OT_110: Waimate District Council (2021) — Wastewater Asset Management Plan 2021–2031 (reticulated-scheme pipe base…

OT_110: Waimate District Council (2021) — Wastewater Asset Management Plan 2021–2031 (reticulated-scheme pipe base…

Source

https://www.waimatedc.govt.nz/ — original source (opens in a new tab; the file is not redistributed)

Waimate District Council (2021) — Wastewater Asset Management Plan 2021–2031

Primary read CORRECTS a CR_050 mis-attribution: the "80-yr" life is earthenware pipe (and one building), NOT concrete septic — and this is a reticulated municipal scheme, not septic infrastructure

RT_319 was raised to verify CR_050’s prose that “the Waimate DC AMP uses an 80-yr base life for concrete septic infrastructure.” The full read confirms the document is the Waimate District Council Wastewater AMP (not “Waimakariri”, the alternative CR_050 flagged), but the underlying claim is wrong on two counts. (1) The 2020-valuation base lives (Table 3-3) are earthenware 80 yr, PVC 100, MDPE 100, reinforced-concrete 60 — the only 80-yr figure is earthenware pipe, plus, separately, a single building at §3.8 (80-yr base life); reinforced-concrete pipe is 60 yr. (2) The scheme is a reticulated urban wastewater network (39.2 km pipe + oxidation-pond WWTP, $25.1m 2020 replacement value) — septic tanks appear only in the private St Andrews system, for which no asset life is stated. So “80-yr concrete septic” conflates the wrong material (earthenware/building) with the wrong asset class (buried mains, not tanks). Primary council document, figures read verbatim from the valuation tables → data_quality: verified.

Summary

The Waimate District Council Wastewater Asset Management Plan 2021–2031 (Version 3.2, May 2021, “Draft for comment”; authored with Waugh Infrastructure Management Ltd) is the statutory 10-year AMP for Waimate’s urban reticulated wastewater system. It documents the asset inventory (39.2 km of gravity + rising main, 10.7 km laterals, 308 manholes, a pond-based WWTP, two pump stations), the 2020 valuation (25.1m optimised replacement cost; 10.44m depreciated; $229,813 annual straight-line depreciation), condition and remaining-life profiles, renewal forecasts and financial provisions. Its NI value is a single reference table — Table 3-3, the economic (base) lives of buried wastewater pipe by material — which the CR_050 synthesis mis-read. The verified figures materially change how the source should be used: it corroborates that buried reticulation is long-lived (60–100 yr), making the engine’s 25-yr params.ASSET_LIFE wastewater very conservative for reticulation, but it supplies no on-site septic/AWTS tank life (the value CR_050 implied), so the septic-tank component-life gap stays open (RT_312).

Key claims

- claim: "Document identity & scope: 'Wastewater Asset Management Plan 2021–2031', Waimate District Council, Version 3.2, Issue Date May 2021, 'Draft for comment', Report Number 64-073-1024. AMP authors K. Zeelie (Waugh Infrastructure Management Limited) and Paul Roberts (Waimate District Council); Project Sponsor Dan Mitchell (Water & Waste Manager). Covers 'the Waimate urban wastewater system'. Confirms the RT_319 source is WAIMATE District Council (not 'Waimakariri', the alternative CR_050 flagged)."
  source_location: "Title / Quality Record Sheet (PDF p.2–3); §2.2 Assets Included in This Plan (p.18)"
- claim: "Economic (base) lives of wastewater pipe materials, as stated in the 2020 valuation (Table 3-3): Earthenware (EW) 80 years; PVC 100 years; MDPE 100 years; reinforced concrete (CON) 60 years. These are the base lives used for the buried reticulation network. The ONLY 80-year figure is earthenware pipe; reinforced-concrete pipe is 60 years — CR_050's 'Waimate AMP 80-yr base life for concrete septic infrastructure' is therefore a mis-attribution (wrong material AND wrong asset class)."
  source_location: "Table 3-3 'Economic Lives of Wastewater Pipe Materials', §3 Description of the Wastewater Services (p.31)"
- claim: "The other 80-year life in the document is a BUILDING, not concrete septic: 'There is one building individually valued with a replacement cost of $29,057. It has an equivalent base life of 80 years and is 25% through its life.' This is the source of the coincident '80 years' — a building, distinct from the earthenware pipe base life and unrelated to concrete or to septic tanks."
  source_location: "§3.8 Buildings (p.36)"
- claim: "The scheme is a RETICULATED municipal wastewater network, not septic infrastructure. Public asset inventory (Table 2-1): Reticulation — Pipe 39.2 km ($13.01m), Laterals 10.7 km ($5.9m), Manholes 308 ($2.7m); Plant — WWTP ($3.3m), Milford Pump Station ($0.1m); Total replacement cost $25.1m. Two pump stations plus three private pump stations. The WWTP is pond-based (oxidation ponds). Wastewater pipe assets range 'from new to 105 years of age.'"
  source_location: "Table 2-1 Summary of WW Assets (p.19); §3 Pipe Age (p.31); §3.7 Pump Stations (p.36)"
- claim: "The only septic tanks in the plan are a PRIVATE system, for which NO asset life is given: 'The Council also holds a resource consent for the St Andrews wastewater system... granted on 24 August 2017... duration of 15 years. This is a private system consisting of individual private septic tanks on each property. Council engage a septage disposal contractor to maintain each septic tank to meet the requirements of the consent.' (The 15 years is the resource-consent duration, not a tank asset life.)"
  source_location: "§2.2 Assets Included in This Plan (p.18)"
- claim: "2020 Valuation Summary (Table 8-1): total Optimised Replacement Cost (ORC) $25,095,833; Optimised Depreciated Replacement Cost (ODRC) $10,441,154; total Annual Depreciation $229,813. By component ORC/ODRC/annual-dep: Pipe $13,010,957 / $4,296,038 / $92,143; Laterals $5,920,000 / $1,843,525 / $78,448; Manholes $2,721,124 / $1,557,294 / $19,456; WWTP $562,893 / $355,436 / $14,828; Oxidation Ponds $2,052,682 / $1,715,704 / $15,168; Disposal Fields $727,800 / $595,605 / $7,488; Pump Stations $100,377 / $77,553 / $2,281."
  source_location: "Table 8-1 'Valuation Summary – Wastewater Services 2020', §8.4 (p.120)"
- claim: "Depreciation methodology: 'The decline in service potential is thus provided on a straight line basis on all fixed assets... Council complies with the requirements of FRS3 and NZIAS 16 and funds asset depreciation.' 'Annual depreciation is calculated by Council on a straight line basis – i.e. the replacement cost of the asset less its residual value over its useful life.' Assets revalued every three years. Asset useful lives are 'based primarily on book values with some adjustment for known risk factors,' to be refined toward evidence-based lives using condition and performance data."
  source_location: "§8.3 Depreciation (p.119); §8 Renewal and Operational Expenditure (p.123)"
- claim: "Remaining-life exposure (near-term renewal pressure): 'Approximately 18.6 km of earthenware pipe and 0.8 km of concrete pipe will reach the end of its expected economic life within the first five years of the Plan'; a further 'approximately 6.8 km of earthenware pipe and 0.35 km of concrete pipe' in the 11–15 year window. 10-year renewal requirement (Table 8-3) totals $7,756,546 (ww_line $7,556,636 + ww_plant $190,270 + ww_point $6,640), overwhelmingly in the 1–5 year remaining-life group ($7.47m)."
  source_location: "§3 Figure 3-6 discussion (p.31–32); Table 8-3 '10 Year Renewal Requirements' (p.123)"

NI relevance

RT_319 exists to verify one number that CR_050 fed toward params.ASSET_LIFE wastewater. The verified read changes how this source should be used, and the change is worth recording because it is exactly the “right org, wrong doc” cr_ failure mode the corpus guards against.

• The ‘80-yr concrete septic’ figure does not exist — correct the record. CR_050 prose (and the d03 evidence bullet derived from it) states “concrete septic 30–40 yr+ / Waimate AMP 80-yr base life.” The AMP has no such figure. Its 80-yr life is earthenware pipe (Table 3-3), with a second, unrelated 80-yr life on a single building (§3.8). Reinforced-concrete pipe is 60 yr. And the assets are buried reticulation mains, not septic tanks. The claim should be restated on CR_050 and D03 to: “Waimate DC AMP (reticulated scheme) — buried pipe base lives earthenware 80 / PVC 100 / MDPE 100 / reinforced-concrete 60 yr; no septic-tank life stated.”
• What it does legitimately support: buried reticulation is long-lived, so 25-yr wastewater life is conservative for reticulation. For any NI community design that includes a reticulated on-site sewer (gravity/pressure mains to a shared treatment point), these NZ-council base lives (60–100 yr, straight-line, FRS3/NZ IAS 16) are a solid primary anchor and confirm the engine’s 25-yr params.ASSET_LIFE wastewater is very conservative. The wide near-term renewal bulge here is an age artifact (a network with pipe up to 105 years old), not evidence that the base lives are short.
• What it does NOT support: the on-site septic/AWTS tank life NI actually needs. The likely NI “wastewater” asset for a small off-grid community is an on-site septic tank or AWTS (cf. CR_048: concrete tank 30–40 yr+, AWTS aeration motor 5–7, pump 8–10), not a council reticulation network. This AMP gives no tank life (its septic tanks are private St Andrews assets, life unstated). So RT_319 does not close the septic-tank component-life question — that stays with RT_312 (open, awaiting an IPWEA/NAMS-style or BRANZ component-life table).
• Provenance quality. This is a primary NZ council statutory document; the base-life table and valuation figures were read verbatim from the valuation tables → data_quality: verified. It upgrades the DH/septic-life evidence tier CR_050 assigned this row from “Tier-1 primary” (which it is) while correcting what the primary actually says.

Research targets

Documents to retrieve

• None new. The on-site septic/AWTS tank component-life need is already tracked by RT_312 (an IPWEA/NAMS or BRANZ component-life table) — this reticulated-scheme AMP does not fill it.

Research gaps

• RT_319 (RESOLVED → this page). Waimate DC Wastewater AMP 2021–31 retrieved and read verbatim. ⚠ CORRECTION: the AMP is a reticulated urban scheme; its base lives (Table 3-3) are earthenware 80 / PVC 100 / MDPE 100 / reinforced-concrete 60 yr, and the second 80-yr life is a building — there is no “80-yr concrete septic” figure. The verified figures supersede the CR_050 prose. params.ASSET_LIFE wastewater 25 yr is confirmed conservative for reticulation; the on-site septic/AWTS tank life remains RT_312 (open) — RT_312 now partially advanced by OT_158 (BRANZ SR351, fabric lines only; services/tank lives still open).

Connections

Links to

Sources (3): CR_048 · CR_050 · OT_158

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

Referenced by

Sources (1): OT_158

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