The International Information Center for Geotechnical Engineers

Soil Remediation Techniques: Examination of In Situ Chemical Oxidation

 

8. Considerations and Regulatory Aspects

The use of ISCO techniques includes safety and health issues which need to be addressed. As shared by the Interstate Technology and Regulatory Cooperation Work Group (2005), some of such issues include:

  • Oxidants must be safely handled and stored
  • Permanganate and persulfate dust is hazardous
  • The presence of ozone increases the flammability of many materials
  • The generation of ozone can involve high-voltage-equipment concerns
  • There is a potential for uncontrolled exothermic reactions
  • There is a potential for preferential migration of oxidants and/or contaminants (liquid or vapor) through underground utilities

In order to avoid health complications due to hazardous dust inhalation, those directly dealing with the oxidants (most susceptible to toxicity) need to take appropriate safety measures such as wearing respiratory, skin, and eye protection at all times and minimizing the creation of mist or dust (Interstate Technology and Regulatory Council, 2005). The potential for flammability can be reduced by controlling the rate of decomposition of the oxidant (e.g. using low concentration oxidants and controlling its application) and/or by acknowledging and controlling the chemicals with which the oxidant could react (Interstate Technology and Regulatory Council, 2005). Also, when dealing with sodium persulfate, it must be stored in cool, clean, dry places away from heat and moisture sources since excessive heat and moisture can lead to self-accelerating decomposition and further combustion in surrounding materials  (Interstate Technology and Regulatory Council, 2005).

The injection of oxidants and reagents are generally regulated through the Underground Injection Control (UIC) program of the Safe Drinking Water Act (SDWA), the Resource Conservation and Recovery Act (RCRA), the Comprehensive Emergency Response, Compensation, and Liability Act (CERCLA), and the Emergency Planning and Community Right to Know Act (EPCRA) (Huling & Pivetz, 2006). Moreover, specific regulations and permits regarding ISCO techniques vary by state. A selection of permits needs to be issued prior to ISCO techniques applications. For instance, the state of New Jersey requires New Jersey Pollution Discharge Elimination System (NJPDES) Discharge to Ground Water (DGW) permits for any actual or potential discharge of pollutants to the ground, while Missouri and Texas require the completion of its “Form UIC-Application for Class V Permit” and the “TCEQ Class V Injection Well Inventory/Authorization Form” respectively (Interstate Technology and Regulatory Council, 2005). Overall, states require an extensive description of the problem and proposed remediation technique to provide permits.

Monitoring is required not only while conducting ISCO treatments but also after: process and performance monitoring and post-treatment and closure monitoring (Interstate Technology and Regulatory Council, 2005). As its name indicates the first type of monitoring takes place during the most active phase of the remediation practice. In such period of time, it is conducted frequently to ensure that the technique is working as intended. On the other hand, post-treatment and closure monitoring takes place on a more infrequent basis after the soil reaches equilibrium in order to verify cleanup results.

In order to determine the effectiveness of active soil and groundwater ISCO technique the following criteria are proposed by ITRC:

  • Groundwater elevation contour maps
  • Graphs of contaminant concentrations over time
  • Summary of the volume of soil/groundwater treated
  • Summary of contaminant concentrations above/below applicable remediation standards

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