Exchequer Dam - Placed in service in 1926. The famous Exchequer Dam was built for the Merced Irrigation District. The largest irrigation project in America at the time. The dam was 330 feet high and 960 feet long, this huge dam was 220 feet thick at its base and 16 feet wide at the top. Its reservoir was 12 miles long and will held 289,000 acre feet of water.