2019-03-18_PERMIT FILE - M2018016 ‎(15)‎

• Permit No: M2018016
• IBM Index Class Name: PERMIT FILE
• Doc Date: 3/18/2019
• Doc Name: Adequacy Review Response
• From: Greg Lewicki & Assoc.
• To: DRMS
• Type & Sequence: AM1
• Email Name: PSH
• Media Type: D
• Archive: No

Greg Lewicki And Associates, PLLC
3375 W.Powers Circle Phone: [phone] Fax[phone]
Littleton,CO 80123 E-mail: infor'lewicki.biz
March 6, 2019
Peter Hayes
Colorado Division of Reclamation, Mining, and Safety
1313 Sherman St, Rm 215
Denver, CO 80203
Douglas Mountain Ranch Mine 112c Reclamation Permit Application (M-2018-016)
Flood Analysis
This document is intended to address the concerns brought forth by the Colo. Division of
Reclamation, Mining, and Safety (DRMS)during their adequacy review of the Douglas
Mountain Ranch Mine 112c application, dated January 8, 2019. This analysis was conducted
using Federal Emergency Management Agency(FEMA) floodplain maps available as of
February 2019. Structures and controls were designed based on Urban Drainage and Flood
Control District Technical Review Guidelines for Gravel Mining& Water Storage Activities and
sound engineering practices.
1. Baseline Conditions
1_1 Floodplain
The I00-YR floodplain as determined by FEMA is delineated on Maps C-1, C-2A, and C-213 of
the DRMS application. This is a Zone A mapping area with no base flood elevations. The current
approved map of the area from 2007 and preliminary mapping from 2017 both show the same
floodplain along the West Fork of Clear Creek.Neither map has base flood elevations. Usually,
base flood elevations would be compared to the proposed mining and reclamation topography to
determine the potential extent of flooding that may occur onsite. Since there is no base flood
elevation data available from the FEMA mapping, the pre-mine elevation in a given location will
be compared to the floodplain's horizontal extents in an effort to determine the likely base flood
elevation.
It should be noted that a visual review of the topography along the mining area and the
floodplain shows a misalignment. It appears that the floodplain should be roughly 100' further to
the southwest. However, this analysis will take the floodplain mapping as is.
1.1.1 Floodplain Elevations Alone Mining Area
Figure 1 shows flood elevations based on the baseline topography in the area where mining will
be entering the floodplain. These elevations were applied to the proposed final topography
(reclaimed condition)to determine the lateral extent of flooding onsite.
DMR Mine Flood Analysis 1 Greg 1e kki and Associates.PLtd'