2005-03-23_REVISION - M1977424

• Permit No: M1977424
• IBM Index Class Name: Revision
• Doc Date: 3/23/2005
• Doc Name: Submittal
• From: Western Water & Land Inc
• To: DMG
• Type & Sequence: TR5
• Media Type: D
• Archive: No

1.0 INTRODUCTION
Western Water & Land Inc. (WWL), agent for Glenn Springs Holdings, Inc. (GSHI),
property manager for Occidental Oil Shale, Ina (OOSI) has prepared this Technical
Revision (TR) to Mine Permit M-1977-424, Logan Wash Mine, to address stormwater
control measures to be implemented at the mine as part of final reclamation.
stormwater control was requested by the Colorado Division of Minerals and Geology
(DMG) after a site inspection at Logan Wash Mine on September 1, 2004. The Logan
Wash Mine, is located approximately 12 miles northeast of De Beque, Colorado, in T. 7
S., R. 97 W., Sec. 25. A general site location map for the Logan Wash Mine is presented
in Figure 1.
W WL received the Inspection Report on October 4~' 2004. Before the site inspection,
W WL reported to the DMG that erosional features had developed at the site after a
significant precipitation event in July 2004. The erosion that occurred at the mine site
resulted in damage to previously installed revegetation terraces and transport of some
waste rock from the main lower mine dump. There was no transport of waste rock off the
permit area. In an effort to prevent future erosion to revegetated areas and migration of
mine waste materials from significant storm events, GSHI proposed to construct several
stormwater control features on the mine site. DMG concurred and requested in the
Inspection Report that drainage control calculations be provided in a TR.
The goal of stormwater control at Logan Wash Mine is to minimize hydraulic damage
resulting from significant storm events by providing suitable stormwater conveyance
structures at the mine to transport water to natural drainages. The storage of water in
detention basins is not included in the stormwater control plan. This TR describes the
method used to estimate peak discharge at the mine site for a selected rainfall intensity
event and presents the associated peak discharge calculations and design specifications
for stormwater conveyance structures of appropriate design capacity. The primary
stormwater control features to be constructed at the site are open drainage channels of
varying geometry. Secondary drainage features not described in this TR include water
bazs, berms, and, if necessary small toe drains. These features will be constructed on the
Upper and Lower mine benches and access roads and the Research Mine bench (Plates 1
and 2). Construction of the stormwater drainage features will not result in significant
modifications to the site grading plan.
2.0 PEAK DISCHARGE CALCULATION
The rational method was selected to calculate peak dischazge for the Logan Wash Mine
area because it is considered appropriate for small watersheds or subbasins less than 200
acres in size in which no significant flood storage occurs (SWMM, 1996). With the
exception of a runoff stock basin in the drainage above the Research Mine, no detention
storage facilities exist at the mine.
The rational method is based on the equation:
Westem Water 8 Land Inc.