How Long Does Soil Remediation Take?

How Long Does Soil Remediation Take?

Soil remediation is the process of removing or replacing the soil to get rid of contamination. Soil contamination occurs when toxins get mixed with the natural compounds of the soil. 

Many times, these chemicals come from industrial activity or hazardous waste such as heavy metals and/or pesticides. However, contamination can come from many places including:

• Livestock manure runoff
• Farming chemicals
• Failure of a septic system
• Improper waste disposal
• Failing underground oil tanks
• Nearby industrial activity

If toxins are present in the soil, you must be proactive with soil remediation to eliminate the contaminants and restore the safety of your land. 

Some common soil remediation strategies include bioremediation, soil washing, and thermal desorption. The effectiveness of these options depends on the specific type of contamination in your soil as well as how extensive it is. 

These soil remediation technologies can be used to separate out the chemicals, but sometimes it may be necessary to remove the contaminated soil and replace it with clean fill. 

How Long Does Soil Remediation Take? 

Excavating contaminated soil can take one day or several years. The actual time it takes to excavate the contaminated soil depends on several factors including: 

• Large contamination area
• Depth of contamination
• Contamination below the water table

Time by Type of Soil Remediation 

Each type of soil remediation strategy takes a different amount of time. However, in all strategies, one of the primary factors is how much soil is contaminated. 

Bioremediation 

Bioremediation occurs by stimulating the growth of certain microbes to use contaminants, such as oil, as a source of food and energy. As a byproduct, the microbes release water, carbon dioxide, and other non-harmful amino acids. The microbes secrete enzymes similar to the way the human body makes saliva and stomach bile. The enzymes break down the contaminants into smaller pieces. Then, the microbes can consume the broken-down contaminants. 

Ideal environmental conditions are necessary to start the bioremediation process including a balance of temperature, surface pH, available moisture, and other factors. In the right environment, with ample food supply, the microbes reproduce. More microbes can then further aid in the removal of additional contaminants. The cycle repeats until the food source is depleted. 

Due to the need to maintain environmental conditions, it can take weeks, or even months for microbes to clean up a site. The primary consideration is the number of contaminants present in comparison to the number of microbes present. 

Soil Washing 

Soil washing is a remediation strategy that removes contaminants by washing the soil with a liquid (often a chemical additive), scrubbing the soil, and then separating the clean soils from contaminated soil and wash water. 

The concept of soil washing is based on the idea that contaminants will bind with fine-grained soils like silt and clay. These—in turn—are prone to bind with coarse-grained soils like sand and gravel. The main goal of soil washing is to separate the contaminated fine-grained soils and wash water from the cleaned coarse-grained soils. 

The contaminated soils and wash water can be treated or disposed of. The washed soils may be reused as a backfill at the site if all contaminants have been successfully removed. Soil washing can be broken into six steps: 

• Pretreatment 
• Separation 
• Coarse-grained treatment 
• Fine-grained treatment 
• Process water treatment 
• Residuals management 

Soil washing is a very fast method. The process can be run at a very high rate of around 100 cubic yards per day. Soil washing is often also used in conjunction with another remediation method because it can concentrate the contaminants down into a smaller volume of soil which can be easily treated by another strategy.

Thermal Desorption 

Thermal desorption removes organic contaminants (including volatile organic compounds and some semi-volatile organic compounds) from soil by heating it in a machine called a thermal desorber to evaporate the contaminants. Semi-volatile organic compounds require higher heat than volatile organic compounds. The contaminants are evaporated separated from the solid material. 

Thermal desorption may take a few weeks to a few years. Cleanup time will depend on several factors, including: 

• The contaminated area is large or deep. 
• The desorber is off-site. 
• A lot of debris must be crushed or removed. 
• The desorber is small. 
• Contaminant concentrations are high. 
• The soil contains a lot of dust, clay, or organic material. 

Most thermal desorbers can clean over 25 tons of contaminated soil per hour. 

Benefits of Faster vs. Slower Soil Remediation Methods 

Bioremediation is the slowest method while thermal desorption and soil washing are much faster. 

One difference in the strategies is how the contaminants are disposed of. With soil washing the contaminated soil and wash water must be processed. 

The wash water must be treated in order to be reused in the soil washing process or to be disposed of in sewers. Disposing requirements are stringent, so recycling the water back into the system is the preferred choice as long as it does not interfere with the washing process. 

Contaminated fine-grained soils may be disposed of in a landfill. If they are still considered contaminated, they may require further treatment before disposal. 

When it comes to thermal desorption, gas collection equipment captures the contaminated vapors. The vapors often require further treatment, like removing dust particles. The remaining organic vapors are usually destroyed using a thermal oxidizer. 

The thermal oxidizer heats the vapors to high enough temperatures to convert them to carbon dioxide and water vapor. At sites with high concentrations of organic vapors, the vapors may be cooled and condensed back to a liquid form. The liquid chemicals may be recycled or incinerated. If the concentrations of contaminants are low enough, and dust is not an issue, the vapors can be released without treatment into the atmosphere.

While bioremediation takes much longer, once the process is complete, the microbe population will naturally decline. The microbes also do not create any residual waste that needs to be processed or treated. The carbon dioxide, water, and other amino acids they produce absorb naturally into the environment without any negative impact. 

Need Soil Remediation Services? Contact Mikula.

At Mikula Contracting, we offer both residential and commercial soil remediation services in New Jersey. Contact us today for a quote.

by Dennis Mikula Jr.

Using Test Pits for Soil Exploration

Using Test Pits for Soil Exploration

Surface exploration can provide you with many clues about the stability of the ground. However, it doesn’t provide you with the full picture. For that reason, many contractors and engineers will utilize test pits for soil exploration.   

Just as the name would imply, a test pit is a hole dug into the ground that allows you to test the soil. They often aren’t very deep, but they provide great insight into the composition of the soil and its layers. Not to mention, a soil pit is one of the most affordable options for soil exploration.

That’s not all!

In this article, we’ll cover the purpose of soil testing so that you can better understand how a test pit is used. We also cover some of the different options for soil exploration methods so that you can compare them to test pits and trenches.

Purpose of Soil Exploration

Geotechnical engineers and contractors in New Jersey often want to explore the soil for safety reasons. They give you the opportunity to:

• Look for Soil Properties That Could Impact Construction: When you explore soil, it’s important to look for any soft matter, such as clay or sand. These materials create instability. You should also look for sandy loam soil as it exhibits great drainage properties. 
• Determine Materials for Construction: More often than not, you won’t find the perfect soil composition in your test pit. That’s okay, however. There are many ways you can adjust the type of construction materials to fit your land’s soil. Soil exploration allows you to see which materials will work best and the extent of adaptations you will need to make.

• Locate and Check Groundwater Conditions: Groundwater can be a blessing when it’s in the right place and a curse when it’s in the wrong place. If you are building a home in an area with a high water table, you will have to be cautious of foundational issues and basement flooding. On the other hand, a water table can be great if you need to put in a well! 

• Diagnose Cause of Existing Structural Failures: In some cases, soil exploration might be done after construction. If an existing structure shows signs of structural issues, including shifting or cracked foundation, you might need to examine the ground beneath it.

Soil Exploration Methods

When you are testing ground conditions, there are several factors you must consider. These factors can help you determine which tests to perform. They can also aid in making predictions about your soil and its stability. To make sure you get the most out of your soil tests, you should consider: 

Excavated Test Pits

Test pits are one of the most common methods of soil exploration. They are perfect for looking at shallow depths as they are simple and fast to dig. You can do so manually with the help of local labor. When done by hand, a test pit is one of the most economical soil exploration methods. In some cases, you may prefer to hire contractors to use heavy equipment excavation tools.

We also find this method especially useful because it allows you to observe the soil profile up close. You can easily see the variation in each layer, and you can examine the different materials. This view can help you diagnose any fill material that may pose a threat to the stability of the ground.

Auger Boring

If you need to reach more depth, auger boring is another option. It is a method used for shallow or deep collections. It is done by using an auger to drill into the soil. As it makes its way down into the ground, the auger fills with soil, and it brings the samples to the surface where soil experts can examine them.

While this method allows you to reach greater depths, it is more costly. Not to mention, the process causes a lot of disturbance while collecting the samples. That means that it can be challenging to see changes in the soil strata. Using this equipment can also be much more expensive than manually digging a pit.

Wash Boring

When dealing with softer materials like clay and sand, wash boring is the better option for soil exploration. The name comes from the jet stream of water sprayed through a hollow drilling rod. The fragments then separate from the water and collect in soil samplers attached to the bottom of the drill rod. 

This quick and straightforward method is relatively inexpensive. It’s perfect for gathering undisturbed soil samplings. You can even use it in areas with limited accessibility. For example, it’s ideal for testing in swamps or on water.

Percussion Drilling

The percussion drilling method is also known as cable tool drilling. It is often used to dig wells. However, it is also a popular method for examining soil in areas with boulders and rocks. You can even locate cavities and weaknesses in the rocks by comparing drill rate changes. It’s important to keep in mind that the blows of the chisel in percussion drilling cause disturbances to the soil at the bottom.

Rotary Boring

Lastly, you can use rotary boring. It is one of the fastest methods. Despite its speed, it doesn’t disturb the soil as much as some of the other methods. Unfortunately, the cost and bulkiness of the equipment deter contractors and engineers from using it. The drill also doesn’t do well with soil that contains large pieces of gravel.

Use a Test Pit to Explore Soil at Your NJ Construction Site

If you would like assistance with digging a test pit or trench, Mikula is happy to help. Our contracting company has over 75 years of experience with excavation services. Therefore, you can count on our experts to dig a safe test pit for you and your geotechnical engineering crew.  

To get started with your soil test pit excavation, give us a call. We are happy to schedule a consultation before we dig to discuss your soil testing needs. You can also reach out to our service representatives by submitting our online quote form.

by Dennis Mikula Jr.