Septic Decommissioning

How Septic Tanks Work

Septic tanks are a way of processing your wastewater on your property when your system is not connected to the city’s sewer main.  They are typically several feet long, constructed out of concrete, fiberglass, or specially treated plastic, and placed relatively close to the residence.  Your wastewater pipes are routed directly from your residence to the septic tank.  When wastewater enters the tank, gravity causes the waste to settle into three separate layers.  The top layer consists of the lightest waste that rises to the top of the water, such as fats, grease, and oil (typically referred to as scum).  The middle layer is water-based waste (also known as effluent), and the bottom layer is where the solid waste settles.

Septic tanks work as a sort of holding area for waste.  Once waste enters, it needs time to settle into its respective layers.  Bacteria breed inside the tank and feed on the waste, breaking the solids down into sludge and allowing scum to form on top of the wastewater.  These bacteria also work to break down contaminants in the effluent so that it can be safely disposed of; this is known as “treating” the wastewater.  This treated water then flows through a filter and exits the septic tank through a perforated pipe which allows it to seep into and nourish the surrounding soil.  The pipe is then covered with gravel to allow the water to seep out of the pipe into the and oxygen to enter the septic tank to keep the bacteria alive.

How Septic Tanks Break Down

Like any other system, septic tanks need to be maintained in order to maximize their life span.  A healthy septic tank can easily last you several decades, but there are some factors that can considerably shorten that time frame.  Some of the most common culprits are:

• Improper waste.  Septic tank systems are designed to treat wastewater and nothing more.  When foreign substances are introduced to the system, it can cause your pipes to become clogged and lower the effectiveness of your septic system.  Examples of this are grease, non-decomposable solids such as napkins and paper towels, and large quantities of strong household chemicals that eat away at the lining of the tank.
• Excessive levels of wastewater.  Septic tanks have specific capacities that they are built to handle.  When too much wastewater is introduced to the system, it can cause the effluent to be released into the surrounding soil before being fully treated.  It can also lead to solids not settling as they should, obstructing the filter or being pushed through it and clogging the drain pipe, leading to sewage backing up into your residence.
• Improper installation/settling.  Sometimes the gravel and/or soil surrounding the drain pipe is not installed properly, or settles and obstructs the holes of the drain pipe if it runs under a driveway or commonly walked path.  This prevents the treated water from exiting the septic tank, as well as limits the amount of oxygen that can enter, reducing the effectiveness and lifespan of the bacteria.

To get the most out of your system’s lifespan, it’s recommended that you have a professional come out to inspect your tank.  This inspection provides you with useful information such as how often you should clean out your septic tank, if your current system supports the needs of your household and is up to code, and provide additional recommendations for future maintenance.

Dangers of Improper Septic Decommissioning

When a septic tank is not properly decommissioned, or worse, left dormant for years, risks to your physical health and the environment can occur.  While septic tanks are designed to breed helpful bacteria, they can also create pathogens and toxic gases such as methane as byproducts.  If the septic tank is opened without the proper safety precautions, these are released and pose a risk of infection and an explosive hazard, as methane is a flammable gas.  Lastly, depending on the type of material used during the construction of the septic tank, corrosion can occur over time, allowing the waste to seep into the surrounding soil and creating the risk of cave-ins when walked or driven over.

Septic Tank Decommissioning Process

• Obtain a permit from the city or municipality to work on the septic tank system.  These permits are required to ensure that only licensed professionals are working on the system, due to the risks involved.
• Disconnect the water lines that run to the septic tank, as well as any electrical lines, if the system has them.
• Excavate the area around the septic tank to allow access.
• Open the septic tank and use a vacuum pump to empty any waste in the system, followed by a thorough rinsing of the tank.
• Decommission the septic tank.  There are several ways of doing this.  One is to remove the tank as a whole and fill in the hole with soil.  Another is to leave the tank in the ground and fill it in with an approved substance, such as sand, gravel, or concrete, sealing the tank, and replacing the dirt and grass on top of it.  Finally, in the case of metal tanks, some choose to crush the tank and bury it, but this is not often recommended, as it can release any residual contaminants into the surrounding soil.
• Once the tank has been decommissioned, a final inspection takes place to ensure that the process was performed according to city codes and statutes.

Hiring a Professional

The first step of any septic decommissioning work is to ensure you are hiring professional help that can get the job done quickly, safely, and efficiently.  We here at All Seasons Earthworks LLC have decades of experience working with all aspects of drainage systems and are qualified to work in all of Snohomish County.  If you are needing assistance decommissioning your septic tank system or simply want an expert opinion, we’re here to help.  Give us a call at 425-263-2075 today to get started.

Family owned and operated since 2000