2014-04-22_REPORT - M1990057

• Permit No: M1990057
• IBM Index Class Name: REPORT
• Doc Date: 4/22/2014
• Doc Name: Drainage report
• From: Union Milling Company, LLC
• To: DRMS
• Email Name: TC1
• Media Type: D
• Archive: No

Flatirons, Inc. — Surveying & Engineering
1.0 LOCATION AND DESCRIPTION
Back round
This Drainage Report is prepared in response to a letter dated January 22, 2014 sent by the
State of Colorado, Division of Reclamation, Mining and Safety (DRMS). The letter was
sent to Nick Michael of the Union Milling Company, LLC from DRMS regarding
Amendment No. 1 to Adequacy Review No. 4. DRMS File No, M- 1990 -057.
The April 16, 2014 revision to the Drainage Report was responses to the DRMS review of
the originally submitted Drainage Report. The issues identified by the DRMS are found in
a letter from Tim Cazier, P.E. sent to Michael Cunningham, dated March 21, 2014.
The Drainage Report follows the criteria set forth by Urban Hydrology for Small
Watersheds, TR -55 by the United States Department of Agriculture (USDA), Natural
Resources Conservation Service (MRCS), Conservation Engineering Division.
Riprap was sized following the Federal Highway Administration's Design of Roadside
Channels with Flexible Linings Hydraulic Engineering Circular Number 15, Third Edition
The purpose of the Drainage Report is to analyze the hydraulic effects of the storm water
runoff produced by the improvements to the Union Mill Facility. The methodology
described in the publication, Urban Hydrology for Small Watersheds, 2"d Edition
(Technical Release 55), June 1986 was used to calculate the 10 -year and 100 -year flows for
historic and developed conditions. The TR -55 method was used to calculate the Runoff
Curve Number (RCN) and the Time of Concentration (Tc) for each drainage basin study.
Proiect Location
The Union Mill is located 1.75 miles southwest of the City of Leadville in Sections 28 and
33, Township 9 South, Range 80 West, 6th P.M., Lake County, Colorado. The site is
located on the north side of US Highway 24 on the southern face of an east/west trending
ridge. The crest of the ridge is 500 to 800 feet north of the north side of the project.
The Uintah Placer forms the southern project boundary, and the City of Leadville waste
water treatment plant forms the eastern boundary. The western project boundary is formed
by the Zuni and Pima Placers, and the northern boundary is formed by the Zuni Placer.
There are no major lakes, streams, or water resource facilities within the property. Surface
runoff is conveyed through the site in defined natural channels.
Union Mill 3 March 5, 2014