|
Foltz, Lupo, and Barroso (2004) present a discussion of LLDPE under high loads from actual case studies
<br />whereby the geomembrane was exposed to 80% strain without failure. Based on these case histories and
<br />experience at site, the predicted 4% elongation is well within the performance range for LLDPE.
<br />References:
<br />Peggs, I.D., B. Schmucker, and P. Carey, 2005, Assessment of Maximum Allowable Strains in Polyethylene
<br />and Polypropylene Geomembranes, Geosynthetica.
<br />Touze - Foltz, N., J.F. Lupo, and M. Barroso, 2004. Geoenvironmental Applications of Geosynthetics, EuroGeo
<br />4 Keynote Paper, Scotland.
<br />44. Page 7 -15, Section 7.2.6 — This section states the SGVLF sediment ponds will be designed to store twice the
<br />runoff from the 25 -year, 24 -hour storm event. Appendices 9 and 12 state the design volume is two times the
<br />10 -year, 24 -hour storm event runoff. Please clarify and correct the statements) in error.
<br />RESPONSE. The sediment ponds are designed to hold two -times the 10 year 24 hour storm event, and the
<br />statement in the report was a typographical error.
<br />45. Page 84, Section 8.2 — The SGADR will hold, convey, contain, and/or transport designated chemicals used in
<br />the extractive metallurgical process. Pursuant to Rule 6.4.21(10)(a), the Applicant must provide design
<br />specifications certified by a licensed professional engineer for all Environmental Protection Facilities intended
<br />for that purpose. There is not an engineer's stamp and signature on the preliminary design summary presented
<br />in Appendix 10, Volume VI — Squaw Gulch Valley Leach Facility and ADR Process Description & Design
<br />Basis. Please have the responsible engineer from FL Smidth stamp and seal the last page of the design
<br />summary that precedes the series of drawings in Appendix 10, Volume VI. (Note: Colorado statutes require
<br />the certijying engineer to be licensed in Colorado).
<br />RESPONSE. As requested, CC& Vprovides within Attachment 9 stamp and sealed last pages of the design
<br />summary that precedes the series of drawings in Appendix 10, Volume VI from the responsible engineer from
<br />FL Smidth.
<br />46. Page 9 -6, P paragraph and page 12 -8, 4t` paragraph — The Division questions the selection of 100 feet for the
<br />height of highwalls to be fenced off. Falls from a height significantly less than 100 feet could be equally fatal.
<br />Please provide some discussion on the 100 -foot criteria.
<br />RESPONSE: Prior amendment applications reviewed and approved for the Cresson Project have referenced
<br />100 feet for the height of highwalls to be fenced off. Thus, CC &V is uncertain why the same language is
<br />being questioned by the Division. In addition to fencing, as discussed in the application, signs will also warn
<br />of topographic hazards as appropriate. Fencing along with appropriate signs will be adequate to meet the
<br />requirements of the post mining land use of livestock grazing and wildlife habitat for the Cresson Project. In
<br />addition, CC &V will be in control of the property post closure and individuals will be trespassing on private
<br />property owned and controlled by CC &V.
<br />47. Page 10 -1, Surface water Mana eg ment — Please respond to the following comments:
<br />a. Why was a 2.7 -inch design storm was used for the 10 -year, 24 -hour storm event for all areas except the
<br />SGVLF and Arequa Gulch Valley Leach ( AGVLF)?
<br />RESPONSE: AMEC referred to a letter addressed to Mr. Berhan Keffelew on March 4, 1997, in reference to
<br />Cresson Project; Permit M -1980 -244: Surface -Water Drainage Modification For Arequa Gulch Overburden
<br />Storage Area, to obtain the design storms for the permanent diversion channel and sediment pond. The
<br />letter's attachment, Arequa Gulch Overburden Storage Area Drainage Plan March 1997, states in the third
<br />paragraph of the methodology section "The storm -water runoff controls are designed to safely pass the flows
<br />from the 100 year, 24 hour precipitation event (3.5'), and, with respect to the runofffrom the disturbed area,
<br />to detain at least the runofffrom the 10 year, 24 -hour precipitation event (2.4').
<br />b. Why is AMEC using a 25 -year, 24 -hour storm event for detention pond design, when the design
<br />criterion is two times the 10 -year, 24 -hour storm event?
<br />RESPONSE: AMEC has designed the detention ponds to hold two times the 10 year, 24 hour storm event,
<br />and made an error by stating in the report stating in the report 25 year, 24 hour storm.
<br />
|