Since 1997, Parametrix has provided engineering, environmental, and operational services at this active landfill as well as for the closed Ellisforde and Old Okanogan Landfills. We were originally contracted to update hydrogeological and engineering studies to bring the Central Landfill into compliance with the updated regulations. This work resulted in PS&E and construction of the Phase 1B development cells. Parametrix has also led and worked with Washington State Department of Ecology on air quality issues and was able to reduce air quality fines and permit the current passive LFG system. We designed and oversaw construction of a new cell. Parametrix provides quarterly environmental compliance services to assist County staff with groundwater sampling and provides LFG monitoring in accordance with Ecology’s NOC permit.

The hydrogeologic setting of the Okanogan Central Landfill poses a challenge for implementing the required statistical evaluation of groundwater data to identify potential contaminant releases. Groundwater, both upgradient and downgradient of the landfill, has naturally high concentrations of landfill indicator parameters; therefore, groundwater quality at each of the downgradient wells must be compared with their unique history. Parametrix has developed innovative methods to address statistical evaluations to consider the seasonal variability and unique signatures of each well. This has been beneficial to avoid installation of additional wells. Because groundwater at the site occurs at significant depths of approximately 400 feet, installing additional wells would be expensive.