Recommended Groundwater Monitoring Program for Oxygen Release Compound (ORC®)

Monitoring of selected wells should be conducted to validate the enhancement of natural attenuation processes. Also, an initial or "baseline" round of sampling should be performed to identify pre-remediation groundwater conditions. After delivery of ORC to the subsurface, samples can be collected every two to three months. After the initial biodegradation and geochemical trends have been identified, the monitoring frequency can be decreased to a semiannual or annual program. The monitoring program should employ low flow groundwater sampling techniques and include the measurement of the following field/chemical parameters:

• All contaminants of concern
• Field Redox parameters: ORP, pH, DO, and ferrous iron
• Biochemical Oxygen Demand (5 day) and Chemical Oxygen Demand at selected wells within treatment area

Ideally, samples should be collected from the following site locations:

• An upgradient or background location to identify groundwater conditions outside the treatment area
• Inside the treatment area
• An appropriate distance downgradient of the treatment area to identify potential residence time requirements for complete biodegradation
• Downgradient compliance point to confirm offsite migration is not occurring