SAN FRANCISCO (AP) – A team of experts is warning of a “very significant risk” if the main spillway of a California dam is not operational again by the next rainy season. The warning is contained in a report made by a federally created investigating team for Oroville dam. It says repair crews at the Lake Oroville dam have only a few months to make sure the spillway is in good enough shape for the next rainy season, which starts in November, or the state faces a “very significant risk.” The concrete spillway, used to lower the level of Oroville Lake, was badly damaged by erosion from runoff in February. The experts say it’s “absolutely critical” that water doesn’t flow over the dam’s emergency earthen spillway this spring, which could cause further erosion. The emergency spillway began to break apart in February when it was used for the first time in its 50-year history, prompting the evacuation of 188,000 people. Repairs are underway. The team raised a number of concerns about the spillway, including that in some areas compacted clay was used to fill depressions in the foundation of the chute for water flowing out of the dam. They said portions of the slab that appear undamaged might need to be replaced. Repairs are likely to extend over two years, mixing temporary fixes with longer-term work. Overall, the state’s plan calls for rebuilding the spillway in the same configuration as the original design, along with rebuilding the chute that carries water from the dam and retaining walls. “Extensive efforts” are underway to locate and repair voids under the chute’s concrete slab. No estimate was provided on cost.