NCD980602163_19970303_Warren County PCB Landfill_SERB C_Status of Landfill Work Activities 20 - 28 Feb 1997-OCR

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PCB Landfill Working Group/ Techr1it11,·C~ttee
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Pat Barnes, Science Advisor .---/~>\? k ~:.:-C::.-c.,..,...~----·
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DATE: March 3, 1997
SUB.JECT: Status of Landfill Work Activities 2/20 through 2/28/97
Monitorin2 Well Drillina:
Groundwater monitoring wells continued to be installed at a steady pace. The focus shifted
from the off-site or background wells to the well l.ocated in the gorge ( draw) features. The
drilling activities demonstrated how irregular the depth to bedrock is at the landfill site. The
following is a summary of the approximate depth to rock below landsurface for the landfill
locations drilled this past week . Approximate water levels during drilling is also given
Monitoring Well~ Depth to Rock AP-~roximate water level
MW-6 59' 25'
NW-8 16' below bedrock
MW-9 19 1/2' IO'
MW-10 76' 2 1/2'
MW-7 46' 25'
MW-3A 65' 20'
MW-4A 40 1/2' 17'
This varied depth to rock underscores the importance of implementing a comprehensive
drilling program prior to landfill facility siting. Drilling will continue next week on the
monitoring wells closest to the landfill.
Because it is not always easy to predict groundwater flow, it is important that the
monitoring network be as comprehensive as possible. Therefore, upon further review of the
site topography, I strongly recommend the installation of two additional monitoring wells
directly adjacent to the landfill. The wells will be located near the northwest and comers
of the landfill. I have discussed this extensively with Mike Kelly and he has agreed to it.
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Liner Inspection
S&.ME and their subcontractors removed portions of the l 0-mil PVC liner for integrity testing
on Friday. The procedure used generally included cleaning the surface of the 10-mil liner,
cutting it with a utility knife, removing the liner material to be tested and replacing it with a
20-mil patch. The patch was install.ed by solvent welding. (Note this is of particular interest
because air monitors used during the liner operations are l.ikely to detect vapors from the
solvent compound.)
After the liner was cleared, cut and removed, it became very apparent that it contained several
breaches. I saw several holes in the liner. Most were very small pin holes. However, the liner
also contained a failed seam. The seam failure was evident by extensive root growth through
it and beneath it. The liner removed from the north excavation appeared to be in worse
condition. However, both had obvious signs of significant failure . In fact, portions of the
seam exposed on the south excavation appeared to contain no adhesive.
The observations made are consistent with nonnal means of liner failure and support the
hydrologic data analyzed previously, which indicate that water is entering the landfill facility.
The contractors completed their patching work by solvent welding the liner material to the
PVC well casing. A geotextile material will be placed over the liner prior to backfilling of the
excavation.
Backfill of the excavation is scheduled to occur Monday, March 3, 1997.
I recommend that the integrity of the liner be a topic of discussion at the next Working Group
meeting.
Analytical SamJ>ling
The sampling event has been rescheduled to occur during the week of March 10, 1997. Craig
Brown with the EPA, has postponed their planned March 17th event and instead will plan on
performing a separate sampling event only if the results of the March I 0th event warrant it.
The EPA will still he present for the State's sampling event and plans on splitting 20% of the
samples.
As discussed in the last Technical Committee phone conference, I have informed Mike that we
would like to include analysis of pesticides and herbicides in the monitoring wells and landfill
soil samples.
Mike and I will meet this week to determine the location of additional sediment samples.