Best Management Practices Series:
A New House Goes Up:
Back when Steve Privette of Willow Springs was a kid, his neighbor's sewer system plugged up. He remembers that somebody dug up the line and unclogged it with a snake tool. Money was tight in those days and the system was not repaired properly, so after that, water from that septic tank would surface and run into his yard. It would stink, and I didn't like mowing in that area, because it was always mushy, Mr. Privette recalls. But the prettiest tomatoes grew there, even though no one ever planted any seeds. But Dad would never let us eat them.
The seeds came from tomatoes that had been eaten and passed through the septic system. The fruits were well-watered and well-fertilized, also by the septic system. His Dad was right to not eat them; plants fertilized by human waste might contain bacteria that could make people sick.
Mr. Privette grew up in rural Howell County, Missouri, outside of city limits. In that area, everyone who lives in the country is responsible for the water that goes down their drains, with no help from the city or any other government. Most rural residents in the watersheds of south central Missouri and northern Arkansas use septic systems to treat their wastewater. But there are no laws requiring a sewer system. If a homeowner doesn't have the money to install or repair a septic tank, lagoon, or other system, some of them just let the waste flow out onto the ground.
Mowing around those tomatoes was Mr. Privette's first experience with a failed septic system. But he became a lawyer after he grew up, and he has seen a number of court cases in which someone sued someone else because sewage backed up and flooded a basement. You do not want that. There's nothing you can do to wash out the smell or get rid of the mold. The house is never the same, he said.
Septic System Failure Is Common in Southern Missouri Watersheds
There is another possible problem with septic systems, and it's a big one. The geology in south central Missouri is known as karst, which means there are thick layers of porous limestone rock under the ground, with not much soil on top. In this karst landscape, the most likely thing to happen when a septic system fails is that the polluted water will flow straight down through the rocks and quickly end up in the groundwater. Since most rural residents get their household water from wells, and since those wells are often located very close to septic tanks, that means those people could be drinking recycled toilet water.
This really does happen. A 2005 study by the Howell County Health Department discovered that water in 42 percent of the wells in that county were contaminated with fecal bacteria. That kind of bacteria can only come from the insides of a living creature, so its source might be livestock manure, wildlife droppings, or human waste. The chairman of the health department said, We think the majority of bad wells are being polluted from their own septic systems.
See related story: Health Dept. Gets Positive Feedback on Proposed Sewer Ordinance. Read more about the 2005 well water study in the Health Department's May 2006 news release (PDF).
Mr. Privette Builds A New House
Returning to Steve Privette's story, in 2006 he decided to build a new house. It is located north of Willow Springs, in a rural area at the headwaters of the Eleven Point River watershed [map].
Mr. Privette had learned from his experiences. He definitely did not want to mow around mush, have sewage back up into his basement, or drink well water that had started out in his toilet. Even though no law required him to put in any particular system (or any system at all), he wanted to do the right thing. To make sure the job was done correctly, he hired Tony Summers with All Pumps and Septic, Willow Springs, because Mr. Summers is a trained and licensed septic system installer.
How A Septic System Works
Mr. Summers explained the parts of a septic system. A pipe carrying wastewater runs from the house into a big buried tank, called a septic tank. These tanks are made of fiberglass, concrete, or steel. Most installers do not put in steel tanks any more because they rot out and leak, but many older homes have steel tanks.
Septic means to make putrid (become rotten and stinky). As wastewater sits in a septic tank, the solids settle down to the bottom of the tank, and grease and other scummy substances float to the top. Bacteria inside the tank get to work, decomposing the scum and solids to make them septic. About 95 percent of the solids are turned to liquid by the bacteria, said Mr. Summers. A second pipe, on the other end of the tank, allows water to exit. A baffle, or small barrier, keeps the scum and solids from passing out of the tank with the water.
After leaving the septic tank, the wastewater flows into one of several lateral lines, which are located in a big area called a drainfield. The lateral lines which Mr. Summers installs are made of open-bottomed plastic tubes with lots of holes. These are laid down inside long, level trenches, then covered with soil. Because the lateral lines are level, the water spreads throughout them and seeps out evenly. This distributes the wastewater throughout the entire drainfield, where it is absorbed into the ground. If the trenches are not level, the water will all run downhill to the lowest spot, which can cause the system to fail.
Once the water has passed out of the pipes and into the surrounding soil, anything that might still be suspended in the wastewater should be further decomposed by bacteria in the soil. The soil also is expected to act as a filter, purifying the wastewater as it slowly seeps deeper into the groundwater.
Designing A Septic System For Mr. Privette
After arriving at the construction site for Mr. Privette's new house, Mr. Summers first looked for the best spot in the yard to install the septic system. He made sure the location was downhill from the house, was not near the well, and was not close to anything else that might cause a problem later. Then he examined the soil in the chosen area. A system that works well in deep, loamy soil might not drain properly in heavy clay, or might drain too quickly in very rocky soil. A septic system must be designed to fit the soil type. In some situations, a soil scientist is hired to do a precise soil analysis.
Next, Mr. Summers looked at the house size and the number of bedrooms. He needed to know this so he could design the system to safely dispose of wastewater for the most number of people who might live there in the future, not just the number in Mr. Privette's family right now.
Based on all this information, Mr. Summers recommended a 1500 gallon concrete septic tank, with 500 running feet of lateral line. This is a large system, because the house is very large. I could make the system a lot smaller and not be breaking the law, and nobody would say a word, Mr. Summers said. But if he (Mr. Privette) sold the house to a family with six kids, then the smaller system wouldn't be big enough. The smallest system that Mr. Summers will put in is a 1000 gallon septic tank and 200 running feet of lateral line, even if it's a one-bedroom trailer house, he said.
Installing The Septic System
On a hot August day, Mr. Summers sent backhoe operator Carl Roberts to start digging a trench from the new house out into the yard. The house was still under construction. When the trench was done, Mr. Roberts cut white plastic pipe and hooked it up to the drain coming out of the new house. He ran pipe all the way down the trench, glued it together, then refilled the trench, covering the pipe with soil.
Photos and text by Denise Henderson Vaughn.
The development of content for the *Best Management Practices Series* is funded in part by the U.S. Environmental Protection Agency Region 7, through the Missouri Department of Natural Resources, under Section 319 of the Clean Water Act. DNR Subgrant #G04-NPS-17.