COPA - PCBs and Superfund in Bloomington, Indiana

VIACOM
July, 2002

Modifications of Monitoring Wells NN-300A, 00-587A, 00-125A and NN-12A

In order to perform further investigation work planned under the Lemon Lane Conduit Study, we need to modify the four subject wells. Attached is a scope of work describing the modifications we want to make.

We have a drill rig scheduled for the week of June 10, to do the well abandonment work at Winston Thomas and Lemon Lane. We would like to schedule this work right after that to avoid remobilization of the rig. We have already determined that the drill rig will be necessary to clear obstructions in MW-300A. It may also be needed is obstructions are found in the other wells.

This work could begin late in the week of June 10. Therefore, your written consent to proceed with these modifications is requested as soon as possible.

Scope of Work for Modifying Valhalla 'A' Wells

Goals:

To modify Valhalla shallow A wells so they do not reflect phreatic water levels by sealing the bottoms of the wells up to the 817' elevation.

Procedure

The wells to be modified are:

NN-300A
00-587A
00-1 25A
NN-12A

The location of each well is shown on the attached figure.

NN-300A is a 4" open borehole, the rest of the wells are 6" open boreholes. The attached figures show the current depths and elevations of each well. All the wells have 2" PVC casing with 5' or more of screen at bottom inserted without grout or sealant in the hole to prevent collapse from closing the holes. The 6" wells are cased through the soil with 8" steel casing and have 12" steel protective covers over them. There is an 11" steel center plate centering the 2" PVC in the hole.

For the 6" wells

Remove the center plate.
Probe the annulus to check for obstructions.
If the annulus is free of obstructions, pull the 2" PVC up to the desired height (see attached figures).
Pour 4/~" bentonite pellets down the annulus until the desired height. Cut the 2" PVC to fit under the pro-cover.
If the annulus is obstructed then pull the 2" PVC and remove obstruction using a rig-mounted 3' split spoon with rock catcher.
Place bentonite pellets to desired depth and replace 2" PVC.
For NN-300A, set up rig over hole.
Pull 2" PVC out of hole.
Clear hole of all obstructions with 3" split spoon.
Place bentonite pellets to desired depth and replace 2" PVC.

Warning! Eat no fish from Clear Creek, Pleasant Run, Salt or Richland Creeks.
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