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_ 2390 S. Lipan St. <br /> K&A Denver,CO 80223 <br /> (303)742-9700 <br /> Kumar & Associates, Inc. Fax 742-9666 <br />- Geotechnical&Environmental Engineers Branch Office-Colorado Springs,CO <br /> December 8, 1995 <br /> Subject : Backfill of Outlet Pipe, Dam <br /> 4, Eagle Park Reservoir, <br /> Climax, Colorado. <br /> Project No. 95-435 <br /> Mr. Douglas C. Seely, P.E. , <br /> W.W.Wheeler Associates, Inc . <br /> 3700 South Inca Street <br /> Englewood, Colorado 80110 <br /> Dea.— Mr. See! ': <br /> The outlet pipe for Dam 4 has been constructed in a trench <br /> which has vertical sides. The contractor wishes to place "flow <br /> fill" for the backfill above the upper cradle, rather than the <br /> compacted embankment fill . Flow fill consists of a mixture of sand <br /> and typically a low amount of portland cement . It is commonly used <br /> for backfilling utility trenches when it is more economical than <br /> placing soil backfill, due to confined conditions requiring labor <br /> intensive hand operated compaction equipment . <br /> Most commonly, flow fill contains 100 lbs or less cement per <br /> cubic yard. This is so the material can be reexcavated if <br /> required. However, this material probably is somewhat permeable. <br /> We believe flow fill may be used it if is modified to reduce its <br /> permeability. We recommend increasing the cement content to 3 <br /> sacks (282 lbs) per cubic yard to decrease permeability. <br /> The anti-seepage collars around the pipe will be embedded in <br /> the flow fill zone . There are irregularities in the sides of the <br /> trench such that a smooth plane will not occur between the flow <br /> fill and the embankment zone . We do not believe the seepage and <br /> scii piping prevention provictea by the anti seepage collars will be <br /> compromised by use of the flow fill . A benefit to placing the flow <br /> fill will be a better contact between the existing embankment and <br /> the trench backfill, in tight areas where compaction of soil fill <br /> would be difficult to attain. <br /> If there are any questions, please call . <br /> Sincerely, <br /> Kumar & Associates Inc . <br /> By CiL.w- �iC' <br /> MJP/ram Ma Pardi, P.E. <br />- <br />