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• Horizontal Drainage: A horizontal drainage system will be required in the portion of the embankment which is located on the down water side of the pond with an appropriate toe drain system. The horizontal drainage system according to the Bureau of Reclamation Design of Small Dams should be placed az shown in Figure 15. The blanket and toe drain should consist of a free draining granular material with not more than 3% passing the number 200 sieve and a maximum particle size of 3 inches. In addition, the drainage material should be wrapped with a fdter material such az M'trafi 140N or an equivalent fabric approved by the soils engineer. The drainage blanket should be minimum of 3 feet thick. An alternate horizontal drainage system according to Muafi Fabric Filter design guidelines, would be placed az shown in Figure 16. Using the "Design Guidelines for Subsurface Drainage Structures' by Mirafi Fabric Filters, the drainage blanket should be a minimum of 1 foot thick. The granular material may have 100% passing the 3/8" sieve, 70% passing the #8 sieve, 30% pazsing the #40 sieve and less than 10% pazsing the #200 sieve for a permeability of 2 ft/day. The estimated permeability for Pond 005 is expected to be lower. The toe drain should be placed az shown in Figure 15. The underdrain system should consist of a series of 6-inch diarne[er, slotted P.V.C. pipes surrounded by a minimum of 6 inches of free draining granular material. The granular material should extend up to the bottom of the next bench and should contain less than 3% passing the number 200 sieve and more than 50% retained on the number 4 sieve. The granular drainage materials should be wrapped wish a filter cloth such az Mirafi 140N or an equivalent fabric approved by the soils engineer. The drainage system along the pervious dam should extend across the natural channel to an approximate elevation of 6872 feet or 45 feet perpendicular to the center line of the proposed dam, the exact location will have to be determined in the field when the exact elevation of the channel is known. An adequate layer of fill material should cover the drainage blanket in order to maintain its integrity. Bazed on the site geometry the blanket drainage system will be approximately 250 feet in length however, the actual dimensions should be determined in the field. LIMITATIONS This report has been prepared in accordance with generally accepted soil and foundation engineering practices in this area for use by the client for design purposes. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory holes advanced at the locations indicated on the plans. Ttte nature and extent o[ variations between the exploratory holes may not become evident until excavation is performed. If during construction, soil, rock and Job No. 91-562 Ground Engineering Consultants, Inc. Page 7