uAbstract

uFigures

uIntroduction

uRegulatory Environment

uContaminants & Source Areas

uRemedial Systems

uExcavation and Treatment

uBioventing

uSoil Vapor Extraction

uDual Phase Extraction

uBiosparge

uAwards

uAbstract

uFigures

uIntroduction

uRegulatory Environment

uContaminants & Source Areas

uRemedial Systems

uExcavation and Treatment

uBioventing

uSoil Vapor Extraction

uDual Phase Extraction

uBiosparge

uAwards

uAbstract

uFigures

uIntroduction

uRegulatory Environment

uContaminants & Source Areas

uRemedial Systems

uExcavation and Treatment

uBioventing

uSoil Vapor Extraction

uDual Phase Extraction

uBiosparge

uAwards

Introduction

In 2001, an environmental assessment of soil and groundwater contamination associated with natural gas production was conducted. The gas compression and production facilities are located in the West Panhandle Field, Moore and Potter Counties, Texas, and have been in operation since the 1930s (Figure 1). Shallow and/or deep soil contamination, primarily from used lube oil and natural gas condensate was discovered at most of the gas compression facilities. Limited amounts of non-aqueous phase liquids (NAPL) were observed on shallow perched waterbearing zones at two sites and dissolved phase (BTEX) plumes with benzene concentrations exceeding drinking water standards were observed at a total of six sites. The depths to the shallow perched water-bearing zones at these sites varied from approximately 20 to 40 feet below ground surface.

Regulatory Environment

Pioneer Natural Resources USA, Inc. designed a proactive, practical, and cost effective program for the selection and implementation of active systems to remediate these sites as part of the Operator and Voluntary Cleanup Programs (OCP/VCP) administered by the Railroad Commission of Texas.

Contaminants & Source Areas

Pipeline condensate, lube oils, and coolants were released from ASTs, USTs, compressor pads, scrubbers, separators and other process equipment. Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX), and TPH are the primary contaminants of concern. Free-phase NAPL was observed at two sites.

Remedial Systems

In 2005, five biovent (BV), two soil vapor extraction (SVE), one biosparging (BS), and one dual phase extraction (DPE) systems were designed, constructed, and operated to achieve cleanup of soil and groundwater at the six sites. (Figure 2) Remediation was completed at five of the six sites within two years of startup, with completion of the final site expected in 2009.

(Figure 3)

Excavation and Treatment

Impacted shallow soils were excavated, treated on-site via soil shredding, and backfilled at sites throughout the West Panhandle Field. (Figure 4)

50,000 cubic yards of soil treated onsite below Texas Risk Reduction Program (TRRP) residential levels (benzene <0.026 mg/kg, TPH < 210 mg/kg). (Figure 5)

Bioventing

The bioventing system design included installing temporary, transferable, prefabricated venting equipment that required minimal infrastructure, low O&M requirements, and were convertible to SVE operation. (Figure 6)

Main system components included bioventing wells, transfer piping (PVC), venting equipment, flow meters and pressure gauges, and electrical control equipment.

Bioventing systems were operated at 5 sites to treat vadose zone soils. All systems achieved cleanup goals below TRRP cleanup levels (benzene <0.026 mg/kg, TPH <210 mg/kg). Remediation was completed within 18 months at all sites. (Figure 7)

Soil Vapor Extraction

The SVE system design included installing temporary, transferable, prefabricated venting equipment that required minimal infrastructure, low O&M requirements, vapor treatment, and were convertible to bioventing operation. (Figure 8)

Main system components include SVE wells, transfer piping (PVC), extraction equipment, flow meters and pressure gauges, vapor phase granular activated carbon vessels, and electrical control equipment.

SVE systems were operated at 2 sites to treat high TPH concentration vadose zone soils. Both systems were operated for approximately one month before they were converted to bioventing operation to complete the final treatment. (Figure 9)

Dual Phase Extraction

The DPE system design included installing temporary, transferable, prefabricated extraction system that required minimal infrastructure, moderate O&M requirements, vapor treatment, and groundwater disposal (deep well injection). (Figure 10)

Main system components include DPE wells, transfer piping (PVC), extraction equipment, flow meters and pressure gauges, electric catalytic oxidizer, and electrical control equipment.

A DPE system was installed at on site to remove LNAPL and treat impacted soil and groundwater. The system operated for two years removing over 175,000 gallons of water, 18,000 lbs of TPH and reducing NAPL levels to less than 0.1 feet in all monitoring wells. Cleanup was achieved in 24 months. (Figure 11)

Biosparge

The biosparge system design included installing temporary, transferable, prefabricated sparge equipment that required minimal infrastructure and low O&M requirements.

Main system components include biosparge wells, transfer piping (PVC), sparge equipment, flow meters and pressure gauges, and electrical control equipment.

One biosparge system was installed to treat dissolved phase hydrocarbons. A series of 7 wells were installed on the property boundary as a barrier to treat hydrocarbons migrating from the site. The system is currently in operation. (Figure 12)

Awards

In 2005, the remediation program was nominated by the Texas Railroad Commission for the Interstate Oil and Gas Compact Commission’s Environmental Stewardship Award and received Honorable Mention.

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