The Soil Tells The Story 03-27-09

03-27-09
The Soil Tells The Story

It was twenty-five years ago this April of 2009, that I witnessed my first perc test. I wasn’t an official witness. Heck, I didn’t even know what the word meant; I certainly could not have interpreted the results. I was interested in it, though. I remember watching a big hole dug by an excavator and seeing a lot of sand. I asked if the orange-colored soils under the brown topsoil were clay. This question was greeted with chuckles and I was immediately set straight that there was no clay on this property. I watched as a shelf was made with a small hole dug into the collapsing sand. Water was poured into it and everyone watched as the water quickly disappeared. I wasn’t sure what this all meant but everyone seemed happy with the results and this happy occasion would somehow form the basis for designing the septic system for the new, not-yet-built house. I looked around with delight and, being a country girl at heart, I couldn’t wait to move to this pine tree hill in this beautiful little town.
Although first interested in the property in the fall of 1984, we had to wait about six months to conduct that almighty perc test because Plympton only conducted perc tests in the spring. Oh, well, I figured, what can you do with these municipal rules other than accept them?
Looking back on those perc test conversations, I can appreciate the wisdom behind those rules. The 1984 Plympton Board of Health knew that the septic system leaching areas should not sit in the groundwater. At the same time, boards of health were learning that cesspools worked in that the contents went up and down. It acted like a large outdoor in-ground toilet. The cylindrical hole in the earth filled up with whatever was delivered by the plumbing. Groundwater came along, blended with the contents of the cesspool and then, in drier times, receded, emptying, or flushing, the cesspool. Marvelous, amazing things, those cesspools. They last forever. Too bad that they get such a bad rap, though, huh? They “only” pollute the groundwater, contaminating it with bacteria and viruses of all kinds. And, in rural areas, such as sweet Plympton, that can mean contaminated drinking water, as well.
So, in 1984, the trend was to design more shallow cesspools, called pits or chambers, and to keep the bottom of them above and out of the groundwater. I was fortunate. My property did not have a groundwater issue. Not then or now.
It is important to look at both then and now, because knowledge grows and, with that knowledge, the rules and responsibilities change. Plympton did the best it could in 1984 and they did the wise thing, too. Preferring to err on the side of caution, they waited until what is the traditionally wettest time of the year to conduct that perc test. It would be another decade before the next big wave of scientific evidence swelled to such a degree that the rules had to be changed once again. Many still recall with anger when, what is known in Massachusetts as “Title V”, changed dramatically. Local boards of health may make reasonable regulations stricter than the State’s but never more lenient. So, it was with a rush to beat the fast approaching changes, that some septic systems were designed in the spring and summer of 1995 with what would soon be seen as more lenient rules. If your system dates from that time period and it is still functioning, you might want to call it a skeptic system and go to your local board of health for more information.
For instance, if water was seen in the deep hole in the spring, that would be measured and that measurement would count as the official elevation of the groundwater. What if that year happened to be a drought year, though? In an ongoing dry period, a system’s leaching area could easily end up in the groundwater when more rain returned. That is exactly what the new rules, based on new scientific evidence, wanted to avoid. The goal was the same. The means of determination had changed.
By listening to soil scientists, the state’s environmental watchdogs realized that there were methods of determining the seasonal high groundwater, even during the driest part of the year and even in a whole year of drought. The soil scientists knew that as the groundwater rose, it changed the chemistry surrounding the soil particles. There would be times when the particles were submerged and other times and places where the water could not sit long enough to create chemical changes around those soil particles. When water had the opportunity to sit for a while, it stripped the iron so common in New England soils, leaving some areas with concentrations of reddish colors from the iron and other areas depleted of iron, stripped down to their natural yellowish grey bits of granite. Scientists call these marks redoximorphic features. Common lingo refers to them as mottles.
Now, when a percolation test is performed, it is with confidence that we determine the seasonal high groundwater because we look carefully for the redoximorphic features. In an ever-morphing world, it is comforting to feel sure about something.

Cathleen Drinan is the health agent for the Town of Halifax. You can contact her with questions about septic systems and groundwater at 781 293 6768 or cdrinan@town.halifax.ma.us