Mt Eden Main Works Flocculant Treatment Management Plan
CRL-MTE-RME-LKA-PLN-800041
Revision: 001 Date: 29 June 2020
Flocculant Treatment Management Plan
Flocculant Treatment Management Plan CRL-MTE-RME-LKA-PLN-800041
This document is uncontrolled when printed. This document should be printed in colour
Revision Status Revision
Date
Version details
Prepared By
Approved By
Rev A00
20 April 2020
Draft for Auckland Council and Independent Peer Review
Mike McConnell
-
Rev 000
16 June 2020
Final for Lodgement
Mike McConnell
Peter Roan
Rev 001
29 June 2020
Final for submission
Mike McConnel
Peter Roan
Approval Status Name/Title
Signature
Date
Prepared by:
Mike McConnell Erosion and Sediment Control Advisor
29 June 2020
Approved by:
Peter Roan Consents Lead – Link Alliance
29 June 2020
Flocculant Treatment Management Plan
Table of contents 1. Introduction ........................................................................................... 66 1.1
Purpose of the FTMP ................................................................................................... 66
1.2
Flocculant Treatment Management Plan Author .......................................................... 66
1.3
FTMP Audience ........................................................................................................... 66
1.4
Relevant Conditions .................................................................................................... 68
1.5
Sustainability .............................................................................................................. 73
1.6
FTMP Review and Updates .......................................................................................... 73
1.7
Duration of Works ....................................................................................................... 73
2. Use of Flocculants and Coagulants ......................................................... 74 2.1
Soil Testing.................................................................................................................. 74
2.2
Test Procedure ............................................................................................................ 75
2.3
Potential Flocculants and Coagulants ........................................................................... 75
3. Dosing Options ...................................................................................... 76 3.1
Introduction ................................................................................................................ 76
3.2
Rainfall Activated Dosing ............................................................................................. 76
3.2.1.
Introduction .................................................................................................................. 76
3.2.2.
Rainfall Catchment Tray ................................................................................................ 77
3.2.3.
Header Tank .................................................................................................................. 77
3.2.4.
Displacement Tank ........................................................................................................ 77
3.2.5.
Flocculent Reservoir ...................................................................................................... 77
3.3
Flow Activated Dosing ................................................................................................. 77
3.3.1.
Introduction .................................................................................................................. 77
3.3.2.
Water Treatment Plant(s) ............................................................................................. 77
3.3.3.
Water Treatment Plant Operation ................................................................................ 78
3.4
Batch Dosing ............................................................................................................... 79
3.4.1.
Introduction .................................................................................................................. 79
3.4.2.
Dosing Trigger Level ...................................................................................................... 79
3.4.3.
Batch Dosing Methodology ........................................................................................... 79
4. Storage and Handling of Chemicals ........................................................ 80 5. Emergency Spill Response Plan .............................................................. 80 6. Responsibilities for Operation and Maintenance ................................... 81 7. Monitoring and Maintenance ................................................................ 82
Flocculant Treatment Management Plan 7.1
Monitoring.................................................................................................................. 82
7.2
Maintenance ............................................................................................................... 83
7.2.1.
Rainfall Activated Devices ............................................................................................. 83
7.2.2.
Water Treatment Plants................................................................................................ 83
7.3
Transportation of Flocculation Chemicals ..................................................................... 84
8. Water Quality Discharge Monitoring Programme (WQDMP).................. 85 8.1
Sampling Locations...................................................................................................... 85
8.2
Monitoring Parameters ............................................................................................... 85
8.2.1.
Daily............................................................................................................................... 85
8.2.2.
Weekly .......................................................................................................................... 85
8.3
Monitoring Methods ................................................................................................... 85
8.3.1.
Daily............................................................................................................................... 85
8.3.2.
Weekly .......................................................................................................................... 86
8.4
Trigger Levels .............................................................................................................. 86
8.4.1.
Daily Parameters ........................................................................................................... 86
8.4.2.
Weekly Parameters ....................................................................................................... 86
8.5
Monitoring reports ...................................................................................................... 87
8.5.1.
Initial Monitoring Report .............................................................................................. 87
8.5.2.
Non-Conforming Result Report..................................................................................... 88
8.5.3.
Annual Monitoring Reports .......................................................................................... 88
Attachement 1: ISCA Requirements ................................................................. Attachment 2: Rainfall Activated Device Monitoring Sheet ..............................
Flocculant Treatment Management Plan
1.
Introduction
The City Rail Link (CRL) project comprises the construction, operation and maintenance of a 3.4 km underground passenger railway, running between Britomart Station and the North Auckland Rail Line (NAL) near Mt Eden Station. CRL works in the Mt Eden area involve the construction of the southern section of the tunnel structures and the tie-in of the CRL railway to the existing NAL, including the construction of the redeveloped Mt Eden Station. The Mt Eden Active Construction Zone (ACZ) and Construction Support Areas (CSAs) are generally located between Nikau Street to the north, State Highway 1 (SH1) to the east, Dominion Road to the west and the existing NAL to the south
1.1 Purpose of the FTMP This FTMP has been prepared to identify measures that will be implemented to enhance the effectiveness of the erosion and sediment control measures utilised on site to mitigate and manage the potential adverse effects on water quality during the Mt Eden main works. This FTMP also includes the Water Quality Discharge Monitoring Programme (WQDMP). The objective of the FTMP is: •
To detail how the discharges of water from the site will be monitored to ensure compliance with the above.
It is noted that the main works are to be undertaken within areas of varying degrees of contamination. As such the ability to discharge runoff generated by the works is also primarily regulated by compliance with the Contamination Delivery Work Plan (CDWP). This FTMP has been prepared in accordance with conditions 59 to 64 of the regional land use consent R/LUC/2016/1890. The FTMP has been prepared in consultation with the CRL Mana Whenua Forum and the Mt Eden Community and Business Liaison Group (CLG). A record of the consultation outcomes, including the Link Alliance’s response to matters raised, is included in Appendix D. No construction activities will commence until certification of this FTMP has been received from Auckland Council (as per resource consent condition 60).
1.2 Flocculant Treatment Management Plan Author This FTMP has been prepared by Mike McConnell of McConnell Consultancy Ltd on behalf of the Link Alliance. Mike McConnell is a Certified Professional in Erosion and Sediment Control (Envirocert Certification No 8185).
1.3 FTMP Audience The primary audience of this FTMP is the Management staff of the project and as a reference guide to the Environmental Advisors, Project and Site Engineers. This FTMP will also provide details of the flocculation management practices to be utilised on the main works to stakeholders including Auckland Council and the general community.
Flocculant Treatment Management Plan The required stage specific details, as a result of compliance with this document will be detailed in the SSESCPs, it is these documents that will be used to provide the onsite staff with the information needed to ensure that the approved flocculation management practices are implemented on site. This separation of information and tailoring the included information to the intended audience is critical to ensuring that the flocculation management practices are correctly designed, understood, implemented, maintained and improved.
Flocculant Treatment Management Plan
1.4 Relevant Conditions Table 1.1 identifies the CRL resource consent conditions relevant to this FTMP and where they are addressed in the document. Table 1-1: Regional Resource Consent conditions for FTMP and location in Plan
Flocculant Treatment Management Plan Condition No.
Condition
Relevant section of FTMP
Land Use Consent R/LUC/2016/1890 Flocculant Treatment Management Plan 59
At least 20 working days prior to the commencement of construction, the Consent Holder shall submit to Council (Team Leader Central Monitoring) for certification an FTMP which confirms the measures that will be taken to ensure that the construction of the Project or Project Stage will be generally consistent with the Water Quality Assessment and the Industrial and Trade Activities Assessment prepared by Golder Associates (NZ) Limited, both dated December 2014.
Section 1.1
60
The Consent Holder shall request the Council's (Team Leader Central Monitoring) written determination as to whether the FTMP can be certified, in writing, within 10 working days of receipt of the FTMP.
Section 1.1
No construction activity shall commence until certification from Council is provided. 61
The FTMP shall include, but not be limited to, the following matters: • Specific design details of the flocculent treatment system based on a batch dosing methodology for the site's settlement tanks, including the potential for use of non - flocculants (e.g. chitin based flocculants); • Monitoring, maintenance (including post-storm) and contingency programme (including a record sheet); • Details of optimum dosage (including assumptions); • Results of initial flocculent treatment trial; • A spill contingency plan; and • Details of the person or bodies who will hold responsibility for the long-term operation and maintenance of the flocculent treatment system and the organisational structure which will support this system.
Sections 2.3, 3.0
62
Any change to an FTMP shall be submitted to the Council (Team Leader Central Monitoring) for certification.
Section 1.6
63
The Consent Holder shall request the Council's (Team Leader Central Monitoring) written determination as to whether the proposed change can be certified, to be provided within 10 working days of submission of the change. No activity reliant upon a change to the FTMP can be undertaken until the change has been certified.
Section 1.6
64
The Consent Holder shall comply with the ESCP for the duration of the earthworks associated with the Project.
Section 1.7
Section 7.0 Section 2.1 Section 5.0 Section 6.0
General Performance Standards 68
The operational effectiveness and efficiency of all erosion and sediment control measures specifically required as a condition of resource consent, including the certified ESCP referred to in Condition 53, shall be maintained throughout the duration of earthworks, or until the Project site is permanently stabilised against erosion.
Section 1.7
Flocculant Treatment Management Plan 70
The Consent Holder shall ensure that the erosion and sediment control measures are constructed and maintained in accordance with TP90, except where a higher standard is detailed in an ESCP/FTMP, in which case the higher standard shall apply.
Section 1.1 Section 1.7
Specific conditions – discharge permit (contaminated land) R/REG/2016/1895 and land use consent R/LUC/2016/1890 (Contaminated Land and Resource Management (National Environmental Standard for Assessing and Managing Contaminants in Soil to Protect Human Health) Regulations 2011) Discharge Monitoring 173
Within 30 days of the installation of the water treatment systems, and prior to operation, the Consent Holder shall develop and submit to the Council (Team Leader Central Monitoring) for certification a discharge monitoring programme.
Section 8.0
Flocculant Treatment Management Plan 174
The water quality monitoring programme shall include, but not be limited to:
Section 8.0
a. Sampling locations (to include the final discharge from the treatment system located in CSA 1, CSA 2, CSA 3, CSA 5 and CSA 4); b. Methods and procedures for discharge sampling; and c. Monitoring parameters for analysis, which shall include: Daily • Water clarity (black disc) cm • Turbidity (NTU) • pH Weekly (in addition to the above) • Total Suspended Solids g/m3 • Total recoverable copper g/m3 • Dissolved copper g/m3 • Total recoverable zinc g/m3 • Dissolved zinc g/m3 • Total petroleum hydrocarbons g/m3 • Ammoniacal nitrogen* g/m3 • Nitrate nitrogen* g/m3 *only in discharge from treatment systems in CSA 3 and CSA 4 d. identified trigger levels for each of the above parameters. These trigger levels shall be developed with reference to the ANZECC Guidelines for water quality where applicable; and e. the methods and procedures for investigating and reporting stormwater discharge monitoring results to the Council (Team Leader Central Monitoring). 175
The discharge monitoring programme shall be implemented upon completion of works set out in Condition 168.
Section 1.1 Section 8.0 Section 8.5
Flocculant Treatment Management Plan 176
Within five working days of receipt of sample results showing contaminants exceeding the agreed trigger levels in Condition 174(d):
Section 8.5.2
a. An investigation shall be undertaken to determine why exceedances were detected and to identify any additional source controls or treatment required; and b. The results of the investigation shall be reported to the Council (Team Leader Central Monitoring). Discharge Reporting Requirements 177
Within eight weeks following the start of the monitoring required by Condition 173 a monitoring report shall be submitted to the Council (Team Leader Central Monitoring). The monitoring report shall include, but not be limited to, the following:
Section 8.5.1
a. a summary of the monitoring results to date; b. an interpretation of those results and suggestions for improvement to the site operations; c. a programme for ongoing monitoring including the reporting of results; and d. a programme for the ongoing maintenance of the discharge water management and treatment system. 178
For the duration of the construction stages of the Project, the Consent Holder shall forward a report annually from the date of granting of this consent to the Council (Team Leader Central Monitoring) evaluating the site’s environmental performance for the year to date.
Section 8.5.3
179
The Annual Report required by Condition 178 shall include but not be limited to:
Section 8.5.3
a. all aspects of the performance of the EMP relating to this consent; b. a summary of all revisions and revised sections of the EMP; c. details of all inspections and maintenance of the stormwater system for the preceding 12 months; d. details of and changes to the person(s) or body responsible for the maintenance of site and the organisational structure supporting this process; e. results and analysis of the preceding 12 months of stormwater monitoring, along with an interpretation of those results and suggestions for improvement to the site operations; and f. records of any spills or incidents which occurred within the previous 12 months and the response which was undertaken.
Flocculant Treatment Management Plan
1.5
Sustainability
The Link Alliance is seeking an Infrastructure Sustainability Council of Australia (ISCA) Infrastructure Sustainability (IS) rating for the Project. Further details can be found in the main works CEMP and Sustainability Management Plan. Sustainability requirements that relate directly to this FTMP are included in Attachment 1. These requirements are imbedded within the Delivery Work Plans and Management Plans for the main works to ensure that sustainability is a key focus and ‘the way we do things’. In some cases, the IS requirements and sustainability goals enhance the designation requirements.
1.6
FTMP Review and Updates
This FTMP is a live document that will be reviewed at least annually, or as a result of a material change to the main works, or to address unforeseen erosion and sediment runoff effects arising from construction, or unresolved complaints. The ability to make changes to the FTMP is vital to maintain its effectiveness and relevance as the construction works progress. Revisions to the FTMP will be made: • • •
As the Link Alliance considers necessary Promptly on any material change (including named personnel changes) If requested by Auckland Council
Any changes to this FTMP must be certified by Auckland Council prior to any on-site activity reliant upon the change commencing (as per resource conditions 62 and 63). Refer to the CEMP for further detail on the review and updating process.
1.7
Duration of Works
The works covered by this FTMP will commence in April 2020 and continue until completion of works, June 2023.
Flocculant Treatment Management Plan
2.
Use of Flocculants and Coagulants
The use of flocculants and coagulants (commonly referred to as flocculation) can decrease the settlement time within sediment retention devices and therefore increase the sediment removal efficiency of these devices. In order to maximise the efficiency of sediment retention devices utilised on site, and therefore minimise the adverse environmental effects associated with the discharge of sediment the use of flocculants and coagulants is to be investigated for all sediment retention devices on site. Typically, flocculation for a sediment retention device will be provided unless: • •
Bench testing of soils in the contributing catchment confirms there is no benefit from flocculation, or Where the duration of the earthworks is very short.
Flocculation will be undertaken in general accordance with Section F2.0 Coagulant and Flocculant Treatment of Auckland Council Guideline Document 2016/005 “Erosion and Sediment Control Guide for Land Disturbing Activities in the Auckland Region” (GD05). It is to be noted that the above document focuses on Coagulant and Flocculant Treatment for Sediment Retention Ponds, and in particular the utilisation of a rainfall activated methodology. Due to the dominance of Water Treatment Plants (WTP) to be utilised for the main works the specific dosing methodologies are not typically applicable, however the soil testing and principle of Coagulant and Flocculant Treatment remains applicable. The details of the specific erosion and sediment control measures to be utilised, including the design of the flocculation management practices is detailed within the SSESCP prepared for each stage of work. The initial design of the flocculation management practices will be based on previous information of soil types until the soil testing (Section 3.1) can be undertaken. The implementation and as-builts of any flocculation device will be in accordance with the inspection and as-built procedures contained within the ESCP.
2.1 Soil Testing As part of the initial earthworks associated with areas where flocculation is to be considered, soil samples will be taken and will be bench tested to confirm flocculation options for those soils, including flocculants or coagulants to be used, optimum dosage rates and dosage methodology Where practical this sampling will be undertaken at the time of preparing the SSESCPs. However for a number of locations access is not possible due to the use of the area (NAL in particular) or due to existing ground cover, concrete slabs etc. Note this testing will also consider existing pumped flows from similar locations. This bench testing will also identify any soils where the existing pH is outside of the baseline range of 5.5 – 8.5. This assessment of the additive to be used will also determine the most efficient method of dosing (refer Section 3).
Flocculant Treatment Management Plan In accordance with the monitoring and maintenance detailed in Section 7, as the soil types in each area change due to deeper cuts and/or altering fill sources, the optimum flocculation option may also change. Any changes to the flocculation for a device will be recorded as part of the monitoring records for that device.
2.2 Test Procedure Testing is undertaken by mixing a representative sample of soil from the site with water to produce a weak slurry, representative of sediment laden runoff from the site. Four samples of this are then taken and placed in clear jars along with a fifth reference sample. Potential chemical additives are then added at varying concentrations (where appropriate). At regular intervals (10 minutes, 30 minutes and 60 minutes), the depth of clarity is measured in each sample to determine which dosage of chemical provides the greatest level of settlement. The pH of each sample is also measured after 60 minutes to ensure that this remains within the required limits of 5.5 – 8.5. The appropriate dosage rate is then used to calculate the sizes of the various components of the rainfall activated treatment devices.
2.3 Potential Flocculants and Coagulants A number of potential flocculants and coagulants are available, however experience with the typical soils in the area indicates that the greatest increases in efficiency will be provided by: • • •
Polyaluminium Chloride (PAC) PolyDADMAC EC20 (80% PAC / 20% PolyDADMAC)
When initial testing is undertaken, an assessment will also be made to determine if the use of biobased flocculants provide suitable increases in efficiency. As industry experience changes during the course of the main works, other additives or blends of additives will be considered as appropriate. Each of the above additives can be used in a rainfall activated or a batch dosing method. The use of chemicals in addition to PAC or PolyDADMAC products will be included in a revision to this FTMP. The revisions to address this will identify the chemicals, the dosing procedures and testing and sampling proposed to ensure that residual chemicals are monitored and within acceptable limits.
Flocculant Treatment Management Plan
3.
Dosing Options 3.1 Introduction
There are three main forms of dosing: Rainfall Activated; Flow Activated; and Batch Dosing. In the rainfall activated process, during rainfall the dosing system is automatically activated by rainfall to provide the appropriate volume of additive to the sediment laden surface runoff. In the flow activated process the dosing system is automatically activated by flow (typically pumped) to provide the appropriate volume of additive to the sediment laden inflows. The batch dosing process is typically undertaken to treat an impounded volume of sediment laden water, typically as the result of pumping. This is a manual process where the volume of impounded water is determined and from this the appropriate volume of additive determined, added and mixed. The sampling and testing of soils detailed in section 3.0 will be utilised to determine the appropriate chemical and dose rate.
3.2 Rainfall Activated Dosing 3.2.1. Introduction Rainfall activated dosing will be utilised where the sediment retention devices receive runoff as a gravity surface flow. This system will typically be used in the early stages of the works with a transition to flow activated dosing as the excavation progresses and gravity surface flow decreases. The flocculation systems to be used will be designed in accordance with GD05. The basic design will be a rainfall activated system (typically) using Polyaluminium Chloride (PAC) to dose the Sediment Retention Pond (SRP). The layout of a typical PAC Rainfall Activated System is shown in Figure 4-1 below.
Figure 4-2: Typical PAC Rainfall Activated System Layout
Flocculant Treatment Management Plan
3.2.2. Rainfall Catchment Tray The rainfall catchment tray will be sized to provide treatment at the design dose rate for 100% of the runoff from exposed earthwork areas and for 60% of the runoff from any stabilised areas within the catchment. A 50mm storm event will be used for calculating the size of the tray.
3.2.3. Header Tank The header tank design provides for 12mm of rainfall before dosing commences. At this point a low rate outlet hose with a 3mm orifice is installed. The high rate outlet hose with a 10mm orifice is installed at the level reached by a further 12mm of rain above the low flow outlet. The header tank has a minimum freeboard of 50mm above the high rate outlet. The header tank typically has a diameter of 580mm (a recycled PAC drum).
3.2.4. Displacement Tank The displacement tank will be a neat fit inside the flocculent reservoir tank. The minimum displacement tank capacity will be the equivalent of a 100mm rainfall event.
3.2.5. Flocculent Reservoir The flocculent reservoir tank will have a minimum capacity to store sufficient flocculent to dose runoff from a 100mm rainfall event.
3.3 Flow Activated Dosing 3.3.1. Introduction Flow activated dosing will be utilised where the sediment retention devices receive runoff as a pumped flow. This system will typically be used in the mid to later stages of the works as the excavation progresses and gravity surface flow decreases. Flow activated dosing will be utilised as part of the Water Treatment Plants (WTP). Subject to the activities taking place on site and the contaminants encountered, more than one WTP may be utilised at any one time. The use of and specific design of each WTP is detailed within the applicable SSESCP.
3.3.2. Water Treatment Plant(s) As noted in section 3.5.3 of the ESCP, the primary sediment control for discharges from the site will be Water Treatment Plants (WTP). The water treatment process will include the use of either chemical or non-chemical flocculants (the latter being preferred if effective) as well as pH dosing, and will be undertaken at the WTP. If the quality of the discharge is not deemed appropriate for stormwater discharge, it will be discharged to sewer in accordance with resource consent condition 145 (b) (provided it complies
Flocculant Treatment Management Plan with a Trade Waste Permit previously applied for and authorised by Watercare), or disposed of by a licenced liquid waste contractor (in accordance with resource consent condition 145 (a)) There will be a primary WTP which will be located in CSA 4 in the north-eastern part of the Technical Area . This plant will control water from the tunnelling operation and from the general earthworks within CSA 4 and the M1 ACZ. A secondary WTP at CSA 5 is located adjacent to the entrance off Water Street. This plant will control water from the operations within CSA 5 and the M2 ACZ. These primary and secondary water treatment plants will be supplemented by smaller WTPs which will be relocated around the site as appropriate to control runoff that cannot practically be directed to the primary or secondary WTP. The specific details of each WTP will be detailed within the SSESCP for each area of work.
3.3.3. Water Treatment Plant Operation The WTP will be operated in the following manner: •
Inflows from the site will be pumped to the buffer tanks, which are the primary storage tanks.
▪ Typically flows will be pumped from the site to the buffer tanks as fast as possible so as to keep the site as dry as possible. •
From the buffer tanks water will be pumped to the settlement tank as follows:
▪ Inflow to the settlement tank will be measured by a flow meter, which in turn will trigger flocculent dosing and pH adjustment dosing as required (see below). •
In order to maximise the efficiency of the settlement tank, it is anticipated that flocculant dosing will be beneficial. The dosing will be undertaken as follows:
▪ The specific flocculant to be used and dose rate will be determined by bench testing that will be undertaken during setup of the water treatment plant and prior to commencing operation.
▪ As works progress additional testing will be undertaken as required by changing soil types. ▪ The flocculant dosing will be undertaken by an automated pump, triggered by inflow rates which will add the flocculant at the required rate. •
To comply with the WQDMP pH adjustment will also likely be required and undertaken as follows:
▪ pH adjustment will be undertaken using citric acid or similar product, dosed using an automated pump triggered by inflow rates.
▪ The dose rate to buffer the pH will be determined by a pH sensor, which will sample water within the settlement tank and will be adjusted by the WTP operator as required. • • •
From the settlement tank, compliant outflow will be discharged to the stormwater network. The WTP operation and discharge quality will be monitored daily by the WTP plant operator. Where this discharge quality is identified as non-compliant for stormwater discharge the discharge will be recirculated for additional treatment. If this is impractical and the flow is
Flocculant Treatment Management Plan
•
compliant for trade waste disposal the discharge will be directed to the wastewater network. Maintenance of the WTP will include the following:
▪ Regular cleaning of pH sensors; ▪ Top up of flocculant and pH buffer; and ▪ Regular removal of accumulated sediment within the buffer and settlement tanks (before the total storage volume of the tanks has been reduced by 20%).
3.4 Batch Dosing 3.4.1. Introduction Batch dosing will be undertaken where runoff is impounded and may be the result of ineffective rainfall activated or flow activated dosing. It will also be utilised for minor flows
3.4.2. Dosing Trigger Level The trigger level for batch dosing will be 100mm clarity, i.e., when the clarity of impounded sediment laden runoff falls below 100mm batch dosing will be undertaken in accordance with the following batch dosing methodology.
3.4.3. Batch Dosing Methodology The outlet of any impounded runoff will be blocked. This may be done either with a pre-installed valve or a crimped (folded) section of lay flat hose connected to the outlet of the decant or other methods such as raising the decant. Following rainfall, the clarity will be checked and if less than 100mm, the required chemical will be added by spraying it on the surface of the SRP or by careful application using a bucket or other small container to evenly disperse the chemical over the surface of the SRP. The chemical will be added at the standard rate of dosing for the devices on site, this rate expressed as a litre of chemical per 10m3 of impounded runoff will be included within the specific FMTP details for that device. The impounded water will then be mixed with the chemical using one of the following methods: • • •
Mixing with a pole, paddle or oar Mixing by circulating the impounded flows through a pump Mixing by dragging semi-submerged floats through the surface area of the impounded water.
Once settlement has occurred, typically within 2-3 hours the pH and clarity within the device will be checked. If the pH is between the range of 5.5 and 8.5 and the clarity is greater than 100mm the decant will be opened and the device drained. If the clarity is less than 100mm a further dose of chemical will be added at 50% of the original rate and a further settlement period of 2-3 hours allowed before retesting. If the pH levels fall outside the acceptable range of 5.5 to 8.5 the Environment and Sustainability Manager will be contacted to determine appropriate actions which could include off site removal of
Flocculant Treatment Management Plan impounded water or adding alternate chemicals, such as sodium carbonate or sodium bi-sulphate, to alter the pH. Subject to the weather conditions at the time and the level by which the range has been exceeded it may be appropriate to use the impounded water for dust control.
4.
Storage and Handling of Chemicals
The water treatment chemicals (if assisted settlement is required) will be stored in the CSA in the vicinity of the treatment plant. The chemicals will be stored within bunded enclosures in order to contain any spillage or failure of container vessels or pipe connections. The storage and monitoring of the chemicals will be undertaken by trained personnel in accordance with the requirements of the main works Industrial and Trade Activity Environmental Management Plan (ITA EMP). These personnel will be the same as those responsible for managing the chemical dosing of the influent water. Monitoring will ensure all chemicals used on site are accounted for, and the daily volumes used will be captured on the daily record sheets.
5.
Emergency Spill Response Plan
Where chemical treatment is required during the main works, the chemical substances to be used will be in liquid form. An Emergency Spill Response Plan (ESRP) has been developed to set out the project spill management procedures. The ESRP is Appendix C to the ITA EMP.
Flocculant Treatment Management Plan
6.
Responsibilities for Operation and Maintenance
The Environment and Sustainability Manager or delegated person and Mt Eden Station Construction Manager will be responsible for the implementation of the FTMP, including the operation and maintenance of the treatment system, as outlined in the following Table. Responsibilities for implementation of the FTMP are contained in Table 7-1 below. Table 7-1: Responsibilities for FTMP implementation
Role
Responsibility
• Mt Eden Station Project Manager
• Ensures site personnel adhere to the CEMP and sub-plans (including FTMP) and comply with environmental operating procedures.
• Mt Eden Station Construction Manager • Environmental and Sustainability Manager (ESM) • Environmental Advisor (with support from ESCP Subject Matter Expert)
• Project and Site Engineers
• Treatment plant operator
• Develops, implements and reviews environmental management systems including the FTMP. • Oversees the water quality discharge monitoring and that sampling is carried out as per sampling protocol. • Reviews water quality monitoring results, investigates and reports to Auckland Council any non-compliances. • Provides on-site compliance with resource consent conditions and other requirements (such as trade waste consent if applicable) and ensure site compliance. • Undertakes regular site inspections and audits to ensure compliance with the CEMP and sub-plans, including the FTMP and consent conditions. • Implements (or supervises subcontractors to ensure implementation of) environmental controls in accordance with the contract, CEMP and sub-plans including FTMP. • Ensures environmental erosion and sediment control works are installed and maintained as per ESCP/FTMP and supplier’s technical specifications. • Manages maintenance and operation of the water treatment system. • Inspects works (such as operation and maintenance of the sediment retention devices and the water treatment system) to assess compliance with the FTMP and other sub-plans. • Is responsible for the implementation of the water quality discharge monitoring programme.
• Treatment Unit Supplier personnel • Suppliers / Subcontractors
• Undertakes test procedure and bench testing for use of flocculant at the water treatment system.
Flocculant Treatment Management Plan
7.
Monitoring and Maintenance
In addition to the Water Quality Discharge Monitoring Programme (WQDMP) (section 8), the following monitoring and maintenance specific to the flocculation management practices is required.
7.1 Monitoring Monitoring will include: • • • •
Certification of all ESC devices Inspection after rainfall event Weekly audits Pre and post rain event audits, including significant weather events
The specific monitoring of the flocculation system will be undertaken by the Site Engineers with regular checks of this monitoring made by the Environmental and Sustainability Manager. This monitoring will be undertaken weekly and following rain events of the following items: • • • • • • • •
Rainfall in previous 24 hours Depth of water in displacement tank Volume of flocculent used (added) pH of the pond Initial header tank level Any changes in degree of stabilisation of the site Appearance of pond (relative turbidity) Estimated level of accumulated sediment within pond.
The frequency of this testing may be increased during extended periods of heavy rainfall or reduced during dry periods. An example monitoring sheet is included in Attachment 2. Additionally, prior to any forecast heavy rain or if the site is to be unattended for more than 48 hours, the flocculent reservoir tank will be filled to ensure that chemical treatment will occur through the following (or potential) 50mm of rainfall. The results of pH sampling will be used to determine if any modifications are required to the dosage rate. The acceptable limits for the pH is between 5.5 and 8.5. If the pH levels fall outside these ranges the Environment and Sustainability Manager will determine appropriate actions which could include decommissioning the flocculation unit or adding alternate chemicals, such as citric acid, sodium carbonate or sodium bi-sulphate, to alter the pH. Monitoring of pH will be a key indicator of the potential for residual aluminium discharges. Specifically, overdosing of PAC may cause a reduction in pH, raising the potential for aluminium within the PAC to react, forming toxic aluminium compounds that are bioavailable to fresh and marine water organisms.
Flocculant Treatment Management Plan
7.2 Maintenance 7.2.1. Rainfall Activated Devices The Site Engineer will have responsibility for the maintenance of the rainfall activated chemical treatment devices on their site. The maintenance of the chemically treated sediment retention devices will be similar to that of nonchemically treated devices. The exception will be that the devices will require removal of the accumulated sediment more frequently. This accumulated sediment will be removed, dried and placed in fill areas of the site when this volume exceeds 20% of the pond storage volume or otherwise decreases the efficiency of the pond. For a rainfall activated system the maintenance will include checking that the catchment tray is kept clear of leaves etc., and that the outlet point of the delivery hose is encouraging adequate mixing of the flocculent with inflows. All hoses, connections etc. will be checked to ensure they are sound and that there is no leakage. Flocculent levels etc. will be topped up and the displacement tank emptied at this time. The daily maintenance of the system will also include the setting of the header tank level. This level allows a degree of rainfall to take place prior to dosing occurring. This initial level will be set to the following parameters: • •
When the site is dry, the header tank will be left empty so that 12mm of rain will fall prior to discharge of flocculent During extended periods of rainfall or if the site is already saturated (i.e., runoff will occur as soon as rain begins) the header tank will be filled to the level of the low rate outlet.
As the area of the contributing catchment and the degree of stabilisation within the contributing catchment alters, the area of the catchment tray will be altered to account for these changes. The catchment tray area will also be used as a method of controlling the pH and dissolved aluminium levels.
7.2.2. Water Treatment Plants Each of the Water Treatment Plants will have a dedicated operator. The maintenance of these plants will depend on the actual plant selected but will include: • • • •
Ensuring that sufficient volumes of flocculent and pH buffer (acid) are available. Ensuring that the flocculent / acid dosing components are operating efficiently including cleaning of hoses and outlets as required by the plant supplier. Removal of accumulated sediment. Cleaning of filters and or inclined plates and other components.
The accumulated sludge or sediment will be stored with other excavated material to drain before offsite removal.
Flocculant Treatment Management Plan
7.3 Transportation of Flocculation Chemicals The transportation of Flocculation Chemicals (including chemicals for pH balance) to and from the main works will be undertaken in accordance with the required Hazardous Goods, Traffic and Transport regulations. On site the chemicals will be transported in sealed containers, securely retained within the site vehicle. These containers will be small enough to be easily handled and only the expected required volume will be transported. The use of these chemicals will be in accordance with the Construction Health and Safety Management Plan.
Flocculant Treatment Management Plan
8.
Water Quality Discharge Monitoring Programme (WQDMP)
Resource consent Condition 168 requires that ‘Settlement Tanks’ be utilised to control runoff from the grout plant and segment storage yard. Condition 168 also requires that 2 x ‘Settlement Tanks’ be installed for all ACZ, with the Settlement Tank sizing based on 2% of the contributing catchment. It is considered that the control measures, specifically the Water Treatment Plants, SRPs and DEBs, detailed in the SSESCPs fulfil this condition. Condition 174 of the A2N resource consent details the requirements of the WQDMP. These are addressed as follows.
8.1 Sampling Locations The sampling locations within the CSAs are identified in the SSESCPs for the main works. Typically, the daily sampling will be undertaken at the outfall of each sediment retention device (SRP, Decanting Earth Bund or WTP). The weekly sampling will be undertaken at the lowest stormwater manhole within or immediately below the CSA.
8.2 Monitoring Parameters 8.2.1. Daily Daily sampling and measurement will be made of: • • •
Water clarity Turbidity pH
(cm) (NTU)
8.2.2. Weekly Weekly sampling and measurement will be made of: • • • • • • • •
Total Suspended Solids g/m3 Total recoverable copper g/m3 Dissolved copper g/m3 Total recoverable zinc g/m3 Dissolved zinc g/m3 Total petroleum hydrocarbons g/m3 Ammoniacal nitrogen g/m3 Nitrate nitrogen g/m3
8.3 Monitoring Methods 8.3.1. Daily The method of daily monitoring will depend on the sediment retention device utilised. For the majority of devices this monitoring will be undertaken manually with a grab sample taken at the outlet.
Flocculant Treatment Management Plan For the measurement of clarity this outflow will be collected in a 20L bucket, with the clarity then measured using a 100mm black disk. The turbidity will be measured utilising a handheld turbidity meter. The pH will also be measured using a handheld pH meter. This monitoring will be recorded on daily record sheets detailing the following information: •
• • • • •
Visual check of influent and effluent water clarity, pH, presence/absence visible TPH (e.g. conspicuous oil or grease film, sheen or odour), flocculant type and volume used, dosing system operation; Water clarity; Turbidity; pH; Record any notes for maintenance or additional information (e.g. ordering additional flocculant supplies); and Record of daily volume of chemicals used.
8.3.2. Weekly Weekly sampling will be undertaken by retrieving a sample(s) of outflows from the lowest stormwater manhole within or immediately below the CSA. This sample(s) will be forwarded to an accredited laboratory for testing of: • • • • • • • •
Total Suspended Solids g/m3 Total recoverable copper g/m3 Dissolved copper g/m3 Total recoverable zinc g/m3 Dissolved zinc g/m3 Total petroleum hydrocarbons g/m3 Ammoniacal nitrogen g/m3 Nitrate nitrogen g/m3
8.4 Trigger Levels The initial trigger levels for discharges from the site are:
8.4.1. Daily Parameters • • •
A minimum water clarity for all discharges of 10 cm or greater measured with a black disc pH between 5 and 9; and No visible total petroleum hydrocarbons (TPH) - sheen or odour.
The trigger for turbidity will be determined following the first month of sampling.
8.4.2. Weekly Parameters The initial trigger values for the weekly parameters are taken from the Water Quality Assessment prepared by Golder Associates (NZ) Limited, dated December 2014.
Flocculant Treatment Management Plan These initial trigger levels took into account dilution within the receiving environment, Motions Creek. This consideration resulted in trigger levels being related to the flows within Motions Creek at the time of the discharge. Specifically, the Water Quality Assessment states that the trigger levels for MTE are 25 x ANZECC 95% Freshwater during low flow (being 25 L/s) and 100 x ANZECC 95% Freshwater all other times The flow within Motions Creek at the time of discharge will be determined from the AC continuous flow recorder on Motions Creek (ARC site 8104). These initial trigger levels are set out in Table 9-1 below. Table 8-1: Initial Trigger Values
Chemical / Parameter Total Suspended Solids
Initial Trigger Value Low Flow (25L/s at Flows > than low Motions Creek) flow 3 50 g/m for 95% of the time
Total Recoverable Copper / Dissolved Copper Total Recoverable Zinc / Dissolved Zinc Total Petroleum Hydrocarbons Ammoniacal Nitrogen (CSA 4 Only) Ammoniacal Nitrogen annual maximum (CSA 4 Only)
0.035 g/m3
0.14 g/m3
0.2 g/m3
0.8 g/m3
15 g/m3
15 g/m3
Nitrate Nitrogen (CSA 4 Only) Nitrate Nitrogen annual 95th percentile (CSA 4 Only)
>1.0 and ≤2.4 (g/m3)
>0.03 and ≤0.24 (g/m3) >1.25 and ≤10 (g/m3)
>37.5 and ≤87.5 (g/ m3)
Notes Water Quality Assessment 25 & 100 x ANZECC 95% Freshwater 25 & 100 x ANZECC 95% Freshwater ARC TP10 MFE (2018), Attribute State B MFE (2018), Attribute State B, 25x dilution (low flow) for annual maximum MFE (2018), Attribute State B MFE (2018), Attribute State B, 25x dilution (low flow) for annual 95th percentile
8.5 Monitoring reports The monitoring reports outlined in Sections 9.5.1-9.5.3 below will be prepared and forwarded to Auckland Council (Team Leader Central Monitoring).
8.5.1. Initial Monitoring Report Within eight weeks of monitoring commencing an initial report outlining: • • • •
A summary of the monitoring results to date; An interpretation of those results and suggestions for improvement to the site operations were required; A programme for ongoing monitoring including the reporting of results; and Water treatment plant maintenance programme.
Flocculant Treatment Management Plan
8.5.2. Non-Conforming Result Report Within five working days of receipt of sample results showing contaminants exceeding the trigger levels set out in Section 5.4 of the FTMP, an investigation will be undertaken to determine why exceedances were detected and to identify any additional source controls or treatment required. The results of this investigation will be sent in a report format to Auckland Council (Team Leader Central Monitoring).
8.5.3. Annual Monitoring Reports An annual report will be prepared and submitted detailing: • • • • • •
all aspects of the performance of the EMP relating to this consent; a summary of all revisions and revised sections of the EMP; details of all inspections and maintenance of the stormwater system for the preceding 12 months; details of and changes to the person(s) or body responsible for the maintenance of site and the organisational structure supporting this process; results and analysis of the preceding 12 months of stormwater monitoring, along with an interpretation of those results and suggestions for improvement to the site operations; and records of any spills or incidents which occurred within the previous 12 months and the response which was undertaken.
Flocculant Treatment Management Plan
Attachment 1: ISCA Requirements Table A identifies the ISCA Credit Requirements relevant to this FTMP and where they are addressed in the documents. Table A: ISCA Requirements Credit
Relevant section
Requirement *
Other Relevant Information / Comments
Receiving Wai (Water) Quality DIS-1 Level 1
Measures to minimise adverse impacts to receiving wai environmental values during construction and operation have been identified and implemented. These measures demonstrate an awareness of the values of wai ora and its Mauri, and opportunity for mana whenua feedback has been provided and where practicable incorporated into these measures.
Section 1.2 Section 3.3 Section 8.0
The principle purpose of the ESCP / FTMP is to ensure that discharges of water from the site have as minimal effect receiving wai environmental values as practical. This will be achieved through the implementation of the measures detailed within the ESCP / FTMP and the subsequent SSESCPs.
AND Monitoring of wai discharges and receiving wai is undertaken at appropriate intervals and at times of discharge during construction. DIS-1 Level 2
Monitoring and modelling of wai discharges and receiving wai demonstrates no adverse impact on receiving wai environmental values.
Section 8.0
The monitoring of discharges from the site is detailed within the Water Discharge Quality Monitoring Programme (WDQMP). Refer Section 8.
DIS-1 Level 3
Opportunities to improve receiving wai environmental values have been identified and implemented.
N/A
Not applicable as construction discharges are relatively short term. Adverse effects will be minimised to the greatest practicable extent through compliance with the ESCP and this FTMP
Monitoring and modelling demonstrates improvement of receiving wai environmental values
* Refer to ISCA Rating Tool for full details of the requirement
Erosion and Sediment Control Plan
Attachment 2: Rainfall Activated Device Monitoring Sheet Device Name: Date
Rainfall (mm)
Flocculent Added (litres)
Header Tank Depth (mm)
Catchment Stabilisation (%)
Appearance of Device
Estimated Sediment Depth (m)
pH of Device
Inspected By (sign)