Wellington Wastewater PNRP evidence submission Steve Hutchison 23 - PowerPoint PPT Presentation

Wellington Wastewater PNRP evidence submission Steve Hutchison 23 February 2018

Wastewater system overview 4 catchments 2,367 km pipes 168 pump stations 412,000 popn. 140,000 m 3 /d

Pipe age profile

Metropolitan area growth forecast

Disposal to land – Porirua example

Rainfall impact on wastewater flows

Example of storm event

Unconsented wet weather overflows - CBD Overflow Chamber Most frequent overflow Video from 20 Feb 2018

Environmental monitoring example E.Coli monitoring 24, 48 and 72 hours after an overflow

Uncontrolled manhole overflows

Constructed manhole overflow

Current overflow locations Categorised by constructed or uncontrolled Categorised by receiving environment Most pump stations rarely overflow but have facility to Constructed overflows are best engineering practise for public health protection

Current consents 11 separate wet weather discharges consented 2 global stormwater consents Majority unconsented Consented Overflows Consent ref Description WGN080003 [31506] To occasionally discharge up to 4500 litres per second of mixed disinfected secondary treated and milli-screened wastewater to the coastal marine area via an existing submarine outfall during and/or immediately after heavy rainfall, when the quantity of wastewater arriving at the Moa Point Wastewater Treatment Plant exceeds 3000 litres per second. Un-consented Overflows Location Description  Wellington City Karori - approximately 3 sites, about 6 constructed in network (2 WGN 12014 [33408] Discharge to Waiwhetu Steam during Main Outfall Pipeline repairs. treatment sites consented)  Tawa - approximately 6 sites surcharge  Churton Park - 1 site surcharges WGN030100 [22447] Discharge wastewater to the CMA, when sewer operating at full capacity due to extreme wet weather, up to 70L/s. Lower Hutt  Wainuiomata - approximately 5 unconsented overflow sites operate regularly, and approximately 10 constructed sites in total  Western Hills - several sites, exact numbers unknown WGN060283 [25227]  To occasionally discharge milli-screened (partially treated) effluent to the Hutt Rossiter Ave - 1 site overflows to the Waiwhetu Stream Wellington South Coast coastal marine area (Cook Strait in the vicinity of the  Porirua Approximately 25 sites overflow regularly, and up to 58 in total plus 40 Karori Stream Mouth) via an existing outfall during significant wet weather pump stations events.  All cities All wastewater pump stations are potentially emergency discharge locations – approximately 120 sites in total WGN960002 [23747] To intermittently discharge wastewater to the Hutt River downstream of Silverstream Bridge. WGN96002 [02] To intermittently discharge water to the Hutt River at Barber Grove Pump Station. WGN010101 [20893] To discharge sewage overflows from the Wellington Road pump station to the Black Stream during extreme wet weather events. WGN060283 [25228] To occasionally discharge secondary treated and disinfected wastewater from the WWTP to Karori Stream during events when the stormwater tank is full and the flow to the plant exceeds 190 L/s. WGN060283 [25229] To occasionally discharge milli-screened and settled wastewater from the WWTP to Karori Stream during events when the stormwater tank is full and the flow to the plant exceeds 390 L/s. WGN090321 [32525] To discharge untreated wastewater from the overflow structure at Malone Road, Lower Hutt to the Waiwhetu Stream.

2016-17 overflow frequency Wastewater Network Overflows for 2016/17 Ref Sub Category Council Jul-16 Aug-16 Sep-16 Oct-16 Nov-16 Dec-16 Jan-17 Feb-17 Mar-17 Apr-17 May-17 Jun-17 Tota for the year Consented Overflows - HCC_WW_114 HCC 0 0 0 0 0 0 0 0 0 0 0 0 0 Network Consented Overflows - PCC_WW_114 PCC 0 0 0 0 0 0 0 0 0 0 0 0 0 Network UHCC_WW_114 Consented Overflows - UHCC 0 0 0 0 0 0 0 0 0 0 0 0 0 Network Consented Overflows - WCC_WW_114 WCC 0 0 0 0 0 0 0 0 0 0 0 0 0 Network Consented Overflows - HCC_WW_75 HCC 0 5 5 2 11 0 1 4 3 7 0 0 38 Trunk Main 0 5 5 2 11 0 1 4 3 7 0 0 38 Non-consented HCC_WW_117 HCC 0 0 0 0 0 0 0 0 0 8 0 0 8 Overflows - Network Non-consented PCC_WW_117 PCC 10 12 13 1 14 0 0 0 10 13 3 0 76 Overflows - Network UHCC_WW_117 Non-consented UHCC 0 0 0 0 0 0 0 0 0 0 0 0 Overflows - Network Non-consented WCC_WW_117 WCC 9 9 15 3 45 5 2 11 13 34 10 6 162 Overflows - Network Non-consented HCC_WW_76 Overflows - Trunk Main HCC 0 0 0 0 2 0 1 0 0 0 0 0 3 19 21 28 4 61 5 3 11 23 55 13 6 249

Questions