Septic Installation & Cesspool Conversion in Pepeekeo

We install septic systems and convert cesspools in Pepeekeo, about 30 minutes north of our equipment yard in Keaau. Pepeekeo ground the Hilo area’s last sugar, and that history still shapes septic work here: a county treatment plant serves one subdivision, older homes rely on cesspools, and a narrow scenic road with one-lane bridges leads to many lots.

Pepeekeo at a glance

  • 2020 Census: 1,826 residents in 609 households, the largest of the census places between Hilo and Honomu.
  • Location: About 7 miles north of Hilo on Highway 19, 3 miles past Papaikou and 3.5 miles short of Honomu.
  • Elevation: The Census reference point is about 564 feet, higher than the towns closer to Hilo.
  • Soils: The USDA’s Hilo soil series covers this coast below about 1,100 feet. Above that, the Kaiwiki series takes over, where rainfall runs 200 to more than 240 inches a year.
  • Sewer: The county’s Kulaimano Wastewater Treatment Plant serves the Kulaimano Heights development. Its 2024 permit notice put the population served at 1,800.
  • Sugar ended: Processing stopped at the Hilo Coast Processing Company site in 1994.

Where the sugar companies ended up

Pepeekeo’s plantation started as the Metcalf Plantation at Kaupakuea in 1857 and harvested its first crop in 1859. After 1874 it became Pepeekeo Sugar Company, and C. Brewer took control in 1904. Over the next 70 years the smaller neighbors folded into it. Honomu merged in March 1946, Hakalau in 1963, and the whole operation became part of Mauna Kea Sugar in 1973. As the Wainaku and Hakalau mills closed in the 1970s, the Pepeekeo mill was modernized to roughly double its capacity, and cane from up and down the coast came here to be ground.

Sugar processing on the Hilo Coast Processing site ended in 1994. The site’s power plant then burned coal for the island grid until 2004.

What that means for homeowners: Pepeekeo has a mix of older plantation-era homes and later subdivision housing. The older houses are the ones most likely to still sit on a cesspool.

Ash, rain and elevation

Pepeekeo sits on the windward flank of Mauna Kea, on lava flows 100,000 to 300,000 years old buried under weathered volcanic ash. That is a very different site from the young pahoehoe in Puna. Both the Hilo and Kaiwiki soil series are described as deep, with 44 to more than 60 inches to bedrock and well drained.

For septic, Pepeekeo lots differ from Puna in a few ways:

  • Elevation changes the rain. A lot near the highway and a lot well mauka can see very different rainfall. The Kaiwiki series above 1,100 feet forms under 200 or more inches a year, so upper lots stay wet longer and leach field work has to be timed around the weather.
  • Deep soil can open up options. Hawaii’s rule that requires a soil replacement system applies to fractured lava. Where the engineer’s 5-foot soil profile finds ash instead, a standard tank and leach field may be possible. The perc test decides.
  • Gulches still cut through. The USDA notes that the Hilo series can reach 200 percent slope in gulch areas. Lots that back onto a stream need the 50-foot setback to streams and careful excavation near the edge.

Slope limits that shape Pepeekeo designs

Under HAR 11-62, a trench system can’t go on ground steeper than 12 percent, and an absorption bed is limited to 8 percent. On lots steeper than 12 percent, a seepage pit is the allowed alternative, set at least 9 feet from the property line.

Sizing follows the bedroom count: 200 gallons per day per bedroom, with a 1,000-gallon minimum tank for up to four bedrooms. Any room of 70 square feet or more is presumed to be a bedroom, so an old plantation house with an enclosed lanai or an added room may be counted as larger than its owner expects.

Kulaimano Heights and the sewer question

Pepeekeo is one of the few places on our map with its own county sewer plant. The Kulaimano plant gives secondary treatment and discharges through an ocean outfall near Waimaauou Stream. In 2024 the EPA and the county signed an administrative order covering three plants not meeting EPA standards, and Kulaimano was one of them. In December 2021 the county reported a discharge from the plant that reached coastal waters off Pepeekeo town.

If your home is in Kulaimano Heights, you may already be connected and have nothing to convert. If you are outside it, don’t assume either way. Ask the County Department of Environmental Management whether a sewer main reaches your parcel before you commission a septic design.

The road in

Most Pepeekeo lots are reached from Highway 19, but a good number sit on the Four Mile Scenic Drive, the old Mamalahoa Highway alignment between Papaikou and Pepeekeo. It is narrow and curvy, with about half a dozen one-lane bridges and hidden driveways. We check that route for the excavator trailer and tank delivery truck before scheduling a job. From Hilo, the south end of the drive starts shortly after mile marker 7, and the north end comes out at Kulaimano Road between mile markers 10 and 11.

Rules and money for Pepeekeo owners

Every cesspool must be upgraded, converted or connected to sewer by January 1, 2050 under Act 125. New cesspools have been banned statewide since 2016. A home sale doesn’t force a conversion, but adding bedrooms through a building permit can. Our explanation of Act 125 covers the details, and our step-by-step conversion guide explains the engineer, Department of Health review and county permit sequence.

Low-income owners should ask the USDA’s Hilo office whether they qualify for a Section 504 repair loan or grant. The state’s Act 204 loan fund is expected to open in late 2026 but isn’t taking applications yet. More on both is in our grants and loans article.

Other towns along this coast

South toward Hilo, see Wainaku, Paukaa and Papaikou, which has its own county plant. North of Pepeekeo, Honomu is the next town up Highway 19, and Hakalau was one of the mills that merged into Pepeekeo Sugar. The Hilo septic services hub covers the whole district.

Get a look at your Pepeekeo lot

Whether you are in an old camp house near the highway or on a sloping lot off the scenic drive, we can look at the ground, the access and the sewer question, then bring in the engineer. Request a free estimate

Frequently Asked Questions

I live in Kulaimano Heights. Do I need to worry about the 2050 cesspool deadline?

If your home is connected to the Kulaimano treatment plant, the cesspool law doesn’t apply to you. If you aren’t sure, check with the County Department of Environmental Management before assuming.

Can a septic tank truck get down the Four Mile Scenic Drive?

The road is narrow with several one-lane bridges, so it takes planning. We check the route and the turn into your driveway before scheduling delivery.

My lot is high above the highway. Does that change the septic design?

It can. Above about 1,100 feet the soil is mapped as Kaiwiki series, with 200 or more inches of rain a year. Wetter ground affects the perc test, the trench schedule and sometimes the choice between a leach field and an aerobic unit.

Is Pepeekeo in a cesspool priority area?

Pepeekeo isn’t named separately in the Department of Health’s 2017 report. Check your parcel on the University of Hawaii cesspool prioritization tool to see its rating. The 2050 deadline is the same everywhere.

Will my old plantation house need a bigger septic system than I expect?

Possibly. Systems are sized at 200 gallons per day per bedroom, and any room of 70 square feet or more is presumed to be a bedroom. Enclosed porches and added rooms can push the count up.

Do I need a seepage pit on a steep Pepeekeo lot?

Only if no part of the usable area is 12 percent or flatter for trenches (8 percent for beds). The engineer usually looks for a level bench first.