REV96528

• Permit No: C1981023
• IBM Index Class Name: Revision
• Doc Name: REQUEST FOR PHASE II BOND RELEASE AT KAISER VENTURES INC CHIMNEY ROCK MINE
• Type & Sequence: SL3
• Media Type: D
• Archive: No

CHI~i INEY ROCK 1996 PHASE II BOND RELEASE
1. INTRODUCTION
This demonstration compares the quality of runoff from reclaimed areas of the Chimney
Rock Mine (Kaiser Ventures, Inc., Permit Number C-81-023) to the quality of runoff from
the same areas in their pre-mined state. Water quality is evaluated in terms of Peak
' Sediment Concentration (Total Suspended Solids, TSS) in mg/l.
' The areas evaluated are pomayed on the 1996 Phase II Bond Release map, 5 September
1996. It includes the Revision 1 Area, and supersedes the other areas [Barren Ridge, AVF
(Alluvial Valley Floor), East Pit, North Flat, and East Slope] demonstrations submitted in
' the Response to Adequacy Review Phase II Release Analysis of Pre-Mining and Post-Mining
Erosion at the Chimney Rock Mine Archuleta County, Colorado, July 1994 (which superseded
the Phase II Release Analysis of Pre-Mining and Posl-Mining Erosion at the Chimney Rock
' Mitre Arcltttleta County Colorado, September 1992 and the Request for Partial Phase II Bond
Release at Kaiser Vet:ntres, Inc. Cftimttey Rock hfirte Permit No. C-81-023, September 1993).
t Vegetation and other types of ground cover have a significant int]uence on the quality of
storm water runoff. In this demonstration, vegetation and ground cover measured in the
' 1996 Vegetation Survey of the Alluvial Valley Floor (AVF) Retierence Area is considered
as representative of the vegetation and ground cover of the AVF prior to being disturbed
by mining activity. Two descriptions of pre-mining vegetation and ground cover of the
' Facilities, East Pit, East Slope, and North Flat are considered in this demonstration. One
scenario is that the vegetation and ground cover description in the 1996 Vegetation Survey
of the Rangeland Reference Area is representative of the vegetation and ground cover of
' these areas prior to mining. The second scenario is that the vegetation and ground cover
description in the Vegetation Survey of the Pinyon-Juniper Tvpe ar Chimney Rock :ti/ine Barren
Ridge and Revision 1 Areas, Archuleta County Colorado, by ~Lfariah Associates, litc., Laramie,
' Wyoming, July 1983 (Exhibit 5, Permit) for the affected area (Table 3.2, a copy attached as
Appendix A) is representative of the vegetation and ground cover of these areas prior to
mining. The Exhibit 5 description is taken as representative of the vegetation and ground
' cover of the pre-mined Barren Ridge and Revision 1 areas. Vegetation :tnd ground cover
parameters for all the areas in their reclaimed state were developed from information
presented in the 1996 Vegetation Survey.
' Due to the extremely dry year experienced in 1996, vegetative cover on both the dryland
reclaimed and reference areas was lower than previous year's sampling data. Rock content
' observed on the reference area contributed significantly to overall cover versus the rock
content observed in the reclaimed area soils. While vegetative cover was better on the
reclaimed areas than on the reference area, rock content make the use of reference area
' comparisons invalid. Use of pre-mining data indicates that post mining runoff would be less
than the pre-mining conditions.
' Page I of 34, 7 Oct 96