Contaminated Septic Tanks - Expensive to Fix, Easy to Avoid

Ecology’s dangerous waste inspectors are finding an expensive problem at some small businesses – septic tanks contaminated from putting dangerous waste down the drain. This type of contamination can easily cost property owners up to $9,000 to clean up, whether they own the business or are leasing out the property.

What is a septic tank?

Septic tanks are a major part of an on-site sewage system (OSS). In the system, bacteria break down domestic waste solids, such as from toilets. The system releases the liquids and broken-down solids into a drain field that allows the soil to further capture and treat any impurities.

The tank typically contains three phases: a sediment layer on the bottom, a liquid “column” in the middle, and a scum layer on top.

What is the problem?

The problem is that workers at businesses with on-site septic systems may also put non-domestic waste, such as commercial or industrial wastewater, in the septic system. A lot of bad things can happen from this practice, worst of all contaminating the septic tank, groundwater, and property with dangerous waste.

The most common dangerous wastes we find in septic tanks are solvents and heavy metals (lead, mercury, copper, etc.). Bacteria in the tank cannot decompose these materials, so these contaminants build-up in the sediment layer and stay dissolved in the liquid column. The tank can release them into the drain field where they bind to the soil or percolate into the groundwater.

Even if the wastewater does not contain enough dangerous materials when it is generated to designate as dangerous waste, it can still contaminate the tank through long-term accumulation of metals and chemicals.

If an inspector finds that a business is discharging commercial or industrial wastewater to a septic tank, that discharge must stop immediately. Each phase of the tank needs to be sampled and tested to determine if the contents meet the definition of dangerous waste. Further sampling may then be required to determine if the contamination spread to the drain field and groundwater.

How much can it cost?

The main costs include sampling and testing the tank contents, cleaning out the tank, and properly disposing of the waste. Including labor and disposal costs, the total to clean-out a septic tank containing dangerous waste can be $3,000 to $9,000, or more.

A typical small business may end up paying $400 to $1,000, or more, just for sampling and testing the tank contents.

Cleaning-out and decontaminating a tank is considerably more expensive. Tanks typically come in two sizes – 1000 or 2000 gallons. A company must be qualified for dangerous waste pumping to pump out a contaminated tank. Estimates can vary from 30¢ to $3.00 per gallon, or more.

These costs are the responsibility of the property owner, but a tenant may ultimately have to pay the bill through civil litigation between the tenant and property owner. Ecology may also pursue penalties against the tenant.

What should people do with their commercial wastewater?

Businesses have options when it comes to disposing of commercial wastewater. The options aren’t as cheap and easy as discharging to the septic tank, but they are legal and cost less than cleaning up a contaminated tank, surrounding property, and groundwater.

Once the business ceases the discharge, it can:

• Recycle and reuse the wastewater through a closed-loop filtration system onsite; or
• Collect the wastewater in proper containers or tanks and send them offsite to a facility that can accept the waste.

Stay educated and avoid the risk

Tenants and property owners need to stay educated on what can and can’t be discharged to a septic tank. Whether you operate a business on your own property or rent to a small business tenant, discharging any commercial wastewater to an on-site septic system is dangerous to human health, the environment, and your wallet.