2007-10-31_REVISION - M1977208

• Permit No: M1977208
• IBM Index Class Name: Revision
• Doc Date: 10/31/2007
• Doc Name: Response to 10-05-07 adequacy review letter
• From: Cemex
• To: DRMS
• Type & Sequence: TR9
• Media Type: D
• Archive: No

Ms. Erica Crosby
October 29, 2007
Page 2
CEMEX Response: CEMEX agrees to retain dissolved thallium and chloride on the analyte lint, and
will continue to monitor for five quarters. The first quarterly sample will be taken in October 2007.
After ftve quarters, the data will be assessed, and if appropriate CEMEX will consider proposing a
different analyte list and scbedrele to DANLS.
c. Continue to monitor the water level in C-Pit.
Agreed.
CEMEX Response: CEMEX agrees.
d. Reduce the sampling frequency for monitor well CEM-001.
Because of the existence of multiple parameters historically exceeding regulatory
limits in pit water, DRMS should recommend that quarterly sampling continue
fox at least five quarters from the date sampling started.
CEMEX Response: CEMEX agrees to sample CEM-001 for five additional quarters. The first
quarterly sample will be taken in October 2007. After five quarters, the data will be assessed, and if
appropriate CEMEX will considerproposing a different sampling rchedule to DBMS.
e. Monitor the waters level at compliance well CEM-005 semi-annually.
Agtee, but if sufficient water is present in CEM-005, an attempt should be made
to collect a sample.
CEMEX Response: CEMEX agreer.
Sample alluvial well CEM-004 semi-annually and analyze for selenium,
sulfate, total dissolved solids, and pH.
Fox the reasons stated above, well CEM-004 should be sampled quarterly, for at
least five quarters from the date sampling started, and thallium should be added
to the suite of analytes.
CEMEX Response: CEMEX agrees to sample CEM-004 for fzve additional quarters and will add
thallium to the list. The first quarterly sample will be taken in October 2007. After five quarters, the
data will be assessed, and if appropriate CEMEX will consider proposing a di~'erent sampling schedule to
DAMS.
ADDITIONAL DRMS COMMENTS
g. Geochemical evaluation
On page 3-4, the statement is made that "The geochemical signature of water from
monitoring well CEM-001 did not change significantly following the placement of
the fill in C-Pit. Furthermore, these samples notably lack Ca, Mg, and K, all of which
are constituents of C-Pit water."
Response: Ca, Mg, and K can be attenuated in the aquifer by geochexnical process
such as ion exchange, mineral precipitation, ox sorption. Their absence in well CEM-
001 does not indicate unequivocally that C-Pit water has not migrated to that locale,
Draft Response to 70-5-07 Adequacy Revicw_'I'R-9_RL•;V2