Samples from within the tanks of the Exxon Valdez have been sent to an independent laboratory in Colorado for analysis, which could determine the makeup and toxicity of a milky blue substance sporadically discharging from the crippled tanker, Coast Guard officials said. Scientists gathered samples from 15 of the Exxon Valdez’s tanks, said Cmdr. Don Montoro. Analysis of the material, earlier found to contain equal parts of weathered crude oil and marine life, could take up to a week. Meanwhile, state authorities are drafting conditions to which Exxon Co. will have to agree before moving the crippled Valdez into state waters for repairs, officials said. The 987-foot tanker is now about 14 miles northeast of Pyramid Cove on San Clemente Island, where steel plates dangling from the ship’s hull will be removed, allowing the vessel to enter San Diego Bay for repairs, the Coast Guard reported.