ORIGINALLY WRITTEN FREE PRESS STAFF
Wash an apple under the sink faucet, drain the bath water, flush a toilet-what happens to the wastewater that magically disappears down the drain?
For rural Marion County residents, the answer is that the water goes into a wastewater lagoon or a traditional septic tank/lateral field.
Those are the two most common systems installed on new rural-home properties or used to replace outdated systems found connected to older homes in the county.
“In the unincorporated areas, I usually recommend the wastewater lagoon over the traditional septic tank/lateral field,” said David Brazil, Marion County planning and zoning director, and public-health sanitarian. “It’s half the cost and has twice the longevity.”
But Brazil said the soil also determines the type and size of wastewater system he recommends.
The higher the clay content in the soil, the more difficult it becomes to put in the traditional septic/tank lateral, he said.
“If the clay content gets too high-upward of 40 to 50 percent-we basically can’t put in a traditional septic tank/lateral field.”
“It’s like putting a bathtub in underground, and once the bathtub’s full, the system is done-you can’t go any further. We tell (homeowners) they need to go to an alternative system or a wastewater lagoon.”
Brazil estimated that only one in 10 wastewater systems used in new rural homes are septic tank/lateral fields.
“But a lot of homeowners 20 years ago weren’t putting in wastewater lagoons,” he said. “So a majority of the older systems are septic tank/lateral fields.”
The traditional septic-tank system in Marion County consists of two components-the tank and an absorption field, which Brazil calls the lateral field. The lateral field is an underground trench system designed to accept the water from the septic tank.
Home wastewater flows into an underground water-tight tank commonly constructed of concrete, heavy-duty fiberglass or plastic.
The tank should be located at least 15 feet from foundation walls and 50 feet from private water supplies or surface waters.
Solids are separated from the liquid and stored as sludge at the bottom of the tank. Lighter material, such as oil and grease, rises to the top and is called “scum.”
As the wastewater flows through the tank between the sludge and scum layers, solids separate and the wastewater becomes almost clear.
Biological action, known as anaerobic digestion, actually decomposes some of the solids into simpler compounds such as water and gasses.
The liquid-called septic-tank effluent-flows through a pipe into the lateral field. From there, it percolates-moves out-into the soil.
“In Marion County, with an average-size house with average soil, you’re probably looking at a 1,000-gallon septic tank and 300 to 400 linear feet of laterals,” Brazil said.
Every three to four years, all the material in the septic tank should be pumped out by a contractor who uses a “honey wagon,” he said.
The typical lateral field consists of two or more flat-bottom trenches 3-feet deep, 3-feet wide and 100-feet long.
“You put down rock, lay the pipe on top of it, cover the rock over the pipe and add a little bit of top soil,” Brazil said.
In the past 15 years, a second type of lateral-field conduit-called the chamber system-has been available for use.
The crescent-shaped chamber, which replaces the traditional pipe, is 6 feet 3 inches long and 3 feet wide, has vents and is open along the bottom.
“You just lay that in your 3-foot-deep trench, and cover that up with a foot to foot and a half of soil,” Brazil said.
“The advantages of the chamber are it has a much greater storage capacity for the wastewater, and it allows more surface contact between the soil and the wastewater.”
The cost of both conduit systems is about the same, but Brazil said the chamber system is 15 percent more effective.
The total cost of a new septic tank/lateral field is about $3,500 to $4,500.
“That’s an average sized system, not a large system,” Brazil said.
The lateral field should last at least 15 years, but Brazil said some have been know to operate effectively for 30 years.
If the tank is pumped on the recommended schedule, the lateral field lasts longer, he said.
Lateral fields usually fail for one of two reasons: (1) solids from the septic tank enter the lateral field, build up a bio field called slime and prevent the water from percolating out; or (2) there’s an open line at the end of the lateral field.
Brazil has a list available of contractors who install both septic tank/lateral fields and wastewater lagoons.
“I have a bias, and I’m up front about that,” Brazil said. “I think if you have the space, the wastewater lagoon is the wiser choice.”
It works well on larger lot-size properties that have high-clay soil, he said. The increased clay content creates slow percolation rates.
“I think the general public sees the lagoon as a hole in the ground,” Brazil said. “But it’s designed to get wastewater from the house and utilize evaporation by using several biological processes.”
The bottom of the lagoon is anaerobic, which means it has oxygen-depleted bacteria like a septic tank.
Half-way up, the water turns aerobic-with aerobic bacteria working to break down the wastewater.
“The top 6 inches is actually sterilized by the ultraviolet light from the sun,” Brazil said. “So you’ve got a clean-water cap over the septic water at the bottom.”
The water evaporates off the surface of the lagoon, and some of the wastes from the house have been refined enough by the bacteria that they evaporate with the water molecules.
The pipe from the house extends about 11/2 feet from the bottom of the lagoon, which is dug with sloped sides to create more surface water than bottom water.
Brazil recommends a 3-to-1 slope-for every 3 feet dug out, go 1 foot up. The area should be dug down 5 feet, and there should be 2 feet of berm on the ground if it’s sitting on a level site.
The surface area of a lagoon should be at least 900 square feet. When more than five people live in a home, an additional 175 square feet of lagoon surface area is required per person.
The length of the lagoon shouldn’t exceed three times its width, and the depth of the water should be maintained at about 3 feet.
The lagoon should be located at least 50 feet from property lines and 200 feet from neighboring residences. The minimum-size lot for lagoon construction is three acres.
Brazil said a recent Kansas State University study indicates that the average cost of a lagoon project in this part of the state is between $1,500 and $2,500.
“There’s lots of variables there,” he added. “Having a rock layer can make that cost go up, having tighter clay soils can make the cost go up, the distance that a contractor has to travel can make cost go up, and materials used can make the cost go up.”
The recommended size of each homeowner’s lagoon is often a balance between the number of bedrooms and the number of occupants in a home.
Brazil said he’ll often recommend an intermediate-size lagoon for a large home with fewer occupants.
Once or twice a year, that homeowner may need to run water in it to maintain the 3-foot water level.
To keep domestic animals and children out of lagoons, homeowners must have a fence that is a minimum 4-feet tall and should install at least a 4-foot hanging gate.
The fence choices recommended are chain-link or 2-inch by 4-inch welded wire, but Brazil said horse paneling is a third option.
To operate successfully, a lagoon needs sun, wind and water.
“When a lagoon is working properly, it will be sparkling green,” Brazil said. “The top 6 to 8 inches will be relatively clear on a calm day, and then underneath that you’ll see three to four different green tones like the grass in your front yard.”
He recommends mowing three to four times a season and removing any trees or bushes around the edges.
If weeds grow too tall, they block the wind from moving across the surface of the water and prevent the natural process of evaporation required to keep the lagoon efficient and effective.
Properly maintained lagoons should not have an odor problem except for two times a year-once in the spring and once in the fall, Brazil said.
In the fall, the water on top gets cold and sinks to the bottom at the same time as the warmer water on the bottom comes to the surface.
“It takes a good day of solid sunlight for the lagoon to balance itself out during that day,” Brazil said. “You’ll have an odor that you could probably detect 40 feet away from the lagoon.”
In the spring, the process reverses itself, and the odor can be detected again.
A lagoon installed in a high-clay-content soil usually doesn’t percolate too much water into the ground and won’t require any sealant like bentonite.
If a loamy soil or mixed structure like fractured rock is at the site of a new lagoon, Brazil said he recommends bringing in about 1 foot of “good” clay top soil and then adding a layer of bentonite clay.
The cost to install a wastewater lagoon is about $1,800 to $2,000, and the average life span is 30 years, Brazil said.
“They’re really efficient, and they’re designed to work with Mother Nature.”