Contaminated Soil Mixing Method
The contaminated soil mixing method is one of the most effective strategies for soil remediation projects involving heavy metal contamination. The keys to success are:
- Using the right reagent,
- Applying the correct dosage, and
- Achieving thorough mixing between the reagent and the contaminated soil.
When a remedial site has undergone extensive testing that identifies both the lateral limits and depth of contamination, it is recommended to establish a grid system over the area before mixing begins.
Grid System for Contaminated Soil Mixing
A grid system allows for even application and precise dosing of the stabilization reagent. Typically, grids of 25’ x 25’ or 50’ x 50’ are used when contamination is deeper than one foot. For shallower contamination, larger grids may be more efficient.
The grid layout helps ensure the reagent is applied at consistent dosages and makes it easier to allocate pre-measured amounts of the treatment chemical.
Blastox® 215, a proven heavy metals stabilization reagent, is highly versatile and effective across a wide variety of waste types, metal concentrations, and application methods.
Example Calculation of Reagent Dosage
Consider a 25’ x 25’ grid where contamination extends to a depth of 3 feet, and the soil has a density ratio of 1.4.
- Volume: 25’ x 25’ x 3’ = 1,875 cu. ft. (69.45 cu. yds.)
- Weight: 69.45 cu. yds. x 1.4 = ~97 tons
- Reagent dosage at 3%: 97 tons x 3% = 3 tons of Blastox 215
The 3% dosage is calculated after mixing, so the formula is:
97 tons ÷ (1 – 0.03) = 100 tons total after treatment
This ensures accurate reagent application during the contaminated soil mixing method process.
To apply Blastox 215 using a grid system, the predetermined amount for each grid is spread evenly across the surface. This can be done with a lime spreader or regular construction equipment, such as a skid loader or backhoe. If the contamination is in the top 6” to 10”, a disc or tiller can be used. For deeper areas, most contractors use a backhoe to mix in the reagent. The soil should be turned over, or mixed, with a backhoe or loader at least 5 or 6 times to achieve a proper contaminated soil mixing method. Water may need to be added if the soil or waste is dry.
If the contamination is deeper, it is recommended that the mixing be done in lifts, with each lift about 3 ft- 4 ft deep. Once one lift is mixed, a composite sample of the waste can be collected for testing. The sampling can occur immediately after mixing. When the test results show that the stabilization has achieved the project’s performance goal, the waste can be removed and stockpiled or loaded out directly, depending on the requirements of the work plan.
Dosage Determination
Dosage Determination for Contaminated Soil Mixing
Determining the correct Blastox dosage depends on the contamination profile:
- For homogeneous soil with lead contamination where TCLP values are below ~50 ppm, treatment dosage typically falls within a 2%–5% range by weight.
- Higher hotspot areas receive higher dosages, while lower contamination areas require less.
- In many straightforward projects, advanced treatability testing may not be necessary.
However, if the soil matrix is more complex (with sludges, debris, or varying waste types), treatability testing is recommended.
If advance testing is conducted, a waste sample from the highest TCLP data point is always the best starting point for the treatability test. Also, if there is a large quantity of soil or waste involved (5,000 tons +), it can be helpful to pick another sample from a data point that represents the largest volume of soil. When multiple samples undergo treatability testing, it’s common to end up with different recommended dosages for each distinct area. It also helps establish a range of possible reagent dosages, even for areas not tested.
Because of its effectiveness, Blastox has been used successfully on thousands of tons of heavy metal contaminated soil mixing method projects. Its chemistry has a proven long-term stability benefit. You can apply it at low dose rates and have peace of mind knowing that the soil remediation waste will remain stable, always. Its smaller particle size provides more reactive surface which is beneficial when stabilizing heavy metals for contaminated soil remediation projects. Due to the low dose rate and competitive pricing, Blastox® 215 is becoming an effective resource for many engineers and also project managers.
Download our product technical data sheet for more information. Also the video above gives a summary of a past soil remediation project were Blastox 215 treated a large area of lead contamination. This saved the contractor over $1.4 Million in disposal costs, saving the project and allowing them to continue working.
Download Full Technical Data Sheet
