This report illustrates the use of qualitative methods and an interpretive framework (Cultural Historical Activity Theory) to examine educational interventions. The techniques are applicable to engineering education where researchers seek to investigate questions with rich contexts and compelling examples. The specific study illustrating the use of these techniques explored the impact of adopting portfolio management systems for accreditation on the learning experiences of the students required to use them. The data and interpretive framework highlight how use of portfolio assessment to satisfy accreditors' demands creates a variety of tensions - some of which can be resolved by improved design or implementation.