Laserfiche WebLink
An extensive geotechnical evaluation was performed by Chen and Associates during <br />eac•ly summer of 1980. This investigation included exploratory holes along or within each <br />proposed pond embankment to investigate subsoil foundation conditions and borrow for the <br />embankments. Tests were performed to determine shear strength, bearing capacity, <br />permeability, compaction, compressability and swelling characteristics of the various <br />matec•ials. Chen and Associates submitted a report on both the initial investigation and a <br />subsequent boring program. A copy of these reports is enclosed herewith. <br />The results and recommendations cited in the Chen and Associates reports were <br />used as a basis for the design for all embankments. The soils data used in each <br />embankment design are summarized in Table 2 of this report. <br />LANDSLIDE INVESTIGATIONS <br />An extensive geotechnical investigation was conducted on potential slide areas on <br />the project site by Geo-Hydro Consultants during the summer of 1980. Their findings <br />indicate that the area for potential landslides lies above the proposed pond locations above <br />• an elevation of 6,400 feet and as such will not be affected by the construction of the <br />ponds. A copy of this report is available for review. <br />The investigation by Geo-Hydro Consultants indicates that the stability of any cuts <br />within the landslide area is directly related to the saturation state in the upper fifteen <br />(15')`feet of the soils. A dewatering system has been designed to lower the water levels <br />and, thus, stabilize the existing ground and any future construction within these areas. <br />POND DATA <br />The maximum height for the four (4) embankments is generally less than twenty- <br />five (25') feet. Geometric data, storage capacity, embankment heights, surface area, and <br />spillway information for all ponds are shown in Table lA. <br />HYDROLOGIC DESIGN OF RUNOFF PONDS <br />The three (3) storm drainage sediment control dams will be used as settling ponds <br />for site generated sediment. These ponds have been designed according to OSM criteria as <br />. printed in the March 13, 1979 Federal Register. This document requires a sediment <br />storage volume of 0.1 acre feet/acre of disturbed area and a runoff storage volume re- <br />sulting from the 10 year 24 hour rainfall event. The OSM requirements for spillway sizing <br />