Format: 

Author, A. A. (Year). Title of report (Report No. xxx) [Description of form]. Retrieved from Agency Name website: URL

Examples: 

Foltz, S. D., Gerdes, G. L., Hanson, M. J., Krooks, D. A., Rewerts, C. C. (2009). Public reporting and a more sustainable army (Report No. ERDC/CERL TR-09-11). Retrieved from Defense Technical Information Center website: http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA...

In-text: : (Foltz, Gerdes, Hanson, Krooks, & Rewerts, 2009) for first mention; (Foltz et al., 2009) for subsequent mentions

Notes: 

[Description of form] only used for brochures, press releases, white papers. Otherwise, omitted.

Source:
APA (ER) - p. 20, no. 28