The 1,100-ft center span of the landmark Jamestown Bridge, which connected North Kingstown, R.I., to Conanicut Island, was taken down by explosive demolition on April 18. The 135-ft-high steel-truss span was demolished by Cashman Equipment Corp., Boston, under an $19.5-million contract with the Rhode Island Dept. of Transportation. Cashman used a total of 75 lb of explosives to break the bridge into 55 sections. As part of the contract, Cashman will keep the 6,000 tons of steel from the job. The bridge was retired in 1992 on the opening of the adjacent Jamestown-Verrazano Bridge.