Hidden Groundwater Sources in Urban/Suburban Settings, by ALP

If you are ever find yourself in an urban or suburban setting and need water badly, there is a source of water you probably never thought of as accessible: groundwater. In my day job as an environmental technician, I frequently have to supervise contractors who are drilling observation wells in all sorts of urban and suburban settings. Sometime after drilling, I take samples from the wells and submit them to labs to test if they are contaminated. Basically, almost every transaction of a commercial or industrial property, and many residential properties also, will have several surface groundwater wells; so, you can imagine the number. I’ve taken samples from every sort of property, including gas stations, dry cleaners, factories, malls, strip malls, warehouses, apartment blocks, and more. The wells are frequently left in the ground for years at a time and often forgotten about, instead of decommissioned. There will be countless wells all over the urban and suburban landscape when the SHTF.

Groundwater Observation Wells

The observation wells I am speaking about are 1-2″ (2.5 – 5.0 cm) diameter PVC pipes sunk into the ground around a sand filter, which have slots at the bottom to allow the passage of groundwater. The top of the well is a 6″ (15 cm) diameter metal casing of steel or aluminum that can either be flush with the ground, or raised by about 3 ft (1 m) in a rectangular steel case. The flush wells are usually secured with two 1/2″ or 9/16″ bolts, but there are other variations. The wells can be anywhere from 7 to 60 ft deep (2 to 20 m), although usually around 15-20 ft (3 – 4 m) in the areas I have worked (southern Ontario and around Vancouver, Canada). The wells will be whatever the depth of the surface aquifer is in your area.

The purpose of the wells is to obtain samples for laboratory analysis to find out if the groundwater is contaminated around the well. When the industry picks a spot to drill, they usually don’t know if we are going to find contamination. They usually only know if there could be. So, the industry inadvertently drills a lot of clean observation wells along with the contaminated ones.

Is It Contaminated?

How can you know which are contaminated? Even after six years of testing groundwater on all sorts of sites, I cannot always tell if well water is contaminated simply by looking at it. However, there are many warning signs that indicate that it is unsafe to drink. In a bad situation, you may not have any other choice. Ultimately, the purpose of this article is to give you a sense of when it may be worth the risk to drink, and when it is absolutely not.

First of all, the industry drills wells in clusters around areas that have contaminated groundwater, so you shouldn’t bother opening the wells in the center of clusters. The wells at the periphery are best. Once the industry finds the edge of the contamination, we don’t usually keep drilling more wells, since the “edge” of the contamination is inferred to be somewhere between the center and the periphery. However, just because a well is at the periphery is no guarantee that it will be clean. Contaminants continue to migrate slowly with the flow of groundwater.

Secondly, I wouldn’t drink any wells that had dissolved metals as the potential source of contamination, because your senses may be unable to detect dissolved metals (lead, chromium, et cetera) that are very poisonous. So, I would stay away from wells that were around metalworks, foundries, and especially metal electroplating facilities.

Thirdly, the most likely case where you are going to find these wells is at gas stations. At a gas station, you know that the primary source of contamination is hydrocarbons (gas, diesel), so if your well doesn’t smell like gas or diesel, you’re probably going to be okay. The human sense of smell for these products is very sensitive, so you’re normally going to be able to tell almost immediately if it is bad to drink. That being said, the more protection you have the better. If you have a filter, be it sand, activated carbon, or ceramic, use it. If you have chlorination or UV treatment, use it. Hydrocarbons are immiscible and barely dissolvable in water, so if you pass them through an activated carbon filter it will remove almost all of them. However, you don’t want to try and filter very heavily contaminated water. Not only will you wreck your filter, the water may also contain poisonous dissolved metals that will not filter out. The metals come from soils exposed to reducing conditions (low oxygen environments). These conditions are caused by underground bacteria that consume the hydrocarbons and generate acidic wastes.

To access the groundwater wells, follow these steps:

  1. First of all, open the case, take a look, and take a whiff. It’s best if it looks clean and dry, but sometimes it will be flooded and muddy. This might still be okay, as the mud might be bentonite clay that is used in the construction of the well.
  2. Next take off the yellow or green plastic cap that can be twisted off or pulled off. Safety warning here: it is possible for the contents to be under pressure, so don’t open it right into your face. This is because the plug forms an air-tight seal, and the water table might have moved up since the last time it was open, causing the column of air in the PVC pipe to become pressurized.
  3. Look down the well. If you are lucky, there will be a plastic tube in the well with an inertial valve at the bottom. You might need a piece of wire to pull out the tubing because it is folded.
  4. Next, inspect the tubing for stains and smell. If all good, start jerking the tube up and down, which is how the pumping works. Have a bucket at this point to collect the water. At first it’s going to come out clear and then probably transition to cloudy/muddy. This mud is the sediment at the bottom of the well, and it is composed of fine particles of clay or silt. It won’t hurt you, but it will make the water taste really bad. It may also have bits of sand, depending on the well geology. The sediment will be grey or brown but most will settle down to the bottom of your container in fifteen to twenty minutes of sitting still. When clear, run through your filter and drink.

    I usually leave the tubing/inertial pump in the wells, because I don’t want to waste time cutting up the tubing and throwing it away. In my experience opening up wells drilled by other companies, there is often tubing left behind. Once you have some clean tubing, you can coil it up and use it later in another well.

The amount of water extractable from the well will heavily depend on the soils and the amount of penetration of the well into the water table. Sandy soils will allow water to pass easily, and therefore you will get water as fast as you can pump it, while wells sunk into clay soils may offer you just a few litres and then take hours or days to recharge. There may also be wells that have no water, which means the technician made a mistake and/or the groundwater table has fallen below the depth of the well.

Hopefully, you will never have to drink suspect water from an urban/suburban observation well, but maybe a forgotten observation well could save your life, if surface water sources are unavailable or are contaminated with disease vectors (groundwater tends not to have any microbial contamination).

Do not drink groundwater if:

  • there are bad smells (gasoline, diesel, chemical, basically any)
  • there are strange colours (purple, yellow, whatever)
  • there is more than one phase (indicating the presence of hydrocarbons, oils)
  • there are black stains on the pipe, pipe cap, or plastic tubing
  • there are wells around the well you are at
  • there are bad tastes, especially metallic tastes
  • near foundries, metalworks, or electroplating facilities

Groundwater is less risky to drink if:

  • there are no stains and smells
  • the water is clear (not cloudy) and has no colour
  • the sediment settles in 15-20 minutes
  • if you can pass it through a ceramic and carbon filter
  • if you know what the potential source of contamination was and can detect with your senses that it is not present in the water (as in, you are at a gas station with nothing else around, and you smell no hydrocarbons in the water).
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