Borehole / Groundwater (community-scale water backstop)

Borehole / Groundwater (community-scale water backstop)

EDT domain: d03_water_waste_circular

Definition

A community-scale groundwater bore — drill a hole to an aquifer and pump water up. In the NI water cascade (D22) it is the first local backstop: where roof rainwater + tank storage cannot meet demand, a bore supplies water from below ground. Its capex (drilling + pump) is one-off; its ongoing cost is the electricity to lift the water, which couples water supply to the energy model. It is constrained by aquifer availability and by regional-council water-take rules. CR_032

Role — local backstop, energy-cheap

• A local supply (unlike mains, it does not reduce self-sufficiency) and the energy-cheapest backstop where the aquifer is shallow — roughly an order of magnitude less energy per m³ than desalination. CR_032
• Its ceiling is regulatory and hydrological, not cost: the regional permitted-take limit, and whether accessible groundwater exists at all (good on the Canterbury/Heretaunga/Waimea plains, poor in much of Northland’s clay/volcanic and steep hill country). CR_032

Cost & performance (NZ)

• Drilling + casing capex: NZD 8,000–20,000 for a domestic/lifestyle-block bore (point estimate ~NZD 12,000); typical depth 20–80 m (shallow alluvial) up to 150 m+ (deep/hard-rock). A derived per-metre rate is ~NZD 150–350/m (low confidence — NZ drillers quote total installed cost, not a clean per-metre rate). Dry-hole risk is real: one owner report cites ~NZD 50k spent before water was found. CR_032
• Pump + pressure system capex (installed): ~NZD 4,500 (the submersible pump unit is NZD 1,000–1,500; the full installed figure with riser, pressure tank, controller, wiring and labour is trade-typical). CR_032
• Pump energy intensity (the water↔electricity nexus term): physics-governed — kWh/m³ ≈ 0.00272 × total_head_m ÷ wire-to-water_efficiency. At 50 m head and ~55% efficiency ≈ 0.25 kWh/m³ (20 m ≈ 0.10; 100 m ≈ 0.49). Scales linearly with head; the method is high-confidence, the head assumption medium. CR_032
• Drilling cost — named NZ quote (verified primary). Brown Bros (NZ) Ltd via Matamata-Piako DC (ref 25/26/172, 12 Nov 2025) for a 100 mm mud-rotary alluvial community bore at Waitoa: mobilisation + first 20 m 8,900**; mud rotary 20–100 m **285/m; air/tri-cone hard rock 305/m**; 80 mm PVC screen **650 per 6 m; water analysis 420/ea**; worked example 64 m bore **21,440 ex-GST (excl pump, permit, site works). The quote’s structure — fixed 8,900** + **285/m — scales with water-table depth. National ranges (via the synthesis): shallow 20–40 m NZD 12–20k; medium 40–80 m 18–30k; deep 80–150 m hard-rock 30–60k+. Community bores use 150 mm casing (+20–30% vs 100 mm) — so the CR_032 “~12k” point estimate is a shallow domestic bore and sits below a community-scale figure. OT_090 CR_045
• Community system CAPEX by size (indicative — no NZ survey): 5–10 HH 50–120k; 10–25 HH 80–200k; 25–50 HH 150–400k; 50–100 HH 300–700k+ (includes pump set, header/pressure tank, reticulation network 30–150k, treatment 10–40k, electrical/telemetry). Treat as order-of-magnitude only. CR_045
• Single-bore sustainable yield: typical rural 0.3–7 L/s (26–605 m³/day) — low 0.5–1.5, moderate 1.5–5, high confined 5–20 L/s. At ~0.75 m³/HH/day one moderate 150 mm bore serves 20–50 households; a second bore is prudent beyond ~40–50 HH or in shallow unconfined aquifers. CR_045

Regulatory / NZ context

• Permitted-take ceiling (region-specific, NOT national). Under RMA 1991 s14, water for reasonable domestic/stock drinking needs is permitted without consent (no national number); any larger take is governed by regional plans, which set a permitted-activity daily limit above which a resource consent (water-take permit) is required. The limit ranges ~5–50 m³/day: Bay of Plenty up to 35, Horizons <50, Waikato <15, Tasman >5 (10/20 in some zones). The frequently-cited single national ~20 m³/day figure is wrong. CR_032
• Over-allocation: many good-aquifer catchments (Canterbury, Heretaunga, Waimea) are over-allocated, so a new take may be refused even where water physically exists. Treat the permitted-take limit as a capacity ceiling on the borehole backstop unless a consent is modelled. CR_032
• Community supply always needs consent (the binding gate). RMA s14(3)(b) exempts only an individual’s reasonable domestic needs — it cannot be stacked across a multi-dwelling scheme (Auckland Council: communities “must get resource consent”). So a communal bore needs a water-take consent regardless of volume (unambiguous by ~20 HH / ~15 m³/day); the per-property permitted caps above do not aggregate. Separately, any supply serving ≥2 households must register with Taumata Arowai (DWQAR 2022). CR_045
• All-in consent cost NZD 25,000–35,000 typical (non-notified) — dominated by hydrogeological/AEE work + pump testing, not council fees (2–7k). Rises to 40–80k+ (notified) / 80–200k+ (public hearing). Annual compliance charges NZD 300–1,500/yr. Metering has a national 5 L/s trigger (RM Water Takes Regs 2010) — above the 5–100 HH community scale. CR_045
• Waikato drill-take pathway (primary): a WRC bore permit ($546.25, 2025/26) allows drilling + taking up to 15 m³/day; >15 m³/day from one bore triggers a separate water-take resource consent (with a longer pump test). The exact regional figure behind the ≥15 m³/day Waikato threshold. OT_090
• Two gates, not one (community supply). Beyond the RMA water-take consent, a communal bore feeding a shared reticulation is normally a registrable Taumata Arowai drinking-water supply (small networked = 26–100 people) unless designed within the ≤25-person shared-domestic carve-out — a parallel obligation with its own ongoing compliance. Auckland E7 permits only small takes (≤5 m³/day over 20 days, or ≤20 m³/day over 5 days + 5,000 m³/yr); an over-allocated catchment makes a new take non-complying / effectively prohibited → the community must fall back to rainwater/recycling. See regulatory_consenting_off_grid_nz. CR_046

Relevance to Neobiome (D22)

The first local backstop in the water cascade. When the seasonal water balance flags a deficit (water_risk), the bore is the first fallback tried: its capex enters total_capex, and its pump energy adds to the electricity demand denominator (pump_energy_kWh = volume_m3 × 0.00272 × head_m ÷ eff), coupling D22 → D01 — exactly the nexus logic that desalination shares (at ~16× the energy). The bore’s capacity is capped at the regional permitted-take limit unless a water-take consent is modelled. CR_032

Research targets

• Brown Bros/MPDC bore-drilling quote — filed as OT_090, the verified primary behind the drilling rates (RT_295 resolved).
• Waikato + ECan fee schedules (consent processing fees + annual charges) to firm the all-in consent cost (RT_296); a real NZ hydrogeology/AEE consultant quote for the dominant, still-estimated cost driver (RT_297).
• Residual on RT_260: an international community-scale groundwater cost/energy benchmark + the remaining 6 of 16 regions’ permitted-take limits (CR_045 delivered the verified driller quote + a 10-council table).

Connections

Links to

Sources (4): CR_032 · CR_045 · CR_046 · OT_090

EDT domains (1): D03: Water, Waste & Circular Systems

Concepts (1): Regulatory Consenting for Off-Grid Communities…

Referenced by

Sources (3): CR_032 · CR_046 · OT_090

EDT domains (1): D03: Water, Waste & Circular Systems

Concepts (1): Regulatory Consenting for Off-Grid Communities…