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

Recommended Groundwater Monitoring Program for Hydrogen Release Compound (HRC®) Pilot/Full Scale Treatment

Monitoring of selected wells should be conducted to validate the HRC-based enhancement of reductive dechlorination processes. The monitoring well network would ideally include wells from the following locations:

• Inside treatment area: Provides information on geochemical conditions and contaminant trends induced by HRC.
• Downgradient of treatment area: Provides information about residence time effects. Since the contaminant has to be in contact with the electron donor for a given length of time, the actual performance may be evident at downgradient locations for sites with moderate to high groundwater velocities.
• Upgradient of treatment area: Provides a measure of contaminant mass and competing electron acceptor load entering treatment area.
• Background: Allows comparison of geochemical changes induced by addition of HRC.

An initial or "baseline" round of sampling should be performed to identify pre-HRC installation groundwater conditions. After application of the HRC, samples can be collected every other month for a six to eight month period. After the initial biodegradation and geochemical trends have been identified, the monitoring frequency can be decreased to a quarterly, semiannual, or annual program.

The monitoring protocol should call for standard low flow groundwater sampling techniques and include the measurement of the following field/chemical parameters:

• All relevant contaminants
• Field parameters: DO, ORP, pH, temperature, and ferrous iron (optional field measurement)
• Natural attenuation/inorganic parameters: dissolved iron and manganese, nitrate, sulfate, sulfide, chloride, and alkalinity
• HRC-based electron donor:total organic carbon and metabolic acids (lactic, pyruvic, acetic, propionic, and butyric)
• End-product dissolved gases: carbon dioxide, methane, ethane and ethene

A specially qualified laboratory should do the analytical testing for the metabolic acids, otherwise most laboratories can provide testing for the remaining parameters. A typical cost for the above testing program is approximately $300 per sample.