PERMFILE110759

• Permit No: M2001001
• IBM Index Class Name: Permit File
• Doc Date: 5/8/2001
• Doc Name: RATIONALE FOR APPROVAL RECOMMENDATION REGULAR 112 CONSTRUCTION MATERIALS APPLICATION FOUR STATES A
• Section_Exhibit Name: EXHIBIT B #3 05/23/01
• Media Type: D
• Archive: No

Rationale for Approval Recon~ ~dati~n ~ May 8, 2001
Four States Aggregates, I.LC
The application demonstrates compliance with the performance standards of Rule 3.1,
and indicates that operations will be conducted in a manner which minimizes disturbances
to the prevailing hydrologic balance of the affected land and of the surrounding area and
to the quantity or quality of water in surface and groundwater systems both during and
after the mining operation and during reclamation, as required by Rule 3.1.6.
14. Comments relating to adverse impacts due to flooding and 'pit capture':
Please see the attached Analysis of Potential Off-Site Impacts from Pit Dewatering and
River Flooding at the Proposed Line Camp Pit, prepared by DMG staff in response to
issues raised by the objecting parties regarding flooding.
15. The pit is inappropriately located within the Dolores River floodp/ain. The
material stockpiles will impound water and create a f/ashflood hazard for the
Rohinson residence and/or divert f/ood waters towards the Akin residence.
The Act and Rules do not exclude mining activities from floodplain areas, except to the
extent that such areas are located on lands covered under C.R.S. 34-32.5-115(4)(fl.
The amended application indicates that prior to mining, approximately 30% of the pit area
is located within the 100-year floodplain. Excavation activities will redefine the 100-year
floodplain to include a!! portions of the pit and final pond areas. As noted in the DMG
staff report addressing flooding, the proposed pit and final ponds are located within a
portion of the 100-year floodplain where only low velocity flood flows are anticipated.
The amended application clarifies that the temporary material stockpiles, surrounding the
pit will provide a visual and noise barrier but will not form a continuous embankment and
will not impound water. Openings between the stockpiles will allow flood waters to enter
and exit the active pit at the approximate original ground elevations and at the
approximate rate at which the flood waters rise and recede. As the flood waters recede,
water may also exit the pit through the permanent 24" diameter drain pipe. The
application states that the final ponds are totally incised, no water will be impounded
above the original ground elevations or behind constructed embankments. The potential
for a flashflood, resulting from embankment failure and immediate release of impounded
floodwater, does not appear to exist.
The application indicates that the referenced stockpiles will be composed of salvaged soils
and processing fines. Given the low velocity of the floodwaters at the stockpile area and
the unconsolidated nature of the stockpiled material, the potential for deflection of
significant flood energy from the stockpiles does not appear to exist. Additionally, DMG
findings does not support the allegation that the proposed operation will reduce the
capacity of the floodplain. Conversely, as noted in the attached DMG report, the
proposed operation will enhance the capacity of the floodplain and reduce peak flood flow
as a result of the excavation and removal of material from the floodplain.
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