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

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Jan 19, 2024 306 likes •477 views

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

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Wellington Wastewater

PNRP evidence submission

Steve Hutchison 23 February 2018

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Wastewater system overview

4 catchments 2,367 km pipes 168 pump stations 412,000 popn. 140,000 m3/d

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Pipe age profile

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Metropolitan area growth forecast

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Disposal to land – Porirua example

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Rainfall impact on wastewater flows

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Example of storm event

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Unconsented wet weather overflows - CBD Overflow Chamber

Most frequent overflow Video from 20 Feb 2018

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Environmental monitoring example

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

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Uncontrolled manhole overflows

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Constructed manhole overflow

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Current overflow locations

Categorised by constructed

r uncontrolled

Categorised by receiving environment Most pump stations rarely

verflow but have facility to

Constructed overflows are best engineering practise for public health protection

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Current consents

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. WGN 12014 [33408] Discharge to Waiwhetu Steam during Main Outfall Pipeline repairs. WGN030100 [22447] Discharge wastewater to the CMA, when sewer operating at full capacity due to extreme wet weather, up to 70L/s. WGN060283 [25227] To occasionally discharge milli-screened (partially treated) effluent to the Wellington South Coast coastal marine area (Cook Strait in the vicinity of the Karori Stream Mouth) via an existing outfall during significant wet weather events. 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. Un-consented Overflows Location Description Wellington City  Karori - approximately 3 sites, about 6 constructed in network (2 treatment sites consented)  Tawa - approximately 6 sites surcharge  Churton Park - 1 site surcharges Lower Hutt  Wainuiomata - approximately 5 unconsented overflow sites operate regularly, and approximately 10 constructed sites in total  Western Hills - several sites, exact numbers unknown  Hutt Rossiter Ave - 1 site overflows to the Waiwhetu Stream Porirua  Approximately 25 sites overflow regularly, and up to 58 in total plus 40 pump stations All cities  All wastewater pump stations are potentially emergency discharge locations – approximately 120 sites in total

11 separate wet weather discharges consented 2 global stormwater consents Majority unconsented

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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 HCC_WW_114 Consented Overflows - Network HCC PCC_WW_114 Consented Overflows - Network PCC UHCC_WW_114 Consented Overflows - Network UHCC WCC_WW_114 Consented Overflows - Network WCC HCC_WW_75 Consented Overflows - Trunk Main HCC 5 5 2 11 1 4 3 7 38 5 5 2 11 1 4 3 7 38 HCC_WW_117 Non-consented Overflows - Network HCC 8 8 PCC_WW_117 Non-consented Overflows - Network PCC 10 12 13 1 14 10 13 3 76 UHCC_WW_117 Non-consented Overflows - Network UHCC WCC_WW_117 Non-consented Overflows - Network WCC 9 9 15 3 45 5 2 11 13 34 10 6 162 HCC_WW_76 Non-consented Overflows - Trunk Main HCC 2 1 3 19 21 28 4 61 5 3 11 23 55 13 6 249

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