After a year and a half of sampling (7 quarters), the BTEX concentration at MW-4 (Monitoring Well # 4) and MW-3 seem to be holding steady. The concentrations fluctuate throughout the year due to seasonal changes in the water table. Since these wells are closer to the source of contamination and do not dry out in the summer, they better represent what is happening with the BTEX concentrations. See Documents for an Microsoft Excel file with graphs depicting concentrations of BTEX over time by monitoring well and by BTEX constituent.
The PRP has replaced the pump and sparge system with a more cost effective carbon cannister system from Cameron Environmental. Submerisble electric pumps now pull water from the sumps at the end of the collection trenches to a cannister containing 2000 pounds of activated carbon. The water is then discharged on land. Oregon limits the discharge concentration to land to no greater than 10 mg/liter of Total Petroleum Hydrocarbons (TPH). Water level monitors activate and shutoff pumps.
The last sample of the discharge was taken on 3/17/05. The results for BTEX and TPH were at non detect levels.
There has been no visible seeps or sheens into the South Yamhill River according to the PRP’s consultant.
Quarterly Ground Water Sampling Results can be found in “documents” section of this PolRep in a Microsoft Word file.
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