The supplementary materials are associated with a series of focus groups conducted with homeowners in southeastern Massachusetts on their willingness to adopt nitrogen-reducing Innovative/Alternative (I/A) septic systems. This study was conducted by a team of social scientists and an ORISE Fellow at the Environmental Protection Agency in an effort to understand the social and cognitive dynamics of I/A system adoption, which until recently remained understudied. These supplementary materials include: 1) Facilitator Guide for Focus Groups: this contains the script used to conduct homeowner focus groups, including consent information, focus group instructions, and questionnaires used during the focus groups. 2) Instructions sent to FG Participants: these are focus group instructions sent to participants prior to the focus group, to familiarize participants with the focus group process and content. 3) Questions & Q-sort Statements: this contains our data collection instruments for this study, including the Q-sort cards used for the Q-sort, individual interview questions, and semi-structured group discussion questions. 4) Recruitment Letter to Homeowners: this is the letter used to recruit participants for the focus group. 5) Recruitment Screener: this is the phone call template used by the focus group contractors to evaluate potential participants' eligibility to participate in the focus groups.