Grabhorn Inc. is responsible for remediation at closed facility near the Tualatin River
Oregon Department of Environmental Quality officials presented an outline Aug. 23 of an extensive groundwater remediation plan for the former Lakeside Landfill along the Tualatin River.
About 15 citizens gathered in Beaverton City Hall to listen and ask questions about the department's 20-year plan to reduce or eliminate groundwater contamination seeping into the river from the landfill at 14930 S.W. Vandermost Road.
The public comment period for the plan - whose projected price tag tops $5 million - will expire on Sept. 23.
Operated by Grabhorn Inc., the 37-acre landfill took in construction and demolition debris from 1953 until its closure in 2009.
Beginning in the late 1990s, levels of various landfill-related contaminants began rising in groundwater sampled from monitoring wells located between the landfill and the Tualatin River.
Neighbors of the landfill have tangled with Grabhorn's attorneys and government agencies for years because of the operation's size, odor and issues related to oversight and cleanup responsibilities.
With the public's input, DEQ will submit its conclusions for a cleanup remedy to Grabhorn officials for the company to design and implement.
While the DEQ's risk assessment concluded the landfill's runoff and groundwater pose no 'significant human health risk' from private wells, soil covering waste, or gases, the contaminants present an 'unacceptable risk to river ecology.'
Contaminants in the groundwater that increased during the '90s include ammonia, chloride and metals such as barium, iron, manganese and zinc. Trace levels of arsenic and intermittent detections of selenium were also detected.
The report found the following conditions related to the river's ecological life:
Significant toxicity to sediment-dwelling organisms from exposure to contaminants in pore water adjacent to the landfill;
Contaminant impacts are localized and do not bioaccumulate in organisms;
A slow rate of groundwater discharge does not result in significant contaminant levels in water column.
The DEQ's feasibility study examined approaches to reduce rainwater infiltration through the landfill cover and the concentration of contaminants in sediment pore-water to levels that protect aquatic life.
The short-term remedial strategy involves keeping groundwater from entering the river while making landfill-cover improvements and allowing trees to mature. The long-range plan seeks to stop groundwater contamination by eliminating or minimizing rainfall through the landfill cover.
'The overall remedial strategy in the near term is to shut off the spigot of water flowing into the river,' said Henning Larsen, senior hydrologist with the DEQ.
The department is considering the pros and cons of enhancing the landfill's existing 'evapo-transpiration'-type cover versus an 'impermeable geosynthetic cap.'
With the former, soil acts as a rain-absorbing sponge and specific kinds of trees and shrubs transpire stored water and evaporate some of the rainfall.
The latter type, consisting of heavy plastic sheets bonded together and placed over the landfill, is more efficient in reducing contamination, but is more costly, involves more maintenance and is more 'prone to catastrophic failure,' according to the DEQ plan documents.
'It's a fairly complicated system,' Larsen explained. 'It's more costly, and trees would need to be removed.'
Other alternatives to the remediation plan presented include installing a barrier trench to treat water as it passes through, extracting contaminated water through horizontal or vertical wells, installing a 60-foot barrier into the ground to isolate groundwater from the river and planting a 30-foot-wide strip of hybrid poplar trees to treat and extract contaminated water.
Collected water would be treated on site and discharged, within acceptable limits, to the Tualatin River and/or used as irrigation/land application for natrophilic, or salt-loving, plants.
'It can be difficult to treat some of these,' Larsen said of the contaminants. 'It's unlikely we're going to reduce the contamination level compared with what we can do with a land application.'
Art Kamp, a resident of Southwest Pleasant Road, praised the cleanup plan, but expressed concerns about Grabhorn's ability to fund the cleanup responsibilities - which have been estimated at more than $5 million - and complete them in a timely manner.
Brian Wegener of Tualatin Riverkeepers, after the meeting agreed that the battle to clean up the groundwater has been a protracted one, but said he's confident the DEQ is on the right track.
'The cleanup requires the cooperation of the landfill owner, and that's been challenging for a long time,' he said.
However, he added, 'This is the kind of action we need. The DEQ is making significant efforts to clean this up. The plan is asking the right questions and making the right considerations.'