Establishment of the C&SF made Everglades National Park completely dependent upon another political entity for its survival.[84] One of the C&SF's projects was Levee 29, laid along the Tamiami Trail on the northern border of the park. Levee 29 featured four flood control gates that controlled all the water entering Everglades National Park; before construction, water flowed in through open drain pipes. The period from 1962 to 1965 was one of drought for the Everglades, and Levee 29 remained closed to allow the Biscayne Aquifer—the fresh water source for South Florida—to stay filled.[85] Animals began to cross Tamiami Trail for the water held in WCA 3, and many were killed by cars. Biologists estimate the population of alligators in Everglades National Park was halved; otters nearly became extinct.[80] The populations of wading birds had been reduced by 90 percent from the 1940s.[86] When park management and the U.S. Department of the Interior asked the C&SF for assistance, the C&SF offered to build a levee along the southern border of Everglades National Park to retain waters that historically flowed through the mangroves and into Florida Bay. Though the C&SF refused to send the park more water, they constructed Canal 67, bordering the east side of the park and carrying excess water from Lake Okeechobee to the Atlantic.[80]