Septic Installation & Cesspool Conversion in Fern Acres
We install septic systems and convert cesspools in Fern Acres, roughly 20 to 25 minutes from our equipment yard in Keaau, depending on which end of the subdivision you’re on. Fern Acres is a subdivision of uniform 2-acre lots on private roads, and that layout shapes almost every septic job here.
Fern Acres at a Glance
- 1,965 residents and 858 housing units (2020 Census, Fern Acres CDP). In 2010 the count was 1,504 people and 704 units, so the population grew about 30 percent in ten years.
- About 2,000 lots of two acres each, according to the Fern Acres Community Association.
- 26 miles of privately owned roads, maintained with an annual road fee the association sets per lot.
- Elevation around 1,500 feet. The Census point for the area sits at about 1,532 feet.
- Rain: the association puts annual rainfall at about 160 inches, while the Rainfall Atlas of Hawaii draws its 180-inch line through the subdivision. Either way, it’s very wet.
- Lava: Fern Acres is one of the communities the USGS lists on Kilauea’s Ailaau flows from the 1400s. It falls in Zone 3 of the USGS lava-flow hazard map.
- Size: the census area covers about 6.8 square miles, bordered by Mountain View to the north, Hawaiian Acres to the east, Eden Roc to the west and the Puna Forest Reserve to the south.
Building on the Ailaau Flows
The ground under Fern Acres is Kilauea lava from roughly 1410 to 1460 AD. The USGS describes the Ailaau eruption as the largest Kilauea lava flow on land, about 166 square miles of mostly pahoehoe that moved through a huge tube network, including Kazumura Cave. Six hundred years is not long for soil to build up on lava, even in 160-plus inches of rain.
For a septic system, that usually means:
- Rock comes up early. State rules have the engineer examine the ground to a depth of 5 feet and test how fast it absorbs water. On young pahoehoe, the hole often hits rock well short of that.
- Soil replacement is common. When the test finds fractured lava, the rules call for replacing it with suitable fill under the leach field and keeping 3 feet or more between the system and groundwater. In practice, that means excavating rock and trucking in material.
- Old tubes and voids. The USGS notes that much of the Ailaau lava drained out of its tubes, leaving caves behind. If excavation opens a void, the engineer needs to see it before the design is final.
- Fractured rock is a fast path down. Effluent can move quickly through cracked lava, which is why the rules want a soil layer under the field.
Some owners also look at an aerobic treatment unit (ATU). An ATU still needs a disposal area, and it comes with a service contract and an inspection every six months, so it’s a long-term commitment.
Two Acres Gives You Room
Two-acre lots are a real advantage. At about 87,000 square feet, a Fern Acres lot has more than eight times the land the state asks for per system, and side-line clearances are rarely the problem they are on small lots.
That room matters because a typical Fern Acres property may have:
- A catchment tank. Puna’s subdivisions were laid out without central water or sewer, and catchment is the norm. The tank, its overflow and its water lines all need to stay clear of the leach field.
- An ohana or later addition. The state counts most rooms over 70 square feet as bedrooms and sizes the system at 200 gallons a day for each. A single system can serve no more than 5 bedrooms or 1,000 gallons a day, so a large main house plus an ohana may need a second system.
- A home that grew over time. If you’re not sure whether the house has a cesspool or a permitted system, a conversion starts by finding out what’s actually in the ground.
Building new? See our septic requirements for a new home before you finalize the house plan.
Private Roads, Long Detours
Fern Acres’ roads belong to the subdivision, not the county. The association collects a road fee from every lot to keep them up, and one recent listing describes the roads as paved. That helps when an excavator, a dump truck of fill and a concrete tank delivery all have to reach your lot.
What doesn’t help is how the subdivisions connect. A 2015 county subcommittee report on Puna connectivity found that upper Puna’s subdivisions along Highway 11 had no connections between them, so residents couldn’t travel parallel to the highway. It recommended links from Fern Acres to Hawaiian Acres and to the Kopua Farm Lots, plus finishing South Lauko Road into Fern Acres. A 2019 letter in the Hawaii Tribune-Herald described a gate the association installed in late 2018 at the end of Anthurium Street, between Fern Acres and Hawaiian Acres.
For your project, plan on equipment coming in from Highway 11. Tell us the best route to your lot and about any gate on the way.
Deadlines and Funding That Apply Here
Nothing about Fern Acres changes the statewide clock: Act 125 gives every cesspool until January 1, 2050. Selling the house doesn’t force the issue. A building permit for more bedrooms can, and so can a cesspool that keeps needing to be pumped or keeps backing up. Our Act 125 explainer has the full picture.
To see how your own cesspool is rated, use the UH Hawaii Cesspool Prioritization Tool, and our priority map guide explains the colors. For sewer, check with the county Department of Environmental Management.
On cost, most Hawaii conversions run about $20,000 to $50,000, and lava rock pushes toward the high end. Our conversion cost guide breaks it down. Owners with very low incomes can ask the USDA office in Hilo about Section 504 (1 percent repair loans up to $40,000, and grants up to $10,000 at age 62 and up). The state’s new Act 204 loan fund hasn’t opened yet.
Around Fern Acres
Get a Fern Acres Estimate
Tell us your street, how the house is laid out and whether there’s a cesspool now. We’ll look at the lot, the rock and the access, and work with your engineer on a design that will pass DOH review. Request a free estimate
Frequently Asked Questions
Will a regular leach field work on my Fern Acres lot?
It depends on the test pit. Fern Acres sits on Ailaau lava that’s only about 600 years old, so rock often shows up inside the 5-foot profile. When it does, the rules require a soil replacement system.
Who maintains the road to my lot, and does that matter for the job?
The Fern Acres Community Association maintains about 26 miles of private roads, funded by an annual fee on each lot. Good roads make it easier to bring in an excavator, tank and fill. Let us know about any gate on the way.
Is a 2-acre Fern Acres lot big enough for a septic system and an ohana?
Usually, for land area. The limit that matters more is flow: one system tops out at 5 bedrooms, and the state counts most rooms over 70 square feet as bedrooms.
I collect rainwater. How far does the leach field need to be from my catchment tank?
Your engineer will confirm the required distances for your design and place the field so the tank, its supply lines and its overflow stay well clear. Never let the overflow drain onto the field.
Can lava tubes under my lot affect the septic design?
It can. The Ailaau flows moved through a big tube network, and much of it drained out and left caves. If digging opens a void, the engineer needs to address it before the system goes in.
Do I have to convert my cesspool before selling my Fern Acres home?
No. A sale doesn’t trigger conversion under state law. Buyers and lenders may still ask about it, so read our buying and selling guide.