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Ms. Deb Gonima <br />June 12, 2006 <br />Page 9 of 12 <br />experience) will be on <br />when adequate key rr <br />wall excavation along <br />will be prepared/collel <br />6. Reference June 5 <br />during excavation of the slurry wall to determine <br />ials have been penetrated. Daily logs of the slurry <br />i representative samples of the bedrock key material <br />for review by the project engineer. <br />memorandum from Applegate Group, Inc. Tab 6 <br />7. The sheetpile walls have been removed from the proposed design. See <br />Terracon letter dated June 2, 2006 which is an addendum to the Supplemental <br />Geotechnical Engineering Report dated November 9, 2005. The letter includes <br />a revised exhibit showing the revised approximate slurry wall alignment. Tab 10 <br />8. The rip rap protection for the lake embankment 1St. Vrain river side) was <br />designed for the 100-year storm event, See Terracon Report dated June 2, <br />2006 that addresses global stability and impact assessment for existing <br />manmade structures. (Enclosed <br />9. The velocity and volume of 100-year flow within the lake area is approximately <br />1 feet per second (fps) and 730 cubic feet per second (cfs), respectively. The <br />100-year flood elevation varies along the reach of the St. Vrain River. We have <br />included a copy of they Conditional Letter of Map Revision ICLOMR) that has <br />been reviewed by Weld County and is currently under consideration by the <br />Federal Emergency Management Agency (FEMAi. The CLOMR includes the <br />base flood elevations along the adjacent St. Vrain River, as well as within the <br />lake area. Please refer to the Applegate Memo dated June 5, 2006 and <br />Terracon Stability Assessment dated June 2, 2006 for groundwater and <br />stability related respo i ses as provided, <br />10.The "bankfufl" condition (i,e. the maximum flow within the St. Vrain River, prior <br />to overtopping into the adjacent lakes) occurs near the 50-year storm event as <br />slight overtopping occurs during the 50-year event. The 10-year and 50-year <br />river flows are 5,950Icfs and 12,890 cfs, respectively. Since the overtopping <br />occurs and a condition slightly less than a 50-year event, it can be estimated <br />that the "bankfull" rate is approximately 10,000 cfs. Please refer to the <br />Applegate Memo dated June 5, 2006 and Terracon Stability Assessment dated <br />June 2, 2006 for groundwater and stability related responses as provided. <br />G:\3 81 113 81 1-DMG Permit\DMG Atlequacy Rvw Response\3811 Response Letter DMG.doc <br />