EPA Well Field Rehabilitation

EPA Well Field Rehabilitation

Western Iowa

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In June 2017, Seneca Companies, Inc. mobilized teams from both their Seneca Remediation and Waste Solutions divisions to assist an engineering firm in improving groundwater production at an EPA site in Western Iowa. The EPA well field consisted of 11 extraction wells which were used to control a chlorinated solvent plume. The well field operators were experiencing numerous issues including decreased well production, excessive piping back pressures and several motor alarm faults.

One of the first project challenges was that each extraction well and associated pumping equipment was installed below grade, within confined space vaults. These vaults were only accessible through vertical hatches. Our Seneca Waste Solutions team, who is extensively trained in confined space entry and air monitoring, easily overcame this hurdle. Each submersible pump, standpipe and associated wiring was disconnected from the extraction well within the vault. Once completely disconnected, the 60’ long pump assemblies were removed from the confined spaces for further testing by Seneca Remediation technicians.

Eight of the 11 pumps were disassembled and found to be critically damaged. Further investigation revealed that damage was caused by excessive iron deposits, a clogged water distribution line, float malfunctions, sheared pump shafts and electrical motor shorting. New motors and pumps were ordered and later reinstalled by Seneca to remedy the issue.

The well field also consisted of one 850-foot-long 3-inch sch80 PVC groundwater discharge line. Over the years the discharge line had accumulated scale and iron deposits such that the pipe diameter was reduced by half in some locations. The thickest deposits were located where air and groundwater mixed near the meter manifold. This buildup reduced the performance of the groundwater pumps, as the pumps had to overcome the additional back pressure created by the deposits.

To eliminate these piping deposits, our Waste Solutions team accessed the discharge line through the confined space vaults and used jetting equipment to blast the iron deposits from the pipe walls. The pulverized deposits and associated jetting fluids were then simultaneously captured by a vacuum truck and properly hauled away for disposal. These removal strategies were an extremely successful and efficient way to thoroughly clean the line without the use of dangerous chemicals.

To finish the rehabilitation efforts and help improve flow rate metering accuracy, Seneca Remediation rebuilt the metering manifold, cleaned the existing flow meters and completed electrical troubleshooting. The system is now completely rehabilitated with all 11 pumps functioning properly, allowing for maximum capturing of the groundwater plume.