Graphic organizer Grade 8 Health & Consumer Science
Pembury Farmhouse Well: Contamination Pathways and Protections
A cause-and-effect organizer where students trace five ways germs and nitrate can reach a fictional farmhouse well, the health risk of each, and how to prevent it.
Objectives
- Students will trace how each of five contamination sources can reach a private well through soil, groundwater, or a damaged wellhead.
- Students will identify the health risk of bacteria and nitrate in well water, including the special risk of nitrate to infants.
- Students will match each source to a protection step and a testing plan a well owner can carry out.
Vocabulary
- Groundwater
- Groundwater is water that has soaked into the ground and fills the spaces between soil particles and cracks in rock underground. It is a large underground source of fresh water that wells and springs draw from.
- Septic system
- A septic system is a small, private wastewater treatment setup buried in the yard of a home that is not connected to city sewers. A tank settles the solids, and the soil in the yard filters the water.
- Nitrate
- Nitrate is a form of nitrogen that plants use as food. It gets into water from fertilizer, animal waste, and septic systems, and too much of it is unhealthy for both people and streams.
- Coliform bacteria
- Coliform bacteria are common bacteria found in soil, on plants, and in the guts of animals. Most are harmless, but finding them in drinking water warns that germs may be getting in.
- Well casing
- Well casing is the pipe that lines the inside of a drilled well, keeping the hole from collapsing and stopping dirty water near the surface from leaking into the clean water below. It is one of the most important parts of keeping a well safe.
Also: private well
Teacher overview
Families who get water from a private well are responsible for keeping it safe themselves, because the federal rules that govern public water systems do not cover private wells. This organizer is a set of five cause-and-effect chains built from a fictional county inspector's notes on the Pembury family's farmhouse well and a short health department fact sheet: for each source, students trace how the contaminant reaches the well, the health risk, the protection step, and how the family would find out. Teaching note: students often believe that well water is pure because the ground filters it, or that clear, good-tasting water must be safe. Soil does filter some germs, yet cracks, damaged caps, shallow casings, and floodwater can let contaminants skip that filtering, and neither bacteria nor nitrate changes how water looks or tastes.
Organizer
Inspector's notes on the Pembury farmhouse well (fictional)
Read the notes and the fact sheet that follows them. Then complete one chain for each source in the table below.
- The well is about 40 years old and draws groundwater from a layer of sand and gravel.
- The septic tank and its drain field sit uphill from the well. The family does not remember when the tank was last pumped.
- Two horses graze in a pasture near the barn, and a manure pile sits at the pasture's edge. Both are uphill from the well.
- Each spring the family spreads fertilizer on a large vegetable garden next to the house.
- The well cap is cracked, and the top of the well casing is almost level with the ground. Water pooled around it after last spring's flood.
- The family is expecting a baby this summer.
- The family has never had the water tested, because it looks clear and tastes fine.
Facts from the county health department's sheet for well owners (fictional)
- Soil filters out some germs as water soaks down to the groundwater. A cracked cap, a casing that sits too low, or floodwater can let surface water into the well without passing through the soil.
- Sewage and animal manure can carry bacteria and viruses that cause diarrhea, vomiting, and stomach cramps. A lab test for coliform bacteria shows whether germs from the surface may be reaching the well.
- Fertilizer, manure, and septic wastewater all add nitrate to the soil. Nitrate dissolves easily in water, and the soil does not filter it out.
- Nitrate is most dangerous for babies under six months old, because it lowers the blood's ability to carry oxygen. It has no color, smell, or taste, so only a lab test can find it.
- Boiling does not remove nitrate. It drives off some of the water as steam, which leaves the nitrate more concentrated.
- Test a private well for coliform bacteria and nitrate at least once a year, after any flood, and whenever the water's taste, smell, or color changes. A flooded well must be disinfected and retested before anyone drinks from it.
Complete each chain from left to right. Each arrow means "leads to."
| Source | → How it reaches the well water | → Health risk | → Protection step | → How the family would know |
|---|---|---|---|---|
| 1. Septic tank and drain field | ||||
| 2. Horse pasture and manure pile | ||||
| 3. Garden fertilizer | ||||
| 4. Cracked cap and low casing | ||||
| 5. Floodwater around the well |
Testing plan for the Pembury family
| Question | My answer |
|---|---|
| What should the water be tested for? | |
| How often, and after which events? | |
| What should the family do before the baby arrives? | |
| What should the family not do if nitrate is found? |
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Completed Exemplar
| Source | → How it reaches the well water | → Health risk | → Protection step | → How the family would know |
|---|---|---|---|---|
| 1. Septic tank and drain field | Wastewater from the drain field soaks down into the groundwater. An overfull tank that has not been pumped sends out poorly treated sewage, and because the field is uphill, groundwater can carry it toward the well. | Bacteria and viruses from sewage can cause diarrhea, vomiting, and stomach cramps. Sewage also adds nitrate. | Have the septic tank inspected and pumped on a regular schedule, and keep grease and chemicals out of drains. | A lab test for coliform bacteria and for nitrate. |
| 2. Horse pasture and manure pile | Rain soaks through the manure and pasture, carrying germs and nitrogen into the soil. Runoff flows downhill toward the well, and nitrate moves down into the groundwater. | Germs such as E. coli can cause stomach illness. Nitrate is a special danger to babies. | Move the manure pile downhill and far from the well, cover it, and fence the horses away from the wellhead. | A lab test for coliform bacteria and for nitrate. |
| 3. Garden fertilizer | Fertilizer nitrogen turns into nitrate in the soil. Nitrate dissolves easily, so rain and watering carry it down into the groundwater. The soil does not filter it out. | Nitrate is most dangerous for babies under six months old, because it lowers the blood's ability to carry oxygen. | Use only as much fertilizer as the garden needs, avoid spreading it before heavy rain, and never mix or store it near the well. | A nitrate test, since nitrate has no color, smell, or taste. |
| 4. Cracked cap and low casing | Rainwater, insects, and small animals can get straight into the well through the crack and the low casing, skipping the soil that would filter them. | Bacteria from surface water and animals can cause stomach illness. | Install a sealed, sanitary well cap, raise the casing above the ground, and slope the soil so water drains away. | A coliform bacteria test, and checking the well cap for insects or debris. |
| 5. Floodwater around the well | Floodwater carries sewage, manure, and chemicals. When it pools over the wellhead, it can pour through the cracked cap into the well. | Floodwater can contaminate the whole well with germs that cause serious stomach illness. | After any flood, do not drink the water until the well is disinfected and a test shows it is safe. Use bottled water until then. | A coliform bacteria test after every flood. |
Testing plan for the Pembury family
| Question | My answer |
|---|---|
| What should the water be tested for? | Coliform bacteria and nitrate. |
| How often, and after which events? | At least once a year, after any flood, and whenever the water's taste, smell, or color changes. |
| What should the family do before the baby arrives? | Test for nitrate now, and use bottled water for mixing formula until a result shows the well water is safe. |
| What should the family not do if nitrate is found? | Do not boil the water to fix it. Boiling removes some water as steam, which makes the nitrate more concentrated. |
Differentiation
Support
Fill in the first chain (septic tank) with the class as a model before students complete the rest. Provide a word bank for the health risk column: diarrhea, vomiting, stomach cramps, nitrate, oxygen, and babies. Allow students to work in pairs and complete three of the five chains.
Extension
Ask students to draw a side view of the farmhouse, the well, the septic field, and the pasture on a slope, with arrows showing the direction groundwater flows. Then have them decide where on the property a new well should be drilled if the family replaced the old one, and justify the location using the direction of flow.
ELL supports
Pre-teach "septic," "manure," "fertilizer," "casing," and "nitrate" with a labeled picture of a farmhouse and its well. Allow the chains to be completed with short phrases, and pair each source row with a small icon so students can match notes to rows quickly.
Extensions
Students can find out what their county or state health department recommends for private well owners, including where to get well water tested. A county environmental health specialist can be invited to explain what an inspector checks at a wellhead and how families learn their test results.