Big Fix: Failed Onsite System Requires Massive Overhaul

An elevated sand mound and directional drilling provide a quality solution for a failed system in violation of a Pennsylvania township code.
Big Fix: Failed Onsite System Requires Massive Overhaul
The rear door of a semi-trailer and other material cover the collapsed 350-gallon metal septic tank. (Photos courtesy of Thomas H. Erb and Sons)

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During a mandatory four-year pumpout and inspection at a three-bedroom home in Rapho Township, Pa., a service provider from Thomas H. Erb and Sons found the rear door of a tractor trailer and other material covering the collapsed 350-gallon metal septic tank.

A dye test revealed sewage flowing from a clay tile pipe that surfaced 50 feet from the septic tank, then running downhill to a stream. The condition continued for three years before the township issued a sewage violation and gave the owners 30 days to comply.

“When a copy of the violation notice arrived in June, we didn’t have a design or septic permit,” says installer Ray Erb, based in Lititz, Pa. “We also had to line up three extremely busy subcontractors and obtain a permit to cross the road.” Rainy weather and other unexpected situations extended what should have been a four-day install right up to the deadline.

Site conditions

Soils are silty clay loam with a percolation rate of 46 minutes per inch and a seasonal high water table at 46 inches. The property, a boarding stable, has a 4 to 6 percent slope.

System components

Erb designed the system to treat 400 gpd. Major components are:

  • 1,000-gallon single-compartment concrete septic tank. Tanks made by Monarch Concrete Products, York, Pa.
  • 500-gallon single-compartment settling tank with PL-122 Polylok effluent filter
  • 750-gallon single-compartment dose tank with 1/3 hp Goulds effluent pump
  • 55- by 18-foot elevated sand mound

System operation

Effluent flows by gravity through the first two tanks, then to the dose tank. The on-demand pump sends 225 gallons per cycle at 35 gpm through 2-inch Schedule 40 PVC pipe to the drainfield. A 2-inch manifold in the middle of the mound feeds effluent left and right to three 27.5-foot-long 1.5-inch laterals on 6-foot centers. Effluent disperses through 0.25-inch holes drilled 6 feet apart.


The only location for the tanks, set in series, had trees growing into overhead power lines running from the house to the stable. “Wires and trees had to come down, but coordinating the effort between the two contractors’ schedules was fun,” says Erb. “However, they knew our deadline and did their best to accommodate us.”

One week later, the electrical contractor arrived and found nothing to code. The only circuit breaker box had no main breaker to kill the power. “After a long, fruitless search for the breaker, he finally pulled the electric meter off its base and cut the wires,” says Erb. “Then we waited another five days for the tree surgeon to remove the trees.”

Knowing they’d hit water at 22 inches when excavating holes for the tanks, Erb had Monarch Concrete waterproof them before delivery. Son Tom Erb used a Gehl 383Z mini-excavator to dig close to the house, and just missed hitting a buried 1/2-inch flexible PVC water pipe running parallel with the trench. “Fortunately, Tom could excavate back and pull the line out of the way,” says Erb.

Water seeped slowly enough into the 7-foot-deep excavation for Erik Pinkerton to level 4 to 6 inches of gravel in the hole before the crane set the first two tanks. “Although the water line was just for the horses, we sleeved it in 1-inch flexible PVC pipe to meet code,” says Erb. “That left a 2-foot buffer between the tanks and line.” After plumbing the tanks, the workers backfilled them.

With room to maneuver, Tom Erb used a Caterpillar 312B excavator to dig a 10-foot-deep hole for the dose tank. Its side outlet enabled the supply line to run straight down the driveway and under the road before making two 45-degree turns toward the elevated sand mound 188 feet away. “The tanks never became buoyant,” says Erb. “The pressure from 3 feet of soil was sufficient to prevent them from floating.” Setting and plumbing the tanks took two days.

Erb hired L & N Zimmerman Excavating, of Newmanstown, Pa., to bore 50 feet under the road using a directional drill from Vermeer Corp. However, the land dropped 4 feet from the mound to the dose tank. To guarantee the bore bit achieved the proper elevation, workers excavated the bore hole 30 feet from a 9-foot-deep observation pit. The distance enabled the bit to maintain the proper pitch before leveling off and boring to the 5-foot-deep entry pit at the driveway entrance.

The machine operator then pulled back 3-inch HDPE pipe to sleeve the pressurized supply line. Meanwhile, Tom Erb and Pinkerton open-trenched from the dose tank to the entry pit and from the bore pit to the drainfield. “We planned one day for the bore, but it took half that long, enabling us to backfill the driveway pit and trench before nightfall,” says Erb.

To install the sand mound, workers scarified the soil, leveled the slope with 20 to 32 inches of sand, then covered it with 6 inches of 2B crushed stone. They laid the laterals and delivery lines, covering them with 2 inches of stone and geotextile fabric topped with 12 inches of soil. “We ran two dump trucks and brought in 120 tons of soil,” says Erb. “Fortunately, we had the tank excavation spoils to use when building the berm.”


The township’s management program requires cleaning and inspecting the tanks every four years.


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