Presentation on theme: "Masterton District Council Homebush Wastewater Treatment Plant Neighbours Meeting 29 September 2014."— Presentation transcript:
Masterton District Council Homebush Wastewater Treatment Plant Neighbours Meeting 29 September 2014
Neighbours Meeting 29 September 2014 Introductions David Hopman – Manager Assets and Operations Ian Steer – Special Projects Manager
Communicate the findings of the Annual Report on plant performance. Overview of construction issues associated with the old ponds. To provide an update on progress with the project and the timeline for the coming year. To provide neighbours with an opportunity to raise any issues they may have and for appropriate people from within the project team to answer questions.
Construction Overview – Work completed Completed construction, lining and commissioning of Pond 1A (final pond). Dewatering, de-sludging and landfilling of material from old pond 1. Construction of the sludge landfill. Partial de-sludging of old ponds 2 & 3. Completion of 65% of the irrigation area including automation. Completion of landscaping. Completion of all access roads.
Operational Overview – Work completed Fully operational ponds (Ponds 1A, 1B & 2-6). Diffuser fully operational. Border strip irrigation from November 2013 to April Harvesting and Sale of balage (3 rotations) & production of 1600 bales. Average irrigation depth of 410mm. (compared to 330mm for Riversdale). Works remaining ◦ Complete de-sludging of old ponds. ◦ Construction of remaining irrigation areas. Outstanding issues ◦ Areas of compaction over some areas of the site are limiting irrigation rates. ◦ Elevated Ground water level preventing construction of all irrigation areas in M zone.
For the 2013/14 monitoring period, the following was noted: The discharged flows complied with the consent requirements on all occasions. The quality of the discharge complied with the consent conditions. E. coli concentrations level downstream of the WWTP were below the surveillance level on all occasions except for 6th October when the upstream concentration was also high. Odour and discharge clarity problems were observed when the last pond was commissioned in May/June. The discharge is still having a localised effect on in-stream biological community structure in the Ruamahanga River and Makoura Stream (although less that the previous year).
Ruamahanga River E. coli Levels of Contact Recreation Guidelines (July 2013 – July 2014) MfE Action Level (550/100mL) MfE Alert Level (260/100mL) RUA 2 (Downstream) RUA 1 (Upstream) Figure 4 Red – Action Zone Orange – Alert Zone Green Zone
General direction of Homebush groundwater flow
Monitoring wells were drilled at Homebush in 2004 to provide reference data. Surveys were undertaken to establish levels of the wells and the groundwater. A number of errors (survey, interpolation of data and change of datum) have now been identified. The design of the border strips located over the old ponds was based on incorrect groundwater level information. These errors only became apparent when the contractor began de-watering of the old ponds and preparing for construction of the border strips in the M zone.
Can Council take legal action? Consultant for initial survey engaged directly by Council. Information supplied to Beca in good faith. Subsequent surveyor engaged by Beca used same base level information for wells. Minor groundwater irregularities were noted during construction but not considered significant. Legal advice is it would be difficult and costly to prove a case against any of consultants or contractors involved.
The current situation The design includes a factor of safety of 30%. This was considered prudent design to address potential risks. Without the M Zone the treatment plant has no safety margin. The Consent allows to increase irrigation from 10 mm/d to 20 mm/d after 2 years operation if it can be shown that all operational targets can be exceeded. After one irrigation season we are not currently in a position to confirm that 10 mm/d can be sustainably exceeded. The Council is required by the consent to undertake a technical review of options to further reduce discharges to the river.
The range of options to utilise the M Zone and reduce the potential irrigation area shortfall include Do nothing Increase height of M1 to M3 Import fill to raise height of M4 to M10 A wetland treatment system in M4 to M10 Infiltration basin system in M4 to M10 Install cut-off drain to existing design Design new cut-off drains Open swales to capture groundwater Spray irrigation of M1 to M3 Abandon M4 to M10
A range of further options to address the potential irrigation area shortfall include Do nothing Extend irrigation onto adjacent Council land Purchase additional land for irrigation Construct a tertiary treatment plant to supply Fonterra standard water to Council dairy farm Extend drip irrigation around the site Ground water pumping Pipeline under river to supply irrigation water to adjacent farm
Recommendation Complete M1 to M3(giving a design factor of safety of 15%), then adopt one of the following four options: Do nothing Construct a wetland Extend the border strip irrigation system to the Homebush dairy farm Install a tertiary treatment plant to produce irrigation water that meets Fonterra standards
The way forward Start negotiations with Hoppers regarding completing M1 to M3. A decision to proceed will be subject to the outcome of these negotiations. Initiate discussions with GWRC regarding additional options and consent variation requirements. Begin the process to evaluate the options to address the irrigation shortfall in conjunction with the affected parties.
The way forward - Programme Complete construction of irrigation areas that can be constructed – This summer. Option evaluation - data collection/treatment trials – Underway. Option evaluation – Workshop with affected parties – proposed around March.
Queries and Concerns During Construction All queries or concerns should be directed to MDC. Calls/contact are logged and directed to Ian Steer. Ian discusses/actions with the appropriate parties. Action is taken as appropriate, the call closed off and contact made with the person who contacted MDC.