What is the problem with septic system drainage?
When you run water in the sink, shower, or flush the toilet, the water that runs down the pipes carries pollutants and bacteria with it. This water is called wastewater, and septic systems are the most common way to treat it on the Eastern Shore. Wastewater from your home drains into a septic tank, where solids sink to the bottom and separate from the water. In a conventional septic system, underground pipes carry this water into a trench called a drain field to be cleaned.
On the Eastern Shore, these drain field trenches are dug 18-24” underground, and they need to stay dry for the water to drain through them. If ground stays wet too close to the surface, those pipes can stop draining during rain or high tides. If septic pipes empty into wet soil, people sometimes notice the water in their lawn smells bad. The toilet water can also come back up the pipes into the bathroom.
What causes this problem?
Groundwater level is the distance below ground where the soil stays wet. For septic systems to drain correctly, this level needs to stay at least three feet below the ground surface.
The groundwater on the Eastern Shore is rising closer to our feet. Rain, tides, and ocean levels can change how close it gets at different times. Soil is like a sponge with a lot of tiny holes. In the hot summer, the soil sponge is drier and drains more easily, so water underground stays low, away from the surface. When the weather is cold or rainy, the soil “sponge” gets full of water, and it stops absorbing as much. When underground septic pipes drain into this full sponge, the bacteria can move through the soil to pollute nearby water sources like wells and streams. Sewage can also come back up the toilet or into people’s yards.
What does this mean for the future?
The underground water level is different everywhere on the Eastern Shore, and it changes between winter and summer. But the ocean level is also getting higher, and tides are getting higher too. This means that in the future, whether it is hot or cold outside, the soil sponge will be wetter than it has been in the past. From now on, the location of a septic drain can change whether or not the whole system will work.
We estimate that by 2040, about 7,800 home septic systems on the Eastern Shore will be in areas where groundwater is less than three feet.
Some government grants cover septic upgrades or replacements, but maintaining an upgraded system can be too expensive for many people. A typical septic system costs $5-10k. Special systems that clean waste water even in wet areas that don’t drain is $30-40k. For the whole Eastern Shore, the cost of replacing 7,800 at-risk septic systems at $20k each is around $156,000,000.
What can be done?
SEPTIC MAINTENANCE
Regular cleaning of your septic tank is important to make sure toilet waste does not overflow underground. Check how often your tank needs to be pumped based on how large it is and how many people use the toilet.
INSTALLING RECLAMATION AND REUSE SYSTEMS
These compact systems fit in a garage or utility room. They are fully automated to remove solids, soluble organic material, ammonia, and bacteria from wastewater. This reduces groundwater use and lets residents reuse water for laundry, flushing the toilet, and watering your plants.
INSTALLING ALTERNATIVE SEPTIC SYSTEMS
Some people use special septic systems that treat wastewater before it goes into the ground. These systems can filter out more pollutants and reduce harmful bacteria, which helps in areas where the soil is too wet for a regular septic system. These systems can be costly to install and maintain. Septic repair and installation grants are available through local government and the Planning District Commission.
INSTALLING MOUND SEPTIC SYSTEMS
Some people in areas where the groundwater is close to the surface build a small mound to make the ground higher and raise the drain field. They use a pump to move the wastewater up higher on the mound to drain. Mound systems can work better than conventional systems in places where the ground is often too wet.
COMMUNITY SEPTIC
A community system spreads financial and maintenance burdens among multiple property owners. Towns can apply for grants to install A) municipal wastewater infrastructure, where possible or B) a community septic system that could be used by many houses.
Livability Tool Research
Our science team researched the underground water depth across the Eastern Shore to find out which places may need extra attention to avoid septic drain issues. This data is included in the interactive Livability Tool.
Resources
Clean Water Financing and Assistance
VA Department of Environmental Quality
Septic Grant Assistance Program
How Septic Systems Work
Onsite Sewage System Owner Responsibilities
VA Department of Health
Virginia Household Water Quality Resources
Virginia Tech Extension Office
Safeguarding Septic Systems from Natural Disasters
Environmental Protection Agency