2002-03-29_REVISION - M1999034 (2)

Home Browse Search

Perimeter Embankment Along Existing Slurry Wall Approximately 4000 linear feet of slurry wall that was constructed along the perimeter of the proposed reservoir has had a compacted homogeneous fill placed against the mined gravel highwall. This embankment was not designed as a zoned structure like the interior dike was. This embankment section is only necessary for mass and stability. The slurry wall provides seepage protection. Homogeneous backfill consisting of sandy clay overburden was used for this embankment section. Geotechnical testing was done to determine the suitability of these materials prior to using them for fill. The embankment in this azea was placed in the same manner as a dam embankment is constructed. Compaction control, moisture control, lift thickness and adequate bonding between lifts were all part of performance criteria used to evaluate the placement. The material was placed using scrapers in maximum 9-inch lifts. A disc and an 815 compactor were used to mix, tie-in and compact the lifts. Testing was done on each lift and a professional engineer from our office provided construction observation services. Field reports were compiled during the times that an engineer was on-site. Outlet Works There are cun•ently no plans that we aze aware of for an outlet works in this structure. We understand that Arvada will require some facilities to divert water in and out of the facilities. This design report does not consider the location or construction of any future outlet structures. Conclusions and Recommendations The following conclusions and recommendations aze offered for this report: 1. The proposed design section for the interior dike using a zoned earth fill can be constructed with the materials that exist on site. Geotechnical testing has shown that the materials exhibit the necessary properties for dam construction. 2. A qualified engineer should be on-site during construction of the dike to maintain construction logs. 3. A qualified lab technician should be on-site during construction of the dike to provide quality assurance of the fill that is placed. Testing should be done according to the recommended schedule. 4. Any modifications to the construction plans should be reviewed and approved by the Engineer of Record. 5. Final operating criteria for the reservoirs should be based on the safety factors that were established in the existing design. If operating criteria is proposed outside of the normal range expected for reservoirs, additional evaluation is recommended and possible modifications to the design maybe necessary. 6. When all construction of embankments and the interior dike is completed the structure will be required to be tested to see if it meets the criteria for lined gravel pits as established by the State Engineer. The testing period is 90 days and will require certifcation by a professional engineer.