PERMFILE43804

• Permit No: m2004044
• IBM Index Class Name: Permit File
• Doc Date: 11/22/2004
• Doc Name: Adequacy Review Response
• From: Tetra Tech RMC
• To: DMG
• Media Type: D
• Archive: No

TETRA TECH RMC Mc Larry Oehler
Adequacy Response M-2004-044
November 22, 2004
Page 8 of 20
writing, from UDFCD, prior to consideration of the application, for the planned
100 feet setback.
A Floodplain Use Application has been submitted to Adams County for this
project. Adams County is the regulating authority on the flood permit; however
Adams County will request review and comment from Urban Drainage and Flood
Control District (UD&FCD). The Mining Plan Map Sheet 5 of 7 has denoted the
"limit of mining without further approval of the UD&FCD".
14. For reaches of the South Platte River north of the Morgan Smith Natural Area
the UDFCD requests that Aggregate Industries change the Application to
include the information that "Mining limit without further approval of UDFCD
and DMG be shown at a 300 feet setback from the riverbank." Please make the
necessary changes to the application narrative and plan maps or obtain
approval in writing, prior to consideration of the application, from UDFCD for
the planned 100 feet setback. (See UDFCD's letter of 8-6-04 referenced above)
The Mining Plan Map Sheet 5 of 7 has denoted the "limit of mining without
further approval of the UD&FCD".
Exhibit E -Reclamation Plan
1. Describe the extraction of sand and gravel in relation to establishment of the
reservoir bank slopes. Will the dry mined pits be excavated to 3h:lv slopes or
will they be excavated to steeper slopes and then backfilled to reclamation
grades? If excavation of the reservoir perimeter will be to slopes steeper than
the reclamation grade describe backfilling of the pit perimeters including the
level of compaction and the timing of backftlling in relation to the completion
of sand and gravel extraction.
The detail, Section A-A on the Mining Plan Maps (sheet 4 and 5), shows that the
mining operation will temporarily excavate vertical high walls and backfill 3:1
sideslopes for reclamation of the water storage reservoir. The Slope Stability
Analysis conservatively modeled the mining excavation assuming a vertical high-
wall.
The site will be concurrently reclaimed to create the water storage reservoirs.
Compaction for the reservoir sideslopes at this site will be 95% (or better)
standard proctor. When an area is completely mined out from grade to bedrock,
each section approximately 800 foot wide (or approximately 30 acres), will begin
sideslope construction while the next contiguous area or consecutive phase is
beginning mining. Due to the floodway, there is limited space for stockpile
placement at this site; by concurrently reclaiming, as an area is being prepared for
mining, the overburden and topsoil can be stripped and immediately placed, or
H:\3919_0l9_OI VviLRR\DMG Response\Ist Adequacy Response to DMG I 1-5-04.doc