Septic Installation & Cesspool Conversion in Wainaku, Paukaa & Papaikou
We install septic systems and convert cesspools in Wainaku, Paukaa and Papaikou, roughly 25 minutes up Highway 19 from our equipment yard in Keaau. These three old sugar communities line the first few miles of coast north of Hilo, and the ground under them is nothing like the lava rock we dig in Puna. Here the questions are deep, wet volcanic ash, steep gulches, and whether a county sewer line already runs past your lot.
Wainaku, Paukaa and Papaikou by the numbers
- 2020 Census: Wainaku had 1,147 residents in 410 households, Paukaa had 434 residents in 188 households, and Papaikou had 1,166 residents in 424 households.
- Elevation: The Census points for the three sit at about 236 to 256 feet, though lots run from the sea cliffs well up into former cane land.
- Soil: The USDA maps the Hilo soil series along this coast: deep ash, usually 44 to more than 60 inches to bedrock, over Mauna Kea lava flows 100,000 to 300,000 years old.
- Rainfall: The Hilo series forms where rain runs 130 to more than 200 inches a year.
- Slope: That series is described on slopes of 0 to 35 percent, and up to 200 percent in the gulches.
- Sewer: The county runs a wastewater treatment plant at 27-2138 Hawaii Belt Road in Papaikou. Its permit notice says it serves about 1,900 people.
Ash soil instead of lava rock
On fractured lava, Hawaii’s wastewater rules require a soil replacement system, which is why Puna jobs often mean hauling in fill. For septic, Papaikou and its neighbors pose a different problem. The Hilo series is a hydrous silty clay loam formed from weathered ash, and the USDA rates it well drained, with fast water movement near the surface. In a U.S. Geological Survey study of ash deposits near Hilo, samples held water contents as high as 392 percent.
That has a few practical effects:
- The perc test decides the design. A Hawaii-registered engineer runs the percolation test and digs a 5-foot soil profile. In deep ash a conventional tank and leach field is often worth testing for, which is rarely true in Puna, but only the results can say so for your lot.
- We try not to dig wet. The USDA describes this soil as smeary. A trench cut in saturated ash can glaze over on the sides, so we watch the forecast before opening a leach field.
- Slopes need respect. The same USGS study found this ash holds steep faces when left alone but is prone to landsliding during earthquakes. We keep excavation back from gulch edges and don’t stack spoil where it loads a slope.
Gulch lots and the HAR 11-62 slope limits
Many homes here sit on a bench above a gulch or on a lot that falls toward the ocean. Hawaii Administrative Rules chapter 11-62 caps leach field trenches at 12 percent slope and absorption beds at 8 percent. Where a lot is steeper than 12 percent, a seepage pit is allowed instead. A seepage pit needs 9 feet to the property line rather than 5, and every disposal area must stay 50 feet from streams and the shoreline. On a narrow lot between a gulch and the highway, that can leave only one workable spot.
Plantation houses and what owners usually need
Onomea Sugar Company was formed in 1888 when the Onomea, Paukaa and Papaikou plantations combined. Its mill sat a short distance below Papaikou at the base of a gulch that opened to the sea. At Wainaku, the Hilo Sugar Company mill ran until December 1976, and the Nikai Camp there housed Japanese workers who arrived in 1885.
Typical projects owners ask about:
- Replacing an original cesspool that fills or backs up in the rainy months.
- Adding a bedroom or an ohana unit. A building permit that adds bedrooms can lead the Department of Health to require a cesspool upgrade, and any room of 70 square feet or more is presumed to be a bedroom.
- Converting before a sale. A sale does not trigger conversion by itself, but buyers and lenders ask. See our guide to selling a home with a cesspool.
One help for older lots: the rule that each system needs 10,000 square feet of land does not apply to lots recorded before August 30, 1991.
Check for a sewer line before you design anything
Unlike the Puna subdivisions where most of our work happens, this stretch has a county treatment plant. A 2024 administrative order between the EPA and the county named Papaikou as one of three Hawaii Island plants not meeting EPA standards, with its upgrade expected to go out to bid by March 2028 and finish by July 2031.
The permit notice does not map the plant’s service area, and we won’t guess which streets it reaches. Before paying for a septic design, ask the County Department of Environmental Management whether a sewer main fronts your property. If one does, connecting may be the simpler way to meet the cesspool law. If not, a septic system or an aerobic treatment unit is the likely path.
Getting equipment onto the lot
From Keaau we come through Hilo and north on Highway 19. The hard part is the last 100 feet: narrow side roads, driveways that drop steeply off the highway, and wet ash that turns a dirt drive slick. We check access on the site visit so the excavator and tank delivery fit the lot.
The cesspool law and funding
Under Act 125, every cesspool in Hawaii has to be upgraded, converted or connected to sewer by January 1, 2050. The Department of Health’s 2017 report named Hilo Bay a Priority 3 area, with about 8,700 cesspools draining to streams and groundwater that reach the bay. Priority level does not set an earlier deadline. To see how your lot is rated, our priority map guide walks through the University of Hawaii tool.
There is no state tax credit right now, and the Act 204 state loan fund is not open yet. USDA Section 504 repair loans and grants come out of the USDA office in Hilo, so check eligibility there if your household income is low. Our conversion cost article explains what moves the price.
Neighboring towns we serve
Just up the coast, Pepeekeo has similar ash soils. Farther north, Honomu and Hakalau are older mill towns with deeper gulches. For the wider area, see our Hilo septic services page.
Planning a project between Wainaku and Papaikou
If you own a home in Wainaku, Paukaa or Papaikou and want to know whether you are looking at a sewer connection, a leach field or a seepage pit, we can walk the property, check slope and access, and line up the engineer. Request a free estimate
Frequently Asked Questions
Is my house in Papaikou already on county sewer?
Possibly. The county plant in Papaikou serves roughly 1,900 people, but its service area isn’t published street by street. Call the County Department of Environmental Management with your tax map key and ask whether a sewer line fronts your lot.
Does the ash soil here mean I can skip the soil replacement system Puna homes need?
Often it can. The soil replacement requirement applies to fractured lava, and much of this coast has deep ash instead. The engineer’s soil profile and perc test decide, so wait for the results before planning around it.
My lot drops into a gulch. Can I still put in a leach field?
Trenches are limited to 12 percent slope and beds to 8 percent. If the only open ground is steeper than 12 percent, a seepage pit is allowed, with 9 feet to the property line and 50 feet from any stream.
Is Wainaku inside the Hilo Bay priority area?
The 2017 state report describes the Hilo Bay area by the cesspools draining toward the bay, not by street. Look up your parcel on the University of Hawaii prioritization tool. Either way, the deadline is January 1, 2050.
Does adding an ohana unit on my Paukaa lot mean I have to convert my cesspool?
It can. When a building permit adds bedrooms or wastewater load, the Department of Health may require the cesspool to be upgraded as part of that permit.