for moccasin it flowed across the san wa queen valley where michael o'shaugnessy failed a daunting challenge. >> most feat was tunnelling throughout coast ranges. which was the tunnel was 28 miles long. it was an under taking but we persevered he wanted to drill through so it would be gravity flow from beginning to end. there were 85 miles of tunnels some through grantite and 71 miles of aqueducts to carry hetch hetchy water to the crystal springs reservoir >> o'shaugnessy delivered to bring water and generate power from the tuolumne river 167 miles across california by gravity flow to the san francisco bay area. >> this o'shaugnessy dam centennial moment is >> >> (indiscernible) faces transformed san francisco street and sidewalks. local business communities are more resilient and our neighborhood centers on more vibrant ask lively. sidewalks and parking lanes can be used for outdoor seating, dining, merchandising and other community activities. we're counting on operators of shared spaces to ensure their sites are accessible for all and safe. hello, san francisco. i love it when i can cros