Episode 13 - Septic Systems

March 2022


Groundwater is water held underground in the soil or in pores and crevices in rock. Over 44% of the population in America depends on groundwater as a primary water source.


The second week in March is National Groundwater Awareness Week, often the focus is on groundwater wells and the recommendation to test and inspect wells annually, but today we’re going to talk instead about septic or wastewater systems.


Septic systems are underground wastewater treatment systems, commonly used in areas where municipal water and sewer services are not available.  A combination of nature and technology are used to treat wastewater from household plumbing produced by bathrooms, kitchen drains, and laundry. Systems may vary in their method of filtration and discharge but common elements include a septic tank and a drainfield.


It is a homeowner’s responsibility to have their septic system inspected and maintained regularly. Septic systems should generally be inspected every three years and pumped every 3 to 5 years.

Learn the location of your septic tank and drainfield and avoid driving or parking on them. You should also avoid planting trees or shrubs in the area as their roots can cause costly damage to the system.


There are steps you can take to avoid clogging or overloading the system. Only human waste and toilet paper should be flushed down your toilet. Avoid rinsing grease or oils, coffee grounds, and chemicals down your drains. Eliminate or limit using a garbage disposal. Stagger the use of water-generating appliances or activities like dishwashing, laundry, and taking a shower. These simple steps will help to protect your home, health, and system.


If you are looking to install or modify a wastewater system you will need to consult the Ravalli County Environmental Health Department (RCEH) and get a permit. Every septic system installed or modified after 1982 should have a permit on file with the RCEH.


The county and state regulate wastewater systems with groundwater in mind. RCEH has over 20 years of historical groundwater monitoring information and an active groundwater monitoring program, they can help advise.


State of Montana Department of Environmental Quality regulations require wastewater systems to have at least 4 feet between waste hitting the soil in the drainfield and groundwater level at its peak season. Peak groundwater will vary by location, with some areas heavily influenced by the river and others more affected by the irrigation season, but is defined as two weeks of fall after a steady rise.

The process starts with an 8-foot hole to determine if there are any indications of groundwater.  Indications may be subtle like mottling or staining of the soil. If any indication is noted then groundwater monitoring is required to determine if there needs to be a “vertical setback” of a wastewater system or if a system is possible at all.


To monitor groundwater a 10-foot perforated pipe is installed 8 feet into the soil with 2 feet above. The perforations allow groundwater to move within the pipe and allows us to see what is going on with the groundwater level. RCEH monitors groundwater weekly. If there is any indication of groundwater in the top 52 inches then there can be no increased usage, as in no additional system or added bedroom count.


The RCEH office noted that “there should be no assumptions on groundwater”. Groundwater is very unpredictable.  Having a neighbor with a permitted system doesn’t mean you will get approval.

The enrollment period for RCEH’s groundwater monitoring program ended on March 1st.  Late enrollment is possible, however you run the risk of missing the peak. Last year RCEH did a little over 350 pipes, but noted that enrollment is a little down this year.


Learn more by calling the Ravalli County Environmental Health Department at 406-375-6565 or emailing RCEH@rc.mt.gov. Their office is located at 215 South 4th St. Suite D in Hamilton if you prefer to stop in or are looking for a well testing kit.


Additional Resources:

EPA Septic Smart Resources

CDC Groundwater Awareness Week

Ravalli County Environmental Health Home Buyer’s Guide

Annual Well Inspection

National Groundwater Awareness Week