<bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Background:</b> This research explores how controversial engineering decisions become the subject of widespread social media debates, using the prominent case of activism opposed to the Dakota Access pipeline (DAPL). The #NoDAPL Twitter hashtag became the primary vehicle for activism, with Twitter users shaping the debate through how they framed the controversy. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Literature review:</b> Framing refers to how information is packaged and presented. Because framing shapes the interpretation of information, it plays a crucial role in scientific controversies. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Research questions:</b> 1. Which framing strategies are present in the most influential (determined by the number of retweets and “likes”) posts using #NoDAPL on Twitter? 2. How do the framing strategies used in the most influential #NoDAPL tweets change in relation to major political events? 3. Do the framing strategies used in the most influential #NoDAPL tweets amplify the echo-chamber effect and polarization on Twitter? <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Methodology:</b> The team collected daily data on the #NoDAPL hashtag and selected tweets with #NoDAPL that had more than 1500 likes or retweets, and categorized them by the frames that they exhibited. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Results and discussion:</b> The most-used frames were conflict/strategy and morality/ethics, with no noticeable middle path frame, leading to the echo-chamber effect and online polarization. The scientific/technical uncertainty frame was used only sporadically, in contrast with project proponents who tried to emphasize the pipeline's safety. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Implications:</b> Engineers seeking to understand and participate in public debates about issues central to their profession should recognize and engage the frames being used by the public to understand information. The project proponents’ defense of the pipeline fell on deaf ears, likely because they focused on safety rather than broader questions of morality. While engineers should share technical information related to a project under fire, they cannot ignore the concerns expressed by their critics.