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A Trusted Global Environmental, Health and Safety Partner

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Memorandum

Date: March 19, 2009

To: Tim Drexler, USEPA Kevin Herron, IDEM

From: A. Elizabeth Perry, P.G.

Subject: Miscellaneous Requested Information Pines Area of Investigation

Distribution: L. Bradley, ENSR 01776-020

On February 5, 2009, a web-based conference call was conducted between USEPA and its agency partners and representatives of the Pines Area of Investigation Respondents. The purpose of the call was to discuss the groundwater flow model. During the call, requests for specific types of background information were expressed. This memo provides the requested information.

Construction of the Type III (South) Area at Yard 520

As explained during the conference call, the four clay side-walls of the Type III (South) Area were constructed in the 1980s. Filling operations then took place within these walls. The stormwater retention basin previously located at the eastern end of the South Area was also located within the clay walls. This is shown in the three documents in Attachment 1:

Figure 7 from ATEC’s Hydrogeologic Assessment (1989) showing the active fill area, which corresponds to the area where sand was excavated.

The engineering design final grading plan for Yard 520 (1991), showing the original intention to complete filling to the eastern limit of the area.

A letter to IDEM, documenting the cessation of filling activities in 2003, and the fact that the full capacity of Yard 520 was not filled.

Permeability Testing Results

Part of the Hydrogeologic Assessment performed by ATEC (1989) included permeability testing of subsurface (natural) materials. During the conference call, there was a request for the actual test results (as opposed to a summary table of the calculated permeabilities). The raw data were included as an attachment to the ATEC report, and a copy is provided here in Attachment 2.