Treatment of polluted soil(As)⑩

Resolving customer’s uneasiness regarding the insolubilization processing required to deal with contamination level

Emergence of a problem

There was a plan to bulldoze and sell a plot of land after dismantling a factory. However, as a result of pollution investigation, the detected arsenic level was found to exceed the standard level.

The landowner and the buyer reviewed possible courses of action, and contacted us because insolubilization was considered as a possible countermeasure.

Diagnosis

Our client (the landowner) and the buyer reviewed possible countermeasures and contacted us because insolubilization was considered as a possible countermeasure. First, we had a meeting with both our client and the buyer to hear their respective requirements.

Desires of the landowner

・Completion in a short period of time
・Pollution countermeasures hopefully part of the factory demolition work
・Reduction of countermeasure expenses by simply using the heavy machinery being employed for the demolition work
・On-site measures are preferable because the traffic of many trucks carrying the materials is undesirable in this residential area.

Desires of the buyer

・To know whether the complete removal of heavy metals was necessary (※ this was the only pending issue)
・To confirm that our technique was reliable

Validation

Since the construction site was surrounded by a residential area, it was necessary to complete the construction work (including demolition) in as short a period as possible. As we felt it was necessary that the owner and the buyer of the land fully understand the processing method, we gave a presentation about our insolubilization technology before the validation.

First, we carefully explained the risk of heavy metals.
We explained that dissolved heavy metals are toxic, mobile, and easily absorbed by the human body, increasing the possibility of health damage. Thus, the most important target material is soluble heavy metals.

We therefore had a common understanding that heavy metals do not dissolve easily and do not continue to dissolve, and that excessive construction measures are not necessary if the well-founded standard is met.

We were able to address the points of concern of the buyer by helping the buyer understand the safety and validity of the technique by showing the documentation and data we had prepared beforehand.

Planning

After reaching an understanding with both parties, we decided to adopt the total insolubilization on-site construction method.
We quickly drew up a plan for the countermeasures so that insolubilization could start immediately after the demolition work was completed.

At the same time, we tested samples gathered from the site, selected appropriate materials, and determined the adequate additive amount.
After the material was determined, we held a meeting regarding the construction work with the company performing the demolition, and the test construction phase was then started.

Once the test construction was started, both the client and our team measured in parallel the eluted arsenic from the soil after insolubilization processing, and we both confirmed that the standards were met.

Solution to the problem

Before the main construction was started, AMEC submitted a single proposal to the client.
The on-site pollution investigation was conducted in great detail, and measurement accuracy was quite good in comparatively high and low arsenic concentration areas.

Therefore, we proposed that it would be possible to make use of one of the merits of insolubilization, namely, that the consumption of the material can be varied depending on the contamination level.
Because it was possible to use an amount of material that was less than the prescribed additive amount where the contamination level was low, we prepared a map of the necessary amount of the insolubilization material according to the contamination level. By doing this, we were able to further reduce the cost of the countermeasures and devise a more appropriate and rational process. We were thus able to complete the project without any incident.

Comments from the person in charge

When a land sales contract for a privately funded parcel of land is signed, both seller and buyer must fully understand the environmental measures to be taken. To achieve this, it is essential to take care of dispelling any feelings of unease or concern that the customer may have.

AMEC does not simply promote the performance of our materials but also presents data to provide reassurance and confidence.
Additionally, we believe that proposing appropriate and rational measures, instead of excessive measures, can promote land sales and activate the economy.