Will Your Soils Want Your Septic System?
“Don’t put that stuff here!” and “Not in my backyard!“ There are lots of ways of saying it, and sometimes it’s the ground that does the talking.
If you have a rural property, you likely won’t have access to a publicly owned sewer system. Instead, you will have to test your soils and install a septic system. Sometimes that is relatively easy and others it is downright difficult. Much will depend on the soils you have under the surface of your land. Below is a basic description for what you’ll need to endure to discover what type of a septic system you’ll need. Keep in mind that every situation is unique. Let’s walk through the process and then see what you can do if things don’t go as planned.
Step 1: Site Evaluation.
Start with a good pair of walking shoes and a map of your land drawn to scale. You can find maps at the local county offices or potentially online. Just make sure the scale is something you can work with in the field. It is likely your only measuring tool in the field will be a tape measure so increments of 1/16″ to 1″ per foot work well depending on the size of your land and how much paper you want to carry around with you. Of course if you have a particular section of your land in mind for the septic system, you don’t have to carry a map with you that covers the other 150,000 acres (I’m of course assuming that Ted Turner is one of my clients here!). The local county office or sanitation department will usually have informational packets that explain the process and clearly outline what you’ll need to note on the map.
Don’t clear your land before you complete the site evaluation. You’ll want to look for patterns in the trees, grasses and rock outcroppings that would otherwise be lost if the land is cleared prematurely. In addition, if a well is needed on site, you should consider locating the septic system first and then locating the well. In some cases, the obvious location of water will help in this process, but in most cases, you’ll need to hire a professional to locate your best location for a well.
Step 2: Make Your Map.
Now that you have walked the land and are clear about where you want to build your house and install your septic, start making your map. You should include the location of all test pits on the map as the sanitation will want to see their location as well as the data they yield about the soils on your land. The actual digging of the test pits can often be done by the home owner, but the system design is best left to licensed septic designers. Check with your local sanitation department. Just like on a plot plan, you will need to include things like property lines, grade changes, water ways, existing structures, roads, and more. Check with your sanitation department documents to see what is required.
Step 3: Dig the Test Pits.
Unlike the old days where small “perc-tests” were performed by drilling a relatively shallow hole in the soil and dumping 5 gallons of water into it, most jurisdictions require test pits be dug from 5′ to 7′ deep by a backhoe. The pits allow for a greater viewing of the soil layering and are much more telling about what is really happening underground. The pits must be dug wide enough to allow access to the base without a danger of cave-in and must be sloped to allow for a soil analyst to walk into the pit and test the soils at depth.
Step 4: Design the System.
The moment of truth has arrived. What kind of soils do you have and will they accept your septic system? Once your soil analysis is complete, your designer will use the local sanitation department guidelines to determine what type of system you will need. The soils around 3′ to 4′ down are the most important as they are at roughly the same level as the drainfield will be once the system is installed and will be responsible for cleaning the effluent (liquids from the septic tank). Once again, the septic designer will take over for this portion of the job. He or she will design your septic system based on the soil analysis they perform in the test holes. Like I said, some soils are easier than others. The process can be quick: 20 minutes per hole (dig, analyze, fill), or long: up to an hour per hole in difficult sites. Plan some time for this process.
There are several types of systems. Even within the heading “standard septic system” there can be great variation. Some drainfields are required to be bigger than others based on soil types and home size so that the slower draining soils have time to catch up. This is where your soils report can catch you off guard. Tight soils can mean a larger system may be needed or even a special system like a sand filter. Just remember that something will work, so don’t panic. The biggest bummer is that the “something” may cost you twice as much as a standard system.
Consider adding size to your system if the soils don’t test well. Another option is to use drainfield plastic vaults. They are connected to each other and improve the efficiency of the system. Sometimes a simple system redesign is the cheapest thing to do and the best all around option. When that will not work, consider switching to a two vault system or a sand filter. Each of these has their place and your designer will be able to tell you what your land requires. Be sure you get the soil analysis right because a mistake there can leave you with too small a system which will fail early or too big of a system that unnecessarily sucks money out of your wallet at a rapid pace.
Designing the right system starts with a good soli analysis and ends with a conservative design that considers long term expansion of the family and/or home. Be sure to consider efficiency and cost together when you decide on your system. There are two costs to consider. The first is the installation cost. The second is the lifecycle cost. This is the long term cost of the system. For me, having a system that can expand with the growth of my family is a cost worth incorporating in the system design. Remember, there is always a way to make it work. Your job is to find the best one for you at the least cost without compromising the quality and long term efficiency.
ABOUT THE AUTHOR
Andrew Morrison is the co-founder of Straw Bale Innovations, LLC, a company specializing in straw bale construction education and the proprietor of www.StrawBale.com. Andrew has a passion for straw bale construction that is matched only by his desire to teach his knowledge to others. For over 15 years, Andrew was a skilled, licensed general contractor with experience in designing and building both conventional and straw bale homes. In 2007 Andrew closed his contracting company to focus entirely on teaching workshops and consulting. You can learn more about his workshops at www.StrawBaleWorkshops.com and his consulting services at www.StrawBaleConsulting.com. Andrew received a BA degree from Hampshire College in 1995 for Glacial Geology. He also has a degree in construction technology form the College of the Redwoods.
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