceeded by all four measurements taken at the downstream monitoring site. For dissolved reactive phosphorus the ANZECC (2000) guideline value is 0.01g/m³. This trigger value was often exceeded at both upstream and downstream monitoring sites in CH2M Beca // 5 May 2014 // Page 11

15 Figure 2.6 Total Suspended Solids Concentrations in Receiving Water Figure 2.7 Nitrogen Compound Concentrations in Receiving Water CH2M Beca // 5 May 2014 // Page 12

16 Figure 2.8 Phosphorus Compound Concentrations in Receiving Water Edible Shellfish Monitoring Samples of edible shellfish are collected annually at two sites south of the confluence of the Wairau and Opawa Rivers and tested for faecal coliform contamination and more recently, E. coli. The testing site locations are shown in Drawing (Appendix A). After 2006, MDC switched to measuring E. coli instead of faecal coliforms, as this was considered a more appropriate indicator of faecal contamination. However, in 2014, faecal coliforms were tested rather than E. coli. A possible explanation for this could be that the lab forms were redone and the tests taken from the original consent. The results of monitoring for faecal coliforms, carried out from 1995 to 2006, and again in 2014 are shown in Figure 2.9. The Ministry of Health Reference Criteria for Food (1995) still applies and has an upper limit of 330MPN/100g of faecal coliforms in shellfish. From Figure 2.9, it can be seen that historically, the value is close to, or exceeds the MoH limit, in samples at both sites. The gathering of shellfish for consumption from this area is discouraged by MDC through signage warning of the risk to health. In February 2014, the faecal coliform test results were <20 MPN/100ml for both sites, which is lower than the MoH limit. The data for E. coli from 2007 to 2013 is shown in Figure Shellfish samples are also tested for the presence of salmonella. Samples from the February 2014 annual monitoring showed no presence of salmonella, which is consistent with historical data. CH2M Beca // 5 May 2014 // Page 13

17 Figure 2.9 Shellfish Flesh Faecal Coliform Concentrations Figure 2.10 Shellfish Flesh E. coli Concentrations CH2M Beca // 5 May 2014 // Page 14

18 2.6 Condition 41 Reporting The consent holder shall prepare an annual performance review of the treatment plant upgrade. The report shall cover the monitoring results of the previous year and identify any issues relating to the performance of the plant. The first review shall be provided in 1998 and presented to the Manager, Regulatory Department, Marlborough District Council. These reviews shall be prepared every year for the duration of this consent. This report is intended to fulfil the requirements of Condition 41. CH2M Beca // 5 May 2014 // Page 15

19 3 Consent U Industrial Ponds Discharge to Wairau River Estuary 3.1 Consent Purpose This consent allows the discharge of treated effluent not exceeding an annual average daily volume of 4,800m 3 from the BSTP industrial ponds (formerly the PPCS treatment ponds) into the Wairau River Estuary. 3.2 Condition 4 Annual Monitoring Report The consent holder shall provide to the consent authority on or before 31 August in each year of the term of the consent, an Annual Monitoring Report which shall contain the following information: a) An analysis of the extent to which the applicant has, in exercising this consent, complied with consent conditions and the extent and cause of any non-compliance, in each case with a summary of the environmental effects arising from the operation of the outfall, during the preceding 12 month period from 1 July to 30 June inclusive (the reporting period); b) An identification and discussion of any operational difficulties, changes or improvements made to the Blenheim Sewage Treatment Plant and other operating processes, which may cause any material difference in environmental outcomes from the previous reporting period; c) An identification of any maintenance works needed, proposed or undertaken to ensure compliance with these conditions of consent; d) An identification of any improvements or changes required and the timetable for implementation; e) A summary of all the effluent monitoring data collected as a requirement of condition 8 of this consent during the reporting period; f) An analysis of the data summarised under condition 4(e) above in terms of consent compliance and environmental effects during the reporting period; g) A comparison of results with those of previous years and a discussion of any trends during the reporting period; and h) A listing of any complaints received in regard to the discharge of treated effluent from the outfall. This report is intended to fulfil the requirements of Condition 4. As the wetlands are now in use and the discharge from Pond 6 to the Wairau Estuary is no longer used other than for maintenance purposes, this reportwill be the last assessment of compliance in regard to this consent. CH2M Beca // 5 May 2014 // Page 16

20 3.3 Condition 8 Effluent Quality A grab sample of effluent from the outlet of Pond 6 shall be taken each month and tested for the following: - ph - Temperature - Dissolved oxygen - Suspended solids (non-algal and total) - Biochemical Oxygen Demand - Dissolved Inorganic Nitrogen (DIN) - Dissolved Reactive Phosphorus (DRP) - Ammoniacal Nitrogen - Faecal coliforms. The ph, temperature and dissolved oxygen were measured monthly at the Pond 6 outlet as required. Suspended solids, BOD, DIN, DRP, ammoniacal nitrogen and faecal coliforms were measured monthly as required. Condition 8 sets no limits for dissolved oxygen (DO), dissolved inorganic nitrogen (DIN), or dissolved reactive phosphorus (DRP). Figures 3.1, 3.2 and 3.3 show the results of monitoring effluent DO, DIN and DRP concentration over the reporting period. Figure 3.1 Dissolved Oxygen Concentrations in Industrial Effluent (Pond 6) CH2M Beca // 5 May 2014 // Page 17

21 Figure 3.2 Dissolved Inorganic Nitrogen Concentrations in Industrial Effluent (Pond 6) Figure 3.3 Dissolved Reactive Phosphorus Concentrations in Industrial Effluent (Pond 6) CH2M Beca // 5 May 2014 // Page 18

22 Figure 3.4 Ammoniacal Nitrogen Concentrations in Industrial Effluent (Pond 6) 3.4 Condition 9 Effluent Quality Limits The quality of the sampled effluent shall meet the following standards: - ph BOD 5 90%ile: 80g/m 3 Median: 25g/m 3 - Suspended solids (non-algal) 90%ile: 130g/m 3 Median: 75g/m 3 - Faecal Coliforms Geometric mean: 20,000 MPN/100mL Monitoring data for the monitoring period is shown in Table 3.1. It can be seen from Table 3.1 that the industrial STP is operating within consent limits, except for BOD and suspended solids. Refer to Section 4 for possible explanations for the exceedances of the consent limits. CH2M Beca // 5 May 2014 // Page 19

23 Table Consent Limit and Collected Data Comparison for Industrial Effluent (Pond 6) Parameter Consent Limit Monitored Value ph BOD 5 (g/m³) 90%ile limit: 80 Median: 25 90%ile: 95 Median: 47 Suspended Solids (nonalgal) (g/m³) 90%ile limit:130 Median: 75 90%ile: 198 Median: 134 Faecal Coliforms (MPN/100mL) Geometric mean: 20,000 Geometric mean: 4, Condition 11 and 12 Effects of the Discharge 11. The mixing zone shall be as shown on the attached plan called Plan Consent No. D and stamped This plan forms part of Resource Consent U The discharge of treated effluent shall not cause any of the following effects outside the mixing zone referred to in Condition 11: a) The production of any conspicuous oil or grease films, scums, foams or floatable material; b) The emission of any objectionable odour; c) Any conspicuous change in colour or clarity; d) Any significant adverse effects on aquatic life; and e) Any undesirable biological growths. None of the effects listed above were noted beyond the mixing zone, during the reporting period. Previous studies by Cawthron show that the effluent plume does not reach the surface until well downstream of the discharge. Therefore, there is unlikely to be any conspicuous change in colour/clarity, or the production of scums or foams in the receiving waters, after reasonable mixing. 3.6 Condition 13 Exceedances of Consent Limits If any of the effluent consent limits prescribed in Condition 9 is exceeded in samples taken in two consecutive months, the consent holder shall assess the environmental consequences of the exceedance. The results shall be reported to the Manager Resource Consents and Compliance Manager of the Marlborough District Council, within 8 weeks of the identification of the exceedance. As previously discussed, the Pond 6 effluent exceeds the median and 90 th percentile consent limits for BOD 5. In order to further assess compliance with Condition 13, the monthly BOD 5 values have been graphed in Figure 3.5. It can be seen that, the Pond 6 effluent BOD 5 values exceeded the median consent limit of 25g/m 3 for every month except June 2013 in the monitoring period, and that the 90 th percentile was exceeded twice. Therefore under Condition 13, the environmental consequences of these exceedances must be assessed. The Resource Consents and Compliance Manager of Marlborough District Council must also be notified of the exceedances now that they have been identified. CH2M Beca // 5 May 2014 // Page 20

24 Figure 3.5 BOD 5 Concentration in Industrial Effluent (Pond 6) The Pond 6 effluent also exceeds the median and 90 th percentile consent limits for suspended solids. In order to assess compliance with Condition 13, the suspended solids values have been graphed in Figure 3.6. The Pond 6 effluent suspended solids concentrations were below the median consent limit of 75g/m 3 for April July 2013, but then were above the median consent limit from August 2013 onwards, and were above the 90 th percentile limit for six months. Therefore under Condition 13, the environmental consequences of these exceedances must be assessed. The Resource Consents and Compliance Manager of Marlborough District Council must also be notified of the exceedances now that they have been identified. Figure 3.6 Suspended Solids Concentration in Industrial Effluent (Pond 6) CH2M Beca // 5 May 2014 // Page 21

25 4 Discussion and Conclusions 4.1 Overview This assessment is based solely on the physical, chemical and microbiological monitoring as detailed in this report. Monitoring of effluent and receiving water is only carried out on specific days, and it is assumed that the results from the monitoring are representative of water quality at other times, unless specifically stated otherwise. 4.2 Domestic STP - Consent U Effluent (Conditions 37 and 38) The consent requires the regular monitoring of pond effluent and places numerical limits on some effluent parameters. This monitoring was carried out in the period in compliance with the consent requirements, except that conductivity was not measured. Monitoring shows that effluent quality is similar to previous years Opawa River (Conditions 39 and 40) The discharge may not cause any physical effects (including odour, conspicuous change in colour, floatable scums, etc.) outside the specified mixing zone. The discharge has a characteristic algaegreen colour but there is no visual evidence of the presence of the outfall discharge beyond the consented mixing zone. Other physical effects are not evident and MDC is complying with Condition 39. The consent requires MDC to monitor the receiving waters, but places no numerical limits on contaminants. The monitoring was carried out as required, complying with Condition 40, with the exception of Secchi depth, which was not measured due to the presence of weed in the river. The concentrations of nutrients (nitrogen and phosphorus) in the Opawa River showed a similar pattern to previous years. However, the total suspended solids levels were higher than the previous reporting period. For total nitrogen, total phosphorus and dissolved reactive phosphorus, the trigger values were often exceeded at both upstream and downstream monitoring sites in the monitoring period. There were no nuisance algal blooms reported in the monitoring period. The MfE Water Quality Guidelines (2003) recommend that no sample taken during the bathing season exceed an enterococci concentration of 140MPN/100ml. The guideline median value for faecel coliforms is 14 NTU. Concentrations of both faecal coliforms and enterococci were generally higher than in the previous year, and both of these parameters regularly exceeded these guideline values. The shellfish monitoring results from the 2014 samples indicate low concentrations of faecal coliforms, which indicate an improvement on the microbiological effluent quality as compared with previous years. Council discourages the collection of shellfish for consumption from the area with signage warning of the health risks. As the Opawa River receives contamination from a variety of sources within the catchment, including farm runoff, stormwater discharges and inflows from on-site treatment/disposal systems, it CH2M Beca // 5 May 2014 // Page 22

26 is unlikely that consumption of shellfish gathered from the lower reaches is desirable, even after decommissioning of the BSTP domestic outfall. 4.3 Industrial Ponds - Consent U Effluent Quality (Conditions 8 and 9) The consent requires monthly monitoring of Pond 6 effluent and testing for ph, temperature, DO, non-algal suspended solids, BOD, DIN, DRP, ammoniacal nitrogen and faecal coliforms. Condition 8 requires monthly grab samples of Pond 6 effluent to be taken and analysed. Compliance with this condition was achieved. Condition 9 sets limits on effluent ph, BOD, non-algal suspended solids and faecal coliforms. The Pond 6 effluent did not meet the median and 90 th percentile consent limits for BOD 5 and suspended solids. During the previous monitoring period, all consent limits were met except for BOD Impact on Receiving Environment (Condition 13) Where the effluent quality limits set in Condition 9 are exceeded in two consecutive months, Condition 13 requires MDC to assess the environmental consequences of the exceedance and the Resource Consents and Compliance Manager of Marlborough District Council must be notified of the exceedances. The discharge of effluent that exceeds the consented concentrations of BOD 5 from the BSTP is unlikely to be having any significant adverse on water quality or aquatic biota. The organic loading from the treatment ponds is high enough to cause adverse effects in poorly flushed systems or embayments. However, the large flow during ebb tides, sediment re-suspension and the mobile bed sediments, mitigate any significant adverse effects. The sub-tidal sediments in the estuary have low organic content indicating a well-flushed system. The water movement provides significant reoxygenation which also reduces the potential for creation of anoxic sediments. Due to the available dilution and significant ebb tide flows the concentrations of effluent suspended solids recorded are unlikely to cause any adverse impact on water quality. It is worth noting the following comments made by Forrest (2001) in respect of the former PPCS discharge (which had a significant BOD loading from treated meat industry wastes): ".the discharge has no discernible effect on sediment quality or the sea-bed dwelling community. Sediments downstream of the discharge were primarily clean sands and were not enriched in terms of organic matter or nutrients relative to sites immediately upstream" (Forrest, B. (2001) Ecological Impacts of the PPCS Marlborough Effluent Discharge to Wairau Estuary. Cawthron Report No. 673). CH2M Beca // 5 May 2014 // Page 23

27 Appendix A Site Plan and Outfall Monitoring Location

28 Appendix A - Blenheim STP Plant and Outfall Sampling Locations Wairau Bar waterquality sampling/shellfish monitoring Receiving waterquality sampling point Upstreamwater quality sampling point Downstreamwater quality sampling point Industrial effluent sampling point Domestic effluent sampling point Beca // Blenheim STP Consent Complaince Report Monitoring Data // Page 1 of // NZ // site plan Printed 11:10, 27/01/2012

29 LEGEND: DESIGNATION BOUNDARY OUTLINE OF PROPOSED NEW WETLANDS S H 1 S I M T R H A R D I N G S R O A D O P A W A R I V E R S H 1 1 POND 5 I1 POND I2 POND 2C POND 2B POND 2A POND 4 POND 3 POND 6 EXISTING OUTFALL DESIGNATION BOUNDARY DESIGNATION BOUNDARY PROPOSED WETLANDS EXISTING OUTFALL PROPOSED NEW OUTFALL PRELIMINARY DESIGN NOT FOR CONSTRUCTION A FOR PRELIMINARY DESIGN SVM :7,500 1:15,000 SAC SVM BLENHEIM SEWAGE TREATMENT PLANT UPGRADE OVERALL SITE LAYOUT CIVIL C-001 A

30 Appendix B Monitoring Results

31 Monthly Recorded Parameters in Pond 5 Effluent "Effluent Outlet" Carbonaceous BOD5 SS ph DO Temperature May Jun Jul Aug Sep Oct Nov Dec Jan Geomean Median Max 8.5 Min 7.5 Ar Cd Cr Cu Pb Hg Ni Zn Jul Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan Jan ANZECC trigger v

32 Domestic Receving Water Parameters Measured Quarterly TN Nitrate-N NH4-H Nitrite-N TP DRP Conductivity U/S D/S Effluent U/S D/S Effluent U/S D/S Effluent U/S D/S Effluent U/S D/S Effluent U/S D/S Effluent Effluent Apr Jul Oct Jan Apr Jul Oct Jan < 0.01 < Receiving Water Parameters Measured monthly Suspended Solid Faecal Coliforms Enterococci Date U/S D/S Eff U/S D/S Effluent U/S D/S Effluent Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan <10 52 Geomean

33 Faecal Coliforms Enterococci BOD TSS (Nonalgal) DIN DRP DO ph Total Ammoniacal- N Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb geomean median %ile max min

34 Presumptive Coliforms Shellfish Sampling Faecal Coliforms E. coli Salmonella Date 28-Feb-95 Site not detected 27-Feb-96 Site not detected Site not detected 18-Feb-97 Site not detected Site not detected 5-Feb-98 Site not detected Site not detected Site 3 2 <2 Site 4 33 <2 18-Mar-99 Site Site Feb-00 Site Absent Site Absent 26-Feb-01 Site Absent Site Absent 26-Feb-02 Site Site Feb-03 Site Not detected Site Not detected 3-Mar-04 Site Not detected Site 2 4-Mar-05 Site Not detected Site Not detected 1-Mar-06 Site 1 Site Not detected 28-Feb-07 Site Not detected Site Not detected 29-Feb-08 Site 1 90 Not detected Site 2 90 Not detected 25-Feb-09 Site Not detected Site Not detected 8-Feb-10 Site Not detected Site Not detected 17-Feb-12 Site Not detected Site Not detected 18-Feb-13 Site Not detected Site Not detected 12-Feb-14 Site 1 <20 Not detected Site 2 <20 Not detected NZ BSTP data for BECA to xlsx Page 1