Cesspools and Pre-Septic Systems

Why this matters

Before the septic tank and drain field became standard, a lot of houses sent their sewage into a hole in the ground. Many still do, and many more have an old pit that was taken out of use and never filled. These pits are covered with whatever was to hand eighty years ago: planks, a steel plate, a concrete slab, a dome of dry-laid brick with a foot of soil and grass on top. Covers rot and domes give way, and nothing on the surface warns you until a mower wheel, a skid steer or a person goes through into a pit of sewage and gas.

The rule that comes before anything on this card: no vehicle, no equipment and no person goes over an unexplained depression, soft spot or settled circle in the yard of an older house. You go around it, you mark it, and you find out what it is from someone whose job that is.

What you are looking at

• Cesspool: a covered pit that receives raw sewage straight from the house, with no tank ahead of it. Its walls are open-jointed (dry-laid stone, brick or block, or precast rings with holes) so liquid seeps out into the soil and solids stay behind. Solids accumulate, the soil clogs, and the old fix was to dig another pit beside it, so one house may have two or three in a row.
• Seepage pit: looks the same in the ground but sits after a septic tank and takes only liquid effluent. Some older systems have a tank and then a seepage pit instead of a drain field.
• Other pre-septic arrangements: privy vaults under old outhouse sites; dry wells of rubble or stone that took sink and laundry water (graywater) separately from the toilet; and straight pipes discharging to a ditch, a stream or a neighbor's field. All of them are holes or voids, and all of them are someone else's trade to investigate.

None of these can be confirmed from the surface. "Appears to be a cesspool or old pit" is what goes on your ticket.

How they show up on the surface

• A round or square depression, often a few feet to ten feet across, where the cover has sagged or the backfill has settled.
• A green circle: grass greener and faster-growing over the pit than the lawn around it in dry weather, or a soggy patch after rain.
• A sewer line leaving the foundation toward the yard (often cast iron or clay) with no septic tank lid, riser or drain field anywhere on the property. See related: Cast Iron Drain Lines and How They Fail.
• A concrete slab, steel plate or boards at grade in the yard with no obvious purpose.
• Odor near a spot in the yard, or drains that back up in wet weather.
• Paperwork that says "cesspool" on a seller disclosure, an old permit or a county record card. See related: Dating a House by What You Find in It.

The three hazards, and what each one demands

Collapse. This is the one that catches crews. A brick dome or a plank cover can carry a person for decades and then fail under a riding mower, a loaded wheelbarrow or the outrigger of an auger rig. The hole beneath can be six to ten feet deep or more, and its walls can keep caving after the cover goes. The control is distance: keep all loads, people and equipment off the suspected area and a margin around it, mark it with stakes and caution tape before work starts, and plan equipment paths that never cross it. Do not lay a sheet of plywood over a soft spot and treat that as a fix; you have hidden the hole and invited someone to stand on it.

Atmosphere. The pit holds decomposing sewage, which produces hydrogen sulfide, methane and carbon dioxide, and displaces oxygen. Hydrogen sulfide deadens the sense of smell at concentrations that injure, so a pit that stops smelling is not safer. Nobody enters an open pit or leans into its opening for any reason. Entry into a pit like this is permit-required confined space work, under 29 CFR 1910.146 for general industry or 29 CFR 1926 Subpart AA for construction, done by a trained crew with atmospheric testing, ventilation and an attendant. A dropped tool or phone is written off.

Sewage contact. Spoil from near a pit, a broken line or an exposed cover carries pathogens. Wear waterproof gloves for anything wet, keep hands off the face, wash before eating or drinking, and bag gloves before you get back in the truck.

And if someone goes in. Call 911 immediately and tell the dispatcher it is a sewage pit that may contain toxic gas. Do not climb in, and do not lie on the edge to reach in; would-be rescuers die in these pits as well. If you can extend a rope, ladder or pole from firm ground well back from the edge, do it. Keep everyone else back, because the edge that failed once can fail again. If a vehicle wheel breaks through, stop, get everyone off on the side away from the hole, leave the machine where it is, and cordon the area until the septic contractor and, if needed, a recovery operator assess it.

Why you do not lift the cover to find out

The obvious way to settle "is that a cesspool" is to pry up the slab or plate and look. It is the wrong move for a crew that is not the septic trade. A slab resting on a rotted frame can drop into the pit as it is levered, taking the person levering it onto the edge. Lifting it releases the gas that has collected under it straight at the face of the person bent over it. And a cover moved and set back slightly askew is now a hazard that looks repaired. The septic contractor opens it with a plan for all three; your job ends at the stakes and the tape.

The law, by layer

There is a federal floor and it does not reach most houses. Under the Safe Drinking Water Act's underground injection control rules (40 CFR Part 144), EPA banned new large-capacity cesspools in 2000 and required existing ones closed by 2005; a large-capacity cesspool is one serving 20 or more people a day, which covers multi-family and non-residential buildings and excludes a cesspool serving a single-family home.

The house rules are state and local, and they range from none to strict. As we understand them, and you should check the current text: Massachusetts requires a system inspection before most property transfers under its Title 5 code, and a system that fails must be upgraded; Rhode Island's cesspool law requires a cesspool to be replaced within a set period after the property is sold, and earlier near shorelines and drinking-water sources; Hawaii has set a statewide deadline to convert every cesspool. Many other states have no requirement at sale and leave cesspools to county health departments when they fail. This is not legal advice; the county health department or state environmental agency answers what applies to a given lot, and the owner's attorney answers what a sale requires.

For a field shop, the law matters in one practical way: an owner with a cesspool may be facing a mandatory upgrade, and the yard you are about to fence, pave or plant may be where the replacement system has to go.

Worked example: a fence line across a sunken circle

A fence crew is setting an 80-foot run of fence along the side yard of a 1938 lakeside cottage, posts every 8 feet. Eighty feet at 8-foot spacing is 10 bays and 11 posts, at 0, 8, 16, 24, 32, 40, 48, 56, 64, 72 and 80 feet.

Walking the line before the auger rig comes off the trailer, the lead finds a round depression about 6 feet across, centered about 28 feet along the line, with greener grass on it and a 4-inch cast-iron pipe stub at grade near the house end. There is no septic lid, riser or drain field anywhere on the lot.

The read. A sunken circle, a green cap, a cast-iron line heading toward it and no visible septic system on a 1938 lot add up to "appears to be a cesspool or old pit." Nothing on the surface tells him whether it is in use, abandoned, or already caving.

The hold. The shop default is no digging and no equipment within 10 feet of the edge of an unexplained depression. The depression runs from 25 to 31 feet along the line (28 minus 3, 28 plus 3), so the hold runs from 15 to 41 feet (25 minus 10, 31 plus 10). The posts at 16, 24, 32 and 40 feet are inside it, four of the eleven. The auger rig's planned path along the line runs straight across the depression, so the path is rerouted to come in from the far end and stop short of 41 feet.

What he does. He marks the circle and the 10-foot margin with stakes and tape. He sets the seven posts outside the hold (0, 8, 48, 56, 64, 72, 80) only if the owner agrees to proceed in stages, and otherwise holds the whole job. He tells the owner what he saw and recommends a septic contractor locate and assess the pit, and he records it: "Depression about 6 ft diameter at 28 ft along fence line, green cap, 4-in cast-iron stub toward it, no visible septic system; suspected cesspool; not probed; 10-ft hold marked."

What changes the answer:

• The septic contractor finds an active cesspool. The fence may be fine beside it, but the owner should know that a lakeside lot is exactly where state rules tend to be strictest, and that a replacement system may need this side yard. Fencing across it can mean pulling the fence later, which the owner decides with that information.
• The pit was properly abandoned (pumped, the cover broken in and the void filled, with a record): the hold comes off and the four posts go in.
• It turns out to be a settled tree-stump hole or an old filled trench. The hold cost a day. The other outcome costs a machine in a pit, or worse.

How to verify you handled it right

• Nobody and nothing crossed the depression, including during setup and cleanup, when crews take shortcuts.
• The hold has a number and is marked on the ground, not only in the notes.
• The record says "appears to be" and gives the location in measurements someone else can find.
• The owner has the septic contractor's name, and the ticket says what is waiting on that visit.

References

• See related: Recognize, Record, Route - the Rule for Legacy Materials; Septic System Basics; Private Wells and Septic for Non-Specialists; Old Wells and Abandoned Casings
• EPA, Underground Injection Control, Class V large-capacity cesspool rules, 40 CFR Part 144
• OSHA, Permit-Required Confined Spaces, 29 CFR 1910.146 and 29 CFR 1926 Subpart AA
• Your state environmental agency and county health department, on-site wastewater and cesspool rules