Texas moved closer Friday to allowing low-level radioactive waste from dozens of states to be trucked in and disposed at a site in West Texas, which would become one of only four in the nation that could take low-level radioactive waste shipped from out of state. A state agency with oversight of waste imports adopted rules Friday that help clear the way for the 1,338-acre dump near the New Mexico border, despite concerns expressed by environmentalists that such a facility may be unsafe. Its operator, Waste Control Specialists LLC, still needs final approval from the Texas Commission on Environmental Quality, but expects to receive it within several weeks, said company spokesman Chuck McDonald. The company is majority-owned by Texas billionaire Harold Clark Simmons, one of the nation's wealthiest men and a major donor to Republican state and national political candidates. Supporters of the project, located in a remote red-clay formation just east of the New Mexico-Texas state line about 31 miles from the town of Andrews, Texas, maintain it is environmentally safe and note that it will generate needed revenue for Texas. Critics contend that water near the disposal site could become contaminated by the waste, which can include radioactive material from nuclear-power plants, research facilities and hospitals. They also say that truckloads of refuse will be traveling through Texas with insufficient oversight, creating a recipe for trouble if they get into accidents. "We do not believe the site has been adequately examined to ensure it is not too close to groundwater," said Cyrus Reed, conservation director of the Sierra Club's Lone Star Chapter. "And on windy days, there is also the potential for air dispersion of radioactive materials." The Texas Commission on Environmental Quality said it couldn't specify when Waste Control could begin importing and disposing of waste at the site, which would be able to accept low-level waste from 36 states including Texas. The agency closely inspects prospective waste facilities to make sure "public health and the environment are protected," said Andrea Morrow, a spokeswoman for the agency. Three other sites currently accept low-level radioactive material: Richland, Wash., since 1965; Barnwell, S.C., since 1971; and Clive, Utah, since 1991. Several others have since closed, some of which encountered minor leak problems, including one in Beatty, Nev., that closed in 1992. The U.S. Geological Survey found slightly elevated radiation west of the Beatty site in the 1990s. The transport of radioactive materials poses an additional hazard, said Craig Adair, chief of staff for Texas Rep. Lon Burnam, a Democrat who represents Fort Worth, which rests along two major interstates that could be used to bring waste to the West Texas site. "There are serious questions about how prepared the state's emergency responders are for a potential spill," Mr. Adair said. Mr. Burnam last year voted against a bill that expanded the number of states from which Mr. Simmons's company can import radioactive waste. Texas Republican Sen. Kel Seliger, who wrote the bill, said there was a pressing need for the disposal facility. "The state has worked for years to ensure that the process and location of the site are safe and environmentally sound," he said. Critics maintain that that Mr. Simmons's financial might has helped him win state backing for the site. Mr. Simmons has donated more than $1 million to Gov. Rick Perry, who appoints board members to Texas agencies that oversee the waste site, according to Texans for Public Justice, an Austin-based organization that tracks political donations. Mr. McDonald said Mr. Simmons didn't help the company win any regulatory shortcuts. "There have been more public and legislative hearings on this issue in the past nine years than just about anything in Texas," he said. "It has been heavily scrutinized." In February, a political action committee that Mr. Simmons solely funded admitted it had erred when it donated $65,000 to 18 state lawmakers last year, and asked the politicians to give the money back. The admission came after Texans for Public Justice filed a complaint with the Texas Ethics Commission, challenging the donations as illegal under state law because such committees have to have at least 10 contributors before making contributions. If the project "will create jobs and meets all the permitting criteria required by the state, then there is no reason the project should not move forward," said a spokeswoman with Mr. Perry's office. The Texas Department of State Health Services, which oversees radioactive-waste shipments, said shippers of radioactive waste must "submit emergency plans in case of an accident or incident." Waste Control Specialists estimated that Texas would receive as much as 25% of the revenue from the disposal of imported waste, up to a total of $20 million annually. "These disposal facilities will generate new money for our state—without raising taxes—at a time when legislative budget writers face severe financial distress," company President Rod Baltzer said in February.