1997-06-05_REVISION - M1981302

• Permit No: M1981302
• IBM Index Class Name: Revision
• Doc Date: 6/5/1997
• Doc Name: ANALYSIS OF THE ISSUES RAISED BY THE CITY OF BOULDER IN CORRESPONDENCE DATED 4-22-97 WESTERN MOBILE
• From: DMG
• To: FILE
• Type & Sequence: AM2
• Media Type: D
• Archive: No

Memo to File M-81-302 -4- June 5, 1997
adjacent Open Space land, with particular concern for
potential impacts on ground water, vegetation and access to
irrigation water. The City of Boulder Open Space lands
contain known populations and habitat for various rare,
threatened and endangered species which are dependent on the
ground water and irrigation systems that may be affected by
the amended reclamation plan.
. . .the City of Boulder does not believe it is appropriate to
approve the proposed amendment to the existing reclamation
plan for the Deepe Farm Pit until Western Mobile conducts a
thorough evaluation of the potential ground water and
irrigation system impacts for adjacent Open Space lands .
Specifically, this evaluation should determine what affect the
revision from 38 . 1 acres of surface water to 4 .2 acres will
have on ground water levels and irrigation flows within the
adjacent Open Space lands. The City of Boulder wishes to
ensure that the reductions in surface water which the proposed
reclamation plan amendment incorporates do not result in
adverse impacts to ground water levels and irrigation flows on
the adjacent Open Space properties, threatening the habitat
for Ute ladies' tresses orchid or the Preble' s meadow jumping
mouse .
The reclamation plan proposed in the amendment application includes
a 1 . 9 acre ground water fed pond near the center of the permit
area. There has been a ground water fed pond near this location
for several decades. The size and shape of this pond has varied
somewhat over time depending on excavation and dewatering
operations at the site . The proposed reclamation plan also
includes a 2 . 3 acre ground water fed pond at the north end of the
permit area. There is currently a pond at this location that has
been created by relatively recent mining at the site (since 1988) .
Ground water fed ponds such as the two ponds at the Deepe Farm Pit
create a slight cone of depression in the ground water table. The
effect of ground water table depression caused by the existing
ponds on the lands surrounding the permit area would be negligible,
and the ground water table elevation beneath the surrounding lands
in the presence of the two ponds would be the prevailing condition
to which any Ute ladies' tresses orchids or Preble' s mice on the
surrounding lands will have adapted.
A quantitative analysis that forms the basis of the Division' s
opinions on ground water table elevations is provided here. On
December 7, 1989, the operator of the Deepe Farm Pit provided the
Division with a report titled "HYDROGEOLOGIC IMPACT ANALYSIS OF
DEWATERING FLATIRON SAND AND GRAVEL STAGE 4 AND 6 AT DEEPE PIT"
prepared by Leonard Rice Consulting Water Engineers, Inc. The
statement is made in that report that the hydraulic conductivity of
the alluvial gravel mined at the Deepe Farm Pit ranges from 80-1200