1999-06-23_REVISION - M1977208

• Permit No: M1977208
• IBM Index Class Name: Revision
• Doc Date: 6/23/1999
• Doc Name: Report on Storage of Cement Kiln Dust
• From: BANKS AND GESSO LLC
• To: DMG
• Type & Sequence: TR1
• Media Type: D
• Archive: No

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' 6.0 Surrounding Wells and Local Aquifers
There are two aquifers in the area that are typically used for water supply. They
' are the alluvial aquifer of St. Vrain Creek and the Dakota sandstone. Both of
these aquifers are isolated from C-Pit by 800-1000 feet of relatively impermeable
' sedimentary rocks.
Figure 4 shows a plot of wells in the area based on data from the Colorado
' Division of Water Resources (permitted wells database). The list of wells from
the Colorado Division of Water Resources is included in Appendix B. Wells are
shown by quarter -quarter section. It should be noted that many of the wells are
' piezometers and monitoring wells adjacent to Southdown's property in the sand
and gravel alluvium.
' Recent water quality data is available from wells in both the Dakota sandstone
and in the alluvial aquifer. Water quality in both aquifers is generally good with
no indication of any impact from CKD disposal.

A well completed in the Dakota sandstone (located in the extreme southeast
corner of section 28) was sampled in April, 1999 by personnel from Grant
Environmental, Inc. The laboratory results (Table 6.1) indicate that the water
quality is in compliance with almost all applicable standards. Results of water
quality analysis in A-Pit Reservoir are also shown in Table 6.1.
The pli (which would serve as a key indicator of impacts due to CKD disposal) of
Dakota Well water is 8.28, within the natural, expected range. Table 6.1 shows
the measured water quality in this well compared to the groundwater standards
suggested by the DMG.
Eight wells completed in the alluvial aquifer have been recently sampled and
analyzed for a variety of water quality parameters. These results are presented
in Appendix C and they indicate good water quality that meets the various
groundwater quality standards. There is no indication of elevated pH, which is
evidence that the water in the alluvial aquifer is not affected by CKD disposal.
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7.0 Fate and Transport of Certain Constituents of Concern in
Groundwater
' 7.1 Introduction
' The hypothetical groundwater quality impacts resulting from the disposal of CKD
in C-Pit-are:the formation and migration of leachate from the disposed CKD to
groundwater. Leachate forms as precipitation infiltration percolates through the
' backfilled CKD and dissolves soluble constituents present in the CKD. The
amount and composition of leachate is governed by three considerations: 1) the
' is