Residential Tank Cleanups

There are two basic cleanup options available for DEQ file closure: removing the contaminated soil or completing a risk assessment of the contaminated area to determine if the soil can remain in the ground. Since the Heating Oil Tank Department was created at the DEQ in March of 2000, risk based closure has become the most common type of residential tank cleanup. However, risk based closure in not always possible; it is dependent on site conditions. With over 10 years of residential tank cleanup experience, we can tell you the best option for your property.

There are many parameters we investigate when completing a risk assessment around a leaking heating oil tank. We investigate site specific conditions such as level of benzene and diesel in the soil, volume of the contaminated area, depth and use of groundwater in the area, and soil type. The process always begins with decommissioning the tank. Once the tank has been decommissioned we collect 5-7 additional soil samples from around the tank area. These samples are submitted to an independent laboratory for analysis. The purpose of these samples is to determine how deep and widespread the soil is contaminated around the tank. Once we have the results back from the lab we will confirm that the site meets all the criteria for DEQ site closure. The decommission can then be completed and the site restored. We complete a full report to document the project and submit it to the DEQ for review and file closure.

Sometimes the level of contamination in the soil is simply too high to leave in the ground. In these circumstances the highly contaminated soil needs to be excavated from around the tank. The method we use to excavate the soil depends on the access to the tank area. If the tank is in an area where we can use our small rubber track excavator we will decommission the tank by removal and then excavate the contaminated soil. If the tank area cannot be accessed with the machine, we can remove the bottom of the tank and excavate the soil by hand. We do not know exactly how much soil needs to be excavated until we get started digging. When we are digging with the machine we begin by excavating approximately 7 tons of contaminated soil. When we are digging by hand we usually excavate no more than 3 tons of soil. After the day of excavation we sample the excavation area to confirm all the contamination has been removed or to determine what levels are still remaining. If lab analysis confirms all the contaminated soil has been removed then we can backfill the excavation, restore the site, and submit a cleanup report to the DEQ. If lab analysis determines there is still contamination remaining but at significantly lower levels, then we may conduct a risk assessment and attempt to close the site using the risk based rules as described above. There are times when the levels remaining are still too high to leave in the ground. In these circumstances we will have to return to the site and excavate more soil.

Residential Tank Project Inquiries

Why cleanup the soil around a leaking tank?

Cleaning up contaminated soil keeps your family safe from harmful vapors inside and outside your home. Additionally it protects the quality of the groundwater which in turn keep the Northwest’s rivers healthy.