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Groundwater Verification Monitoring at the Lancaster Landfill


Detection and verification monitoring programs were conducted at the Lancaster landfill in Lancaster, California. The detection monitoring program consisted of installation and quarterly sampling of four monitoring wells. Sample results indicated that groundwater in all four monitoring wells had been impacted by volatile organic compounds (VOC). A verification monitoring plan was prepared and implemented. Tasks of the verification monitoring program consisted of landfill drilling, monitoring well installation, soil sampling, hydraulic testing, and cone penetrometer/HydroPunch sampling.

Landfill drilling detected no leachate at the base of refuse. An additional monitoring well was installed at the downgradient edge of the site. The investigation to define the contaminant plume off-site was conducted with cone penetrometer/HydroPunch techniques.

The cone penetrometer was used to distinguish the interbedded alluvial sediments and to select sand units from which groundwater samples would be collected. HydroPunch sampling was used to determine whether VOC had migrated offsite and to characterize the lateral/vertical extent of the VOC plume(s). Groundwater sampling with the HydroPunch indicated VOCs had migrated approximately 800 ft from the site and were located in a thin (3-5-ft) sand bed.

Application of these techniques, along with data collected from six other tasks, enabled characterization of the hydrogeology and assessment of ground water impacts to the landfill. The cone penetrometer/HydroPunch sampling technique proved to be a time efficient, cost-effective method to delineate a contaminate plume at the Lancaster landfill.


AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)