Use case · Cesspool, wastewater & water-side regulatory screening
Know the parcel's wastewater situation — and the full water picture around it — before it becomes a 9-foot hole.
Act 125 mandates conversion of every Hawaiʻi cesspool by 2050 — and a conversion is a deep excavation. KILO classifies the parcel against the cesspool, septic, and sewer record, flags where that dig runs into cultural-resource exposure, and now reads the surrounding water context: BWS Pass / No-Pass, CWRM aquifer + GWMA, the SDWA UIC line, the upstream watershed cesspool load, the nearest nearshore monitoring, the nearest WWTP ocean-discharge mixing zone, and the federal water-related construction permits the project will trigger.
Every Hawaiʻi cesspool is a conversion owed — and the conversion is rarely just plumbing.
Act 125 (2017) requires every cesspool in Hawaiʻi to be converted or upgraded by 2050 — roughly 88,000 statewide, 8,135 of them documented on Oʻahu. A conversion is not a paperwork exercise: it is a ground-disturbance event that can reach 9 feet or more.
In coastal sand substrate — exactly where many of those cesspools sit — that depth is the documented setting for inadvertent iwi kūpuna discoveries (Wainiha 2021 and multiple Oʻahu coastal incidents). A septic system compliant today can fail HAR §11-62 as the water table rises. And the conversion gets meaningfully more invasive on parcels where the BWS forces an aerobic-treatment-unit replacement, where the DOH Safe Drinking Water Branch UIC line requires protective-zone design, or where high upstream cesspool density creates accelerated-timeline pressure. The wastewater question pulls in the freshwater-supply question and the nearshore water-quality question right behind it.
What the screen returns
Which wastewater outcome attaches to the parcel.
KILO cross-references three authoritative datasets — the HCPT 2022 cesspool inventory, DOH 2008 OSDS coverage, and C&C Honolulu sewer mains — and classifies the parcel's on-site wastewater situation, with the realistic disturbance footprint that follows from it:
Wastewater classification · live for every Oʻahu parcelFive outcomes, one signal
Cesspool documented (HCPT 2022)Cesspool replacement · mandatory by 2050 under Act 125HIGH
Cesspool in DOH OSDS only (HCPT gap)Cesspool replacement · older registrationHIGH
Sewer mains within ~100mSewer-lateral connection · smallest plausible footprintLOW
No sewer, no on-site documentedLikely septic for new constructionMOD
Sources: HCPT 2022 · UH Water Research Center / DOH — including its census-block conversion-priority ranking. DOH OSDS 2008 · Hawaiʻi DOH Source Water Protection Program. Sewer mains · City & County of Honolulu.
When the math fails the ordinance
A septic compliant today can still fail by 2050.
HAR §11-62 requires vertical separation between a leach field and the water table. As sea level rises, that buffer shrinks. KILO projects the separation for a coastal cesspool parcel under each SLR scenario:
Worked example · A representative coastal cesspool parcelHCPT depth-to-water 2.5 m
Current separationToday1.00 mCOMPLIANT
@ 1.1 ft SLRHanalei 1:1 model0.66 mFAILS
@ 2.0 ft SLRSLR-XA scenario band0.39 mFAILS
@ 3.2 ft SLRSLR-XA scenario band0.02 mFAILS
HAR §11-62 · Hawaiʻi DOH. Groundwater-rise model from The Hanalei Initiative, Wastewater Management Plan (Feb 2026); generalization to coastal Oʻahu per Habel et al. 2017.
When the conversion will be more invasive
The friction signals that make the cesspool cascade harder.
The cesspool record is the start. The replacement design is governed by where the parcel sits in the freshwater-protection regime — and parcels in a friction context end up with a more invasive conversion: deeper trench, additional protective-zone design, or an accelerated timeline. KILO now reads three friction signals alongside the cesspool flag, and amplifies the cesspool-cascade reading (modestly, capped) when they stack:
Cesspool conversion-intensity friction signalsA modest, capped adjustment on cesspool parcels — no single signal flips a band
No-Pass BWS groundwater-protection zone (BWS §3-301)ATU replacement typical instead of conventional septic — deeper tank base, larger excavation footprint
Above the SDWA UIC line (DOH Safe Drinking Water Branch)Protective-zone design adds liner + monitoring wells + larger setbacks from leach field
The cesspool conversion-intensity amplifier fires only when a cesspool is documented; no cesspool means no firing. Bounded contribution — won’t single-handedly flip bands; solidifies borderline coastal-cesspool-belt parcels (Mokulēʻia, Sunset Beach, Punaluʻu, Hauʻula) where the conversion will genuinely be more invasive than a like-for-like replacement.
Companion water-supply read
Can this parcel actually get drinking water?
Wastewater is half the question. The other half is whether the parcel has a viable path to a potable water connection. KILO synthesises the BWS Pass / No-Pass coverage, the DOH SDWA UIC Line position, the DLNR CWRM aquifer + GWMA designation, and the Conservation district overlay into a single feasibility verdict — surfaced as a companion card on every assessment:
Water Supply Feasibility · four tiersSynthesised from BWS / UIC / CWRM / Conservation — non-scoring
BWS-EXTENDABLEService area but with §3-301 / UIC / GWMA frictionLonger commitment-letter cycle, possible conditions (post–Red Hill ʻAiea-Hālawa / Lanikai pattern)FRICTION
WELL-REQUIREDOutside BWS service areaDOH SDWA well permit + setback math vs. cesspool / septic / leach fieldWELL DEPENDENT
BWS doesn’t publish a service-area polygon, so Pass / No-Pass coverage is the proxy for “inside service area.” CWRM aquifer-system map + designated GWMAs per HRS §174C-41. SDWA UIC Line per Hawaiʻi DOH Safe Drinking Water Branch.
Companion water-quality read
Is the water next to this parcel polluted?
For coastal and stream-adjacent parcels, KILO surfaces the nearshore water-quality picture two ways. First, the HDOH Clean Water Branch monitoring-site catalog overlaid with the Surfrider Foundation BWTF 2025 Hawaiʻi Water Quality Report chronic-exceedance roster — eight Oʻahu sites exceeded the recreational health standard more than 50% of the time in 2024-25 (Punaluʻu Beach Park 100%, Kuliʻouʻou 80%, Waiāhole Beach Park 61%, and others). Second, the HCPT cesspool inventory read against each receiving watershed — surfacing the upstream cesspool load draining toward the receiving water. The causal narrative behind the chronic-exceedance picture.
Coastal parcels along Mamala Bay (Kakaʻako → Ala Moana → Waikīkī → edge of Diamond Head) additionally see the nearest WWTP ocean-discharge mixing zone. The Sand Island Deep Ocean Outfall discharges 90 MGD of treated effluent 2 miles offshore; the EPA NPDES permit allows bacteria counts at the discharge port roughly 220× the recreational health standard, engineered to dilute back to compliance at the Zone of Initial Dilution boundary. Brown-water plume events and persistent low-level dilution affect the shoreline parcels — material for any coastal-amenity or STR underwriting.
Permits the project will trigger
Stormwater, grading, and the federal water-permit cascade.
KILO now also surfaces the federal and county water-related construction permits any ground-disturbing project on the parcel will have to clear. Both panels frame the triggers honestly — they fire on parcel-level proximity / size as a coarse first read, but real applicability turns on the project’s actual disturbed-area footprint and whether earthwork crosses a regulated water.
Construction-permit triggers · screen at the parcel levelNon-scoring; regulatory context for the developer
C&C Honolulu Grading Permit (ROH §14-2)Triggers at 5,000 sq ft disturbed or 1,000 cu yd graded — almost any earthwork≥ ~0.1 ac
EPA NPDES Construction General Permit (40 CFR §122.26 / HAR §11-55)NOI + SWPPP required before ground-breaking; paired with C&C ESCP under ROH §14-13≥ 1 ac
Clean Water Act §401 (DOH Water Quality Certification)Required for any federal-permit activity that may discharge to a regulated water (parcels near a documented Oʻahu perennial stream)§401
Clean Water Act §404 (USACE Honolulu District)Discharge of dredged or fill material into waters of the U.S. requires individual or Nationwide General Permit§404
Hawaiʻi Coastal Zone Management — SMA Use Permit (HRS §205A)Parcels inside the Special Management Area need a county SMA Use Permit (Minor or Major)SMA
Hand-curated seed of 13 major Oʻahu perennial streams (Mānoa, Pālolo, Nuʻuanu, Kalihi, Moanalua, Kaukonahua, Anahulu, Waiāhole, Punaluʻu, Kahana, Kāneʻohe, Heʻeia, Waimānalo). Smaller intermittent channels and undocumented wetlands aren’t on the layer yet; USACE jurisdictional determinations remain authoritative.
How it works
Three steps, before the dig.
01
Classify the parcel
Enter the TMK; KILO places the parcel against the cesspool, septic, sewer, BWS, CWRM, UIC, watershed, and WWTP-mixing-zone record.
02
See the real footprint
The disturbance depth a conversion forces, the friction signals that amplify it, the cultural-resource exposure at that depth, and the federal + state permits the project will trigger.
03
Plan the conversion + the rest of the water work
Budget the excavation, the monitoring, the BWS commitment cycle, and the federal permit cascade before Act 125's deadline sets the schedule for you.