Investigation reveals contamination plume at Kandiyohi Co. landfill is not what was expected
WILLMAR -- The investigation of a plume of groundwater contamination coming from the Kandiyohi County landfill is providing some surprising information that will help identify the scope of the problem and potential cleanup options. The county has been tracking the plume -- which originated from barrels of toxic paint and solvents buried at the landfill in the 1970s -- for years by using monitoring wells.
But it was never known how far the plume extended, the level of contamination and if the toxic waste buried at the landfill was still fueling the plume.
Responding to a directive from the Minnesota Pollution Control Agency, the county budgeted $1 million to conduct the time-consuming and expensive investigative process of testing and analyzing the depth and breadth of the plume, which includes tetrachloroethene and vinyl chloride.
A portion of the data was collected late last fall when holes were drilled through layers of garbage buried decades ago at the landfill, and by boring deep into the aquifer on private and public lands outside the perimeter of the landfill.
Water samples were taken at five-foot intervals to a depth of 120 feet in a complicated process that has cost the county $450,000 so far, said Jeff Bredberg, Kandiyohi County Environmental Services Director
Additional borings will take place this summer, which is expected to cost another $400,000.
"It's expensive, but something needs to be done," said Gary Gilbert, environmental engineer with ECAD Engineering. Gilbert gave the County Board of Commissioners an update on the investigation at the regular meeting Tuesday.
The results, so far, are a combination of good news and bad news.
Although contamination is high in the actual garbage, Gilbert said the contamination is low in groundwater borings that were drilled through the landfill.
That part of the old landfill, which does not have a vinyl liner that new landfills have, was capped in 1989-91.
The plume likely started moving through the aquifer before the landfill was capped.
Gilbert said the capping of that 22-acre section of the landfill has kept out oxygen and has kept groundwater contamination levels surprisingly low as contaminants are naturally degraded.
"It's not what I expected," said Bredberg, who anticipated the highest groundwater contamination would be found at the source, which could have meant excavating the landfill to remove toxic hot spots.
Bredberg said that's "fairly good news" because it appears mitigation won't be needed at the source and it also means the landfill won't continue to generate contaminants to feed the plume.
"It sounds more encouraging than it did a year ago," said Commissioner Dennis Peterson.
But on the flip side, the plume appears to have spread deep and wide into the aquifer off the landfill site with levels of contamination higher than at the source.
The plume is "significantly larger than was previously known," Gilbert said.
Additional borings this year will determine exactly how far the plume has spread to private and public lands.
Once that is mapped out, the MPCA will likely recommend corrective action by the county to clean up the plume.
There are options for doing that, but Gilbert said the first step is to finish the investigative process to find out exactly how far the plume has gone and how severe the contamination is.
"By fall we'll have this plume mapped out," Gilbert said.
In other action the board:
* Approved resolutions to use eminent domain to obtain land from a property owner for an improvement project on County Road 26, as well as land from another property owner for an improvement project on County Road 8. Offers to purchase the land were rejected by the property owners and a settlement wasn't reached, which necessitated the use of eminent domain, said County Attorney Jenna Fischer.
* Approved a conditional use permit for Kandiyohi Power Cooperative to construct a distribution substation in Roseville Township.
* Opened bids for the sale of a 40-acre tract of county-owned land in Irving Township. No action was taken.
* Approved a petition requesting the partial abandonment of Branch 4 of County Ditch 23A. A public hearing was set for April 5.