Laserfiche WebLink
end. In the June 3 letter the SEO stated a design for replacement of the outlet pipe must <br /> be developed. RJH performed a site visit on October 28, 2013 to observe field conditions <br /> and develop a better understanding of site conditions. Based on review of the SEO's <br /> evaluations,review of the video inspection, and site observations, it is our opinion that <br /> the existing outlet works cannot be rehabilitated and should be demolished and replaced. <br /> In addition to the severely deteriorated condition of the pipe and potential loss of <br /> embankment, the existing pipe is too small to meet evacuation criteria. <br /> 1.6 Key Design Criteria <br /> Based on RJH's understanding of Project objectives, constraints, and site conditions, RJH <br /> has identified the following key design criteria that will influence design: <br /> • Safely pass flows for normal drawdown of the reservoir. <br /> • Include a low-level outlet sized to meet SEO release requirements. <br /> • Include an outlet stilling basin structure downstream of the dam for energy dissipation. <br /> • Include an intake structure for a manually-operated slide gate and trash racks. <br /> 2. Concept Design <br /> RJH identified the primary features of the proposed outlet works replacement to include: <br /> • Excavating through the dam to remove the existing outlet conduit. <br /> • Construction a new intake structure. <br /> • Placing new outlet works conduit. <br /> • Construction a new stilling basin. <br /> • Replacing the embankment fill. y �� <br /> • Placing riprap slope protection. <br /> The proposed outlet works replacement is shown on Figures 1 and 2. <br /> 2.1 Earthwork <br /> Two samples of the embankment above the existing conduit were obtained during the <br /> October 2013 site visit. The samples were obtained from the embankment above the <br /> outlet works conduit and at a depth of about 2 to 3 feet below the ground surface. One <br /> sample was obtained from the upstream slope and one sample from the downstream <br /> slope. <br /> Gradation, Atterberg limit analyses and a standard Proctor test were performed on the <br /> samples. Based on the test data, the material is a clayey sand (33 to 47 percent fines with <br /> a plasticity index between 15 and 18). A standard Proctor test(ASTM D 698, Method A) <br /> was performed on a combined sample of existing embankment. The material density was <br /> 107.3 pounds per cubic foot(pcf) and optimum moisture content was 15.1 percent. It is <br /> expected that the material excavated for the outlet works conduit replacement will be <br /> stockpiled near the site and is suitable for re-use as backfill to return the embankment to <br /> its current geometry. <br /> The embankment above the existing outlet works conduit would be excavated from the <br /> crest with maximum 1.5 horizontal to 1 vertical (1.5H:1 V) side slopes to the level of the <br />