In early summer season, the reservoir behind Dworshak is about 630 feet deep. At the bottom of the reservoir the water pressure is high. From the top to the bottom of the dam are large, solid, copper “waterstops” between the large concrete monoliths designed to prevent leaks between the monoliths and in the cracks. Since 2009, the District and a contracted architectural-engineering (A-E) firm have been studying and prototyping new urethane waterstop technologies for tall or “high-head” dams. This $1.3 million American Recovery and Reinvestment Act (ARRA) technology demonstration will lead to groundbreaking engineering research data for future high-head waterstop repairs at Dworshak and around the world. The urethane waterstop cylinders are being manufactured off site, and installation is expected to begin in late September 2010.