Septic Installation & Cesspool Conversion in Honomu
We install septic systems and convert cesspools in Honomu, about 35 minutes from our equipment yard in Keaau. Honomu differs from the towns closer to Hilo in one plain way: a state environmental assessment reports no county sewer lines in Honomu town at all. Every home here is on an individual wastewater system, which means a cesspool, a septic tank, or an aerobic unit.
Honomu in numbers
- 2020 Census: 452 residents in 184 households.
- Location: Highway 19 runs through town, 11 miles north of Hilo. Route 220 branches off through the middle of town and climbs 3.8 miles to Akaka Falls State Park.
- Elevation: About 300 feet at the Census reference point. Homestead land mauka of town runs from about 400 to 1,250 feet.
- Rainfall: A 2018 Department of Hawaiian Home Lands environmental assessment put mean annual rainfall on its Honomu land at about 205 inches.
- Water: The County Department of Water Supply runs the Honomu Water System for the village. The new homestead lots above town are planned around rain catchment.
- Sewer: None in town, per that same assessment. Wastewater is handled by cesspools and septic systems.
A sugar town since 1880
The Honomu Sugar Plantation was established in 1880 on 2,400 acres by M. Kirchoff and Company, with C. Brewer as agent. In 1946 the Honomu mill closed and operations merged into Pepeekeo Sugar. The mill site sits downhill toward the ocean, and some of its structures still stand under roots and vines. Today the town is small, with fewer than 200 households, and much of its trade comes from Akaka Falls visitors.
For septic, Honomu’s history means two things. Many houses in the village date from the plantation era and were built when a cesspool was the standard. And because there is no sewer to connect to, every one of those cesspools has to become an on-site system before 2050.
Three soils, very different behavior
The Honomu assessment mapped three soil types on its land above town, and they are a good guide to what an engineer may find on lots in the area:
- Kaiwiki silty clay loam: Well drained ash soil, 44 to more than 60 inches deep over lava that is 100,000 to 300,000 years old. Of the three, this is usually the easiest ground for a leach field.
- Akaka silty clay loam: Found on footslopes and toeslopes. The USDA describes it as moderately well drained with moderately slow permeability, and very slow permeability in the bedrock below. A leach field in Akaka soil may need more trench length, or an aerobic treatment unit may make more sense.
- Rough broken land: The gulch sides, at 35 to 75 percent slope. No conventional disposal field goes here.
With rainfall near 205 inches a year, Honomu soils rarely dry out. That affects the percolation test, which a Hawaii-registered engineer runs along with a 5-foot soil profile, and it affects when we can open trenches without smearing the ash.
Gulch edges and the slope rules
Gulches cut through the land around Honomu, and many lots slope toward one. HAR 11-62 limits leach field trenches to 12 percent slope and absorption beds to 8 percent. Steeper than 12 percent, a seepage pit is permitted instead, with at least 9 feet to the property line. Any disposal area must stay 50 feet back from a stream. On a lot that ends at a gulch rim, the stream setback often decides where the system can go before the slope does.
What Honomu homeowners usually need
Typical projects here include:
- Converting a plantation-era cesspool in the village, often on a small, older lot. Lots recorded before August 30, 1991 are exempt from the 10,000 square foot per system rule, which helps here.
- New systems on homestead lots. The Department of Hawaiian Home Lands awarded 16 one-acre subsistence agricultural lots at Honomu in November 2024 and planned 40 more. Its assessment states cesspools won’t be allowed there, so each new home needs a septic system or aerobic unit from the start. Our guide to septic requirements for a new home covers that process.
- Systems for businesses on the highway. Shops in town that serve Akaka Falls visitors have higher daily flows than a house, and a single system is capped at 1,000 gallons per day. Commercial jobs usually need an engineer to size the flow first.
Driving up to Honomu
From Keaau we run through Hilo and north on Highway 19, then turn into town. Lots along Route 220 share the road with Akaka Falls visitor traffic, so we try to schedule deliveries early in the day. Older village side streets can be tight for an excavator trailer, and we check every route before booking a tank delivery.
The 2050 deadline in a town without sewer
Act 125 requires every cesspool in Hawaii to be upgraded, converted or connected to sewer by January 1, 2050. With no sewer in Honomu, connecting is not an option, so every remaining cesspool here will need an on-site system. Honomu isn’t one of the communities named in the Department of Health’s 2017 priority report, but priority status doesn’t change the deadline anyway. Our Act 125 explainer walks through the rule and its triggers.
On this coast, slope, access and soil tend to drive cost more than lava rock does. For low-income owners, USDA Section 504 repair loans and grants may apply, so check eligibility with the USDA office in Hilo. Our grants and loans page lists what is open now and what is still coming.
Nearby towns on the Hilo coast
Next door to the south, Pepeekeo absorbed the Honomu plantation in 1946. To the north, Hakalau sits at the bottom of a deep gulch. Closer to Hilo, see Wainaku, Paukaa and Papaikou. Our Hilo septic services page covers the district.
Plan your Honomu project
Whether you are replacing a village cesspool or building on a new homestead lot above town, we can look at the ground, the slope and the access, and coordinate with the engineer. Request a free estimate
Frequently Asked Questions
Can I hook up to county sewer in Honomu instead of putting in septic?
A 2018 state environmental assessment reports no county sewer lines in Honomu town. To confirm for your parcel, ask the County Department of Environmental Management, but plan on an on-site system.
I was awarded a DHHL lot in Honomu. Can I use a cesspool to start?
No. New cesspools have been banned statewide since 2016, and the homestead assessment says cesspools won’t be allowed. You’ll need a septic system or an aerobic unit designed by an engineer.
Does the heavy rain in Honomu affect septic design?
Yes. Rainfall near 205 inches a year keeps the soil wet, which affects the perc test, trench sizing and construction timing. In slower soils like the Akaka series, an aerobic treatment unit is sometimes the better fit.
My Honomu lot backs onto a gulch. Where can the leach field go?
At least 50 feet from the stream, on ground no steeper than 12 percent for trenches or 8 percent for beds. If no such ground exists, a seepage pit may be allowed on steeper ground.
Does my shop on the highway need a different system than a house?
Often it does. A single system is capped at 1,000 gallons per day, and an engineer estimates the daily flow from how the building is used.
Is my Honomu home a high priority for cesspool conversion?
Honomu isn’t named in the state’s 2017 priority list. Check your parcel on the University of Hawaii prioritization tool. The deadline is January 1, 2050 either way.