The trip to a closed landfill...

today with my environmental science seminar class was instructive, where we viewed the successful implementation of a pump-and-treat groundwater remediation program at the Colbert Landfill about 15 miles north of Spokane.  The tour was guided by KB, a former EWU geology grad who oversees the functions at several closed solid waste sites in the county, seen here making introductory comments (click to enlarge):

Students peer into a vault that contains a groundwater interception well and associated electronic controls and sampling port at the periphery of the contaminated site:

Since the landfill originated as a sand and gravel pit in 1968 it doesn't have a bottom liner, but a cap installed during closure in the mid-1990s includes a thin HDPE geomembrane that prohibits water from infiltrating into the buried wastes and generating additional leachate:

The interior of the plant is a maze of pipes and valves where contaminated groundwater from a number of interceptor wells is collected and routed to the top of the air-striping tower outside of the plant:

Volatile organic compounds (VOCs) rapidly disperse from the descending column of water in the four story air-striping tower while a blower forces air up through the base and out the top, venting the evaporated VOCs into the atmosphere:

The treated water is collected and discharged to the Little Spokane River, about a half-mile to the west.  In sum, this represents a local environmental success story.