Steep Maine Hillside Requires Carving a Flat Drainfield Bed

Jackson Excavating worked machines carefully in sandy loam while battling a 15% grade during installation of an Eljen system

Steep Maine Hillside Requires Carving a Flat Drainfield Bed

 The Eljen units in South Thomaston, Maine, sit on 6 inches of washed sand, with the rest of the bed built with coarse septic sand. (Photos courtesy of Jackson Feener)

The house about a half-mile from the Atlantic Ocean had a system dating to sometime in the 1950s. There was a stone bed for the drainfield, and it was time for a replacement, says Jackson Feener, the installer hired for the project. Feener runs Jackson Excavation in South Thomaston, Maine, also the location of the property where he installed this system. 

The tricky part of the installation was not the system components but a steep hill. With heavy woods on the land, the new onsite system was placed on the hill that drops from the house to a local road. 

System overview

Wastewater exits the house in 4-inch Schedule 40 PVC pipe and reaches the first treatment step, a 1,000-gallon concrete tank from American Concrete in Bangor, Maine. There is a baffle on the inlet and an effluent filter on the 4-inch outlet.  

From the tank, pipe runs about 9 feet and then drops 12 feet down the hill to an Eljen GSF drainfield. There it changes to Schedule 25 pipe. Because this system is on a hill, the only pressure on the pipe will come from mowing grass, Feener says, so there was no need for the client to pay for the extra strength of Schedule 40 pipe. 

The drainfield is divided into two sections, Feener says, “because it’s on a hill and you don’t want it to be this big mound sticking out of the ground.” Dividing the drainfield, and stepping the two sections down the hill, allows the system to blend into the contour of the land.

In total, the sand bed for the Eljen units is 9 feet wide and 28 feet long. A 4-inch perforated pipe runs the length of the first section. In the middle of the first bed is another length of 4-inch pipe, that allows effluent to flow down about 4 inches to the second bed.

To build the sand bed, Feener cut a shallow rectangle in the hillside. There’s a 5-foot toe on the uphill side and a 23-foot toe running downhill.

Eljen units sit on 12 inches of sand or mixed sand. At the transitional horizon beneath the units, he says, he blended native soil with coarse septic sand (free of rocks but not washed) to a depth of 6 inches so treated water is not stalled by suddenly hitting a different material. Under the GSF units only, Feener uses 6 inches of washed sand. The rest of the bed is built with the coarse septic sand. Cover is about 12 inches of sand topped with 6 inches of loam.

The only piece of equipment Feener used was his 2016 Cat 307E2 mini-excavator with a tilt bucket and thumb, and steel tracks with rubber pads. 

“Great little machine,” he says. “The rubber plates, you bolt them on to the steel plates, and you can run over pavement, run over lawn, and it’s minimal impact. But in the wintertime, up here in Maine, as soon as we get a little snow and ice they’re useless.”

Joining Feener in doing the work were his father Joseph Feener and his brother Ryan Feener. 


There was an old septic tank on the property. 

“I crushed the old septic tank up, and filled the hole with sand, and put the new septic tank in a new location,” he says. 

He had to dig down quite a bit for the drainfield, he says. That meant about 18 inches below the planned sand layer for one section of the drainfield, a little deeper beneath the other section. Then he built up with sand. Feener buys his washed sand from State Sand & Gravel in Belfast, Maine. 

Working on the hillside was another problem to solve. 

“My machine is great, but it does not have a huge amount of reach,” Feener says. And he likes the ability to drive all around a drainfield and spread material so his crew doesn’t have to push wheelbarrows of sand all around. 

To get access on this job, he used the spoils dug from the sand bed excavation to build a temporary road wide enough for his mini-excavator to drive on. He’s worked on hills before, he says, but never on such a steep slope. Grade was 15.5%. There were trees, but nothing he felt comfortable using as an anchor for his 18,000-pound mini-excavator.

Before the tank was delivered, Feener says he measured the space available. The crane truck was able to back within 5 feet of the hole. “I had to set one of his outriggers on the bucket of my excavator because it was such a bad drop-off. There was no earth underneath for him to put pressure on.” 

Properly speaking, that shouldn’t be done, he says, but it was necessary to do the work.

Feener is an old hand at installing Eljen systems. For 2021, he says, his company will probably install about 15 of them. “We live so close to the coastline, most of the designers around here won’t give you anything else but an Eljen bed,” he says. 

Rock beds may be simple, but they require a tremendous amount of space, he says. An Eljen system can fit into small spaces. 


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