Occasionally someone asks how well a drainfield works and if one's willing to accept a great deal of uncertainty and qualifications, we can answer the question. Some of our information comes from laboratory studies, some from research that Virginia Tech has done for us using columns installed under close to natural conditions, and some of it comes from testing real working systems. The latter usually gets a raised eyebrow and sometimes the question, "How do you measure a working system?" The answer is, with difficulty and using several different techniques depending on what we're looking to discover.
One of the common tools used is a lysimeter. There are several varieties including suction lysimeters and pan lysimeters. A lysimeter is just a device for collecting a "water" sample from the soil.
Lysimeters then are what we use to collect samples from under a drainfield. They can be placed very precisely so we can sample a known distance below or beside a drainfield. The devices have to be inert so the sample results are meaningful and they have to be capable of being sterilized before use. They come in a variety of sizes shapes and materials. The one in the following photos is made of stainless steel but others lysimeters are made of plastic or ceramic materials.
These photos show Kevin Sherman, Ph.D., installing ground water sampling devices called suction lysimeters. This particular lysimeter is designed to allow the collection of water samples from the vadose (unsaturated) zone for biological analysis. These photos were taken in the Florida Keys at a site where research is being conducted on a sewage system serving a daycare facility. Movement of bacteria is important in the coarse marine sediments and fill over coral but nutrients are an even greater concern. Evidence suggests that nitrogen from onsite systems is adversely impacting the marine environment around the Florida Keys.
These photos also suggest that the dress code in the Keys is a bit more relaxed that in Virginia. Our actual observation was everything in the Keys was more relaxed. Dr. Sherman is the president of the National Onsite Wastewater Association and we'd like to point out he does clean up nicely. Two days after this photo was take he was in a business suit he was enjoying 18 degree weather in Milwaukee at the 1996 annual NOWRA conference.
Finally, here's the final installation before it was covered with soil.