Assessing environmental major development projects requires using advanced levels of environmental secondary data (ESD). This is particularly challenging in developing countries. Hence, a systemic literature review was performed. Along with structured interviews and online questionnaire designed for professional planners and researchers were used to investigate the factors affecting secondary data collection and processing for environmental assessment systems in Egypt as an example of developing countries revealing potentials and challenges. The results pinpointed critical problems for ESD associated with poor sufficiency, availability, relevance, and accuracy of data. Thus, using these four defined criteria, an assessment framework was developed to evaluate the status of ESD for development projects. This provides guidelines for establishing an integrated data collection and management system to support the environmental assessment process. This is further applied to 'Elqattara depression national development project' to investigate the environmental impact of various desalination development scenarios. This case study project pinpointed problems for the ESD used related to both relevance and sufficiency.