Framing refers to how information is packaged and presented. Because framing shapes the interpretation of information, it plays a crucial role in scientific controversies. We analyzed the frames used by Twitter posters using the #NoDAPL hashtag during the unfolding Dakota Access Pipeline controversy. We found that the most used frames were conflict/strategy and morality/ethics, with no noticeable middle path frame, which reflected and reinforced an echo chamber of online polarization. We also identified a mismatch between engineers' emphasis on pipeline safety and the lack of posters' use of the scientific/technical uncertainty frame. Our article was awarded the 2018 Rudolph Joenk Award for Best Paper in the journal IEEE Transactions on Professional Communication.