Risk-Based Clean-Up

Risk-Based Clean-Up

Risk-Based remediation addresses the highest level of contamination from a leaking underground storage tank, with levels reported above 10,000 PPM. According to the DEQ, a risk-based clean-up offers the greatest amount of flexibility and adaptability to site-specific conditions. However, it is also the option that might require collecting additional site data and evaluation of more alternatives than a soil matrix or generic remedy clean-up. Risk-based clean-ups are the most rigorous option, with the collection of several soil samples to determine the magnitude and depth of contaminated soil, as well as how far the contamination has spread. The most important aspect of a risk-based clean-up is the evaluation of current and reasonably likely future risks to human health and the environment.

A risk-based remediation involves a soil investigation, which examines the pathways the contamination has likely spread. This pathway evaluation determines where the contaminants were released, how the contaminants can be transported to new locations and the reasonably likely ways that people may come into contact with them. Tests need to be conducted on enough samples to determine the lateral extent, as well as the depth of the petroleum contamination.

There are three investigative phases of concern while conducting a risk-based clean-up, phase two and three may not be necessary if the area of contaminated soil is limited enough in extent. Below are the steps, in order, that are required by the DEQ in order to close a risk-based clean-up:

Risk-Based Clean-Up and Free Product, Groundwater and Soil Vapor Gas

Petroleum Contaminated Soil (PCS) and/ or Free Product:

Up to seven (7) soil samples are taken to establish a representative sample and delineate the vertical and lateral extent of the pocket of petroleum-impacted soil, and potential or actual groundwater impacts. If it is determined that there is free product or large volumes of heavily contaminated soil, from which product may continue to migrate, mitigating the risk by excavation and off-site removal would be required, to the maximum extent practicable.

Risk-Based Clean-Up

Petroleum Contaminated Soil (PCS) seen during an excavation. The PCS is pictured here in the greyish color.

Risk-Based Clean-Up

The side view of the PCS, here you can see the coloration difference between the contaminated and the native soil.

Risk-Based Clean-Up

Free Product refilling into a sample boring hole

Risk-Based Clean-Up

Free Product within a sampling tube

Groundwater:

Has groundwater at the site at risk or has it been impacted by the diesel contamination?

In order to determine if groundwater has been or could be potentially encountered, a 10’ separation is required by the DEQ between the vertical extent of the contaminated soil and any potential shallow groundwater.

If there is no impact or potential impact to groundwater?

The groundwater investigation is now completed, no further action would be required.

If groundwater has been or has the potential to be impacted, what are the next steps?

A representative well will be installed in the source area to determine if groundwater has been impacted by the release. The installation of the representative well is designed to obtain a groundwater sample to measure, if any, the water level elevation in the contaminated water or soil.

If the samples in the representative well have detections that exceed the DEQs Ingestion and Inhalation from Tap Water Risk-Based Clean-Up levels, a groundwater investigation is necessary. The groundwater investigation determines the extent of the contaminated groundwater, and whether it is limited only to the property of the leaking UST or if extends to neighboring properties.

If the samples in the representative well meet the DEQ Ingestion and Inhalation from Tap Water Risk Based Clean-Up levels, no further action would be required.

The 10’ separation boring cannot be obtained due to site conditions, what happens to the investigation?

If a 10’ separation boring cannot be completed due to examples like refusal (rocky soil, etc.) or if the tank is too deep, per the DEQ a Beneficial Well Survey would need to be conducted.

A Beneficial Well Survey determines if a release of hazardous substances has impacted or has the potential to impact groundwater or surface water, through contaminant migration. These determinations will be used for evaluating exposure pathways in human health and ecological risk assessment; for identifying hot spots of contamination; and for selection or approval of remedial actions at hazardous substance clean-up sites.

The DEQ requires the survey to identify all properties that are in proximity to the site with the leaking underground storage tank, which may be utilizing a water supply well. The well may be used for drinking water, irrigation, etc. DEQ regulations considers that any well on a property that is for domestic use, be accounted for. These surveys can and are conducted within and outside city limits.

Grd Water

Groundwater encountered within an opening within an underground storage tank.

Vapor Intrusion from soil or groundwater:

Vapor intrusion is the migration of Volatile Organic Compounds (VOCs) from the subsurface into buildings. Per the DEQ, vapors released from volatile substances can be slowly released from underground spills. These volatile constituents move upward through the pores in the soil, when the soil is exposed during excavation, as well as, from contaminated groundwater. The DEQ requires Soil Vapor Gas sampling (SVGs) to assess the potential of carcinogenic vapors entering residential buildings. When certain constituents of interest, such as benzene, ethylbenzene and naphthalene concentrations exceed the DEQ Vapor Intrusion into Residential Buildings Standards, soil vapor gas sampling would be required.

To assess the potential cancer risks from vapor intrusion into homes, soil vapor gas sampling is triggered if any of the following variables apply:

  • The plume of contamination exceeds 65 cubic yards
  • There are, or likely to be, buildings within 30 feet of Volatile Organic Compounds (VOCs)
  • A 10’ separation cannot be established between the vertical extent and any potential shallow groundwater

Due to site specific factors, the number and sample locations may vary. Sampling may be conducted within the home or on the exterior of the building, either through the sub-slab and/or the soil.

Risk-Based Clean-Up

Soil Vapor Gas Sampling at the exterior of the property

Risk-Based Clean-Up

Sub-Slab Sampling, in the interior of the building

For a more in-depth overview of the DEQs requirements and standards regarding Risk-Based Clean-Up and leaking tanks, please visit their Leaking Underground Storage Tank Program (LUST site) DEQ LUST Site.

UST Tank Search for Buyers

UST Tank Search for Buyers – Common Questions

As a Buyer, searching for an underground storage tank has become integrated as part of the inspection period. These are some of the most common questions that we are asked regarding the tank inspection process and why it is important to protect yourself before you buy.

What is an underground storage tank (UST)?

Homes, apartments, farms and some businesses that are currently or were previously heated using diesel heating oil, used an underground storage tank (UST) to store the heating oil. The USTs were usually buried in the yard, and copper tubing or steel piping was installed to deliver the diesel from the tank to the furnace. In Oregon, an estimated 100,000 USTs were installed for home heating.

UST Tank Search for Buyers

UST Tank Search for Buyers – Rendition of an underground storage tank (UST) buried in a yard, with the supply lines running into the home.

Why should I worry about a UST?

Underground storage tanks are made of steel, which are selected for their strength, not for their corrosion resistance. Therefore steel USTs rust through, given enough time. Like a roof, steel storage tanks have a life of about 25 years, and like a roof it is cheaper to replace the tank or convert to another heat source before it leaks and the damage is done.

UST Tank Search for Buyers

UST Tank Search for Buyers – Removed tank with numerous holes, this allows the diesel fuel to leak into the surrounding soil.

Performing the UST tank search

How do you find an abandoned UST?

The best way to determine if there is an abandoned oil tank on the property, is to conduct a tank search.

How do you perform a tank search?

EcoTech first will perform a Tank Background Search, this entails a detailed examination of state and local databases, as applicable. Besides years of on-the-job experience, our technician conducts a visual inspection for product lines and fill or vent pipes, utilizes metal detectors and Terra, our specially trained Petroleum Detection K-9.

UST Tank Search for Buyers

UST Tank Search for Buyers – Terra finds a tank

UST Tank Search for Buyers

UST Tank Search for Buyers – The UST Terra found during the tank search, is now marked out for sampling.

What if there is an in-service tank already on the property, should I still do a tank search?

EcoTech highly recommends doing a tank search to rule out any additional tanks that may or may not be on the property. On average our tank searches cost $99.00, during the inspection period this is money well invested. Not only does a tank search give you peace of mind that there are no additional tanks on the property. It can also save you from years of worry or money spent if there is indeed an additional leaking tank on the property, which you now own and are responsible for cleaning up.

 

UST Tank Search for Sellers

UST Tank Search for Sellers – Common Questions

As a homeowner, you may be thinking about or are preparing to put your home up for sale. For some homeowners, you may want to perform a tank search to prepare yourself for any unforeseen surprises during the home inspection period. On the other hand, you may know that there is a tank on your property that was decommissioned and never registered with the DEQ or that there is an abandoned oil tank, but you don’t know where. These are some of the most common questions that we are asked regarding the tank inspection process and important information you should know before you sell.

What is an underground storage tank (UST)?

Homes, apartments, farms and some businesses that are currently or were previously heated using diesel heating oil, used an underground storage tank (UST) to store the heating oil. The USTs were usually buried in the yard, and copper tubing or steel piping was installed to deliver the diesel from the tank to the furnace. In Oregon, an estimated 100,000 USTs were installed for home heating.

UST Tank Search for Sellers

UST Tank Search for Sellers – Rendition of an underground storage tank (UST) buried in a yard, with the supply lines running into the home.

Why should I worry about an UST?

Underground storage tanks are made of steel, which are selected for their strength, not for their corrosion resistance. Therefore steel USTs rust through, given enough time. Like a roof, steel storage tanks have a life of about 25 years, and like a roof it is cheaper to replace the tank or convert to another heat source before it leaks and the damage is done.

UST Tank Search for Sellers

UST Tank Search for Sellers – Shot from interior of tank, many small holes in the UST, which will cause diesel fuel to leak into the surrounding soil.

Performing the UST tank search

How do you find an abandoned UST?

The best way to determine if there is an abandoned oil tank on the property, is to conduct a tank search. As the homeowner, you may also look for these tell-tale signs of an abandoned oil tank:

  • An Oil Fill Pipe, these are usually close to the ground and near where the furnace is located in your home.  The lid itself will usually indicate OIL in the center of the cap.
UST Tank Search for Sellers

UST Tank Search for Sellers – Fill pipes can appear in multiple places within a property, in a walkway, grass, driveway, and even under a deck are a few examples.

  • A Vent Pipe, this is usually attached to the home, about two to eight feet up the side of the house and it is 1.25 to 1.5 inches in diameter with a small vent cap on it.

 

UST Tank Search for Sellers

UST Tank Search for Sellers – 4 different types of vents and their locations.  Fill vents can come in different sizes, colors, and may be placed at varying sections of the home.

  • Product lines, may be found sticking out of the ground in the yard, in a crawlspace or basement floor.  Product lines may still be attached to a basement or crawlspace wall next to water or gas pipes.
UST Tank Search for Sellers

UST Tank Search for Sellers – Crimped product lines may appear as random pipes sticking out of a basement floor or out of the dirt near the home in the yard. A product line may also appear running up a wall in a basement or crawlspace, like the far right picture (the thin line on the right)

  • Patching, will be present on a basement floor, it appears as though a pipe has been removed and covered with concrete.  The patching may appear as a bad “patch job” with numerous bumps and grooves.
UST Tank Search for Sellers

UST Tank Search for Sellers – Patching on a basement floor.

How do you perform a tank search?

EcoTech first will perform a Tank Background Search, this entails a detailed examination of state and local databases, as applicable. Besides years of on-the-job experience, our technician conducts a visual inspection for product lines and fill or vent pipes, utilizes metal detectors and Terra, our specially trained Petroleum Detection K-9.

UST Tank Search for Sellers

UST Tank Search for Sellers – Terra finds a tank within a planter.

UST Tank Search for Sellers

UST Tank Search for Sellers – The tank that Terra found is marked out. The purple arrow indicates where the vent pipe has been removed from the siding. The red arrows indicate the length of the tank, marked with orange flags as well as the tip of the measuring tape.