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It’s a no-brainer that acing a physics exam won’t affect one’s grade in history class, yet it’s frequent to assume that a water test, not otherwise specified, covers all the potential bases. A common water test is for coliform bacteria, the presence of which would indicate a leaking septic field, or/ and manure runoff. If the lab gets back to you with a result of ND or “non-detect,” it’s great news, but it is by no means a clean bill of health.
Wells, no matter how deep, are vulnerable to contaminants that originate on the surface. Pesticide residues, nitrates from commercial fertilizers, benzene and other dissolved-phase petroleum compounds, and commercial degreasers are but a few of the things that can end up spewing from our faucets.
Across northern NY State, around 40% of residents rely on wells for drinking water. We are very fortunate in our little corner of the planet to have such easy access to fresh water. Broadly speaking, aquifers in our region are shallow, with the water table less than 50 feet below ground. In fact, dug wells still exist at some rural homes.
By contrast, it’s often necessary to drill 300 feet or deeper to find water in parts of the Southwest and Midwest. Another blessing is that our aquifers are replenished annually. In some Midwestern states, aquifers are being depleted faster than they can recharge, and it’s not uncommon for wells to run dry and need replacement or overdrilling to deepen them.
While no well is pollution-proof, a dug well is at higher risk for contamination. A drilled well is more secure, but regardless of depth, it’s still vulnerable to surface pollutants near the wellhead. There’s no such thing as a well in “solid rock,” which by definition is a dry hole in the ground. Water flows into boreholes at various depths through bedding planes in sedimentary formations, and joints and fissures in all rock types. Contaminants are sometimes drawn into wells along these channels.
There are three general categories of water-quality measurements: biological, inorganic, and organic. A typical biological marker for potential water-borne pathogens is the presence of coliform bacteria. Some coliforms are harmless, occurring naturally in soil, but fecal coliform bacteria live only in the digestive tracts of warm-blooded animals. Their presence indicates pollution from septic systems or animal manure.
Contaminants such as lead, arsenic, cadmium, and copper are called inorganic. So are nitrates, which can sicken or kill infants, as well as indicating that pesticides could be getting into the water. Many older pesticides contained lead and arsenic, which do not break down, and some farms still have high levels of these metals in the soil. Cadmium and chromium, released from smelting operations and when colored paper is burned, can leach into the groundwater too.
Hardness (from calcium and magnesium), as well as iron, chloride and sulfur are natural inorganics that can leave deposits and stains, or cause a bad smell or taste. At very high levels, some of these elements can be toxic.
“Organic” is a misleading term, because while organic food is good, consuming organic chemicals is definitely not. Pesticides, degreasers, gas, oil, antifreeze, and many paints are all organic chemicals. How do these get into our water? It’s shockingly easy to pollute groundwater here in the Northeast where it rains a lot and the distance to groundwater is relatively small. Leaky fuel tanks, tank overfills, garage floor drains, and even surface spills can contaminate wells.
We’re told oil and water don’t mix, but that’s a partial truth: they don’t mix much, but enough to badly pollute water. Benzene, a constituent of gas and diesel, is 0.018% water soluble. Given that the allowable limit of benzene in drinking water is 0.07 parts per billion (ppb), the concentration of benzene near a gas spill could be something like 180,000 ppb! Fortunately, the odor threshold for benzene is 50-100 ppb, so one would never drink benzene at that concentration.
Paint thinners and degreasers that get washed down home drains easily enter groundwater through septic fields and find their way into kitchen sinks. Many chlorinated solvents like dry-cleaning fluids have high odor thresholds, meaning one could drink high levels over time without knowing it. Fuel oil spilled in a garden could disappear in one season if one added manure and rototilled often, but underground with little oxygen, chemicals take decades, even generations, to break down.
Because groundwater is always (slowly, in general) flowing, contamination often takes months or years to show up. A corollary to that is the fact that contamination from one property can and does migrate onto others’ properties.
Testing for organics is complicated: for example, checking for solvents, pesticides, and antifreeze all require different tests. It can also be expensive. The cost of testing for oil and most solvents varies, but may be in the $50-$60 range. For pesticides, though, it can run many times that amount.
Many contaminants can be removed with the right filtration system, but upkeep is expensive. Occasionally, drilling a new well upgradient from the contaminated area is more cost-effective, and safer, than perpetual filtration.
The take-home message is that anything that goes onto the ground or down the drain can into our drinking water. National Groundwater Awareness Week is March 7-13, 2021, and World Water Day is March 22. Let’s work together to keep our well water – and that of our neighbors – well.
A former Cornell Extension educator, Paul Hetzler’s well is drilled in coarse-grained igneous rock. He takes clean water from granite, but never for granted.
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Paul,
Nice article.
I would like to expand on it. The part where you discuss benzene being slightly soluble in water. After tetra ethyl lead was banned as an gasoline octane booster in the 70’s because of it’s toxicity, they started using MTBE or Methyl tert-butyl ether as an octane booster. MTBE has a greater solubility in water than benzene.
Around underground gasoline storage tanks that leaked gasoline containing MTBE, home owners wells could become contaminated with MTBE, but not benzene or other components of gasoline such as toluene, ethyl benzene and xylenes.
This was due to the much higher solubility of MTBE in water so it would travel further in the aquifer. As a result of this, The DEC had to put in water filtration systems in peoples homes. MTBE has since been banned and now we have ethanol to replace it.
Agreed, well-written article.
JT, I’m no expert in gasoline additives, but I think you are mostly right about the inefficiency of aromatic hydrocarbons in migrating to groundwater through soil, and sometime ago I actually saw a study where they injected dichlorobenzene, which has a similar solubility in water as benzene but is found more commonly in household products (e.g., drain cleaners), directly into a septic system and then dug test pits and analyzed concentrations at various depths over about 10 weeks. They found that DCB was highly attenuated (i.e., concentration was not conserved and went down rapidly over time), with an estimated half-life of 15 days and a high retardation factor (it still travelled through unsaturated sandy ground through sorption, but much more slowly than water). They theorized that in an aerobic environment, DCB may be mainly degraded via bacterial metabolism, warning that in an area with a high water table or different soil characteristics, DCB could easily reach the anaerobic water table where it would remain without biodegradation (they even cited an Air Force base in Massachusetts where DCB ground contamination has persisted for decades and migrated miles). (That study, by the way: Robertson, W. D. (1994). Chemical fate and transport in a domestic septic system: Site description and attenuation of dichlorobenzene. Environmental Toxicology and Chemistry: An International Journal, 13(2), 183-191.)
I do know that there are all sorts of proprietary additives in gasoline other than the mostly phased-out MTBE (anti-oxidants, ignition controllers, corrosion inhibitors, markers, dyes, etc.), and some of them may be more soluble in water. The additive tricresyl phosphate comes to mind as being particularly toxic, but beware I am really not sure if that is used in gasoline or automotive motor oil. We would probably need an industry insider to tell us more about all of that.
Lastly, for those interested, I will copy-paste an excerpt from an excellent earlier comment from my good friend and colleague Henry Grant on the very important subject of the prevalence of PPCPs (pharmaceuticals and personal care products) in septic systems and, subsequently, in groundwater:
Our modern wastewater treatment technologies are little changed from the 1960s, and they are really only equipped to handle BOD (biological oxygen demand), fecal pathogens and some very basic other challenges. In the past fifty or so years, though, thousands of new compounds have come into widespread and increasing use by consumers, in the form of pharmaceuticals and personal care products (PPCPs) and other household products. Unfortunately, these facts, and their inevitable consequence for xenobiotic contamination of the environment, remain fairly uncontemplated by the general public, instead being mainly confined to the purview of a handful of experts. We can see that governments in the United States are well aware of this issue if we look at some of their reports.
The vast majority of research, especially pertaining to OSWTS, however, is still focused on contamination in groundwater from fecal pathogens or nitrogen and phosphorus contamination, rather than PPCPs and related organic compounds. That research does indicate that those contaminants, which are heavily monitored, are finding their way into ground and surface water as a constituent of effluent from functioning OSWTS (Hantzsche and Finnemore [1992], Robertson et al [1991], Tinker [1991], Verhougstraete [2015], Walker et al [1973]). The organic compounds in PPCPs, which are present in virtually all WWTPs and OSWTS, are certainly also making their way into ground and surface water via discharge of treated effluent, especially since they are much harder to remove from wastewater due to their highly polar nature (water-solubility). This property is also what makes these compounds particularly hard to detect in the environment (Ternes et al [2004]) despite the fact that they have a very high potential for human and environmental toxic impact. That being said, there is still plenty of research confirming their presence in treated effluent and their subsequent occurrence in ground and surface water worldwide (Cormio [2008], Daughton and Ternes [1999], Ebele et al [2017], Halling-Sørensen et al [1998], Herberer [2002], Kolpin et al [2002], Kolpin et al [2004], Loraine and Pettigrove [2006], Luckenbach and Epel [2005], Montes-Grajales et al [2017], Nowak and Lisowska [2020], Del Rosario et al [2014], Stuer-Lauridsen [2000], etc). Further complicating things is the fact that some of the organic compounds that have been found in treated wastewater effluent are also used in house and boat paints, cleaning products, sunscreens, etc, which could provide additional sources of ground and surface water contamination. An example would be high concentrations of methylisothiazolinone (MIT), which is found in sunscreens, in beach sand. On the other hand, MIT and related compounds are also found ubiquitously in rinse-off products that ultimately make their way into wastewater effluent. The reason that these compounds are so widely used is due to their desirable antimicrobial activities, and they have been argued to be safer alternatives to other biocides due to their perceived low toxicity and low environmental stability. However, emerging research is calling this into question by demonstrating adverse health effects in mammals and aquatic life (neurotoxicity, cytotoxicity) and high prevalence in the environment (Silva et al [2020], Nowak and Lisowska [2020]).
More research needs to be done, especially here in the United States, where we are 20 years behind Europe in this area, and even more so in the Adirondacks. But we already have plenty of data and good models, which indicate that the assumption that OSWTS are preventing these compounds from reaching ground and surface water is simply false. Centralized WWTPs are better, but still do not remove enough of these organic contaminants to render most effluent environmentally safe. If anything, though, we can be thankful for the fact the WWTPs reduce the number point sources of contamination and tend to be built intentionally distant from nearby drinking water sources, which is a still great improvement over OSWTS. Many places in the Adirondacks and Catskills are particularly poorly suited to the use of OSWTS due to suboptimal soils. In some such places, certain solutes can quickly travel through soils, hundreds of feet beyond NYSDOH and APA setback requirements from wells and surface water, without diminishing significantly in concentration (Robertson et al [1991], Weiskel and Howes [1992], etc). Thus, the argument for limiting the density of houses in unsewered Adirondack areas is backed by an abundance of literature, with the EPA even suggesting that density greater than 40 OSWTS per square mile has the potential to adversely impact groundwater (Carroll and Goonetilleke [2005], Whitehead and Geary [2003], Yates [1985], etc). Obviously, even basic safety criteria are probably not being met in most places in upstate NY. We need to take a hard look at current practices and not assume that wastewater technologies give us the green-light to settle rural areas in greater and greater numbers without environmental and health consequences.
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Informative reply. Emerging contaminants–pharmaceuticals, personal care products (PCPs) and endocrine disrupting compounds (EDCs)-that we wash down our waste systems (home septic units and municipal waste treatment plants) should also be mentioned. In Ithaca, a study of emerging contaminants found that these contaminants are ending up in Cayuga Lake and that most of these contaminants just pass through the municipal waste treatment plant (WWTP) and are then discharged into the lake. I’m not aware of similar studies in the Adirondacks.
Thanks, sounds like a very interesting study from Cayuga Lake; I had not heard of that one, or any other serious PPCP-related study in NYS. But I have long believed that emerging high-polarity organic pollutants are the most dangerous for environmental and human health! In the original comment from Henry Grant that I excerpted, he had mentioned the fecal bacteria problem in Lake George from leaking septics (that Adirondack Explorer covered a few years ago), and he had mentioned research from East Caroga Lake that had supposedly found elevated septic-related nitrate levels (https://www.adirondackalmanack.com/2021/01/adirondack-survey-seeks-feedback-from-potential-residents.html/#comment-1391032), although I have never been able to find that via Google. But the rationale there is that if relatively reactive, poorly soluble and non-conservative contaminants like coliform or nitrate ions are making their way into surface water, then the highly-polar and analytically difficult-to-detect PPCPs (you really should be using LC-MS/MS to detect these types of compounds with any high degree of sensitivity) should certainly be making their way into ground and surface water as well–scalable technologies to remove such compounds from wastewater just don’t really exist. The literature cited at the foot of the above comment is a goldmine on this under-researched subject in my opinion! I have read nearly all of it, a good amount of which during this past year. The ubiquitous acid-rain or road salt related water studies are important, but we should be prioritizing this other type of research in our region for sure!
A lot of good messages conveyed by Paul Hetzler. I would like to add that little is known about groundwater characteristics in the Ads and that groundwater flow is a very complicated science. Also, the author underestimates the characteristics of depth of wells and groundwater traveltimes in the Adirondacks. This morning I computed the average depth and median depth of 8,264 wells within the blueline (boundary of the Adirondacks) using records collected by the DEC from 2000-2021. The average well depth in the Ads was 322 ft, with the median depth of 285 ft. That means half the wells in the Ads are greater than 285 ft in depth. I was surprised on how many wells were between 400 to 650 ft deep. The deep wells that tap fractured bedrock and that have relatively low well yields (<3 gal/min) suggest that these wells are tapping bedrock aquifers of very low permeability in which the age of groundwater could be hundreds or even thousands of years old. It should also be mentioned that the many deep wells in the Ads suggest they are tapping confined aquifers, which would have a relatively impermeable overlying layer on top of the aquifer which would inhibit migration of contaminates from seeping into the underlying aquifers. But again, little is known about the extent and location of these confining units and artesian aquifers in the Ads.
Todd, very good points. The research into groundwater pollution is way behind where it should be, considering all of the people in the United States who are living off-utility. There is much better research coming out of Canada and Australia in that area. But you are right: current research suggests that even through sandy soils, conservative solutes can move very slowly (typically centimeters/day); this is part of what makes this type of research so difficult. In my above comment, I should have added that the latter part was from a previous discussion that emphasized the emerging research on shallow-ground and surface water contamination originating from the treated effluent of functioning septic systems (OSWTS). Even if this may not be a major concern (at least not immediately) for some people drawing from deep wells bored into mountain sides away from surface water (although, see chloride/road salt ADK groundwater contamination studies), avoiding the introduction of these types of pollutants into soils in the Adirondacks is made absolutely paramount by the high risk for ground and surface water contamination posed to down gradient areas by OSWTS that are built on the steep slopes with shallow, low-permeability glacial till subsoils that are ubiquitous throughout the Park…People living high-and-dry in the Adirondacks may not pollute their own wells for decades, but they very well may pollute the lakes, wetlands, rivers and wells downhill.