Laserfiche WebLink
,. <br />i~~ <br />~ JI <br />We believe the most positive, long term solution would be to add drainage and a <br />buttress as shown on Fig. 16, where the relative FS increase to over 1.5 provides <br />the desired stability increase. <br />Conclusions <br />We believe the addition of new fill has decreased the relative stability of the <br />embankment, has IikE~ly lead to movement of the pipe and has caused the ground water <br />level in the embankment to rise relative to conditions prior to placement of the fiH. It is <br />our opinion the existing embankment is marginally stable. A sudden failure is less likely <br />than gradual movemeent. However, gradual movement is likely to lead to fracture of the <br />pipeline which could trigger massive, rapid failure. This possibility has serious safety <br />implications over and above the obvious problem caused by lack of flow in the pipeline. <br />Potential flooding anl~ environmental damage could impact the San Miguel River. We <br />recommend remedial measures be implemented to increase the relative stability of the <br />slope and decrease the risk of damage to the pipe: Specifically, these include: <br />Limit truck traffic across the embankment until a more complete engineering <br />analysis of the interaction between the fill, pipe and traffic is completed. <br />Construction of a buttress fill at the toe of the embankment. Conceptually, we <br />estimate a buttress fill, about 15 feet wide and 35 feet high would be required. The <br />fill should be constructed of gravel and boulders and would need a blanket of sand <br />and gravel (designed to filter criteria) aboc ~ feet thick on the bottom and <br />upstream sides. Some portion of the exisi::.g failed embankment would be <br />removed. We recommend this repair be implemented as soon as practicable, <br />preferably prior to spring runoff. <br />Provision of drainage improvements. Conceptually, we estimate horizontal drains <br />spaced 30 to 50 feet apart across the embankment will be required. <br />The embankment area should be surveyed to provide an accurate topographic <br />plan to allow pneparation of defined design of the improvements. <br />Check the density of materials in the top six feet of both embankments to evaluate <br />the risk of additional settlement of the embankment caused by repeated traffic <br />loads. <br />PUBLIC SERVICE COMPANY OF COLORADO <br />AMES HYDRO PENSTOCK <br />C7LIT 37,848 <br />7 <br />