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. JOHN F. ABEL, JR. 310 LOOKOUT VIEW COURT <br />MINING ENGINEER GOLDEN, CO 80401 <br />303-279-4901 <br />FAX 278-8163 <br />JFAbe12l~Comcast. net <br />Mark Levin <br />Mining & Environmental Services LLC <br />P.O. Box 1511 <br />Idaho Springs, CO 80452 <br />February 29,2008 <br />Reference: "As Built' bulkhead review <br />Dear Mark: <br />The "As Built" Pierce Adit and Steve Adit reinforced <br />concrete bulkheads constructed by MES at the Schwartzwalder Mine <br />are strong enough to support all potential anticipated loads, <br />including the maximum static water head of 120 feet and the <br />predicted peak 0.239 g earthquake acceleration of the impounded <br />line-of-sight water. The initial bulkhead design calculations <br />had to be rerun after the adit profiles for the bulkhead sites <br />were scaled, cleaned and measured. The calculations for the "As <br />Built" bulkhead dimensions were checked and verified. The <br />low-pressure grouting of the rock/concrete contact and the <br />formation grouting that was being performed during our inspection <br />on January 24th was designed to further seal the bulkhead and <br />provide additional protection against leakage along and around <br />the bulkheads. - <br />The "As Built" strength of the bulkheads exceeds all <br />American Concrete Institute requirements for structural concrete. <br />In addition, the compressive strength of every sample of the "As <br />Built" concrete, collected during filling of the forms and <br />measured by CTL Thompson, Inc. exceeded the specified 28-day <br />3,000 psi design concrete compressive strength in the initial <br />design calculations. <br />~~p.REQ~s~ <br />~ ~ 5642 ~v <br />-~.c.~ •' <br />`SS~~NA~ <br />Sincerely, <br />~• , <br />C~L~ <br />John F. Abel, Jr. <br />Colorado P.E. 5642 <br /> <br />