GENERAL41680

• Permit No: M1999006
• IBM Index Class Name: General Documents
• Doc Date: 7/18/2002
• Doc Name: Reference GW report
• From: Hydrosphere
• To: DMG
• Media Type: D
• Archive: No

Ms. Cynthia Pazker
,July 13, 2001
Page 2
It is convenient to categorize the impacts with respect to their relationship to the phasing
of activities and operations of the proposed mine.
1. The first phase may be regarded as the "active operations period," in which the actual
mining and related activities (including dewatering and reclamation) take place. We
assume that this period may last azound 20 years for the first project phase. During
this period, the major activities which may have an impact on the water resources of
particular interest to you are:
The local alluvial aquifer dewatering activities which would be necessary to
implement the proposed "dry mining" sand and gravel resource exploitation. Because
the sand and gravel being extracted by the proposed operation is a portion of the
continuous regional South Platte River / St. Vrain River alluvial aquifer, the impacts
of aquifer dewatering and removal aze likely to extend beyond the immediate area of
operations. If not mitigated, the consequent decline in groundwater levels is likely to
be the cause of significant adverse impacts to Sage Hill Farm wells, spring and
wetlands. We address this matter in greater detail below.
The manner in which water pumped during the dewatering activities is used and
disposed of The dewatering operations are likely to result in the production of
significant amounts of water, requiring suitable disposal to avoid causing undesirable
impacts.
• The manner, location, timing, sequencing, duration and extent of the mining and
dewatering activities will affect each of the issues identified above.
2. The second phase can be considered "the long term," in which active mining,
dewatering and reclamation operations have ended. During this phase, the major
water resources related issues aze:
The potential impacts of the reclaimed gravel pits on local water resources (including
the local aquifer) due to possible changes in consumptive use of groundwater. Such
impacts are considered by the State Engineer in the review of the required Substitute
Water Supply Application, to the extent that they have an identifiable impact on
decreed water rights, registered wells within 600 feet of the gravel pit, and
appropriated stream systems . For Substitute Supply Plans, the State Engineer does
not normally consider "collateral" environmental impacts unless they aze addressed
by Water Court decrees, or other legal or regulatory protection.
Possible environmentaUecosystem impacts of open water surfaces (and other aspects
depending condition in which the mined area is left) may cause changes in the local
flora and fauna, and human use of the areas. These could result in changes in the
ecosystem in neazby azeas as well. There maybe differences of opinion about the
desirability of such impacts - some may be regazded as positive (e.g. new and
interesting vegetation and wildlife, etc), and some maybe considered to be adverse
(e.g. increased mosquito breeding habitat, safety issues, and neazby parking problems
if the gravel pit ponds aze made available for public access, etc).
Hydrosphere Resource Consultants, 1002 Walnut Suite 200, Boulder, CO 80302