Complex sentence: Although steps were taken at the time of the accident to notify the public in accordance with a state contingency plan, local residents were not immediately aware of the toxic danger and were accustomed to using the riverside for recreation and herb gathering.
Split into simpler sentences: Although steps were taken at the time of the accident to notify the public in accordance with a state contingency plan, local residents were not immediately aware of the toxic danger. They were accustomed to using the riverside for recreation and herb gathering.