Agenda of Nelson Regional Sewerage Business Unit

Nelson Regional Sewerage Business Unit

9 December 2016

REPORT R5951

Bell Island Wastewater Treatment Plant - Pond Sludge Management

1. Purpose of Report

1.1. To review the options of dealing with the sludge accumulation in the maturation and facultative ponds at the Bell Island Wastewater Treatment Plant (WWTP).

2. Recommendation

That the Business Unit

Receives the report Bell Island Wastewater Treatment Plant - Pond Sludge Management (R5951); and

Approves proceeding with engaging Gurney Environmental for the supply and delivery to Nelson of 9 (nine) Accel-o-Fac series three aerator/mixers in Pond F2 up to 50% of the value of $280,000 (excl GST); and

Approves the investment of up to $60,000 to install the 9 (nine) Accel-o-Fac series three aerator/mixers in Pond F2; and

Approves the negotiation of a variation to the Operation and Maintenance contract for the installation of nine Accel-o-Fac aerator/mixers in facultative pond F2 and;

Approves funding for the upgrade of the maturations ponds and desludging of the ponds in the 2015/16 and 2016/17 Business Plans be utilised for this initiative; and

Approves the monitoring of effluent quality in chambers C4, C5 and C6 to assess the performance of upgraded pond (F2) compared to the other two facultative ponds (F1 and F3); and

Requests that the outcome of the monitoring be reported back to the NRSBU for approval prior to the remaining 50% payment being made to Gurney Environmental.

3. Background

3.1. The Bell Island WWTP includes 3 facultative oxidation ponds (F1, F2 & F3) and 2 maturation ponds (M1 & M5). These ponds are an important part of the treatment process in that they allow natural processes to treat the wastewater. Part of this natural process involves the settlement of sludge to the base of the ponds.

3.2. The ponds have aerators as follows;

· F1 – 1 No. Hamilton brush aerator/mixer plus 4 No. Aire-O₂ Aspiration Aerators.

· F2 – 1 No. Hamilton brush aerator/mixer plus 4 No. Aire-O₂ Aspiration Aerators.

· F3 – 1 No. Hamilton brush aerator/mixer plus 3 No. Aire-O₂ Aspiration Aerators.

· M1 and M5 – no aerators.

3.3. All the ponds experience a build-up of sludge that in time increasingly compromises their effectiveness. It has been 20 plus years since the last desludging was undertaken.

3.4. The NRSBU Business Plan 2016/17 has listed capital projects to upgrade the performance of the WWTP including the proposal to de-sludge the ponds. Table 3.4 outlines the capital projects related to the pond efficiency improvements;

Table 3.3 – Capital Upgrade Projects 2016/17 Business Plan

Year	Description of Projects	Estimated Costs
2016/17	Carry forward from 2015/16: Desludging Ponds (Option Study)	40,000
	Modification pond M1 (The installation of the curtains in M1 will create directional flow through the pond which will result in improved treatment and removal of algae. The work will only commence once the effectiveness of improvement in M5 has been assessed)	140,000
	Carry forward from 2015/16: Modifications pond M5	140,000
	Desludging oxidation ponds (The desludging will be carried out over two financial years)	200,000
2017/18	Desludging oxidation ponds (The desludging will be carried out over two financial years)	1,400,000
2018/19	Modification pond F3 (The installation of the curtains in F3 will create directional flow through the pond which will result in improved treatment and removal of algae. The work will only commence once the effectiveness of improvement in M1 &M5 has been assessed)	140,000

4. WWTP – Pond Sludge Management

4.1. Over recent years there has been a gradual increase in carbonaceous biological oxygen demand (CBOD) in the final discharge effluent from the WWTP. Although this increase is still within the consented limits for the discharge, it does indicate a decrease in retention times within the ponds. This could be attributed to the increasing sludge accumulation.

4.2. Recent sludge surveys have confirmed the increased accumulation. They have also confirmed that the sludge is only partially digested. This is not surprising as the current aeration system was not designed to provide sufficient aeration and mixing. The original intention was to allow the ponds to operate naturally with some minor aeration and mixing capability introduced in 1992 to enhance performance.

4.3. The NRSBU has anticipated the need to deal with the accumulated sludge as outlined in its Business Plan 2016/17 and Table 3.3 above.

4.4. There are several options that could be implemented to deal with the accumulated sludge in the ponds. These are summarised as follows;

· Mechanical Removal – remove sludge using specialised equipment and either place in geobags or dispose of in a consented manner (either on site or at approved landfill);

· Increased aeration and mixing – additional aeration and mixing can accelerate the digestion of sludge accumulated in the ponds.

5. WWTP - Pond Performance

5.1. The ponds are currently operating well, however a review of the aeration and mixing indicates that there is an opportunity to improve treatment efficiency. Although sludge will still be a by-product, initial assessments suggest that with improved aeration and mixing there is likely to be better sludge digestion and longer lead times between de-sludging.

5.2. Recent condition and performance inspections have confirmed that the Aire-O₂and Hamilton aerators are at the end of their useful lives. Whilst not requiring urgent replacement these aerators are now high maintenance. The Aire-0₂’s parts are becoming difficult to source and the motors are getting to the point where rewinding is increasingly expensive due to the amount of wear etc.

5.3. It is therefore prudent to either consider replacing them as is, or reviewing the types and layout of aerators to improve the efficiency of the ponds.

5.4. The replacement cost of the current aeration/mixing equipment is $67,000 per facultative pond (around $200,000 for the three facultative ponds).

6. Sludge Removal Options

6.1. The NRSBU has been assessing the options to deal with the accumulated sludge in the ponds. This has included considering improvements in the aeration and mixing parameters which potentially have an impact by reducing sludge production and increasing sludge digestion. Some of the options claim to reduce levels of accumulated sludge and claim to keep sludge at manageable levels that will never require physical removal. These claims need to be substantiated.

6.2. In general conventional sludge removal option is only focused on sludge removal and does not improve mixing or aeration. The other options are primarily focused on aeration and mixing and any improvement in sludge digestion is consequential.

6.3. The conventional sludge removal is required every 20-25 years depending on the loadings and pond treatment effectiveness. The cost of this is around $1,400,000 for the three FOPs each time. It requires a consent to dispose of the sludge and this can occur either in an appropriate manner on site or at another consented off-site location e.g. landfill (The cost of haulage and disposal to landfill is not included in this estimate).

6.4. The installation of comprehensive aeration/mixing equipment on all three FOPs is estimated at around $1,200,000. The annual operating cost of these vary as some equipment utilise wind power, others utilise solar energy and others electrical power. The wind power and solar energy equipment can have backup power installed. The annual operating costs are estimated as follows;

· Current system $26,500/year

· Wind power alone $2,200/year

· Wind power with backup electrical power $4,220/year

· Solar energy alone $500/year plus $7,000 every seven years for replacement of batteries

· Grid-Bee electrical powered misers $7,500/year

6.5. The conventional sludge removal does not improve aeration/mixing whereas the improved aeration mixing does.

7. Aeration/Mixing and Sludge Management Proposals

7.1. The sludge removal proposals are outlined as follows;

· Conventional Sludge Removal – utilising mechanical equipment to remove sludge from the ponds;

· Improved Aeration/Mixing - Accel-o-Fac equipment which may improve sludge digestion and reduce accumulated sludge levels;

· Improved Aeration/Mixing - Solar/Grid-Bee Equipment which may improve sludge digestion and reduce accumulated sludge levels.

8. Conventional Sludge Removal

8.1. The most common method to remove sludge from ponds in New Zealand is the use of a dredge.

8.2. The sludge is generally thickened through the application of polymer with effluent diverted back to the pond and the thickened sludge placed in a contained area (could include a geobag or a sludge lagoon).

8.3. The sludge is then allowed to dewater naturally.

8.4. Once the sludge has reached a specified consistency it is disposed of through land application or landfilling.

9. Improved Aeration/Mixing - Accel-o-Fac Aerators/Mixers - Gurney Environmental

Overview

9.1. There is a company that supplies wind powered aerators. The company is called Gurney Environmental (GE) and a representative visited the WWTP in April 2016. GE has developed a proposal for the NRSBU. The proposal focuses on the eventual installation of wind generated Accel-o-Fac aeration/mixing equipment in all the ponds. GE believes that this equipment will not only improve the mixing and aeration of the ponds, but also reduce the volumes of accumulated sludge.

9.2. GE has analysed the treatment plant data to evaluate the current performance of the pond system. It also analysed the wind profile at Nelson airport and translated that across to what would occur at Bell Island. It confirms the wind consistency and strength are sufficient to effectively power the Accel-o-Fac aerators/mixers.

9.3. Based on this analysis the wind generated Accel-o-Fac aerators/mixers are designed to:

· Provide a cost effective upgrade that will make use of existing assets and improve the treatment capabilities and capacity of the treatment plant.

· Eliminate short circuiting from inlet to outlet.

· Distribute loads evenly through the ponds.

· Reactivate and increase digestion of the accumulated sludge in the ponds.

· Increase Dissolved Oxygen levels through the ponds to provide improved BOD and TSS removal, and nitrification.

· Increase the robustness of the wastewater treatment system so that it will accommodate increased loads, and wide swings in flow and loading without operator attention.

· Minimise and/or eliminate odour.

· Deliver maximum processing for the minimum total-life-cost and the least operator attention.

The Gurney Environmental Proposal

9.4. Gurney Environmental has proposed installing its equipment in all five ponds. This comprises 33 Accel-o-Fac Aerators at a capital cost of approximately $1,250,000 excl GST.

9.5. In proposing this as the ultimate intention, GE has proposed a progressive implementation with a risk-share approach until the effectiveness of the aerators/mixers has been confirmed by the NRSBU. GE has suggested that the equipment be installed on F2 pond initially with the NRSBU only funding 50% of the cost until the stated performance has been achieved.

9.6. The scope of this initial investment is as follows. GE shall:

· Supply and deliver 9 (nine) Accel-o-Fac series 3s aerators;

· Supply mooring system;

· Send an engineer to oversee the installation;

· Total cost of $280,000 (UK Pound 152,000)

9.7. The NRSBU shall:

· Pay GE 50% of the equipment and shipment cost of $140,000 (UK Pound 76,000) upfront with the balance due when the NRSBU is satisfied that the Accel-o-Fac system is providing the benefits promised.

· Be responsible for the installation cost to be carried out by a local contractor. (Estimate NZ$60,000)

· Install the aerators in accordance with the design in pond F2.

· Evaluate the performance of pond F2.

9.8. The total estimated cost of implementing the proposal is estimated at $340,000 but is subject to exchange rates and actual confirmed construction costs. Initially the NRSBU will need to fund around $200,000 and pay the balance to GE as and when performance is confirmed.

9.9. GE expect the following improvement to occur with the Accel-o-Fac aerators:

· The sludge level will drop by 762mm (Two and a half feet) and result in a 40% decrease in the volume of sludge in the bottom of the pond over time.

· Stabilisation of the sludge blanket level will be observed within a 12 month period.

· Noticeable pond effluent improvements within one month of installation.

Proposed Performance Assessment

9.10. While the promised improvements might appear speculative it is not difficult to measure the performance of the upgraded pond compared to the performance of the other two ponds.

9.11. The COD, CBOD, Total Nitrogen, Total Phosphorous and suspended solids are monitored in the discharge chambers of the facultative ponds so any improvements can easily be assessed.

9.12. A sludge survey programmed for November 2016 will be delayed to provide comparative performance based on the June 2014 pond survey and other surveys completed in the past four years. Any changes to the sludge blanket can be benchmarked against previous sludge survey results.

9.13. Whilst poor management of loads can distort the outcomes, GE is confident that it is not in the interest of the NRSBU to manipulate the outcome of the process and is therefore prepared to share the risk with the NRSBU to the extent that the payment of the remainder of the contract value will be at the discretion of the NRSBU.

Due Diligence on the Proposal

9.14. Gurney Engineering provided a number of case studies that demonstrate projects implemented worldwide achieved the outcomes stated in their proposal. A literature study and assessment of the documentation provided support their proposal.

9.15. Inverloch Treatment Plant, Victoria Australia – has installed and has been trialling a Accel-o-Fac unit in a pond at the Inverloc treatment plant for the last two years. It has installed another unit at another treatment plant following part evaluation of the first unit 18 months later.

· The Council reported that the units installed achieved a 20% increase in Dissolved Oxygen (DO) allowing them to turn a 22kW aerator off for the greater part of the year and maintaining the required pond performance.

· It continues to run the 22kW aerator as a precaution during the peak loading periods to supplement DO transfer to the ponds (Seasonal peak load resulting from influx of visitors into the area).

· These aerators generated significant energy savings compared to all the other aerators trialled.

· The units are easy to operate and maintain.

· The construction is high quality and the aerators are considered more durable than alternatives considered.

9.16. South Gippsland Water reported their findings relating to the use of wind generated Accel-O-Fac mixers to the 78^th Annual WIOA Victorian Water Industry Operation Conference. It reported that these mixers provide:

· More cost effective solution than other systems considered. (Solar powered systems were found to be significantly more expensive than wind generated systems)

· Energy saving allows for 6 year pay-back period.

· Did not require installation of 0.55kW backup motor.

· Dissolved oxygen levels in the pond improved significantly.

· Easier and less maintenance.

· Improved effluent quality.

· Lower Health and Safety risks associated with servicing.

9.17. It is apparent that efficiency gains in treatment have been made at the different locations where Accel-o-Fac aerators were installed. Improved DO transfer throughout the water column in the ponds contribute to conditions required to optimise bacterial activity in the ponds.

9.18. Many of the case studies report that sludge is stabilised in the ponds to the effect that desludging of ponds will not be required. In some instances the ponds have been operational for more than 40 years with no requirement to desludge these ponds.

9.19. Reduction of sludge blanket of two and a half feet is reported in some of the case studies.

10. Solar/Grid-Bee - Iguana Water Solutions

10.1. SolarBee, a subsidiary of the Novasys Group in the United States of America. SolarBee has provided quotes for a solar powered and grid system that will provide optimal pond conditions for pond F2.

10.2. Based on the current pond parameters SolarBee provided quotes for a solar powered and grid powered mixing system through their agents in Australia, Iguana Water Solutions. The SolarBee design consists of a 5 No. machines at a total cost of $500,000 (solar) and $335,589.56 (grid) shipped to Bell Island and delivered to Nelson. The final cost subject to exchange rate changes.

10.3. Installation and connection to electrical grid, where required, are at the cost of the NRSBU. This is estimated to cost around $60,000 for the five units.

10.4. The annual operating costs are estimated to be around $20-22,000 per annum. The savings in power costs for the solar models are absorbed in depreciation on their greater value.

10.5. The SolarBee Engineers claim that with SolarBee circulation in F2, the sludge blanket should even out and start digesting at a much faster rate in a matter of months. It claim that many of “their customers have never had to consider dredging again after installing the machines, even those with severe sludge buildup issues before installation”.

11. Assessment of Proposals

11.1. Opus International Consultants (Opus) have undertaken a high level assessment of the Accel-o-Fac proposal. It has indicated that this technology that has not been implemented widely, however its aeration and mixing focus would improve pond effectiveness and efficiency. It has reservations about the sludge management claims but has recommended that the equipment is worthy of a trial.

11.2. The following table 11.2 outlines the respective annual operating estimates for each of options in pond F2.

Table 11.2 – Annual running for upgraded Facultative Pond F2

11.3. This table shows that the current system has the highest annual operating costs and that the Accel-o-Fac option has the lowest annual operating estimates.

11.4. The Net Present Value (NPV) for each of the options as installed in Pond F2 has been calculated. These NPV values have been calculated over 50 years at a discount rate of 6%. They essentially give an indication of the whole of life costs for infrastructure by including the capital and renewal costs, operational costs, maintenance costs and deprecation over the 50 year period. The results are outlined in Table 11.4.

Table 11.4 - Net present value for Facultative Pond F2 upgrade

11.5. The NPV results indicate that the current system has the lowest NPV ($371,000) with the next highest NPV being the Accel-o-Fac option ($409,000). Although this table compares the value of each option in economic terms, it does not account for the improved pond performance the other options would bring. If additional aerators and/or mixers were installed to the current system then it is very likely that the NPV would increase above the other options.

11.6. Accel-o-Fac and Solar Bee engineers claim that the implementation of the proposed improvements could delay the removal of sludge from the ponds indefinitely. This would bring a significant saving as the estimated $1.4 million every 20-25 years could be either delayed or, if the claims are substantiated, may not need to be undertaken.

11.7. It is therefore proposed that some of the funding set aside for the de-sludging of the ponds over the next 2 years be utilised to fund the installation of aerators/mixers in Pond F2 initially. The NRSBU can then assess the effectiveness of this option in managing the sludge before committing to further investment in the other ponds.

12. Potential Benefits of Implementing Aeration/Mixing Proposal

12.1. If the installation of aeration/mixing equipment is implemented and the improved treatment is achieved this will provide the following benefits:

· Extend the useful life of pond F2;

· Provide an opportunity to evaluate implementing aerator/mixing equipment in all 5 ponds;

· Avoid having to undertake an environmental analysis and obtaining consents for sludge disposal;

· Improve the quality of the effluent discharged from the WWTP;

· Result in significant cost savings by deferring conventional sludge removal;

· Provide the opportunity to further divert load away from the aeration basin.

13. Practical Installation of Aeration/Mixers Option

13.1. Although there is confidence that the aerator/mixing option will provide adequate DO to the ponds it is considered prudent to retain the current aerator system for use as and when required (especially so during winter months when available wind is much less than during the rest of the year).

13.2. Once the aeration/mixing options has been fully evaluated and implemented, and the anticipated improvements substantiated, the current aerator equipment could be removed permanently. This alone would decrease electricity use by approximately $13,000 per pond per year and remove the need for their replacement in the future.

14. Consultation

14.1. The NRSBU could invest the allocated funding and still comply with its objectives in its Business Plans for the improvement of the ponds.

14.2. The changes proposed are not likely to have any detrimental environmental effects that could affect the public.

15. Conclusion

15.1. The implementation of the aeration/mixing option as proposed by Gurney Environmental will improve the treatment efficiency of the ponds. This will also improve the digestion of sludge. The scale and extent of sludge digestion and particularly in treating the sludge already accumulated is less known. However, indications are that it will have a positive affect and could defer the need for conventional sludge removal indefinitely.

15.2. Gurney Environmental has accepted that the NRSBU would be taking a risk implementing the proposal. GE has offered a 50% investment until the effectiveness of its proposal is substantiated. If the NRSBU does substantiate the claims then it has the discretion to pay the balance to GE.

15.3. The results of the project will provide the NRSBU with information required to consider whether the conventional removal of sludge is warranted to the same extent as originally envisaged.

15.4. The NRSBU can be reasonably confident that the installation of the aerators/mixers in Pond F2 will result in a beneficial outcome for both the efficiency and effectiveness of the pond and could enhance the digestion of the accumulated sludge.

Richard Kirby

Consulting Engineer

Attachments

Nil

Important considerations for decision making

1. Fit with Purpose of Local Government

This project fits in with the purpose of local government as it contributes to meeting the current and future needs of communities for good-quality local infrastructure and local public services.

2. Consistency with Community Outcomes and Council Policy

This report is in line with the objectives of the Nelson Regional Sewerage Business Unit in the provision of cost-effective collection and treatment of wastewater.

3. Risk

The risks related to improvements to mixing in facultative pond F2 are outlined in the report and the risks associated with the recommended option have been highlighted and dealt with.

4. Financial impact

The project will be funded from budgets approved in the 2016/17 Business Plan and carry overs from the 2015/16 Business Plan

5. Degree of significance and level of engagement

This matter is of low significance because it relates to enhancing the business continuity for the wastewater treatment plant operations.

6. Inclusion of Māori in the decision making process

Consultation with Maori occurred as part of the Draft Annual Plan 2016/17 process.

7. Delegations

The Committee has the responsibility for considering the backup power supply as part of management of the Nelson Regional Sewerage Business Unit and report to Council through its draft Business Plan 2017/18.

Nelson Regional Sewerage Business Unit

9 December 2016

REPORT R6834

Bell Island Wastewater Treatment Plant - Electrical Power Business Continuity Assessment

1. Purpose of Report

1.1 To review and assess business continuity requirements and options for the supply of electricity to the Bell Island Wastewater Treatment Plant (WWTP)

2. Recommendation

That the Business Unit

Receives the report Bell Island Wastewater Treatment Plant - Electrical Power Business Continuity Assessment (R6834); and

Notes the offer from Network Tasman to fund 50% of the capital cost ($447,000) of installing a second cable to the Bell Island Wastewater Treatment Plant has been declined; and

Approves adding the option of including the installation of permanent backup generation for the Inlet Structure and Discharge Pump (250 kVa) in the draft Business Plan 2017/18.

3. Background

3.1 The Bell Island treatment plant started operating in the early 1980’s.

3.2 Currently there is only one electrical cable supplying power to Bell Island WWTP. This cable is owned by Network Tasman and crosses the estuary south of the plant. It has a capacity of 2.0 MW.

3.3 Having only one cable is a risk to the ongoing supply of power to the plant. This risk to supply was initially identified during Engineering Lifelines studies undertaken around 2007/2008 for the region.

3.4 Prior to 2010, the NRSBU were considering an upgrade to the treatment plant and this included the option of dewatering sludge. The NRSBU asked Network Tasman for options on increasing the power supply to Bell Island to meet the electrical demands of sludge dewatering.

3.5 Network Tasman responded with the following statements:

· “The most limiting factor is the size of the existing 11kV cabling and the amount of current that can travel through the cable before damage occurs. When the cable is run close to its capacity limit, as it will be with the proposed capacity increase, the probability of failure increases rapidly.

· Whilst a fault to a cable upon Bells Island may take a couple of days to repair or a week to replace, if the cable fault were to occur under the estuary the repair may take several weeks and the replacement would take considerably longer.

· Network Tasman Limited strongly recommend that a backup supply is looked into whether it be generation or a second secure 11kV supply to the island, either across the causeway or through the estuary (overhead or underground) as there will be no quick fix if the estuary cable fails.”

· “Your [WWTP] co-incident load, ie when everything peaks at one time, will be the limitation and naturally as more load comes on the cable heats up (i^2r) until the insulation finally breaks down. It is therefore unwise to run the cable beyond full load or our case we prefer not to run cables etc continually at their FL rating anyway just to give longer life.”

3.6 This response from Network Tasman clearly indicated that the cable had limitations. The NRSBU would need to consider the additional cost of increasing the supply capacity.

3.7 However, during the 2010 upgrade it was decided not to progress with the dewatering component of the upgrade. This additional capacity was therefore not required and the plant could continue to operate within the capacity of the current cable. The peak use is currently 1.2 MW compared to the cable capacity of 2.0 MW.

3.8 The security of supply associated with a single cable still remains a risk and the NRSBU have asked Network Tasman to review and respond to this risk.

3.9 Since 2010, the NRSBU has implemented procedures to ensure that electricity demand remained within the design capacity of the power cable. For instance, when the discharge pump (Outfall) starts operating, one of the 6 larger aerators is programmed to switch off to keep the power demand consistent.

4. Network Tasman Proposal

4.1 After considering the risk associated with a single cable, Network Tasman has confirmed that as a supplier, the most cost-effective solution is a second underground cable to the Bell Island WWTP. This cable would be on a separate alignment to the current cable and run from the overhead supply on Best Island, along the golf course fairway adjacent to the treatment plant access road, under the estuary and along to the treatment plant. Network Tasman has secured easements along the proposed route.

4.2 The total cost of the project is estimated at $447,000. This is greater than what Network Tasman had budgeted for the work and it has requested that NRSBU consider sharing the cost 50:50. This would require NRSBU funding $223,500 (plus GST). Network Tasman would own the cable.

4.3 Although Network Tasman are contracted to supply electricity, it has not guaranteed to provide a continuous supply 100% of the time. This is not unusual as events do occur that can interrupt supply which are beyond Network Tasman’s control. This includes the current cable failing.

4.4 The key issue for the NRSBU is the impact of no power supply for what could potentially be up to a week should the cable fail.

4.5 Network Tasman has confirmed that the proposed cable will have around 20% greater capacity than the current supply cable. Although this is not of benefit to the NRSBU at present, it could be of benefit if any future upgrade at the plant is required.

4.6 Network Tasman has indicated that the second cable would be configured in such a way that it would become immediately operable should the current cable fail.

4.7 The NRSBU considered the Network Tasman proposal at its meeting 16 September 2016. It requested that more research on the risks of power failure and the comparative costs of backup generation to mitigate those risks.

4.8 Rather than focus purely on the single cable, an assessment has been undertaken focusing on the business continuity risks associated with various power disruption scenarios. The following section summarises that assessment.

5. Business Continuity Assessment – Power Supply Disruption

Operational Demands

5.1 The current WWTP operational demands peak at 1.2 MW which is comfortably within the 2.0 MW capacity of the cable. Consequently, the risks of the current cable failing because of capacity exceedance is very low, if not negligible.

Power Disruption Scenarios

5.2 There are four scenarios that could threaten the continuity of the power to the Bell Island WWTP. These are summarised in increasing scale as follows:

5.2.1 Scenario 1 - Minor power disruption for up to 4 hours at any one time – this is likely to be a local failure that interrupts supply or a more widespread disruption. Network Tasman would have contingency plans to restore power for this type of disruption.

5.2.2 Scenario 2 - Moderate power disruption in excess of 4 hours and up to 24 hours – this is likely to be a major local failure or more widespread disruption that takes longer to reinstate. Network Tasman would have contingency plans to restore power for this scenario as well.

5.2.3 Scenario 3 - Significant power disruption in excess of 24 hours and up to 14 days – this is could be the failure of the current cable and Network Tasman would need to locate and identify the fault and restore power. This scenario is likely to be more widespread post a serious natural event that would probably result in an emergency declaration and probably comprise repairs to power infrastructure across the Nelson/Tasman Region. Network Tasman would probably require additional expertise and resources from other parts of New Zealand to help with this scenario. The resumption of power services would take time.

5.2.4 Scenario 4 - Major power disruption in excess of 14 days – this is likely to be a major natural event that has probably impacted the greater Tasman/Nelson region. Network Tasman would probably require additional expertise and resources from other parts of New Zealand and maybe internationally to help with this scenario. The resumption of power services would take time and the priority would be the welfare of people and animals. The Bell Island WWTP would have lower priority.

Scenario Risk Assessments

5.3 The likelihood of Scenario 1 occurring is almost certain. Currently power failures ranging from 15 minutes to 1 hour occur 2-5 times per year. Although the power is usually restored the consequence of these types of power failures on the treatment plant are low. This will be discussed further below

5.4 The likelihood of Scenario 2 occurring could be considered unlikely. They could occur once or twice over the next 15 – 20 years. Although Network Tasman would have the capacity and capability to reinstate the power supply in accordance with its supply contract, the consequence of any power failure to the operation is considered to be low - medium. This will be discussed further below.

5.5 Scenario 3 includes the failure of the current cable to the treatment plant. The likelihood of this occurring is considered to be rare - unlikely. The cable is not currently stressed and therefore would be expected to last its natural life. Network Tasman has indicated that it could take up to a week to locate and identify the fault and restore power. Although Network Tasman would have the capacity and capability to reinstate the power supply in accordance with its supply contract, the consequence of this length of power outage is considered to be medium - high. This will be discussed further below.

5.6 The last two scenarios (Scenarios 3 and 4) also comprise major natural events where the priority to reinstate the Bell Island WWTP power supply would probably be secondary to other health and welfare demands. Potentially any portable power generation capability in the region would be deployed to meet other health and welfare demands. This could also impact generation equipment purchased and installed at the WWTP as this could be requisitioned by Civil Defence to meet other health and welfare demands. The likelihood of this scenario to the NRSBU is rare, however the consequences are considered to be medium to high. This will be discussed further below.

Bell Island WWTP – Backup Power Generation

5.7 The NRSBU has completed a Hazard and Operability Study (HAZOP) for the Bell Island WWTP. The study concluded that the WWTP could continue to treat wastewater for extended periods of disrupted power supply. Mobile generators, if available, could be deployed within days of a power outage if required.

5.8 Previous assessments have identified several options for backup generation;

5.8.1 The NRSBU arrange with Network Tasman to manage the deployment of emergency generators when required. Network Tasman would have the expertise to ensure these generators were appropriately located on site as well as manage the effects of any backload into its power supply network.

5.8.2 The NRSBU arrange with Network Tasman to install a single generator (around 1200kVA) located close to the aeration basin transformer and feed the other transformers from this point using existing Network Tasman cabling (Network Tasman would have to implement and manage this option).

5.8.3 The NRSBU arrange with Network Tasman to install an appropriately sized generator at each transformer site – this would require up to 5 generators of between 100kVA and 500kVA (Network Tasman would have to implement and manage this option).

5.8.4 The NRSBU install backup generation at critical locations to minimise the impact of any power disruption (NRSBU would implement and manage this option).

5.9 Network Tasman has assessed all these options and concluded that from its perspective a second cable is the most cost-effective way of providing greater security of supply.

5.10 Between 31 January 2014 and 27 March 2014 the NRSBU did not use any electricity in the aeration basin and this resulted in minimal (not noticeable) adverse effects. The power consumption at that time was less than 4,000kWh per day compared to the normal daily peak of around 13,000kWh.

5.11 Although this trial was undertaken in the summer months when the pond efficiency is more effective, it does indicate that the treatment plant is resilient. It can be operated quite effectively with lower power use and still maintain good performance for extended periods of time. There would be lesser resilience in the winter months maybe 3-4 weeks at a maximum.

Risk Assessment

5.12 The risk of a power outage lasting greater than 14 days is considered to be very low. If it did occur it is likely to coincide with a major event across the region. The evidence suggests that the Bell Island WWTP could operate with minimal back-up power generation for up to 14 days. The only risks during this period would be potential increase in odour and the increasing risk of a compromised quality of effluent discharge.

5.13 The critical components over the short term are the inlet structure and associated electrical controls. The discharge pump would be the next priority, although it is only likely to be needed during periods of high flow. These periods could conceivably occur during a major power outage event e.g. earthquake, major storm, hurricane etc.

5.14 The other components could be left idle for 2 to 4 weeks before odour, dormant sludge and compromised discharge become issues. The raw wastewater would be distributed directly from the inlet structure to the Facultative Oxidation Ponds (FOP) during this period. There is sufficient buffer in the FOPs to accommodate the additional wastewater loading if required.

Backup Generation Options

5.15 A review of the likely power generation requirements for varying lengths of power disruption is summarised as follows;

5.15.1 Inlet Structure (inlet screens and primary sludge pumps) – The inlet structure is the most critical component. It should, preferably, remain operational during any power disruption. This outcome suggests that the NRSBU should consider installing permanent backup generation (100Kva) for the inlet structure with automatic cut over in the event of any power failure. This will keep the inlet screens and primary sludge pumps functioning whilst allowing screened effluent to flow (under gravity) to the rest of the treatment plant. This would keep the inlet structure functional for any length of power disruption.

5.15.2 Outlet Pump – The outlet pump is normally only required when the outlet flow is greater than normal, which often coincides with significant stormwater inflow. This outcome suggests that backup generation (150Kva) would be required if the power disruption occurred concurrently with high rainfall. This is considered to be realistic occurrence therefore for the marginal extra cost the permanent inlet structure generator be increased in size to operate the outlet pump as well.

5.15.3 ATADS and Biosolids Pump – The Autothermal Thermophilic Aerobic Digestion Tanks (ATADs) and biosolid pumps could be left dormant for up to two weeks without power. Thereafter they would need to be restarted. Any longer than two weeks could result in additional odour problems and the need to remove solids and clean before recommissioning. The ATADS and biosolids pump would need up to 350kVA backup generation to operate effectively.

5.15.4 Aeration Basin – The aeration basin could be left for up to 3 weeks without power if it was operating at the time of the power outage. Any longer than three weeks could result in additional odour problems. Should the power disruption occur when the aeration basin is not operational then odour problems are not likely to be an issue. The aeration basin would need back up generation of up to 500kVA if required to remain operational in periods of power outage.

5.15.5 Pond Aerators – The pond aerators provide additional treatment capacity. During a power outage the ponds would continue to treat wastewater through natural means. The ponds could possibly treat the full wastewater load for up to four weeks. After four weeks the quality of the treated effluent discharged into the estuary could be compromised and odours could begin to occur. The pond aerators would need back up generation of up to 100kVA to continue to operate in periods of power outage.

Cost Estimates

5.16 The back-up generation capital and operational costs are summarised as follows;

	100 kVA Generator (Inlet Structure only)	250kVA Generator (Inlet Structure and Discharge Pump)
Supply and install	$46,000	$80,000
Power Synchronising Controls	$6000	$6000
Upgrade switchboard	$40,000	$40,000
Upgrade controls	$7,000	$7,000
Harmonic correction	$10,000	$10,000
Total Estimate	$109,000	$143,000
Maintenance	$3,500/yr	$4,500/yr
Operation	$600/day	$1,500/day

6. Summary

6.1 The WWTP is very resilient in that the Facultative Oxidation Ponds (FOPs) can operate effectively for short periods (2-3 weeks) without aeration – potentially longer periods during summer.

6.2 The WWTP has been configured to ensure that the power draw-off is well within the capacity of the current power supply cable. This is important for the long-term durability of the cable. The cable is therefore less likely to fail. However in the event of failure Network Tasman has indicated it could take up to a week to locate the fault and repair it.

6.3 The inlet structure is the most vulnerable component to power outages. Incoming wastewater needs to be screened. Minor power outages can occur. The inlet screens stop operating and the screenings build up and unscreened wastewater enters the plant. After power outages the inlet screens need to be reset. Funding the installation of backup generation for the inlet structure would be appropriate. It would cater for both minor and major power disruptions i.e. minutes, hours, days or weeks.

6.4 The flow from the inlet structure can gravity to the rest of the plant and distributed to the FOPs without further pumping.

6.5 The Aerator Basin and the ATADs can cease operating for up to 2 weeks without major concern (beyond 2 weeks there could result in increasing odour issues).

7. Conclusion

7.1 The conclusion is that there is no justification for the NRSBU contributing to the 2nd power cable.

7.2 The NRSBU should consider the installation of permanent backup generation at the inlet structure. This can be included in the next revision of the Business Plan.

7.3 The risk of extended periods of power disruption is sufficiently low. Combining this with the natural resilience of the WWTP, it is concluded that no further permanent backup generation is required.

7.4 The business continuity plan should include contingency plans to respond to the unlikely occurrence of an extended period of power disruption.

Richard Kirby

Consulting Engineer

Attachments

Nil

Important considerations for decision making

1. Fit with Purpose of Local Government

This project fits in with the purpose of local government as it contributes to meeting the current and future needs of communities for good-quality local infrastructure and local public services.

2. Consistency with Community Outcomes and Council Policy

This report is in line with the objectives of the Nelson Regional Sewerage Business Unit in the provision of cost-effective collection and treatment of wastewater.

3. Risk

The risks related to power failures are outlined in the report and the risks associated with the recommended option have been highlighted and dealt with.

4. Financial impact

The recommended option is proposed to be included in the Draft Business Plan 2017/18 with the intention of funding it in that year.

5. Degree of significance and level of engagement

This matter is of low significance because it relates to enhancing the business continuity for the wastewater treatment plant operations.

6. Inclusion of Māori in the decision making process

Consultation with Maori will occur as part of the Draft Annual Plan 2017/18 consultation process.

7. Delegations

The Joint Committee has the responsibility for considering the backup power supply as part of management of the Nelson Regional Sewerage Business Unit and report to Council through its draft Business Plan 2017/18.

Nelson Regional Sewerage Business Unit

9 December 2016

REPORT R6816

General Manager's Report

1. Purpose of Report

1.1 To report on the NRSBU operational activities over the last few months and outline what is proposed over the next few months.

2. Recommendation

That the Business Unit

Receives the General Manager's Report (R6816) and its attachments (A1649724, A1665105, A1645078, A1436459, A452094, and A1664757); and

Approves the Draft Business Plan 2017/18 (A1664757).

3. Bokashi Logic Proposal

3.1 The Bokashi Logic was initially presented to the NRSBU in late 2015. The NRSBU held a workshop on 23 February 2016 to discuss the merits of the proposal as presented. Essentially Bokashi Logic were suggesting that EM (effective micro-organisms) when added to the facultative and maturation ponds would enhance treatment of the sludge. Bokashi proposed trials which would require investment by the NRSBU.

3.2 The consensus was that more evidence needed to be produced to substantiate the claims. Bokashi Logic were asked to revise their proposal requiring more risk on its part into the outcome of the trials.

3.3 At its meetings 24 June 2016 and 16 September 2016, the NRSBU was given an update on progress with this proposal.

3.4 Although the Bokashi Logic proposal outlined a trial process, it still has not included any details on a testing regime to demonstrate how the biosolids are affected by the introduction of the additive. Specific sampling and laboratory testing would be required to validate the results and it was unclear from the proposal who would be responsible for this cost.

3.5 In proposing the trial, Bokashi Logic requested a financial contribution of $9,000 to run the trial over a period of approximately 100 days.

3.6 The NRSBU requested this additional detail and has received a response from Bokashi which has outlined a revised trail involving 8 x 1,000 litre water tanks. The NRSBU has met Bokashi on site and been briefed on the revised proposal. These trials and the liability of the proposed costs are still being finalised.

3.7 Since the 16 September 2016 meeting, there has been no further contact from Bokashi Logic. The NRSBU is not aware of any further progress on this proposal. Until Bokashi Logic furnish a more details around the proposal and who will be responsible for the costs and risk, it is proposed that this not be reported on any further.

4. Accidental Discharge Consent – Nelson City Council

4.1 The NRSBU lodged an application for a resource consent for the accidental discharge of wastewater into the estuary. This was primarily from the NRSBU reticulation and pumpstations. The layout of this infrastructure is shown in Figure 2.0 below.

4.2 This was initially lodged on 23 July 2015 with the Nelson City Council (consenting authority). NCC subsequently requested additional information and this was collated and lodged 29 February 2016.

4.3 The application was notified publically during August/September 2016 and submissions closed at the beginning of November 2016.

4.4 Thirty five submissions were received.

· One submission was in support of the consent.

· Four of the submissions did not oppose the consent application and asked to be heard.

· The other submissions all opposed the application submission mainly on the grounds that the discharge of any raw sewage to the Waimea Inlet is unacceptable.

Figure 2.0 Showing NRSBU Reticulation, Connections and Pumpstations

4.5 A more fundamental issue raised by the submitters is the perceived inactivity by Nelson City Council and Tasman District Council at addressing storm water inflow and infiltration. (If Board members wish to review the submissions received these will be made available on request)

4.6 Following evaluation of the submissions it was decided to retain the services of Fluent Solutions (Designers of the regional pipeline upgrade project) to provide engineering expert witness at the hearing and Cooper Rapley (John Maassen) to provide legal support for the project.

4.7 The public hearing for the application is expected to be held in March 2017.

4.8 It should be noted that the discharge of wastewater in Tasman District Councils is a prohibited activity and therefore a consent application cannot be submitted.

5. Office of the Auditor General - Annual Audits Arrangements

5.1 The Office of the Auditor-General (OAG) has sent a letter setting out the procedures to renew the contract with the NRSBU for the annual audits of its accounts. The OAG proposes to engage Audit New Zealand to continue undertaking these audits on its behalf.

5.2 It was agreed that a Draft Audit Proposal will be prepared for discussion with the NRSBU with the objective of renewing the agreement for a further three years.

6. Pump Station Energy Review

6.1 Enercon was commissioned to review the operation of NRSBU pump stations with the view to identify energy saving opportunities. The report confirms that the systems run efficiently.

6.2 The report does outline improvements that could be made to the management of the storm pumps during periods of high flow. The improvements would optimise pump operations to respond more effectively to flow variations during high flow events.

6.3 However, the associated costs and risks of these improvements which include reprogramming control systems, do not justify changing the pump controls for what is at best a very marginal cost saving.

6.4 It is therefore proposed to continue the current practice. The operators monitor the flows at the pump stations during wet weather events and reset control systems once the high flows have dropped to the point where they and can be managed by one storm pump.

7. Impact of the Bell Island Regional Treated Effluent Discharge on the Coastal Environment : 5 Yearly report

7.1 This is a report that the NRSBU commission every 5 years to determine the impact of the effluent discharge on the coastal environment.

7.2 The report confirms that continued discharge of treated wastewater from Bell Island has no discernible impact on the environment. It states that;

· Seawater stratification characteristics indicate rapid mixing of the low salinity wastewater discharge with estuarine receiving waters within the ebb tide flow channels.

· Receiving water nutrient concentrations indicate adequate dilution down-current from the Bell Island wastewater outfall to prevent development of eutrophication.

· Ammoniacal-N concentrations at all sites were well below ANZECC (2000) and USEPA (1986) guideline trigger levels, ensuring that potentially toxic conditions were not achieved.

· Phytoplankton characteristics at inner Tasman Bay sites were considered to be normal for the region, reflecting the seasonally productive spring diatom growth period but showing no discharge-related signs of over-enrichment or stimulation of undesirable species.

· Receiving water faecal coliform and enterococci concentrations indicate that the Bell Island outfall discharge was not a significant source of bacterial contamination during the sampling period.

· Concentrations of faecal coliforms and enterococci in mussels, summarised from 16 bio-monitoring surveys (2008-2016), indicate that contributions from the Bell Island discharge were minor in comparison to catchment runoff.”

7.3 The report suggests that additional investigations in the relationships between catchment sources of contaminants and estuary water quality could be useful. It would assist in the interpretation of the relative significance of point-source discharges, such as the Bell Island wastewater discharge. The report implies that other sources of contaminants have a more significant impact on water quality in the Waimea Inlet.

8. WWTP - Discharge Consent Renewal

8.1 The discharge consent for the Bell Island Wastewater Treatment Plant expires on 7 February 2018. The consent comprises the discharge of treated wastewater to the Waimea Inlet, the discharge of treated wastewater to land at Bell Island and the discharges to air related to the wastewater treatment plant at Bell Island.

8.2 Significant data sets are now available on the performance of the treatment plant in terms of the effects of discharges from Bell Island. Analyses of the performance of the treatment plant suggest that the improvements have facilitated compliance with the objectives of the consent.

8.3 The NRSBU is engaging appropriate expertise to develop the application. Request for Proposals for the professional services and legal services closed on 1 December 2016. They are currently being assessed using the Brookes Law methodology.

8.4 It is anticipated that both professional services and legal services will commence working on the consent application from 16 January 2017.

8.5 The project will need to be managed actively to consolidate the consent application for lodgement with the consent authority in early August 2017.

9. Pond Sludge Management

9.1 At its meeting 24^th June, the NRSBU were briefed on a proposal from Gurney Environmental regarding the installation of Accel-o-Fac aerators in the ponds to reduce sludge production and volumes. The intention was to undertake more research to achieve more certainty around the cost-effectiveness of this proposal and associated investment.

9.2 The NRSBU has progressed the investigations including a meeting with a wastewater specialist at Massey University who has seen the equipment in the UK. The NRSBU obtained some feedback and suggested a course of action for further investigations.

9.3 The results of the assessment and conclusions are outlined in a separate report on this agenda.

10. Contract 3458 – Operation and Maintenance

10.1 The reticulation and treatment operations have continued as normal over the last few months. The effluent discharge continues to meet consent conditions and sludge produced at the treatment plant complies with Class A biosolids quality.

10.2 The ponds continue to perform well. Loads are diverted away from the activated sludge area and into the ponds to utilise the capacity of the ponds during the summer months resulting in energy savings in the aeration basin.

10.3 Following the recent blockage on the biosolids transfer pipeline, trials of different types of pigs on different types sludge transfer pipelines have been undertaken. These trials indicated that sludge build up can be better managed through better selection of pigs and changing pump controls. The result is that pigging is carried out under increased flow velocity.

10.4 The operational costs are tracking ahead of budget. These are primarily due to the costs associated with clearing the blockages in the biosolids and primary sludge transfer pipelines. The operations of the plant are being optimised to better utilise the capacity in the ponds, thereby reducing costs. It is intended that savings will be made over the remaining part of the year to cover the additional costs to date.

10.5 The use of the belt thickener to manage the thickening of primary sludge has resulted in a significant increase of cost. The methodology used by the contractor to thicken up the primary sludge is currently under review as the expected decrease in biosolids produced has not reduced as anticipated. With ENZA going off line until March 2017 it is not expected that any further thickening of primary sludge will be required until then.

10.6 The aeration basin and secondary clarifier will be taken off line during December 2016 for annual maintenance and additional condition assessment of the secondary clarifier mechanical components.

Songer Street Pump Station: Blockages

10.7 There have been recent blockages occurring in the Songer Street Pumpstation. These have been caused by increased stormwater infiltration flows picking up settled solids and items in the reticulation and flushing them into the pumpstation all at once.

10.8 The control systems have been modified and appear to have mitigated the problems experienced. NCC officers continue work on managing the problems in the reticulation upstream of the pump station.

11. Contract 3619 – Biosolids Operation

11.1 The monthly average volume of biosolids sprayed over the last few months have stayed at higher levels. However they have dropped significantly over the last month.

11.2 The projected volume of biosolids that will be sprayed this year are trending to exceed the volume budgeted for.

12. Key Performance Indicators

12.1 The outcomes of key performance indicators for the 3 month period to 31 October 2016.

13. Compliance Outcomes

13.1 The compliance outcomes for the 12 months to 31 October 2016 are outlined in the following table:

i)	Resource Consent Compliance (rolling 12 month record)
	Ø Discharge to Estuary Permit			Achieved.
	Ø Accidental discharges (Consent for accidental discharges within Nelson City Council area is being sought at present)			Overflows occurred at the Beach Road, Saxton Road and Songer Street pump station during the heavy rain event on 24 March 2016. The rainfall event is the second highest rainfall recorded over a 24 hour period recorded for Nelson since January 2000. An overflow occurred at the Songer Street during wet weather conditions when both storm pumps blocked on 22 June 2016. Biosolids overflow to land and the Waimea estuary following a blow out on biosolids transfer pipeline on 19 and 20 July 2016.
	Ø Discharge to Air Permit			100% Compliance
	Ø Biosolids Disposal			100% Compliance
	Ø Discharge treated waste water to land			100% Compliance
ii)	Odour Notifications
	Ø Past three months	Nil.
	Ø Last 12 months	Nil.
iii)	Overflows
	Ø Past three months		Nil.
	Ø Last 12 months		Five.
iv)	Speed of response for maintenance works
	In past three months: Ø Six call outs were associated with treatment plant issues. · Aeration basin aerator – 1 event. · Gravity belt thickener – 2 events. · Washwater – 1 event. · Milliscreen – 2 events. Ø One call out recorded for pump stations. · Richmond – power failure.
	Ø Response within 30 minutes. Achieved.

14. Review of Action Plan Implementation –
2014 Asset Management Plan and 2015/16 Business Plan

The following table indicates the draft time lines for the individual action items:

IP	Business Plan Action	Target Date	Completion Date	Comments
1	Review manuals annually.	Dec 2016		Delayed. Contract manuals are reviewed annually by the contractor and submitted to the NRSBU for review. All the manuals have been reviewed with the exception of the Operation and Maintenance Manual. It is expected that this will be comleted in December 2016.
2	Consolidate all natural disaster information and review 3 yearly.	Mar 2018		Work will be carried out as part of next asset management review.
3	Internal benchmarking carried out annually.	Jun 2016	Aug 2016	Carried out as part of annual report.
4	Review risk of contributors leaving NRSBU.	Jun 2016	Dec 2015	Completed.
5	Review capacity of treatment components.	Mar 2017		Expect treatment plant model to be in place in March 2017. This will follow an assessment of S::can results.
6	Programme for pipe inspections.	Dec 2016		Included in annual review of Operation and Maintenance Plan.
7	Annual review of contractor performance.	Dec 2016	Jun 2016	Completed.
8	Screen upgrade.	April 2017		Variation issued to Nelmac to proejct manage the installation of the second inlet screen.
9	Review secondary sludge separation.	May 2017		Depends on completion of treatment plant model.
10	Construction second sludge storage tank.	Jun 2017		Delayed from June 2016.
11	Develop sludge removal programme.	Jun 2017		Subject of a separate report to 9 December 2016 NRSBU Meeting.
12	Review effluent discharge management.	Mar 2016	Jan 2016	Competed.
13	Renewal of effluent discharge permit	Aug 2018		Preparation of application commences in January2017.

AP	AMP Action	Target Date	Completion Date	Comments
1	Annual customer survey.	Mar 2016	Apr 2016	Completed.
2	Business Continuity Plan review.	Jun 2016	Jun 2016	Completed.
3	Consider benefits of succession planning and how it might be implemented once governance issues (TDC and NCC) have been resolved.	Jun 2016	June 2016	Completed.
4	Review of security required at all facilities.	Mar 2016	May 2016	Completed.
5	Monitor sludge levels in ponds and ascertain long term removal and disposal requirements.	Mar 2016	Feb 2006	Completed.
6	Improve reporting requirements for asset condition, performance and maintenance from maintenance contractor.	Mar 2016	Apr 2016	Completed.
7	Implementation of internal bench marking (using historical data) of NRSBU network, pump stations, treatment and disposal facilities.	Jun 2016		Delayed until 2017.
8	Develop Demand Management Policy.	Jun 2016	Jun 2016	Completed.

15. Health and Safety

15.1 There have been 8 inductions and 207 visitors to the Bell Island WWTP over the past three months.

15.2 Five health and Safety incidents were reported.

· In two instances operators suffered minor cuts when attending to mechanical equipment.

· An operator got sprayed with algae when operating the algae transfer pump. The algae transfer system was inspected and fittings replaced where required.

· An operator observed unsafe practices employed by engineering staff. Following an investigation additional site signage was deployed and information added to isolation permits.

· The team leader observed an incident where a trailer was towed using an incorrectly sized vehicle. Following an investigation plates showing the capacity of the trailers were fitted to trailers.

16. Financial Status

16.1 Expenditure is tracking above budget. This has been a result of dealing with the biosolids transfer pipeline blockages and the blow out which was not budgeted for.

16.2 There has also been an increase in monitoring costs:

· The testing daily trade waste samples collected from the three industrial contributors, as arranged following the review of the Agreement for Disposal of Trade Waste. This amounts to $3,000 per month.

· The cost of the five yearly environmental monitoring associated with the treated wastewater discharge. This cost was budgeted for in year 2017/18 instead of 2016/17.

16.3 The cost of biosolids spraying is expected to exceed the budget for this financial year as the decrease in biosolids volume following the introduction of sludge thickening has not eventuated as anticipated. The cost of thickening primary sludge is projected to exceed the budget by $30,000 for the year.

16.4 The cost of power supply is tracking well below budget and the annual cost is expected to be well under budget.

16.5 Current projections show that operation and maintenance expenditure will exceed the budget by over $100,000. To compensate for this increased expenditure, discretionary expenditure will be deferred where feasible.

Richard Kirby

Consulting Engineer

Attachments

Attachment 1: NRSBU Pump Station Energy Audit A1649724 ⇩

Attachment 2: NRSBU Audit Arrangements A1665105 ⇩

Attachment 3: Coastal Environment: Five yearly Receiving Water Survey A1645078 ⇩

Attachment 4: Memorandum of Understanding A1436459 ⇩

Attachment 5: Status Report A452094 ⇩

Attachment 6: Draft Business Plan 2017/18 A1664757 ⇩

Important considerations for decision making

1. Fit with Purpose of Local Government

This update fits in with the purpose of local government as it contributes to meeting the current and future needs of communities for good-quality local infrastructure and local public services.

2. Consistency with Community Outcomes and Council Policy

This report is in line with the objectives of the Nelson Regional Sewerage Business Unit in the provision of cost-effective collection and treatment of wastewater.

3. Risk

There is no risk in the recommendation to receive this report and approve the draft business plan 2017/18.

4. Financial impact

None

5. Degree of significance and level of engagement

The recommendation to receive this report and approve the draft business plan 2017/18 is of low significance.

6. Inclusion of Māori in the decision making process

Consultation with Maori will occur as part of the Draft Annual Plan 2017/18 consultation process.

7. Delegations

This is a matter for the Nelson Regional Sewerage Business Unit.