In March 2019, a pipeline riser leak was discovered, and an unknown volume of produced water was released to the subsurface from a leaking valve. Envirotech performed an initial site inspection to identify the area to be sampled. In order to delineate the horizontal and vertical extent of impact, soil sample locations were staked along and within the spill area.
Envirotech collected soil samples using a truck mounted direct push technology unit at the locations identified during the initial site inspection. The direct push technology unit relied on the weight of the truck, combined with a percussion hammer to drive the sampling tool into the ground. The soil core was pushed up into a plastic collection tube to the desired depth. The tube was then removed from the tool string for observation and sample collection. A scientist provided oversight of all sampling activities and collected the soil samples from the collection tube in accordance with industry-standard protocol. In addition, a background sample was collected from an upgradient and presumably non-impacted area for comparison. Each soil sample was screened for organic vapors in the field using a photo-ionization detector (PID) to determine if the area was impacted by petroleum hydrocarbons in addition to produced water.
Based on the delineation activities, Envirotech recommended removal of the soil in the impacted area down to approximately 5-ft. In addition, Envirotech recommended that representative samples of any groundwater encountered during the excavation activities be collected for laboratory analysis. Based on the concentrations of the salt observed in the spill area, the shallow depth to groundwater, and proximity to the creek, the most effective remediation technology to use at this site was a “dig and haul” which is the removal of the impacted soil for disposal or beneficial re-use in accordance with applicable state and local regulations.
Continuous field testing utilized a hand-held electrical (EC) conductivity meter and on-site field laboratory was conducted to direct the depth and direction of the excavation to ensure removal of all impacted soil. When field testing indicated removal of all impacted soil, samples were collected for a certified laboratory analysis to confirm the field testing results. Confirmation soil samples were collected and verified to be below the OCC action levels.
During excavation of the area, groundwater was encountered at approximately 5-6-ft. below ground surface (BGS). The water was field tested and determined to exceed the OCC action levels for conductivity. A sump was excavated in the area and groundwater was pumped through a temporary line to a frac tank for disposal.
At the conclusion of excavation activities, the OCC approved to backfill this area and to discontinue groundwater recovery based on the laboratory analytical results. Soil that was used for the backfilling was obtained from improving and enlarging two nearby ponds.
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