2019-10-01_REVISION - M1986015

• Permit No: M1986015
• IBM Index Class Name: REVISION
• Doc Date: 10/1/2019
• Doc Name: Adequacy Review Response
• From: RPM, Inc.
• To: DRMS
• Email Name: JPL
• Media Type: D
• Archive: No

RPM,Inc.
Patrick Lennberg
August 16.2019
Page 3
levels in all of the Phase I monitoring wells.except for the MW-8.MW-I I and MW-12
wells,were impacted by the gravel pit Honing and de-watering activities.The wells located
at a distance from the Arkansas River or other surface water features(MW-6.MW-7.MW-
7obs. MW-9 and MW-10) dropped as dew•atering increased. The water levels in MW-8.
MW-I I and MW-12 dropped to a lesser extent because water levels in those wells were
stabilized by the Arkansas River or nearby settling ponds.
All of the Phase 1 area wells show a rise in water level at the end of 2018 and into 2019.
This rise in seater level results from the de-watering pumps being turned off and the refilling
of the Phase 1 gravel pit in September 2018.
Phase 2 Area
Wells MW-1.MW-2.MW-3,MW-5 and MW-199 are located inside of the slurry wall and
do not represent regional aquifer conditions.Instead,they represent the pumping impacts
occurring inside of the slurry wall resulting from dewatering activities for mining and liner
testing purposes. Data from these wells are not meaningful for the purposes of
understanding grotmd water conditions in the aquifer.
As indicated in Figure 3,water levels in most of the monitoring wells located outside of
the slurry Beall in the Phase 2 area show relatively little reduction in water level during the
wining period from 2009 to 2012 because the influences of the dewatering activities are
constrained to the alluviums within the slurry wall.The water level in MW-4.MW-4R and
MW-6 show a decrease in treater level north of the Phase 2 pit.The decreases in neater level
at these locations occurred as a result of influences from the Phase 1 pit dew-atering
activities and may also be influenced by the limited recharge available fiom the river to
this location as a result of the Phase 2 slurry wall.Note that the water level fully recovered
in Iv1W-4R in 2018 when the Phase 1 dew•atering pumps were turned off
Phase 7 Area
As shown in Figure 4,the Phase 7 monitoring wells do not show any changes in water level
until the end of 2012 when de-watering of the pit area began. At the end of 2012. water
levels declined as a result of the dewatering of the pit. Water levels remained lowered
through the end of 2015 when milling stopped. and portions of the Phase 7 pit were
backfilled. Dewatering activities are still occurring at Phase 7 but from a smaller footprint.
The rise in water levels occurring at the end of 2015 resulted from the reduction in footprint
of the dew atered area at the Phase 7 pit.
Current Status and Need for Ongoing Monitoring
The greatest water level impacts at the Pueblo East Pit have already occurred and Transit
Mix has successfully mitigated any impacts that have occurred to nearby wells and well
owners. Water level condition in the fixture are expected to be less than what occurred in
the past and mitigation measures have already occurred for neighboring well owners.
including well replacements.pump replacements and hauling of temporary water supplies
to cisterns.Additional mitigation efforts are not expected to be needed in the fixture.
RPM,Inc.,25049 E.Alder Dr.,Aurora,CO 80016 Phone:[phone] Email:h1humphries2(keomeast.net