EDT domain: d03_water_waste_circular
Definition
A connection to a council / Watercare reticulated (town) water main. In the NI water cascade (D22) it is the import backstop — the water analogue of an electricity grid connection: consuming mains water is an import and reduces self-sufficiency, exactly as importing grid electricity does (the D21 analogue on the water side). Capex is the connection + any development/growth charge + any pipe extension; opex is the volumetric tariff (where metered). CR_032
Role — import backstop, counts out of SSI
- The only non-local backstop: a community on mains is not water-self-sufficient for that volume. In the model it should reduce
water_ssi, not count as locally supplied. CR_032 - The grounded NZ pattern is partial reliance: Earthsong reticulates roof water for non-potable use but keeps drinking water on the city main, and the mains top-up is what makes its modestly-sized tanks workable (tanks “run dry several times each summer”). Mains is the safety net, not the primary supply. Interview VI [INT_006]
Cost & performance (NZ)
- Physical connection capex (tapping the main, meter, lateral to boundary): ~NZD 2,000–5,000, point estimate ~NZD 3,500 (council-specific, low confidence). CR_032
- Development / growth charge (a separate, much larger one-off for a genuinely new connection): Auckland’s Watercare Infrastructure Growth Charge = NZD 21,174.95 incl GST (combined water + wastewater) from 1 July 2024 — high confidence for Auckland, much lower or zero in many rural districts. CR_032
- Reticulation extension where no main is nearby: ~NZD 250–400/m of new main, open-trench rural (derived from adjacent NZ trenching rates, low–med). A community 1 km from the nearest main faces NZD 250k–400k — often enough to make mains the least viable backstop. CR_032
- Volumetric tariff (opex): Watercare NZD 2.296/m³ (2024–25) rising to 2.46/m³ (1 July 2025) — high confidence, Auckland. But many NZ councils are unmetered / rates-funded, so there is no per-m³ charge to apply; the “import cost” then shows up as an annual rate instead. CR_032
- Second metered-council anchor — Nelson (2025/26, GST-incl, primary). Nelson City Council’s statutory rates resolution sets a two-part water tariff: fixed NZD 273.42/yr per metered connection + volumetric NZD 2.764/m³ (residential tier ≤10,000 m³/yr; 2.349 to 100,000; 1.935 above; summer-irrigation 2.570/m³ >10,000). So the mains-import opex is
fixed + volumetric, not volumetric-only — and Nelson’s residential rate (2.764/m³) sits above Watercare’s 2.46/m³, giving a national metered range of ~NZD 2.46–2.76/m³ (⚠ normalise GST basis first) plus a ~NZD 273/yr fixed part where a council uses a two-part tariff. Wastewater is billed separately (flat NZD 708.57/SUIP), so a community importing water without network discharge avoids the wastewater line — the water-only vs wastewater separation the model needs. Nelson is fully metered, a second counter-example to “many councils are unmetered”. REG_030
Relevance to Neobiome (D22)
The import backstop in the water cascade — chosen only when the local options (rainwater, borehole) can’t meet demand and a main is reachable. Its connection + growth charge + extension enter total_capex; its volumetric tariff (or annual rate, if the council is unmetered) is opex; and crucially the imported volume counts OUT of water_ssi, mirroring grid_extension/grid_import on the electricity side (D18/D21). The per-metre extension cost is what usually rules mains out for a genuinely remote community. CR_032 Interview VI [INT_006]
Research targets
- A multi-council water-tariff sweep (Tasman, Nelson, Kāpiti, Christchurch) to build a national tariff range and quantify how many councils are unmetered — vs the single Watercare anchor (RT_261). Nelson leg delivered → REG_030 (two-part: NZD 273.42/yr fixed + 2.764/m³ residential, GST-incl; fully metered). Tasman/Kāpiti/Christchurch still open.
- Split the Watercare IGC into its water-only vs wastewater portions, for the case where the community imports water without discharging wastewater to the network (RT_261).
Connections
Links to
EDT domains (1): D03: Water, Waste & Circular Systems
Referenced by
EDT domains (1): D03: Water, Waste & Circular Systems