Erie Canal and Salt Covers. The Erie Canal within the city limits is about five miles long, and in it are three locks, with a stop-gate just east of the city of protection from floods. There are about 35,000 salt covers in Syracuse, averaging about 16 feet square and from 6 to 8 inches deep. The brine is pumped from the earth and sold by the State to the manufacturers. About 3,000,000 bushels of salt are produced annually.