Material: Design considerations
The geosynthetic design included the following components installed on the prepared dam face, as detailed by geo-technical engineer Norm Bishop of Stone & Webster:
• a nonwoven geotextile protective under- layer (16 oz./yd²);
• a 45-mil reinforced poly-propylene geomembrane;
• a nonwoven geotextile pro-tective over-layer (16 oz./yd.²);
• a 75-mm (3-in.) tendoned, perforated Geoweb? cellular confinement system;
• a 75-mm (3-in.) poured-in-place concrete veneer facing element protecting the un-derlying geomembrane.
The geosynthetic solution was chosen for three reasons, according to John Heap, Pres-ident of Colorado Lining In-ternational. "First, it saved cost. The client saved be- tween $600,000-$700,000 over conventional reinforced-concrete methods. Second, it provided a waterproof pro-tection to the dam face, the client has a system that will conserve more water and will
function for a long, long time." The third reason, added Heap, was constructability. "Custom-made geomembrane panels were precut and welded offsite, significantly re-ducing construction time, as well as limit-ing exposure to natural degradation ele-ments and eliminating the need for special construction equipment."
The geocell slope-protection system with integral tendons and ATRA? clips was specified as the geomembrane-protection system. The tendons allowed the geocell
sections to be anchored at the crest of the slope, secured to a deadman anchor system and suspended over the geomembrane. "When anchoring with traditional stakes is not possible, as in this case, integral tendons and load-transfer clips allow the geocell system to be suspended over the geomembrane without jeopardizing its integrity," Samuel Randolph of Soil Stabilization Products Co. notes. "This method enables a system that directly protects the geomembrane from accidental puncturing and natural degradation."

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